The program of research on building materials and structures imdertaken by the

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C. W. Chamberlain,

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Hugh L. Dryden,

National Bureau of Standards.

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P. H. Bates W. E. Emley A. S. McAllister

H. C. Dickinson G. E. F. Lundell H. S. Rawdon

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is cooperating with the National Bureau of Standards in studies of wood constructions.

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UNITED STATES DEPARTMENT OF COMMERCE • Harry E. Hopkins, Secretary

NATIONAL BUREAU OF STANDARDS • Lyman J. Jiriggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS17

Sound Insulation

of

Wall and Floor Constructions

by V. L. CHRISLER

ISSUED MARCH 28, 1939

The National Bureau of Standards is a fact-finding organization;

it does not "approve" any particular material or method of construction. The technical findings in this series of reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, WASHINGTON, D. C. • PRICE

• 1939

10 CENTS
Foreword

For about sixteen years the National Bureau of Standards has made measurements

on the sound-insuhiting value of different materials and types of construction. Many

of the measurements were made in cooperation with manufacturers of building materials;

others were made by the Bureau to advance our knowledge of the sound-insulating

properties of representative types of construction.

The funds available for the research program on building materials and structures with special reference to low-cost housing were insufficient to permit a new experimental

program on sound insulation in view of more urgent needs. However, the results of

the past experience of the Bureau are brought together in this report in one place so that the information may be more useful to architects and engineers.

The results show that a wall or floor which is approximately homogeneous must be

excessively heavy to be a good sound insulator. If the wall or floor is built in layers

which are loosely connected, the sound-insulating properties are greatly improved.

Thus, method of construction is more important than nature of material. Small openings may almost completely destroy the sound-insulating value.

This report also contains a general discussion of the principles of sound insulation.

Lyman J. Briggs, Director.

[IT]
Sound Insulation of Wall and Floor Constructions

by V. L. CHRISLER

CONTENTS

Page

Foreword ii

I. Introduction 1

II. Location of building 2

III. Location of looms within a building 2 IV. Factors which control the transmission of sound through walls and floors 3 V. Homogeneous walls 3 VI. Nonhomogeneous walls 4

1. Lath and plaster walls 4

2. Masonry walls and floors 5

Page VII. Impact noises and methods of isolating

them G VIII. Eff'ect of openings and methods of computing results 7 IX. Masking effect 10 X. Maximum noise levels which should be

tolerated 11 XI. Panel construction and transmission loss in decibels 11 XII. Literature references 31

ABSTRACT

This report summarizes the data obtained in tests at the National Bureau of Standards on the sound

transmission of wall, partition, and floor panels and

gives a general discussion of the principles of sound

insulation. Attention is called to the desirability of constructing buildings, in which quiet conditions are

essential, in locations where the noise level is not high

and of locating rooms intended to be especially quiet in parts of the building where there will be the least dis- turbance from the usual noises in the building. A general

discussion is given of the factors which determine the

transmission of sound through partitions. Impact

noises and methods of insulating against them receive

special mention. The importance of eliminating small

openings, which may almost completely destroy the sound insulating value of a wall, is illustrated by ex- amples. It is pointed out that the required sound

insulation is less, the greater the normal noise level within the room.

I. INTRODUCTION

In the design and construction of low-cost row houses and low-rental apartments as well

as better types of construction, attention

should be given to preventing the transmission

of sounds to insure privacy between rooms in

the same apartment and between adjoining

apartments. It is evident in much existing

construction that more thought should have

been given to the design and construction of

partitions, party walls, and floors, as regards

sound transmission.

In many localities outside noises have greatly

increased during the past few years because

of heavier traffic, especially large busses and

trucks. In addition, more electric and mechanical equipment is being used which increases the

amount of noise produced within the building.

At the same time, for reasons of economy, there

has been a tendency in modern construction

to make the walls and floors as thin as practicable, which has resulted in additional trans- mission of sound. As a result of the inferior

type of construction and increased noise level within the building, the value of the property,

in many cases, is decreased. Frequently,

tenants have moved to another building, hoping to be annoyed less by noises originating

outside of their rooms. There is a growing

demand for better sound insulation.

To aid in obtaining the necessary data for the design of structures which would have a

satisfactory degree of sound insulation, in 1922

the National Bureau of Standards constructed

equipment by means of which measurements

could be made of the sound insulation of

different types of construction. A large number of different types of partitions and floor

[1]
structures have been tested. These tests have

been made on constructions ranging from heavy

masonry to glass and tliin fiberboards, on

customary types of wall and floor structures,

and on modifications of the customary types.

A large portion of this work has been made

possible by the cooperation of manufacturers

of building materials[l].^ This report contains

the results of measurements on all constructions tested that are likely to be of interest in

any type of building.

The problem of sound insulation is a very

difficult one, as there are many unknown

factors, and it is generally unpossible to predict

with any degree of certainty whether or not

a partition will be a good sound insulator. As a

result of the sound-transmission measurements

which have been made, it is possible to make a more intelligent estimate than heretofore.

There still remain, however, many elements of

uncertainty. Before presenting the numerical

results of the measurements of various constructions, the general principles of securing quiet

buildings will be discussed.

II. LOCATION OF BUILDING

When planning a building in which it is desired to keep the noise level as low as possible, one of the first things that should be considered

is location. The requirements of some buildings, such as hospitals, schoolliouses, court- houses, etc., are such that they should not be

located on streets wbere the noise level is high

unless extra precautions are taken to insulate

the building against external noise. If it be- comes necessary to locate such a building on a

noisy street, either the windows should be

eliminated and artificial illumination provided

or double windows should be used and precautions taken to eliminate any leakage of sound

around the windows. In either case mechanical

ventilation must be specified.

Wliere a building is located close to railway

lines, subways, elevated railways, or streets where heavy trucks are passing, it is frequently

necessary to use special precautions to prevent

vibrations being transmitted through the foun1 Figures in brackets indicate the literature references at the em! of this paper.

dation into the structure. This is an important

problem [2] but no attempt will be made to' discuss it in this report.

III. LOCATION OF ROOMS WITHIN A , BUILDING

I Many of the more difficult problems of sound

insulation can be avoided if care is taken as toi the location of rooms within a building. Foi^

instance, in some Government buildings there are one or two courtrooms or hearing rooms

where a low noise level is desired and a large

number of other rooms used for purposes where

the noise level is relatively high, for example, rooms in which typewriters and other office? equipment are to be used. Frequently, a

building of this type has an interior court.f Under these conditions it might be possible to locate the courtroom, hearing rooms, and pri-i

vate offices around the interior court. In the

past many buildings have been designed so that rooms facing on a court were the least desirable.

From the standpoint of soimd insulation, however, these rooms should be the most desirable, as it is generally possible to have the noise level in these rooms much lower than in rooms facing on the street. It must be emphasized, however, that one room located on such an interior

court may destroy the quiet of all other rooms

located on the court if this room is a source of

noise. ; Similar considerations apply to the location

of rooms within dwellings, and the architect can often make a house more comfortable by

suitable location of sleeping quarters, for

example, with respect to the prevalent sources'

of noise.

A type of noise which is very disturbing and

often difficult to eliminate is that from mechanical equipment. Frequently the mistake

is made of locating mechanical equipment on some of the upper floors and then locating a room directly below in which a low noise level is

,

desired. It is true that it is generally possible

to place such mechanical equipment on specially

designed machine bases which will eliminate

most of the noise in the room below. However, if the locations of the two rooms were re- versed the problem would be much simpler.

[2]
IV. FACTORS WHICH CONTROL THE

TRANSMISSION OF SOUND THROUGH

WALLS AND FLOORS

Noise may enter a building by the following means:

1. By transmission of air-borne sounds

tlirougli openings, such as open windows or

doors, cracks around doors, windows, water

:j pipes, conduits, or the ducts of ventilating

systems, etc.

2. By transmission of structural vibrations

from one portion of the budding to another.

3. By direct transmission tlirough the various

portions of the building structure, which act as diaphragms set in motion by the sound waves

striking them.

The method of preventing the transmission

of sound by the first means is quite evident, but

it is not always easy to control these conditions.

However, cracks can be reduced to a minimum

and where a high degree of sound insulation is desired windows should be eliminated wherever

possible. Ventilating ducts present a serious

problem, but by mserting a properly designed

acoustic filter in the duct, most of the noise can

be eliminated.

Prevention of sound transmission by the

second means is a structural detail wliich should

be taken into consideration when the building is designed. Some materials do not transmit

vibration as readily as others and this difference

in the materials can sometimes be used to advantage. One of the most common methods

is the use 6f a nonhomogeneous structure, or when possible, the complete separation of the

two parts of the structure. This problem will be discussed further under the topic of Impact

Noises.

The prevention of sound transmission by the

third means is a problem wliich it has been

possible to study in the laboratory to better

advantage than when somad is transmitted by

the other methods. By sound insulation of a

wall, partition, or floor is meant the insulation

mth respect to the transmission of sound by

tliis means. In an attempt to understand this

diaphragm action, let us consider some of the

factors which control the transmission of sound

through a panel. Let us consider how sound

passes through a sheet of wmdow glass. The

sound energy is transmitted to one side of the

glass by air. The impact of the successive

sound waves upon the glass causes it to be set

in motion like a diaphragm, and because of this

motion, energy is transmitted to the air on tlie opposite side. The amount of energy trans- mitted through the glass depends upon the

amplitude of vibration of the glass. This in

turn depends primarily upon four things—the

initial energy striking the glass, the mass of the

glass, the stiffness of the glass, and the method

by which the edges of the glass are hold, especially as it affects the damping of the motions

of the glass. There is a fifth factor wliich is occasionally of importance. When the sound

consists primarily of a single frequency there is a possibility that the diaphragm may be in resonance with this frequency. In this case a

very large part of the sound energy is trans- mitted. Normally the resonance frequency of

any part of a building is much lower than the

frequencies of any of the ordinary sounds, and

hence this condition will not generally be of

importance.

