NAT'L INST. OF STAND & TECH NIST

PUBLICATIONS REFERENCE

NBSIR 75-938

The National Measurement

System for Acoustics

David S. Pallett and Marilyn A. Cadoff

Applied Acoustics Section

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

March 1977

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 75-938

THE NATIONAL MEASUREMENT

SYSTEM FOR ACOUSTICS

David S. Pallett and Marilyn A. Cadoff

Applied Acoustics Section

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

March 1977

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Betsy Ancker-Johnson. Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

CONTENTS

Page

EXECUTIVE SUMMARY 1

1 . INTRODUCTION • 3

1.1 Importance and Status of Field 3 1.2 Purpose of the Study 3 1.3 Scope of the Study 3 1.4 Limitations of the Study. 4

2. STRUCTURE OF THE MEASUREMENT SYSTEM 5

2.1 Conceptual System 5

2.1.1 Quantities Being Measured 5 2.1.2 Interrelationship of Quantities Being Measured 7 2.1.3 Units Used in Acoustical fleasurements 8

2.1.4 Derivation from SI Base Quantities 10

2.1.5 Nature of the Physical Reference Standards 11

2.2 Basic Technical Infrastructure 11

2.2.1 Documentary Specification System 11

2.2.1.1 Standardization Institutions 11 2.2.1.2 Survey of Documentary Standards 13

2.2.2 Instrumentation System 14

2.2.2.1 Measurement Tools and Techniques 14

2.2.2.2 The Instrumentation Industry 19

2.2.3 Reference Data 20

2.2.4 Reference Materials 23

2.2.5 Science and People 24

2.3 Realized Measurement Capabilities 25

2.3.1 General Patterns 25

2.3.2 bependence upon Environmental Factors 27 2.3.3 Adequacy Versus Needs 28

2.4 Dissemination and Enforcement Network 29

2.4.1 Central Standards Authorities 29

2.4.2 State and Local Offices of Weights and Measures 29

2.4.3 Standards and Testing Laboratories and Services 29

2.4.3.1 Types of Acoustical Standards and Testing

Laboratories 29

2.4.3.2 Functions Performed 29

2.4.3.3 Detailed Description of a Representative

Industrial Laboratory 31 2.4.3.4 Interrelationships 31

2.4.4 Regulatory Agencies 32

2.4.4.1 Local Regulatory Efforts 32

2.4.4.2 State Regulatory Ffforts 37

i
Page

2.4.4.3 Federal Regulatory Efforts 37

2.4.4.4 Quasi -Governmental Regulatory Units 38

2.5 Direct Measurements Transactions Matrix 38

2.5.1 Analysis of Suppliers and Users 38

2.5.2 Direct Measurements Transaction Matrix 41 2.5.3 Highlights re Major Users. 41

3. IMPACT, STATUS AND TRENDS OF THE MEASUREMENT SYSTEM 45

3.1 Impact of Measurements 45

3.1.1 Functional, Technological and Scientific Applications .... 45

3.1.1.1 Use and Function of the Measurements 45

3.1.1.2 Impacts on Technologies 45

3.1.1.3 Scientific Fields Affected 48

3.1.1.4 Impacts on End Users 48

3.1.2 Economic Impacts 48

3.1.2.1 Costs of Measurement 48

3.1.2.2 Economic Benefits of Measurements 49

3.1.2.3 Example of Economic Cost Benefit Analysis 50

3.1.3 Social and Human Impacts 50

3.2 Status and Trends of the Acoustical Measurement System 52

4. SURVEY OF NBS SERVICES 55

4.1 The Past 55

4.2 The Present — Scope of NBS Services 55

4.2.1 Description of NBS Service 55

4.2.1.1 Support of the International Measurement

System 55

4.2.1.2 Participation in Standardization Organization Activities 57 4.2.1.3 Development of Measurement Methods 57 4.2.1.4 Provision of Reference Data 59

4.2.1.5 Provision of Reference Materials 60

4.2.1.6 Support of Science, Education and the Dissemination of Knowledge 61 4.2.1.7 Existing Measurement Capabilities 61 4.2.1.8 Role in the Dissemination and Enforcement

Network 61 4.2.1.9 NBS Input/Output for NMS/NBS Interaction 63

4.2.2 Users of NBS Services 66

4.2.3 Alternate Sources 67

4.2.4 Funding Sources for NBS Services 67

4.2.5 Mechanism for Supplying Services 67

4.3 Impact of NBS Services 68

4.3.1 Economic Impact of Major User Classes 68

4.3.2 Technological Impact of Servii.e 68

ii
Page

4.3.3 Pay-off Changes in NBS Services 68

4.4 Evaluation of NBS Program . . . . 69

4.5 The Future 71

5. SUMMARY AND CONCLUSIONS 73

5.1 State of the National Measurement System 73

5.2 Role of NBS Acoustics Activities Within the National

Measurement System 74

5.3 Conclusions and Recommendations for Action 74

Appendix A. Methodology of the Study 76

Appendix B. Summary of Background Documents 77 Appendix C. Government Standards Activities 79

References 85

LIST OF FIGURES

Figure 1. The internationally standardized weighting curves for sound

level meters. °

Figure 2. From sound pressure level (SPL) to predicted human response (PHR). ... 10

Figure 3. Infrastructure of standardization institutes in acoustics. 12

Figure 4. Ten different psychophysical units normalized to values at 1000 Hz. 19

Figure 5. Results for several commercial noise exposure meters tested in

a random incidence sound field. 26

Figure 6. Ultrasonic response amplitude data for distance -- amplitude

reference blocks. 27

Figure 7. Acoustical measurement system input-output direct transactions

matrix. 44

Figure 8. Technological impact of precision microphone calibration

processes. 47

Figure 9. Estimated additional cost required to obtain lower noise levels

for medium and heavy duty gasoline-powered trucks. 51

Figure 10. NBS input-output chart showing the interaction between NBS and

elements of the acoustical measurement infrastructure. 54

i i i
LIST OF TABLES

Page

Table 1. Some physical and psychophysical units for measuring noise 9

Table 2. Instrumentation required for acoustical measurements 20

Table 3. Specific instrumentation required for acoustical measurements 21

Table 4. Existing acoustical laboratories 30

Table 5. Municipal noise ordinances: 1976 33

Table 6. Measurement capabilities and services supplied, needs and

services procured, by acoustics measurement system sectors 42

Table 7. Users of acoustical measurement instrumentation 45

Table 8. Factors related to stability and change 54

Table 9, NBS publication output in the field of acoustics 56

Table 10. Participation in national standards organization activities 58

Table 11. Suppliers of microphones submitted to NBS for calibration 62

Table 12. Participants in the National Measurement System/NBS interaction 65

PREFACE

This report was initially prepared during 1974 in response to a request from the

Institute for Basic Standards office, and was intended to be, primarily, an internal,

working document. Thus, the NBS role in the national measurement system for acoustics

has probably been emphasized to a greater degree than what, in reality, actually exists.

Also, because the field of acoustics is a dynamic, rapidly changing area, certain information contained in this report may rapidly become outdated.

1v
THE NATIONAL MEASURE^€NT SYSTEM FOR ACOUSTICS

David S. Pallett and Marilyn A. Cadoff

Institute for Basic Standards

March 1975

EXECUTIVE SUMMARY

This report describes acoustical

measurement processes that are motivated by

societal concern over noise and which are continuations or extensions of traditional

acoustical measurements. In addition,

material is presented to describe an important relatively new application of

acoustical technology, the field of

ultrasonic non-destructive testing.

Acoustics, the branch of science dealing

with sound, has become a field that is an important element in many aspects of our contemporary technological society.

Acoustical measurements are performed in

order to quantitatively characterize noise

levels, to specify noise emissions, to specify the acoustical properties of

architectural materials, and to quantify and

interpret human response to sound, to name

but a few examples. Applications of

acoustical principles to be found in other

aspects of our technology include the use of

ultrasonic acoustic energy to identify and

characterize flaws. These ultrasonic

measurements are performed in order to meet

the increasingly severe requirements for

mechanical integrity and reliability as well

as in response to pressure for material

conservation and increased productivity.

Although the repgrt describes a diverse

range of acoustical measurement tools and

methods, there remdin numerous acoustical

measurements not covered in this report.

These deliberate exclusions were made for

two major reasons. First, resources -- in terms of available time, manpower, and

funding -- were too limited to carry out the

comprehensive literature study which would

have been required to survey adequately such

a broad topic as acoustics. Secondly, it was decided to direct attention to those

areas in acoustics in which the necessity of

obtaining increased objective quantitative

knowledge has recently become apparent, and

that is primarily in the area of noise

abatement and control.

The principal user groups for noise

measurements include various departments,

agencies, and laboratories of Federal ?nd

State governments; manufacturers of

measurement instrumentation, products for

which noise emissions are of immediate or potential concern, or architectural

materials; acoustical consultants,

architects, and urban planners; and

university faculty and staff members

affiliated with research laboratories or speech and hearing clinics. Users of

ultrasonic non-destructive evaluation

equipment include the aerospace, power

generating, construction, metals production,

auto manufacturing, metals fabrication, and

railroad industries.

There are numerous identifiable social,

technological, and economic impacts for

these measurements. Measurement of noise is now an important element in the protection

of hearing. Conduct of some ten to twenty

million annual audiometric examinations will soon demonstrate an increased level of awareness of the effects of noise and of the

importance of hearing preservation in our

society. Acoustical measurement processes

are explicitly involved in noise control and

hearing preservation. Economic impact is more difficult to assess quantitatively, and

a well-defined picture of the economic

impact of acoustical measurements is not yet

available.

The work of the National Bureau of

Standards in acoustics and its role within

the infrastructure of the National

Measurement System is based primarily upon a number of interactive processes. The

substance of the interactive process

consists of such elements as provision and

interchange of test and calibration data and

technical reports, as well as the

development of calibration and test

procedures and measurement methodologies.

Participants in this interactive process

include standards organizations, various

industrial representatives (including trade

associations and individual manufacturers),

professional societies and universities, and

even representatives of foreign

laboratories. Because of the increased

legislative attention given to noise and its

control, and the consequent promulgation of

regulations that require measurements for

enforcement, the adequacy of required

measurement methods is now the subject of

intensive study, both within NBS and within

other Federal, State and local agencies.

The study indicates that there is a continuing demand for improved accuracy and

precision in both the development and

calibration of acoustical measurement
instrumentation and in the evolution of

improved measurement methods. Research in

these areas has traditionally been a strength of the NBS program in acoustics.

The study also illustrates that a significant increase in the number and scope

of legislative actions directed toward noise

control has taken place. State and local

governments are becoming active

participants. Inconsistencies in the

relevant measurements required for effective

implementation of these regulations

introduce ambiguities. These ambiguities

also involve the imprecisions inherent in

these measurements. Consequently,

inequities in trade can arise. A need,

therefore, is shown for acoustical research

directed toward the basic physical

phenomena, the study and evolution of

improved measurement facilities and

instruments, and the improvement of the

required measurement methodologies.
1. INTRODUCTION

1.1. Importance and Status of Field

Nearly all of us are able to speak, to hear, and to interpret sounds. The

importance of sound to man's existence is

attested to by our possession of the

ever-present sense, hearing, and we continually make use of our sense of hearing

to provide us with information from which we

attempt to infer information important to our existence. Sound is, therefore, a physical phenomenon of basic concern and

importance to man.

The more complex civilization has become

the more sound sources have come into being.

Many of the sounds do not convey desirable

information and have little aesthetic value.

They are unwanted sound or noise. Man's

objections to, and attempts to control,

noise have intensified as sources proliferate and the noise level surrounding

man has increased.

Central to our technological concern with the phenomena of sound is the necessity

for accurate quantitative measures of the

relevant physical phenomena. Accurate

measures are essential to the design of

acoustical devices for communication

systems, the improvement of systems for the

recording and reproduction of sound for

entertainment or aesthetic value, and

facilitate the implementation and

enforcement of noise control measures. In short, acoustical measurements are central

to many pprtions of our current

technological society.

1.2. Purpose of the Jtudy

It can be appreciated that measurement

is one of the fundamental activities upon

which human cultures depend. It is

essential for the establishment of objective

quantitative knowledge. Without

quantitative knowledge, many human

activities would become impossible or would

have to be drastically changed. It is therefore appropriate, that the staff of the

National Bureau of Standards review the role

of some of the more important of the

acoustical measurement processes.

All active scientists or engineers are

at some time or another concerned with the

process of measurement. Conduct of a measurement operation makes one a participant in the National Measurement

System. As members of a system which has

its own ordered structure of rules,

definitions, and procedures for guidance in

the conduct of the measurement process, it

becomes advisable for the participant to explicitly understand the structure of the

system. For without this explicit understanding, the participant cannot identify

other individual or institutional

participants or user groups, and cannot

effectively interact with the system to improve his measurement process or operation

.

By making clear the individual's role in

the National Measurement System, several

advantages of an institutional nature

accrue. This particular study is motivated

by a desire to identify the measurement

system elements and interfaces between the

National Measurement System and NBS. As the

measurement system infrastructure becomes

apparent, social, technological, and

economic impacts are delineated. In the

process of defining the system structure,

current measurement challenges are identified. These data are intended to enable optimum allocation of funds, evaluate

current programs in the light of new

information, and plan future directions.

Perhaps, above all, those involved in

defining their individual or institutional

roles in the National Measurement System

will become motivated to redirect their

activities if indicated and thus, to interact more effectively.

1.3. Scope of the Study

Primary emphasis is placed on identification of relevant measurement

processes and units, description of the

measurement system infrastructure, and

indication of the impacts of these

measurement processes upon social issues,

current technology, and economic processes.

Forecasts of possible and probable changes

in both the National Measurement System and

the interaction of NBS acoustic personnel

with this system are presented. Attention

is directed to the following topics:

(1) Measurement of sound pressure level

and related quantities, and the

development and calibration of the

associated instrumentation.

(2) Measurement of the acoustical

properties of architectural

materials and systems.

(3) Measurement of human auditory

acuity, especially audiometric

3
measurements and the calibration of

the components of that measurement

system.

(4) Determination of appropriate metrics

and algorithms to be applied to basic acoustical measurement data to predict human response to sounds.

(5) A brief review of some of the

relevant details concerning the

topic of ultrasonic flaw detection

is also included. Ultrasonic flaw

detection represents a rapidly

growing use of acoustical energy for

the purposes of nondestructive

testing. It is included because it

exemplifies an active contemporary

application of acoustical principles

within our technology, and because

it is a "measurement intensive"

industry. There are numerous other

applications for ultrasonic acoustic

energy, one of which -- medical

ultrasound for diagnostic and

therapeutic purposes -- is described

in another of the National

Measurement System studies[l] in

this series.

1.4. Limitations of the Study

For a number of reasons, there are several important activities in the field of

acoustics which are not described in the

present report and for which the relevant

infrastructure of the National Measurement

System has yet to be delineated. Notable

among these are the fields of underwater

acoustics, physical acoustics, and

physiological acoustics

Underwater acoustics is a relatively new activity within man's utilization of sound,

since it has only been since the early years

of this century that man has been able to make use of sounds for purposes of location,

identification and communication underwater.

Much of the technology is guided and used by

the members of the international naval

community. Some of the more advanced and

sophisticated applications are classified.

Because the resources available were too limited to adequately survey this complex

and yet extremely active field of acoustics,

a conscious decision to omit underwater

acoustics from the scope of this study was made. However, within the U. S. Navy,

integrated systems of reference measurement

standards, performance standards, and

standards laboratories are known to exist.

In the future, it would be desirable to assess the relationship of this largely

defense-oriented activity to the remainder

of the National Measurement System for

acoustics

.

Physical acoustics has not been included

within the scope of this study for several

principal reasons. Initially, the scope of

physical acoustics includes studies ranging

from low temperature physics to the study of

molecular processes in rarefied gases. In other words, the field is itself very extensive and measurements of acoustical

quantities are often of secondary interest.

Moreover, within the field the majority of*

measurement operations are conducted without

concern for adherence to a "standard"

measurement methodology (and in fact

frequently none is appropriate), the

interpretation of the acoustical data is of

irmiediate concern only to isolated relevant

researchers, and the relevance of the

measurement to other acoustical measurement

operations is often only peripheral, however

basic the physical phenomenon.

Physiological acoustics, including the

topic of hearing aid design, testing and

fitting, is excluded principally because of

a concern that the present report should

direct attention principally to physical

measurement processes, without the

introduction of the complications attendant

to biological mechanisms.

The scope of the present report, as has

been indicated, has been principally re- stricted to those activities which are both

motivated by increasing societal concern over noise and involve numerous acoustical

measurements. However, other activities

exist within acoustics which are not described in the present report. The findings of the recent "Conference on Acoustics

and Societal Problems" [2] describe some of

the additional activities. The interested

reader is referred to the conference report

for much relevant material.

4
2. STRUCTURE OF THE MEASUREMENT SYSTEM

2.1. Conceptual System

2.1.1. Quantities Being Measured

The principal physical quantity being

determined when performing an acoustical

measurement is that of the pressure

fluctuation we term sound.

Perhaps the simplest property under

study is the pressure amplitude. Acoustical

signals are complicated time-varying

phenomena, and it is not sufficient to make

one measurement to determine the pressure

amplitude. Rather, it is essential to determine some measure of the pressure

amplitude involving averaging over an appropriate time period. Frequently, we

seek to characterize the temporal

root-mean-square (rms) pressure amplitude,

with some appropriate time period over which

the averaging operation may be performed.

The motivation for many acoustical

measurements lies in a desire for

quantitative estimation of some subjective

response such as loudness, aversi veness , or annoyance which is derived from quantitative

measurements of the acoustical signal.

Therefore, it is not surprising that

measurements are conducted with the explicit

intention of obtaining the specific physical

measurements which are most directly

relevant to the estimation of subjective

response. Three factors enter into

immediate consideration when one sets out to characterize acoustic signals within the

audible range.

1) The first has already been alluded

to: the signals vary with time in a complex manner. It is necessary to obtain the rms pressure amplitude,

averaged over some time period

consistent with both the

characteristics of human hearing and

with the time scale over which the

signal is relatively consistant in

its characteristics.

2) Secondly, the range of pressure

amplitudes which the human sense of

hearing can meaningfully interpret

without discomfort is a range of more than a million to one. Because

of the extent of this range, and

because many subjective reactions t"-' changes in pressure vary approximately logarithmically with the

pressure, it has become customary to

specify pressure amplitudes by

making use of a logarithmic measure

of pressure amplitude. A frequent

measure of an acoustic quantity is expressed in terms of a "sound-pressure-level (SPL)", which

is expressed as follows:

SPL = 10 log

10 rms

20 log^Q / ^rms \ dB re p where p is the temporal root mean square (rms) sound pressure in

pascals (Pa) and p is the rms reference sound pressure in pascals.

The reference pressure, p , is equal

to 20 yPa.

°

It is implicit in this measure that some appropriate time period be used

to define the rms pressure amplitude

P3) The third factor entering into

characterization of acoustic signals

lies in the realization that the

human subjective response to sounds

of equal pressure amplitude, but at different frequencies, is not

linear. That is, the subjective

loudness of a low frequency pressure

fluctuation will generally be less

than that for an otherwise

comparable, mid-audible-range,

signal. In order to account for

this difference, numerous frequency-weighting curves have been

developed over the years. The most

commonly used is termed the

A-weighting characteristic, and it

approximately corresponds to the

inverse of the 40-phon contour of

the human ear. When one determines

sound pressure level making use of

a frequency-weighting characteristic

in the measurement process, one is

. said to determine the

"frequency-weighted sound level",

such as the A-weighted sound level

(see figure 1 for the

internationally standardized

weighting curves for sound level

meters)

.

5
-20

-40

5

-60

-80

1 III III II

B & C

_ bX /

~ A /

-

1 1 1 1

1 1 1 1 1 20 100 500 2000

FREQUENCY. Hz

20 000

These considerations result in

characterization of some of the more simply

defined time-averaged and frequency-weighted

characteristics of the complex pressure

fluctuations. More complicated

characterizations of such factors as peak

amplitudes, statistical measures of sound

levels, and of the temporal fluctuations are constantly being developed. However, the

vast majority of measurements motivated by concern over noise fundamentally involve

determination of sound pressure levels.

Because of interest in quantitative

measures of the total acoustic emission from sources of environmental noise, it is

frequently desirable to determine either the

sound pressure level averaged over many

positions at some reference distance from

the source, or alternatively, the sound

power which is inferred from measurements of

sound pressure at prescribed distances and

angular orientations and from certain

properties of the acoustic field. The total

acoustic power W emitted by a given source

can be related to the mean squared pressure

_2

p under appropriate (far field) conditions

by

P^(r)

pc~

cos e ds,

Thus the acoustic power can be inferred from

measurements of squared rms pressure

amplitude, determinations of the density e [kg/m ] and velocity c [m/sec] of

propagation in the medium, and from

consideration of the area over which the

pressure amplitude is approximately

constant. These measurements are then

related to the intensity of the acoustic

9 field I9r) [W/m ] and integrated over a

2 surface S[m ] enclosing the source to obtain

the acoustic power [W] emitted by the source.

Characterization of environmental noise

generally involves measures of both the

temporal and spatial characteristics of

environmental noise. Typically, one will

either make use of statistical description

of the temporal fluctuations in the acoustic

field, or one will perform some process of

temporal integration to obtain a measure of

the total noise exposure that an occupant of

the space in which the acoustic field exists

has experienced. Procedures for adequate

characterization of the spatial variations

of sound pressure levels are the subject of

current research, but typically, one might

determine contours of equal sound pressure

level throughout the space under study.

These considerations indicate the nature

of the quantities being measured when one is principally interested in characterizing

sound by describing its amplitude

characteristics. However, there is

considerable interest in describing the

distribution of acoustical energy as a function of frequency. Thus there are many

instrumentation elements and systems which

permit one to obtain measures such as the

sound pressure level contained in some prescribed frequency band, or the band

pressure level. Typically, one makes use of

octave band, one-third octave band, or constant percentage bandwidth filters and

analysis schemes. Alternatively, constant

bandwidth filters, such as one Hz or 100 Hz bandwidths, are used.

Many acoustical measurements are conducted to determine the acoustical

properties of architectural materials and

systems. In these measurements, the

quantity being measured is the energy

absorption or transmission properties of

some material. These measurements are discussed more fully in Section 2.2.2.1.

Because man's concern with sound is related to his ability to hear and interpret

sounds, it is natural that the quantitative

meflsMrHinHnt of this ability would be an appropriate subject for study. Indeed, the

measurement of auditory acuity enables one

to assess hearing impairment and to

6
characterize appropriate acoustic signal

processing or noise measurement

methodologies. Characterization of auditory

acuity is typically accomplished by

determining the threshold of hearing, which

is the lowest sound pressure level at which

a subject just perceives a sound. By

comparison with data characterizing the

thresholG for a large sample of the

population with negligible impairment, it can be determined whether or not the

individual's hearing threshold is "normal",

or whether there is impairment.

Having established that one can quantitatively characterize sounds or noises

by determination of the sound pressure

levels or by means of the total acoustic

power emitted, describe environmental noise,

obtain quantitative measures of the acoustic

properties of materials to be used in the

implementation of noise control measures,

and make quantitative measures of hearing

acuity, there is still an additional element

required in any discussion of acoustical

measurements. This element is the

consideration of the subjective reaction to various sounds. An important goal of

psychoacoustical research is the evolution

of algorithms from which one can predict

human response to sounds from the physical

measurement of the sound. The development

of the algorithms is complicated, but in

general involves subjecting experimental

subjects to well characterized acoustic

signals in order to determine corresponding

quantitative measures of the subjective

response. Research in psychoacoustics has

led to the development of frequency

weighting characteristics curves such as the

A-weighting curve mentioned earlier in this

section

.

The preceding considerations have all dealt with quantitative measures motivated

by or related to human perception of audible

acoustic signals. For centuries the scope

of acoustics was limited to the

consideration of the pressure fluctuations

which man could perceive as sound. However,

as our technology has developed, we have

learned to make use of acoustic signals with

principal energy content orders of magnitude

above the frequency band of human hearing,

the so-called ultrasonic range. The

principal uses of ultrasonics considered in

this report are those involved in

identifying the presence of cracks or voids

within solid structures, termed ultrasonic

non-destructive testing (USNDT), and in

studying the acoustic emissions of stressed

systems. Typically, an acoustic pulse is

introduced into a solid structure under

study, and the various reflections from

boundaries of the structure or from the

cracks or voids are studied. The simplest

interpretation of the data suggests that one estimates the size of the crack or void from

the amplitude of the reflected pulse.

Inherent in these considerations is the

understanding that large (relative to the

acoustic wavelengths) flaws will have very

large scattering cross sections with

correspondingly large amplitudes for the

reflected pulses. Acoustic emissions are studied in order to yield information about

flaws which in turn portend failures.

2.1.2. Interrelationship of Quantities

Being Measured

As the preceding section has indicated,

the majority of noise-related acoustical

measurements concern the determination of

sound pressure level. This quantity is inferred from measurements conducted with

regard to concern for appropriate

(relatively short term) temporal averaging

and frequency weighting procedures.

Physically, however, the measurements

concern the determination of pressure

ampl itude.

Concern over the quantitative

characterization of the acoustic radiation

averaged or integrated over all possible

angles gives rise to determinations of the

spatially averaged sound pressure level, or the total acoustic power radiated. To infer

this latter quantity, it is necessary to determine the density of the acoustic medium

and the velocity of sound in order to infer

the intensity of the acoustic radiation

averaged over some appropriate surface.

This intensity is determined from an assumed

relationship between pressure amplitude, density,

and velocity of propagation. Integration of

the intensity over the surface area yields

the power radiated through the surface.

Provided that the surface over which the

measurements are obtained is properly

sampled and that all of the energy radiated

by the source passes through the surface,

these measurements of pressure, density,

velocity of sound, and area yield the

radiated power.

Architectural acoustical materials are characterized by measures of their

fractional acoustic energy absorption or transmission. These properties are inferred

from measurements conducted in special test

facilities. Either a change in rate of

sound pressure level decay is determined

7
(for absorption studies), or the sound

pressure level is determined under

circumstances in which a test structure

serves as a transmitting element that

separates a sound source from a well known

acoustical system (for transmission loss

studies). Once again, the central

measurement process involves determination

of sound pressure level, or of the rate of

decay of sound pressure level.

The measurement processes concerned with

both audiological and psychoacoustical

measurements require the quantitative

assessment of subjective response to a well

specified acoustic signal. For audiological

measurements, the subjective response is

typically a relatively simple detection

task; but for psychoacoustical purposes more complicated subjective responses are studied.

Ultrasonic flaw detection measurements

are performed in order to locate and

characterize flaws in a wide variety of

specimens and materials. A related class of

ultrasonic measurements, called acoustic

emission measurements, are performed in

order to provide information concerning

failure-related phenomena such as crack

propagation. In flaw detection

measurements, time of propagation data are used to infer the location of flaws within

the material under study, and measurements

of the reflected signal amplitude sometimes

are used to estimate the size of the flaw.

In measurements of acoustic emissions, the

amplitude of the emissions is thought to be

related to the magnitude of the

failure-related phenomenon.

2.1.3. Units Used in Aconstical

Measurements

The principal acoustic measurements

frequently are concerned with sound pressure

levels, which are logarithmic measures of

pressure amplitudes. The reference pressure

(the weakest sound pressure perceived by the

"aygrage" person at 1000 Hz) used is 20 x 10 pascals. A sound pressure level near

the threshold of feeling (tickling

sensation) will be 120 dB corresponding to a pressure amplitude of 20 pascals.

The unit for characterization of

acoustic power emissions is the watt. One

watt of acoustic power is approximately the

amount of power produced by one thousand

people, each shouting as loudly as possible;

i.e., an individual person can produce

approximately one milliwatt by shouting.

Acoustical absorption is characterized

by the energy absorption coefficient; e.g.,

an absorption coefficient of 0.95 implies

that 95% of the incident energy is absorbed

by the specimen. Total acoustic absorption

is described in terms of the equivalent area over which all of the incident energy is totally absorbed; this quantity is given by

the product of the surface area and the

corresponding energy absorption coefficient.

The acoustic airborne sound transmission

properties of building elements, such as partitions, are given in terms of a logarithmic measure of the energy transmission

coefficient. That is, if 10% of the energy

incident upon unit area of a partition is

transmitted through and/or re-radiated by the

partition, the transmission coefficient is

0.10, and the appropriate logarithmic measure of the transmission coefficient is given by the transmission loss (TL, where

TL = -10 log (0.10) dB or TL = 10 dB in this

case.

Somewhat more complex single-figure

rating systems are used to summarize the

frequency weighted absorption, transmission,

and impact isolations or structure borne

sound properties of architectural systems.

The majority of audiologic data are implicitly referred to the threshold of

hearing of "normal" individuals and thus

rely upon a reference data base. The units

used to quantitatively assess departures

from the normal threshold, however,

frequently are those appropriate for sound

pressure levels.

Psychoacoust'lcal research has led to such a proliferation of related acoustical

data processing algorithms to yield

predictions of human response from physical

measurements, that there are now more than

35 algorithms used (see table 1 and figure

2). Thus one finds the use of data

involving 35 "units" throughout the

literature, with wide disparities in the

resultant predictions of subjective

responses

.

The units used for ultrasonic

non-destructive testing are at present not

precisely stated or directly traceable to fundamental physical processes. For example, in ultrasonic measurement systems

used for material acceptance on the basis of

internal flaw size, the measurements involve

the use of reference blocks with artificial

defects for system calibration. These

8
Table 1. Some physical and psychophysical units* for measuring noise.

Abbreviation Name A Typical Product Use

PHYSICAL

MR PI W a Y*r\\»i R a n ri P v^c^ c c 1 1 1 o \/0 1 I'lai 1 uw Daiiu ricboUi c lcvc i fnP uca^ Y* nv^i\/on flnn^v^a'hiic I Ui iVcil MppcLiaUUb

UD rL Or"l" a \/o R a n H D c c 1 1 1 o v/p 1

, UULavt: DuilU rrcobuit: Level nuuo 1 iiy CDI oUUilU rrcobUrfc: Level fll 1

1 UK rL imrCi ULLaVc DaiiU rrcbburc Level iraiibpurLdLiori L^u 1 priicri

t

r o T Ln Ur n T o 1 UML

ATMi MrtlLUIaCIUri 1 iiCJc A LUiTUnuri 1 La C 1 Drib C^U \ pillc'l L CUD LINK Kcsiuentiai uwei i ings

CD uorrecLion racLor UTTices ana ractories

CAT tTTecLiVc MrticuiaLion inaex communications tquipment

(TDMI trlNL tTTecxive rerccivcu inoisc Lcvei Ml rcrai

t

farrlUN rnon ^ br

;

Export Manufactures

bb Ulxh oone [br

1

Export Manufactures

LL Louaricss lcVci Kaulo ana ieievision

1 R 1 o \/o 1 P

n

Lc Vc 1 rVul 1 Is. H'f'f'ippc anH P;3r'i"nv*ipc ui 1 iLcb aiiu raLLUi ico NFF iicr IMU IbC LApUoUl c rui eL.uo u M

A n Y*r y^A "Fl*

I r L 1 a 1 L NNT Mn TCP a n rl M n mK o T n H p v INUllic ailU INUIIiUcr lilUcA oLilUUIb ailU nubpiLatb

NflY M r\ \/ oUl raLc VcrilLlcb

NPI llUIoc rUI lULiUli LCVCI OLiiuu I b aiiu nub[-' i La i b

NIP 11 IN Mn"icp nUloe Ps'hinn rxuLIII^ Ppc "i/Hpnl""! ^1 HiAf p 11 "1 n n c rxc b I Uc 1 1 L la 1 UWc 1 1 1 1 ly b urnull Phnn r 1 lu 1 1 Ion) \\ju J r\|J |J 1 1 a 1 1 LC b OSONE Sone (OD) Appl iances

PHR Predicted Human Response All PNL Perceived Noise Level Surface Vehicles PNLT Tone Corrected PNL Ai rcraf

t

SIL Speech Interference Level Office Equipment

SLA A-weighted Sound Level Highways

SLAS Slow Response SLA Construction Equipment

SLB B-weighted Sound Level Metal -working Equipment

SLC C-weighted Sound Level Farm Equipment

SLD D-weighted Sound Level Railcars

SLE E-weighted Sound Level Boats

TWI Traffic Noise Index Highways

*The definitions for most of these units can be found in the following source: About Sound (Office of Noise Abatement and Control, U. S. Environmental

Protection Agency, Washington, D. C, May 1976).

9
PHYSICAL

SOUND PRESSURE LEVEL

ANALYZE

PSYCHOPHYSICAL

WEIGHT

SUM

TONES

OCCURRENCES

SPREAD

DAY-NIGHT

EXPOSURE

SLA SLB SLC SLD

SPL X

OBPL

SLE

DURATION SLAS SLBS SLCS SLDS

STANDARD:

1 ANSI1 lEC1 lEC

1 ISO

S1.4 123 179 R507

LR NR

CFl

SLES CF2

r

TOBPL

OPHON SIL

OSONE

NONE NONE

TNI

ISO R1996

ANSI

S3.

4

PNL

NBPL

GPHON

NOY GSONE

PNLT

EPNL

LL

EAI

NONE

CF3

CF4

CF5

CNR

FAA

36

ISO R532

ANSI

S3.

5

ISO R226

NNI

NPL

NEF

PREDICTED HUMAN RESPONSE PHR •PSYCHOPHYSICAL FREQUENCY WEIGHTING SHOWN IN FIG. 4.

Figure 2. From sound pressure level (SPL) to predicted human response (PHR).

reference standards rely on inadequately

precise primary reference and result in unacceptably large variations between

nominally identical reference blocks. A

well defined primary standard and a thorough

understanding of the physical process of the

measurement relating the measurand to basic

SI units is needed. A proper dissemination

system with clear feedback from the users also needs to be developed. In the area of

ultrasonic acoustic emission measurements,

the knowledge of the absolute sensitivity

and the spectral response of acoustic

emission transducers is of great importance.

In state-of-the-art measurements an attempt

is made to classify flaws which produce

acoustic emissions based on signal strength.

