NBSIR 74-488

EPA-550/9-74-007

Measurements of Railroad Noise-Line

Operations, Yard Boundaries,

and Retarders

J. M. Path

D. S. Blomquist

J. M. Heinen

M. Tarica

NATIONAL BUREAU OF STANDARDS

December 1974

Joint EPA/NBS Study

Approved for public release; distributio

Applied Acoustics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

NBSIR 74 - 488

EPA-550 '9-74-007

MEASUREMENTS OF RAILROAD NOISE - LINE

OPERATIONS, YARD BOUNDARIES,

AND RETARDERS

J. M. Path, D. S. Blomquist, J. M. Heinen and M. Tarica

Applied Acoustics Section

Meclianics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

December 1974

Final Report

Prepared for Office of Noise Abatement and Control U. S. Environmental Protection Agency

Washington, D. C. 20460

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

Abstract

A field investigation of noise emission from railroad operations vas

conducted. The objectives of the study were the establishment of a data

base on the noise levels associated with railroad operations, both line

(trains in transit) and yard, and the development of measurement procedures

that could be utilized in regiilations applicable to the noise from rail

carrier equipment and facilities. For trains in transit, measurements were

made as a function of horizontal distance from the tracks [five locations

at 25, 50, 100, 200 and hOO feet] and as a function of microphone height

[three different heights at the 25 and 50 foot microphone locations]. Train

passby data are presented as the maximum A-weighted sound level observed

during the passby and as Single Event Noise Exposure Levels (both A-weighted

and one-third octave band levels). A-weighted sound level measurements

were made at the boundary of the railyard, at 0.1 second intervals, for

periods of time ranging from 1 to 23 hours over several days. These data

are presented as the energy equivalent sound level and the level exceeded

ten percent of the time. The directionality of retarder noise was also

investigated. Measurements were made of the noise emitted in various directions during retarder operation.

Table of Contents

Page

1. Introduction 1

2. Field Test Program 1

2.1. Railroad Line Operations 2

2.1.1. Field Test Site (Line) 2

2.1.2. Test Procediire (Line) 6

2.1.3. Test Results (Line) 8

2.2. Railroad Yard Operations 11

2.2.1. Field Test Site (Yard) h6

2.2.2. Test Procediire (Yard) h6

2.2.3. Test Results (Yard) . 50

3. Conclusions 92

h. Acknowledgement ., . . . 93

5. References 93

6. Appendix A, Data Acquisition and Analysis System for

Line Operations 9^

7. Appendix B. Procedures for Calculation of

L and SENEL 97

8. Appendix C. DaSa Acquisition and Analysis System for

Rail Yard Boundary Measurements 99

9' Appendix D. Data Acquisition and Analysis System for

Retarder Noise Measurements ... 102

1. Introduction

The U. S. Environmental Protection Agency (EPA) is charged, under Section IT of the Noise Control Act of 19T2 (Public Law 92-57^4), with the development of railroad noise emission standards. The lav states "After con- sultation with the Department of Transportation, EPA is required to prom-ulgate regulations for surface (rail) carriers engaged in interstate commerce,

including reg^ilations governing noise emission from the operation of equipment and facilities of such carriers."

The lack of data in the public domain on the noise levels associated

with railroad operations necessitated the establishment of a substantial

data base prior to Federal rule making in this area. Through an interagency agreement, EPA requested the assistance of the National Bureau of

Standards (NBS) in the establishment of such a data base. These data, in

conjunction with data from other sources [1, 2]— , provide the technical

basis for the proposed EPA interstate rail carrier noise emission regulations.

2. Field Test Program

For the purpose of this report, the broad range of noises emitted by

railroad operations has been divided into two categories — line operations

(trains in transit) and yard operations.

The movement of locomotives and freight /par^senger cars over main line

and local branch main line tracks is termed line operations. For trains in

transit, there exists two major noise contributors — the noise from the

locomotive, or road power unit, and the wheel/rail interaction noise which

defines the car-generated noise levels.

Railroad yard operations, on the other hand, include all operations

which are conducted within the confines of the yard property boundaries,

including the classification of freight cars and services relating to the

performance testing and routine maintenance of cars and locomotives. The

classification process — the uncoupling of cars from incoming trains and

recoupling them into outgoing trains bound for various destinations — is

the major yard activity. The various noise sources associated with this

operation include: (l) switcher engine noise as incoming cars are pushed

up the hump for weighing, classification and destination determination,

(2) wheel/rail and retarder noise as the speeds of the free-rolling rail

cars which have been pushed over the hump are controlled by retarders —

rails which squeeze against the wheels of the moving cars -- as they are guided to the outgoing train make-up area and (3) the coupling noise as the free-rolling rail cars bump into the other (stationary) cars of the

outgoing train.

— Figures in brackets indicate the literature references at the end of this

report
The nolit asioelattd with both yard and lint optrationi wai invtitigattd during thii study with emphasis on the development of meaiurement

procedures and the estatlishment of a data base appropriate to railroad

operatiQns.

2.1. Railroad Line Operations

The' noise levels associated with trains in transit are dependent upon

the physical characteristics of the train, the operating speed, the condition of the wheels and rails, total weight and length of the train, and the

contour of the track bed. Although these variables can be determined, they

cannot be controlled in a field study such as this; therefore, it is difficult to correlate the noise levels and frequency spectra of successive train

passbys. This section presents a discussion of the field test site and

test procedures utilized during the data acquisition phase of the railroad

line operation study as well as a presentation of the resultant data.

2.1.1. Field Test Site (Line)

The high speed main line of the Chesapeake and Ohio Railroad, located

adjacent to the Montgomery County Fairgrounds in Gaithersburg, Maryland (in

close proximity to the National Bureau of Standards) was selected as the

field test site for the line operation noise study. The Fairgrounds provided a large grass-covered (mowed) open area free of any large reflecting

surfaces. Figure 1 is a contour map of the test site and surrounding area. The roads interspersed throughout the area are dirt with the exception of

the one adjacent and parallel to the tracks which is paved. The stands

for the baseball field are open style grandstand bleachers. Immediately

south of the tracks is a fairly dense growth of weeds and brush about 2

to 3 feet thick and 6-7 feet high. Behind the brush is a large open area

that drops in elevation until it reaches Interstate Highway TO-S which is

20 feet below the level of the track bed.

Microphones were located along a line perpendicular to the tracks as indicated in Figure 1. The point of intersection of track and the line of

microphones is approximately 520 feet from the nearest point of I-TO-S.

Along the microphone line, the ground elevation decreases as it recedes

from the tracks. The land was sixrveyed to' establish the elevation of the

microphone positions relative to the track bed (see Figure 2). For the

purpose of this measurement, the track bed is defined as the top of the

wooden ties.

At this location, two types of rails exist — continuous welded rail

on the westbound tracks and jointed rail on the eastbound track. Since

grade could be an important parameter affecting train noise, the track elevation was surveyed 300 feet on either side of the intersection between the

microphone array and the track (see Figure 3). Eastbound trains go up a slight grade as they pass the microphones while westbound trains go down

the grade.

2


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2»1.2. Test Proeidure (Line)

As stated previously, the microphones were located along a line perpendicular to the direction of travel of . the trains. For one series of

measurements, five microphones, located at distances of 25, 50, 100, 200

and kOO feet as measured from the centerline of the westbound track, formed

a horizontal array. Each microphone was mounted on a tripod and positioned

at a height of h feet above ground level. Since the ground along the microphone line was hot level (see Figure 2) the line-of-sight distance between

the microphones and the tracks w^re slightly different from the nominal

distances cited above. Table 1 shows the angle and line-of-sight distance

for each microphone in the horizontal array with respect to both the eastbound and westbound tracks . 1 ^

Table 1 Angle (0) and line-of-sight distances (d) for

each microphone in the horizontal array with

respect to the eastbound and westboiind tracks

(See Figure' 2)

Microphone West Track East Track

0 d,ft 0 d,ft

1 6° 23' 25.2 k° 10' 38.6

2 1° 9' 50.0 0° 63.5

3 0° ^1' 100.0 0° 36' 113.5

k 1° U8' "^200.1 , 1° Ul' 213.6

. 5 1° 37' hOO: 2 % ki3.6

A second series of measurements were also conducted utilizing a vertical, rather than a horizontal, microphone array-. For these measurements

microphones were mounted at heights of U, 10 and 15 feet above the ground

at horizontal distances o.f 25 and 50 feet as measured from the centerline

of the westbound track. 'Figure k illustrates the array and shows the microphone heights with respect to the track bed and ground level. The associated

table gives the angle and line-of-sight distance for each microphone with • respect to the track bed.