V. HOMOGENEOUS WALLS

From work that has been done in the laboratory on homogeneous walls of various types, it has been determined that the weight of the

wall per unit area is the most important factor

in determining its sound insulation. Of

secondaiy importance are the nature of the

material and the manner in which it is fastened

at the edges. There is a rather popular misconception that fiberboard and sheet lead have

special properties as sound insulators. Actually, if only the soimd insulating properties of the

materials by themselves are considered, a sheet

of steel is a slightly better sound insulator than

a sheet of lead or fiberboard of the same weight

per square foot, because of the greater stiffness of the steel, but the difference is not usually

great enough to be of practical value. In small

panels the manner of clamping the edges is of

importance, but for a large panel the manner in

which the edges are held makes but little differ- ence in its value as a sound insulator.

However, attention should be called to the

fact that the sound insulation factor (transmission loss in decibels) for homogeneous walls

[31
is not directly proportional to the weight per

unit area, but increases less rapidly than this

factor, actually being proportional to the

logarithm of the weight per unit area. This means that a high degree of sound insulation

cannot be obtained in a homogeneous wall

unless the wall is made exceedingly heavy.

VI. NONHOMOGENEOUS WALLS

Shortly after the study of sound insulation was undertaken it was found that the insulating value of a wall of given weight could be

increased considerably if the wall were broken

up into two or more layers. The surface on

which the sound strikes is set in vibration as a diaphragm, but the energy from this surface

has to be transferred to the next layer and then

to the other side. By a proper combination of

materials this energy transfer may be made

quite small, and the smaller this transfer the

better the wall is as a souiid insulator. When

a wall is thus broken up into layers, the problem becomes more complicated and it is more

difficult to predict what the sound insulation

factor will be.

I. Lath and Plaster Walls

A wood-stud partition, with either wood,

metal, or gypsum lath, is an example of a construction for which it is difficult to predict the

sound insulation. Many factors affect the

sound insulation of such a structure. With

walls of ordinary stud construction we have

two plaster diaphragms which are on opposite

sides of the partition and have common supports, where they are attached to the studs.

Sound energy can then be transferred by two

different paths from one side of the partition

to the other. The energy of vibration of the

plaster on one side can be transferred either to the studs and then across to the plaster on the

other side by solid conduction, or it can be

transferred to the air between the two plaster

surfaces and then from the air to the second

plaster surface. By experiment, it has been

shown, for usual plaster construction on wood

studs, that most of the energy is transferred

through the studs and only a very small proportion through the air. Keepmg this in

mind, we may draw a few general conclusions.

First, the stiffer the stud, which is the common

support for the two surfaces, the smaller the

amplitude of vibration, hence, the better the

sound insulation. Second, if the plaster is rather weak and flabby and has considerable

internal friction, a considerable portion of the

energy striking it will be absorbed by internal

friction and only a small portion will be trans- ferred to the stud and from there to the other

side. Hence, the stronger the plaster the poorer

it will be as a sound insulator. The practical

difficulty that arises here is that in the attempt

to secure good sound insulation by weak

plaster, the plaster may become too weak to withstand the abuse that a wall generally

receives.

A rather interesting development of this idea

of reducing the coupling between the wall

covering and the stud has taken place in the

last few years in the use of gypsum lath or gypsum plaster board. When gypsum lath was

first introduced the usual method of attaching

it to the studs was by nailing. This gave a

rigid attachment to the studs which was undesirable from the standpoint of sound insulation. An improvement was made by attaching

the gypsum lath to the stud with a resilient

clip which allowed some relative movement between the lath and the stud. As these clips were a patented article, other methods of ac- complishing the same result in a slightly differ- ent manner have been tried, one of which was

to use a large-headed naU driven between the

pieces of gypsum lath instead of through them.

Another method was to use a stiff clip. Neither

the large-headed nail nor the stiff clip forms a

rigid fastening between the gypsum lath and

stud. Hence, a wall constructed in this manner

proved to be a better sound insulator than one

with the gypsum lath nailed in the usual manner. The resilient clip, however, gives some- what better results. As in ordinary wood stud construction, most

of the sound is transmitted through the stud ; attempts have been made to improve such a

partition by using separate studding for the two

sides. This staggered-stud construction always

shows some improvement over a single stud,

but not as much as one might expect, for in this case considerable energy is transmitted

[i]
through the coniiiion connections at tlie cciUng

and floor. There is a ratlicr general misconception that

the sound insulation value of an ordinary

plaster wall can be greatly increased by using some kind of falling material between the studs.

While such a filler is usually advantageous as a heat insulator, the same cannot always be said

of it as a sound insidator. In many cases the

empty air space is acoustically the best construction. For lighter partitions a filler may be

of advantage, but even here much depends upon

its nature and properties. If it packs down so that it becomes rather solid, it will act as a tie between the two surfaces and frequently do more harm than good. If it is a material which

is fairly elastic, so that it stays in contact with

the surface layer of the partition and exerts some

pressure, and if it has considerable internal

friction, it may materially damp the vibration

of the partition surface and thus improve the

sound insulation of the partition.

Unfortunately, we have not sufficient data at present to enable us to determine without

measurement exactly what kind of a material

should be used as a filler and how tightly it should be packed between given surfaces so as

to obtain maximum sound insulation.

2. Masonry Walls and Floors

For heavy building construction, such as load-bearing waUs, a double wall will increase

the sound insulation, but the fillers which have

been tried seem to be of little value. However,

with a masonry wall satisfactory sound insulation can be obtained in other ways wliich often

give better results than a double waU.

In most cases it is customary to apply the

plaster directly to the masonry. In this case, the wall becomes a solid unit and its weight is the most important factor. If only 3- or 4-inch

tiles are used there is not sufficient weight to give satisfactory sound insulation in most

cases. The problem then is one of attaching

the plaster surfaces to the masonry core so as

to secure as much sound insulation as possible.

To obtain some idea of the eft'ect of keeping

the plaster surface as independent of the

masonry as possible, wood furring strips were

tied to a 4-inch tile wall with wires which had

been embedded iji the mortar joints. Waterproofed paper was nailed to these furring

strips, then metal lath ajid plaster were applied

(fig. 1). The object of using paper was to prevent the plaster from pushing through the

metal lath and bonding to the masonry core.

It was found that this type of wall was a

trifle better than an 8-inch brick wall, although

it weighed approximately only one-third as much. When this was first tried out, it was

believed that the method of attaching the

furring strips might make considerable dif- ference in the sound transmission. The measurements which have been taken indicate that

this feature is of minor importance. There

are several patented methods of attaching

furring strips, but it is believed that for this

type of wall construction there is little dif- ference in the sound insulation values of these

4"CLAY TILE'' Figure 1.

Masonnj wall with furred-out plaster.

systems as long as the plaster surface is held

away from the masonry, not maldng direct

contact at any point.

W^hen these furred-out masonry panels were

in position, conversational tests were made as

well as the usual sound-transmission measurements. In every case it was found that the

sound of a conversation carried on in an

ordinary tone of voice was barely audible to a

listener on the other side, provided he was

listening intently, but that he was unable to understand anything that was said. Moreover,

if there were the slightest noise in the listener's room, he failed to detect any sound of the conversation on the other side of the panel. It should be borne in mind that the rooms in

which these tests were made had bare concrete

walls and were so sitiiated that no distracting

noises entered from the outside. If these rooms had contained draperies and furniture

to absorb part of the sound, and if there had

been some noise due to traffic or other causes, the conversation would have been inaudible.

It was also found that sound insulation of a masonry floor could be greatly improved by

using a floating flooring and a suspended ceiling

[5]
- PLASTER Figure 2.

Floating floor and suspended ceiling

(fig. 2). The method of attaching the nailing

strips is probably of secondary importance, as

in the case of furring strips attached to masonry

walls. For the suspended ceiling, rigid hangers

should not be used. Any flexible supports,

such as springs or wires, which do not give a

rigid connection should be satisfactory.

From the above discussion it is evident that

the best form of sound insulation for masonry

would have the following construction. What

might be called the "core" of the building would

be built in the customary manner, that is, with walls and floors of masonry. From this

point the procedure would be different. The

rooms would be formed of rough masonry and

inside of these the finished surfaces would be

applied. Instead of plastering on the masonry

to form the wall and ceiling surfaces, these

surfaces would be furred out so that the finished

plaster surfaces would not be in direct contact

with the masonry. Likewise, the floor w^ould

be of the "floating" type. In other words,

we might picture it as a box within a box, the

inner box to be attached to the outer one at as few points as possible, with these connections no more rigid than absolutely necessary.

VII. IMPACT NOISES AND METHODS OF

ISOLATING THEM

Noises caused by impact, such as walking or the moving of furniture, or by a direct transfer

of vibration from machines and musical instruments, such as pianos, radios, etc., form another

class of noises which are more difficult to insulate than air-borne noise. These noises are also more difficidt to study in the laboratory due to the limitation in size of test models. We all know from experience, that a machine often

sounds as noisy in the room below as in the room where it is located. For experiments with

impact noises, a special machine (fig. 3) was

built. It consists of a set of five rods wliich are

raised in succession by a set of cams. The

speed of the cams is such that one rod is allowed

to fall every fifth of a second. On a wood floor

it is quite noisy—so much so that it is rather

difficult to hold a conversation in the room. With a floor built of wood joists there is some

reduction of the noise transmitted through the

floor panel, but the transmitted noise is still decidedly annoying. Some contractors build a

so-called "floating floor" by laying a rough

flooring upon the joists, upon this a layer of

fiberboard, and upon the fiberboard a finish

floor which is nailed through the fiberboard to the rough floor. This form of construction was

tested by the impact machine to determine

whether such a structure was better, but it was

found that the same percentage of sound was

transmitted (within experimental error) as without the layer of fiberboard.