In attempts to improve the measurement

system, researchers are presently

investigating the spectra of the received

signals to determine the nature of the source.

2.1.4. Derivation from SI Base Quantities

Microphones a reciprocity techn

procedure are wel one to calibrate

[Vol ts/micropasca

length [meter], s voltage [Volts],

frequency [hertz]

heats of the acou [dimensionless]

.

units to basic SI

re calibrated by the

ique. The physics of the

1 established, and enable

the microphone sensitivity

1], from measurements of

tatic pressure [pascals],

resistance [ohms],

, and the ratio of specific

Stic medium

The relationship of these

units is well developed.

The majority of acoustical measurement

processes require that the properties of the

acoustic field be determined by means of some electroacoustic transducer. This

yields an electrical signal which is

proportional to the acoustic pressure at the

point at which the microphone is located.

The microphone must be accurately calibrated

10
in order that measurements of the properties

of the electrical signal can be used to infer the analogous properties of the

acoustic field.

2.1.5. Nature of the Physical Reference

Standards

Few physical standards exist in

acoustics. The principal phenomenon under

study in most of the measurement procedures

is the temporal average squared pressure

fluctuation we term sound. A standard

source of sound would therefore be, in

principal, desirable. However, the

stability of most sources of sound is not as high as would be desired for a standard

source. There are two types of devices used

for reference sound source purposes. The

term "reference sound source" refers to a device constituting a source of sound for

which the acoustic power output has been

previously determined, or for which the

power output characteristics of similar

devices have been known. Several

aerodynamic devices are currently available

for use as reference sound sources and are often used as a source of comparative data

in determining the acoustic power output of

noise sources. A second type of device is

used to produce a reference sound pressure

,

and is used for the purposes of field checks

on the sensitivity of microphones. These

devices are termed pistonphones or microphone calibrators, and are produced by

several manufacturers.

2.2. Basic Technical Infrastructure

2.2.1. Documentary Specification System

2.2.1.1. Standardization Institutions

In the context of this report it should

be clearly understood that there are several

types of standards. So called "measurement

methodology" standards deal with

specification of techniques for physical

measurements while other standards provide

definitions of descriptive terminology. The

class of standards referred to as engineering or industrial standards specify

methods of test and document agreements on such parameters as dimensions, performance

and physical characteristics for products

that are specified, designed, manufactured

and sold. Industrial standards usually

include more specific types of standards

termed product standards, commercial

standards, and safety standards. The

majority of these industrial standards are normally not a matter of law, and most of

the relevant acoustical standards are developed in the private sector.

However, mandatory standards are issued

by municipal, state and Federal governments

in areas such as health and safety or pollution control and abatement. The

incorporation of widely accepted standards,

whether measurement methodology, descriptive

terminology, or industrial standards into

contracts, codes and regulations has the

effect of rendering them mandatory.

The overall infrastructure of

standardization institutions in the field of

acoustics is shown in figure 3. In addition

to those organizations shown, there is significant interaction with the mechanical

shock and vibration infrastructure.

International standards dealing with

instrumentation for acoustical measurements

fall under the purview of International

El ectrotechnical Commission Technical

Committee 29 on Electroacoustics (IEC/TC29).

The U. S. Technical Advisory Group to IEC/TC29 consists of three related American

National Standards Committees: SI on Acoustics, S2 on Mechanical Shock and

Vibration, and S3 on Bioacoustics . The

Acoustical Society of America serves as Secretariat of SI, S2, and S3, and thus serves as liaison between technical experts

and the American National Standards

Institute.

International standards dealing with

acoustical measurements (other than those

directly concerned with instrumentation) are

the responsibility of International

Organization for Standardization Technical

Committee 43 on Acoustics (IS0/TC43). There

are two subcommittees under IS0/TC43 which

work independently — Subcommittee 1 on Noise (IS0/TC43/SC1 ) and Subcommittee 2 on Building Acoustics ( IS0/TC43/SC2) . American

National Standards Committees SI and S3

function as the U. S. Technical Advisory

Group to IS0/TC43/SC1 and American Society

for Testing and Materials Committee E-33 on Environmental Acoustics serves as U. S. Technical Advisor to the IS0/TC43/SC2.

Both IEC/TC29 and IS0/TC43 are active at present, particularly with regard to measurement standards needed in conjunction

with the worldwide proliferation of noise

regulations. The Commission of the European

Communities ("Common Market") is becoming

increasingly active in noise measurements

and has established liaison with

IS0/TC43/SC1

.

11
IEC/TC29 ELECTROACOUSTICS

INTERNATIONAL

U.S. CONSENSUS

STANDARDS

ORGANIZATIONS

PROFESSIONAL &TRADE

ASSOCIATIONS

& GOVERNMENT

AGENCIES

Figure 3. Infrastructure of standardization institutes in acoustics.

12
International activities concerning

aircraft noise mainly are the concern of the

International Civil Aviation Organization

(ICAO) Committee on Aircraft Noise (CAN).

United States liaison with ICAO is handled

by the U. S. Department of Transportation.

Numerous Federal, state, and local

agencies have promulgated noise regulations

based on objective measurements. In some cases, these agencies have prescribed, or

will prescribe in the future, measurement

procedures. Federal agencies in this

category include:

0 Environmental Protection Agency

0 Department of Transportation

0 Department of Labor

0 Department of the Interior

States and cities which have been

particularly active in establishing

quantitative noise regulations include

California, Illinois, New York City, and

Chicago. These Federal, state, and local

agencies usually have very limited

interaction with the standardization

institutions shown in figure 3. Additional

material on this topic can be found in

Section 2.4.4.

The majority of broad, generic

acoustical standards ir the United States

are produced by the three American National

Standards Committees (SI, S2, S3) and by

American Society for Testing and Materials

Cormiittee E-33. These committees follow

well-established consensus procedures and

thus, their standards reflect inputs from

professional end trade associations,

consumers, and government agencies. Many

professional and trade associations (see

figure 3) also produse their own acoustical

standards, the most active organizations

being the Society of Automotive Engineers,

the American Society of Heating,

Refrigerating, and Ai r-Conditioning

Engineers, and the Ai r-Conditioning and

Refrigeration Institute. Some organizations

(notably the American Society for Testing

and Materials and the Society of Automotive

Engineers) submit their acoustic standards

for approval by the American National

Standards Institute.

There is a limited number of Federal

specifications dealing with acoustical

materials. However, the Department of

Defense and the General Services

Administration now more frequently require

Federally purchased items to meet prescribed

specifications concerning their acoustic

performance than in the past. For the most

part, these agencies do not issue new measurement procedures but rely on existing

standards. The Department of Housing and

Urban Development and the Department of

Transportation have established policies

concerning the noise levels (at a prospective building site or along a highway) which must not be exceeded to qualify for Federal financial assistance.

These policies spell out the required

measurement procedure.

Overall, the large number of noise

regulations and noise-related contractual

arrangements in recent years has

dramatically increased acoustic

standardization activities. The standards

community is preparing for this work and a trend toward national and international

harmonization is becoming evident.

2.2.1.2. Survey of Documentary Standards

The Noise Control Act of 1972 (PL

92-574) gave the U. S. Environmental

Protection Agency a wide range of authority

for the establishment of noise emission

standards for products, regulations on products intended to reduce the noise of

related products, and for the coordination

of related research and noise control in the

Federal agencies. This Act specifically

calls for NBS-EPA cooperation in regard to research and development of improved methods

and standards for the measurement and

monitoring of noise.

In cooperative work undertaken prior to the enactment of this legislation, NBS

prepared a compilation of more than 200

acoustic standards that are believed to be

specifically relevant to noise control and

abatement. NBS Special Publication 386

"Standards on Noise Measurements, Rating

Schemes, and Definitions: A Compilation"

[4] provides this information.

The publication presents material

assembled from the various standards,

industrial and trade organizations, and from

the relevant technical and scientific

societies concerned with acoustics. No attempt has been made to review or to critically evaluate the standards, although

a serious attempt has been made to include

in the listing all those standards that are available and relevant. Because of the

broad range of topics in acoustics, the

standards cover a broad scope including:

13
— measurement techniques and

instrumentation — rating schemes — definitions —- equipment and product

speci f ications — subjective measurements and

response to noise — calibration methods.

The compilation includes paragraphs

describing the standards and giving a brief

summary of the intent and/or scope of each

standard. In some cases the text is drawn

from the official description of the

standard as issued, while in others the

spirit of the standard is described. An Appendix lists the names and addresses of

the various organizations or societies and

their acoustical standards committees. All

information available as of January 1, 1976,

is included.

Because of the lack of central

coordination in standards writing activities

of the United States, there are numerous identifiable deficiencies in the

organization, structure, and

interconsistency of the relevant acoustical

standards.

Some shortcomings of the nation's

acoustical standardization system have come

into prominence as a consequence of

attentioh to the issues of: — consumer/workplace safety — environmental pollution control — barriers to international trade.

A number of recent legislative actions in

response to these issues give impetus and a sense of urgency to the development of

standards and measurement methods that are needed for the effective implementation of

national programs on noise abatement and

control. The laws that have been enacted

rarely call specifically for new or improved

measurement standards, yet they require them

implicitly. The sense in which they are implicitly required is that the enforcement

of these regulations must be based upon

uniform and equitable measurement

methodology in order to maintain economic

equitability among the affected groups

(often manufacturers).

In the technology of ultrasonic

nondestructive testing. Technical Committee

E-7 of the American Society for Testing and

Materials has produced several methods of

test and recommended practices covering a wide range of ultrasonic testing. These

include the evaluation of testing systems

[5], fabrication and checking standard

reference blocks [6, 7] and methods of

inspection for structures and products [8].

2.2.2. Instrumentation System

2.2.2.1. Measurement Tools and Techniques

Most sound-measuring devices are designed to respond either to sound pressure

or to particle motion. Of the two quantities, sound pressure is easier to measure accurately over a wide range of

frequencies and amplitudes. Hence,

measurement of pressure is much more prevalent than that of velocity. Thus,

almost all instruments for the accurate

measurement of sound employ transducer

elements which respond to sound pressure.

Such an element is commonly referred to as a pressure microphone. Its purpose is to transform acoustical energy into electrical

energy

.

In order that we might properly infer

the corresponding properties of the acoustic

signals from the electrical signal provided

by the microphone, it is essential that the

calibration of a microphone be accurately

known. Calibration is accomplished by means

of the reciprocity technique (developed at the National Bureau of Standards), and is described fully in American National Standard

Method for Calibration of Microphones,

SI. 10-1966 [9]. This calibration process

provides the electrical output of the

microphone [volts] in response to some specified pressure fluctuation

[micropascal s] , and is an important implicit

factor in most acoustical measurements.

Instrumentation systems for noise

measurements perform the following measurement and signal processing operations. The

sound pressure is converted into an electrical signal by a microphone. This

signal is amplified and passed through a filter which weights the various frequency

components of the signal. The filtered ac signal is then detected (usually converted

to a root-mean-square dc) and averaged over

an appropriate time interval. This detected

signal is then either displayed via some

14
read-out device, or recorded on a magnetic

tape recorder and brought back to the

laboratory for analysis.

A device has evolved called a sound

level meter, which is a relatively simple

self-contained instrumentation system. Its main use is to measure sound pressure levels

in air. A sound level meter consists of a microphone to transduce the sound into an electrical signal, an amplifier to raise the

microphone output to a useful level, a calibrated attenuator to adapt the

instrumentation to the sound level being

measured, an indicating instrument

exhibiting ithe measured sound level,

weightings (A-, B- , and C-) to adjust the

frequency characteristic of the response,

and an output connection to accommodate

additional measuring equipment.

Sound level meters usually are manufactured to the specifications contained in one or more of the following documents:

0 International El ectrotechnical

Commission Recommendation on Precision Sound Level Meters,

Publication 179 (1973) [10].

0 American National Standard

Specification for Sound Level

Meters, SI. 4-1971 [11].

0 International El ectrotechnical

Commission Recommendation for Sound

Level Meters, Publication 123 (1961)

[3].

International El ectrotechnical Commission

Publication 17<l(1973) gives tolerances for

all three weighting networks. American

National Standard SI. 4-1971 defines several

types, or classes, of sound level meter with

different tolerances. Because of diverse

precision and accuracy requirements for

different applications, four types of sound

level meters are specified: Type 1 -- Precision, Type 2 -- General Purpose, Type

3-- Survey, and Type S -- Special Purpose,

with different tolerances for the Type 1, 2,

and 3 instruments. American National

Standard SI. 4-1971 specifies a number of

additional characteristics of sound level

meters, including dynamic range, directional

response, and sensitivity to various

environmental conditions. Of particular

importance is the detector circuit, which

should provide true root-mean-square

response to signals of different crest

factors and provide appropriate averaging

times corresponding to the specified "fast"

and "slow" dynamic characteristics. The

American National Standard Type 1 tolerances

are essentially identical to the

International Electrotechnical Commission

tolerances except below 100 Hz where the

American National Standard Tolerances are tighter. If direct measurements are to be

made of the A-, B-, or C-weighted sound

level, the allowable tolerances on the

frequency weighting should be clearly

referenced to one of the above standards.

In acoustical measurements where a frequency analysis is required, it has been

traditional to use a bank of contiguous

band-pass filters, and to switch through

them sequentially to obtain the sound

pressure in each frequency band. More

recently, real-time analyzers have become

available which have parallel filters, with

detection and read-out for each frequency

band. Alternatively, the instantaneous

voltage from the microphone can be passed

through an analog-to-digital converter which

is interfaced to a computer. Filtering and

detection are done digitally within the

computer.

A complicating factor relevant to the

preparation of measurement methodology

standards is the fact that the measurement

standard should not assume any particular

instrumentation configuration. Yet

discussion of instrumentation performance

specifications cannot be neglected or omitted, although the principal concern of

the measurement standard is most properly

with overall system performance, and not

that of individual system elements.

It is the authors' judgment that

frequency analyses required for regulatory

actions will not generally require

measurements in frequency bands narrower

than octave or one-third octave bands. The

International Electrotechnical Commission

Standard on Octave, Half-Octave, and

Third-Octave Band Filters Intended for the

Analysis of Sounds and Vibrations,

Publication 225 (1966) [12], defines the

center frequencies and sets limits on terminating impedances, effective bandwidth,

attenuation in the pass-band, attenuation

outside the pass-band, overall tolerances,

harmonic distortion, and the effects due to environmental conditions. American National

Standard Specification for Octave,

Half-Octave, and Third-Octave Band Filters

Sets, SI. 11-1966 [13], is a rather more

detailed document which establishes three

classes of band filters. Classes I and II for octave band filters and Classes II and

III for half-octave and one-third- octave

band filters.

15
The choice of a filter for a given

measurement is based upon the accuracy

required. The bandwidth error of a filter

depends upon its transmission loss at the

band edges, the slope of the transmission

loss characteristic outside the band, and

the input noise spectrum slope. Appendix B of American National Standard SI. 11 -1966

discusses the subject and gives data and

references allowing selection of filter

characteristics which will yield

measurements falling within specified error

limits at various noise spectrum slopes.

The electrical signal from a microphone

is typically comprised of the sum of

components at many frequencies. The

measuring instrumentation should "detect"

the root-mean-square value of this signal,

averaged over the desired time interval.

The International Electrotechnical

Commission Standard on Precision Sound Level

Meters, Publication 179 (1973), requires

that instrumentation complying with that

standard be able to measure the combination

of signals of two non-harmonic frequencies

to within +0.1 dB of the true rms value.

Although noise measurement

instrumentation with different principles of

operation may be calibrated to yield the

same results on steady-state signals, such

may not be the case for transient signals

such as motor vehicle pass-bys. It is

recommended that measurement standards for sources which produce transient sounds

include specific criteria for system

response to one or more well-defined

transient events (e.g., a pure tone that is amplitude- modulated in a specified manner).

Generally speaking, the primary function

of acoustical materials in noise control is to impede the undesirable' effects of sound

reflection. Architects rely heavily on the use of acoustical materials. Such materials

are rated over a range of frequency

according to their acoustical absorptivity.

The two most prevalent methods for measuring

the sound absorption coefficients of

acoustical, architectural or building

materials are the reverberation room method[14] and the impedance tube

method[15].

The reverberation room method for

measuring the sound absorption coefficient

of a test specimen is determined by

"measuring the- change in the rate of decay of

sound in a reverberation room when a test

specimen is brought into it. In a routine

test, a test specimen is placed centrally on

the floor of the room. A test signal is turned on long enough for the sound pressure

level to reach a steady state level in the

room. The signal is then turned off and the

time it takes the signal to decay to some prescribed level ^s measured. The

absorption. A, (m ) , of the room and its

contents is calculated from the Sabine

equation

^ 0.9210 Vd

c

3 where: V = volume of the room, m

d - rate of decay, sec.

d = speed of sound, m/sec.

The decay time measured with the specimen in

the room is then compared with that obtained

when the room is empty. The difference in

the decay times is a function of the sound

absorption of the test specimen.

The impedance tube method for measuring

the sound absorption coefficient of a test

specimen is determined by measuring the

difference between the maximum and minimum

sound pressure levels in a standing wave set

up within an impedance tube. Acoustic waves

from a source are reflected by the test

specimen and combine with the incident waves

to form a standing wave pattern along the

tube. This pattern is explored with a movable microphone to locate and measure the

maximum and minimum sound levels. The

difference between these two pressure levels

is a measure of the sound absorption of the

test specimen.

Of the two, the reverberation room method is the most widely accepted method

for conducting such measurements.

In both of these measurement processes,

the parameter of interest is the

dimensionless fraction of incident energy

which is absorbed by the test specimen.

This parameter is inferred from measurements

of pressure (for the tube method) and from

measurements of pressure and the time rate of squared pressure decay (for the

reverberation room method).

Acoustic energy transmission occurs in one or more of three principal manners: (1) as airborne sound transmitted along

continuous air paths (2) as structure-borne

sound which typically originates from direct

impulses (e.g., footsteps) or direct

mechanical contact between vibrating

machinery and the building elements or (3) a combination of both (e.g., the sound from a power lawnmower causing a window to vibrate

16
and radiate acoustic energy into a room).

In the case of airborne sound

transmission, there are several highly

specialized testing methods for the

evaluation of the acoustic transmission

properties of such building elements as ventilation ducts or mufflers. These test

methods tend to become specially adapted to the particular requirements of the specific

industry concerned, and in general are given

in terms of measures of the dimensionless

pres^sure ratios at specified positions.

For the case of structure-borne sound

transmission, since mechanical energy can propagate as flexural or compress ional waves within diverse structural elements, the

tools and test methods are potentially

complex. In fact, only one generally

accepted test method dealing with the

measurement of structure-borne sound has

been adopted to any significant extent

within this country. This test method deals

with the assessment of the sound emitted

into a room when the floor of the

superjacent space is mechanically excited by

a standardized form of impact excitation.

Since the data tend to be strongly

varying functions of frequency, they are often further classified by making use of a specific frequency weighted curve-fitting

procedure to yield a single number rating

called an Impact Insulation Class (IIC).

This single number rating is taken to be more or less indicative of the

frequency-averaged impact response and

structure-borne transmission properties of

the floor-ceiling assembly.

The most common form of transmission of

acoustic energy through structures, however,

is the case of airborne sound transmission

involving the mechanical vibration of a structural element. The measurement process

involves determination of the difference

between the space-time average sound

pressure levels in two reverberation rooms separated by a wall containing a test panel

under study. Following a simple normalization process, this measurement yields a measure of the fractional portion of the

energy incident upon the panel which is transmitted into the adjacent space through

the panel [16,17].

As in the case for direct mechanical

(impact) excitation, the data are subsequently used in a frequency weighted

curve-fitting procedure to obtain a single

number rating called the Sound Transmission

Class (STC). This rating, which can be used

for comparing wall or floor specimens for

general building purposes, is designed to correlate with subjective impressions of the

sound insulation provided against the sounds

of noise in buildings [18].

A description of the tools and

techniques used to determine the threshold

of normal hearing is presented in Section

2.2.3. In this section it should suffice to note that the principal tool is the

audiometer, which consists mainly of an audio oscillator or noise generator and

filters, an attenuator, appropriate

amplifiers, and one or two earphones.

Mainly, we hear by conduction of sound

by air. However, if a small vibrator is placed on the skull, sound is conducted by

the bones of the head to the inner ear. A person with a middle ear difficulty could

show an impaired hearing level by air

conduction, but have normal hearing by bone

conduction. Physicians use this difference

between hearing by bone or air as a diagnostic tool. However, there are no standard reference threshold data for

hearing by bone conduction and a standard

procedure for calibrating the bone vibrators

has just begun to be developed.

There are several methods frequently

conflicting for adjusting physical

measurements so as to reflect the human

response to environmental noise. Some of

these methods are embodied in domestic

regulations and national and international

standards

.

After a measurement of the physical

sound pressure level has been made, there

are two major ways to process the data to yield adjusted data predicting the response

of a person to the sound. First, a single

weighting network characteristic of the

simplified human response may be applied to the frequency components of the sound as measured on a sound level meter. Second,

the sound may be frequency analyzed into

several band pressure levels by a frequency

analyzer. From the resultant frequency

distributions more complex measures of the

human response may be computed. The names

of four physical units and 35 psychophysical

units are given in table 1. The

relationships among the various

psychophysical units designed to reflect the

Predicted Human Response (PHR) are depicted

in figure .2. Each block in the diagram

represents the name of a different unit for

measuring the physical sound or for

17
predicting the psychological response to that sound.

Many of these procedures for adjusting

physical measurements of sounds so as to reflect the human response are based upon

data collected by the paired-comparison

method. In paired-comparison experiments

human listeners are asked to Compare two different sounds and report which one is judged "louder", "noisier", "more

unpleasant", "more unacceptable", etc. By

collecting judgements on many pairs of

sounds it is possible to elabo>^ate "equal

loudness contours", "equal noisiness

contours", etc., depending upon the verbal

descriptor used to define the listener's

response.

For example, if the single weighting

network is used, a set of frequency weights

proportional to the simplified human

response is applied directly to the sound

pressure level measurement. As can be seen

in figure 2, five different sets of weights

may be applied, producing the A-, B-, C-,

D-, and E-weighted sound level.

The ten psychophysical units designated

by asterisks in figure 2 are plotted in

figure 4. Inspection of the figure reveals

that the axes embrace the entire range of

audible acoustic frequencies (20 Hz-20 kHz)

and most of the range of audible acoustic

intensities -- from the threshold of hearing

(about 0 dB) to the roar of a jet takeoff

(about 120 dB). If one assumes that the

human perception of acoustic frequency and

intensity is roughly logarithmic, then the

disputed area where the ten frequency

weighting contours disagree could represent

from 10-20 percent of the total decibel

measurement above the threshold of hearing

(International Organization for

Standardization R389 [19]). For the 90 dB

level shown in figure 4, this discrepancy

would be +15 dB.

The measurement tools and techniques

used to perform ultrasonic non-destructive

testing are rather different from the ones previously discussed. Frequently, the

objective of a non-destructive test measurement operation is to identify the presence

of an internal flaw such as a void or crack

within a solid. The principal measurement

tool used to accomplish this identification

is termed an ultrasonic flaw detector, and

it consists of an electronic pulse

generator, a receiving amplifier, a gate

system used either to protect the receiver

from the energy developed by the pulse

generator or to enable attention to be

directed to some specific temporal portion

of the received signal, and a cathode-ray-tube display. The output of the

pulse generator is applied to a piezoelectric transducer, which generates a pulsed acoustic signal within the test

specimen. Reflections of the pulse generate

electrical signals in the receiving transducer which are subsequently amplified and

displayed on the display tube. From the

amplitude of the reflected signal the size

of the flaw and its location can be

estimated

;

The process of flaw detection and

identification is also aided by the fact

that the amplitude of the reflected signal

is affected by the inherent acoustic losses

within the material under study, and by the

physical size (deduced from the scattering

cross section) of the flaw. Because the

technology is oriented toward empirical

solutions of measurement problems, and

because the technology is also heavily

interrelated with metallurgy, the means of

system calibration commonly used makes use

of sets of "reference standards". Here the

term is used to denote right circular

cylinders of varying diameters and lengths,

with flat bottomed holes of varying

diameters, used for the purpose of providing

apparent man-made flaws of known geometry

and location. These reference standards are artifacts used for the purposes of system

calibration. Test specifications will

typically require that the instrumentation

be capable of identifying a 3/64" hole in a 4" thick block of aluminum, steel, or titanium. Because of the empirical nature

of the technology, complete sets of

reference standard blocks typically include

three hole diameters in each of 19 standard

thicknesses (a "distance amplitude" set)

plus another set of eight hole diameters in one standard thickness (an area-amplitude

set). These artifacts become an important

part of the instrumentation system.

It is instructive to consider the types

of instrumentation required for the

performance of typical acoustical

measurements. At least seven categories can

be defined, as listed in table 2. A further

breakdown of specific instruments and

instrumentation systems typically contained

within these seven categories is presented

in table 3.

Products listed in the first two categories enable the measurement of an acoustical or related structural vibration

18
120

CO

100

o

CM

GQ 80

a

T LU>

UJ 60

REsu 40

00

UJ

CC

Qo 20

o

to

0

1—I I I I I 1

1

1—I—I I I I I

100

8o|^SUBWAY TRAIN

-VACUUM CLEANER

y 60-1-

^'^A-WEIGHTED SOUND

LEVEL

\IS0 R389 40--

\ \

\

'

I » »I I II

20"

J i I I I I I II

—I

1—I I I 1 1 1

1

-JET TAKEOFF

-AVERAGE RESIDENCE

SOFT WHISPER

rTHRESHOLD OF^HEARING"

_J '

I I I I I II 30 100 300 1000 3000

FREQUENCY, Hz

Figure 4. Ten different psychophysical units normalized to values at 1000 Hz.

10 000

property by measurement of analogous

properties of an electric signal. That is,

the transducers develop electrical signals

which allow one to infer the corresponding

acoustical or vibrational information from

measurement of the properties of the

electrical analog signal. The third

category lists the instruments and

instrumentation systems used to quantitatively characterize noise emissions

or environments. The fourth category lists

representative general purpose electronic

instrumentation used to obtain appropriate

inferences from measurements of the

electrical analog signals. The more specific audio signal processing and

analysis instrumentation elements are listed

in the fifth category. The sixth category

lists special purpose acoustical

instrumentation produced for research or special purposes. The seventh category

refers to those specific instrumentation

elements required to apply acoustical

measurements to the technology of ultrasonic

non-destructive testing and evaluation.

2.2.2.2. The Instrumentation Industry

As noted earlier, the instrumentation

required for the performance of acoustical

measurements is widely varied. This is

largely a consequence of the

interdisciplinary nature of acoustics, and

because a large number of related physical

phenomena are of interest. The

instrumentation industry involves a large

number of manufacturers of related

instrumentation, instrumentation systems,

and materials and systems for the purposes

of noise and vibration control. Four

reasonably distinct categories emerge.

1. Instrumentation for Dynamic

Measurements

2. Hearing Conservation Equipment

3. Materials for Noise and Vibration

Abatement

4. Systems for Noise and Vibration

Abatement
Table 2. Instrumentation required for acoustical measurements.

I. Microphones and Related Accessories

II. Vibration Transducers and Related Accessories

III. Sound Level Meters, Noise Exposure Monitors, etc.

IV. General Purpose Electronic Instrumentation

V. Audio Signal Processing and Analysis Instrumentation

VI. Special Purpose Acoustical Instrumentation

VII. Ultrasonic Non-Destructive Testing Instrumentation

Of these four categories, the first two contain instrumentation of the types listed

in tables 2 and 3, supplemented by products

specifically intended for the implementation

of hearing conservation programs. The other

two categories contain listings of

manufacturers of instrumentation intended

for the implementation of noise abatement

surveys or programs, supplemented by

products required for the absorption of

acoustical or vibrational energy.

Collectively, the suppliers (for which a current listing is given in S)V Sound and

Vibration [20] annually) represent the major

sources of instrumentation and noise-control

oriented materials and systems at the

present time.

Although there are numerous manufacturers and suppliers of

instrumentation intended for acoustical

measurements, the m.ajority do not supply

products included in all of the categories.

Two manufacturers, however, do have such an extensive acoustical instrumentation product

line that their products are found in nearly

all acoustical laboratories. One of these

is a Danish manufacturer, whose products are marketed in the United States through an affiliate. The other is an American firm.

An adequate estimate of the economic

magnitude of the instrumentation industry

producing and/or marketing the required

acoustical measurement instrumentation is

not at present available. Currently, only

scattered, fragmented estimates of various

economic factors are available, and

additional study by trained economists is necessary. Some of these factors are indicated in Section 4.3.1.

There is not sufficient economic data

available at the present time to permit

estimates of the relative importance of

imports vs exports of acoustical measurement

instrumentation. There is, however, some indication that there are appreciable

exports of audiometric instrumentation [21]

and of sophisticated digital systems for the

accomplishment of fast Fourier transform and narrow band analysis. Eighteen of

twenty-three known major manufacturers of

audiometers are located in the United

States

.

Because of the absence of reference

standards or artifacts in acoustical

measurements, measurements made with the

products of the acoustics instrumentation

industry are only rarely traceable to reference standards. In the United States,

at the present time, perhaps the only

"traceable" factor in the measurement

process may be that of the calibration of

the microphone or accelerometer used to obtain the analog signal from which the

acoustical properties are inferred. The

calibration services of NBS are often cited

as a "traceable" factor in these

measurements, despite the fact that the

traceability may be rather remote. For

example, a microphone may nat be directly

calibrated at NBS, but rather it is

calibrated using another microphone which

has been calibrated at NBS. Details of

these services are presented in Sections

4.2. and 4.3. of this report.

2.2.3. Reference Data

Data pertaining to the determination of

the threshold of hearing, and to performance

data on architectural acoustical materials

20
Table 3. Specific instrumentation required for acoustical measurements.

I. Microphones and Related Accessories

Condenser Microphone Cartridges

Electret Microphone Cartridges

Piezoelectric Microphone Cartridges

Preamplifiers/Signal Conditioners/Power Supplies

Pistonphone Calibrators

Sound Level Calibrators

Reciprocity Calibration Apparatus

Electrostatic Actuators

Windscreens

... Spherical (Cloth and/or Polyfoam)

.... Nosecones

Random Incidence Correctors

Directional Microphone Accessories

... Line Microphone or "Shotgun" Units

... Parabolic Reflectors

Probe Tubes

Outdoor Microphones

... Dehumi difiers

... Bird Repel! ant Adapters

Carrier/Multiplexer Units

Hydrophones and Hydrophone Arrays

II. Vibration Transducers and Accessories

Accel erometers

Velo.city Transducers

Force Gauges

Mechanical Impedance Heads

Displ acement Transducers/Instruments

. . . Mechanical

. . . Capacitati ve

... Optical

... Stroboscopic Devices

Preamol ifiers/Signal Conditioners

.. . Charge Amplifiers

. . . Voltage Amplifiers

... Integrators

Vibration Meters

Vibration Severity Meters

Accel erometer Calibrators

Vibration Transducer Mounting Hardware

III. Sound Level Meters, Noise Exposure Monitors, etc.

General Purpose Sound Level Meters

Precision Sound Level Meters

Impulse Precision Sound Level Meters

Noise Dose Meters/Noise Dosimeter/Noise Exposure Meters

... Personal Units

... "Readers" or Monitors

... Monitor- Devices for Fixed Installations

Noise Limit Indicators

Noise Exposure Statistical Distribution Analyzers

IV. General Purpose Electronic Instrumentation

Vol tmeters

Logarithmic Voltmeter Converters

Low Noise "Audio Frequency 'Measuring Amplifiers

21
Phasemeters

Osci 1 loscopes/Osci 1 lographic Recorders/Graphic Level Recorders

Analog Magnetic Tape Recorders

... Instrumentation Type (FM and Direct)

. . . Audio Type

Digital Event and Transient Recorders

Delay Lines

... Digital

. . . Analog

V. Audio Signal Processing and Analysis Instrumentation

Audio Frequency Osci 1 lators

Heterodyne Slave ("Tracking") Filters

Tracking Frequency Multipliers

Heterodyne Analyzers

Constant-Percentage-Bandwidth Frequency Analyzers

Third-Octave Band and Octave Band Audio Frequency Analyzers

Real Time Third-Octave Analyzers

Real Time Narrow Band Analyzers

Digital Signal Processing Instrumentation

... Fast Fourier Trans form/ Narrow Band Analysis Systems

... Signal Correlation Systems

... Computer Interfaces and Peripherals

VI. Special Purpose Acoustical Instrumentation

Reference Sound Sources

. . . Aerodynamic

... Loudspeakers/Omnidirectional Sound Sources

Standing Wave Tube Apparatus

Reverberation Processors

Tapping Machine

Vibration Generators/Exciters

Vibration Exciter Control Devices/Compressors

Artificial Ears Artificial Mastoids

Artificial Voice

Audiometers

Audiometric Earphones

Audiometric Earphone Couplers

Audiometer Calibrators

Audiometer Booths/"Quiet Rooms"

VII. Ultrasonic Non-destructive Testing Instrumentation

Ultrasonic Flaw Detector

... Search Unit: Surface wave; contact

... Search Unit: Longitudinal wave; immersion

... Angle Beam: Contact or Immersion

Couplant medium

Test Specimen/Transducer Manipulation System

Imnersion Tank

Reference Standards

Acoustic Emission Amplifiers

Acoustic Emission Signal Processor*

... Discriminator Module

... Event Counter Module

... Event Count Ratio Module

... Linear Emission Rate Module

... Log Emission Rate Module

Acoustic Emission is a relatively new field, and the terminology

is not standardized.

22
constitute most of the formal acoustical

reference data.

The zero hearing threshold level,

corresponding to normal hearing in the

population, was obtained from measurements

of the threshold of hearing (in volts) of

large numbers of young adults. Results were

usually presented in terms of a median

earphone voltage. However, since earphone

response could change over time, it was decided to retain threshold information in

terms of sound pressure. Accordingly the

earphone was placed on an artificial ear, or coupler (developed at NBS and called the NBS

9-A coupler), the voltage corresponding to threshold applied and the sound pressure in

the coupler measured. This procedure was repeated at each frequency of interest,

thereby obtaining a set of reference

threshold sound pressures.