During both series of measurements, the m:icrophones were connected

through coaxial cables to the tape recording fii|id monitoring equipment housed

in the mobile instrumentation van. The van was located approximately 125

feet from the westbound track and 100 feet -tcp fthe '-^aM of the line along

which' the microphones were located — point A In front of the stands in

Figure 1. The data from each microphone were -Recorded on one channel of a seven-channel F..M. tape recorder. The recorder was manually started and

stopped upon the approach and subsequent departure of each train. Appendix

A contains a detailed discussion of the instrumentation which comprised the,

data acquisition and analysis system for line operation studies.

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statistical information on each train, such as, total number of cars,

loaded cars, empty cars, total weight, etc., was provided by the Chesapeake

and Ohio Railroad Company (see Tables 2 and 3, Section 2.1.3). Train speed

was determined by timing the train with a; stop watch as it traversed a marked distance of U50 feet. Depending oiji the train length, repeated timings were obtained and the average used to compute the speed.

2.1.3. Test Results (Line)

Data were obtained during 23 train passbys. For 12 of the passbys a horizontal microphone array was utilized which consisted of five microphones

located at 25, 50, 100, 200 and ^^00 feet from the centerline of the westbound track. All microphones in the horizontal array were mounted on tripods at a height of h feet above the ground. Measurements of the remaining

11 train passbys were made utilizing a vertical microphone array. In this

case microphones were located at heights of U, 10 and 15 feet above the

ground at locations of 25 and 50 feet from the centerline of the westbound

track. It was felt that the results of this data acquisition program would

provide the necessary data base (l) of the noise levels associated with trains

in transit and (2) to allow for the selection of appropriate numbers of microphones as well as location and height specifications to ensure adequate

characterization of train noise.

I In addition to the A-weighted sound level, the Single Event Noise Exposure Level (SENEL) was investigated as a descriptor of train passby noise.

SENEL is mathematically defined as:

SE.EL=XO los^,£ j-pi^]^ . XO log^„ [i^ £ 10 ^^]'

where p is the time-varying, mean-square-sound-pressure at the point of observation, L is the corresponding sound level, p is the standard reference pressure (20 micropascals) , t is the standard reference time (l second) and t is

the time (in seconds). From a practical standpoint, of course, the integration

is only carried out over a finite time interval which essentially includes all

of the acoustic energy from a given passby.— The SENEL value is very dependent on the integration time selected; errors as great as 10 dB can occiir if

the time is' too short. This is especially critical as the microphone distance

from the train is increased. Considering the train as a line source, this

effect was investigated theoretically and, considering the length and speed

of the train and the microphone distance, the integration time was selected

for each train passby such that in no case was the error due to the finite

integration time greater than 1 dB at any microphone location.

— The procedure by which the SENEL integral was evaluated from the analog

sound pressures is discussed in Appendix B.

8
Also, SENEL is easily relatable to the energy equivalent noise level (L ),

which is the level of steady state continuous noise having the same energy

as the actual time varying noise. Among the many scales used for noise and

its effect, L appears to emerge as one of the most important measiires of

environmental^Soise effects on man [3].

The data for the 25, 50, 200 and hOO foot microphones of the horizontal

microphone array are presented in the following tables and figures. It should

be noted that due to instriamentation failirre, data were not obtained at the

100 foot microphone location. On several occasions one or more microphones

were inoperative during the train passby and therefore, data are not available

in these instances either. Table 2 presents information on the characteristics of the 12 trains which were measured. Data such as the train number

(identification niomber of the lead locomotive), the direction of travel, num- ber of locomotives, number of cars and whether the cars were empty or loaded,

the total weight and length of the train and the speed of the train, are included. The acoustic data are presented in Figures 5-l6. Each figure

corresponds to a particular train and is composed of two parts labeled (a)

and (b). The one-third octave band Single Event Noise Exposure Level versus

frequency data for each microphone position are presented in Figures 5a-l6a,

while Figures 5b-l6b present the A-weighted Single Event Noise Exposure Level

and the maximum A-weighted sound level during the train passby plotted versus

the perpendicular distance from the center of the track on which the train

was running. In the upper right-hand corner of Figures 5b-l6b are shown the

average attenuation with distance (decibel/doubling of distance) of both the

SENEL and L^-j^) data.

The one-third octave band SENEL spectral data show that, as expected,

train passby noise is characterized by low frequency peaks in the range kO100 Hz related to the firing frequency of the locomotive engine. The higher

frequency portions of the spectra result chiefly from the interation of the

wheels with the rails.

Both the spectral and the attenuation-with-distance data point out why

complaints triggered by train noise come from people living miles away from

the railroad tracks. Even at distances of hOO feet from the passing trains,

the low frequency peak is little attenuated from the level measured at 25

feet. The wheel/rail noise, which is typically higher in frequency and is

generated by sources closer to the ground, attenuates at an increased rate

in comparison to locomotive noise. Because of this, a general tendency exists

for the rate of attenuation of A-weighted sound levels to increase with the

number of cars in the train, resulting from the greater contribution from

wheel/rail noise, as opposed to locomotive noise.

In order to gain some understanding of the variation in the rate of

attenuation with distance as a function of frequency, the 50 foot microphone

was selected as a reference and the differences between its reading and

9
those of the other microphones were determined — [L(x) - L(50)]-^. These

differences were computed for the octave hand SENEL values over the frequency range from 63 to UOOO Hz. The average values for each frequency were

plotted against the microphone distances. A straight line was fitted to

the average value data using the method of l*east squares . The average

values, the range, and the least squares line are presented in Figures IT

and 18. The data in these figiires are separated according to direction of

travel — east or west — which also corresponds to differences in track

type and grade. It should be noted that the least square lines have been

displaced and forced to go through 0 dB at 50 feet for westbound trains

and at 63 feet for eastbound trains. The average deviations [L(x) - L(50)]

are also plotted versus frequency for each microphone location as shown in

Figures 19 and 20 for the west and east bound trains, respectively.

As expected, there is a general tendency for an increased rate of absorption at higher frequencies. The data also seem to indicate that destructive interference is occurring in the region of 500 Hz (this phenomena

will be discussed in detail later in this section). Since the data include

both locomotives and cars — for which the effective source heights, and

hence the expected rate of attenuation, are different — no quantitative con elusions can readily be drawn.

In order to determine the influence of microphone height as a parameter

a vertical microphone array was utilized to measure the noise from 11 passing trains. As stated earlier, the vertical array consisted of six microphones — three at 'heights of U , 10 and 15 feet above the groupd at a distance of 25 feet from the centerline of the westbound track and three at the

same heights at a 50 fpot distance. The data obtained with the h foot high

microphone located at 50 feet were found to be erroneous; therefore, the

only tie with the horizontal array was the h foot high microphone located at

25 feet and this microphone was selected as the reference microphone.

These were 11 train passbys; however, on two occasions east and west

bound trains passed the microphone array simultaneously. These are noted on Table 3 which presents data on the characteristics of the trains measured

utilizing the vertical microphone array.

Figures 21 and 22 present the differences in the A-weighted Single

Event Noise Exposure Level and A-weighted sound levels that existed between

the reference microphone and the other microphones [L(x,y) - L{23 ,k)]— .

— L(x) is the noise level measiored at the microphone location whose horizontal distance from the source is defined within the parenthesis, i.e.,

L(50) is the level measured at the 50 foot microphone location. —^L(x,y) is the noise level measured at the microphone location whose

horizontal distance from the source and height above the ground are defined within the parenthesis, i.e., L(25,10) is the level measured

at the 25 foot microphone location for a microphone height of 10 feet.

10
The horizontal distances shown correspond to data for westbound trains —

the distances for the easfbound trains were 13-5 feet greater.