In another experiment a rough subflooring was laid, upon which was placed the fiberboard.

On the fiberboard were laid nailing strips to which the finish floor was nailed. Such a construction is an approximation to a "floating

floor." It is believed that the method of fastening these nailing strips is not of great importance. The strips can be nailed every 3 or 4

feet or held in position by various arrangements

of straps. This same result can be accomplished by the use of springs or small metal

chairs containing felt. For air-borne noises

such structures are quite satisfactory. Under

usual conditions, a conversation carried on in an ordinary tone of voice is not audible through

them. For impact noises, however, such strucFlGURE 3-

Machine for producing impact sounds.

[6]
I tures are rather disappointing. They are somej what of an improvement over the usual wood

structure, but footsteps can be easily heard

, through them.

The next attempt to improve such structures,

j consisted of separating the ceiling and floor

joists. Tliis gave about the same result as the

j single set of joists and floating floor, although

I not quite as satisfactory. A floating floor was

j then added. This combination gave the best

j results that were obtained with wood joists and

j was very satisfactory as far as air-borne noises

j were concerned. The insulation value for impact noises, however, was not as great as could be desired.

Another type of floor which was studied was

1 masonry. When impacts were applied directly

I to the masonry floor, the noise in the room below was practically as loud as in the room where the

machine was located. A floating floor was then

built, residting in decided improvement. FinaUy, a suspended ceiling was added and this

, gave the best result which had been obtained

i (fig. 2). For one of the listening tests a radio

loudspeaker w^as used. The loudspeaker was

operated at a somewhat higher volume than is

j customaiy for home use, and when listening

through, the panel the sounds w^ere very faint. It is certain that if the test had been made anywhere except in a room which was absolutely

quiet, the radio could not have been heard at all. For impact noises this construction was not as good as for air-borne noises, but it was a decided

improvement over masonry slab. The noise

from the impact machine was distinctly audible,

but not loud enough to be very noticeable if two

people were talking in the room. The results in

this case were more satisfactory than for wood

joists.

In the foregoing discussion the difference between the noise levels in the rooms above and

below the floor panel only has been considered.

By changing the floor covering, the noise level

in both rooms may be greatly reduced, although

the insulation factor may not be changed enough

to be of any practical value.

For noises which originate from impacts on

the floor, the floor covering acts somewhat in the nature of a shock absorber. Hence, the

softer and more yielding the floor covering, the

less the amount of energy transferred to the

floor to be radiated as noise. For instance, the

noise produced by walking on a floor covered

with rubber or cork tiles is somewhat less than

that produced when walking on bare concrete; while that produced when walking on a heavy

carpet is very much less than that produced by

walking on a concrete floor. The amount of noise generated also depends

upon the type of object which strikes the floor. As two extremes, let us consider the leather

heel of a shoe with an iron clip on the bottom

versus a rubber heel. The impact of these two

kinds of heels on a concrete floor will produce a

noise level having a difference of several decibels. If the floor covering consists of rubber or cork tfles, the difference in the noise levels produced by these two types of heels is smaUer. If we use a still softer material for a floor covering,

such as a heavy carpet, the difference in the

noise levels produced by the two types of heels

becomes negligible. Considerable sound energy

may be transmitted thi'ough the legs of a piano

or radio into the floor. Tliis can be partly eliminated by putting the legs of the piano or radio

in caster cups and then putting rubber between

the caster cups and the floor. Vibrations from

macliinery which are carried into a budding

structui'e and cause noise throughout the building may be largely eliminated in a somewhat

similar manner. In tliis case a resihent mounting, having a considerable amount of internal

damping, is placed between the machine and

the building structure.

VIII. EFFECT OF OPENINGS AND METHODS OF COMPUTING RESULTS

In the foregoing discussion, the fact that all rooms have either doors or windows or both has

been ignored. A window' or a door in a partition will frequently transmit more sound than

the rest of the partition, although sealed around

the edges so that it is airtight ; hence, it may be

useless to do anything to the partition to improve its sound insulation as long as the door or window remains in the partition.

To bring out this pomt, it will be necessary to discuss rather briefly how to compute the total sound transmitted through a wall composed of several elements having dift'erent coefficients of

127200=—39 2 [7]
transmission and the manner in which these

results are usually expressed.

First, let us consider the usual manner of

expressmg values of sound insulation and why

they are expressed in that way. In most

cases, we are interested in the effect of sound

upon the human ear, therefore, an attempt has

been made to express the results so that they

are approximately proportional to what the

ear hears. It has been found that the ear does not respond in proportion to the energy

of the sound. As the energy of a sound in- creases steadily, the response of the ear fails to keep pace with it. There appears to be in

the ear a regulating or protective mechanism

which, like the weU-known mechanism of the

eye, protects the organ against excessive

stimulation. Experiment shows that the re- sponse of the ear is approximately proportional

to the logaritlim of the sound energy; that is, energies proportional to 10, 100, and 1,000

would produce in the ear effects proportional

to 1, 2, and 3, respectively.

A slight modification of this logarithmic

scale has come into general use to measure sound energy and the amount of noise reduction. It is called the decibel scale. This

scale merely multiplies the numbers of the

logarithmic scale by 10. The unit of this

scale, the decibel, is a rather convenient unit

as it is approxunately the smaUest change in

energy that the average ear can detect. For

this reason this unit has frequently been called a sensation unit.

The decibel scale is suitable for measuring

ratios of soimd intensity. To measure absolute

noise levels the zero value is assigned to a

definite level, i. e., a level of 20 decibels cor- responds to an energy 100 times that corre- sponding to the zero value.

To understand a little more clearly what is meant by different sound energies in decibels,

and how much this energy may be reduced by

a structure, figure 4 should be referred to. This has been made up from the results of

various noise measurements and gives an approximate idea of the value of different noise

levels in decibels.

The noise-reduction factor as referred to in

this report is the difference in sound energy

Range of speech as usually

heard in conversation.

130 Threshold of painful sounds; limit of ear's endurance.

120 Threshold of feeling (varies with frequency). Airplane motor (1600 rpm) 18 feet from propeller.

Express train passing at high

speed. 100 Loud automobile horn 23' away.

90

80 Hew York sutway.

l/.otor trucks 15' to SO'.

70 Stenograijhic room.

60 Average busy street.

lloisy office or department store

50 i.loderate restaurant clatter.

Average office.

40

Soft radio music in apartment. Average residence.

20 Average whisper 4' away.

10 Rustle of leaves in gentle breeze.

Threshold of Audibility.

Figure 4.-Decibel scale of sound interiftities.

expressed in decibels, as a result of the presence

of the wall or panel between the sound and

hearer.

It can be shown [3] that if Ei is the energy

level of the noise outside of a room, and E2

the energy level in the room

[8]
Ei Ti.Si+T2S2+r3S3'

where A is the total absorption in tlie room,

S\, 8-2, S3, etc. are the areas of the various portions

of the walls, such as walls, windows, etc., and

Ti, T2, T3, are their respective coefficients of

sound transmission or acoustic transmittivity,

that is, the fraction of the incident sound energy

that is transmitted through the panel. The

value of r is seldom published. Instead, the

value of 10 logio l/r, which is called the trans- mission loss in decibels, is given. The denominator (TiSi+r2S2-|- . . . ) is termed the

total transmittance, and will be represented by

T. Equation 1 can be rewritten

EJE2=A/T. (2) The noise-reduction factor in decibels, wliich

is the difference between the noise level outside

of a room and the noise level in the room, is equal to10 (}og,oE,-\og,oE.2) = 10\og,oEJE2 = 10log:o^/T _ (3) and the quantity 10 logical/ T is called the

noise reduction factor. To illustrate the use of these formulas and

show the detrimental effect of doors and windows, let us assume the case of a brick building

containing a single room. The walls are of

8-inch brick and the roof a 6-inch reinforced- concrete slab. The total absorption in the room which has been acoustically treated is assumed to be 400 units. It is assumed also that the foimdations and floor are built in such

a manner that the amount of sound which

enters the room through the floor is negligible.

Assuming usual values for the transmission

losses through the various parts, we may

tabulate the separate items as follows:

Trans- Material Areas, s mission T T.S loss

ft' Decibels 8-inch brick walls, plus

plaster 1,200 54 0. 0000040 0. 0048 6-inch cement roof slab, plus plaster _ 600 50 . 000010 .0060 Windows _ 150 28 .0016 .24 Door . 21 35 . 00032 .0067

Total transmittance.

T, equals.- __. _ 0. 2575

Noise-reduction factor (in decibelsj = 10 logio(yl/T) = 101ogio(400/0.25S) =

31.9 decibels.

From the last column in the above table it may be noted that the windows admit many

times the amount of sound admitted by all of

the wall and ceiling structures, and that the

door admits more noise than either tlie walls or

ceiling.

If one window is open so that there is 1 square foot of open window, the transmission

loss through an opening like this is zero, hence

r = 1 and ts = 1. In other words, an opening of

1 square foot would transmit four times the

sound energy that is transmitted by the entire structure with closed windows. The noise re- duction factor with the partly opened windows

is dimmished to 25.0 decibels.

Frequently, the question arises as to how

such a computation would be made in the case

of an apartment room where one side is exposed

to street noise, with adjoining rooms on two

sides, and the fourth side adjacent to a corridor.