Since the coupler is not an exact

acoustic duplicate of the human ear the

sound pressure produced by an earphone is not the same in the coupler as it is in the

ear. Furthermore, while threshold pressure

in the human ear is presumably independent

of the earphone used, the reference

pressures generated in the 9-A coupler are found to be different for each earphone

type. Thus, in this country, a set of data

corresponding to the sound pressures

generated in the NBS 9-A coupler, is recorded. For each earphone type the

applied voltage is that which corresponds to the threshold of hearing. Thus, the coupler

pressure data correspond to the threshold of

hearing. Each time a new earphone type is designed and manufactured for audiometry,

one has to perform a loudness-balancing

procedure with the new earphone versus a standard earphone to establish new reference

pressures. These reference pressure data

then constitute the basis of the

corresponding threshold data [22,23].

Other earphones and artificial ears are used in other countries. International

Organization for Standardization

Recommendation R389, Acoustics Standard

Reference Zero for. the Calibration of

Audiometers, expresses threshold of hearing

or the reference zero of the audiometer in

terms of five national standard

earphone-coupler combinations and their sets of reference equivalent sound pressure

levels, made equivalent by a ring-around

loudness balancing suggested by NBS [22].

These data, defining the reference zero

or threshold of hearing, are then

subsequently used to provide quantitative

measures of hearing impairment. Thus the

data are implicitly used whenever an audiometric examination is conducted.

Explicit use of the data is principally

confined to the members of standards

committees and to the manufacturers of

audiometric equipment.

The Acoustical and Insulating Materials

Association, a national trade organization

of manufacturers of a wide range of

acoustical and insulating materials,

annually publishes a bulletin containing

performance data on architectural acoustical

materials. These commercial data describe

the acoustical properties of currently

available material. These bulletins contain

tabulations of data including sound

absorption coefficients and sound

transmission class information. These

reference data are intended for use in the

practice of architectural acoustics and

noise control engineering, and derive from

tests conducted in independent testing

laboratories and in manufacturer's

laboratories

.

2.2.4. Reference Materials

There are very few identifiable

reference acoustical materials. This was

not always the case, and there have been, at various times, various suggestions for the

use of acoustical reference materials. Many

people are aware of things such as the use

of tuning forks or pitch (frequency)

standards, which of course to this day

remain relatively common in music.

One of the more interesting uses of

"reference materials" in architectural

acoustics was made during the researches of

W. C. Sabine [24]. Sabine realized that the

decay times in the lecture room at Fogg Art

Museum at Harvard University were inversely

proportional to the total acoustical

absorption, and that the total acoustical

absorption could be measured in terms of the

number of running feet of velour upholstered

seat cushions taken from nearby Sanders

Theatre. Thus, for a brief time, Sabine's

functional unit of acoustical absorption was measured in terms of the number of running

feet of seat cushions. The seat cushions

themselves were, in a crude sense, an acoustical reference material . However,

this was quite unsatisfactory and more satisfactory determinations of acoustical

absorption in terms of the dimensionless

fractional energy absorption were soon developed. The principal reason that

23
reference materials are not used in

acoustical measurements is that the

acoustical properties of materials are related to atmospheric properties such as humidity and temperature, and to other

physical parameters which are often not well

controlled. Because of this dependence upon

other physical phenomena, most of the

measurement procedures have not evolved so

as to require reliance upon the acoustical

properties of reference materials, an exception being the case of ultrasonic

non-destructive testing, as discussed in

Section 2.2.2.1.

2.2.5. Science and People

Acoustics has traditionally been a discipline in which the major contributions

have been provided by physicists and

mathematicians. Early in the twentieth

century, however, the technological

developments in the field of

electroacoustics and electronics rapidly led

to the expansion of the discipline to include important contributions from the

fields of electrical engineering. The

development of physiological acoustics,

psychoacoustics , and social sciences such as audiology are important related disciplines.

The recent growth of noise control

technology has led to the inclusion of such

disciplines as mechanical engineering,

engineering mechanics and aerospace

engineering. Thus the scope of acoustics

has become more in-terdiscipl inary than at any previous time. However, this is but one more manifestation of the central ity of the

phenomena of sound to our culture.

Every person who performs an acoustical

measurement is a participant in the National

Measurement System. Yet, there has been

relatively little awareness on the part of

acousticians of the desirability of explicit

understanding of the structure of such a system. Without such an understanding, the

participants cannot identify other

individual or institutional participants or user groups, and cannot effectively interact

with the system to improve their measurement

processes or operations.

In retrospect, it seems probable that

this neglect of awareness of the structure

of the National Measurement System has

contributed to the proliferation of

inconsistent, inaccurate, and imprecise

measurement methodologies in acoustics. An increasing awareness of the necessity for

national and international consistency and

for the relevant undergirding scientific

research on the part of participants in the

National Measurement System may result in

the improvement of measurement standards.

This increased awareness may be brought

about by studies of the structure of the

system itself. One of the objectives of

this report is to contribute to such an increased awareness.

The principal relevant professional

society in the United States is the

Acoustical Society of America (ASA) which is

a member society of the American Institute

of Physics (AIP). Other relevant important

professional societies include the:

... Audio Engineering Society (AES)

... Institute of Noise Control

Engineering (INCE)

... Institute of Electrical and

Electronic Engineers (IEEE)

... American Society of Mechanical

Engineers (ASME)

There are three types of publications

which serve to disseminate knowledge in this

discipline, exclusive of corporate or governmental contractor's reports. These

categories are Journals, Special Interest

Magazines, and News Letters. Several of the more prominent of these publications are presented in the following list:

Journal

s

Acustica [German]

IEEE Transactions on Audio and

Electroacoustics

IEEE Transactions on Ultrasonics

Journal of Applied Acoustics

[British]

Journal of the Acoustical Society of

America

Journal of the Audio Engineering

Society

Journal of Noise Control Engineering

Journal of Sound and Vibration

[British]

Soviet Physics - Acoustics

[Russian/English Translation]

Special Interest Magazines

Noise News

Sound and Vibration

News Letters

Noise Control Report

Noise Regulation Reporter

In recognition of the interdisciplinary

24
nature of acoustics, graduate university

curricula have been developed to provide the

interdisciplinary preparation required for

contemporary acousticians. These curricula

provide programs of study including course

work in Physics, Applied or Engineering

Mathematics, Engineering Mechanics and/or

Mechanical Engineering, Electrical

Engineering, and Computer Science.

Interdisciplinary programs directed toward

the training of Clinical Audiologists have

also evolved. The Acoustical Society of

America has a committee to study Education

in Acoustics, and the results of their

studies document available graduate

education in acoustics, and are to be found

in the literature [25].

The number of institutions having

graduate programs directed toward a degree

in acoustics is relatively small, although a significantly larger number of institutions

offer undergraduate or isolated graduate

courses in acoustics within the framework of

curricula in the related disciplines.

Graduate level education in acoustics is concentrated principally at:

Catholic University

Massachusetts Institute of Technology

North Carolina State University

Pennsylvania State University

Purdue University

University of Houston

University of Pittsburgh

University of Texas ^Austin)

By virtue of contact with ongoing

research programs at several of these

universities NBS is fortunate to have direct

contact or interactions with all of the

above institutions except the University of

Pittsburgh.

In addition, faculty members of the

following institutions serve or have served

on the ad hoc Advisory Panel on Acoustics:

Columbia University

George Washington University

Pennsylvania State University

University of Houston

University of Rochester

2.3. Realized Measurement Capabilities

2.3.1. General Patterns

The motivating factor for many

acoustical measurements is often tied to some subjective (e.g., noisiness, annoyance,

etc.) reaction of people toward a noise

source. Many difficulties exist in

developing reliable algorithms to predict

human response to noise from physical

measurements of sound, and the discrepancies

among the data collection and processing

measurement methodologies and between the

various predictions of human response are often large. Because the subjective

response to noise cannot be accurately

predicted, appreciable measurement

inaccuracies and imprecision have often been

tolerated in the required physical

measurements of noise.

Loudness judgements may be taken as a specific example. (Loudness, in this case,

can be defined as a listener's perception of

the intensity of a sound or noise.) In psychophysical experiments on loudness,

subjects are often requested to judge when

one sound is equal in loudness to another.

The standard deviations of equal loudness

judgements made by a group of 20 to 30

people will typically range from 4 to 12 dB.

Furthermore, when different laboratories

repeat the same experiment employing

slightly different conditions (e.g., free

field vs. earphones, method of adjustment

vs. constant stimuli, etc.), differences in

the mean equal loudness judgements vary from

10 to 20 dB in many cases.

Furthermore, there exists the problem of

which method should be used. For example,

Corliss and Winzer at the National Bureau of

Standards applied several algorithms for

computing loudness to the same sounds [26].

The different loudness scales yielded

answers that were discrepant by as much as 9 dB, and discrepancies among any of the

algorithms and the actual judgement of a jury of subjects reached 13 dB. Thus, not

only do the various psychoacoustic scales

disagree among themselves, but they may all

be at still greater variance with the actual

reactions of people.

The accuracy and precision required for

important acoustical measurements and for

the associated instrumentation are somewhat

more stringent; yet, there is a need for

appreciable improvements. For example, the

25
90 95 100 105 110 A WEIGHTEO SOUND LEVEL. dB re 20

fj. Pa

115

Figure 5. Results for several commercial

noise exposure meters tested in

a random incidence.

procedure for calibrating audiometers

permits ambiguities in tolerance limits.

The present American National Standards

Institute standards [11,27] allow an audiometer with an error of 11.5 dB at 8000

Hz to be calibrated as being within the

allowed 5 dB tolerance. This anomaly is due

to the cumulative calibration error effects

allowed by the standard. Obviously,

tightening of the tolerance for audiometer

calibration equipment is desirable.

In general there have been no measurement or instrument standards which

spell out accuracy and precision

requirements for environmental noise

monitoring. For example, in the case of

integrating sound level meters, the lack of

applicable performance standards and the

competition among different manufacturers to produce low-cost, compact instruments has

resulted in some equipment that exhibits

very poor performance. Recent NBS tests

[28] on a number of commercial portable

exposure meters intended for occupational

noise monitoring yielded the results shown

in figure 5. The quantity being measured

was the percentage of allowable noise

exposure. The errors are relative to 100

percent of allowable exposure. Plus or

minus 5 to 10 percent would be considered

good performance. Based on this criterion,

of the twelve devices tested, only three

passed this particular test.

. In terms of accuracy, American National

Standard SI. 4-1971 describes three basic

types of sound level meters. Accuracy

requirements are given in terms of allowable

error tolerances relative to the specified

overall response of the instrument. The

tolerances, as indicated, vary from +1.0

decibel for the mid-frequency range for the

Type 1 meter, to +7.5, -«> decibels at 10 kHz

for the least precise type, Type 3.

Manufacturers of sound level meters

usually claim compliance with American

National Standard SI. 4. Purchasers of

meters are likely to require such compliance

or else use SI. 4 as a basis for preparing

specifications. It is likely that many

manufacturers do not have the proper

facilities to determine compliance. It should be noted that "type testing" of

meters is a substantial job and even with a semi -automated, dedicated facility, would

still probably cost on the order of $500 per

meter. Because of the intricacies of

compliance testing sound level meters it is

doubtful whether most of the sound level

meter manufacturers are currently using

thorough and extensive techniques.

Unfortunately, much of the value of

American National Standard SI. 4-1971 is

diluted by the absence of a standard on aaoustiaal aalibration procedures for sound

level meters. Performing an adequate

calibration requires that the detailed

procedures be carried out by highly skilled

personnel

.

The highest degree of acoustical

measurement accuracy is usually to be found

in the microphone calibration process. This

is a consequence largely of the tight

control of the variable factors in the

process, concern for attention to details

and good measurement practices, and caution

in the interpretation of experimental data.

The estimated accuracy of NBS pressure

reciprocity calibration is 0.1 decibel. The

accuracy will, typically, be worse than this

for random incidence conditions since it is

difficult to produce a sound field which is spatially uniform. Nonetheless, this degree

of accuracy is an important objective when

legal limits are involved such as compliance

with OSHA regulations or aircraft noise

certification. Unfortunately, inaccuracies

26
in level of typically 1.0 dB are not uncommon for acoustical measurements.

Many companies and institutions maintain

sound measurement standards laboratories of

their own. The size and extent of each is

related to the companies' activities. Some

of the laboratories perform reciprocity

calibrations with special,

commercially-available equipment, but such

equipment does not yield as accurate a calibration as is available from NBS. A

small number of laboratories have

calibration equipment modeled after NBS and

obtain accuracies approaching ours for

certain types of measurements.

The calibration provided by a microphone

manufacturer is usually accurate. However,

such is not always the case. For example,

for one brand of microphone, a calibration

chart is included which is based on the use

of non-standard calibration techniques. For one-inch diameter microphones, differences

from the NBS calibration of as much as 1.5

decibels exist in the neighborhood of the

microphone resonance. A short paper [29]

has been published describing the

differences in calibration and the reasons

for them.

Despite the fact that inaccuracies found

in acoustical measurements can be

appreciable, as the preceding ' has indicated,

the inaccuracy to be found in the technology

of ultrasonic non-destructive testing is

believed to be even more appreciable. The

National Bureau of Standards is currently

directing attention to this technology, and

is studying the response of reference blocks

to acoustic signals. Realizing that these

reference blocks are used for the purpose of

system calibration, data were obtained upon

several sets of commercially available

distance-amplitude blocks. The ultrasonic

response data are shown in figure 6, and

indicate that although the response

amplitude generally drops off significantly

with increasing metal thickness, for one set

of blocks there was an anomalous response,

amounting to differences as large as 800%.

This is probably due to uncontrolled

metallurgical properties of the material.

Differences of this order of magnitude not

only render this specific set of blocks

unusable, but would, if representative of

those generally used make the use of

ultrasonics as a means of non-destructive

testing and evaluation a source of inequity

in trade. Manufacturers cannot rely upon

the data obtained from such an empirical

technology to develop product standards.

TEST FREQ -5MH

SEARCH UNIT -.375 in DIA QUARTZ

WATER DISTANCE -3.5 in

0 1 2 3 4 5 6 METAL DISTANCE, in.

Figure 6. Ultrasonic response amplitude

data for distance - amplitude

reference blocks.

The current NBS program in ultrasonic

non-destructive testing and evaluation is

leading to the discovery of the causes and

elimination of the variability of the

reference blocks as a major source of error

in ultrasonic measurement systems.

2.3.2. Dependence Upon Environmental

Factors

There are two principal active concerns

about the dependence of acoustical

measurement instrumentation and measurement

methodologies upon environmental factors.

These concern the stability of the

instrumentation calibration over long

periods of time and under varying

environmental conditions, and the dependence

of the data upon poorly characterized

environmental facters.

In obtaining long term measures of such

factors as community noise, the temperature

dependence of the instrumentation may be an important factor. Recent National Bureau of

27
standards services performed to evaluate

noise monitoring systems for the Department

of Housing and Urban Development have

disclosed an unanticipated significant

dependence of microphone sensitivity upon

temperature which will require design

changes. An additional investigation is currently in progress to evaluate the

dependence of microphone sensitivity upon

temperature and humidity for condenser,

electret and ceramic microphones.

Current attention directed to the

quantitative characterization of noise

emissions from conrnon noise sources such as automobiles, trucks, portable air

compressors, etc., has disclosed the

necessity for accurate characterization of

such factors as the acoustic impedance at several angles of incidence (including

grazing) of concrete, macadam, or grass

covered surfaces. Recognition, in fact, of

the impossibility of reliable

characterization of the acoustic properties

of grass has led to the use of synthetic

turf in a measurement methodology directed

toward measurement of the noise emission of

small engine powered equipment (e.g., lawn

mowers, snowmobiles, etc.) [30].

2.3.3. Adequacy Versus Needs

There are a large number of important

acoustical measurement standards related to numerous special purpose measurement

procedures

.

While these standards may have been

adequate in the pabL, they may not be

adequate for future needs. Due to the

economic and/or legal implications of

present and pending noise control

legislation, the degree of accuracy and

precision which can be anticipated with

employment of a specific measurement

methodology is now receiving increased

attention. For standards and regulations to be effective and reasonable uncertainties in

the measurement methods should, be as small

as practicable. Compliance cannot be

determined unless the measured levels are lower than the specified limit by an amount

at lec'ist equal to a realistic estimate of

the measurement uncertainty. Uniformity of

enforcement — i.e., consistency among

measurements by different officials -- is

only possible if the tolerance between the

legal limit and the enforcement limit is set

at the measurement uncertainty

representative of typical field measurement

conditions.

The largest uncertainty likely for

measurements by the least competent

official, using the most inaccurate or imprecise equipment allowable, under the

least favorable test conditions, must be

considered in the process of setting the

relation between the legal limit and the

enforcement limit. If this measurement

uncertainty is large, the enforcement

agency's problems are increased. If the

enforcement level is set above the legal

limit,- it appears that the agency is not

enforcing the desired noise abatement level.

If the enforcement level is set below the

legal limit, manufacturer's incur increased

compliance costs. Thus, the situation must

be optimized, so that although a certain

degree of measurement certainty is

sacrificed, the cost of compliance is kept

at a reasonable level

.

The question might well be raised as to whether close measurement tolerances —

attainable by careful control of

environment, operating procedures, and

measurement procedure -- are justified in

view of the uncertainties in the application

of the resultant noise rating to predict

in-service noise levels and its resultant

effects. First, the total error in

prediction is the sum of the errors in

ratingJ in predicting in service levels and

in predicting the resultant effects.

Reducing the rating error thus reduces the

total error; however, it would be

economically wasteful to insist upon high

levels of accuracy and precision for rating

measurements if the errors in predicting

in-service levels and resultant effects are relatively gross and difficult to control.

Second, application errors and, to some extent, effect-prediction errors tend to average out from one application to another;

systematic errors are repetitive. Third,

when noise ratings are used to compare the

performance of competitive products,

difficulties in enforcement, inequities in

trade and excessive costs may be incurred.

Because the increase in concern over noise and attention given to the accuracy

and precision of determining noise emission

are very recent developments, essentially no one -- including NBS — has, as yet,

adequately evaluated the uncertainties

associated with various techniques for

measuring noise emission. NBS is currently

responding to this need to evaluate

measurement uncertainty by conducting a project in the area of transportation noise.

Because of increasing concern with the

impact of transportation noise on

28
coirniunities , there has been an increase in

the number of motor vehicle noise

regulations at all levels of government. As regulations become more widespread, the

accuracy and precision of vehicle noise

measurements become more critical since each

uncertainty in the measurement requires a corresponding increase in the margin that

manufacturers must allow between the

regulated noise limit and vehicle design

levels. Although considerable uniformity

has been achieved by existing voluntary

standards, there remain significant

variations between noise measurements made

at different sites or at different times on the same site. These variations are attributable to differences in the

environment, including site and

meterological influences. Thus, there is a need for systematic investigation of the

various environmental and test site effects

on noise generation, radiation and/or

propagation. Although it may not be

feasible to determine "correction factors"

for environmental effects, it is fully

expected that the data obtained from this

experiment will reveal the magnitude of

variations in the measurement and provide a broad enough information base. for study of

the underlying physical mechanisms [31].

2.4. Dissemination and Enforcement Network

2.4.1. Central Standards Authorities

Because the standards system in this

nation is voluntary, there is no central

standards authority, as such, and NBS has no specific legal "authority" in the

dissemination of acoustical measurement

standards, in contrast to the situation in some other nations. NBS staff members serve active roles in the professional society and

voluntary concensus standards groups, but as an institution NBS does not serve to disseminate or enforce standards for

acoustical measurements. The scope of

institutional involvement is principally

limited to the individual participation of

NBS staff members within the existing

voluntary concensus standards-writing

groups, to the critical review of existing

standards and scientific contributions

toward the evolution of improved measurement

standards, and to the provision of advisory

information covering measurement

methodologies to other Federal agencies.

State and local governments, and to the

general public.

2.4.2. State and Local Offices of Weights

and Measures

At the present time no state or local

offices of weights and measures are known to

be concerned with the subject of acoustics

or acoustical measurements. This situation

is apt to change as our society becomes more concerned with the measurement of noise

emissions, but these considerations are relatively recent elements in our society,

and this institutional element of the

standards and enforcement network has not

yet become active in this field.

2.4.3. Standards and Testing Laboratories

and Services

2.4.3.1. Types of Acoustical Standards and

Testing Laboratories

Private (non-governmental) acoustical

standards and testing laboratories exist as both corporate industrial and independent

laboratories. The industrial laboratories

largely exist to serve the needs for

acoustical measurements of corporate

research and/or design engineering groups.

The motivation for these measurements is

frequently related to noise control

engineering, product improvement, or product

quality control considerations. The

independent laboratories provide testing and

measurement services to industry wide

groups, to noise control consultants,

industrial clients who do not maintain their

own testing laboratories, and to municipal,

state and Federal governmental units.

Governmental laboratories provide

limited acoustical testing and measurement

services to support review of measurement

procedures or procurement specifications or

for the furtherance of basic research on acoustical phenomena.

Table 4 presents a tabulation of known

acoustical laboratories, together with

information pertaining to the relevant

acoustical measurement capabilities.

2.4.3.2. Functions Performed

The industrial research and independent

testing laboratories are principally

concerned with determining the following

types of information:

... mechanisms of aerodynamic noise

emissions

29
Table 4. Existing acoustical laboratories.

Type of Test Acoustical Measurement

Facilities Capabilities

Industrial Laboratories:

Armstrong Cork Company Barry Controls Carrier Corporation

Celotex Corporation

Conwed Corp. (formerly Wood Conversion Co.)

Donitar LTD. , Quebec

International Business Machines (IBM) Jim Wal ter Corp. Johns-Manville Research and Engineering Center Lockheed Missile and Space

Lord Manufacturing Company McDonald Douglas Corporation

Minnesota Mining and Manufacturing Co. (3M) National Gypsum Company

Noise Unlimited,' Inc. Ohio Research Corp., Donn Products, Inc. Odgen Technology Laboratories, Inc. Owens-Corning Fiberglas Corp. Pittsburgh Corning

United Acoustic Consultants

United States Gypsum Company Vibro-Acoustics Ltd. A Douglas Engineering Co. York, Borg-Warner

Independent Laboratories:

Cedar Knolls Acoustical Laboratories

Geiger & Hamme, Inc. Intest (International Acoustical Testing Labs) Kodaras Acoustical Laboratories

Ling Temco Vought, Inc., Research Center Riverbank Acoustical Laboratories of I I T R I Wyle Laboratories

Government Laboratories:

NASA Langley Research

NBS Laboratories at Gaithersburg

National Research CounciT of Canada- Wright Patterson Air Force Base

a,b,d

a,c,

a

a

aa,b,d

a ,c a,b

aa,b,c

a,b

a ,b,c

aa,b,d

a ,c a,b

aa,b,d,c

ac,e

a,e

a,b

a

a,b,d,g,i

,

a ,b,Q a,b,c,d,g

a ,b,d,g,j

a ,g ,1 a ,b,d,g

a ,b ,c ,d ,g

,

a ,c ,g

a ,c

a ,b ,d,g

a ,b,c,g,h,i

1 ,2,4,5,10,13

4,5

4,5 4,5

4,5

1 ,2,4,5 4,5,10

1 ,4,5 4,5

1 ,4,5

1 ,4,5

1 ,4,5 4,5

1 ,2,4,5 4,5

1 ,4,5 4,5

1 ,2,4 ,r,10,13

4,5 5,10

1 ,2,4,5

1 ,4,5 4,5

1 ,2,3,4,5,7,9,10,13

1 ,2,3,4,5,10,13

1 ,2,3,4,5,;;, 10

1 , 2, 3, 4, 5, 7, H, 9, 10,1 3 4,5,11

1 ,2,3,4,5,9,10

1 ,2,3,4,5

4,5,10 4,5,6,10,12,13,14,15

1 ,2, 3, 4,!), P., 10,1 3,14,15

1 ,4,5,6,10,11

Academic Laboratories: .

Illinois Inst, of Technology, Research Inst. a,c,g,i

Pennsylvania State University a,c,g,h,j

Purdue University a,c,g,j

University of California • ci,b University of California-, Los Angeles a,b,c,i University of Houston c University of Texas • a,c

4,5,11 4,5,6,7,8,11,12,13,1^,15

4,5,7,9

1 ,4,5

1 ,4,5,11

54,5

Type of test facilities in existing acoustical laboratories in the U. S.:

Evaluation of existing acoustical laboratories in this country

is based on the nature of their specialized facilities. Those

facilities that are needed for the building acoustics portions

of the sound, auditior. and noise abatement program may be categorized as follows:

a. Reverberation chamber

b. Transmission chamber

c. Anechoic chamber

Impact testing chamber

Field test simulation spaces in an actual building

Plumbing sound facilities Machinery sound facilities Audition chamber with observation room Acoustical scale model test facilities

Air handling systems and terminations sound, test facilities

d.

e.

f

.

gh.

ij .

Acoustical Measurement and Service capabilities of the existing

acoustical laboratories in the U. S.:

1. Airborne sound inslatinn of building partitions

2. Impact sound insulation of floor-ceiling assemblies

3. Airborne sound insulation of exterior walls fi roofs

4. Sound absorption of acousti:al ^ arc'ii tectural materials

5. Sound power out|)ut of small noise sources, machinery C household appliances

6. Psychoacoustics h loudness

7. Heating, ventilating f< air-conditioning system noise

8. Structure-borne noise 1 vibration of building structures

9. Sound attenuation of silencers f> mufflers

10. Flow resistance f< acoustical impedance of sound absorbing materials

11. Acoustical scale modeling

12. Calibration of microphones, sound "'cvrl meters, noise dosimeters

13. Technical consultation re acoustical problems, noise abatement *i control

14. Advisory services coordinating government R private

standards re acoustics, noise criteria f- abatement

15. International domestic standardization activities.

30
... noise emissions of business

machinery

... noise emissions of heating,

ventilating and air conditioning

systems

... noise abatement properties of

mufflers and duct silencers

... acoustic transmission properties of

building systems

... acoustical properties of ceiling and

wall covering materials and

constructions

... acoustic absorption of fibrous

materials

... dynamic mechanical and acoustical

properties of floor coverings and

constructions

... structural vibration control and

structure-borne sound abatement

systems

.

Governmental acoustical laboratories are net only fewer in number, but are also

relatively more limited in scope than the

industrial or independent testing

laboratori es

.

The Institute of Environmental Sciences

has recently initiated a survey of

approximately 200 laboratories to determine

more detailed information on the facilities

and services offered by these laboratories.

The preliminary results of the survey are to be published in the March/April 1975

Institute of Environmental Testing Journal,

with more detailed information to be

released in late 1975 as an lES Report.

Although this survey concerns itself in part

with consideration of the environmental

testing aspects of acoustical measurements,

i.e., noise induced structural fatigue, the

results of this study should be of

considerable general interest.

2.4.3.3. Detailed Description of a Representative Industrial Laboratory

A wel 1 -equipped representative

industrial laboratory which was visited to obtain information for the purposes of this

report had the following major facilities:

3 ... 200 m anechoic chamber with

removable floor wedges to convert

the facility for use as a "semi -anechoic" facility.

... 200 m reverberation room with

removable panel, coupling into an adjacent

3 ... 100 m reverberation room

... real time analyzer, coupled into a digital computer for digital signal

process! ng

... instrumentation to enable the

measurement of sound power emissions

in free-field, free-field over reflecting plane, and reverberation

room environments, under digital

computer control

... instrumentation for the measurement

of acoustic absorption coefficients.

The technical staff of this laboratory

consists of three full-time engineers, two technicians, and secretarial help. The

principal service offered by this laboratory

is product research and development and

implementation of product noise control measures. The facilities had been

specifically constructed on a remote site at

a corporate research facility primarily to enable the measurement of product noise

emissions and for research purposes.

Another facility visited by NBS

personnel was an independent testing

laboratory with facilities specifically

devised to enable the measurement of the

noise emissions of air conditioning

equipment. Because these measurements

require that the equipment be operated under

load, this laboratory has extensive

facilities to control the temperature and

humidity over wide ranges on both sides of

the air-conditioning equipment. In addition, the reverberation room facilities

were equipped for the measurement of the

impact noise properties of floor-ceiling

assemblies. The clients of independent

laboratories such as this include the

manufacturers of commercial grade carpeting

and resilient floor coverings, manufacturers

of heating, ventilating, and air

conditioning equipment, and trade

organizations

.

2.4.3.4. Interrelationships

The most common inter-relationship of

these laboratories is to be found in the common professional affiliations of the

staff members. The senior staff members

generally serve on the committees of the

31
voluntary concensus standards groups such as the American Society for Testing and

Materials, American Society of Heating,

Refrigerating and Air Conditioning

Engineers, etc. In so doing they strive to represent the desires of their employers as well, of course, as to serve their own concern for scientific factual objectivity.

However, in their desire to represent the

interests of their employers or firms, there

is the possibility that they will tend to promote the acceptance or continued

acceptance of an outmoded facility or test

method.

Generally speaking, the specifications

of voluntary test standards are written so that most of the existing laboratories can meet them. However, detailed instructions

and specifications for the construction of new laboratories are given in most

standards, with the objective of improving

future measurement accuracy within and among

laboratories. Some facilities are too small, not equipped for accurate

measurements, and are obsolete by

present-day standards. In a few instances,

laboratories have developed and use their

own methods of test in preference to the

recognized standards because they feel the

latter are unrealistic or misleading —

particularly with respect to airborne and

impact sound insulation measurements.

As can be seen in table 4, there is a limited number of architectural acoustic

test facilities. It should be noted that

only twelve of the laboratories listed have

facilities for conducting both airborne and

impact sound insulation measurements of wall

and floor constructions. Jen laboratories

have facilities fo>^ measurements of only

airborne sound insulation of wall

constructions. These statistics reflect not

only the expensive nature of these test

facilities, but also the fact that the

measurement processes are under the

direction of a relatively small number of

engineers.

2.4.4. Regulatory Agencies

The principal -involvement of regulatory

agencies with acoustics, and more specifically, with acoustical .measurements

is Concerned with the regulation of

environmental noise. Much of the material

presented in Section 2.4.4. is drawn from an appendix entitled "Environmental Noise

Regulatory Structure", by Dr. Louis Mayo

and Mr, Robert C. Ware, in the, report 'of the

Conference on Acoustics and Societal

Problems [32]. Extensive quotations are used because of the apt and succinct manner

in which the authors have described the

structure. Additional material is used to describe the detailed structure of municipal

noise regulatory efforts, and is drawn from

the work of Bragdon [33].

2.4.4.1. Local Regulatory Efforts

"Most noise regulation has traditionally

been at the local level. It has suffered

from the low priority given to noise control

by the police forces and the community as a whole. Cities have not had the technical

knowledge or the financial resources with

which to combat noise effectively.

"Much local noise regulation is in the

form of general laws prohibiting loud and

unnecessary noise. The most popular type is

that patterned after the Model Ordinance

Prohibiting Unnecessary Noise of the

National Institute of Municipal Law Officers

(NIMLO) (1948). The NIMLO ordinance

prohibits all loud and unreasonable noise

and specifies certain prohibited noises such

as those of loud animals and badly loaded

cars and trucks.

"More cities are developing programs to cope with excessive noise. Some have

established noise abatement offices with

special teams whose duty is to monitor noise

around the city. City noise laws are becoming more sophisticated, substituting

noise level limits for the former subjective

standards. These laws also provide for

tougher standards over time. The success of

city anti -noise programs will depend upon

enforcement of these new laws.

Unfortunately, there is a lack of trained

personnel to handle noise law enforcement.

Enforcement also provides strains on the

already over-burdened budgets of many of the

nation's cities." [32]

The compilation shown in table 5 lists

440 municipalities. These ordinances now represent a comt^ined population in excess of

62 million people. "There is a continuing

interest to enact legislation with

quantitative noise emission requirements.

In many cities ordinances previously

containing non- quantitative or general

nuisance provisions have been replaced with

quantitative noise emission requirements.