The chief conclusion to be drawn from these data is that some care is

required in attempting to predict levels at one vertical height from measurements at some other height. At a horizontal measurement distance of 50 feet,

assuming a 15 foot high locomotive and a 15 foot high microphone, an acoustic

signal originating from the roof-top exhaust would travel about 8.5 feet

further by lindergoing one reflection from the ground than it would travel

in going directly from the exhaust to the microphone. A distance of 8.5

feet corresponds to one-half wavelength for sound at a frequency of about TO

Hz. This is in the frequency range where the maximum sound pressure levels

due to the locomotive engine firing frequency occur. This observation would

suggest that the anomalously low levels at the 15 foot high microphone at a horizontal measurement distance of 50 feet were due to destructive interference between the direct signal and that reflected from the ground.

For measurements using a microphone h feet above the ground, assuming

a hard reflecting surface, at a distance of 100 feet from a locomotive (distances that have been suggested for regulatory purposes), a 15 foot high

so\arce (i.e., locomotive exhaust) woiild result in destructive interference

at about 500, 1500, 2500, 3500, ..Hz and constructive interference at about

1000, 2000, 3000, i+000, Hz. The first frequency at which destructive

interference occurs is well above the frequency range associated with the

fundamental firing frequency of the locomotive engine. Thus one would not

expect serious measurement errors due to interference phenomena. Similarly,

measured sound levels should be reasonably independent of small differences

in microphone height, provided the terrain is reasonably flat and level.

However, if there were a small valley between the train and the microphone,

destructive interference could occur at frequencies near that of acoustical

radiation associg-ted with the fundamental firing frequency of the locomotive

engine. As an example, ass\ame the ground falls off to about 10 feet below

track level at 50 feet away and then rises to be level with the track at

100 feet away. For exhaust noise from a 15 foot high locomotive, destructive interference would occur (for a U foot high microphone) at frequencies

of about 80, 2i+0, UOO, 560,...Hz. Destructive interference would occur

near these same frequencies if the ground fell off, for example, to T feet

below track level at a distance of 50 feet and then rose to about 5 feet

above track level at 100 feet.

2.2. Railroad Yard Operations

The noise levels associated with a railroad yard are dependent upon a variety of activities within the yard. The primary noise sources typically

are the various retarders, the coupling of cars, and the working and idling

locomotives — both road and switcher. This section presents a discussion

of the field test site and test procedures utilized during the data acquisition phase of the railroad yard operation study as well as a presentation

of the resiiltant data.

11
Table 2. Characteristics of trains on the main line during measurements made

utilizing the horizontal microphone array.

Train* Direction Locomotives Cars

T a o r1 Cars Ft/sec

weJ^^ii u Tons

T . A w + Vi Feet

Ul03 West 3 9h kQ 62 7380 7020

6607 West 2 0 0 112 300 136

Ihll West 5 138 0 33 i+890 696ii

hO^h West 6 0 0 56 900 U08

3823 West 2 20 3 30 1016 1390

k036 West ... 1+ 0 81 68 6889 1+160

k5hQ West k . 63 13 k3 U162 3920

6970 West . \

- .2 32 5 51 2100 1912

U031 West 3 0 77 87 58iiO 3900

3555 East 3 27 59 k6 1+800 1+332

6955 East 2 16 8 h9 •1535 1288

5983 East 1 2 2 36 500 260

*The numbers refer to the identification numbers of the lead locomotives.

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for train no. 4103.

LOCOMOTIVES EMPrr LOflOEO SPEED WEIGHT LENGTH

CftRS CARS ( FT/SEC 1 (TONS) (FEET)

3 94 48 62 7380 7020

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Figure 5b. Maximum A-weighted sound level (in dB re 20 MPa)

and A-weighted SENEL (in dB re 20 uPa and 1 second) versus distance for train no. 4103.
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LOCOMOTIVES EMPTY LOflOEO SPEED WEIGHT LENGTH

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LOCOnOTIVES EMPTY LORDED SPEED WEIGHT LENGTH

CARS CFIRS [ FT/SEC) ( TONS) ( FEET )

5 138 0 33 4890 6964

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LOCOMOTIVES EMPTY LOPIDED SPEED WEIGHT LEMGTH

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LOCOMOTIVES EMPTY LOflOEO SPEED WEIGHT LENGTH

CRRS CRRS [ FT/SEC ) ( TOWS) ( FEET)

2 20 3 30 1016 1390
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63 125 250 500 1000 2000 4000

FREQUENCY, Hz

8000

Figure 10a. Single event noise exposure level versus frequency

for train no. 4036.

LOCOrlOTIVES E^PTY L0ROED SPEEP WEIGHT LENGTH

CfiRS CARS FT/SEC) ( T0N5) (FEET)

4

''

'—' r

0 81 88 6889 4160

r>~'

23
60-

10 20* 50

DISTANCE/ m

' I I. L. 100

Figure lOb, Maximum A-weighted sound level (in dB re 20 juPa)

and A-weighted SENEL (in dB re 20 juPa' and 1 sec^

ond) versus distance for train no. 4036.

2k
>

w

ft; D

cno

X

w

130

Q

H

K

120 -

UO -

70 -

-1 r

1 1 1 1 1 1 r—I 1 1 1 1 1 1 1 1 « 1 r

<I> 25FT niCR0PH0NE

ffi SOFT MICI10PH0NE

200FT niCROFHONE

A. 400FT niCR0PH0NE

^^^^^

cn I—I—»—I—I—I—I—I—I—I—I—I—I\—I—I—<—I—1—I—I—1- 63 125 250 500 1000 2000 4000 8000

FREQUENCY, Hz

Figure 11a. Single event noise exposure level versus frequency

for train no. 4548.

LOcenoTivES EMPTY LOflOEO SPEED WEIGHT LENGTH

CARS CRRS 1 FT/SEC) ( TONS

)

( FEET)

4 63 13 43 4162 3920

25
Q

D

O

QW

E-» o

H

w

I

20

110-

100

90

80

70

60

D]]STANCE, ft

SO 100 200

I I » I I I I

10

500

OSENEL»-3.7 OB/00 . A LilflX. -4.0 OB/00

' I i_ 20 50

DISTANCE, m

100

Figure lib. Maximum A-weighted sound level (in dB re 20 n'Pa)

and A-weighted SENEL (in dB re 20 uPa and 1 second) versus distance for train no. 4548.

26
k1W

>

w

(Jw

D

COO

PaX

a

w

H

o

01

Eh TJ 2 C

>

O o

H

CO (U Q

CQW

EhU

O

Q

H

EH

130

120

110

100

r r r 1 t I I r t t I 1 r i t r i r f i » i O SOFT niCROPHONE:

CD 200FT MICROPHONE

A 400rT niCROPHONE

80

60 —•—'—'—I—»—•—I—'—'—I—'—'—•—'—'—I—'—'—I—'—

63 125 250 500 1000 2000 4000 8000

FREQUENCY, Hz

Figure 12a. Single event noise exposure level versus frequency

for train no. 6970.

LOCOnOTI VES EMPTY LOADED SPEED WEIGHT LENGTH

CRRS CARS I FT/SEC) ( TONS) (FEET)

2 32 5 51 2100 1912

27
20

110

100

90

80

70

60

50

DISTANCE, ft

100 200

I I

:Xx:

10

I III—

500

OSENEL.-4.2 DB/00

^LnflX. -4.5 DB/00

-I I

' ' 20 50

DISTANCE, m

100

Figure 12b. Maximum A-weighted sound level (in dB re 20 juPa)

and A-weighted SENEL (in dB re- 20 /iPa and 1 second) versus distance for train no. 6970.

28
>

w

OiD

O

diX

w

w

w

H W

O

Z <H

Eh T3 >

O o

S CN M

CO Q)

5-1 Q

S cq < T)

>

u

o

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PiH

tr: Eh

130

120

1 10

» t t r t I t I r r I T I r > I' T » I 1 »

<3> 25FT MICROPHONE

O SOFT niCRQPHONE

A 400fT niCROPHONE

70

gn •—i—'—•—1—i—» I —I—I—1—•—I—J—I—I—I

t—k.,—I—I—6- 63 125 250 500 1000 2000 4000 8000

FREQUENCY, Hz

Figure 13a. Single event noise exposure level versus frequency

for train no. 4031.