Let us assume the case of a rectangular room,

the width of which facing on the street is 10

feet, the length 12 feet, and the height 9 feet. Also, let us assume that the outer waU is a 13- inch brick wall having one window 3 feet by 5

feet, and that the interior walls are 4-mch clay

tile plastered on both sides, having one door 3

feet by 7 feet, entering from the corridor. As- sume the street noise to be 80 decibels, the peak

noises caused by loud talking and laughter in

the room on one side to be 75 decibels, the peak

noise in the other room to be 60 decibels, and in

the corridor, 60 decibels. We shall neglect all sound coming through the floor or ceiling. The

total absorption by carpet, draperies, furniture,

etc., will be considered as 70 units. The absorption is computed as outlined in reference [4]. If the noise-reduction factor for each wall is computed as before, the following is obtained:

EXTERIOR WALL

Material Areas, s Transmission loss T rs

13-inch briclc wall, plus

plaster on one side,. . . Window ..

Total transmittance, T, equals75

15

Decibels

57280. 0000020

.0016

0. 00015

.0240

0. 0242

Noise-reduction factor (in decibels) = 10 logio (.4/ T)=10 logio(70/0.0242)=

34.6 decibels.

[9]
WALL BETWEEN ROOMS

Material Areas, s Transmission loss T T.S

4-inch clay tile wall, plus

plaster on both sides

Total transmittance, T, equals -

ft'

108

Decibels

44.0 0. 000040 0. 00432

0.0043

Noise-reduction factor (in decibels) =10 logio (70/0.0043) =42.1 decibels.

WALL BETWEEN ROOM AND CORRIDOR

Material Areas, s Transmission loss T rs

4-inch clay tile wall plus plasteronbothsides- . Door . Total transmittance. T, equals

ft' 69

21

Decibels 44.0

35.0

0. 000040

. 00032

0. 0028

.0067

0. 0095

Noise-reduction factor (in decibels) = 10 lof;io (70/0.0095) =38.7 decibels.

The noise in the room caused by street noise

only would be 80.0 —34.6=45.4 decibels.

That from the noisiest room would be 75 —42.1 =32.9 decibels. That from the quietest room,

60 —42.1 = 17.9 decibels, and that from the

corridor, 60-38.7 =21.3 decibels.

The approximate peak noise level can be

obtained as follows:

Anti logio (45.4/10) =34700

Anti logio (32.9/10)= 19.50 Anti logio (17.9/10)= 60 Anti logio (21.3/10)= 140

36850

10 logio 36850 = 45.7 decibels. In other words, the street noise, because of

the poor insulation of the window, is the pre- dominating noise, but it may not be the most

annoying one, as the intermittent noise result- ing from loud talking and laughing may be more disturbing than a steady noise. Furthermore, with a level of 32.9 decibels it should be

possible to understand a large portion of any

conversation carried on in the adjoining room. The values given for transmission losses are approximate for doors and windows, and are used merely to illustrate the fact that with a door or window in a wall it may be impractical

to attempt to make the rest of the wall a good

sound insulator, inasmuch as a small opening,

such as a crack imder a door, will greatly

reduce the soimd insulation. The same is

true of ducts or any other opening which may

connect two rooms. In equation 3 the total absorption comes in

the numerator, hence the noise level can be

reduced by increasing the total absorption in

the room. Generally, however, this reduction

is not large, being of the order of about 5

decibels as between a treated and an untreated room. This means that the introduction of

absorbent material to reduce the noise level caused by noises originating outside of the room

is of little value, since a much greater reduction can generally be obtained at less cost by

increasing the sound insulation of the boundaries of the room. This does not mean that

sound absorbent materials [4] are of no value,

for they are necessary to keep down the noise

level resulting from noises originating in the room. Absorbent material prevents corridors

from acting as speaking tubes and transmitting

sound from one room to another when the doors

are open. Other illustrations could be given

of the value of sound absorption, but the fact

should be emphasized that sound absorption

cannot take the place of sound insulation.

IX. MASKING EFFECT

There remains one other important question,

namely, what should be the transmission loss of a partition to give satisfactory results? It has often been stated that a certain type

of partition built in one place has been very sat- isfactory, yet the same type of partition used in

another place is not satisfactory. It is believed

that in these cases the conditions of local noise

are entirely different, hence the apparent fail- ure in one case. Wliether a partition is satis- factory or not depends on what is heard through

it. Wliat one hears through a partition depends upon the amount of general noise in the

locality as well as upon the noise level in the

adjacent room, and the transmission loss of the

partition.

For example, in the country or in a place

where the general noise level is very low it might be possible to hear almost everything

that occurs in an adjoining room, but if this same building were in a downtown district where the noise level is high, comparatively lit- tle would be heard from the adjoining room.

[10]
In other words, there is a masking effect be- cause of the presence of other noises and. this

should be taken into consideration. This

masking effect of noise is much the same as if the hstener were partially deaf, since his threshold of hearing is shifted slightly upwards.

In what is ordinarily considered a quiet room

this masking effect may raise the threshold of

hearing as much as 5 or 10 decibels, and in an

ordinary business office as much as 10 to 20

decibels. In a noisy shop or factory this maskmg effect is considerably greater.

Unfortunately, there have been very few

measurements made to determine the masking

effect of complex noises; hence, there is not

enough information available to determine

what the masking effect of a given noise level

will be.

X. MAXIMUM NOISE LEVELS WHICH

SHOULD BE TOLERATED

A more practical way to determine the type

of partition that should be used to secure defi- nite results is to determine the noise level one is willing to tolerate in a room. From a knowledge of this and the noise level existing on the

other side of the partition, the transmission loss through the partition required to reduce the

noise to the desired level can be computed from

the formulas given in section VIII.

The loudness of various noises has been

measured by different listeners, and the results

published [3, 6]. There is very little information regarding which noise levels should be tol- erated, but Knudsen [3] makes the following

recommendations:

Location

Studios for the recording of sound (talking- picture studios) Radio broadcasting studios Hospitals Music studios Apartments, hiotels, and homes.

Theaters, churches, auditoriums, class- rooms, and libraries Talking-picture theaters Private offices Public offices, banking rooms, etc

Maximum

noise level which

should be

tolerated

Decibels

6 to 8

8 to 10

8 to 12

10 to 15

10 to 20

12 to 24

15 to 25

20 to 30

25 to 40

Attention should be called to the fact that the

above levels are those desired but seldom found

in practice. Special attention is directed to the

low noise level reconanended for hospitals.

This low level is desirable; but, because of the

usual construction and location of hospitals,

the level is generally very much higher. The

transmission loss of numerous types of construction from which the reduction factors can be

computed may be found in Architectural

Acoustics [3], Acoustics and Architecture [5], and in the publications of the National Bureau

of Standards [1]. Many of the results obtained

at the National Bureau of Standards are given

in this report.

With this information it should be possible to design a floor or partition which will give satis- factory sound insulation for most conditions.

XI. PANEL CONSTRUCTION AND

TRANSMISSION LOSS, IN DECIBELS

Tables 1 and 2 give a summary of the results of sound-transmission measurements made at the National Bureau of Standards which, with

a few exceptions, have been published in pre- vious papers. In the earlier papers the term

"reduction factor" was used and the measure- ments made in a somewhat different manner

than in Research Paper RP800. In this paper

the results are given in the form of transmission

loss in decibels.

The frequency bands at which measurements

have been taken have been varied from time to time. The frequencies given in the following

table are approximately the middles of these

bands.

The panel numbers are those given in the

original publications.

The results for panels 25 and 26 were originally published in Scientific Paper of the National Bureau of Standards S552, for panels 60

to 128 in Research Paper RP48, and for panels

129 to 147, except 137A and 137B, in Research

Paper RP800. The results for panels 137A,

137B, and 148 to 169 have not been previously

published. In the table, two columns of aver- ages are given. The first column gives the

average transmission loss for frequencies 256

to 1,024 cycles. In the second column an

average is given only when measurements have

been made at nine frequencies. This column

then represents the average transmission loss between 128 and 4,096 cycles per second.

[11]
I

I

i 1

1 1 1

PANELS 162,163,119

Panel 162.—Wood studs; wood lath; scratch and brown coats of lime plaster; smooth, white finish. Panel 163.—Wood studs; wood lath; scratch and brown coats of gypsum plaster; smooth, white finish. Panel 119.

Same construction as panel 163.

PANELS 164 & 165

Panel 164.

Wood st uds; metal lath; scratch and brown coats of lime plaster; smooth, white finish. Panel 165.—Wood studs; metal lath; scratch and brown coats of gypsum plaster; smooth, white finish.

PANEL 86

Panel 86.— Wood studs; Y-z-inch Flaxlinum nailed to each side of 1- by 2-inch furring strips; wood lath, plastered on both

sides with scratch and brown coats of gyps um plaster; s mooth, white finish.

1 i i

PANEL 120 PANEL 123

Panel 120.—Wood studs; ji-inch Insulite applied to both sides; joints filled. Panel 123.—Wood studs; ^i-inch Insulite; scratch and brown coats of gypsum plaster; smooth, white finish.

PANEL 124 PANEL 126 PANEL 125

Panel 124.

Staggered wood studs;yo-inch Insulite applied toboth sides; joints filled. . ^ i. Panel 126 —Staggered wood studs; \i-inch Insulite; scratch and brown coats of gypsum plaster; smooth, white finish. Panel 125.

Staggered wood studs; ji-inch Insulite; Ecod fabric; scratch and brown coats of gypsum plaster; smooth,

white finish.

[12]
TaI!I,JO I -S()iiii.il-l,ranHni,issi()n loss uhM slniciiirc.s

Transmission loss (in decibels) at frequencies (cycles per scconfl)

Panel

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096

Average

256 to 1,024 128 to 4,096

Weight

WOOD STUDS

162.