"The ordinances are organized by

category including: Nuisance, Zoning (Land

Use), Vehicle, Aircraft, and Building

Regulations containing acoustical criteria

32
Table 5. Municipal noise- ordinances: 1976

Naisance Zonini Vehicle

Regulition includes acoustical criteria 157 219 138

Regulition does not include acoustical criteria 410 22 115 — Nofegulltlon 85 411 399

1970 = = J*lpsi )«ri«4lctie> Paiiriitioii £S£££ s3m

Anniston 31.533 Birmingham 300.910 -------- Irondale 3.166 - - - - -

-

Madison 3.086 -

Mobile 190.026 Montgomery 133.386 ------- -

UASU

Anchorage 48,081

Juneau 6.050 -------- ((etchikan 6,994 --------

AHZOM

flagstaff 26.177 z - - - - - -

Pho«ni« : 581,562

Scottsdale 67.823 Tempe 62,907

Tucson 262,933

AMANSAS

Utile Rxk 132.125 -Q - - - - - - -

Pine Bluff 57.389. q-------

CAllFOmiA

Alhambra 62,125 - - - - - -

-

Amador 156 - - - - - ~

-

Anaheim 166,704

Arcadia 43 867 b------- Belmont 23,667 b------- Berkeley 116 716

Beverly Hills 33 415 Buena Park 63,646 Burbank 88,871 = n- -Z- Buflingame 27,320

Caprtola 7,175 - - - - - -

-

Ceres 8.675 3-----^- Chico 19,580 B-----B- Commerce 10.662 _b------ Cosla Mesa 72,660

Cotati 2,081 Cudahy 17,040 - z- -- -- -

Culver City 37.600 b------- Cuperlino 18.216

Del Mar 4.475 3-a---n- DelReyOaks 1.-830 r:-G---_i- Downey 88.442

Duarte 15, 100 - - - - ^

-

El Caion 52 273 - b- -- -- -

ElEscalon.. Seiundo 15,620

1,834 3---aFoster City IS, 550 b------- Fountain Valley 31,826 BB----B- fresno 165,972

Fremont 100.869 - bD----- Gardena 41.021

Garden Grove 121,371 -

Glendale 132 752

Glendora 31,349

Gustine 3,546

Hayv-ard 93.058 Hemet 12.252 zm------ Hermosa Beach 17.412

Huntington Beach 17,412

Huntington Park 33.744 r; - -- -- --

Inglewood 89.985 yH--HB-- Laguna Beach 15.100 -

Lakewood 82.973 -

La Mesa 44,509 - - - - - - -

La Puente 31,450 B----- _-

Larkspur 10,487

Lo<ji 28.691 - B - -B--- Lomita 19.784 bB------ Long Beach 358.633 -

Los Altos Hills 6.853 -

Los Angeles 2.816.061 =

Los Banos 9.188 -

Lynwood 43.353 - _i - - - - -

Manteca

Menlo

MilpitasPark 26,82632,400

13,845 _b------ z------- - -- -- -- -

Modesto

Monrovia 75,80030.015 B------- - -- -- -- b

Monterey 26,302 b ------ -

Newark 27,153 - - - - - -

Newport Beach 49,422

Norwalk 91,827 - -- -- -- -

Novato 31,006

Oakland 361.561 zm------

Recreational

Vehicle Railroad Aircraft Conitruction Building

50 16 26 44 26

20 9 9 71 9 582 627 617 537 617

1970 I I i ? I 1

Juriidiction Population z S » x S 5

"Orange 77.365

• Pacifica 36,020 z------- Palmdale 10,600 - -- z- -- -

Palo Alto 55,965 bB------ Pasadena 112.951 =

Perns 5,100 - - - - - - -

Petaluma 31.150 - b- -- -- -

Placentia 30.200 -

Pleasant Hill 27.150

Red Bluff 7.676 - -- -- -- -

Redding 16,659 Redondo Beach 64.000 - -

Richmond 79,043 -

Rocklin 3,039 - b- -- -- -

Roseville 19,950

Ross 2,742 Sacramento 254.413

Salinas 58.893 J - Z - - -

-

San Anselmo 13.031 San Bernardino 104.251 Z------- San Bruno 38.750 - - - - - -

San Carlos 26.053 - b- -- -- -

San Clemente 17.063 San Diego 696,769 San Dimas , - 17,125 San Francisco 715.674 &

San Jose 445.779 ----- : - -

San Juan -Capistrano 11.000 b------- San Leandro 68.698 z------- San Marcos 3.896 San Mateo , 78.991 ~m-----m San Rafael 38.977 z------- Santa Barbara 70.215

Santa Clara 87.717 Z----B-B Santa Fe Springs 14.750 _b------ Santa Maria 32 749 _ b ----- -

• Santa Monica 88, 289 ----- _ -

Santa Rosa 50,006

Saratoga

Sausalito 29.9326.158 b------- - Z - - - - -

Simi SouthValley

El Monte

59.832

13.442 b------- b - -- -- --

South SouthGate Pasadena56.909

22.629 b------- b - - - -

Sunnyvale 95.408 ZB------ Tracy 14.724 - B- -- -- B

Torrance 134.584 - - - Z' -

Valleio

Victorville 74.80010.845 Zb------- - - - - - - -

Walnut Creek 48.850 Z - - - - - fj -

West Covina 74,000 b - - - - - -

Whittier 73,400 z ------ -

COLORADO

Arvada 49,083

Aspen 2.404

Aurora 74.974 _b------ Boulder 66.870 Z-mm---- Colorado Springs 135.060

Denver 514.678

Dillon 182 - - c - - - - -

Englewood 33.695 Z - - - - -

Fort Collins 43.337 Lakewood 92.787

Littleton 26.466 - - -

Wheat Ridge 29.795 --------

CONNECTICUT

Berlin 14.149 - - - - - -

Bridgeport 156.542

Farmington 14.390 - - - - -

Hartford 158.017 New Haven 137.707

Stonington 15.590 - - - - - -

Westport 27,414 - b- -- -- -

DELAWARE

Wilmington 80.386 Z - - - - -

DISTRICT OF COLUMBIA

District of Columbia - 756,510

FLORIDA

Anna

AtlantisMaria 1,400 844 Z------- - - - - - -

Bal Harbor Village 2.104 :]------- Bay Harbor 4.723 Z - - - - - - -

Bay Lake 18 - - - - - -

-

Boca Raton 28.506 B-----Z- Cape Canaveral 5.131 bB------

33
iurlidlctlon Populitlon

Clearwatet 52,074

Cocoa Beach 11,555

Coral Gables 42,494

Oania 9,819

Daytona Beach 47,682

Oeertield Beach 19,577- Deland 11,641

Delray Beach 19,915 Eigewatet 3,348

fort Lauderdale 139,590

fort Myers 32,563

Fort Pierce 31,752

Gainesville 64,510

Hallandalc 32,292

Hialeah 102,452

Hialeah Gardens 1,076

Hollywood 106,873 Homestead 19,022

Indian Shores 891

Jacksonville 528,865

Lake Buena Vista • 22

Lakeland 45,091

Lake Park 7,927

Lake Worth , 25,934

Lauderdale t)y the Sea , , . 2,941 Lighthouse Point 11,760 Madiera 4,769

Margate 17,153 MeltMurne 40,236 Miami 334,859

Miami Beach ,,. 89,741 Miami Shores 9,541 Miami Springs . , 13.384 Miramar 27,132

North Lauderdale 5.648

North Miami 42,970

North Palm Beach 12,056 Oakland Park 19,700 Oldsmar 2,090 Opa Locka 12,924

Orlando 97,565

Plantation 29.512

Plant City 15.781

Pinellas Park 28.526 Palm Beach Gardens 8.315 Pompano Beach 38.544

Lauderdale Beach 2,941

Riviera Beach 21,401

Redington Shores 2, 111

St Petersburg 216,232

Sarasota 44,538

South Daytona 7,825

Surf side 3,649

Tallahassee ' 72.586 Tampa ,. 298.740

Tavares 3.673

Treasure Island 6,878

Vero Beach 14,211

Virginia Gardens 2,592 West Miami 5.989 West Palm Beach 27, 132

Winter Haven 16.136 6E0RGW

Alma 3.756

Atlanta '. . . . 497.421

Camilla 4.987

Carrolton 13.520

Claxton 2,669

College Park . .• 18.203 Columbus 154.168

Cordele 10,733

Oacala 782

Oanielsville 370

Decatur 21,943

Dover 220

Flowery Branch 761

Forest Park 19,994

Griflin 22,734

Hapeville 9,567

Kingsland 1,831 Lake City 2,306

Louisville 2.691 Macon 122.423

Moultrie 14,400 Newnan 11.205. Peachtree City 793

Rincon 1.854

Riverdale 2.521 Savannah 118.349

Tyrone 136

Warner Robins 33.491 Waynesboro 5.5.10

HAWAII

Honolulu 324.871

IDAHO

Boise 74.990

Idaho Falls 35,776

Pocatello 40,036

1.1 ----- n - -------- - n» CD - -- -- --

- -- -- -- - --------

- -- -- -- -

[D - -- -- --

- -- -- -- -

-

- -- -- -- - - -- -- -- - - -- -- -- - - -- -- -- - - -- --

- -----

- - -- -- -- - --------- D------- - -- -- -- - n------- - -- -- -- - - -- -- -- - - -- -- -- -

- n - -- -- --- - -- -- -- - - -- -- -- - - -- -- -- - BB------

- -- -- -- - - -- -- -- - -------- - -- -- -- - - -- -- -- - - -- -- -- - n-------

u — - -- -- - Q-------

- - - -

-

- -- -- -- -

- --------

- -------

- - -- -- -- - D------- - -- -- -- - - -- -- -- - - -- -- -- -

- -- -- -- -

- -- -- -- - - -- -- -- - - -- -- -- - -------- - -- -- -- -

lyrtrilctloii Popylttlon

lUINOIS

Arlington Heights 64.884

Carbondale 22.816

Chicago 3.369.359

Decatur 90.397

Oes Plaines 57.239 Downers Grove 32.751

Joliet 80,378 Marengo 4,235

Moline 46.237

Northbrook 27.297

Park Ridge 42.466

Peoria 126,963

Rockford 147,370 Savanna 4,942

South Holland 12,619 Urbana 32.800

INDIANA

Evansville 138.764

Gary 175,415 Hammond 107.888

Indianapolis 745.739

Logansport 19.255

Lowell 5.822 Ogden Dunes > 982

South Bend 125.580

IOWA

Bedford 2.361 Cedar Falls 29.597

Council Bluffs 60.348

Davenport 98.469

Des Moines 7. .. 200.587 Dubuque 62.309

Pella 6.668

SiouK City 82.925

Storm Lake 8.591

Waterloo 75.533

KANSAS

Lawrence 45.598

Prairie Village 28.138

Wichita 276.534

KENTUCKY

Covington 52.535

Lexington 108,137

Louisville 361,472

Newport 25,998

LOUISIANA

Baton Rouge 165.963 New Orleans 593.471

MARYLAND

Baltimore 905.759 Cumberland 29.724

Rockville 41.564

MASSACHUSETTS

Acton 14,770

Boston 541,070

Concord 16.148

Fall .tiver 96.898

Milford 19.352 Newton 91.263

Pittsfield 57.020

Springfield 163.905

Worcester 175.572

MICHIGAN

Ann Arbor 99,797 Augusta Township 1.016

Beverly Hills .... 13.598 Birmingham 25. 170 Comstock 5.003

Dearborn 104.199

Detroit 1.512.893 Farmington 10.329

Gladwin 3.624 Grand Rapids 197.649

Harbor Springs 5.251 Kalamazoo 85.555

Meridian Township 23.817

Milford 4.699

Pontiac 85,279 Ravenna 851 Saginaw 91.849

Troy 39.419

Warren 179.250 Westland 86.749 Wyoming 56.560

MINNESOTA

Bloomington , 81.970

Brooklyn Park 13.692 Cannon Falls 2. 155 Columbia Heights 23.837 Oilman 798

Minneaoolis 434.400

34
1970

PofliitlOl Jurisdiction

1970

Populllion

Rochestef

St- Paul -

MISSISSIPPI J3OS0-

53.766 309 828

153 968 Z

HISSOMI

Bfagetcn 19.992

Gladstone . 23.422

SrandYiew 17.456

Independence 111.662

Kansas City 507.330

St Louis . 622.236

Spcingfield 120.096

Waynesvilie - . 3.376 HONTUU

Billings Great Falls Helena

Livingston Missoula NUUSU

Beatrice

Lincoln McCook Omaha

Scattsbhiff Stdner NEVAOI

Las Vegas NEWMMPSINK

Berlin Concofd Man-ies!e' NEW JEISIT

ADsecon

Asburj Part Bayonne

Belleville Bertele) Heights . .

Bhxmfield

Booflton Bordentown

Bfigantine

Burlington Camden

Cape May

Cedar Grove

Clifton Clinton

Coflnti Doi«. . . , East Grange

Elizabeth Emng

Fairlawn

GkMicestef . .'. Hackensack Hanmonton

Hanover

Harrison Hasbrouck Heights . Hawthorne HigMstWrn

Hoboken

Irvington .' Jersey City Lakewood

Linden Long Branch Margate Maywood

Mcrnstoarn Newark

Newton

North Haledon

North Wildw«xid . . .

Nutley Ocean City Orange City Passaic

Paterson Pemberton Borough

Perth Amboy

Plamfield

Pleasantville Princeton RaiMay

Ridgefield Paili . . .

Salem

Secaucus

South Amboy

S(»rti Summit

Trenton VitMland Wayne

Westfield .

s: 58: 60.091 22.730

e.883 29.497

12.787 149.518

8.285 346.929

14.507

6.258

125.787

15.256 30022

87 I'bi

6.094

16.533

72.743 34 643

13 078

52.059

9.261 4.490

6.741 11.991 102.551 4.392

15.582 82.437 1 742 258

15.039 75.471 112.654

32.831 37.975

14.707 36.008

11.464

10.700

11.811 13.651 9.173

5.431 45.380

59 743

260.545

17 874

41.409

31.774

10.576

11.087

17 662

382.417

7.297

7.614 3.914 31.913

10.575 32.566

55.124

144.824

1.576 38.79«

46.862

13.778

12.311 29.U4-

14.453

7.648 13.228 9 338

10.819 23 620

104.638

47 399

49.141 33.720 -

West Orange Wharton . . .

Wildwood ... Woodbridge . NEW MEXICO

Albucuerque

Gallup

Los Alamcs NEW YORK

Albany Auburn Binehamton . . .

Buchanan

Buffalo Canandaigua . .

Clifton Springs Corning

Cortland

Freeport Geneva Hammondsport

Hempstead - . .

Hornell Huntington . . Islip Ithaca Lake George . Lynbrook

Lyons Macedon Mamaroneck

Marion . Montour Falls . New Rochelle . New York Crty Niagara Falls Niskayuna

Ossining Penn Yan

Phelps

Rochester Smithtoum Sodus Southampton . .

Utica Watkins Glen . White Plains . .

Williamstawn . Wolcott

Wallkill Yonkers

NORTfl CAROUNA

Aberdeen . .

Asheville Aurora Belmont Benson Boone

Burlington Carolina Beach . .

Carrboro Chapel Mil Concord

Conetoe Durham

Fayetteville Forest City Franklin Fuquay-Varina . . .

Gastonia

GiltsonvjJIe Goldsboro Greensboro

Hickory High fmitt Kings Mountain . .

Kinston Kure Beach

Laurinburg Lumberton Madison

Manteo

Marion

•ilonrM Mt Pleasant New Bern Newton ... Raleigh . . Red Springs Roanoke Rapids

Rocky Mount

Roper

Salisburg Seaboard

Silver City Southern Pines . Statesville Tarboro Thomasville

43.91D 1 1. 105

4. 110

—

78,846

243,751

13.779

11.310—

115.781

34. 599

64. 123

2. 110

462. 758

10.488

—

2.058

15.972

19.621 40.374

—

16.763 l.(^

'30 ^1 1 12 144

12 601 7 692

26^226 ] 50g

23^776 4 496 1 168

—1

18 909

ssc " 53*1 75 385

/.03J.3QJ 85.615

6. 186 21.659

J. IDS

i:

£.130, cJJ 1 7 rwv) l/.UUU

—

C. / lb

50. 125

1.919

1.617 1l.Hb QJQ

204.297

—

1.592 57.681

D

620

4.814

—

2.267 8.754 35.930

—

1,663—

3.472 25.537

18.464

D

160

95.438O

53.510

7.179 2.335

3.575

—

47.143

—

2.019 26.810

—

144.076

—

20. 559—

53.204

—

8.405 22.309

—

394

—

8.859—

16.961

D

2.081 547

3.335 1 1 282

"l'l74

14.660 7.857

123.793 3.383

13.508 34.284

649

22.515

511

4.689

5.937 19.996

9.425 15.230

DD Z

35
Iiirlitlctlon

Valdese WaKe Forest . .

Walnut Cove . Warsaw . .. Washington ... Wilmington , . Winston- Salem

WInton

NORTH DAKOTA

Bismark

Minot

OHIO

Akron Amherst

Cincinnati Cleveland Columbus

Dayton ^ Mansfield " Middleburg Heights Shaket Heights

Springfield Toledo

University Heights . OKUWOMA

Oklahoma City Tulsa .... OKCON

Albany . . .

Ashland . Astoria Beaverton Bend Bandon

Central Point . Coos Bay — Corvallis . . . .

Dallas City . .

Eugene

Grants Pass . Hillsboro .... Klamath Falls Lake Oswego . Medford

Milwaukie . . .

.'endleton . . Portland

Silverton . . . .

Toledo

Tualatin Yachats

1970 S I I

3.182 3,148

1,213 2,701

8.961 46,169

132,913 917

34,703 32,290

275,425

9,902 452,524

750,903 540,025

243,601

50,743

12,367 36,306

81,941 383.818

17,055

18.181 12,342 10,244

18.577

13,710

1.832 4.004

13.466 35,153

10.423 76.346

12,455

14,675 15,775

14,573 28,454

16,379

13,197 380,620

4,301 2,818 768 414

PENNSYLVANIA

Allentown 109,527

Bethlehem 72,686

Dubois 10,112

Erie 129,231

Girard 2,631

Harrisburg 68,061 Muhlenberg Township . . ^.212

Philadelphia 1,950,098

Pittsburgh 520.117

Scranton 103.564

State College 33.778 West Mifflin 28.070

368.856

330,350 - - -

1«70

i«ftt<lcttoii Po»»litloii

Irving 97.457

Killen 35,507

Mineral Wells 18.411 Odessa 78.380 Saginaw 2, 382 San Antonio 654. 153 Texarkana 30.497

Wichita Falls 96.265

UTAH

Murray 21,206 Ogden 69,478

Provo 53,131

Roosevelt 2,005

Salt Lake City 175.885

VIRfiINU

Alexandria 110.927

Arlington 174,284 Chesapeake 89,580

Fairfax 21,970 Hampton 120,779

Newport News 138,177

Norfolk 307.951 Richmond 249,621 Roanoke . . . 92,115

Virginia Beach 172,106

WASHIN8T0N

Bellevue 61.102

Cheney 6.718

Colfax 2,664

College Place 4,510

Kennewick 15,212 Medina 3.455 Pullman 20.509

Renton 25.878

Richland 26.290

Seattle 530.831 Snohomish 5.174 Spokane 170,516 Tacoma 154.581

Walla Walla 23.619 Yakima 45.588

WISCONSIN

Janesville 46.426 Madison 173.258 Milwaukee 717.372

Racine 95.162

Sparta 6.258

WYOMING

Casper 39.361 Cheyenne 40.914

Lander 7,112

Powell 4.807

Riverton 7.995 Worland 5.055

Total 67,383,478 ' S 1 M 1 M 1 i - - o - D n n - - ana n n (J 'J

:3 - -ii --

RHODE ISLAND

Cranston

East Providence Pawtucket

Providence .... Warwick

74,287

48,151 76,984

179,116 83,694

SOUTH CAROLINA

Columbia

Florence 113,542 -

25,997 -

SOUTH DAKOTA Lemmon

Sioux Falls . . .

2,456 - -

72,488 -

TENNESSEE

Chattanooga 119,923

Kingsport 31,939

Knoxville 276,293 Memphis 623.530

Nashville 448.003

TEXAS

Amarillo . . . . .

Austin Beaumont . . Corpus Christi Dallas

El Paso

Fort Worth . . .

Garland

127.010 193.862

117.548

.... 204.525

844,401

.... 322,261

.... 393,476

81,437

Houston 1,232,802 ---

36
are referred to as performance type

regulations while those without noise

emission limits are non-quantitative and

difficult to enforce. Interest in

regulating land use through the zoning

process remains the largest single legal

category of noise control. However,

vehicular, aircraft and building controls

with quantitative noise emission limits also

have grown over the previous year." [33]

2.4.4.2. State Regulatory Efforts

"Recently more States have been entering

the noise control field. Some State

legislation specifically regulates noise,

whereas most assign the environmental

departments the task of studying and

promulgating regulations.

"California's law governing airport

noise became effective December 1, 1971.

The law requires operators of existing

airports to monitor the noise of aircraft on takeoffs and landings and to establish a Noise Impact Boundary around the airport

with noise at this boundary to be reduced

periodically over the next fifteen years.

New airports must conform to the standards

applicable (in fifteen years) to existing

airports. The airport operator must also

set noise limits on single takeoffs and

landings. Those airports which fail to come within the noise limits may lose their

licenses or face other State sanctions.

California has attempted to avoid

constitutional difficulties by basing its

legislation on the State's licensing power

over airports and the proprietary rights of

airports vis-a-vis the scheduled airlines

and other users. The practical difficulty

with this law is that it may require airport

operators to curtail operations or to make

major purchases of land. The former measure

could have major repercussions for national

air transportation patterns, while the

latter alternative could lie well beyond the

financial capacity of the airport.

"The bi-State Port of New York Authority

has set an objective noise limit of 112 PNdB

for takeoffs from its four airports. This

limit is very high, however, and there is

also alleged to be systematic cheating by

aircraft momentarily cutting power as they

pass the monitoring equipment.

"Almost all States have laws governing

motor vehicles, most requiring mufflers,

some restricting unnecessary use of

automobile horns. Increasing numbers of

states are setting noise level limits on vehicle operation and, in some cases, on new

vehicles. States also provide quantitative

standards on motorcycles and in increasing

numbers, on snowmobiles as well.

"Colorado alone sets limits on noise

radiating from construction sites and few

States have any requirement concerning the

acoustical treatment of buildings. The

regulation at the State level of noise from

commercial sources is negligible. Many

states do prohibit disturbances of the

peace." [32]

An adequate current review of state

noise regulatory efforts is not to be found

within the literature, although preliminary

response to inquiries indicates an increasing degree of concern on the part of

state governments.

2.4.4.3. Federal Regulatory Efforts

"The Noise Pollution and Abatement Act

of 197C was the first legislation to provide

a central focus to environmental noise

abatement at the Federal level. This act

provided for an Office of Noise Abatement

and Control to be established in the

Environmental Protection Agency for the

purpose of carrying on research and

investigations into the environmental noise

problem. §402(c) of the act also requires

any Federal agency whose activity is creating noise amounting to a public

nuisance to consult with EPA to determine

possible ways to abate such noise.

"The National Environmental Policy Act

of 1969 has required since January 1, 1970,

that Federal agencies submit environmental

impact statements on all Federal actions

significantly affecting the quality of the

human environment. These statements should

include the noise impact of the proposed

action

.

"The 1968 amendment (§611 -- Abatement

of Aircraft Noise and Sonic Boom) to the

Federal Aviation Act of 1958 was the

beginning of the Federal government's active

participation in the aircraft noise

abatement area. Part 36 of the FAA Aircraft

regulations, effective December 1, 1969, and

issued pursuant to this legislation,

requires all new subsonic aircraft to conform to specified noise levels on takeoff

and landing before issuance of type

certification.

"The first active consideration of

highway noise at the Federal level was Policy and Procedures Memorandum 20-8 of the

Bureau of Public Roads, issued January 14,

1969 Pursuant to a 1970 amendment to

37
the Federal -aid Highway Act, the Secretary

of Transportation... is to develop and

promulgate standards for highway noise

levels compatible with different land uses after July 1 , 1972.

"Regulations of May 20, 1969, pursuant

to the Walsh-Healey Public Contracts Act,

set noise exposure limits for employees of

Federal supply contractors. With the

enactment of the Occupational Health and

Safety Act of 1970 these standards were

applied to all business affecting interstate

commerce, with the provision that any State

may take over regulation of occupational

noise with the approval of the Secretary of

Labor. Civil and criminal penalties for

violations are provided. The Bureau of

Mines of the Department of the Interior

applies the standards to some 1,900 licensed

mines pursuant to "the Federal Coal Mine

Health and Safety Act of 1969.

"Pursuant to the Construction Safety Act

of 1969 the Walsh-Healey noise standards

have been applied to Federal construction

projects by th6 Department of Labor." [32]

At the time of this writing (March

1975), the Occupational Safety and Health

Administration has proposed retention of the

90 dB A-weighted limit for an eight hour

exposure to industrial noise, *with, however,

some changes in the earlier provisions. The

Environmental Protection Agency has

advocated adoption of more stringent noise

exposure criteria, and in particular has

suggested an A-weighted sound level of 85 dB

as a more acceptable limit for an 8-hour

exposure. These differences of proposed

policy are undergoing discussion,

"In the area of the acoustical

characteristics of buildings, the Department

of Housing and Urban Development has issued

Policy Circular 1390.2 (August 4, 1971),

concerning the acoustical acceptability of new sites and existing buildings to be aided

by HUD funds. The noise limits involved

relate to programs of mortgage underwriting

in noisy areas near airports and minimum

standards for multi family dwellings for

which HUD financial assistance is sought.

"On October 27, 1972, the President

signed into law the Noise Control Act of

1972. With this legislation the

•Environmental Protection Agency (EPA) has

significant authority to deal with numerous noise sources for the first time. The

Administrator of the EPA is authorized to promulgate noise emission standards for

construction equipment, transportation

equipment (including recreational vehicles),

any motor or engine (including any equipment

of which an engine or motor is an integral

part), electrical or electronic equipment,

railroads and motor carriers. EPA is also

to assume an important role in the

development of aircraft noise standards.

The new legislation clearly provides EPA

with considerable authority to deal with the

nation's present noise problems." [32]

In most of the aforementioned

legislation, NBS provided comments to Congressional committees prior to the time

the legislation was voted on by the

Congress, and has assisted the responsible

agencies in implementing the legislation

(e.g., development of measurement

methodologies, standards review).

The preceding material also is cited in

order to indicate that there is an appreciable amount of activity involving

local, state, and Federal regulatory

agencies. The inter-relationships of these

agencies is discussed in Appendix C, which

is an edited survey of an oral presentation

on government standards and regulations.

2.4.4.4. Quasi-Governmental Regulatory

Units

There are few of these units in

acoustics, with the possible exception of

the American National Standards Institute.

The relationship of this institute to standardization institutions and in the

acoustical measurement infrastructure is

discussed in Sections 2.2.1.1.1. and

2.2.1.1.3.

2.5. Direct Measurements Transactions Matrix

2.5.1. Analysis of Suppliers and Users

., The summary input-output matrix

contained within this section is based upon

identification of 18 institutional elements,

which serve dual roles in the measurement

infrastructure as suppliers and users. These eighteen elements are:

1. Knowledge Community: Scientific

organizations, the general scientific

community; academic institutions

(elementary and secondary schools,

colleges and universities, vocational

training institutions), libraries,

information centers; domestic and

international professional, scientific

and technical societies; technical

publ ishing houses ; and the like.

38
2. International Metrologiaal

Organizations: International Bureau of

Weights and Measures (BIPM).

International Organization for Legal

Metrology (OIML).

3. Documentary Standardization

Organization: American National

Standards Institute (ANSI) and American

Society for Testing and Materials (ASTM)

ajid their affiliated organizations.

International Organization for

Standardization (ISO) and International

El ectrotechnical Commission (lEC). The

national physical standards laboratories

and services of other nations. The

documentary standardization committees

of domestic and international professional , scientific, technical, and

industrial trade organizations. The

standardization activities of the U. S. Department of Defense.

4. Instrumentation Industry: Instruments

and related products-- engineering and

scientific instruments, environmental

controls, process control instruments,

other measuring and controlling devices.

5. National Bureau of Standards : The

National Bureau of Standards -- all

Institutes and divisions.

6. Other U. S. National Standards

Authorities: Only three such

organizations have been identified —

The U. S. Naval Observatory (USNO) in

the field of time-keeping (time and

frequency); The U. S. Geological Survey

in aerial camera calibration (optics);

The U. S. Coast Guard for measurements

related to sea transportation of

liquified natural gas. These have

little relevance to this particular

study

.

7. State and Local Offices of Weights and

Measures (OWM's): The state, county,

and city or similar agencies responsible

for policing the honesty of weights and measures practices in commercial

transactions. These have little

relevance to this particular study.

8. Standards and Testing Laboratories and

Services: Members of the National

Conference of Standards Laboratories and

organizations eligible for such

membership. Testing laboratories such

as Underwriters' Laboratories and the

many commercial analytical laboratories.

Note also that all standards

laboratories and organizationally

distinct testing laboratories are included in this sector, no matter in what larger organization they may be

embedded. Thus, the standards

laboratory structure of the Department

of Defence is covered here, and the

standards laboratories of the major

economic industrial sectors.

9. Regulatory Agencies (excluding OWM's):

Federal, state, and local government

regulatory agencies, excluding those

units which regulate the commercial

weights and measures field or which

perform classical policing or law-enforcement duties, or the normal

legislative branches of government.

Examples at the Federal level include

the Bureau of Mines, Consumer Product

Safety Comnission, Environmental

Protection Agency, National Highway

Traffic Safety Administration, and the

Occupational Safety and Health

Administration. On the local level,

similar agencies are active primarily in

the public health field, in occupational

safety and health, and in enforcing

environmental protection regulations.

While the presumption is that all of

these agencies are governmental, there

may be instances of private or

quasi -governmental agencies that fall in

this sector.

10. Department of Defense (excluding

standards Idbs . ) : The Air Force, Army,

Navy, Advanced Research Projects Agency,

Defense Nuclear Agency, Defense Supply

Agency and al

1

intelligence and security

agencies

.

11. Civilian Federal Government Agencies:

Congress and its agencies. Judicial

branch. Executive Office of the

President. Depts. of Agriculture,

Housing and Urban Development, Interior,

Justice, Labor, State, and Treasury,

Dept. of Commerce, excluding NBS, but

including the National Oceanic and

Atmospheric Admin, (and therefore the

National Weather Service and National

Ocean Survey), Patent Office, and Office

of Telecommunications. Dept. of Health,

Education and Welfare, including the

National Institutes of Health, and

National Institute for Occupational

Safety and Health. Dept. of

Transportation, including the Coast

Guard and Federal Aviation Admin.,

Energy Research and Development Admin.,

39
General Services Admin., National 17 Aeronautics and Space Admin., National

Science Foundation, Tennessee Valley

Authority, U. S. Arms Control and

Disarmament Agency, U. S. Information

Agency, U. S. Postal Service, and

Veterans Admin.

12. State and Local Govevrment Agencies : All

aspects of state and local governments,

with some major exclusions — Public

schools, colleges and universities;

Offices of Weights and Measures;

Regulatory agencies; Public health 18

departments and publicly run hospitals.

All these groups are covered in other

sectors

.

13. Industrial Trade Associations

Industrial, business, or trade

associations, such as the Electric Power

Research Institute (ERPI), the 19

Electronic Industries Assn. (EIA), the

Motor Vehicle Manufacturers Assn.

(MVMA), the Air Conditioning and

Refrigeration Institute (ARI), and the

Compressed Air and Gas Institute (CA6I).

14. Extractive Industry: Crops. Livestock.

Agricultural services, including

landscape and horticultural services.

Forestry. Mining. Coal mining. Oil

and gas extraction. Stone, gravel,

clay, chemical, and fertilizer minerals.

15. Construction: General building

contractors. Heavy construction

contractors. Special trade

contractors--plumbing, heating, air

conditioning, electrical, water well 20

drilling, etc. Note that engineering

and architectural services relevant to this sector are included here.

1 6 . Food/Tobaoco/Texti le/Appare l/Lumber/

Fumituj'e/Paper/Leather : Food and

kindred products. Tobacco

manufacturers. Textile mill

products —weaving, knitting, floor

covering, and yarn and thread mills; 21 tire cord and fabric cordage and twine.

Apparel and other textile products.

Lumber and wood products—logging camps,

sawmills, mobile homes, prefabricated 22

wood buildings. Furniture and fixtures:

drapery hardware, blinds and shades.

Paper and allied products— pul p and

paper mills, building, paper and board.

Leather and leather .products--tanning

and finishing, footwear (except rubber).

i

Chemiaals/Petroleum/Rubber/Plas tics/Stone/

Clay/Glass: Chemicals and allied

products. Petroleum and coal

products —petroleum refining, paving and

roofing materials. Rubber and

miscellaneous plastics products —tires,

footwear, miscellaneous plastics

products. Stone, clay and glass

products --flat glass, cement,

structural clay products, vitreous

plumbing fixtures, block and related

products, lime, gypsum products, stone.

Primary and Fabricated Metal Products:

Primary metal industries —iron and

steel, nonferrous metals, plate, sheet.

Fabricated metal products--heating

equipment, household furnace

humidifiers, structural metal, doors,

prefabricated metal buildings.

Machinery, except Electrical: Turbines,

turbine generators, internal combustion

engines; farm, lawn, garden,

construction, mining, oil field, rolling

mill, metalworking, food products,

textile, woodworking, paper industries

and printing trades machinery;

industrial trucks and tractors; pumps,

compressors, blowers, fans; speed

changers, drives, and gears;

typewriters, electronic computing

equipment, calculating and accounting

machines; commercial laundry,

refrigeration and heating equipment;

humidifying equipment, except household

furnace or room electric; carburetors,

pistons, rings, and valves.

Electrical and Electronic Equipment:

Transformers, motors, and generators,

refrigerators and freezers, electric

humidifiers, laundry equipment, vacuum

cleaners, sewing machines, small

electrical appliances; radio and TV

sets, phonograph records, telephone and

telegraph apparatus, radio and TV communication equipment.

Transportation Equipment: Motor

vehicles, aircraft, ships, boats,

railroad equipment, motorcycles.

Transportation and Public Utilities:

Railroad transportation. Local and

interurban passenger transit, including

taxicabs and school buses. Trucking and

warehousing. Water transportation. Air

transportation. Transportation

services . Communication —telephone,

telegraph, radio and TV broadcasting,

other communication services.

40
23. Trade (Retail and Wholesale) /Insuranae/

Finance/Real Estate/Personal Services/

Pr-inting and Publishing: Wholesale

Trade--autos , construction materials,

electrical apparatus and appliances, TV and radio, electronic equipment, heating

and air conditioning, refrigeration,

industrial machinery, transportation

equipment. Retail Trade —building

materials. Finance, Insurance and Real

Estate. Services (other)--radio and TV,

motion pictures from production through

theaters. Printing and

Publ ishing--commercial printing; photoengraving and related printing and

publishing services.

24. Health Services: Offices of physicians,

dentists, osteopathic physicians,

chiropractors, optometrists; nursing and

personal care facilities; hospitals;

medical and dental laboratories;

outpatient care facilities, other health

and allied services

.

25. General Public: The

person-on-the-street, housewife,

automobile driver, private pilot,

amateur radio operator, home

do-it-yourselfer, camper, amateur

sportsman; the worker as a private

person on the job, being exposed to job

safety and health hazards. The

consumer, consumer advocate, public

interest advocate, citizen taxpayer.

End users of most data, but frequently

only in an indirect manner in this

field.

The various relevant measurement

capabilities and services offered by the

eighteen suppliers are given in table 6,

along with the needs of these same sectors

as users and the services they procure.

2.5.2. Direct Measurements Transactions

Matrix

The direct measurements transaction

matrix, figure 7, indicates several

dimensions of the transactions occurring

between the several suppliers and users. Within each matrix element there may be as many as five symbolic entries denoting the

several dimensions of the transaction. The

coding for four of these is, consistent among

all of the measurement system studies in

this series, and is described in the key at the bottom of the table.

The alphabetic symbol in the lower right

hand corner describes the type of provision

of service in the direct measurement

transaction.