LOC0I10TI VES EtiPTY LORDED SPEED WEIGHT LENGTH

CRRS CRRS [ FT/SEC) ( TONS) (FEET)

3 0 77 87 5840 3900

I 29
CQ

•xi

o

COQ

EHO

H

I

20

110

100

90

80

70

60

DISTANCE, ft

50 100 200 500

I I III

O SENEL.-4.1

A LtlflX. -4.3

OB/00

OB/DO

10 20 50

DISTANCE, m

100

Figure 13b, Maximum A-weighted sound level (in dB re 20 uPa.)

and A-weighted SENEL (in dB^re 20 juPa and 1 second) versus distance for train no. 4031.

30
pa>

w

paD

w

o

X

w

w

w

H

o

3

(0

Z C

pa nJ >

O o

Z <N H

W 0) Q

3 CQ

CQ

ca%

u

o

Q

130

120

110

70

-f— ,—n,, 1

' I

" '

I I" I1—I r I 1' » I « r I —T r

<5> 25FT MICROPHONE

O 50PT MICROPHONE

200FT MICROPHONE

A 400FT MICROPHONE

gn I—I—I—I—I—I—I—I—IL—4—I—I—I— —ri—I—-»-—•—I—•—

L

63 125 250 500 1000 2000 4000 8000

FREQUENCY, Hz

Figure 14a. Single event noise exposure level versus frequency

for train no. 3555.

LOCOnOTI VES EMPTY LOflOEO SPEED WEIGHT LENGTH

cms ( FT/SEC) ( TONS ) ( FEET)

3 27 59 46 4800 4332

31
•T3

Q

o

o

COQW

EhO

H

w

I

20

110

100

90

80

70

60

50

DISTANCl,

100 200 500

10

I I OSENEL-3.6 OB/OD

A LMRX . -3.8 06/00

I '

' 20 50

DISTANCE, m

100

Figure 14b. Maximum A-weighted sound level (in dB re 20 /iPa)

and A-weighted SENEL (in dB re 20 ^i'Pa and 1 second) versus distance for train no. 3555.

32
>

Ed

PHD

(0O

a^

w

H

o

E-t H (tl >

O o

S CM H

W 0) Q

OQ

%

EhU

O

§

H

EH

130

120

no

100

-T—I—r "

r'

" ' ' ' r—r-—p—r' ' r"—p— 1 r—r—t—-r

r ' r—

r

<!> 25FT niCROPHQNE

O SOFT niCR-OPHONE

m 200FT rUCRQFHONE

A 400FT MICROPHONE

70

go I 1 1 1—J 1 1 ' • 1—• ' I

. ,li r« 1 1 l-r-J • * ^3 125 250 500 1000 2000 4000 80 00

FREQUENCY, Hz

Figure 15a. Single event noise exposure level versus frequency

for train no. 6955,

LOCOMOTIVES EMPTY LOflOEO SPEED WEIGHT LENGTH

CARS CARS IFT/SEC) ( TONS) ( FEET)

2 16 8 49 1535 1288

33
W

i-q Q

Z

DO

03Q

W

EHtcO

H

20

110

100

90

80

70 -

60

DISTANCE, ft

50 100 200

10

T r—»—1—

soo

©SENEL-A.l OB/00

A LtlflX. .4,5 OB/OO

J I I—_« lL. 20 50

DISTANCE, m

100

Figure 15b, Maximum A-weighted sound level (in dB re 20 isPa)

and A-weighted SENEL (in dB re 20 uPa and 1 second) versus distance for train no. 6955.

3k
>

w

p

cno

a.X

w

w

H

o

EhW

>

o

H

Q

<:W

EHU

O

Q

H

tc

Eh

C

o

Q) m

t3

130

120

110

100

-r-—r—I 1 « 1 1 1 »—T 1

' I"

' »—T—T • 1—~« '

' r-

<!> 25FT riICR0PH0NE

O SOFT niCR0PH0NE

CQ 200f T niCROFHaNE

A 400FT niCRQPHONE

60'—ir-"—

-I 1 i 1 1 4 1 1 1 «- 63 125 250 500 1000 2000 4000 8000

FREQUENCY, Hz

Figure 16a. Single event noise exposure level versus frequency

for train no. 5983.

LQCQMOTI VES EMPTY LOROEO SPEED WEIGHT LENGTH

CARS CARS 1 FT/SEC) (TONS) ( FEET)

1 2 2 36 500 260

35
20

10

100

90

80

70

60

10

DISTANCE, ft

50 100 200 500

1 111 —1 1 © SENEL. -3.5 OB/00 , A LtlRX. "5.2 DB/00

/.*v

' - o

-

1 1 1 I I

1 1 20 50

DISTANCE, m

100

Figure 16b Maximum A-weighted sound level (in dB re 20 juPa)

and A-weighted SENEL (in dB re 20 ptPa and 1 second) versus distance for train no. 5983.

36
DISTANCE, ft

20 50 100 200 500

10 20 50 100

DISTANCE, m

Figure 17a. Octave Band SENEL [L(x) - L(50)] versus distance for

west bound trains.

37
o

in

I

d

tJ

PiD

COO

x

H

03H

o

M

O

ISH

CO

M

EMU

O

20

10

0

-

-10 -

10

0

10

10 -

0

-

-10 -

10

10

DISTANCE, ft

50 100

I I II' 200I 500

1000 HZ

-^•Q OB/00

2000 HZ

-^•3 08/00

4000 HZ

-^•0 08/00

R-WT

-4.3 08/00

J 1 i I I I l_ 10 20 50

DISTANCE, m

100

Figure 17b. Octave band SENEL [L(x) - L(50)] versus (distance for

west bounci trains.

38
CO

o

I

>

W

PiD

w

O

X

cnH

o

is

EHz

w

>

Z

H

W

Q

CQW

%

EhU

O

20

10

-10

10

0

-10

10

I 0

-10

10

0

-10

DISTANCE, ft

50 100

I I I I

r 200I

500

63 HZ

-2.7 DB/DD

125 HZ

-1.8 DB/DD

250 HZ

-3.2 DB/DD

500 HZ

-4,6 OB/DO

10 20 50

DISTANCE, m

I I , > I, I I 100

Figure 18a. Octave band SENEL [L(x) - L(50)l versus distance for

east bound trains.

39
73

O

in

I

X

>

w

w

PiD

cno

CMX

w

H

o

>

W

W

i-q O

P3H

w

p

i

EHUO

20

lOh

0

lOf10

0

10

10

0

10

10

0

10

DISTANCE, ft

50 100 200 500

I I I I I I I I

1000 HZ

-3.8 DB/00

2000 HZ

-3.5 OB/DO

4000 HZ

-3.6 OB/DO

fl-WT

•3.7 OB/00

-I I I I I I I u 10 20 50

DISTANCE, m

100

Figure 18b. Octave band SENEL [L(x) - L(50)] versus distance for

east bound trains.

)40
Figure 19o Octave band SENEL [L(x) - L(50)]

versus frequency for west bound

trains

.

(3 -©

Ann

Ul

J
D

UlO

ftw

w m

H

o -

EH o

S in

I O X

s —

EHUO

53 125 Z5Q 500 1000 2000 4000

FREQUENCY, Hz

Figure 20. Octave band SENEL [L(x) - L(50)]

versus frequency for east bound

trains.

_25_ -A

©ZHD o

400

U2
Table 3. Characteristics of trains on the main line diiring measurements made

utilizing the vertical microphone array.

Tram* Direction Locomotives

Empty

Cars

Loaded

Cars

Speed

Ft /sec

Weight

Tons

Length

Feet

3692 West ),

• 74 1, c 45 39 DD02 6032

West 2 0 0

ii It 44 300 13d

d493 iLast 1 d d 30 2d0

hast 0d

on 0 313 AU

)i 1 41 ) I 0 0 0 d4£;4

Jijast 3 0

lift 110 44 7730 pobo

41(J 0'"' West 3 0 DO 52 4730 oil 34DO

hast ), 29 33 2900 1720

wes b d 0 0 44 300 13d

9910*** East 1+ 0 0 87 236 3I+Q

11+56*** East 1 3 0 107 239 3I+9

9911*** East 0 0 88 236 3i^9

*The numhers refer to the identification numbers of the lead locomotives.