163. 119.

27. 4

31. 6

164.,

165.

.

26. 4

31. 0

86.

120_

123.

124_

126. 125.

38. 2

28. 5

46. 2

34. 1 50. 1 52. 2

27. 3

29. 0

34. 2

26. 0

36. 3

18. 4

39. 6

40. 6

34. 5

42. 4

28. 6

39. 5

29. 9

52. 2

52. 6

38. 1 34. 4

39. 7

31. 5

41. 0

33. 2

39. 2

43. 7

38. 2

38. 2

24. 0

47. 2

27. 9

49. 4

47. 4

43. 5

39. 9

48. 7

43. 6

50. 2

36. 8

43. 9

52. 3

42. 6

44. 7

35. 6

57. 0

41. 8

59. 6

53. 7

54. 9

40. 1 49. 0

56. 1 44. 7

54. 1

47. 5

56. 3

59. 3

60. 1 58. 2

58. 8

61. 7

50. 7

55. 2

60. 1 53. 8

62. 7

59. 9

58. 2

58. 1 61. 1

41. 8

32. 5

40. 9

45. 0

38. 1

41. 8

29. 4

47. 9

33. 2

53. 7

51. 2

42. 1 35. 7

44. 4

39. 2

ibljr1.5. 6

15. 1 17. 4

19. 8

20. 0

14. 7

5. 1 13. 3

4. 94

13. 1 16. 1

13
PANEL 127

Panel 127.—Wood studs; }i-inch Insulite applied to one side, plastered and back plastered; metal lath applied to opposite

side and plastered with scratch, brown, and finish coats. 1 1 i f

PANELS 148 & 149

Panel 148.—Wood studs; gypsum lath nailed to studs with nails approximately 6 inches apart; scratch and brown coats of sanded gypsum plaster; smooth, white finish; thickness of plaster yi- inch. Panel 149.

Wood stiids; gypsum lath held on with special nails with large heads, the nails being driven between the sheets of gypsum lath; scratch and brown coats of sanded gypsum piaster; smooth, white finish; thickness of plaster

Yi inch.

PANEL 153 Panels 151.152 PANEL 150,167

Panel 153.—Wood studs; gypsurn lath attached to studs with stiff clips; scratch and brown coats of gypsum plaster; smooth, white finish; thickness of plaster Ys inch Panel 151.

Same as panel 153, except that Yi-inchfelt was glued to back of gypsum lath. Panel 152.

Same as panel 151, except that plaster was inch thick instead of ji inch. Panel 150.—Wood studs; gypsum ath attached to studs by spring clips; scratch and brown coats of gypsum plaster; smooth, white finish; thickness of plaster inch. Panel 167.

Same as panel 150, except spring clips were made by different firm. Panel 168.

Same as panel 167, except that the space between the studs was filled with glass wool and packed to a density

PANEL I43A PANEL I43B

Panel MSA.—Constructed of lYz-inch Steeltex channels for studs; Steeltex lath; scratch and brown coats of gypsum

plaster; smooth, white finish. Panel 143B.

Same as panel l/fSA, except that the space between the studs was packed with rock wool.

PANEL 1 66

A

PANEL I66B

Panel 166A.

Constructed of 3-inch one-piece metal studs spaced 16 inches on center; expanded metal lath; scratch and

brown coats of gypsum plaster; smooth, white finish. Panel 166B.

Same as panel 166A, except that the space between the studs was filled with rock-wool bats and packed

to a density of 4-3 IblfP.

[14]
Table 1.

Sound-transmission loss—wall slru.clures—CoiitiiuKul

Panel

Transmission loss (in decibels) at frequencies (cycles i)er second]

Average

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096 256 to 1,024 128 to 4,096

Weight

WOOD STUDS—Continued

127

148 32. 6

149 32. 5

153 30. 9

151 29. 6 152 37. 4

150 51. 0

167 45. 1

168 47. 5

45. 4

27. 8

41. 0

37. 2

37. 6

40. 4

42. 3

52. 9

50. 1

45. 1

31. 0

38. 9

40. 5

39. 9

42. 4

48. 1

45. 0

49. 1

34. 9

43. 2

41. 7

44. 9

45. 3

48. 4

48. 1

53. 2

44. 7

39. 2

45. 7

46. 2

47. 1 46. 5

50. 0

47. 4

53. 2

44. 3

50. 6

51. 3

56. 6

55. 4

56. 3

53. 0

55. 9

47. 6

45. 6

50. 4

60. 8

60. 6

56. 4

55. 4

58. 0

57. 7

48. 7

55. 1

53. 8

60. 3

61. 8

47. 6

53. 1

57. 6

59. 0

65. 9

71. 6

45. 8

39. 0

45. 8

67. 2 46. 2 46. 7

70. 2 49. 9 49. 7

68. 2 50. 0 50. 9

65. 8 51. 8 51. 8

66. 7 49. 8 51. 9

68. 2 53. 9 54. 8

41. 1

47. 7

STEEL STUDS

17. 7

25. 7

29. 9

34. 3

27. 4

34. 9

20. 6

24. 0

28. 4

30. 9

35. 3

33. 5

27. 2

36. 8

34. 8

40. 1

40. 1

38. 0

42. 7

46. 7

40. 0

39. 4

39. 2

49. 8

42. 6

39. 6

57. 8

69. 1

53. 4

51. 7

30. 2

35. 8

35. 7

36. 4

36. 9

38. 0

127200'—39- 15
A B

Panel 159.Panel A only—Metal studs of Yi-inch channel iron expanded metal lath; scratch and brown coats of gypsum plaster; smooth, white finish, applied to only one side. Panel 160A.—Two panels similar to panel 159 plowed hack to hack and. resting on cork 1-inch

thick; distance from face to face of panels 10 inches. Panel 160B.

Same as panel 160A, except distance from face to face 8}^ inches. Panel 160C.

Same as panel 160A, except distance from face to face 7 inches. Panel 160D.

Saine as panel 160A, except distance from face to face BVi inches. Panel 160E.

Same as panel 160A, except distance from face to face inches. Panel 160F.

Same as panel 160A, except distance from face to face JfVi inches, and braces at corners are in contact with each other. Panel 160G.

Same as panel 160E, except cork was removed and a 1-inch hoard was placed under the panels to carry the load. Panel 160H.

Same as panel 160G, except board was removed and concrete substituted for the hoard. Panel 1601.

Same as panel 160H, except the two panels ivere tied together at two points with a

shoe made of ji-inch channel iron, each point being approximately 18 inches in the horizontal

direction from the center of the panel.

PANELS 159,

I60A-I60I

PANEL 161

Panel 161.

3- by 12- by 30-inch gypsum tile; hroion coat of gypsum plaster; smooth, white finish.

Panel I38

Panel 138.

3- by 12- by 30-inch gypsum tile; United States Gypsum resilient clip; metal lath and gypsum plaster on one side; gypsum plaster applied directly to tile on the other side; smooth, white finish on both sides.

[16]
Table 1.

Sound-transmission loss—wall struclures—Continued

Transmission loss (in decibels) at frequencies (cycles per second)

Panel Average

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096 256 to 1,024 128 to 4,096

Weight

STEEL STUDS—Continued

159 26. 8 160A 50. 0 160B 48. 7 160C 51. 0 160D 43. 4 160E 43. 1 160F 44. 1 160G 44. 5 160H 46. 4

1601 43. 0

30. 8

49. 9

51. 0

49. 0

49. 3

50. 5

48. 7

52. 7

45. 5

39. 9

28. 8

47. 8

46. 1 44. 4

45. 3

43. 1 42. 9

44. 0

44. 0

41. 4

33. 3

52. 4

51. 8

51. 1 49. 6

48. 3

45. 6

46. 2

43. 2

42. 7

34. 7

53. 4

53. 2

52. 9

51. 6

50. 6

47. 0

45. G

47. 8

46. 3

36. 1

56. 8

56. 7

55. 7

55. 8

54. 8

52. 0

53. 7

51. 0

48. 3

32. 8

54. 6

54. 4

54. 5

51. 0

50. 2

49. 4

49. 7

46. 2

45. 7

32. 2

60. 0

58. 4

55. 6

61. 1 61. 6

57. 1

55. 9

49. 2

45. 9

43. 8

71. 8

71. 8

72. 5

72. 7

73. 6

71. 9

69. 5

59. 6

58. 2

33. 1

53. 0

52. 4

51. 7

50. 7

49. 4

47. 4

47. 8

46. 4

44. 9

33, 3

55. 2

54. 7

54. 1 53. 3

52. 9

51. 0

51. 3

48. 1

45. 7

IhlJt^

8. 1

17. 2

17. 2

17. 2

17. 2

17. 2

17. 2

17. 2

17. 2

17. 2

GYPSUM TILE

161 28. 9 30. 9 35. 7 38. 5 36. 2 37. 0 41. 5 46. 8 47. 2 37. 8 38. 1 21. 0

138 45. 4 44. 4 54. 7 59. 1 6L 9 80. 0 52. 7

[17J
Panel 60

Panel 60.

Holloio clay tile panel (two units, Sji by 12 by 12 inches and 8 by 12 by 12 inches); end construction;

-plastered on both sides with brown coat of gypsum plaster; smooth, white finish.

PANEL

Panel 61.

Hollow clay tile panel (two units, Sji by 5 by 12 inches and 8 by 5 by 12 inches) ; side construction; plastered

both sides with brown coat of gypsum plaster; smooth white finish.

PANEL 62 PANELS 64&65

Panel 62.

Hollow clay tile panel constructed of 8- by 12- by 12-inch tile, six cells; plastered on both sides with brown

coat of gypsum plaster; smooth, white finish. Panel 63.