A. > End-use -Measurement Data

B. Other Measurement Services (e.g.,

cal ibrations)

C. Measurement Instrumentation and

Associated Software

D. Measurement "How To" Information

E. Measurement "Needs" Information

The appearance of only one symbol in any

transactions box (that for the primary

magnitude quantity) implies that NBS' knowledge is insufficient to support an estimate of the subsidiary information

items. An empty box indicates that the

volume of transactions is judged to be

negligible. If one or more of the corners

have symbols entered, then those that are

still blank can be read as zeros.

2.5.3. Highlights re Major Users

The majority of the users of the

acoustical products listed in table 3 fall

into the groups identified in table 7. Additional more specific noise abatement

products can be identified; however, the

group becomes so large that much of our present day industrial technology can be

included. For example, manufacturers of

business machinery purchase vibration

damping products to implement noise control measures directed toward the control of

related structure-borne vibrations. Yet

they may not attempt to quantitatively

measure the mechanical properties of the

vibration damping product. They may instead

elect to judge the product's effectiveness

through measurement of the reduction of

radiated noise, an acoustical measure of the

effectiveness of a vibration damping

product. To implement this evaluation of a vibration control product, they thus require

instrumentation to perform the acoustical

measurement. There are numerous similar

identifiable examples which could be cited,

and a large segment of current technology

ultimately becomes involved.

41
Table 6. Measurement capabilities and services supplied, needs and services procured, by acoustics measurement

systems sectors.

Suppi iers

1. Knowledge Community

2. International Metrological Organizations

3. Documentary Stahdar5ization Organizations

Measurement

Capabi 1 i ties

Basic physical research, many

acoustical measurements

(None specific)

No measurement capabi 1 i ti es , per se

Services Provided

Dissemination of know- ledge, standards com- mittees evolve standards, consultant services

Measurement methodology,

development of instru- mentation systems, calibration services, provision of data base, etc

.

Evolve measurement

methodologies

,

disseminate same.

Measurement Needs

Measurement data

Measurement data

,

calibration data

(None specific)

Services Procured

Information on meas- urement methodologies, measurement data, publications, etc.

Information on meas- urement needs, instru- mentation, information

on measurement methodology

Measurement data, information on methodologies

Instrumentation Industry

National Bureau of Standards

Other U. S. National Standards Authorities

State and Local Offices

of Weights and Measures

Standards and Testing

Laboratories and Services

9. Regulatory Agencies

(excluding OWM's)

10. Department of Defense

(excluding standards

labs)

11. Civilian Federal Government Agencies

12. State and Local Government Agencies

13. Industrial Trade Associations

14. Extractive Industry: Agriculture, Mining, etc.

15. Construction

16. Food/Tobacco/Textile/

Apparel/Lumber/Furni ture/ Paper/Leather

Acoustical measurements requi red for ^product development

Wide range of acoustical measurements and basic research

(None specific)

(None specific)

Wide range of acoustical measurements

Noise emission monitoring, environmental noise monit- oring

(Largely excluded

from study)

Acoustical measurements in research

(e.g. , NASA)

Noise emission

or environmental

noise monitoring

No measurement capa- bilities, per se

at the trade association level . More within relevant

industry

Noise emission

monitoring, environmental noise monit- oring

Noi se emi ssion monitoring, environmental noise monit- oring

Noise emission monitoring, environmental noi se monitori ng

Provide measurement

instrumentation, calibration services

Measurement methodology,

development of instru- umentation systems, calibration services, provision of data base,

etc.

(None specific)

(None specific)

Measurement data,

cal ibration .services

,

etc.

Measurement data, measurement methodologies, etc.

(Largely excluded

from study)

Measurement needs information, measure- ment data, etc.

Measurement data, measurement methodologies

Measurement data, measurement needs information, etc.

Measurement data

Measurement data, calibration data

Calibration services, measurement needs

i nf ormati on

Information on measurement needs, instrumentation information on measurement methodology

(None specific)

(None specific)

(None specific)

(None specific) (None specific)

(None specific) (None specific)

Measurement data

,

cal ibration data

Information on measurement methodology, measurement

data

Measurement data

Information on measurement methodology, measurement

data

Information on measurement methodology, measurement

data

Measurement data, measurement needs

Information on measurement methodology, measurement

data, calibration

data

information on measurement methodology, measurement

data, calibration

data

Information on measurement methodology, measurement

data, calibration

data

Information on measurement needs, instrumentation information on measurement methodology

Measurement data, instrumentation, information on measurement methodology and on measurement needs

Measurement data, instrumentation

Measurement data, instru- mentation, information on measurement methodology and

on measurement needs

Measurement data, instru- mentation, information on measurement methodology and

on measurement needs

Measurement data

Measurement data

Measurement data

Measurement data

42
Table 6 (Continued)

Supp1 iers Measurement

Capabi 1 i ties Services Provided Measurement Needs Services Procured

17. Chem./Petro. /Rubber/ Plastic/Stone/Clay/Glass

18. Primary and Fabricated

Metal Products

Noise emission

monitoring, environmental noise monit- oring

Noise emission monitoring, environmental noise monitori ng

(None specific)

(None specific)

Information on Measurement data measurement methodology, measurement

data, calibration

data

Information on Measurement data measurement methodology, measurement

data, calibration

data

19. Machinery except

Electrical Noise emission monitoring, environmental noise monit- oring

Product noise data Information on Measurement data measurement methodology, measurement

data, calibration

data

20. Electrical and Electronic

Equi pment Noise emission

monitoring, environmental noise monit- oring

Specifications re: instrumentation

response

Information on Measurement data measurement methodology, measurement

data, calibration

data

21. Transportation Equipment

22. Transportation and Public Utilities

23. Trade/ Ins./ Fin./ Real Estate/ Pers. Svcs./

Print., Pub.

24. Health Services

25. General Public

Noise emission monitoring, environmental noise monitori ng

Noise emission

monitoring, environmental noise monit- oring

(None specific)

Medical diagnostic

data

Very little measurement capability

Product noise data, measurement procedures

(None specific)

(None specific)

Information on Measurement data measurement methodology, measurement

data, calibration

data

Information on Measurement data measurement methodology, measurement

data, calibration

data

(None specific) (None specific)

Medical diagnostic and Information on therapeutic services instrumentation performance

Instrumentation and calibration services

Measurement needs information Measurement data Measurement methodology

information

43
DIRECT MEASUREMENTS

TRANSACTIONS

MATRIX FOR ACOUSTICS £

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COMMUNITV \ iScianca Educ 2

2 1 3

1 1 2

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2 1 3 2 2 X 2 1 1 3 2 2 2 3 3 3 2 3 1

2 INTERNATIONAL METROLOGICAL

j DOCUMENTARY

ORGANIZATIONS

1 2 2

3 2

2 1 3

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2 2

4 2

2 1 3

2 3

2 X 2 3 2 3 1 2 1 4 1 1 1 2 3

2 1 4 1 3

4 INSTRUMENTATION

INDUSTRY

2 i 3

1

2 1 2

2

22^

2 1 2^

3 2 3

2

2 3 1 4

2 1 3

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2 1 3

2 3 3 3 3 3 3 3 3 2 3 1

Nes

2 2 2

2 1 3

2 1 S 1 3

2

2 1

^ 2 3 3 2

' 1 2

3 2

3 2 3 2 1 2 2 1 3

2

2 3

^

1 2

e OTHER US NATIONAL STANDARDS

AUTHORITIES

T STATE ft LOCAL

OFFICESOF

8 STANOARDSb TESTING LABORATORIES AND SERVICES

1 3 2 1 3

2

2 1 2

1 22 1 4

2 X 2

3 4 2 3 3 3 3 2 2 3 2 1 1 1

9 REGUIATORV

AGENCIES 1

1 2

3 J

3

1 2

3 3

1 X 2 3 1 4

3

4 2 4

4 1 3

2

4 2

4 2 2 4 . 2

2 4 1 4

2

4 1 3

2

1 4 3

3

4

3 2

3 4

10 DEPARTMENT OF DEFENSE X 1 2 2

3

2 X X X X X X X X X X X X X

11 CIVILIAN FEDERAL GOVERNMENT

AGENCIES

2

2 1 3

1

2 3 2 1 X

3 3

2

3 1 2

2

3 1 2^

U STATE fa LOCAL GOVERNMENT

AGENCIES

1

1 2 1 X 2 1 1 1 1 1 1 1 1 1 , 2

13 INDUSTRIAL TRADE

ASSOCIATIONS

1 2 2 3

2

2 t 3

2

2 1 3 1 3

2 1 4

2 X 2 2 1 3 2

1 1 1 1 1 1 1 1 2

14 E KTHACTfVE IND AG MINING ETC 2 1 1 2 X 2 I

15 CONSTRUCTION

iStC O.. CI

2

3 3 2 3 3 3 2 2 2 2

2 1 3

2

1 3

16 FOOD TOe TEXTILE APPAREL LBR FURN'PAPER

LE AIHER iSIC 20 24 3'l 2 2 3 1 3

2 X 2 2 2 2

17 CHEM PETROL RUBBER

PLASTICS STONE CLAV GLASS iSIC 28 30 331 2 2 3 X 2 2 2 1

18 PRIMARY b FAB METAL PRODUCTS

iStC 33 34 3911 2 3 X 2 2 2 2 2 1

19 MACHINERY

EXCEPT ELECTRICAL 2 4 1 3 0

2 3 2

2 1 X 2 2 2 2 2 2 2 22 1 ^

3 2 2 2 2

70 ELECTRIC AND

ELECTRONIC EQPMT

ISIC Ma,o. Gpaei

1 2 2 2

1 X 1 2 3 2

21 TRANSPORTATION EQUIPMENT

<SlC Major Gp 371 2 3 1 2 1 2

2

3 1 3 X

3 1 3

2

4

1 1 1 1 I 1 1 2 1 2 1 2

22 TRANSPORTATION - PUBLIC UTILITIES

ISIC D'v El 2 3 2 3 1 3 X 3 3 2 2 2

23 TRADE INS fIN REAL

EST PERSSVCS PRINT PUB

iSIC f H bal 1 271

1

24 HEALTH SERVICES

ISIC Maior Gp 80) 2 1 3 2 2 2 X 2 2 1 V r 1 1 1 I 1 ^ 2 K

GENERAL PUf Lie 1 1 1

1 3 2 X 2 2 1 2 2

KEY TO MATRIX ENTRIES

C - IMPORTANCE OF TRANSACTIONS

1 = Purely convenience

2 ^ Strongly desirable

3 = No real alternatives 4 = Essential

B - RATE OF CHANGE

N = Declining

0 - Stable

2 = Growing

4 = Growing explosively

USERS

C D

SUPPLIERS A

B

D - (INIADEQUACY OF SERVICES

0 = No improvements needed

1 = Could be improved

2 = Marginal

3 = Serious deticiencies 4 = Out of control A - MAGNITUDE OF TRANSACTIONS

0 = Trivial

1 = Minor

2 = Moderate

3 - Important

4 = Major

Unknown, X = Not studied. Blank

Figure 7. Acoustical measurement system input-output direct transactions matrix.

44
Table 7. Users of acoustical measurement instrumentatioa.

Manufacturers and Users of "Noisy" Products

Manufacturers and Users of Noise Abatement Products

Federal, State, and Local Regulatory Agencies

Environmental Control Engineers in Industrial Plants

Research Scientists and Engineers in

Industrial Laboratories

Independent Research Institutions

Government Laboratories

Academic Laboratories

Independent Testing Laboratories

Architects and Urban Design Engineers

Acoustical Consultants

3. IMPACT, STATUS AND TRENDS OF THE MEASUREMENT SYSTEM

3.1. Impact of Measurements

3.1.1. Functional, Technological and

Scientific Applications

3.1.1.1. Use and Function of the

Measurements

The preceding sections have described a number of acoustical measurement processes

which are related to the unifying theme of

accomplishing an adequate, objective,

quantitative characterization of sound or acoustical properties. By implication it

may. appear that the principal utility of

these measurements is for the implementation

of noise control legislative or abatement

measures, but this is not strictly the case. Acoustics is a scientific discipline with

relevance to many aspects of man's

existence. Many of these aspects have grown

phenomenally without explicit appreciation

of the importance of acoustical phenomena.

For example, it was only as recently as the

1930's that the fundamental physical

phenomena involved in airborne sound

transmission through walls and partitions

was studied in any detail. [36] Pioneering

work of Buckingham [34], Chrisler and Snyder

[35], and London [36] at NBS led to the

evolution of a quantitative single-figure

rating system [19] to evaluate this property

of building system components. Prior to that time, architects were only able to rely

upon crude empirical rules in order to provide desired acoustical properties —

rules that were Often inadequate to the

challenge.

It was also shown that acoustics is used

for the improvement of communication

systems, for entertainment and aesthetic

purposes, and for numerous other purposes,

including the implementation of noise

control measures. Acoustical measurements

are required for the evaluation of design

changes and within research and development

programs dealing with devices such as communication system components (e.g.,

telephone transmitter microphones and

receiver earphones), systems for sound

reinforcement and entertainment purposes,

etc.

Recent legislative actions directed

toward noise control have provided a legislative incentive or imperative to ensure that such factors as product noise

emission or workplace noise levels are within prescribed limits. This legislative

imperative is a relatively new element in

the motivating factors for acoustical

measurements, and has given rise to a burst

of activity and attention to noise

measurement tools and methodologies. Many

current NBS measurement activities typify

those required for the enforcement of noise

control legislation, the calibration of

measurement instrumentation, and the

quantitative assessment of hearing loss.

3.1.1.2. Impacts on Technologies

Ultrasonic flaw detection is an excellent example of a technology which has

45
grown rapidly in recognition of the

possibility of making use of acoustical

measurements to serve some desired goal, in

this case, non-destructive testing.

Acoustical measurements are also central to the implementation of the growing noise

control technology. Within noise control

technology there is somewhat less direct concern with the measurement process, per

se. However, there is inevitably an implicit reliance upon the objective

quantitative knowledge to be obtained from

acoustical measurements, if the measurements

are for any of the following purposes: — calibration of instrumentation — characterization of product noise

emission — evaluation of the effects of design

changes — characterization or monitoring of

environmental noise levels — characterization of acoustical

properties of architectural

materials and systems — characterization of auditory acuity — prediction of human response to sounds from physical measurements.

The technological impact of the various

measurements is far-reaching. Two examples

should serve to illustrate this fact: the

impact of the microphone calibration

process, and the impact of the audiometric

examinations required by the Occupational

Safety and Health Administration.

Figure 8 presents a block diagram to illustrate the extensive technological

impact of precision microphone calibration

processes on our society. In figure 8, the

top portion of the flow diagram indicates

the basic physical measurements required to carry out the absolute pressure and absolute

free field calibrations of microphones.

Comparisons of these data yield the origin

of the free-field correction, and provide

input for the evolution and improvement of

measurement standard American National

Standard Method for the Calibration of

Microphones, SI. 10-1966 [9].

The use of the NBS pressure microphone

calibration service or of the measurement

standard will yield a knowledge of the

microphone calibration which enables one to

infer pressure data from corresponding

electrical data. One then may make use of a calibrated microphone to perform laboratory

and field measurements of sound, these

measurements are central to... — characterization of noise — sound power measurements — architectural acoustics — audiometry — hearing aid calibration — human response to sounds — communication systems and

broadcasting — sound recording and reproducing.

The range of the related technologies

requiring these types of information touches

upon much of our daily existence.

Section 2.4.4.5. described some of the

impacts of proposed changes in the

Occupational Safety and Health

Administration workplace noise exposure

rules, and indicated the reliance upon

audiometric testing that will be used to detect damages in hearing thresholds. A four- to ten-fold increase in the number of

annual audiometric measurements may take

place as a consequence of these changes in

the regulations.

All of the research and development in

audiometry is closely allied with the needs

and problems of international and national

standards committees to formulate standards

for equipment and criteria for measurement

of hearing. These standards have been

accepted by the industry (who have

participated in their formulation). Many of

the standards approved by societies such as the American Academy of Opthomology and

Otolaryngology and the American Speech and

Hearing Association have been incorporated

into state and Federal Law. Thus, the

equipment used in the measurement of

hearing, whether during a general physical

examination, in a school system, in industry

for employees, in a government medical

office or in the armed forces, has been

calibrated to meet these standards which

have been written by, reviewed by, or based

on research by NBS employees.

46
ANSI WG

S1.S4-CAUBRATIOIl OF MICROPHONES

MEASUREMENT

STANDARD

ANS S) 10 ?—

¥

LENGTH. TIME ELEC.

RESIST., DC VOLTAGE. BAROM. PRESSURE.

RATIO OF SPECIFIC HEATS

ABSOLUTE

PRESSURE

CALIBRATION

NBS

PRESSURE

CALIBRATION SERVICES

NBS

EXPERTISE

LENGTH. TIME ELEC

RESIST . DC VOLTAGE. TEMPERATURE. RELA

TIVE HUMIDITY

FREE FIELD CORRECTION

CALIBRATION BY CUSTOMER OF WORK

ING STANDARDS OR OTHER SOUND MEAS

URING DEVICES

ABSOLUTE

FREE-FIELD CALIBRATION

LABORATORY AND FIELD MEASUREMENTS

NOISE: AIRCRAFT. MOTOR VEHICLE. COMMUNITY, MISSILE. SONIC

BOOM.. BUILDING CONSTRUCTION.

ETC.

SOUND POWER

MEASURE- MENTS

ARCHITECTURAL ACOUSTICS AUDIOMETRY HUMAN

HEARING AID RESPONSE

CALIBRATION TO SOUNDS

BROADCASTING AND

COMMUNICATION

SYSTEMS

SOUND

RECORD

ING AND

REPROD

UCING

Figure 8. Technological impact of precision microphone calibration processes.

47
3.1.1.3. Scientific Fields Affected

During the recent past, the principal

fields affected by the activities in

acoustical measurements have been the

related engineering disciplines, principally

electrical engineering, mechanical

engineering, aerospace engineering, civil

engineering, and the newly established

interdisciplinary field, acoustical

engineering. Interactions with more basic

scientific fields such as physics and

mathematics have continued to be important.

Substantial growth of some of the related

social sciences, including the field of

audiology and psychoacoustics , in response

to societal concern over noise has also

taken place.

3.1.1.4. Impacts on End Users

There are three broad types of impact on the end user — social, technological, and

economic.

Accurate characterization of the

acoustical properties of architectural

materials facilitates noise control

engineering in buildings. However, it is

interesting to note that while many of these

materials are advertised as products

specifically advised for their acoustical

utility, aesthetic and mechanical

construction factors as well as cost factors

enter as important elements in the marketing

process. The consumer often implicity

assumes that "acoustical materials" have

acoustical merit, without explicit

evaluation of the acoustical measurement

test data. It is nonetheless extremely

important that the test data be obtained

with the use of standardi/Led measurement

procedures, that the data be made available

as product specifications, and that the consumer be trained in the interpretation of

the test data so that the utility of

acoustical materials can be properly

assessed.

Measurements enable the development of

improved noise control products through

assessment of the effects of variations in

the manufacturer's design engineering

process. Further, through open publication

of accurate test data, it becomes possible

for products with demonstrable superiority

to succeed in the open market, and equally

for inferior products to fall into disuse

and be eventually removed from availability.

Provision of accurate measurement services,

and publication of the data facilitate these

natural scientific and economic processes.

There is little available data at present to document. the total national

annual expenditure for the measurement of

sound absorption and insulation. This is

largely a consequence of the fact that the

tests are often conducted in a relatively

small number of industrial laboratories, and

that the industrial representatives do not

release these data. Some data are available, however, on the 1973 expenditure

for evaluating the sound absorption

properties of acoustical materials [37].

The statistics concern tests conducted by

independent laboratories. In 1973, 486

tests of sound absorption were conducted for

total fees of $73,000, while a total of 122

tests of ceiling attenuations were conducted

for $31 ,000.

An additional expenditure of $78,000 for

156 evaluations of the sound insulation of

walls, floors, and other building

constructions is also documented [38].

Thus expenditures of somewhat less than

$200,000 are cited for independent

laboratory tests. At least another $50,000

to $100,000 is spent annually to assess the

impact and acoustical properties of

resilient flooring materials and carpeting,

and another $250,000 may be spent to conduct

acoustical measurements concerned with

architectural materials at the' various

industrial laboratories. Thus one can identify a probable total annual expenditure

for acoustical measurements of this type to be somewhat more than $500,000.

Other significant impacts can be

identified as consequences of the measurement of such parameters as product noise

emissions or the detection of flaws in

materials through non-destructive testing.

But these measurements are less commonly

performed at standards and testing

laboratories and are dealt with elsewhere in

this report.

3.1.2. Economic Impacts

3.1.2.1. Costs of Measurement

A principal source of direct economic

impact of the measurement of noise emission

is that related to the enforcement of

regulatory actions. The measurement

methodology used to implement noise control

regulations must be technically,

administratively, and economically feasible

and reasonable. The ultimate determination

of appropriate satisfaction of the "feasible

48
and reasonable" criteria must be adapted to the probable characteristics of the chosen

noise source. Unfortunately, the economic

implications of the selection of appropriate

measurement methodologies have not been

adequately assessed. Recent Environmental

Protection Agency activities, pursuant to implementation of Section 6 of the Noise

Control Act of 1972, "Noise Emission

Standards for Products Distributed in

Commerce", will yield pertinent information.

Contracts have been written with at least

two consulting firms to carry out cost

effectiveness studies to estimate the

manufacturing costs associated with noise

reduction of a number of classes of

products. The nature of these studies is

described more fully in Section 3.T.2.3.

The studies conducted for the

Environmental Protection Agency are intended

to address the issue of manufacturing costs

associated with specified levels of noise

reduction. Two additional types of costs

are of interest in the context of this

report. They are, the costs associated with

(1) performance of a specified measurement

operation or with the performance of many

similar measurement operations assessed over

the nation or an industry for some specified

time period, and, in contrast, (2) the costs

associated with some specified amount of

measurement uncertainty. Examples of these

costs are given in the following material.

It should be noted that these data are not

as detailed as would be desirable. Further

studies of these costs should be conducted,

probably under the direction of professional

economists

.

As an example of the costs associated

with specific measurement operations, the

following can be cited.

Fomierly, in order to ascertain

compliance with the Department of Housing

and Urban Development noise standards for

site noise levels, an initial capital

investment of the order of $8000 was required for the necessary instrumentation.

The labor costs to conduct the measurement

involved approximately 9 man-days to obtain

the data and an additional 5 man-days for

data analysis, amounting to between $2000

and $4000.

Because of the expense of these tests,

NBS has, at the Department of Housing and

Urban Development's request, developed

special purpose instrumentation which wouTd

require an initial capital investment of

from $1500 to $3000, dependent upon the

configuration chosen. This instrumentation

is designed to conduct the data acquisition

and analysis operations automatically, and

can be installed by an unskilled person.

The labor costs associated with the conduct

of the test should be on the order of $50, a very substantial reduction in the costs of

both instrumentation and data acquisition

and analysis.

Previous sections have indicated the

nature of measurements conducted to determine the sound absorption and isolation

properties of architectural materials, and

of economic factors involved in. these

measurements.

Costs associated with measurement

uncertainty are briefly indicated in Section

3.1.2.3.

3.1.2.2. Economic Benefits of Measurements

It is difficult to quantitatively assess

the economic benefits of acoustical

measurements because many of the

measurements are conducted in order to quantify or reduce the noise emissions of

products, and the economic value of noise

emissions cannot be easily quantified.

While it is generally appreciated that the

absence of noise must have some economic

value, it is difficult to assess this value.

Since the market does not impose severe penalties on the producers of noise, more noise is ultimately emitted than is desired

from society's point of view. This is a situation analogous to other pollution

problems (air, water, etc.) that have

arisen. The final selling prices of noisy

products (or of those whose production

involved significant noise pollution) is frequently lower than it should be and more

of the devices are produced and used than

should (ideally) be. Costs accrue to those affected

by the noise produced in the use and

production processes.

Other economic factors enter into the

estimation of economic benefits of

measurements, factors such as: — relief of the possible necessity of

overdesign of a product to meet some specified noise emission regulation,

provided the measurement uncertainty

is small — the assurance of ability to meet

some specified procurement noise

emission standard, and assurance of

a competitive position in the

marketplace

49
— the assurance that product features

are realized and that proposed

design changes are substantiated by

quantitative data — provided that measurement

uncertainty is small and

. unit-to-unit variability is small,

the manufacturer of a noisy product

may not be required to test 100% of

production, but may rely upon sample

testing, thus lowering the costs of

testing.

3.1.2.3. Example of Economic Cost Benefit

Analysis

Considering material obtained from a recent Environmental Protection Agency

sponsored study of manufacturing costs

associated with noise reduction for mediumand heavy-duty gasoline powered trucks [39],

figure 9 shows the estimated manufacturing

costs to produce vehicles having a given

noise level. The area between the two curves on the graph represents the

uncertainty in the estimates. (These curves

are based upon a very limited number of

points, and a much larger number of data

points, in general, are required to accurately define curves of this sort.) Note

that as the noise emission levels a'e

reduced the costs rise sharply. The rate of

change of this curve (slope) can be studied

to obtain the incremental cost of quieting

($/dB).

3.1.3. Social and Human Impacts

Acoustical measurements are frequently

conducted because of human or, social

interest in sound or noise. For many

reasons, some of which have been previously

indicated, it is difficult to assign

economic value to the measurement process

itself, or indeed, to factors such as the

absence of noise.

The impact of these acoustical

measurements upon our society can perhaps

best be appreciated by realization of the

possible consequences if it were not

possible to perform acoustical measurements.

For example, — it would not be possible to quantitatively assess the impact of

design changes in the process of

product development and the entire

technology of noise control could

not function effectively

— communication system, sound

reinforcement, or entertainment uses of acoustics could" not be improved — perhaps most importantly, the noise

control regulations which did evolve

would have to rely upon qualitative

prohibitions, such as those laws

prohibiting "loud and unnecessary"

noises. Reliance upon such

qualitative descriptors are subject

to appreciable ambiguity and

enforcement can easily become

i nequitabl e.

Acoustical measurements are central to the quantitative assessment of, and

protection against, noise-induced hearing

loss. Hearing loss itself is a topic within

acoustics which is very difficult to describe in economic terms, although there

are undeniable economic aspects to the

subject. For example, the publication

"Hearing Level of Adults" [40] estimates

that in the United States at least 1.2

million persons have a severe hearing

handicap. Costs of disorders of hearing

were recently put at $100 million annually

[41]. This includes direct expenditures for

the education of the acoustically

handicapped, the training of specialists,

and therapeutic measures such as hearing

aids. Reduced earning power is a hidden

indirect cost.

A far-reaching program to protect

against noise-induced hearing loss is that

of the Occupational Safety and Health

Administration. The proposed final standardto protect workers from excessive workplace

noise would set a limit of 90 dB for eight

hours of continuous noise exposure, and

would require employees to provide

audiometric testing for all workers exposed

to eight hour average levels exceeding 85

dB. A tradeoff ratio of 5 dB for halving or doubling of permissible exposure time is

proposed; thus workers can be exposed to levels of 85 dB for up to 16 hours, or to 95

dB for four hours, 100 dB for two hours,

etc. Control of workplace noise is to be

accomplished primarily by engineering and

administrative controls, even if these

controls fail to reduce exposure to within

acceptable limits. As an interim measure,

the use of hearing protective devices is

acceptable, but this usage is regarded as poor industrfal hygiene in view of the

administrative difficulties in requiring

their use, overcoming worker's resistence to use, guarding against improper use and

maintenance, and the hazard posed to the

50
86 ' 84 82 80 78 76 74

A-WEIGHTED SOUND LEVEL* db re 20^Pa

'Measured in accordance with SAE J366a

Figure 9. Estimated additional cost required to attain lower noise levels for medium

and heavy duty gasoline-powered trucks. [39].

worker by being less able to detect audible

signals in his work environment.

As previously noted, the Occupational

Safety and Health Administration has

included provisions for hearing conservation

programs which will include audiometric

testing for all workers exposed for eight

hours to levels of 85 dB or more, and for

those workers who wear personal protective

equipment to reduce their noise exposure.

Reliance is placed upon audiometric testing

to detect changes in workers hearing

thresholds, in order to permit employers to inform those workers of hearing problems

before they become significant. The

standard provides mandatory requirements for

audiometric test rooms and for the

calibration of audiometers, to ensure that

the audiometric environment and techniques

are well standardized and stable. [42]

As a result of the promulgation of the

occupational noise exposure regulations,

there are a number of commercial noise

exposure meters on the market today that

provide a measure of noise integrated (with

appropriate weighting) over a time interval.

The National Bureau of Standards, under the.

sponsorship of the U. S. Environmental

Protection Agency, carried out ah evaluation

program of the devices to assess their

usefulness in moni tori ng 'compl iance with the

regulations. A number of acoustical and

electrical tests were conducted, and the

results are presented in a joint NBS/EPA

report. [28]

A dramatic example of the potential

impact of ultrasonic non-destructive testing

51
can be cited. In the case of the nuclear

powered submarine Thresher, which sank in

1963, possibly due to failure of a silver-brazed saltwater pipe, only 145 of. Thresher's several hundred silver-brazed

pipes were tested with ultrasonics. Yet 14°/ of those tested were found to be faulty

[43]. The possibility exists that the

disastrous loss might have been eliminated

if the ultrasonic testing program had been more extensive, and the results relied upon

for elimination of probable flaws.

3.2. Status and Trends of the Acoustical

Measurement System

If we mainly direct attention to those

acoustical measurements which are primarily

motivated by increasing social concern over

noise, then a growing concern about the

adequacy of noise emission and monitoring

methodologies can be identified. There are numerous identifiable deficiencies in the

organization, structure, and

interconsistency of the relevant acoustical

standards and consequently, the regulations

which utilize such standards.

Inconsistencies result from unnecessary

duplications of effort and needless

insistence upon incorporation of adaptations

to appease special interests. In responding

to what are regarded as emergency situations, mandatory standards are sometimes put

together in patchwork fashion. Participants

in the acoustical measurement system seem to be increasingly aware of the intolerable

nature of this situation, and there appears

to be a growing concern for increased

consistency in the relevant measurement

standards. For example, a report was written by NBS for the Consumer Product

Safety Commission in which the problem of

possible discrepancies among noise

regulations established by different

government agencies is discussed with

suggestions for obtaining uniformity. [44]

However, whether or not the relevant

regulatory agencies participate fully in

this movement for simplification remains to be seen.

There is likewise considerable

duplication of effort in the area of noise

regulation and allocation of regulatory

power. As Mayo and Ware [32] have noted,

"More cities are developing comprehensive

noise statutes. Recent legislation in

Chicago, Minneapolis and New York and

proposed legislation in Boston demonstrate

this. Cities are establishing noise

abatement offices for enforcement purposes.

Local governments are becoming more

sophisticated, replacing subjective

standards with quantitative standards to an increasing extent.

"As with the cities, more States are becoming concerned wi th noise regulation.

States are setting up environmental

departments with authority in the noise area

or adding noise control as one of the

environmental factors to which these

departments should give attention. The

number of noise sources being dealt with by

State regulation is growing. The States are also becoming more sophisticated in their

approach and are substituting quantitative

standards for old subjective limits.

However, in the area of aircraft noise

control, no State seems willing to follow

California's lead. The extreme complexity

of this problem technologically,

economically, legally and politically

discourages State action.

"Under the Noise Control Act, however,

state authority will be limited. States and

cities may not prescribe standards with

respect to new products covered by Federal

regulations unless they are identical to those regulations. However, states and

cities are free to establish and enforce

controls on noise by restricting the use, operation, or movement of any product.

States and municipalities are prohibited

from issuing any noise emission regulations

applicable to railroads or motor carriers

unless the Administrator of EPA and the

Secretary of Transportation determine that

such standards are necessary and that they

are not in conflict with Federal

regulations. ....

"It is a recognized fact that the

existing Federal/State/Local regulatory

relationships are in a situation of

substantial disarray. One outcome of

Federal intervention may likely be a realignment of the Federal /State/Local

regulatory arrangements into a relatively

symmetrical structure of laws, regulations,

and enforcement practices. This could come about in time through the promulgation of

Federal standards, through negotiation among

various jurisdictional levels, through

agreements for Federal support to states and

municipalities, and by court decisions

(where disputes arise) which will,

hopefully, tend to bring the overall

regulatory scheme into coherent and workable

alignrent." [32]

At the present time, NBS interaction

with the Federal agencies responsible for

52
noise abatement measures is quite active and

satisfactory. However, interaction with the

state and local governments is, at best,

sporadic. It is planned to intensify this

relationship in the future.

A current gap in the measurement system

is noted when one considers the measurement

of acoustical properties of architectural

materials and systems. It appears likely

that within the next decade building codes

and procurement policies for large

organizations will frequently include

acoustical performance specifications. In order to satisfy these specifications, it

will be essential not only to conduct many

more tests, but also to devise more satisfactory field measurement test

procedures. New or improved measurement

methodologies are essential to evaluate

noise transmission through the exterior

walls of buildings and for plumbing and

structure-borne sound. If these steps are not undertaken, the present deficiencies in

the measurement system will continue to deteriorate.

It is particularly distressing to realize that the technology of ultrasonic

flaw detection relies heavily upon empirical

data based upon reference blocks which are not adequately specified. This technology

is badly in need of more reliable reference

artifacts, and of more precise means of

system calibration.

Table 8 presents a tabular

representation of some of the factors

entering into discussion of forces for, and

barriers to, both stability and change of

the system.

Because nearly all acoustical

measurements are presently based upon a metric or SI system of units, there will be

negligible impact when the United States

adopts the SI system of units. A possible

exception to this may occur in ultrasonic

non-destructive testing, since there is

strong reliance upon a non-metric system of

reference blocks.

An interesting scenario for the future

can be constructed in consideration of the

implications of the currently proposed

Occupational Safety and Health

Administration regulations described in

Section 2.4.4.5.