**Simultaneous Passby

**Coii]muter Trains

U3
in

Hi

s.

X.

paw

H

s

EH -5

H

W

g

Eh

iH0

H

I -10

25/10 25/15 50/10 50/15

WEST BOUND

O EPIST BOUND

A WEST/EflST BOUND

<^ ERST BOUND COMMUTER

MICROPHONE LOCATIONS

horizontal distance/height

Figure 21. A-weighted SENEL [L(x,y)

microphone locations.

- L(25,4)] for various

kk
m

in

1-3

I

>

Q

Z

DO

W

Q

W

EH

!l! OM

&

I <

aD

sH

-5

-10

-15

()

fi.

25/10 25/15 50/10 50/15

O

A.

WEST BOUND MICROPHONE LOCATIONS

ERST BOUND horizontal distance/height

MEST/EflST BOUND

EflST BOUND COMMUTER

Figure 22. Maximum A-weighted sound level [L(x,y) - L(25,4)] for

various microphone locations.
2.2.1. Field Test Site (Yard)

Bail yard measurements were made at the Norfolk and Western Railroad

Terminal located in Roanoke, Virginia. The Roanoke terminal is the eastern

hub of the Norfolk and Western Railway system and as such is operated on a

2i|-hour, T days per week basis. The following statistics are presented

to provide an indication of the size and activity of the facility: • There is an average of U5OO cars handled daily through the terminal,

with peak loads near 65OO cars. An average of over 85 trains arrive

and depart Roanoke on a daily basis. • Approximately 2100 cars each day are classified over the dual hump

(master retarders).

•The classification yard contains 55 classification trkcks with a capacity of approximately 1950 cars. •The receiving yard contains 20 tracks with a capacity of approximately

2000 cars. • The hump computer controls 2 master, 2 intermediate, and 9 group

retarders, and 65 switches. • The terminal contains 228 miles of track.'

A reduced' reproduction of a detailed map of the Roanoke Yards is shown

in Figure 23. Superimposed on the map are the microphone positions at the

yard perimeter (locations Al, A2, Bl and B2) and within the yard (location

C) which were utilized for rail yard measurements.

. 2.2.2. Test Procedure • (Yard)

Measurements were made at four locations (designated Al, A2, Bl and B2)

along the boimdary of the Roanoke train yard and at one location (designated

C) within the yard. .

• ,

Microphone positions Al and A2 were selected because of their proximity

to the intermediate and group retarders and the car coupling area respectively.

Figure 2k shows an overview of this area with microphone number Al in the

foreground. The two microphones at location A were mounted on tripods at a height of 5 feet above the ground. They were located at the edge of an em- bankment which was approximately 50 to 60 feet above the level of the track

bed of the nearest track. The line-of-sight distances from the microphones

to the edge of the nearest track were 65 and 81 feet for locations Al and A2

respectively.

At microphone' positions Bl and B2 (see Figure 25) the microphones were

also mounted 5 feet above the ground at the edge of an embankment. At this

U6
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CO -i-i O

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C

CO

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•1-1 i-( > --^CO " ;j

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C u-i COO •« OS o

*> 13

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'1-1 •» g CM

5-1 CQ

a> H »

-d PQ

toO " U <N

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•I-I cO " c

i-i T)

<U (U 4J 4J

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IS

M

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C! (1) CO T3

r-l CO o a

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0)

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X!

CL, i-l O D

^-1 to O CO to •!-) (U

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0)

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•I-I fa

47
48
O

J3

O-OUO

•i-l Bco

•I-l 4J

aiOO

XIp

bOC

•Ho

Xim

13

COC

•H

«0

J-i 4JOcO

<u

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in

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49
location the embankment was 35 to 4 5 feet above the level of the nearest

track. The noise levels measured at this location were dominated by the

noise from stationary (idling) and moving locomotives.

In order to gain a better understanding of the noise levels and the

directionality patterns of the noise associated with retarders , measurements were also made within the yard interior. This location is designated

location C. Figure 26 shows the eight microphone positions utilized. Retarder number 1 was selected as the primary source to be studied; therefore,

all positions selected' are in relation to this retarder. The noise from

retarder number 2 was also measured and dimensions relative to this retarder are also given. Microphone position 1 was established on a line perpendicular to retarder number 1 and 50 foot from the centerline (both longituinal and lateral) of this retarder. Microphone heights of 5j 10 and 15 feet

above the ground were utilized at microphone position number 1. A line was then drawn through microphone position number 1 parallel to the long axis of

retarder number 1. Microphone positions 2 and 3 were located along this line

at an angle of 30° and ^5° respectively, in relation to the line from microphone number 1 perpendicular to retarder number 1. At these two positions,

microphone heights of 5 and 15 feet were used. A final position, number h, was located at an angle of 75° but as close to retarder number 1 as possible

rather than along the line of microphone positions 1,2 and 3. At location

h a single microphone height of 5 feet was utilized. Since various locations and heights were utilized, it was determined that one way to keep

track of the positions would be to designate each with an angle and a height

which would uniquely define each measurement position. For example, the

microphone at the five foot height at position 1 was designated (0°, 5 ft.).

For each measurement two microphones were utilized. One of the microphones was always at the reference position — location 0°, 5 ft. — while

the other microphone was successively placed at the other seven test positions

as indicated in the table of Figure 26. Figures 27 and 28 show the reference

microphone (0°, 5 feet) and a test microphone (0°, 10 feet) from two different perspectives showing the area in and around the retarder locations.

2.2.3. Test Results (Yard)

A-weighted sound level measurements were made at the boundary of the

rail yard at 0.1 second intervals utilizing a mini-computer-based digital

data acquisition system (described in Appendix C). Data were taken for periods of time ranging from 1 to 23 hours over a 7 day period.

Data at positions Al and A2 were taken from 1200 hours of the 1^5th day

of 1973 until 1000 hours of the 150th day of 1973. At positions Bl and B2,

data were taken from 1100. hours of the 150th day of 1973 until 1000 hours

of the 151st day. ' The data resulting from these measurements are presented

in this section in the form of the A-weighted soiind levels exceeded ten

percent of the time (L-^q) and the energy equivalent A-weighted sound levels

(L ), both plotted as functions of time.

50
MICROPHONE LOCATIONS

SCALE: = 25 FT.

LOCATION e HEIGHT. FT.

#1 0" 5. 10. 15

#2 30° 5, 15

#3 45° 5. 15

#4 75° 5

Figure 26. Measurement location C. Microphone locations near retarders. ^ is defined as the angle between lines

drawn from microphone number 1 and any other microphone

through the intersection of the longitudinal centerline of retarder number 1 with the perpendicular line

drawn from microphone number 1 to retarder number 1.

51
Measurement position C. Retarder number 1 is to the left, retarder

number 2 is to the right with the master retarder and hump in the

background. The two microphones in this photograph are the reference

microphone (9 = 0", height = 5 feet) and one of the seven test

microphones (9 = 0°, height = 10 feet).

52
Figure 28. Measurement position C. View of retarder number 1. The two

microphones in this photograph are the reference microphone

(e = 0" , height = 5 feet) and one of the seven test microphones (e = 0", height = 10 feet).

53
The energy equivalent noise level, L , for a stated period of time is

the level of a constant, or steady state, ^Soise which has an amount of acous

tic energy equivalent to that contained in the measured time-varying noise.

L is mathematically defined as: i eq

^e, = ^0 ^-10 [^f (if " loS,o [Ifj

10^^^>/^° dt] .

where p is the time-varying, mean-square sound pressure at the point of

ohservation, L is the corresponding sound level, p is the standard Reference pressure (20 micropascals ) and T is the perioS of integration. —

The A-weighted L^^ sound levels at locations Al and A2 are presented

in Figures 29a- 3^a for days 1^5 - 150. The hourly equivalent A-weighted

sound levels, i.e., L for each hour, for locations Al and A2 for days

1U5 - 150 are presented: in the complementary Figures 29^ - 3^b. Similar

data for measurement locations Bl and B2 are presented in Figures 35a - 36b.

The data points on these plots represent the cumulative noise level during

the preceding hoior; that is, the data poini: at 1200 hours represents the

noise which occurred between 1100 and 1200 hours . The lack of data at cer- tain hovirs on these plots is due either to inclement weather or electrical

power failures or power fluctuations which affected the data acquisition

system at the field test site.