Hollow clay tile panel constructed of 6- by 12- by 12- inch load-bearing partition, tile, si.c cells; plastered on

both sides with broum coat of gypsum plaster; smooth, white finish. 1'anel 64.

Hollow clay tile patud constructed of 6- by 12- by 12-inch partition, tile, medium bunted, three cells; plastered both sides with brown coat of gypsum plaster; smooth, white finish. Panel 65.

Hollow clay tile panel constructed of 6- by 12- by 12-inch soft partitiuti. tile, three cells; plastered on, both

sides with brown coat of gypsum plaster; smooth, white finish.

PANELS 66,140,141, 142/ PANELS 68 & 69

Panel 66.

Hollow clay tile panel constructed of 4- by 12- by 12-inch partition tile, three cells; plastered on both sides with brown coat of gypsum plaster; smooth, white finish. Panel 140.

Hollow clay tile panel constructed of standard 4- by 12- by 12-inch New Jersey porous clay tile; plastered on both sides with % inch of brown coat gypsum plaster; smooth, white finish. Panel 141.

HoUoiv clay tile panel constructed of 4- by 12- by 12-inch Nevj Jersey hollow clay tile with 1-inch shells; plastered on both sides with Ys inch of brown coat gypsum plaster; smooth, white finish coat. Panel 142.

Hollow clay tile panel constructed of 4- by 12- by 12-inch New Jersey standard clay partition tile; plastered on both sides with Ys inch of brown coat gypsum plaster; smooth, white finish coat. P.anel 68.

Hollou) clay tile panel constructed of 3- by 12- by 12-inch partition tile, three cells; plastered both sides with brown coat of gypsum plaster; smooth, white finish. Panel 69.

Built as nearly like panel 68 as possible.

[18]
Table \ .- -SniDul-irannmigKioti, less ukiU, .slriicliirrs ('diil iiiiicil

Traiisiiiissicn loss (in decibels) at fixHiiioiicies (cycles pel' second)

Panel Average Weight

128 165 192 256 381 512 768 1 ,021 2,018 3,100 4,096 256 to 1,024 128 to 4,096

CLAY TIL]']

37. 0 55. 2 53. 6

48. 7 53. 3 52. 2

48. 9 58. 0 53. 2

46. 6 53. 5 54. 7

45. 1 52. 1 52. 7

43. 7 50. 1 45. 9

41. 5 49. 9 47. 3

46. 6 50. 2

51. 5 55. 7

46. 2 49. 4

43. 3 51. 0 51. 2

43. 7 49. 8 50. 3

60.

61.

62

63

64

65

66..

140_

141_

142.

68_.

31. 2

30. 0

33. 3

49. 4

49. 4

44. 3

38. 8

41. 2

41. 1

41. 1

31. 0

35. 4

32. 8

40. 7

41. 7

40. 1

40. 3

44. 5

42. 1

37. 4

42. 0

40. 0

35. 9

43. 5

42. 1

35. 9

41. 4

57. 7

65. 1

61. 8

42. 2

48. 1

45. 9

42. 5

41. 2

42. 3

40. 9

37. 8

43. 5

40. 4

40. 0

42. 3

[19]
1 n

iLJ.

!7*- ,« PANEL 71 PANEL 72 ^ PANELS 73 & 74

Panel 71.

Hollow clay tile panel constructed of 4- by 12- by 12-inch partition tile, three cells; wood /wring strips; paper; metal lath; scratch and brown coat of gypsum plaster; smooth, white finish. Panel 72.

Hollow clay tile panel constructed of 4- by 12- by 12-inch partition tile; three cells; pads; wood furring

strips; paper; metal lath; scratch and brown coats of gypsum plaster; smooth, white finish. Panel 73.

Hollow clay tile panel constructed of 4- by 12- by 12-inch partition tile; three cells; wood furring strips; Masonite; broxvn coat gypsum plaster; smooth, white finish. Panel 74.

Hollow clay tile panel constructed of 4- by 12- by 12-inch partition tile; three cells; wood furring strips; Insulite; brown coat of gypsum plaster; smooth, white finish.

PANEL 75

Panel 75.

Double partition 3- by 12- by 12-inch hollow clay tile spaced Iji inches between sides; Flaxlinum, 1 inch

thick and butted tight, was placed in the space between the tile; one side of the partition was carried on %-inch Flax- linum strips, which were 4 inches wide, the strips being placed at the sides and top as well as the bottom.

PANEL 139 & 144 / PANEL 145

Panel 139.

Cinder-block panel constructed of 4- by 8- by 18-inch standard Straub hollow cinder blocks; plastered on

both sides with % inch of brown-coat gypsum plaster; srnooth, white finish. Panel 144.

Cinder-block wall panel constructed of 4- by 8- by 16-inch cinder blocks; plastered on both sides with Ys inch

of brown-coat gypsum plaster; smooth, white finish. Panel 145 - —Cinder-block wall panel constructed of 3- by 8- by 16-inch cinder blocks; plastered on both sides with -/s inch

of brown-coat gypsuin plaster; s?nooth, white finish.

PANELS 25 & 26

Panel 25.

Four-inch brick panel; plastered on both sides with brown coat of lime plaster; smooth, white finish. Panel 26.

Four-inch brick panel; plastered on both sides with brown coat of gypsum plaster; smooth, white finish.

[20]
Iablk ].

Sim iiil-lnirisiii issiiDi, Iiisx -inid.i si riirl iircs ( 'ontiiiiUMl

Trausmission loss (in decibels) at frequencies (cycles jjcr second)

Panel Average

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096 256 to 1,024

1 28 to 4,096

Weiglit

CLAY TILE—Continued

71.

72.

73 _

74.

75.

55. 6

55. 7

55. 3

52. 2

55. 2

52. 8

52. 4

53. 2 5L 9

50. 8

57. 3

53. 3

56. 8

60. 9

50.

57. 6

60. 2

68. 8

61. 1

65. 8

64. 0

69. 7

69. 6

61. 6

73. 2

55. 2

53. 8

55. 1

55. 0

52. 3

34. 0

34. 0

28. 0

34. 0

50. 0

CINDER BLOCK

139_

144.

145.

29. 8

35. 5

33. 8

36. 6

36. 4

30. 2

36. 9

36. 5

41. 2

40. 5

37. 7

44. 4

41. 9

46. 7

44. 7

47. 9

50. 9

51. 2

52. 7

55. 4

56. 9

59. 1

62. 4

64. 3

38. 6

44. 0

43. 0

45. 6

45. 1

29. 7

35. 8

32. 2

25 43. 1 46. 7 54. 5 56. 4 44. 9 26 46. 4 48. 8 58. 4 6L 3 47. 6

[21]
PANELS 79^80,81

Panel 79.

Eight-inch brick panel, New Hampshire brick, poor workmanship; plastered on both sides with brown coat of gypsu m plaster; smooth, white finish. Panel 80.

Eight-inch brick panel, New Hampshire brick, good workmanship; plastered on both sides with brown coat of gypsum plaster; smooth, white finish. Panel 81.

Eight-inch brick panel, Mississippi brick, good workmanship; plaUered on both sides with brown coat of gypsum plaster; smooth, white finish.

PANELS 82,83,84 ^ PANEL 85

New Hampshire brick laid on edge; furring strips wired; gypsum plaster board; plastered both sides with

scratch and brown coats of gypsu m plaster; smooth, wh ite finish. New Hampshire brick laid on edge; furring strips nailed; gypsum plaster board; scratch and brown coats of gypsum plaster; smooth, white finish. New Hampshire brick laid on edge; furring strips nailed; Yi-inch Insulite; scratch and brown coats of gypsum

plaster; smooth, white finish. New Hampshire brick laid on edge; brown coat of gypsum plaster; smooth, white finish.

Panel 146.—Wall panel constructed of Thermax sheets 3 inches thick laid in mortar composed of gypsum plaster; plastered both sides with a brown coat of gypsum plaster; smooth, white finish. Panel 147A.—Wall panel constructed of Thermax sheets 3 inches thick laid in mortar composed of gypsum plaster; when the gypsum had set, 1-inch Thermax sheets were nailed on one face; plastered both sides with a brown coat of gypsum plaster; smooth, white finish. Panel 147B.—Wall panel; this panel was constructed the same as 147A, except that sisal-kraft paper was placed between the 1-inch and 3-inch Thermax, thus preventing any mortar penetrating through the joints of the 1-inch Ther- max, and bonding it to the S-inch Thermax.

PANEL 154

Panel 154.

Two-inch solid plaster partition; j^-inch channel studs; Ecod ?netal lath with paper backing applied to one side; gypsum plaster; sand finish.

Panel 155.

Partition of 3yi- by I^A- by 8-inch glass bricks manufactured by Owens Illinois Glass Co.

Panel 93.Single sheet of aluminum 0.025 inch thick. Panel 94.

Single sheet of galvanized iron 0.03 inch thick. Panel 95.

Single sheet three-ply plywood Vs inch thick. Panel 96.

Single sheet three-ply plyivood }i inch thick. Panel 98.

Single sheet Insulite }i inch thick. Panel 101.

Single sheet of heavy wrapping paper. Panel 102.

Single sheet of double-strength glass }i inch thick. Panel 103.

Single sheet of plate glass }i inch thick. Panel 106.

Single sheet of standard Celotex jia inch thick. Panel 110.

Single sheet of lead Vs inch thick. Panel 111.

Single sheet of lead Me inch thick.

[22]
Table 1.