For a reference data base, we should

realize that in 1972, between 1.8 and 3.0

million individuals were seen for

audiological services, including hearing

tests. These tests were largely

administered by speech pathologists,

audiologists certified by the American

Speech and Hearing Association, or by

certified audiometric technicians. This

latter category refers to individuals who

can show documentary evidence of the

satisfactory completion of a course of

training meeting, at a minimum, the

standards specified by the Intersociety

Committee on Audiometric Technician Training

[45] or of certification by the Council for

Accreditation of Occupational Hearing

Conservation Technicians.

With the passage of the Federal

Occupational Safety and Health Act of 1970,

noise levels in all industries throughout

the country are limited. According to the

Department of Labor's current Guidelines,

audiometric tests must be made of all

individuals working regularly or infrequently in areas in which the

A-weighted sound level exceeds 90 dB. A current estimate of the number of workers so affected in manufacturing alone is

approximately 2.5 million [46], without

consideration of workers in other noisy

industries, such as construction.

If proposed changes in the Occupational

Safety and Health Administration legislation

take place, the threshold level for annual

audiometric testing will be lowered to 85

dB. This will significantly increase the

number of workers whose hearing must be

measured. There are no satisfactory data

upon the number of workers involved, but two sources within the Occupational Safety and

Health Administration estimated the total

number at between 14 to 40% of those

involved in manufacturing industries. Since

the total number employed in manufacturing

industry is approximately 55 million,

somewhere between seven to twenty million is

the approximate number of required annual

audiograms. Thus this represents

approximately a four-fold to ten-fold

increase. If it proves that as many as twenty million annual audiograms are required nearly one in every ten citizens

will be tested annually, with the con- centration of measurements as high as 4 out

of ten in the manufacturing industries.

In order to conduct these examinations,

there will be a significant increase in the

number of trained audiologists, otologists,

and in the number of audiometers required.

Because of the impact of forthcoming OSHA

regulations, audiometer manufacturers

53
Table 8. Factors related to stability and change.

Stability

Forces

For

Barriers

To

Change

The voluntary consensus standards

writing community which is such

a central element in the system

is inherently a very conservative

apparently democratic institution,

which makes changes occur

more slowly.

The proliferation of inconsistent

measurement standards and metrics

is known to be intolerable, with

the result that some of these

standards will have to be revised

or dropped.

The proliferation of inconsistent

measurement standards may make it

difficult to implement effective

noise control legislation and

enforcement with the result that

in the future there may be little

reliance upon quantitative

characterizations.

The voluntary consensus standards

institutions include among their

members representatives of manu- facturers, trade associations, or testing laboratories who seek to delay

acceptance of measurement methodologies

the adoption of which might prejudice

the economic well-being of that

organization.

anticipate significant increases in annual

sales

.

The problems of providing adequate

audiometric services for compliance with

revised OSHA regulations have been

illustrated by Dr. Allen Cudworth, Vice

President and Director of Research for

Liberty Mutual Insurance Company [47]. Dr. Cudworth indicated that a typical

audiometric examination requires 10 to 20

minutes, so that one can hardly accomplish

more than 20 tests per day per audiometer.

Twenty million audiograms then will require

at least 1,000,000 audiometer days annually.

Because there are probably something like

100,000 work places potentially affected by

the proposed regulations, if each workplace

is to be supplied with its own audiometer,

there will be an extraordinary demand for a large number of instruments, and each

instrument will be utilized for a small

fractional part of the work year. Not only

does this pose unusual production and calibration demands upon the industry, but it

requires that something like 100,000 trained

audiometric technicians be available. A likely solution to this problem will be the use of mobile audiometric units, to best

utilize the available instrumentation and

trained personnel. There are indications

that this will in fact be a characteristic

feature of this portion of the acoustical

measurement system, since the use of these

facilities is currently an element of the

services of an increasing number of noise

control consultants.

Other possibilities for the future

include:

...An emerging technology which may be

limited by measurement capability is that of

ultrasonic non-destructive testing. As practiced now, this technology uses a large

and wide-ranging body of empirical knowledge

which is based on physical phenomena and

scientific principles. The closing of the

gaps between the "clinical" or industrial

practice and the understanding of the

physical processes has been accomplished

only partially -- and then largely only in

defense, aerospace, or nuclear energy

applications. At this time, the better

engineering departments and industrial

laboratories are able to establish and

maintain control of their measurements

within particular manufacturing process

cycles and some entire plants. However,

compatibility in results from measurements

between plants and between companies ranges

from good (at best) to entirely

unacceptable. This situation appears to be one which may be amenable to solutions

through the development and dissemination of

evaluated measurement methodology, wellcharacterized physical standards, and

reliable technical data.

...Because of the many possibilities for

54
error which may occur with the operation of

complex instrumentation systems, it appears

likely that automated systems for the

calibration of measurement instrumentation

win be developed for use by the larger

acoustical laboratories. In addition,

automated noise monitoring systems such as that developed for the Department of Housing

and Urban Development by NBS and several

systems presently available on the

commercial market for less complex

measurements will be more widely used.

Automated systems for the performance and

analysis of audiometric tests will also be

devised.

...Several technologies will become more measurement intensive within the foreseeable

future. These include: — environmental noise monitoring — audiometric examinations — applications of ultrasonics, such as ultrasonic flaw detection.

4. SURVEY OF NBS SERVICES

4.1. The Past

During World War I, acoustic transducers

were developed and the study of underwater

sound ranging received much attention. (At

the National Bureau of Standards, this work

led to the establishment of the Sound

Section which was formally integrated into

the Institute for Basic Standards.)

In a 1966 editorial in the Journal of

the Acoustical Society of America, [48]

noting the dedication of the NBS

Gaithersburg Laboratories, Editor-in-Chief

Dean R. B. Lindsay said in part,

"...The Sound Section, familiar to all

readers of this Journal, has during its

existence corcerned itself with every

branch of acoustics recognized in our

Index Classification save music and

bioacoustics . It has, in particular,

done calibration, audiology, vibration

measurements, long-range propagation in

the atmosphere, and magnetic recording,

as well as attenuation and dispersion in

gases."

In 1972, the Applied Acoustics Section

(formerly the Applied Acoustics and

Illumination Section, Center for Building

Technology, Institute for Applied

Technology) was transferred into the

Institute for Basic Standards. The Applied

Acoustics Section has concerned itself with

a number of acoustical problems, principally

those dealing with the technology of noise

measurement, monitoring and control.

Significant contributions to the data bases

on truck and portable air compressor noise

as well as several new innovations in

instrumentation systems for the acquisition

and interpretation of environmental noise

data have been accomplished. Attention has

also been directed to study of the adequacy

of present measurement methodologies for the

determination of noise emission from several

noise sources, and to assess the acoustical

properties of building systems.

Research elsewhere at the National

Bureau of Standards, e.g., in such diverse

fields as vibration measurement, rheology,

instrumentation, engineering mechanics,

statistics and digital signal processing,

while not directly relevant to acoustical

measurements, have made significant

contributions to facilitate and further the

understanding of the basic physics which

underpins all acoustical measurements and

analytical procedures.

Table 9 summarizes the published output

of NBS in this field as of December 1972.

Additional publications by current staff

members who were not employed at NBS at that

time, or were conducting research in other

fields, are numerous, but are omitted. The

papers cited are those published in archival

journals by present staff members. Letter

reports and other minor reports are omitted.

4.2. The Present Scope of NBS Services

4.2.1. Description of NBS Services

4.2.1.1. Support of The International

Measurement System

There are two principal activities by means of which NBS provides support to the

international measurement system. An important activity in this context is active

participation in the relevant committees of

the International Organization for Standardization (ISO) and the International

El ectrotechni cal Commission (lEC).

Throughout the past and to the present day,

NBS has had active representation on these

committees. At the present time NBS staff

members hold the following committee

assignments. — Secretary of the U. S. Technical

Advisory Group (E33.06) to IS0/TC43/

Subcommittee 2 (Building Acoustics)

55
Table 9. NBS publication output in the field of acoustics.

Books and Chapters in Book

R. D. Berendt, G. E. Winzer, and C. B. Burroughs, "A Guide to Airborne, Impact,

and Structure Borne Noise Control in Multifamily Dwellings" (1968).

E. B. Magrab and D. S. Blomquist, "The Measurement of Time-Varying Phenomena"

(1971).

M. Greenspan, "Transmission of Sound Waves in Gases at Very Low Pressures",

in "Physical Acoustics", Vol. IIA, W. P. Mason, Ed. (1964).

R. K. Cook, Section Editor, "Acoustics", in "American Institute of Physics

Handbook", 2nd ed. (1963), 3rd ed. (1972).

M. Greenspan, "Acoustic Properties of Liquids", in American Institute of Physics

Handbook", 2nd ed. (1963), 3rd ed. (1972).

M. Greenspan, "Translational Dispersion in Gases", in "Dispersion and Absorption

of Sound by Molecular Processes" (1963).

M. Greenspan, "A Sing-Around Velocimeter for Measuring the Speed of Sound

in the Seg", in "Underwater Acoustics", V. Albers, Ed. (1963).

t R. K. Cook and P. Chrzanowski, "Transmission of Airborne Noise through Walls

and Floors" in Handbook of Noise Control", C. M. Harris, Ed. (1957).

M. Greenspan, Articles: "Damping"^ "Forced Oscillation"; "Impedance, Mechanical";

and "Lissajous Figures" in "McGraw-Hill Encyclopedia of Science and Technology"

(1960) (Also in 2nd and 3rd ed.)

Papers and Reports

Subject Papers (No.) Reports (No.)

Theory, including propagation and .13 2 diffraction

Architectural acoustics and noise 17 22

Speech and hearing, including 21 87

hearing aids, audiometry,

loudness

Electroacoustics , including micro- 22 10

phones, sound recording,

instrumentation

Communication theory 6 2

Physical acoustics, including 24 33

ultrasonics

Vibration 15 5

118 161

56
— Member of Working Group 6 "Noise

Emitted by Machinery and Equipment"

under IS0/TC43/SubconTni ttee 1 (Noise) — Member of Working Group 5 "Noise

Emitted by Ships and Railways and

Noise Inside Vehicles" under

IS0/TC43/Subcommittee 1 (Noise) — Member of ad hoc croup of

IS0/TC43/SC1 for "CTassification of

Machinery and Equipment with respect

to the Noise Emission." — Member of Working Group 2 "Free-Field Calibration of

Microphones" for IEC/29/SC29

Another activity which provides support

to the international measurement system is

through exchange of technical publications,

by attendance at international conferences,

symposia, etc., and by discussions with and

visits to the facilities of foreign

standards laboratories. As a specific

example of such support, the National Bureau

of Standards hosted the meetings of

IEC/TC29, its Subcommittees and Working

Groups, and as well, the meetings of

IS0/TC43/SC1 and its working groups in April

1976.

4.2.1.2. Participation in Standardization

Organization Activities

Participation of NBS staff members in

the national voluntary concensus standards

organizations Is documented in table 10,

which shows the names and titles of the

relevant corrimittees in which NBS staff

members participate. It is the concensus of

the NBS staff members who belong to these

committees that the corrmittees are currently

quite active and productive, and that it is

a worthwhile endeavor for NBS to be involved

in.

4.2.1.3. Development of Measurement Methods

The result of NBS research activities is

frequently the development of measurement

methodologies. These outputs have

traditionally been an area in which NBS has

provided leadership. Typically, the first

output of NBS research or measurement

expertise is the conception of a measurement

methodology, a data base is then obtained

with the implementation of the measurement

methodology, and ultimately, the improved,

tested, and proven measurement methodology

Is accepted within the standardization

community. Section 4.2,1,4. describes some current NBS activities related to measurement methodology and the provision of

data bases; the following sections describe

some prior activities resulting in accepted

measurement methods.

Measurement of sound pressure: In the

late 1930's, an investigation Into the basic

physics of how a fluctuating sound pressure,

acting on a microphone, is converted by the

latter into fluctuating electrical voltages

and currents was carried on. The resulting

technical scheme is now known as the

reciprocity method for calibration of

microphones. The basic description of the

method was published in appropriate

scientific and engineering journals.

Shortly, it became apparent that several

methods for calibration of microphones were being used, including the reciprocity

method. The systematic differences in the

results of the several methods forced a decision to select a single standard method

for such calibrations that would furnish the

most accurate scheme for arriving at absolute measurement of audible sound

pressure. Agreement on a single method

would lead to compatibility in data obtained

in various laboratories with different

instruments. A technical committee of the

American National Standards Institute was appointed. This corrmittee was made up of

acoustical experts and included NBS

representation. In due course, the

reciprocity method was agreed upon and an American Standard Method for Calibration of

M1crophones[9] was approved and is widely

used.

Measurement of sound pov/er: The

absolute measurement of the total amount of

acoustical power radiated by sound sources

such as houshold appliances, gasoline

engines, etc., is only partially achieved in most cases. The total radiated power is important because it governs, to a large

extent, how much annoyance is created by the

noise. Such acoustical powers are relatively small, frequently less than 1 watt, and therefore require special

facilities for measurement.

In the late 1940 's, NBS modified its

reverberation chamber facilities for

measurement of such powers. This facility

had been set up in the 1920's for measuring

the absorption coefficients of the

newly-invented acoustical materials used to control sound and noise in offices, shops,

public buildings, etc. An investigation

57
Table 10. Participation in national standards organization activities.

Organi zation

Audio Engineering Society

American National Standards

Institute

Acoustical Society of America

American Society for Testing

and Materials

Committee, Sub-Committee, or Working Group Title

-- "Stethoscopes Committee" (member)

Acoustics Technical Advisory Board

(2 members)

Committee SI : Acoustics

-- 45 Sound Level Meters and

Their Calibration (member) — 54 Standard Microphones and

Their Calibration (member)

-- SC57 Attenuation of Sound in

Air (member) — 61 Evaluation of Absorptive

Wedges and Anechoic Rooms

(member)

Committee S3: Bioacoustics — 35 Audiometers (member) — 37 Coupler Calibration of

Earphones (member)

-- 43 Method of Calibration of

Bone Vibrator (members)

-- 43 Artificial Head-Bond (member) — 48 Hearing Aids (member)

-- 51 Auditory Magnitudes (member)

Committee S4: Sound Recording (member)

Acoustical Society of America

Committee on Standards (2 members)

Working Group 3: Motor Vehicle

Engine and Tire Noise (member)

Committee E18: Sensory Evaluation of

Materials and Products (member)

Subcommittee 04: Psychophysical

Measurement of Environmental

Pollution (member)

Committee E-33: Environmental Acoustics

(3 members)

-- Subcommittee .01 "Sound Absorptions" (3 members) — Subcommittee .03 "Sound Transmissions" (3 members) — Subcommittee .06 "International

Standards" (member) — Subcommittee .08 "Mechanical and

Electrical System Noise" (member)

Institute of Electrical and Electronic

Engineers

Society of Automotive Engineers

58

-- Standards Committee 6-AE "Earphone

Measurements" (member)

-- Committee A21 Aircraft Engine Noise — Subcommittee: "Subjective

Evaluation of Flyover Noise"

(member)

-- Committee "Vehicle Sound Level"

-- Subcommittee "Instrumentation"

-- Ad hoc Group on "Vehicle Noise

Test Environment" (member)

-- Monitoring Panel for Audible

Warning Systems (member)
into the use of such chambers for sound

power measurement was launched in the early

1950's. The electroacoustical facilities

were modified so as to incorporate the

absolute sound pressure measurement

capability, which came from the reciprocity

method (see Section 4.2.1.4.1.). The

results of the first researches led (a) to a scheme, using the measurement of correlation

coefficients for sound fields in

reverberation chambers, for arriving at an estimate of the state of diffusion in the

chamber, and (b) to an estimate of the errors in measurement of sound power arising

from the arbitrary method used to sample the

sound fields in the chamber.

The technical problems connected with

achieving a diffuse field, and with sampling

the sound pressure of the diffuse field, were substantial enough to require

continuing research into the acoustics of

reverberation chambers to the present day.

The most recently accepted standard for

the measurement of sound power is American

National Standard Methods for the

Determination of Sound Power Levels of Small

Sources in Reverberation Rooms, SI. 21-1972

[49j. This standard, as now embodied,

represents a major advance in the

state-of-the-art of reverberation room measurement of sound power. It incorporates

the best currently available interpretation

of measurement technology which is the

subject of ongoing research. However, in

order to identify additional analytical and

experimental information needed for further

refinement of this standard, NBS sponsored,

under contract, a critical review of this

standard which was published in May 1974, as NBS Technical Note 841 [50]. The report was made available as a relevant conmentary on the state-of-the-art and in the interests of

an open exchange of information.

Miscellaneous acoustical measurement

methods: The widely used American Society

for Testing and Materials method of test for

airborne sound transmission [16] loss is a direct outgrowth of NBS research several

years ago [34,35,36].

The Consumer Product Safety Cormission

(formerly the Bureau of Product Safety of

the Food and Drug Administration, HEW)

issued regulations on the allowable noise

levels from toy cap guns. Manufacturers and

their consultants were found to be using

inappropriate measuring techniques, leading

to very large (40 decibel) errors in the

measured peak sound pressure levels. NBS

rectified this situation by carrying out

laboratory measurements and then, based on these measurements, prepared for Consumer

Product Safety Commission performance

specifications for the measurement systems

[51], which led to suggested measurement

methodologies for measuring the noise of

paper caps [52] and toy guns [53].

Using an acoustic coupler which was developed at NBS more than thirty years ago,

and a standardized procedure, NBS offers a service for the calibration of audiometric

earphones. Such a calibration procedure is

critical to the calibration of all hearing-test devices.

NBS has had a continuing program with

the Veterans Administration (VA) to determine numerous electrical and acoustical

characteristics of hearing aids. Though a discussion of the properties of these

devices, and description of the nature of

these measurements, is beyond the scope of

this report, the complete results of these

tests are published annually in a document

published by the VA and which is obtainable

from the U. S. Government Printing Office.

Current work is now devoted to developing

test methods to determine the acoustic

response of two new types of hearing aids,

the directional hearing aid and the open-ear

mold or high-pass hearing aid.

NBS is presently in the midst of a major

effort to determine the electrical and

acoustical properties of sound level meters

in a variety of physical environments and to devise a standard calibration procedure to verify that sound level meters meet the

relevant (usually ANS SI. 4-1971)

specifications. It is anticipated that a calibration/evaluation service will be

offered to government and industry within

the near future.

4.2.1.4. Provisions of Reference Data

The principal means by which NBS

provides reference acoustical data is

through the technical reports on its

research studies and by participation in

national and international acoustical

measurement round robins. Several

significant accomplishments can be cited as examples of these services.

1. Truck tire noise: At medium to high

speeds, the noise from tires predominates

provided the truck has a reasonably good

exhaust muffler and is in a good state of

repair. Users and manufacturers of truck

59
tires, state lawmakers and enforcement

agencies, and urban planners have been

hampered in their noise abatement efforts by

the lack in the public domain of an information base of tire noise data. An NBS

research program, which served as the basis

for the test procedure adopted by the

Society of Automotive Engineers [54], is one facet -- along with the diesel truck

demonstration project, truck muffler

optimization program, and the

training/equipping project -- of the

Department of Transportation program in

surface transportation noise aimed at

nationwide highway vehicle noise

enforcement.

2. Interior/exterior noise of

over-the-road trucks [55]: On November 7,

1970, the Bureau of Motor Carrier Safety

(BMCS), issued an Advanced Notice of

Proposed Rulemaking Concerning Vehicle

Interior Noise Levels. A total of forty

responses to the docket was received;

however, they provided little real data on the level and effect of in-cab noise on drivers hearing and less yet comparing

improvements in interior noise levels to decrease in exterior noise levels.

Therefore, in order to develop a factual

information base regarding the noise levels

of typical over-the-road trucks, NBS

conducted a data base measurement program,

the output of which includes:

a. Initial data which formed the basis

for the BMCS regulations on vehicle

interior noise levels.

b. The idle-max-idle stationary test

procedure developed during this

program hab been utilized by the

Environmental Protection Agency as one of the test procedures in their

Interstate Motor Carrier Noise

Regulations

.

c. The experience obtained during the

conduct of this program allowed NBS

to develop an appropriate

measurement methodology which can be

used by the Environmental Protection

Agency in their Noise Emission

Regulations for New Medium and Heavy

Duty Trucks [56].

3. Railroads: NBS evaluated various

measurement methodologies and data

processing algorithms as to their

appropriateness in characterizing the noise

generated by rail line and yard operations,

including the noise of retarders [57].

These data, in conjunction with data from

other sources, provide the technical basis

for the Environmental Protection Agency

Interstate Rail Carrier Noise Emission

Regulations. The study was prompted by lack

of data on the noise levels associated with

railroad operations, which necessitated the

establishment of a data base prior to Federal rule making in this area.

4. Noise of portable air compressors:

The Environmental Protection Agency has

identified portable air compressors as a major source of noise pollution. As part of

a study of procedures for the equitable

determination of noise output, the sound

power levels associated with seventeen

different portable air compressors were determined in an extensive field measurement

program. The resultant data, together with

data from several other sources provides a technical basis for evaluation of

measurement procedures for stationary noise

sources. [58]

4.2.1.5. Provision of Reference Materials

Because of the fact that the use of

reference materials is relatively unusual in

acoustical measurements, the role of NBS in

provision of these materials is modest.

A significant exception, however, is in

the technology of ultrasonic flaw detection.

In this technology, since reliance is often

placed upon reference blocks for system

calibration, NBS has recently evolved a program directed toward the study of the

adequacy of ultrasonic reference artifacts.

This research will utilize the current

American Society for Testing and Materials

standards to determine the size of already

wel 1 -characteri zed flaws, initially starting

with fatigue cracks in standard fracture

specimens. The ultimate goal of this

research is to devise, improve and

disseminate the measurement techniques,

standards, and test methods for

acoustic-based nondestructive testing; and

to facilitate, establish and maintain

comparability between measuring systems to assure compatabi 1 ity of data resulting from

inspections of the same product at different

locations. As an element in this program it

is likely that the present reference block

system will either be more tightly

characterized, or replaced with a more satisfactory system.

60
4.2.1.6. Support of Science, Education and

The Dissemination of Knowledge

There are several direct interactions

which NBS acoustics activities have had, and

continue to have with the educational

system. These affect all levels of

education, and include: — provision of training as laboratory

aides for high-school science

students — provision of research experience for

high school science teacher programs

leading to the M. Ed. degree — presentation of invited lectures at colleges and universities — support of research through a grant

to a university on the subject of

reverberation room acoustics — support of the research of National

Research Council post-doctoral

research associates.

These interactions serve to disseminate

knowledge about acoustics and at the same

time infuse new ideas and fresh approaches

into the research programs.

An additional service provided to make

possible the dissemination of knowledge is

through technical publications. As indicated in Section 4.1., NBS researchers

have numerous publications in acoustics. At

the present time, NBS researchers serve not

only as authors and reviewers, but a staff

member presently serves as Associate Editor

for Noise fo>" the Journal of the Acoustical

Society of America, and on the editorial

board of the Journal of Noise Control

Engineering.

4.2.1.7. Existing Measurement Capabilities

The acoustical measurement capabilities

presently existant at NBS include but are

not limited to the following principal types

of acoustical measurements: — precision microphone calibration,

(reciprocity method) — measurement of sound pressure level — in a free field (anechoic)

envi ronment — in a semi -anechoic (free-field over reflecting plane)

environment (limited to field

measurements) — measurement of sound power emissions — inferred from... anechoic

... semi -anechoic

(field)

... reverberation

room data — measurement of environmental noise — through the use of instrumented

. and microcomputer data

processing facilities — through the use of special

purpose noise monitoring systems — measurement of the sound attenuation

properties of ear protectors — measurement of the acoustic

pressures produced by audiometric

earphones — measurement of acoustical absorption

properties — using the reverberation room method — using the impedance tube method

4.2.1.8. Role in the Dissemination and

Enforcement Network

At the present time, NBS provides a reciprocity calibration service for

precision condenser microphones, provided

that they are made to be used with the

standard calibrating couplers described in

American National Standard SI. 10-1960 [9].

Table 11 indicates that the users of this

service include not only manufacturers of

acoustical measurement equipment, but also a wider range of participants in the

infrastructure. Many of the companies send

microphones to NBS for calibration once a year.

Present plans for the NBS program call

for the extension of calibration services

possibly to include determination of such

factors as compliance with performance

specifications ("type testing") of sound

level meters or integrating sound level

meters

.

61
Table 11. Users of microphones submitted

to NBS for calibration.

Type of Industry Examples

Manufacturers of Sound

Measurement Equipment

Aerospace Industry

Manufacturers of

Audio Equipment

Department of

Defense

Other Government

Agencies

Automobile

Manufacturers

Equi pment

Manufacturers

Acoustical Consultants

Universities

Manufacturers of

Audiometric Equipment

General Radio Co.

B & K Instruments, Inc. Hewlett Packard Co.

Boeing

McDonnell Douglas

Lockheed

Rockwell International

Pratt & Whitney

General Dynamics

RCA Laboratories

CBS Laboratories

Electro-Voice, Inc. Dictaphone Corp.

U. S. Naval Weapons Eng.

Support Activity

Newark Air Force Station

Wright-Patterson AFB

Redstone Arsenal

NASA: Marshall , Goddard,

Kennedy

,

Langley, Houston,

White Sands

HEW Dept.

Labor Dept.

Transportation Dept.

Agriculture Dept.

General Motors Corp.

Ford Motor Co.

General Electric Co. Westinghouse Corp.

Rohr Corp.

Bendix Corporation

Wyle Laboratories

Bolt Beranek & Newman

Western ElectroAcoustic Labs

Sandia Corp.

Pennsylvania State

University

Roanwell Corp.

Instrument Systems Corp.

62
With the increased use of audiometers as diagnostic instruments which is projected

for the near future, it would be desirable

to develop a measurement assurance program.

This program shojld include all the

laboratories presently calibrating

audiometers as well as those to be

established in the near future. Analysis of

the precision and accuracy of these

calibrations should be very significant in

indicating improvements to the system. NBS

participation ideally should involve

participation with other agencies such as the Occupational Safety and Health

Administration, which is now in the process

of accrediting laboratories. Factors such

as a round robin to deal with the subject of

earphone calibration, requirement of the use

of an insertion technique, the effects of

operator testing, skill or technique, and an educational program would be involved.

Relationship to lower echeleon

calibration and testing laboratories: This

subject is discussed in some detail in

Sections 2.4.3.1. through 2.4.3.5. The

principal NBS interaction with these

laboratories is through the common

professional affiliations of the NBS staff

members and the laboratory staff members in

the relevant professional societies and in

service on the voluntary consensus standards

groups. There is not at present, and has

not been, any extensive program of review of

the facilities and capabilities of these

laboratories. However, a survey of the

capabilities of some of these laboratories

on a limited number of acoustical

measurement-related topics will soon be

initiated with the cooperation of the

Institute for Noise Control Engineering.

Relationships to regulatory agencies:

NBS provides technical support and

assistance to regulatory agencies with

emphasis on: — developing improved measurement

procedures

,

— establishing and/or validating data

bases

,

— evaluating performance of

commercially available acoustic

measurement instrumentation, — developing new instrumentation.

In some areas, NBS support services are authorized or mandated by specific

legislation, such as the Noise Control Act

of 1972 or the Consumer Product Safety Act. Through participation in interagency

research panels and interaction with

regulatory agency personnel at the planning

and decision-making level, NBS assists

regulatory agencies in defining their future

research programs by identifying areas where

the promulgation of regulations or the

ability of industry are hindered by a lack

of accurate measurement procedures or data.

The principal regulatory agencies with

which NBS has active interrelationships are those described in Section 2.4.4.1.3. and

Appendix C, and include the Department of

Transportation, Consumer Product Safety

Commision, Department of Housing and Urban

Development, and the Environmental

Protection Agency.

4.2.1.9. NBS Input/Output for National

Measurement System/NBS Interaction

Figure 10 illustrates the nature of the

input/output process characteristic of the

National Measurement System/NBS interaction.

It is seen that the elements in this

interactive process can be categorized as

fol lows

... Standards organizations

... Industrial

. . . Federal and State governments

... Professional activities

... Foreign laboratories

Each of these elements has a dual role -- as

a source of information or material to NBS

participants, and as a recipient of NBS data

or NBS measurement expertise. It is instructive to briefly consider the elements

in some detai 1

.

Estimates of representative fractional

total manpower concerned with each form of

identified output are shown in figure 10.

The relevant standards organizations

with which NBS acoustics staff members have

active involvement are listed in tables lo

and 12. NBS staff members serve in various

capacities in these organizations, and

frequently serve as chairmen of committees,

sub-committees, or working groups for the

development of standard test methods.

Numerous interactions with industrial

groups can be cited. While it is

inappropriate to cite individual

manufacturers or individual colleagues, the

industries they represent complement those

identified as members of the trade

63
INPUT

Figure 10. NBS input-output chart showing the interaction between NBS and elements of

the acoustical measurement infrastructure.

associations explicitly cited in table 12.

It should be noted that these groups include

producers of a wide variety of noise

emitting products. Recently, in

establishing a measurement methodology for

noise source characterization, valuable

input was provided by meeting with these

groups, to cite but one example.

Interactions with elements of Federal

and state governments are numerous, and

these are listed in table 12. Details on the nature of the interactive processes are indicated in other sections of this report.

Additional input to the NBS work in

acoustics also comes from other groups

within NBS. In particular, interactions

with the Sensory Environment Section, Center

for Building Technology, Institute for

Applied Technology, are active and

extensive.

Professional activities provide another

valuable interaction. These professional

activities consist of participation in the

meetings of relevant professional and

scientific societies, special symposia,

preparation and review of papers published

in technical journals, and meetings with

faculty and staff members of various

universities. Specific elements of these

professional activities are listed in table

12.

Activities of foreign standards and

research laboratories are important sources

of input to the National Measurement System.

In the context of interaction with NBS work

in acoustics, the specific foreign

laboratories listed in table 12 are cited.

It is, of course, important to determine

the probable structure of the total

input-output interactive process for the

64
Table 12. Participants in the National Measurement System/NBS interaction.

Standards Organizations

American National Standards Institute (ANSI) American Society for Testing and Materials (ASTM) Society of Automotive Engineers (SAE) International Organization for Standardization (ISO)

IndustryTrade Associations

Acoustical and Insulating Materials Association (Alf'tA) Air Conditioning and Refrigeration Institute (ARI) American Road Builders Association (ARBA) American Short Line Railroad Association (ASLRA) American Trucking Associations (ATA) Association of American Railroads (AAR) Association of Home Appliance Manufacturers (AHAM) Construction Industry Manufacturers Association (CIMA) Engine Manufacturers Association (EMA) International Snowmobile Industry Association (ISIA) Motor Vehicle Manufacturer's Association (NVMA) National Electrical Manufacturer's Association (NEMA)

Individual Manufacturers Colleagues in Industry

Federal and State Governments

Federal Government

Consumer Product Safety Commission (CPSC) Department of Agriculture (DOA) Department of Defense [Air Force, Army, and Navy] (DOD) Department of Health, Education and Welfare (HEW) Department of Housing and Urban Development (HUD) Department of Interior (DOI) Department of Labor (OOL) Department of Transportation (DOT) Environmental Protection Agency (EPA General Services Administration (GSA) National Aeronautics and Space Administration (NASA)

State Governments

Cal ifornia

111 inois Maryland

New York

NBS Sensory Environment Section, Center for Building Technology,

lAT (463.03)

Professional Societies

Acoustical Society of America (ASA) Audio Engineering Society (AES) Institute of Electrical and Electronic Engineers (IEEE) Institute of Noise Control Engineering (INCE)

Technical Journals

IEEE Transactions on Audio and Electroacoustics

IEEE Transactions on iilLrasonics Journal of the Acoustical Society of America

Journal of the Audio Engineering Society , Journal of Noise Control Engineering

Journal of Applied Acoustics

Journal of Sound and Vibration

Universities

Catholic University Massachusetts Institute of Technology

North Carolina State University

Pennsylvania State University

Purdue University

University of Houston University of Pittsburgh

University of Texas (Austin) University of Wisconsin (Madison)

Foreign Laboratories Building Research Establishment (BRE) [England] Centre Scientifique et Technique du Batiment (CSTB) [France] Institute of Sound and Vibration Research { ISVR) [England]

National Physical Laboratory (NPL) [England]

National Research Council (NRC) [Canada]

Physical isch-Technische Bundesanstal t (PTB) [W. Germany]

Technical University of Denmark (DTH) [Denmark]

65
entire National Measurement System

infrastructure concerned with acoustics.

The essence of this process is given in Section 2.5.

4.2.2. Users of NBS Services

Indications of the nature and

composition of the primary users of NBS

services can be obtained by study of

previously presented material. In particular, the NBS Input/Output Chart

categorizes the output into the following

categories: — Standards Organizations — Industry — Federal and State Government — Professional Activities — Foreign Laboratories

The standards organizations rely upon the

acoustical measurement expertise of NBS

personnel and upon the participation of NBS

laboratory activities in their measurement

round robin programs, and, perhaps most

significantly, upon the NBS basic research

efforts directed toward the relevant

physical phenomena.

Industry makes use of NBS acoustical

measurement expertise in the development of

measurement methodologies and through the

use of NBS measurement services. Table 12 indicates the range of industrial trade

organizations which have met with NBS

personnel within the recent past, and table

11 (Section 4.2.1.9.) illustrates the nature

of the users of the NBS precision microphone

calibration services.

The nature of the NBS relationship with

Federal regulatory agencies is described in

Section 4.2.1.8. At the present time, there

have been several inquiries from

representatives of state governments for

assistance with regard to acoustical

measurements. These inquiries have included

discussion of such general topics as laboratory accreditation, round-robin

inter-laboratory checks, and the evaluation

of the performance of measurement

instrumentation. Specifically the

discussions have indicated that their major

problems are with sound level meters and

graphic level recorders. These problems

are:

... there is no place where they can have instruments tested by an independent agency to ascertain

their conformance with applicable

standards (e.g., American National

Standard SI. 4-1971 [11]);

... American National Standard SI. 4 does

not adequately specify the

capabi'lity of sound level meters to handle high crest factor (peak to rms value) signals;

... the transient response of graphic

level recorders does not conform to specifications for sound level

meters, so data obtained on different instruments are not

comparable.