To provide some indication of th? correlation between specific ' activity

within the yard and the L and so\ind levels measured at the boundary of

the railyard, retarder activity fr3m I6OO hours on day 1^+9 until O9OO hours

on day 150 has been .summarized in Table h.. Since measurement locations Al

and A2 along the railyard boundary were in the vicinity of the active retard

ers, the operations can easily be compared with the corresponding values of

L _ and L A-weighted sound levels for these days as shown in Figures 33a,

33b, 3ka ISd 3Ub.

The data contained on plots 29a - 36b are compressed into two summary

plots (Figures 37 and 38) which show the L and A-weighted sound levels

for the total time period (days 1^5-151). Note thaS the data prior to 1100

hours of day 150 was for location A while data -after this time was for location B.

It is important at this time, on the basis of these data, to examine

the relationship between L^^ and and evaluate the appropriateness of the

two measures as descriptors of the^Soise emanating from railroad yards.

Figures 39 and ko show plots of L- versus L at microphone positions Al

The procedure by which the L integral was evaluated from the digital

data is discussed in Appendix^B.

5h
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CMO

CMO

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to

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edT/ oz ap "TaAgT awnos ott oaj.HoiaM-v

55
56

m oo to

^d^i OZ 9J HP

'laAai amos aaiHoiaM-v i-NaivAinoa ArEnnoH

58
59

61
T8df^ OZ 3-^ 9P

"laAai QMnos aai.HDiaM-v iiNaiVAinOa AinnoH

62
63
64
65

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67
68
69
70
Tatle h. Sur.::..\ry of retarder activity from 16OO hoiirs on day

1^+9 until 0900 hours on day 150.

Retarder Operations Empty Loaded

Day Start Finish Cars Cars

IU9 1616 1650 90 0

1705 1736 35 35

1756 1808 31 51

- X04U T A)i n % %

1936 I95U 19 . 2i^ 2019 2oi+5 33 31

2100 2127 \\ 23

2131 2139 9 9

2223 2300 27 25

2323 2331 2 18

150 0010 0050 36 19

0100 0122 —J 50

01U8 0207 20 22

021U 0233 38 21

0310 0321 9 25

0333 0!il3 101 0

OU06 0)+23 25 8

Oi^36 OU5U ii9 0

05U5 0607 23 60

0627 0635 0 18

0816 0829 9

0835 0913 In g

71
72
73
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75
and A2 respectively for measurements made on day ll+9' As can easily be ' seen, the correlation between the tvo descriptors is not veiry good in this

case. The probable reason for the large differences — as much as 20 dB —

between - and L is the fact that short duration, high level noises which

10 eo do not occur more than 10 percent of the time have a significant influence

on the value of L but absolutely no influence on the value of L^q. A

review of the raw^Sata confirmed this to be the case for railyard measurements

taken during this study. For those hours where the differences between L^^

and L were the largest, the raw data showed that high level noises occurred

for neirly 10 percent of the time and therefore, the L value tended to be

much higher than the L^^ value (which was not influencIS at all by the high

level noises since they did not occur more than 10 percent of the time during the hour of interest). What these data show is that the nature of the

activities within a railyard are such that L^^ is a poor descriptor of the

noise in this case. Similar data have been reported [k] for and

data at sites near airports. Differences between the two descriptors wire

as much as 20 dB over a major portion of the day at a residential site

under the landing path of Los Angeles International Airport while for a suburban residential site, comparable L and values were reported over

a 2k hour day (typical differences on the order^Sf a few decibels or less).

is a relatively simple descriptor but it should be utilized with caution,

especially in situations where high level sounds occur for short periods of

time.

However, L is not without problems either. It has been previously

reported [l], in'^the case of railroad yard boundary measurements that:

"In general, the 10 minute sample times utilized for this survey [Wyle

survey] were of insufficient duration for accurate measurement of the yard

activities, indicating that due to the random nature of most yard operations, 2k hour continuous recordings would most likely be required."

In order to investigate this problem further, the data for the time

period from OOkl hours to 02^0 hours of day 150 were selected for investigation as to the variation one could expect in the values of L as a result of the integration time selected. The results (for mealtlrement positions Al and A2) are presented in Figures kl - k3 for integration times of

1, 3, 10, 30 and 6o minutes. Since the A-weighted sound levels were digitally recorded every 0.1 second, this corresponds to 600, l800, 6000, l8,000

and 36,000 samples, respectively. The values. of L plotted in these figures correspond to the beginning point of the intef^-ation time; that is, in

Figure k2 the data plotted at kO minutes represents the L value for the

period extending from the beginning of the ^Oth minute to^She beginning of

the U3rd minute. Since only a two-ho-ur data sample was used, there are no L^^ values plotted over the last period of integration of the two-hour period.

On the basis of these data, it woiild appear that regulation of rail yard

noise emission levels, in terms of L , would require, at a minimum, continuous monitoring for each of several representative hours in a given day. Con76
77 3
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81
tinuous monitoring for 2^ hours on representativ© days would, of course, yield

more reliable results. On the other hand, if it is desired to relate variations in L with specific variations in yard activity, integration times in

the range o? 1 to 10 minutes would he preferred.

As discussed previously in Section 2. 2. 2. , measurements were also made

within the r'ail yard near the active retarders to investigate the characteristic retarder noise levels and directionality — "both in the horizontal and

vertical planes. A reference microphone was utilized in conjunction with . seven different test microphones. Each test microphone was located at a different height/angle combination in relation to the location of the reference microphone (see Figure 26 for microphone locations with respect to

retarders 1 and 2).

Data were obtained for 58 passes through retarder nijmber 1 and 37 passes

through retarder number 2. The data for each train car passing through the

retarders are presented in the form of (l) the differences in the A-weighted

sound level between the test and the reference microphones and (2) the maximum A-weighted sound levels at the reference microphone. For selected passes

through retarder number 1, one-third octave band spectral analysis was also

performed and the data are presented here.

The^differences between the maximum A-weighted sound levels at the test

[L(Q^,x)]— and reference [(L(0, 5)] microphones are presented graphically in

Figures U6 and hj . In addition, the data are tabulated in Tables 5 and 6.

The levei differences are coupled with an identification of the type of rail

car passing through the retarder at the time of the measurement. No information was obtained as to whether the numbers and types of cars sampled during

this study were representative of the long-term operational statistics for

this particular rail yard. An indepth study of retarder squeal (which was

not the intent of this study) would of necessity have to investigate such

facts as car age, condition and type of wheels, car weight, environmental

conditions, speed, etc. ., ^

In summary, the average sound level differences between the test and reference microphone locations as well as the standard deviations are presented

in Table T. Note that in the case of position (T5,5) the data are shown for

retarder number 1 and number 2 seperately rather than combin'ed. The data were

plotted in this manner since this location is much closer to retarder number 1

than it is to retarder number 2. At all other measurement locations, the

microphone is approximately equidistant from the two retarders.

L(0,x) is the noise level measured at the microphone location whose

height above the ground and angular location with respect to the perpendicular line drawn from microphone number 1 (see Figure 26) to the

longitudinal centerline of retarder n\imber 1 are defined within the

parenthesis, i.e., L(0,5) is the level measured at an angle, 0, of

0° and a microphone height, x, of 5 feet.

82
24

22

20

18

16

14

12

10

8

6

4

2

0

-

-2 -

-4

-6

-8

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MICROPHONE LOCATIONS (angle/height)

C)

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Figure 46. Maximum A-weighted sound level [Hd,x) - L(0,5)

various microphone locations, retarder no. 1.

for

83
24

22

20

18

16

14

12

1 0

8

6

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2

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-6

-8

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MICROPHONE LOCATIONS (angle/height)

75/5

Figure 47. Maximum A-weighted sound level [L{e,x) - L(0,5)] for

various microphone locations, retarder no. 2. ,

Qk
Table 5. The difference in maximum A-weighted sound level [L(0,x) - L(0,5)] between the

test and reference microphones for 58 passes through retarder number 1.