Sound-transmission loss—wall sli-uciures—ContiniaKl

Transmission loss (in decibels) at frequencies (cj'cles per second)

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096

Average

256 to

1 ,024 128 to 4,096

BRICK—Continued

47. 7

47. 7

50. 2

52. 1

46. 8

48. 8

40. 0

48. 1

49. 4

47. 6

47. 4

44. 3

50. 5

36. 9

55. 6

57. 0

56. 5

54. 4

59. 8

48. 7

56. 3

59. 2

63. 5

53. 9

61. 3

55. 8

59. 1

60. 4

70. 0

69. 2

57. 8

69. 2

58. 2

59. 1

50. 5

51. 4

51. 1

52. 0

48. 5

53. 0

41. 9

THERMAX

25. 8

33. 4

32. 1

32. 0

33. 1

40. 1

32. 0

35. 9

40. 5

32. 2

36. 0

43. 9

33. 3

37. 6

46. 3

35. 3

43. 7

50. 2

32. 4

45. 2

51. 2

37. 5

47. 1

52. 1

52. 9

62. 9

70. 5

33. 0

39. 7

46. 4

34. 8

41. 7

47. 4

SOLID PLASTER PARTITION

154 38. 0 37. 2 33. 6 33. 4 36. 2 35. 8 41. 0 48. 1 55. 5 36. 0 1 39. 9 GLASS BRICK

155 30. 2 36. 2 34. 7 39. 4 40. 5 45. 1 48. 6 49. 0 1 43. 4 41.7 40. 8 SINGLE LAYERS OF MATERIAL

93 17. 9

25. 3

19. 0

21. 0

22. 2

1. 4

26. 2

32. 6

22. 4

31. 0

31. 8

94

959698

101 102

103_ 106

110

111

13. 2 17. 7 23. 2 25. 3

20. 5 28. 8 35. 0 31. 7

17. 5 22. 0 26. 7 25. 5

20. 7 25. 5 26. 0 21. 9

20. 2 24. 1 20. 9 27. 1

1. 5 1. 7 3. 3 3. 7

27. 4 30. 8 33. 0 29. 2

30. 9 33. 5 34. 2 32. 2

17. 3 23. 4 27. 4 24. 6

27. 2- 37. 5 43. 8 32. 6

33. 2 32. 0 32. 1 32. 5

16. 3

24. 9

19. 5

22. 4

22. 2

1. 5

28. 1 32. 3

21. 0

31. 9

32. 3

0. 35

1. 2

0. 52

. 73

. 75

. 016

1. 6

3. 5

0. 66

8. 2

3. 9

[23]
Panel 78a Panel 78 b

Panel 78A.

Combination floor panel constructed of 6- by 12- by 13-inch three-cell partition tile; the ceiling of this panel was finished with a brown coat of gypsum plaster; smooth, white finish. Panel 78B.

Same as panel 78A, except 2 inches of cinder concrete and 1 inch of cernent were added to upper surface.

PANEL II 7A PANEL II7B

Panel 117A.

Combination floor panel constructed of 4- by 12- by 12-inch three-cell partition tile; ceiling was finished with furring strips, }i-inch Insulite, and plaster. Panel 117B.

Same as panel 117A, except floating floor was added, which consisted of 1- by 2-inch nailing strips, rough flooring, and y%-inch oak flooring.

PANEL II7C PANEL 118

Panel 117C.

Same as panel 117B, except V>-inch Insulite was added between masonry slab and floating floor. Panel 118.

Same as panel 117C, except ceiling was stripped off and suspended ceiling attached by means of wires.

Panel I29a panel I29b Panel I29c

Panel 129A.

Combinatiori floor panel constructed of 4- by 12- by 12-inch, 3-cell partition tile; the ceiling of this panel was flnished with % inch of brown coat gypsuin plaster and a smooth, white finish coat; the floor surface consisted

of ^Yie-inch oak flooring, nailed to 2- by 2-inch nailing strips 16 inches on centers, which were grouted into the

concrete. Panel 129B.

Same as panel 129A, except that United States Gypsum resilient steel clips were inserted between the concrete and nailing strips. Panel 129C.

Same as panel 129B, except that the oak flooring was removed, and Yi-inch gypsum plasterboard was

attached to the nailing strips and PA-inch Hydrocal was applied on top of the plasterboard.

[24]
Table 2.

Sound-transmission loss—Jlnor slrudures

Transmission loss (in decibels) at frequencies (cycles per secoiidj

Panel number

Average

Tapping 128 165 192 256 384 512 768 1,024 2,048 3,100 4,096

256 to 1,024 128 to 4,096

Wciglit

COMBINATION

78A.

78B117A.

117B.

117C.

118-

129A._.

129B._.

129C--.

56. 5

62. 7

63. 6

68. 0

35. 9

37. 0

42. 6

51. 2

52. 4

56. 6

63. 1

70. 3

67. 9

37. 7

46. 6

49. 5

46. 8

48. 0

55. 8

61. 0

63. 4

65. 8

38. 6

58. 3

60. 9

49. 6

49. 9

57. 7

65. 9

63. 5

72,

46. 8

68. 5

71. 3

60. 4

54. 6

58. 8

73. 7

68. <76. 0

53. 8

73. 2

76. 7

54. 0

48. I

57. 2

67. 4

68. 0 <77. 0

49. 2

50. 1

56. 7

63. 3

65. 7

68. 6

55. 1 41. 0

(^)

57. 8

60. 6

5. 1

34. 0

35. 0

51. 0

22. 6

33. 0

38. 5

83

109

69. 8

73. 5

74. 2

72. 8

» Sound inaudible. [25]
Panel 76 ' Panel 77

Panei. 76.Flat arch floor panel constructed of 8-inch, 4-cell tile: plastered with brown coat gypsum plaster and smooth,

white finish; two by fours were fastened to the top surface approximately 16 inches on center and the space betv)een

filled with cinder concrete; floor was finished with hardwood flooring.

Panel 77.

Same as panel 76, except the floor was finished ivith 2 inches of cinder concrete and 1 inch of cement.

Panel 116A.

Reinforced concrete flat slab type of floor construction; Ins ulite furred out and applied as ceiling; brown

coat gypsum plaster; smooth, white finish. Panel 116B.

Same as panel 116A, except floating floor was added, which consisted of 1- by 2-inch nailing strips, rough flooring, and Ys-inch oak flooring.

Panel 116C.

Same as panel 116B, except y>-inch Insulite was added between concrete slab and floating floor.

k \^ - •.,

e

1 # -I —7-r-/— -r

PANELS 156 & 158 / PANEL 157

Panel 156.

Floor panel composed of a 4-inch concrete slab; suspended ceiling of gypsum lath; Yi-inch brown coat gypsum

plaster; finished, with ^i-inch acoustic plaster; S-inch ground cork on top of gypsum lath; hangers were special coiled springs.

Panel 158.

Same as panel 156, except 4 inches of rock wool was used in place of the ground cork. Panel 157.

Same as panel 166, except a flat spring was used in place of the coiled spring in the hanger and Thermofil was used in place of cork.

PANEL II4A PANEL II4B

Panel ll-tA.

Floor panel; wood joists; plaster on wood lath applied to lower side, subflooring and Yn-inch finish flooring to upper side. Panel 114B.

Sa7ne as panel II4A, with exception of flooring; ]A-inch Insulite between rough and finished floors.

26
Table 2.

Soiind-iransiniaaion l:).^— jluor stniciiire:i —Coiiliiiucil

Transmission loss (in decibels) at frequencies (cycles per second;

Panel number

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096

Average

Tapping Weight

256 to 1,024 128 to 4,096

FLAT AECH

76 46. 3

46. 7

46. 8

47. 1

47. 8

47. 4

54. 5

50. 5

54. 4

49. 1

47. 0

47. 1

Ml'

76

77 85

CONCRETE SLAB

116A_-- _. 50. 9

58. 9

57. 9

54. 8

57. 0

58. 2

43. 8

47. 1 46. 6

47. 9

49. 6

50. 1

58. 7

55. 4

55. 8

50. 8

51. 4

51. 0

56. 1

57. 0

55. 7

56. 5

67. 6

66. 3

60. 0

60. 0

59. 6

53. 2

65. 2

67. 3

67. 5

69. 0

67. 8

56. 0

62. 5

62. 3

56. 7

60. 0

60. 1

5L 7

53. 0

52. 6

1. 2

30. 0

33. 0

IL 3

11. 5

12. 3

54. 4

58. 1

58. 9

116B

116C

156

158

157

39. 3

36. 7

40. 8

46. 5

45. 5

43. 6

76. 7

76. 9

76. 5

54. 3

54. 8

54. 6

WOOD JOIST

114A

U4B

47. 9

47. 7

40. 8

48. 3

40. 7

40. 6

50. 1

50. 3

48. 8

48. 9

47. 4

46. 6

45. 9

46. 4

14. 0

14. 0

[27]
PANEL II4C ' PANEL II4D

Panel 114C.

Same as panel IHA, with exception of flooring; rough flooring; }i-inch Ins ulite; floating floor, consisting

of nailing strips, rough and flnish flooring.

Panel Il-ID.

Same as panel II4C, except Insulite was inserted between rough and finished floor in floating floor.

applied as flooring; ends of ceiling and floor joists were nailed to a common support. Panel 115B.

Same as panel 115A with exception of flooring; rough flooring; Yi-inch Insulite; floating floor consisting

of 1- by 2-inch nailing strips, rough flooring, and ji-inch oak flooring.

PANEL 130

Panel 130.

Floor panel, 2- by 8-inch V)ood joist; plaster on metal lath applied to lower side, subflooring and '^Ym-inch oak flooring to upper side.

PANELS I32AJ32C PANEL I33A PANEL I33B

Panel 132A.