Professional activities, other than

participation in the standards committees

and in the dissemination of knowledge,

include the publication of research findings

and the scheduling of conferences and

meetings directed to the subject of

acoustical measurements. As an example of

such activities, NBS co-chaired the 1974

Arden House Workshop on Noise Control

Engineering with the Institute of Noise

Control Engineering. This conference

specifically directed attention to the

subject of accuracy and precision in

acoustical measurements.

Because of NBS activity in fundamental

acoustical measurements such as precision

microphone calibration and in audiometric

measurements, the indirect users or beneficiaries of NBS activities include

nearly everyone who makes use of acoustical

measurement instrumentation or benefits from

the implementation of noise control or hearing conservation measures.

Two types of "non-clientele" who would seem to have reason to be clientele can be

identified. These include some Federal

agencies with which NBS has only a weak

inter-relationship (such as Occupational

Safety and Health Administration) and some manufacturers of acoustical materials used

for noise control purposes. The

relationships with the Occupational Safety

and Health Administration are weak

principally because the Office of Research

and Standards Development of the National

Institute for Occupational Safety and Health

was mandated to have primary responsibility

for development of the recommended

Occupational Safety and Health

Administration standard for exposure to noise, and therefore, employ their own scientific staff to carry out this mandate.

Manufacturers of acoustical materials rely

principally upon independant testing

laboratories for their acoustical

measurements, and are often less critically

concerned with the measurement process per

se than in the acoustical, mechanical.

66
aesthetic, and economic properties of their

products. It may be that the apparent lack

of concern with the possible inadequacies of

the measurement process is because the

acoustical properties are often, in

practice, secondary to aesthetic,

mechanical, or economic factors.

4.2.3. Alternate Sources

Some calibration services comparable to those presently provided by NBS can be

obtained from acoustical consultants or from

independent testing laboratories. In some cases, these laboratories also provide

measurement services no longer rendered by

NBS, but which were at one time provided by NBS. More extensive discussions of this

factor are presented In Section 4.3.3. The

NBS relationship with the personnel of these

alternate suppliers is principally through

comion professional society activities and

in service in the voluntary consensus

standards groups.

An identifiable user need not at present

being met is the provision of calibration

services for sound level meters and noise

exposure monitors. There is increasing

Interest In the provision of such a service

and present NBS plans call for expansion of

the NBS program to provide such a calibration service. There are, however,

indications that another Federal agency may

intend to provide such a service in the

relatively near future. Because these

measurements are extremely complex and

require appreciable expertise in acoustical

measurements, such as is presently available

at NBS, it will remain to be seen whether

other Federal agencies will be able to acquire the essential facilities and

experienced personnel to provide adequate

services

.

4.2.4. Funding Sources for NBS Services

There are three principal sources of

funding for NBS acoustical measurements

work. These sources are: — other Federal agency monies — test and calibration fees — scientific and technical research

service funds

The principal sources of other agency

monies are agencies such as — Department of Transportation — Department of Housing and Urban

Development — Consumer Product Safety Commission

— Environmental Protection Agency — Postal Service.

In general the other agency monies are obtained either as agreed upon In the terms

of Interagency agreements, as reimbursable

projects, or as contracts. The agreements

or contractual terms typically require

written reports to the sponsoring agency;

permit NBS to purchase essential

instrumentation and (frequently) to retain

this instrumentation upon completion of the

contract; and encourage open publication of

the results of the measurements or provision

of the measurement service in the

1 Iterature.

There are certain constraints connected

with the acceptance of other agency orders

and monies. These are Intended to define

such factors as whether or not traceablllty

of the measurements to national standards

may be Important, whether the private sector

cannot or will not develop appropriate test

methods, whether contracts placed outside

the Federal government would result in an unavoidable conflict of Interest, etc.

Test and calibration fees are paid

according to established fee schedules, and

result in the provision of calibration data

reports to the client.

Scientific and technical research

service funds are those monies appropriated

by Congress to NBS to support ongoing NBS

programs

.

4.2.5. Mechanisms for Supplying Services

The following serve as the mechanisms by

which NBS supplies its services: — performance of calibration

measurements — publications, Including: — articles in technical journals

and magazines — NBS reports — talks to various groups, including: — professional societies — trade associations — university sponsored seminars — representatives of state and

local governments — meetings with:

67
— other Federal agencies — trade associations — standards associations — representatives of foreign

laboratories

.

4.3. Impact of NBS Services

4.3.1. Economic Impact of Major User

Classes

As indicated in earlier sections of this

report, the major users of acoustical

measurements include the manufacturers of

noisy (or noise-control related) products

and regulatory agencies. The extent and

nature of use by all of the participants in

the measurement infrastructure is not well

understood at present, and the economic

impact of the major user classes is

correspondingly not well understood.

Detailed study by trained economists is in

order. The information presently available

is fragmented, inadequately detailed, and to some extent irrelevant. Some of the varied

elements in this situation include the

following typical considerations, indicating

the range of impacts to be observed. — A recent economic study carried out

for the Occupational Safety and

Health Administration [59] estimated

that it would cost American industry

$13 billion dollars to achieve com- pliance, insofar as technology

permits, with present Occupational

Safety and Health Administration

regulations permitting workers an 8-hour exposure at 90 decibels. The

same study indicated that it could

cost an additional $8 billion to achieve compliance with an 85-decibel regulation. Thus one can estimate that the cost of reducing

industrial noise in the United

States by only one decibel could be

on the order of $1.5 billion

dollars. If only a fraction of the

measurements made were in error on the high side, industry could spend

vast amounts of money on needless

noise control. On the other hand,

measurements which are erroneously

low can result in an increased

number of workers suffering a hearing handicap. Furthermore, such

measurement errors can lead to costly and time-consuming arguments

between regulatory agencies and

industry. — A recent article [60] indicated that

there are 23 manufacturers of

audiometers, 18 of which are in the

United States. A survey of the five

major manufacturers indicated that,

in 1972, sales of audiometers in

this country totalled between $4.2

and 7.2 million. -— A study conducted in 1969 [61]

documented $15 million spent on ultrasonic equipment in 1969, and

projected an annual growth in this

field of 15%, with a 1980 market

volume of $70 million. A survey of

various manufacturers estimated the

1973 total sales in ultrasonic

equipment of $25 -30 million. Of

this, approximately $5 million was for transducers (which, at a unit

cost of $200 implies 200,000

transducers sold annually), and

approximately $15 million was for

ultrasonic flaw detectors (which at approximately $5000 each implies

3000 instruments sold). It is

estimated that, for the

international market, these figures

would be doubled.

In summary, the economic impact of major

users in the acoustic measurement system is

poorly understood, but, nevertheless, is an important subject. The authors were uncomfortable with the economic information

presented, but these were considered to be

the best examples available. Obviously, a need exists to obtain more concrete and

definitive economic information on this

topic. To help remedy this situation, NBS

has awarded a contract to a major acoustical

consulting firm to prepare a definitive

study on the economic impact of acoustical

measurements

.

4.3.2. Technological Impact of Services

The major technologies presently

supported by NBS acoustical measurement

services are those concerned with the

implementation of noise control legislation

and engineering, with hearing conservation

programs, and with the relevant basic

physical phenomena. These technologies and

their concern with acoustical measurements

are described in Sections 2.1., 2.2.2., and

3.1.1. NBS support is indicated in Section

4.2.1.

4.3.3. Pay-off From Changes in NBS Services

The NBS acoustical measurements

facilities at the previous site in

68
Washington, D. C. included tKe facilities

required to perform airborne sound

transmission loss measurements for panels or

test partitions, as described briefly in

Section 2.2.2.1. These facilities Included

two adjacent reverberation rooms, separated

by the test panel assembly. In addition,

facilities existed for the measurement of

impact-noise properties of floor-ceiling

assemblies. For some time, the use of these

facilities was made available for the

measurement of transmission loss, through

provision of a service at an agreed upon

standardized fee. Two changes came about,

to the effect that this service is not

presently provided by NBS.

At the time that NBS had initiated the

measurement service, alternate sources did

not possess the necessary facilities, and

the measurement methods had not become well

accepted within the standards community. As time went on, the procedures to determine

airborne sound transmission became

relatively well established, and certain

independent testing laboratories acquired

the necessary facilities to perform these

tests. At the same time, NBS facilities

became somewhat obsolete. Thus, because of

this factor and because other sources of the

airborne sound transmission measurement

service were readily available, NBS

discontinued the provision of the service.

The second change brought about was the

decision, at the time of construction of the

NBS Gaithersburg facilities, not to include

facilities for the measurement of

transmission loss or for impact noise

measurement. At that time, it was believed

that there were enough commercial

laboratories equipped to provide these

measurement services that the NBS acoustics

program did not require them also. The

initial consequence of this decision was that it was practically impossible to conduct the relevant measurements at NBS. As it has developed, this decision has had

an adverse effect, both upon the growth of

NBS expertise, and upon NBS relationships

with the standards community. Without the

opportunity to conduct measurements of the

acoustic transmission properties of building

structures, the direction of NBS acoustical

research has had to consciously omit the

important subjects of airborne and

structure-borne sound transmission

properties of building structures, and NBS

outputs on this topic to the standards and

measurement community have been weakened.

As a further consequence, neglect of the

interaction of sound and structural vibration has occurred. This is an unfortunate

characteristic consequence of a conscious

decision to omit provision of essential

measurement tools.

In order to remedy this deficiency, it

will be necessary either to construct these

facilities, or to make arrangements for the use of the required facilities at some other

laboratory. In the absence of the required

facilities, satisfactory program growth and

relevance to some of the important

measurement needs of the nation cannot take

place, and NBS cannot develop required

improved measurement procedures, provide

independent test data, or participate

meaningfully in the promotion of uniform

measurement methods among the members of the

measurement infrastructure.

At the time of these decisions, however,

it vas realized that an important property

of acoustic fields which could not, and to this date still cannot be quantitatively

characterized was that of the diffusiveness

of reverberant acoustic fields. An overt

reprogramming effort of available manpower

to this important field took place. Despite

these actions, however, no satisfactory

quantitative metric for the diffusiveness of

reverberant acoustic fields has been

developed. Present efforts continue to be

directed toward this topic, concentrating

upon the application of digital signal

processing and spatial sampling concepts.

Several innovative concepts have evolved

[62].

4.4. Evaluation of NBS Program

It is useful to note several perceived

strengths and deficiencies of the NBS role

in the National Acoustics Measurement

System. One strength is the provision of

calibration services for precision condenser

microphones. The degree of accuracy and

precision which characterizes these

measurements is higher than that found in

nearly all other acoustical measurement

processes, and these measurements are utilized in the calibration of many

additional instrumentation systems.

NBS acoustics staff members have played

an active role in developing measurement

methodologies for use by regulatory

agencies, and in technical documentary

standards. In the course of this work,

close interactions with standardization

organizations and professional societies

have developed ensuring that the National

69
Measurement System/NBS interaction is broad

in scope.

A further identifiable strength of

current NBS acoustics activities consists of

the evolution of sophisticated special

purpose noise monitoring instrumentation

systems, and the provision of test and

evaluation services (as desired) for related

commercially available instrumentation.

These activities have provided valuable

guidance and established the feasibility of

constructing highly accurate, sophisticated,

and reliable noise measurement instruments.

Several important deficiencies in the

NBS role in the system can also be

identified. Perhaps most immediately

notable is the absence of test facilities

required for certain important measurement

processes. Specifically, the absence of a semi-anechoic test environment results in

severely limited attention to measurement

procedures for this condition.

Further limitations on the scope of

present activities and participation in the

National Measurement System infrastructure

are imposed by the absence of transmission

loss and structure-borne noise test

facilities. As NBS knowledge of

reverberation room acoustics increased, it

became apparent that further research on the

subjects of transmission loss and

structure-borne noise were necessary. Yet,

without the necessary facilities it is not

possible to conduct this research.

Additional limitations are imposed by the

absence of state-of-the-art instrumentation,

such as real time digital signal processing.

Because these limitations, if continued

indefinitely, would impose severe restrictions on the involvement of NBS staff

in the National Measurement System infrastructure, appropriate adaptations are presently planned to acquire the essential

test facilities and instrumentation, and to appropriately redirect manpower.

Other identified NBS program weaknesses

will give rise to probable changes to the

National Measurement System/NBS interaction.

These will include an increase in the amount

of analytical or basic research concerning

the mechanisms of noise generation and

transmission, attention to the relationship

between structural vibration and acoustic

radiation, and consideration of important

practical considerations such as specification of sound level meter

calibration procedures, attention to

electronic aspects of audiometric

instruments, and consideration of the

relevant psychoacoustic phenomena.

The needs for NBS services are made

apparent through contacts directly to NBS

from the prospective users, or through

indirect means such as requests transmitted

through the infrastructure, and as well,

through reviews of the requirements of the

measurement system such as that underlying

this report.

Current NBS resources to meet present

user needs appear to be adequate in most

respects. Naturally, there are some needs

of potential users which cannot be met,

because of the absence of desired

facilities, but the present facilities and

staff are well adapted to most present user

needs, and as previously noted, NBS is able

to provide many important measurement

services. Because of the current and

anticipated growth of the noise emission and

monitoring as well as the hearing

conservation technologies, considerable

attention is presently directed toward study

and review of the physical basis for and

quantitative estimation of inaccuracies in

the relevant measurement methodologies.

Current NBS capabilities in the evaluation

of complex acoustical instrumentation

systems appear to be well adapted to these

studi es

.

Ultrasonic nondestructive testing

appears to be an example of an emerging

technology for which NBS can provide

significant leadership in standardization

and acoustical measurements. In this case,

several industrial representatives and the

Air Force Material Laboratory requested NBS

to consider the possibility of assuming a more active role in the standardization

processes associated with this technology.

Also, NBS has been asked by the American

Society of Metallurgical Engineers, the

American Society for Testing and Materials,

the Electrical Power Research Institute,

transducer manufacturers, and researchers to develop and disseminate absolute measurement

techniques for acoustic emission

transducers. It is appropriate that NBS be

involved with these topics since the work is closely concerned with the development of

test methods, physical properties of

materials and products, physical standards,

consistency in measurement, and assistance

to other government agencies — all criteria

which are embodied in the NBS enabling

legislation and its subsequent amendments.

In the event that NBS is not able to provide

70
assistance, there are three areas of

national concern that will suffer: — Competitiveness and productivity of

American manufactured products for

quality control, unit cost, product

improvement, reliability and

maintainability. Exported

manufactured products from the

U.S.A. have often met price

competition through better

performance and reliability. These

advantages are being eroded by

technological advances of foreign

producers. The absence of carefully

evaluated non-destructive testing

and evaluation standards and

techniques from a nationally

recognized source that can be used

effectively and economically is denying American industry a potentially powerful tool -- that of

reducing hazards to the consumer —

which would help retain and expand

export markets

.

— Hazards in consumer products can be

reduced significantly by appropriate

use of non-destructive testing and

evaluation technology. The high

costs of the equipment and skilled

operators has precluded its use for

inspections of the critical

components of most consumer

products. Traditionally,

standardization of devices and

procedures has reduced the costs of

using sophisticated measurement

systems and this is expected to occur here also. — Continued reliability of public and

quasi-public facilities such as energy transmission systems,

transportation equipment, power

plants and large structures is

clearly in the public interest.

Varying levels of monitoring are regularly carried out for these

kinds of facilities to anticipate

degradation or loss of mechanical

integrity with non-destructive

testing and evaluation procedures

being widely applied. These efforts

are seriously handicapped by the

lack of an unequivocal physical

reference system, i.e., standards,

against which observations can be

compared.

The current NBS program in acoustics, as has been indicated, includes a wide range of

services, from the provision of microphone

calibration services to representation of

U.S. interests in the international

standards infrastructure. In the event that

some of these services were to be

discontinued there would be a potentially

wide range of impacts.

Some of the more routine calibration

work might conceivably be obtained at alternate sources, but at some potential

sacrifice of the objectivity and tight

control of the measurement variables which

has characterized NBS services in these

fields.

Other services, such as the

representation of U. S. interests in the

international standards community are important in continuing efforts to assure equity in international trade. In particular, in the event that the

international noise control corrmunity were

to adopt noise measurement methodologies

radically at variance with those in the

U.S., artificial barriers to international

trade might ensue. in that product noise

emission specifications would not be

compatible, with a resulting adverse effect

upon purchase of U. S. goods abroad. An important objective of NBS participation in the international standards infrastructure

is to ensure not only that the interests of

the participants in the infrastructure in

this country are appreciated

internationally, but that international

thoughts on these topics are understood in

this country.

Because of the disparate interests of

the various segments of the industries

concerned with acoustical measurements and

noise control, the voluntary consensus system for the development of noise

measurement methods has not independently

developed many of the required methods and

cannot react in an acceptable time frame.

Furthermore, NBS participation in the

acoustical standards setting infrastructure

is necessary since many of the required data

bases and test methods could alternatively

only be developed by private sector

laboratories and consultant firms. In many

cases, these organizations are heavily

involved in noise abatement work with the

industries to be regulated, and conflicts of

interest would impair their potential

objecti vi ty

.

4.5. The Future

Several changes in the services

presently provided by NBS appear to be

71
indicated at this time. These changes are dictated largely by realization of the

changes taking place within the acoustical

measurement portions of the National

Measurement System, and are mainly a consequence of the introduction of what was previously termed the legislative

imperative. This imperative simply consists

of the realization, on the part of those

performing acoustical measurements, that

acoustical measurements will be required for

the implementation of noise control or environmental pollution legislation. Thus,

there will be important legislative and

economic consequences associated with not

only the "end-use measurement data", but

with the associated measurement

methodologies. Whereas in previous eras the

significance of measurement data and of the

associated accuracy and precision was often

largely an academic concern, the legislative

imperative has provided a long overdue

motivation for the evolution of improvements

in instrumentation, in measurement

methodologies, and in the extensions of

acoustical measurement services.

Specifically, it appears that three

types of improvements in NBS acoustical

measurement services are indicated: — A program of sound level meter "type

certification" should be developed

in realization of the increased

significance of errors resulting

from use of improperly calibrated or functioning sound level meters.

Such a program ought to achieve

several objectives. At the very

least, a calibration service should

be provided to verify that an instrument does or does not conform

to the appropriate sound level meter

specifications. A second objective

would be to establish a standard

method for acoustical and electronic

calibration testing of sound level

meters. Finally, another objective

would be the improvement of the

relevant specification standards.

The evolution of such a program is

in response to requests and

inquiries from regulatory and

eni'orcement agencies, manufacturers,

and industrial laboratories, and

should greatly help in reducing

measurement uncertainty resulting

from the instrumentation system.

— The present NBS program directed

toward the study of noise emission

measurement, and noise monitoring

instrumentation and measurement

methodologies must be extended in scope, In particular, the economic

and social consequences of

measurement imprecision and

inaccuracies must be made more apparent to the relevant regulatory

agencies, to the standards- setting

community, and to the relevant trade

associations. Also, attention

should be directed to the relevant

physical phenomena in order to evolve measurement systems with

improved accuracy and precision. — It would be appropriate for NBS to participate more fully in the

calibration of audiometric equipment

than is presently done. Study of

the adequacy of acoustical and

electroacoustical performance and

calibration specifications for these

instruments, and participation in

measurement assurance programs and

calibration round- robins are indicated by considerations of the

greatly increased frequency of

audiometric testing anticipated as a consequence of hearing conservation

programs demanded by current and

proposed regulations.

The emerging technology of ultrasonic

non-destructive testing and evaluation is an excellent example of an acoustical

"measurement-intensive" technology which

will require appreciable support from NBS in

the future. In particular, it will be

important that NBS aid in more precise

characterization of reference materials used

in this technology, in the provision of

calibration services for the ultrasonic

transducers used, and in the extension of

fundamental physical principles to analysis

of the ultrasonic non-destructive testing

and evaluation instrumentation.

There are numerous legislative actions

that force the provision of these and other

related services. These range from the NBS

Enabling Act of 1901, to the Noise Control

Act of 1972, which authorizes the

Administrator of the Environmental

Protection Agency to develop improved

methods and standards for measuring and

monitoring noise in cooperation with NBS,

and to proposed legislative or regulatory

actions of the future. At present, it

appears likely that many more states and

72
municipalities will become active in noise

control legislation within the next decade,

and it will be important that NBS provide

appropriate leadership on the topic of the

acoustical measurements required for

effective legislative actions and

enforcement.

Several actions on the part of NBS to respond, not only to the realization of the

needs of changing and emerging technologies,

but to the realization of the strengths and

weaknesses of the current NBS -program in

acoustics, are in order. These actions

include: — Initiation of the above-indicated

improvements in NBS services and

provision of NBS support to emerging

technology. — Intensive scrutiny of existing

acoustical measurement methodologies

with regard to quantitative

estimation of the inherent

measurement errors and imprecisions

,

supplemented by studies of the

consequences of these errors to the

society. — Strengthening the current program of

basic acoustical research to extend

the scope of current activities to include the topics of airborne and

structure-borne sound transmission.

In order to stimulate this work, it

will be necessary to provide

essential transmission loss

facilities. Laboratory measurements

of sound emissions over a reflecting

plane in an otherwise anechoic space

are not permitted by the present

facilities. This important

deficiency and limitation on measurement capabilities should be

remedied. — Finally, the acoustical measurement

community, both at NBS and within

the larger infrastructure, should be

educated as to the structure of the

National Measurement System, to the

inter-relationships existing within

the system, and to the means by

which the inadequacies of the system

can be remedied.

5. SU^f1ARY AND CONCLUSIONS

5.1. State of The National Measurement

Sys tem

The concept of a National Measurement

System does not appear to be very widespread

or initially comprehensible to many of the

actual participants in the system. This is

certainly true for those concerned with the

acoustical measurements portion of the

system. Although it is likely that those

involved suspect that there ought to he some systematic interrelationship of the bases

for all measurement processes, most of those

performing acoustical measurements realize

that their measurement processes are at best, loosely coordinated. Because all

active scientists and engineers are at some

time or another concerned with measurement,

and require the objective quantitative

knowledge that is to be obtained from

measurements, they are participants in the

National Measurement System. An important

objective of the study on which this report

is based has been to identify the structure

of the National Measurement System for

Acoustical Measurements. In so doing, the

relevant measurement system elements and the

interfaces between these elements and NBS

make the system infrastructure more

apparent, and technological, social, and

economic impacts have been discussed. In the process of defining ttie system

structure, current measurement challenges

have been identified and .clarified. These

data are important factors in the allocation

of funds, in the evaluation of current

programs in the light of new information and

in the prediction of program directions

adapted to new needs.

The scope of this report has been

principally limited to those acoustical

measurement processes which are motivated by

increasing societal concern over noise and

which are, at the same time, continuations

or extensions of traditional acoustical

measurements. As an illustrative example of

the diversity of acoustics, however,

additional material has been presented to describe the technology of ultrasonic

non-destructive testing. This technology is

directed toward identification of structural

flaws, and the measurements are performed in

order to meet increasingly severe damands

for mechanical integrity, reliability, and

pressures for material conservation.

The role of acoustical measurements in our technological society has significantly

73
increased within the recent past not only

because of the continuing expansion of

technology, but also because of the

emergence of a legislative imperative. This

imperative grew out of legislative and

regulatory actions directed at a reduction

of the form of environmental pollution which

one author has termed the "tyranny of

noise". [63]

Acoustical measurements directly

affected by the legislative imperative

include the measurement of noise emissions,

environmental noise monitoring and those

related to the implementation of hearing

conservation programs.

Until recently, there was only a limited

awareness among the acoustics technical

community of the desirability or necessity

for inter-consistency of acoustical

measurement methodologies, or for close

attention to the accuracy and precision

inherent to the measurement process.

However, the legislative imperative has now intensified awareness of the shortcomings of

the measurement system and the potential

economic impacts of measurement errors are now being realized.

The nature of the acoustical measurement

portion of the National Measurement System

is undergoing an evolutionary transition,

from a previous state in which the

consequences of measurement error were often

disregarded, to an improved state in which

the consequences of measurement error are often recognized to be intolerable.

Increased attention is consequently being

brought to bear upon the improvement of

measurement systems -- both as systems of

instrumentation elements and measurement

methodologies and as systems containing

individual participants making use of

measurement instrumentation and

methodologies.

It is therefore an excellent time for

participants in the acoustical measurements

portion of the National Measurement System

to benefit from studies of the relevant

interrelationships, to improve the

measurement transactions occurring between

system elements, and to direct their

individual or institutional roles toward the

evolution of an improved measurement system.

5.2. Role of NBS Acoustics Activities

Within the National Measurement System

The role of the National Bureau of

Standards acoustics activities within the

infrastructure of the National Measurement

System is based primarily upon interactive

processes, which constitute the inputs and

outputs for these activities. The substance

of the interactive process consists of such

elements as the provision of and interchange

of data pertaining to: — transducer calibration services — literature reviews — data bases — development of measurement

methodo Togies — development of special purpose

instrumentation systems — evaluation of instrumentation

systems — study of the physical phenomena

relevant to all acoustical

measurements.

Participants in this interactive process

include standards organizations, various

industrial representatives (including trade

associations and individual manufacturers),

professional societies and universities, and

representatives of foreign laboratories.

Because of the increased legislative

attention being given to noise and its

control , and of the consequent attention to the required measurement methodologies, the

adequacy of these methodologies is now the

subject of intensive study, both within NBS

and within other Federal, State and local

agencies

.

5.3. Conclusions and Recomnendations For

Action

The study indicates that there is a continuing demand for improved accuracy and

precision both in the development and

calibration of acoustical measurement

instrumentation and in the evolution of

improved measurement methodologies.

Provision of services such as these has

traditionally been a strength of the NBS

program in acoustics.

The study also illustrates that a significant increase in the number and scope

of legislative actions directed toward noise

control has taken place. It is likely that

this increase will continue, particularly as State and local governments become active

participants. Inconsistencies in the

relevant required measurements are apt to introduce ambiguities into the legislative

actions and the imprecisions inherent in

these measurements may introduce inequities

in trade as well as inhibit expansion of the

technology.

74
A number of elements are suggested for

incorporation into the existing NBS program

in order to adapt to changing needs of the

technical community. These elements

include: — Thorough study of the effects of

environmental factors such as temperature and humidity upon the

properties of acoustical measurement

systems and system elements. These

factors become increasingly

important as interest is extended to include acoustical measurements

conducted over long time periods. — Provision of performance testing

services for acoustical measurement

systems such as sound level meters.

This would include the development

of an appropriate test methodology

both to verify proper operation and

to supplement the present standards

on performance specifications. — Renewed attention to the electronic

and acoustical characteristics of

audiometers. The proper

calibration, maintenance and

operation of this type of acoustical

measurement instrumentation will

become increasingly important to our society as hearing conservation programs become mandatory and more widespread. — Continued attention to the accurate

and objective collection of noise

emission data bases and to the

development of improved acoustical

measurement methods. The provision

of these services to such users as Federal, State and local regulatory

agencies and trade associations will

be critical to the equitable

enforcement of noise control

legi slation

.

— Continued interaction with the

national and international

acoustical measurement standards

community. These interactive

processes provide an important means

for the dissemination of NBS

measurement expertise.

absence, at the NBS Gaithersburg

site of semi-anechoic, airborne

sound transmission loss, and

structure-borne sound test

facilities has proven to be a severe

handicap, not only to NBS

involvement in the infrastructure

but also to continued professional

growth of the staff. Provision of

the facilities will remove barriers

which presently stand in the way of

the provision of leadership by the

National Bureau of Standards in the

measuremiant of important acoustical

phenomena.

Based upon the above recommendations, it

is the authors' judgement' -that acoustical

research should be directed toward: — basic physical phenomena which

underlie all acoustical measurements — the study and evolution of both

improved measurement facilities and

instruments which constitute the

tools used for' measurement — the improvement of the required

measurement methods which constitute

the rules, definitions and

procedures by means of which the

tools are used for the measurement

process.

The authors wish to acknowledge the

following persons who contributed to this

report. Portions of this report were adapted from material provided by R. D. Berendt, D. G. Eitzen, D. R. Flynn, W. Koidan, W. A. Leasure, J. A. Molino, and

P. G. Weissler whose expertise in the

performance of acoustical measurements

constitutes an important strength of the NBS

program. Assistance in preparation of the

text was also provided by J. R. Russell and

R. D. Kilmer. Finally, the cooperation and

support of W. A. Leasure, the valuable

guidance of L. K. Irwin, and the

encouragement provided by D. T. Goldman are recognized. — Strengthening of the NBS program of

research in the relevant basic

physical phenomena, and the

provision of important measurement

facilities for this research. The

75
APPENDIX A. METHODOLOGY OF THE STUDY

In the conduct of this study of the

acoustical infrastructure of the National

Measurement System, use was made of a number

of complementary sources of data. While the

individuals contributing to the preparation

of this report each utilized somewhat

different methods, there have been some common elements to the various approaches.

Basically, the common elements have

included:

... Membership in sixxndards oormittees

and professional societies . NBS

personnel serve on technical

committees of the American National

Standards Institute, American

Society for Testing and Materials,

Institute for Electrical and

Electronic Engineers, and the

International Organization for

Standardization. Professional

society memberships are held in the

Acoustical Society of America, the

Institute of Noise Control

Engineers, the Institute of

Electrical and Electronic Engineers,

and the Audio Engineering Society.

In addition, close contact is maintained with the Society of

Automotive Engineers.

. . . Attendance at professional soaiety

meetings or special conferences and

symposia. Notably, NBS

representatives participated in the

previously cited Conference on Acoustics and Societal Problems,

sponsored by the Acoustical Society

of America.

. . . Meetings with tradti organization and

industry representatives, such as those listed in table 12.

research activities and

international measurement systems.

Also, valuable inputs for this study

were provided by visits to the

facilities of, and meetings with

faculty and staff members of several

universities

.

Review of relevant technical

literature, proceedings of technical

conferences, and a limited amount of

economic market analysis reports

dealing with the economics of the

noise abatement market.

Preparation and review of several

informal (limited distribution)

questionnaires and correspondence

sent to industry and federal

government representatives.

Compilation of information to be

used in the preparation of technical

reports by NBS personnel provided

useful inputs to this report.

Daily use, by NBS staff members, of

the instruments and instrumentation

systems discussed in this report

provided a familiarity with the

operating characteristics of the

devices, the context in which they are used in a particular measurement

methodology, and the inherent

strengths and weaknesses which

choice of a certain device imposes

on the methodology.

Discussions with personnel in

Federal and state agencies, most

notably Department of

Transportation, Environmental

Protection Agency, General Services

Administration, Veteran's

Administration, Department of

Housing and Urban Development, and

the State of California. In many

cases, NBS has worked closely with

these agencies in a variety of

measurement-related tasks.

. . . Visits to domestic and foreign

research laboratories. These helped

to determine the current status of

76
APPENDIX B. SUMMARY OF BACKGROUND DOCUMENTS

Document Title:

By:

Publisher or Source:

Relevance to This Study:

Document Title:

By:

Publisher or Source:

Relevance to This Study;

Document Title:

By:

Publisher or Source:

Relevance to This Study:

"Acoustic Measurements"

L. L. Beranek

John Wiley and Sons, Inc. New York, (1949)

This text is the basic reference text on the subject of acoustical measurements, and

despite the fact that it is more than 25

years old, it still adequately describes many

of the fundamental physical considerations

involved in performing acoustical, measurements.

Detailed information supplementing that contained

in this report can be found in this text.

"Measures For Noise Abatement"

An Issue Study

D. R. Flynn and A. I. Rubin

NBS Internal Document (1972) , This issue study documents the noise problems

in the United States, indicates that improved

acoustical measurements are essential for workable solutions to the problem, and indicates

reasons why NBS is a wel 1 -qual if ied agency to deal with noise measurement problems. It describes an enlarged NBS program in noise to deal with the problem, outlines the emphasis of

this program, and indicates the desirability

of construction of new facilities. This is an example of an NBS program review conducted

prior to this study.

Noise Pollution Abatement Report

(Unspecified)

Frost and Sullivan, Inc. New York, (1972)

This report documents a private analysis of

some of the technological and economic factors

involved in noise control problems. It consists

of a synthesis of material obtained from a variety of sources, and was useful primarily as as source of economic data.

Document Title:

By:

Publisher or Source:

Relevance to This Study:

Document Title:

By:

Publisher or Source:

Relevance to This Study:

Noise Pollution Control: Report No. 418

(Unspecified)

Stanford Research Institute

Menlo Park,, Calif. (1972). . This report documents another private analysis

of factors involved in noise pollution control.

Its relevance was primarily to provide an over- view of the noise control problems.

Occupational Exposure to Noise

(Unspecified)

National Institute for Occupational Safety

and Health

U. S. Department of Health, Education and

Welfare (1972)

This report documents technical and physiological

factors supporting the criteria for recommended

standards on occupational exposure to noise to be

acted upon by the Occupational Safety and Health

Administration of the Department of Labor.

77

I
Document Title:

By:

Publisher or Source:

Relevance to This Study:

Report on the Conference on Acoustics and

Societal Problems

J. C. Johnson and A. D. Stuart (eds.)

Acoustical Society of America

New York (1972)

This conference report describes the results of

a conference dealing with the topics of: noise

and man, outdoor sound propagation and sources,

motor vehicle noise, bio-medical acoustics,

acoustic applications, and other topics. The

conference, made possible through the support

of the National Science Foundation, attempted

to deilineate ways in which the Acoustical Society

of America might address problems affecting

human welfare. It is useful in its concern for

social and technological applications of acoustics,

78
Government

Standards Activities

This is an edited summary of an oral presentation on government standards and regulations by D R. Flynn of the National Bureau of Standards. This presentation was made

on 15 January 1974 at the Arden House Workshop on Noise

Control Engineering, Arden House, -Harriman, N.Y. — Ed.

This talk discusses some of the noise regulations that presently exist, most of which are fairly recent. Mainly be- cause of my own experience vTith the Federal Government,

this discussion wril be a little more heavily slanted toward

the Federal regulations. Also, the implications of measure- ment and measurement standards with regard to the regulations will be discussed briefly. The regulations that have probably had the most impact

so far (mamly because they have been in force slightly longer than some of the others) are the hearing conservation

regulations (see Table 1). As originally passed, the Walsh- Healey Public Contracts Act authorized Federal regulation of a number of safety and health requirements having to do

with work done under Federal contract, but it was not until 1969 that the Walsh-Healey noise regulation was promulgated. Under the Federal Coal Mine Health and Safety Act

of 1969. essentially the same regulations as those under the Walsh-Healey Act, were extended in 1971 to cover the noise exposure of mine workers. The Construction Safety Act ex- tended this coverage to some groups of construction workers.