TYPE CAE • 0°,10 Ft TYPE CAR 0°,15 Ft TYPE CAR 30°,

5

Ft TYPE CAR 30°, 15

Box l+.O Large Tank ll+.U Box 2.0 Flat (2) -8 .k Box(2) Box 11.6 Box -3.0 Box 7 .6 Coal 3.6 Box 5.0 Box 2.2 Box(2) -1

Box U.6 Gondola 1.8 Box & Tank -2.0 Box 3^.0 Box 6.U Box 3.8 Box -0 .2 Box 6.8 Box l.h

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Box(2) 21.6 Box(2) i+.o Box -5.2

Box 17.8 Box 7.2 Box -11.2

Flat & Tank 19.6 Box i+.8 Gondola(2) 16. ii Box 10.2

Gondola(2) 13.lt Gondola ll+.O

Box -2.8

Large Flat 13.1+ Coal(2) 12.1+ Tank(2) 7.0

85
Table 6. The difference in maximum A-veighted sound level [L(0,x) -L(0,5)]

between the test and reference microphones for 37 passes through

retarder number 2.

TYPE CAR 0°,10 Ft TYPE CAR

Box(2) 3.0 Box

Gondola(2) 10.6 Coal(2)

Box -k.k Gondola

Tank(2) 10.8 Box(2)

Box(2)

Box

TYPE CAR 30° ,15 Ft TYPE CAR

Box 0.6 • Box(2)

Box -3.2 Box

Box k.6 Box

Box 0.1; Box & Cement

Tank -1.2 Box

Automobile h.6 Box(2)

Automobile -2.k Gondola

Box -2.U

Box 3.0

Box(2) 8.8

Gondola 1.6

TYPE CAR 75°. 5 Ft

Box -3.6

Grain -2.2 . .

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10.0 Cement 5.6

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18.0 Flat l;.l; 18.8 Grain 5.8

20.8 Box -0.2

l6.2

16.0

19.2

18.6

86
Table T. Summary of the average differences in A-weighted sound

level between the test and reference microphones and

the corresponding standard deviations.

Retarder

Microphone L(0,x) - L(0,5)

lie Hpt-Lfijli xrhtO Average Std. Dev.

#1 & #2 #1 0° 10 ft. +i;.8 dB h.l dB

#1 & #2 #1 0 15 +10.0 5.1

#1 & #2 #2 30 5 +1. ( )i o n & #2 #2 30 15 +0.9 h.3

#1 & #2 #3 ^5 5 +18.3 2.k

#1 & #2 #3 U5 15 +h.3 2.6

#1 75 5 +2.9 8.6

#2 75 5 -1.2 5.2

It can easily be seen that the noise radiation characteristic of retarders

exhibit strong directionality in both the horizontal and vertical planes. Much

more detailed mapping of the sound field would be needed to adequately characterize the directions of minimum and maximum radiation.

The maximum A-weighted sound levels for the reference microphone were tabulated for all passes through the retarders. The tabulated data were

grouped into 5 dB steps for the range of 100 to lUO dB. Since only those

cases where the maximum exceeded an A-weighted sound level of 100 dB are presented, these data should not be construed as being indicative of the average

noise levels associated with retarder operations. The tabulation was performed individually for each retarder. These data are presented in Figirres

HQ and U9 for retarders number 1 and 2 respectively.

To provide an indication of the spectral content of "retarder squeal" a limited amount of one-third octave band analysis was performed. One event was randomly selected from the group of events that comprised each 5 dB step

for passes through retarder number 1. These events are labeled A through G.

The one-third octave band sound pressure levels versus frequency measured at

the reference microphone at the time corresponding to the occurrence of the

maximum A-weighted sound level are presented in Figures 50a and 50b for each

of the randomly selected events. The absence of data at certain frequencies

indicate that the soiand pressure levels were not above the base line of the

analysis equipment. It should be noted that on curves A and G there is a single datum point at 63 Hz.

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3. Conclusions

Based on the data obtained diiring the conduct of this test program, the

following conclusions can be drawn:

• The Single Event Noise Exposure Level (SENEL) value, is very dependent

on the integration time selected; errors as great as 10 dB can occur if

the time is too short. This is especially critical as the microphone

distance from the train is increased.

• A general tendency exists for the rate of attenuation to increase with

the number of cars in the train, reflecting a greater contribution

from wheel/rail noise (high frequency) as opposed to locomotive noise

(low frequency). • If the terrain between the train and the measurement location is not

reasonably flat . and level , destructive interference can occur at frequencies near that of the acoustical radiation associated with the

fundamental firing frequency of the locomotive engine.

. 9i Caution should be exercised if attempts are made to predict the

noise levels- for trains in transit at locations other than the ones

at which measurements were actually taken. This is especially critical for changes in vertical height. • The nature of activities within a railyard are such that L^^ is a poor descriptor of the noise at the boundary of a railroad yard. • Regulation of railyard noise emission levels, in terms of L , would require, at a minimum, continuous monitoring for each ^8f

several representative hours in a given day. Continuous monitoring for 2k hours would be preferable. • The noise radiated from active retarders is highly directional in

both the horizontal and vertical planes, and any attempts to regulate

retarder noise should consider this directionality.

92
h . Acknovledgement

Appreciation is expressed to officials of tl^e American Association

of Railroads, officials and personnel of the Norfolk and Western Railroad,

and officials and personnel of the Chesapeake and Ohio Railroad, for their

assistance in this measurement program.

The authors also express appreciation to the following members of the

Applied Acoustics Section: John S. Forrer, Charles 0. Shoemaker and

Richard B. Gold for the development of the data acquisition and analysis

system and Daniel M. Corley and Ronald L. Fisher for the associated software .

5^ References ,

[l] Swing, J. W. and Pies, D. B. , Assessment of noise environments around

railroad operations. Report WCR 73-5 (Wyle Laboratories, El Segiindo,

California, July 1973).

[2] Rickley, E. J., Quinn, R. W. and Sussan, K. R., Noise level measurements of railroads: freight yards and wayside. Report DOT-TSC-OST73-^6 (Department of Transportation, Transportation Systems Center,

Cambridge, Massachusetts, May 197^)-

[3] Public health and welfare criteria for noise. Report 550/9-73-002

(U. S. Environmental Protection Agency, Washington, D. C, July 27,

1973). Available from the Superintendent of Documents, U. S.

Government Printing Office, Washington, D. C. 20U02

[h] Bishop, D. E. and Simpson, M. A. , Noise levels inside and outside

various urban environments, Sound and Vibration 8_ (5), 51-5^ (May

I97U)

[5] American National Standard Specification for Sound Level Meters,

Sl,i;-1971 (American National Standards Institute, New York, New

York, April 1971).

93
6. Appendix A. Data Acquisition and Analysis System

for Line Operations

Figure A-1 identifies the components of the data acquisition system

utilized for the measurement of noise from trains in transit. To describe

the workings of the system, the following example is cited with the con- tribution of each component discussed.

Consider a train passing an array of microphones. As the train moves

forward, it causes pressure fluctuations which travel as waves and activate

each microphone's diaphragm into vibration. These vibrations are transduced

into an AC voltage which can be recorded for analysis at a later time. The

microphone itself was a three-part subsystem comprised of a one inch con- denser microphone cartridge, protecting grid and a microphone preamplifier.

Battery-powered microphone power supplies were utilized to provide the necessary polarization voltage to the microphones. It was not practical to locate

the tape recorder next to the microphone array, since one wanted to minimize

undesired reflection effects; therefore, long cables carried the signal from

the microphone to the recording facility housed in a mobile instrumentation

van. Once the signal reached the tape recorder there existed a need for

signal conditioning prior to actual recording. A specially designed electronic system provided the necessary amplification/attenuation capability

and in addition-, through a series of panel lights, provided an indication as to whether or not a tape channel had become saturated (i.e., the signal had

exceeded the dynamic range of the recorder) and thus the data were not

acceptable. The signal from each microphone was then recorded on one track

of the seven-channel F. M. tape recorder. Windscreens were placed over the

microphones at all times. . .

A single point calibration utilizing a pistonphone which produced a

12k dB sound pressure level (re 20 micropascals ) at a frequency of 250 Hz , was used for system calibration in the field. .