Floor panel, 2- by 8-inch wood joist; plaster on metal lath applied to lower side, subflooring to upper side; 1-inch Balsam Wool was laid over the stibfloor and on this were placed small squares {2}^ by 2}-! inches) of hardpressed Nuwood spaced 16 inches on centers in each direction; nailing strips lYj by l^i inches were placed on top of

these Nuwood squares and held in place by a metal strap; the finish floor C^Yio-inch oak) was nailed on top of these nailing strips. Panel 132B.—This was a floor in an apartment house and supposed to be constructed the same as panel 132A. Panel 132C.—This panel was the same as panel 132A, except that Yi-inch Balsam Wool was used nistead of 1-inch. Panel 133A.

Floor panel, 2- by 8-inch wood joist; plaster on metal lath applied to lower side, subflooring to upper

side; Y2-inch balsam wool was laid over suhfloor and y^-inch Nuwood was placed on top of the balsam wool; IY4- by lYi-inch nailing strips were spaced 16 inches on centers on top of the Nuwood and held in position by driving one

nail at each end through the strip and into the subfloor; a flnish floor of ^Ym-inch oak was applied on top of the nailing strips. Panel 133B.

Floor panel; this panel was the same as panel 133A, except that the sheets of Nuwood were removed and

strips of Nuwood 2Yi inches wide were placed under the nailing strips.

[28]
Table 2.

Soinid-lransini.ssiorL Zoss

Jlour slruclurcs—Coiiliiiucd

Transmission loss (in decibels) at frequencies (cycles per second)

Average

Tapping 128 165 192 256 384 512 768 1 ,024 2,048 .3,100 4 ,096 Weight 256 to 1,024 128 to 4,096

WOOD .JOIST—Continued

23. 2

31. 8

26. 4

25. 5

23. 6

23. 1

57. 6

57. 9

52. 6

62. 4

57. 5

60. 1

53. 6

65. 3

23. 5

35. 4

31. 1 35. 9

33. 5

34. 8

54. 8

53. 5

49. 2

57. 3

33. 9

48. 7

50. 4

48. 1 47. 5

51. 2

62. 4

62. 7

54. 9

68. 8

40. 6

56. 6

61. 7

56. 1 55. 8

60. 3

57. 6

55. 7

5.5. 3

62. 3

47. 6

67. 5

64. 0

70. 1 67. 1

72. 8

56. 6

56. 7

5.5. 0

65. 0

59. 7

80. 0

80. 0

80. 0

81. 8

80. 0

58. 2

58. 8

52. 6

63. 8

32. 7

46. 9

47. 7

46. 7

45. 6

48. 8

22. 0

22. 0

22. 0

30. 0

11. 1

19. 4

17. 1 15. 3

20. 2

[29]
Panel 137.

Floor -panel constructed of 8-inch Mac Mar joist, with 3-inch Thermax clipped on top and 1-inch Thermax

clipped on bottom of joist; J4 inch of concrete was poured on top of the 3-inch Thermax; floor was finished by cementing

Yi-inch battleship linoleum on top of the concrete; ceiling was finished by applying a brown coat of gypsum plaster

and a smooth, white finish coat. Panel 137A.

Same as panel 137, except 3-inch Thermax was removed and standard high rib metal lath attached to top of joist; 2\'i inches of concrete was poured on top of lath; battleship linoleum was cemented to top of concrete. Panel 137B.

Sa^ne as panel 137A except ceiling of panel 137A was removed and standard high rib metal lath was

attached to under side of joist; scratch and brorvn coat gi/psum plaster; smooth, white finish.

Panel 136A.Floor panel constructed by using steel floor section with flat top; top of this section was covered with 2

inches of concrete and a suspended metal lath and plaster ceiling attached to the bottom, leaving approximately 4

inches between the metal section and plaster. Panel 136B.

Floor panel; same as panel 136A, except that the 2-inch concrete slab was retnoved and ji-inch of emulsified asphalt applied directly to the top of the steel section; a 2-inch concrete slab was cast on top of this asphalt.

[30]
Table 2.

Soiind-lransmission lo.ts—floor- sln/diirefi—Coiiiimicil

Transmission loss (in decibuls) at frequencii's (cycles j;ei' sccoiidj

Panel number

Average

Tapping

128 165 192 256 384 512 768 1,024 2,048 3,100 4,096 25G to

1 ,024 128 to 4,090

Weight

STKEL JOIST

137-

137A.

137B.

30. 6

36. 8

40. 3

51. 0

45. 7

41. 1

43. 7 40. 1

46. 6 47. 6

48. 4 50. 7

51. 9

52. 0

53. 6

55. 2

55. 8

58. 8

58. 2

59. 3

06. 0

64. 5

65. 2

63. 4

74. 2

74. 7

71. 8

51. 0

52. 3

55. 5

52. 8

53. 7

54. 9

11. 7

13. 6

13. 1

STEEL SECTION

136A.

130B_

34. 0

41. S

43. 9

48. 9

43. 2

52. 4

50. 8

56. 3

51. 7

60. 0

57. 0

64. 2

59. 2

66. 7

64. 6

77. 3

71. 9

83. 0

52. 4

59. 9

52. 9

61. 2

6. 5

21. 1

XII. SELECTED REFERENCES

[l] E. E. Eckhardt and V. L. Chrisler, Transmission

and absorption of sound by some building materials. BS Sci. Pap. 31, 37 (1926) S526. V. L. Chrisler, Transmission of sound through

building materials, BS Sci. Pap. 22, 227 (1927-28) S552. V. L. Chrisler and W. F. Snyder, Transmission of sound through wall and floor structures, BS J. Research 2, 541 (1929) RP48.

V. L. Chrisler and W. F. Snyder, Recent soundtransmission measurements at the National Bureau

of Standards, J. Research NBS 14, 749 (1935)

RP800.

[2] S. E. Slocum, Noise and Vibration Engineering, D. Van Nostrand Co., Inc. (1931). Hope Bagenal and Alex. Wood, Planning for Good

Acoustics, E. P. Button & Co., Inc. (1931). Arthur L. Kimball, Vibration Prevention in Engineering. John Wiley & Sons, Inc. (1932).

[3] V. O. Knudsen, Architectural acoustics, John Wiley

& Sons (1932).

[4] Paul R. He.yl and V. L. Chrisler, Architectural

Acoustics. " Cir. NBS (1938) C418.

[5] Paul Sabine, Acoustics and Architecture. McGraw-Hill Book Co., Inc. (1932).

[6] New York City Noise Abatement Commission,

City Noise (1930). Washington, November 8, 1938.

O

[31]

The National Bureau of Standards was established by act of Congress, approved

March 3, 1901, continuing the duties of the old OflSice of Standard Weights and Measures

of the United States Coast and Geodetic Survey. In addition, new scientific functions were assigned to the new Bureau, Originally under the Treasury Department, the

Bureau was transferred in 1903 to the Department of Commerce and Labor (now the

United States Department of Commerce). It is charged with the development, construction, custody, and maintenance of reference and working standards, and their

intercomparison, improvement, and application in science, engineering, industry, and

commerce. SUBJECTS OF BUREAU ACTIVITIES

Electricity

Resistance Measurements

Inductance and Capacitance

Electrical Instruments Magnetic Measurements

Photometry

Radio

Underground Corrosion

Electrochemistry

Telephone Standards

Weights and Measures Length

Mass

Time

Capacity and Density

Gas Measuring Instruments Thermal Expansivity, Dental

Research, and Identification Weights and Measures Laws

and Administration

Large-Capacity Scale Testing

Limit Gages

Heat and Power Thermometry

Pyrometry

Heat Measurements Heat Transfer Cryogenics

Fire Resistance

Automotive Power Plants Lubrication and Liquid Fuels Aviation Engines and Accessories Optics

Spectroscopy

Polarimetry

Colorimetry and Spectrophotometry

Optical Instruments Radiometry

Atomic Physics, Radium, and

X-Rays

Photographic Technology

Interferometry

Chemistry

Paints, Varnishes, and Bitu- minous Materials Detergents, Cements, Corrosion, Etc.

Chemistry—Continued.

Organic Chemistry

Metal and Ore Analysis, and

Standard Samples

Reagents and Platinum Metals

Electrochemistry (Plating)

Gas Chemistry

Physical Chemistry

Thermochemistry and Constitution of Petroleum

Mechanics and Sound

Engineering Instruments and

Mechanical Appliances

Sound

Aeronautic Instruments Aerodynamics

Engineering Mechanics

Hydraulics

Organic and Fibrous Materials Rubber

Textiles Paper

Leather

Testing and Specifications

Fiber Structure Organic Plastics

Metallurgy

Optical Metallurgy

Thermal Metallurgy

Mechanical Metallurgy

Chemical Metallurgy

Experimental Foundry

Clay and Silicate Products Whiteware

Glass

Refractories Enameled Metals

Heavy Clay Products

Cement and Concreting Materials Masonry Construction

Lime and Gypsum

Stone

Simplified Practice Wood, Textiles, and Paper

Metal Products and Construction Materials

Simplified Practice—Continued.

Containers and Miscellaneous

Products

Materials Handling Equipment and Ceramics

Trade Standards Wood, Wood Products, Paper,

Leather, and Rubber

Metal Products

Textiles Apparel

Petroleum, Chemical, and Miscellaneous Products

Codes and Specifications

Safety Codes

Building Codes

Building Practice and Specifi- cations Producer Contacts and Certification Consumer Contacts and Labeling

Office Finance

Personnel Purchase and Stores Property and Transportation

Mail and Files Library

Information

Editorial

Shops

Design and Drafting Instrument Woodworking

Glassblowing

Shop Tools and Equipment

Materials and Supplies

Operation of Plant Power Plant

Electrical Piping

Grounds

Construction

Guard

Janitorial