In 1970, after the Occupational Safety and Health Act wjs

passed, these regulations were extended to essentially all workers engaged in interstate commerce.

REGULATIONS

AUTHORITY PROMULGATED

Walsh-Healey Public Contracts

of 1942 1969

Federal Coal Mine Health and

Safety 1971 Construction Safety Act 1971

Occupational Safety and Health Act of 1970 1971

Interstate Commerce Act and

Department of Transportation Act 1973

Miscellaneous regulations specific to a given agency's activities have been issued by the: Atomic Energy Commission

Air Force Navy

Genera! Services Administration Army

Table 1. Federal Hearing Conservation Regulations

Under several authorities, specifically the Interstate Commerce Act and the Department of Transportation Act, there have been some recent regulations from the Department of

Transportation, Bureau of Motor Carrier Safety, that are also quite similar to the aforementioned ones. All of these regulations utilize the A-weighted Sound level and with few ex- ceptions, all the regulations utilize the 5 dB per doubling

rule - that is, for every 5 dB .-ncrease in level, the allowable exposure time is halved. Inter.Tational standards under ISO

use an equal energy rule, correspondin.H to 3 dB per doubling.

In the EPA criteria document and in early drafts of their "levels document" (to be discussed lat'jr'! a 3 dB per doubling rule is used. With a 3 dB per doubling rule, if 90 dB A

were allowed for eight hours, the maximum noise level that would be allowed for 15 minutes would be 105 dB A rather than 115 dB A as allowed under the present OSHA regulation. The particular algorithm selected has significant i.mpli- cations for the technical and economic impact of the regulations. Regulations similar to these have been enacted by

other Federal agencies to suit their particular activities. These hearing conservation regulations have several ramifications in the measurement sense. They h'ave resulted in a proliferation of sound level meters, particularly what is re- ferred to a^. a Type 2 sound level meter, over the past four

or five years, and some of these sound level meters are, candidly, less than satisfactory. They have also resulted in the development of a nuihber uf integrating sound level meters or dosimeters, if you will, that attempt to measure a worker's total noise exposure. There are currently performance standards being developed by ANSI on this instrument.

In addition, several Federal agencies (Bureau of Mines, De- partment of Interior; National Institute of Occupational

Safety and Health, HEW) have been evaluating these instru- ments. NBS has evaluated several commercial dosimeters

for the EPA and has issued a report giving the lest results. There are some real measurement problems with these devices. Hopefully, these problems will be addressed and the

situation will improve somewhat in the future. In additiun

to hearing conservation regulations, there have been a number of other congressional actions over the past few years

that have had significant impact (see Table 2). These tend

to relate more to authorities for transportation noise. However, the National Environmental Policy Act requires that environmental impact statements be filed in a number of

different activities. There have been a number of those on

noise - to put in a new highway, a new airport, or any

other major construction project, the impact on the en- vironment has to be assessed. To continue further, under

Title IV of the Clean Air Amendment of 1970, EPA was

authorized to do a study of the noise problem and this re- sulted two years ago in their report to the President and

Congress on noise. The Consumer Product Safety Act of 1972 has implications for some fairly stif f regulations. This

Act. in effect, states that for any consumer products where

there is a real safety problem the Consumer Product Safety

Commission can prohibit the sale of those products. One

has to define what one means by safety. This could be a hearing hazard, or in principal, it is possible to have a product sufficiently noisy that there is a danger due to communication interference (for example, if a person cannot

hear a warning signal). NBS lias been involve4 in testing some noise-producing toys, particularly cap guns, and in the future will probably test other noise-producing consumer

products.

79
• I lanspurtatiuii Act kI l^t)6

• Aircraft Noise Control Act of 1968

• National Environmental Policy Act of 1969

• Airport and Airways Development Act of 1970

• Urban Mass Transportation Act of 1970

• Clean Air Amendments of 1970

• Federal-Aid Highway Act of 1970

• Noise Control Act of 1972

• Consumer Product Safety Act of 1972

• Federal-Aid Highway Act of 1973

Table 2. Congressional Actions on Noise. Switching very briefly to the area ot aircraft noise, there

liave been a number of rule-making actions by the Federal '

Aviation Administration (Table 3). The most notable is the FAR- )6 rule which says that new types of aircraft, basically

I l-J-69 FAR Part 36:

S-4-70 ANPRM 70-33:

10-30-70 ANPRM 70-44:

9- 13-71 NPRM 71-26:

7-7 72 NPRM 72-19:

1-24-73 ANPRM 73-3:

3-13-73 FAR PART 91:

10- 10-73 NPRM 73-26: 10-26-73 FAR PART 36

"Noise Standards: Aircraft Type

Certification" effective 12-1-69.

"Civil Supersonic Aircraft Noise Type Certification Standards"

"Civil Airplane Noise Reduction

Retrofit Retjuirements" "Noise Type Certification and

Acoustic Change Approvals"

"Newly Produced Airplanes of Older Type Design"

"Civil Airplane Fleet Noise (FNL)

Requirements"

"Civil Aircraft Sonic Boom",

effective 4-27-73

"Propeller Driven Small Airplanes" "Noise Standards for Newly

Produced Airplanes of Older Type Designs", effective 12-1-73.

Table 3. FAA Rule mai<ing Actions on Noise.

let aircraft and subsonic aircraft, must be type certified as

to allowable noise under prescribed procedures - the takeott, landing, and sideline noise, flic type certilication util- izes a tone corrected, duration corrected. Perceived Noi\c

Level. This has important measurement implications in. that

it requires fairly accurate third octave band levels and employs a fairly complicated algorithm. As can be seen, there have been several Advance Notices of Proposed Rule-Making and Notices of Proposed Rule-Making in the past few years. The one that is particularly worthy of note (because of the measurement implications) is NPRM 73-26, Propeller Driven

Small Airplanes. This is different from previous rule-making

actions in that it uses, as a measure, A-v/eighted sound level rather than a tone-corrected Perceived Noise Level. It was

felt that for a propeller plane the corr-;lation between human

response and the A-weighted level was adequate enougli to

justify its use in the regulation. Also, in connection with ANPRM 73-3 (Civil Airplane Fleet Noise Reqmrements). the Advance Notice of Proposed Rule-Making is now advancing

to a Notice of Proposed Rule-Makmg. This regulation as "

originally written used a very complicated procedure, sort of

an energy weighting of ihe impact from the whole tleet rather than that of a single airplane. There was so much

controversy over this that it has been simplified considerably

in the Notice of Proposed Kule:.Making. Under the Noise Control Act of 1972 (Table 4). the Administrator of EPA is authonzed, to coordinate Federal pro- grams in noise, to identity major noise sources, to establish noise criteria, and to publish reports about available control

Sec. Sec.

Sec. 6

Sec. 7

Sec. 8

Sec. 9 Sec. 14

Sec. IS

Sec. 17

Sec. 18

Federal Programs

Identification of Major Noise Sources, Noise

Criteria, and Control Technology

Noise Emission Standards for Products Uibtributed

in Commerce

Aircraft Noise Standards -Study

-Standards and Regs

-FAA Act Amended

Labeling

Imports

Research, Technical Assistance, and Public Information Development of Low-Noise Emission Products

Railroad Noise Emission Standards Motor Carrier Noise Emission Standards

Table 4. Noise Control Act of 1972

technology. In July, tPA published their "criteria docu- ment," and currently are working on a levels document. (The

"levels document" was issued in early April - Kd.J In the

"levels document" they are putting forth levels, independent

of technological and economic considerations, that would

assure protection of public health and welfare.

.Section VI of the Act. which may have very significant implications for the whole country, allows EPA to set noise emission standards for new products distributed in commerce.

Essentially this says that if a product makes more than a certain noise level as delcritiined by a certain iiieasurenient methodology, it cannot be sold. EPA .should announce

shortly the first lew products /'5t'e ilic Federal Register for 21 .lune l'J74 t'd.) to be regulated under this section of

the Act. NBS is working with EPA closely on the develop- ment of appropriate measurement methodology, and cer- tainly this has to include not merely how the acoustic measurements arc made but what the device under test is doing, what sort of operation it is undergoing while you're making the measurement, how it is installed, etc. Under Section VII, EPA has authority in the area ot air- craii noise standards. In particular, the Federal Aviation Act has been amended to permit EPA to study the problem

and then recommend standards and regulations to the FAA.

Without going into detail, some of the areas under considerlion include takeoff and approach procedures, minimum

80
altitude procedures, type certification of aircraft, fleet noise

levels, rjirotltting of existing aircraft, the supersonic problem, and possible modifications to the present regulations (FAR

36). Also, EPA will be considering questions concerning

propeller plans (in addition to jet planes), the R/STOL gnd

VTOL aircraft, and the whole question of airport noise reg- ulations (see Table 5 for a summary of these).

1 . Takeoff Procedures

2. Approach Procedures

3. Minimum Altitude Procedures

Operating

Procedures

4. Retrofit/Fleet Noise Level (FNL)

5. Supersonic Civil Aircraft Noise

6. FAR 36 Modifications

7. Propeller Driven Aircraft

8. Reduced or Short Takeoff or Landing (R/STOL)

9. Vertical Takeoff or Landing

(VTOL)

10. Aircraft Noise Regulations

Type

Certification

Table 5. Aircraft/Airport Noise Regulatory Actions

Under Section Vlll of the Noise Control Act, the Administrator is authorized to require labeling of products where

the noise impact is not sufficiently severe to prohibit sale of the product, but severe enough that an indication of the

noise emission from that product is needed. The measure- ment implications here are quite severe; how is a product

labeled so that it provides sufficient information to the ultimate consumer and is still simple enough that the majority of persons will understand it? How can the noise of

different types of products be compared'.' Do you use actual

decibel levels or do you give simpler A, B, C, D type categories, etc? It gels to be very difficult to know just how to do this, particularly with other Federal agencies coming out with labeling systems for other product attributes besides

noise. If not well-planned and thought out, the communication that is desired will be totally lost. In Section XIV, EPA is authorized to carry out rather complete activities in the area of research, technical information, technical assistance to states, local governments, etc., and public information. The effectiveness of Section XV depends o:i how strict EPA is willing to be about it. This Sectio,i authorizes the General Services Administration, in Federal procurement actions, to pay a premium price of up to 257o for certified low-noise emission products. This could have some leverage on the development of low noise emission products.

Sections- XVII and XVIII wererput in by Congress rather

late in the progress of the bill. They regulate interstate

carriers and require EPA to set noise emission standards for both railways and interstate motor carriers. Both of these have preemption provisions and there is a lot of concern as

to how these may or may not go along with state regulations

that have been passed in recent years.

All of these activities have fairly severe and complicated measurement requirements and NBS is trying to work closely with EPA to address a number of these points. It is quite a

large task, and EPA is under a great deal of pressure to get

a lot of work done in a very short period of time.

In addition to specific regulations, there are other Federal

activities that are not really of a regulatory nature, but have

serious implications as far. as their impact on the econom.y

(see Table 6). These have to do with Federal procurement

activities. For instance, for jackhammers, impact wrenches HUD Policy

FHWA Standards

GSA Procurement

EPA Low Noise Emission Products

Table 6. Federal Procurement Activities Relating to Noise.

and other such equipment, GSA is buying them now to perform to standards which, among other things, have noise emission requirements. There is also a joint NBS-GSA pro- gram where NBS is investigating performance specifications

for power lawn mowers and room air conditioners with the thought to buying them with a price premi.um'given lor low

noise emission products.

In Table 7, it can be seen that HUD has had, under their Federal Housing Administration, some regulations and re- quirements related to obtaining Federal housing grants. For

instance, to obtain an FHA guaranteed loan or mortgage, iioD

Federal Housing Administration —Proximity to Airports

—Minimum Property Standards Departmental Policy

GSA

Public Building Service DOD

Tri-Service

Table 7. Federal Requirements on Acoustical

Characteristics gf Buildings.

there are requirements concerning housing in the proximity

of airports, as well as minimum property standards relating

to, for instajice, the noise isolation required between

dwellings in multiple family situations. Their departmental

policy will be discussed below. General Services Administration has issued performance

standards under their Public Building Service requiring that any building built for the Federal government must meet

certain criteria. The acoustical criteria could be NC require- ments in buildings, noise isolation between rooms within

buildings, etc. Similarly, the Tri-Service Group within the Department of Defense has regulations on buildings that would be procured with DOD funds.

81
The Department of Housing and Urban Development, in Departmental Circular 1390.2, gives standards for the external noise exposure at new construction sites. Essentially, these say that you cannot get Federal funds or Federal guarantees (either through a grant program or guaranteed

loan program) unless the noise exposure at a new construction site meets certain criteria. Table 8 lists these criteria.

"UNACCEPTABLE"

Exceeds 80 dB A for 60 Mins./24 Hrs. Exceeds 75 dB A for 8 Hrs. / 24 Hrs. Exceeds CNR 115. Exceeds NEF 40.

"NORMALLY UNACCEPTABLE"

Exceeds 65 dB A for 8 Hrs. / 24 Hrs. "Loud Repetitive Sounds". Between CNR 100-115. Between NEF 30-40.

"NORMALLY ACCEPTABLE"

Does not exceed 65 dB A for 8 Hrs. / 24 Hrs.

"ACCEPTABLE"

Does not exceed 45 dB A for 30 Min. / 24 Hrs. HUD 1390.2

Table 8. External Noise Exposure

Standards for New Construction Sites.

Tiie circular states that tiie site is unacceptable it' the noise

level exceeds 80 dB A for 60 minutes out of 24 hours,

or 75 dB A for eight hours, and, if it is near aircraft, if

it exceeds a CNR of 1 15 or an NEF of 40. If a site is unacceptable, it requires a waiver signed by the Secretary

of Housing and Urban Development if it is to be considered. A key division between "normally unacceptable" and "normally acceptable" is whether or not the noise

level at a site exceeds 65 dB A for eight hours out of 24. To determine compliance with this requirement, has certain measurement impHcations. For instance, an individual from New York who did the required measurements

stated that he used a tape-recorder and sound level meter, and taped the noise for 24 hours, usually usmg fairly high

recording speeds and small reels of tape, thus requiring

frequent tape changes. He said he took out a professional, a technician, and also, for any place in New York, an' armed guard. As a consequence, to get 24 hours of data,

it took about nine man days of labor, and probably an- other three man days to analyze the analog tapes. So,

as can be seen, it is a difficult and expensive problem. As

a result, NBS has been heavily involved with HUD in de- veloping black box instrumentation that can be strapped on a telephone pole and, at the end of 24 hours, be re- trieved with all the necessary data there.

In addition, HUD has interior noise exposure standards

(Table 9). These relate both to new construction and to

"ACCEPTABLE"

Sleeping Quarters: Does not exceed 55 dB A for 60 Min. / 24 Hrs. Does not exceed 45 dB A for 30 Min. during

1 1 PM - 7 AM

Does not exceed 45 dB A for 8 Hrs. / 24 Hrs.

Other Interior Areas: At discretion of HUD personnel.

HUD 1390.2

Table 9. Interior Noise Exposure Standards

for New and Rehabilitated Residential Construction.

rehabilitation of existing housing. The key requirement

here is that calling for less than 45 dB A for all but 30 minutes during the night or not exceeding 55 dB .A for more

than 60 minutes out of 24 hours. In some areas this would

be very difficult to comply with. Some of the instrumentation NBS has been developing for HUD also can make

these measurements just by the flip of a switch. The Federal Highway Administration has similar require- ments relating to Federal assistance (see Table 10). These

requirements relate to land use, ranging from areas where

"serenity and quiet are important," to residential areas, down through developed lands, undeveloped lands (where

they do not have any criteria), to building interiors. The

unit of measure is A-weighted L \q , the noise level ex- LAND USt NOISE LEV tL

Serenity and Quiet are Important 60 dB A

Residences, Schools, Hospitals, etc. 70 dU A

Developed Lands, Other than above 75 dB A

Undeveloped Lands

Building Interiors 55 dB A

*1 en-Percentile Level, A-weighted.

FHWA PPM 90-2

Table 10. Highway Design Noise I evels.

ceeded 10% of the time. Lssentially, Federal tunds cannot

be obtained if the levels for the different land uses are ex- ceeded, and since inost of the major highways are 9U%

Federally funded, this has severe economic implications. Since there is no such thing as an Ljq meter, the measure- ment problems are a bit tricky using existing conventional

instrumentation. Also, there are measurement problems due to the weather since many of the instruments cannot

be left outside for 24 hours without damage from the elements. With regard to the State regulations, these change so

rapidly that it can only be hoped that they are current within the last year or so. Many of the states have established limits on :he noise emitted from a vehicle during

typical operations. For example, the State of California has regulations governing (1) motor vehicles over 6,000

lbs., (2) motor cycles, and (3) other motor vehicles, specifically lighter vehicles (see Table 1 1). Concerning the sale

82
OPERATED VEHICLES:

Speed Limit < 35 MPH > 35 MPH

Any motor vehicle with

gro$.s weight rating of 6,000 pounds or more -

Before 1-1-73 88 dB A 90 dB A*

After 1-1-73 86 dB A 90 dB A

Any motorcycle 82 dB A 86 dB A

Any other motor vehicle 76 dB A 82 dB A

*Measured 50 feet from center of travel line under any

condition of operation.

(1)

(2) (3)

Table 11. California Motor Vehicle Noise Limits.

of new vehicles, many of the States and some of the cities are issuing regulations in sort of a programmed de-escalation

if you will. By way of comparison in Table 12, California, Chicago, Boston all start out at about the same level, and

end up at about the same level, but they get there by

slightly different means. The implications for the industry here are quite severe in terms of their lead time to produce new vehicles. Table 13 gives a compilation of some of the State transportation noise regulations. The X's show in what areas these states have transportation noise regulations. California has a rather unique regulation on airport noise whicn will be discussed beluw.

California, in its standard on airport noise, uses A- weighted levels which are converted into a Single Event

Noise Exposure Level (SENEL) which is sort of the integral under the curve for a single fly-by. This is converted into an hourly noise level which is an energy-weighted average

over an hour. Daytime, evening, and nighttime weightings

are applied to yield a 24-hour Community Noise Exposure

Level (CNEL). This value can be converted to an annual community noise exposure level, where you take the CNEL average over an entire year. (See Table 14 for a sum- mary of this discussion.) The implications for the measure- ment procedure have to do with instrumentation. A fair commitment of instrumentation is required. There arc instruments coming out to measure these values, but there

are no performance specifications at the present tim.e. ANSI

is looking at these instruments and is trying to develop

performance requirements for the instrumentation. One

reason that this is much more important than it mighi

Definitions;

(1) Noise exposure level (NEL) - accumulated noise

level, A-weighted Level (in dB re IQjjN/m- and I second).

Single event noise exposure level (SENEL) - NEL

of a single event (flyover). Hourly noise level (HNL) - Average noise level over an hour

{2)

(3)

HNL = 10 log (1/3600) I antilog (SENEL/ 10)

Class California Chicago Boston (4) Daily community noise equivalent level (CNEL) - Average noise level over a day, with evening and MOTORCYCLES: night periods weighted.

Until 1-1-73 88 dB A 88 dB A 88 dB A

After 1-1-73 86 86 86 CNEL = 10 log (1/24) [ 2 antUog (HNLD/10) +

After 1-1-75 80 84 84

After 1-1-77 75 75 75

3 Z antUog (HNLE/10) + 10 ZantUog (HNLN/10)]

LIGHT VEHICLES

Until 1-1-73 86 dB A 86 dB A 86 dB A

After 1-1-73 84 84 84 WHERE HNLD = HNL, 0700-1900

After 1-1-75 80 80 80 HNLE = HNL, 1900-2200

After 1-1-77 75 75 75 HNLN = HNL, 2200-0700. HEAVY VEHICLES:

(10,000#)

(5) Annual community noise equivalent level (annual (6,000#) (8,000#) CNEL) — average noise exposure over a year. Until 1-1-73 88 dB A 88 dB A 88 dB A

After 1-1-73 86 86 86 Annual CNEL = 10 log (1/365) 2 antUog (CNEL/10)

After 1-1-75 83 84 84

After 1-1-77 80 75 75 Table 14. California Noise Standards for Airports.

Table 12. Noise Limit Comparisons —

New Motor Vehicles.

Vehicle Vehicle Snowmobile Snowmobile Aii- Opetation Sales Operation Sales Ports

California X X — — X

Colorado XXX XX Minnesota X X — — —

Connecticut X — X —— —

Indiana X — — — —

Pennsylvania X X — — —

Idaho — — — — —

New York X — — X

Montana — — — X —

Massachusetts — — X X —

initially appear is that EPA is considering using very similar methodology in their levels document. There is concern in having the EPA regulations on specific sources be compatible with the California regulations. This might mean for instance, that if you wanted to rate the noise level of an automobile, you might want to have an energy averaged

level over a typical operating cycle so that you can project hourly noise exposure levels. Then, by knowing the amount of hours cars operate, you could ultimately predict community noise exposure levels. Thus, there are many implications for the measurement procedure that

will require investigation.

Table 13. State Transportation Noise Regulations.

83
Table 1 5 is a summation of local transportation noise

regulations. Vehicle operation and vehicle sales are sort of grouped together because many of the cities have differ- ent regulations. There are a number of other cities that have general (speciHc sound level requirement) regulations

somewhere in the ordinance.

City noise regulations have an interesting history. Some

years ago, in the zoning area, all of our regulations were more of a nuisance type regulation. It was a general "thou

shalt not co;iimtt noise" sort of commandment that people were supposed to comply with. Then in the mid-50's, the Armour Research Foundation came out with an octave- bnnd zoning sort of regulation that was adopted by a number of cities and that is reflected in the statistics in Table

16. In recent years there's been more and more of a trend toward A-weighted sound levels and, as can be seen under motor vehicles and aircraft, everything is in terms of A-weighted sound levels.

Vehicle Vehicle Snowmobiles Powered

Operation Sales and/or Off-Road Boats

Vehicles Chicago XXX X

Boston — X — —

New York City X — —

Minneapolis — X — —

Oahu X — X

Washington, D.C.* XX

*Proposed

Other Cities with General (Quantitative) Vehicle Noise Laws: Ann Arbor, Mich. > Walla Walla, Wash.

Pocatello, Idaho Seattle, Wash.

Idaho, Falls, Idaho Pullman. Wash.

Cincinnati, Ohio Ancorage, Alaska Omaha, Nebraska Boulder, Colorado

Peoria, Illinois Table 15. Local Transportation Noise Regulations.

With regard to building codes. New York City has had a noise regulation in their building code for several years. Chicago, if they have not already, is about to implement some noise control regulations in their building codes. And

that seems to be the trend. There is a definite leaning toward A-weighted levels but there is beginning to be a consideration of the temporal aspects of noise. In the case of HUD. the level exceeded eight hours a day. or the amount of hours that 65 dB A is exceeded is the quantity

being measured. In the case of the Federal Highway Administration, it is L 10 , the level exceeded 10% of the time.

In the case of California and some of the EPA regulations, weighted averages over long periods of time are investigated. There is some interest, of course, in the more complicated

measures such as Robinson's Noise Pollution Level from

England, that takes into account not only the mean level or energy average level, but some measure of the variation of the level with time.

Finally, in addition to moving sources, Chicago, Boston, New York City and others, are attempting to enact noise

regulaiionj or. iiatioaafy jquipiriiiit, co.isi.uctioii equip- ment for example.

That, in general, is an overview of some of the things

that are happening in the area of noise regulations. As mentioned previously, it has tended to dwell more on the Federal regulations than on the State and local regulations. There is a definite trend that one can see, toward using

A-weighted sound levels. Some specific measurement re- quirements on instrumentation are becoming apparent, and

as the regulations begin to encompass stationary sources, measurement methodology that adequately measures the noise emission from a product in a way t.iat will correlate with the community response will need to be developed and

verified.

NOISE REGULATIONS

dB A dB C Linear Octave Octave Band

Band & dB A Totals Zoning 24

Vehicle 21

Aircraft 4

Building I

Totals 50

Table 16.

2

36

12

12

71

214

5

101

Measurement Method (from: Bragdon, C.R., Municipal

noise ordinances, Sound and Vibration 7 ( 12}, 18 (December 1973).

84
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Hudson, P. A., National Measurement

System study on medical ultrasonics,

NBSIR 75-937 (National Bureau of

Standards, Washington, D. C, February

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Johnson, J. C, and Stuart, A. D. (eds.)» Report on the Conference on Acoustics and Societal Problems , Arden

House, Harriman, New York (The

Acoustical Society of America, New

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Systems, E317-68 (American Society for

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Fabricating and Checking Aluminum

Alloy Ultrasonic Standard Reference

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Materials Recommended Practice for

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Reference Blocks Used in Ultrasonic

Inspection, E428-71 (American Society

for Testing and Materials,

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Immersed Ultrasonic Testing by the

Reflection Method Using Pulsed

Longitudinal Waves, E214-68 (American

Society for Testing and Materials,

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revised 1974).

[9] American National Standard Method for

the Calibration of Microphones,

51. 10- 1966 (American National

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York, 1966, revised 1971).

[10] International Electrotechnical

Commission Recommendation on Precision

Sound Level Meters, Publication 179

(International Electrotechnical

Commission, Geneva, Switzerland,

1973).

[11] American National Standard

Specification for Sound Level Meters,

SI. 4-1971 (American National Standards

Institute, New York, New York, 1971).

[12] International Electrotechnical

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Half-Octave, and Third-Octave Band

Filters Intended for the Analysis of

Sounds and Vibrations, Publication 225

(International Electrotechnical

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[13] American National Standard

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85
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,

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4-6 (July 1975); Buyer's Guide to Systems for Noise and Vibration

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1975).

[26] Corliss, E. L. R., and Winzer, G. E.,

Study of methods for estimating

loudness, J. Acous. Soc. Am. 38,

424-428 (1965).

[27] American National Standard

Specifications for Audiometers,

S3. 6-1969 (American National Standards

Institute, New York, New York, 1969).

[28] Leasure, W. A., Jr., Fisher, R. L.,

and Cadoff, M. A., Evaluation of

commercial integrating- type noise

exposure meters, NBSIR 73-417;

EPA-550/9-73-007 (National Bureau of

Standards, Washington, D. C. , December

1973) .

[29] Cook, R. K. , Absolute pressure

calibration of microphones, J. Res. NBS 25, 489-505 (November 1940).

[30] Society of Automative Engineers

Exterior Sound Level Measurement

Procedure for Small Engine Powered

Equipment, Recommended Practice J1046

(Society of Automotive Engineers, New

York, New York, 1974)

.

[31] Holmer, C. I., and Kilmer, R. D., A proposed experiment to evaluate

environmental dependence of the

measurement of noise from medium and

heavy duty trucks, NBSIR 76-1138

(National Bureau of Standards,

Washington, D. C, September 1976).

[32] Mayo, L. H., and Ware, R. C,

"Environmental noise regulatory

structure," Appendix D in Report on the Conference on Acoustics and

Societal Problems Arden House,

Harriman, New York (The Acoustical

Society of America, New York, New

York, June 1972).

[33] Bragdon, C. R., Municipal noise

ordinances: 1974, S/V Sound and

Vibration 8(12), 28-29 (December

1974) .

[34] Buckingham, E., Theory and

interpretation of experiments on the

transmission of sound through

partition walls, NBS Scientific Papers

20, s506 (1925).

[35] Chrisler, V. L., and Snyder, W. F.,

Recent sound-transmission measurements

at the National Bureau of Standards,

J. Res. NBS H, RP800 (1935)

.

86
London, A., Methods for determining

sound transmission loss in the field,

J. Res. NBS 26, 419-453 (1941).

Performance Data, Architectural

Acoustical Materials, AIMA Bulletin

No. XXXIII (Acoustical and Insulating

Materials Association, Park Ridge,

Illinois, 1973).

1973-1974 Design Data Manual (Gypsum

Association, Chicago, Illinois).

Warnix, J. L., and Sharp, B. H., Cost

effectiveness study of major sources of noise: Vol. I-Medium and heavy

trucks. Research Report No. WR 73-10

(Wyle Laboratories, El Segundo,

California, October 1973).

Hearing Levels of Adults, Series 11,

Number 11 (National Center for Health

Statistics, U. S. Department of

Health, Education, and Welfare,

Washington, D. C, October 1965).

Human Communications and Its Disorders

-- An Overview, NINDS Monograph 10 (National Institutes of Health, U. S. Department of Health, Education, and

Welfare, Bethesda, Maryland, 1969).

OSHA proposes noise rule retaining 90

dBA eight-hour exposure limit. Noise

Control Report 3 (22), 211-212

(October 28, 1974)

.

Hearings of the Joint Committee on Atomic Energy on the loss of the USS

Thresher, 88th Congress of the United

States, as reported in Bentley, J.^

The Thresher Disaster: The Most

Tragic Dive in Submarine History

(Doubleday, New York, New York, 1975)

.

Weissler, P. G. , Zerdy, G. A., and

Revoile, S. G., Consumer product

noise: A basis for regulation, NBSIR

74-606 (National Bureau of Standards,

Washington, D. C, November 1974).

Standards of the Intersociety

Committee on Audiometric Technician

Training, Am. Indus. Hygiene Assn. J. 27, 303-304 (May-June 1966).

Occupational Exposure to Noise, Report

HSM 73-11001 (National Institute for

Occupational Safety and Health, U. S. Department of Health, Education, and

Welfare, Washington, D. C, 1972).

[47] Botsford, J. H., Proposed OSHA noise

regulations, S/V Sound and Vibration

7(11). 24-29 (November 1973).

[48] Lindsay, R. B., The National Bureau of

Standards and its new home, J. Acous.

Soc. Am. 40 (4), 949 (November 1966).

[49] American National Standard Methods for

the Determination of Sound Power

Levels of Small Sources in

Reverberation Rooms, SI. 21-1972

(American National Standards

Institute, New York, New York, 1972).

[50] Lubman, D., Review of reverberant

sound power measurement standard and

recommendations for further research,

NBS Technical Note 841 (National

Bureau of Standards, Washington, D. C, August 1974).

[51] U. S. Federal Register , Method for

determining the sound pressure level

produced by toy caps, 36, No. 134,

Section 191.17, 13030 ITuly 13, 1971).

[52] Cadoff, M. A., Mathews, D. E., and

Blomquist, D. S., Development of a procedure for measuring the noise of

paper caps, NBS Technical Note 793

(National Bureau of Standards,

Washington, D. C, October 1973).

[53] Cadoff, M. A., and Blomquist, D. S.,

Measurement methodology for determining the sound output of toy guns,

NBSIR 74-619 (National Bureau of

Standards, Washington, D. C, August

1974).

[54] Society of Automotive Engineers Method

for Measuring the Sound Level of

Highway Truck Tires, Recommended

Practice J57 (Society of Automotive

Engineers, New York, New York, 1973).

[55] Leasure, W. A., Jr., Quindry, T. L.,

Mathews, D. E., and Heinen, J. M.,

Interior/exterior noise levels of

over-the-road trucks: Report of

tests, NBS Technical Note 737

(National Bureau of Standards,

Washington, D. C, September 1972).

[56] Leasure, W. A., Jr., and Quindry, T. L., Methodology and supporting documentation for the measurement of noise

from medium and heavy trucks, NBSIR

74-517 (National Bureau of Standards,

Washington, D. C, June 1974).

87
[57] Path, J. M., Blomquist, D. S., Heinen,

J. M. , and Tarica, M., Measurements of

railroad noise — line operation, yard

boundaries, and retarders, NBSIR

74- 488, EPA-550/9-74-007 (National

Bureau of Standards, Washington, D. C. , December 1974)

.

[58] Holmer, C. I., Measurement methodology

and supporting documentation for

portable air compressor noise, NBSIR

75- 653 (National Bureau of Standards,

Washington, D. C, January 1975).

[59] BB&N data indicate industry could meet

85 dBA rule in five years for

$8-billion. Noise Control Report 5^(2),

11-12 (January 19, 1976).

[60] Audiometer specifications chart.

Hearing Instruments 30, 18-21 (1973).

[61] Noise Pollution Control, Report No. 418 (Stanford Research Institute,

Menlo Park, California, October 1972).

[62] Cook, R. K., and Schade, P. A., New

method for measurement of the total

energy density of sound waves, in

Proceedings of Inter-Noise 74,

Washington, D. C, 101-106 (September

30-October 2, 1974)

,

[63] Baron, R. A., The Tyranny of Noise

(St. Martin's Press, New York, New

York, 1970).

88
NBS-,114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR R1-:P0RT NO.

NBSIR 75-938

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITl.H AND SUBTITLE

National Meas\irement System for Acoustics

5. Publication Date March 1977

6. Performing Organization Code

7. AUTHOR(S)

David S. Pallett and Marilyn A. Cadoff

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proic-ct/Task/Work Unit No. 2004150

11. (ontr.ict /Grant No.

„

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

This report describes acoustical measTorement processes which are motivated "by societal concern over noise and which have broad relevance

to our contemporary technological society. The emphasis of this

study of the National Measurement System for Acoustics has been to

review the status of the system in order to determine the adequacy

of these important physical measurements and to promote improvements

within the measiarement system. The relevent physical quantities

are indicated, and the interactions occuring between participants

as well as the roles of acoustical standardization institutions are

specified. -Tech-nological, social and economic impacts are outlined.

Finally, the status and trends of the system and the NBS role in

adapting to changing technology are discussed.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Acoustics, acoustical measurements, audiometry, national measurement system,

noise, noise control, noise emissions, sound, sound level meters.

18. AVAILABILITY IX I Unlimited

1 j I'"or Official Distribution. Do Not Release to NTIS

[ ] Order I'rom Sup. of Doc, U.S. Government Printing Office

Wa.shinKton. D.C:. 20/i02. SD Cat. No. CI 3 ^ j Order I' rom National Technical Information Service (N'I'IS) Springfield, Virginia 22151

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(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

94

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