Once the data had been recorded, the analog tapes were returned to the

National Bureau of Standards for reduction and analysis. Figure A-2 identifies

the equipment which was utilized for analysis purposes. Each tape was played

back a channel at a time through the real-time analyzer. An interface was necessary to ensure compatibility between the real-time analyzer and the

mini-computer. The time constant for the one-third octave filters was 0.2

second above 2 kHz and below 2 kHz the time constant increased with decreasing frequency to 20 seconds at 20 Hz. The time constant for the A-weighting

network was 21+0 milliseconds which corresponds to the requirement for "RMS

Fast" specified in American National Standard SI.U-1971 [5]. Once all data

had been analyzed in one-third octave bands, the computer stored the data and

dumped it onto digital magnetic tape formatted to be acceptable to the large

NBS computer which was utilized for further analysis and graphical plot generation.

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T. Appendix B Procediires for Calculation

of L and SENEL

eq

The eqioivalent sound level (L ) is the average, on an energy basis,

noise level (usually the A-weighte^^level) integrated over some specified

amount of time. The piarpose of L is to provide a single niimber measure of

the time-varying noise for a p^'edeSermined time period. Equivalent, in this

case, means that the numerical value of the fluctuating sound is equivalent

in level to a steady state sound with the same amount of total energy.

is defined as: eq

L =10 log,^

eq ^10

where p is the time-varying, mean-square sound presstire at the point of observation, L is the corresponding sound level, p is the standard reference pressure (20 micropascals ) and T is the period of integration.

A specialized mini-computer-based digital data acquisition system (described in Appendix C) was utilized for measurements of A-weighted sound levels

for rail yard boTindary measurements. Data were sampled at 0.1 second intervals. For discrete sampling of the A-weighted sound level for a specified

time period, equation B-1 becomes:

n

1 z

where L is the instantaneous A-weighted sound level for the ith sample and n is

the number of samples of L in a specified time peripd.

The Single Event Noise Exposure Level (SENEL) provides a measure which

quantifies the effect of duration and magnitude for a single event. In this

case, SENEL is a measTire of the individual train passby which time integrates

the level accumulated during this event with reference to a duration of one

second. SENEL is defined as:

L^o J "-Q L o

where p is the time-varying, mean-square sound pressure at the point of observation, L is the corresponding sound level, p is the standard reference pressiare (20 micropascals) and t^ is the standard reference time (l second).

An analog data acquisition system (described in Appendix A) was utilized

for rail line noise measurements. As the train passed the microphone array,

voltages corresponding to the sound pressures at each of the measurement loca-

(B

97
tions were recorded on magnetic tape in analog form. During analysis , each

analog tape was played back a channel at a time through a one-third octave

band real-time-analyzer interfaced to a mini-computer. One-third octave band

sound pressure levels and A-veighted sound levels were digitized and stored

on magnetic tape. The analog data were sampled at 0.3 second intervals. For

temporal sampling of the data, equation B-3 becomes:

where L is the instantaneous A-weighted sound level or one-third octave sound

pressure level for the ith sample. At is the time interval between samples,

t^ is the standard reference time (l second) and n is the number of samples

included in the time interval which essentially includes all of the acoustic

energy from a given passby. That is, from a practical standpoint, the noise

samples must be taken during the time the signal is within a given number

of decibels down from the maximum value. As was pointed out in Section 2.1.3.,

the SENEL value is very dependent on the integration time selected. For this

study, the integration time for each passby. was selected to ensure that the

error due to the finite integration time was no greater than 1 dB at any microphone position.

n SENEL

o 1=1

(B-4)

98
8. Appendix C. Data Acquisition and Analysis System

for Rail Yard Boundary Measurements

To facilitate data acquisition in the field, a specialized mini-computer

based digital data acquisition system was designed and fabricated "by NBS. This

system "was utilized for measurements of A-weighted sound levels near the rail

yard property line.

The analog portion of the system consisted of a condenser microphone, a battery-powered microphone power supply, an amplifier, an A-weighting network, a true r.m.s. detector log converter and a sample and hold amplifier

(see Figure G-l). The dynamic range of the amplifier was 80 dB. The r.m.s. detector had a time constant corresponding to r.m.s. fast response for a type-I sound level meter as specified in American Rational Standard Sl.^l1971 [5]. The sample-and-hold circuitry was under computer control and

maintained the time coherency between the two channels utilized for data

acquisition. A third channel was used for calibration and synchronization.

The digital portion of the system consisted of a three-channel m\iltiplexer, an eight-bit analog-to-digital converter (ADC), an asychronous first

in-first out memory (FIFO), a time-of- day clock (the data and time of day

are recorded automatically) and a power fail safe unit to ensure that no

data were lost in the event of a power failure. The system was self-correcting in time of day and channel synchronization when power failed and was designed so that no data were lost while the computer was writing data on

the digital tape or writing the analyzed data on an output device. Additionally, a read-only-memory (ROM) was used for the timing of the various functions of the digital section.

The data were sampled and held ten times per second. The aperture time

of the sample and hold circuitry was 20 nanoseconds with a hold drift rate

of one millivolt per second. One millisecond after the data were sampled,

the reference channel was multiplexed to the ADC. The two data channels were digitized using a ten bit ADC. The output of the ADC was connected to

a first in-first out asynchronous external memory so that data could be

written on magnetic tape without losing new input data.

Initial calibration and check-out of the system in the field was performed using a program which interrogated the multiplex Interface and

printed the internal reference value and the values for channels one and

two on the teletype writer. Additionally a Fortran program was used to

scan the data tapes and print selected values as a check on the quality of

the data while still in the field. A pistonphone which produced a 12h dB

sound pressure level (re 20 micropascals ) at a frequency of 250 Hz was also

used for single point calibration. The digital tapes were returned to the

National Bureau of Standards for reduction and analysis. Figure C-2 identifies the instrumentation which was utilized for analysis purposes.

99
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101
9. Appendix D. Data Acquisition and Analysis System for

Retarder Noise Measurements

The data from the reference and test position microphones were recorded

on separate channels of a two-channel, direct record tape recorder. The data

acquisition system is shown in Figure D-1. A single point calibration utilizing a pistonphone which produced a 12h dB sound pressure level (re 20

micropascals) at a frequency of 250 Hz was used for system calibration in the

field.

Once the data had been recorded, the analog tapes were returned to the

National Bureau of Standards for reduction and analysis. Figiire D-2 identifies

the instrumentation which was utilized for reduction and analysis purposes.

The time constant for the one-third octave filters was 0.2 second above 2 kHz

and below 2 kHz the time constant increased with decreasing frequency to 20

seconds at 20 Hz. The time constant for the A-weighting network was 2^0 milliseconds which corresponds to the requirement for "RMS Fast" as specified in

American National Standard SI. i|-19Tl[ 5 ]

102
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NBS-114A (REV. 7-73)

U.S. DEPT. Or COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 74-488

2. Gov't Accession

No.

3. Recipient's Accession No;

4. TITLE AND SUBTITLE

Measurements of Railroad Noise -- Line Operation, Yard

Boundaries, and Retarders

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S) J. M. Fath, D. S. Blcmquist, Jo M. Heinen, and

M. Tarica

8. Performing Organ. Report No. NBSIR 74-488

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 2130498

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Office of Noise Abatement and Control

U. S. Environmental Protection Agency

Washington, DoCo 20460

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

A field investigation of noise emission from railroad operations was

conducted. The objectives of the study were the establishment of a data

base on the noise levels associated with railroad operations, both line

(trains in transit) and yard, and the development of measurement procedures

that covild be utilized in regulations applicable to the noise from rail

carrier equipment and facilities. For trains in transit, measiirements were

made as a function of horizontal distance from the tracks [five locations

at 25, 50, 100, 200 and hOO feet] and as a function of microphone height

[three different heights at the 25 and 50 foot microphone locations]. Train

passby data are presented as the maximum A-weighted sound level observed

during the passby and as Single Event Noise Exposure Levels (both A-weighted

and one-third octave band levels). A-weighted sound level measurements

were made at the boundary of the railyard, at- 0.1 second intervals, for

periods of time ranging from 1 to 23 hours over several days. These data

are presented as the energy equivalent sound level and the level exceeded

ten percent of the time. The directionality of retarder noise was also

investigated. Measiorements were made of the noise emitted in various directions during retarder operation.

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; noise measurement; noise (sound); railroad yard; trains

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