NBSIR 74-446

Pecos Truck Tire Noise Study:

A Summary of Results

William A. Leasure, Jr. and

Denzil E. Mathews

Applied Acoustics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

January 1974

Final Report

Prepared for Office of Noise Abatement

U. S. Department of Transportation

Washington, D. C. 20590
Disclaimer

The tires and vehicles were selected for this test by the Truck

Tire Noise Subcommittee of the Society of Automotive Engineers, Inc.

The commercial vehicles and instruments are identified in this report

in order to adequately describe the experimental procedure. In no

case does such identification imply recommendation or endorsement by

the National Bureau of Standards, nor does it imply that these vehicles

and instruments were necessarily the best available for the purpose.
NBSIR 74-446

PECOS TRUCK TIRE NOISE STUDY:

A SUMMARY OF RESULTS

William A. Leasure, Jr. and

Denzil E. Mathews

Applied Acoustics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standard^

Washington, D. C. 20234

January 1974

Final Report

Prepared for Office of Noise Anatement

U. S. Department of Transportation

Washington, D. C. 20590

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

NATIONAL BUREAU OF STANPARDS, Richard W. Roberts, Director
(

I

1

I

i
Pecos Truck Tire Noise Study:

A Summary of Results

by

William A. Leasure, Jr. and Denzil E. Mathews

Applied Acoustics Section

Mechanics Division

Abstract

The Society of Automotive Engineers, Inc. (SAE) Truck Tire

Noise Subcommittee conducted a series of truck tire noise tests at

the Automotive Proving Grounds, Inc. in Pecos, Texas, November 5-7,

1973. At the request of DOT, NBS participated in these tests and

made simultaneous measurements with those made by the SAE committee.

This report presents a summary of the results obtained during these

tests.

Key Words: Acoustics; noise measurement; noise (sound); tire noise;

transportation noise; trucks

PECOS TEST RESULTS

In order to address two questions concerning SAE Recommended Practice J-37 — Sound Level of Highway Truck Tires, the SAE Truck Tire

Noise Subcommittee conducted a series of truck tire noise tests at the

Automotive Proving Grounds in Pecos, Texas, November 5-7, 1973. The

tests were designed (1) to clarify the effect of the test surface on

the results obtained utilizing J-57 and (2) to determine if the height

of the truck bed above the tires significantly influences the results.

The standard now specifies a 5+1 inch clearance between the bed and the

tires. At the request of DOT, NBS participated in these series of tests

and made simultaneous measurements with those made by the SAE Committee.

The original test matrix called for the testing of six tire types

[three rib tires (rib-i, rib-2 and rib-3) and three cross-bar

tires (cross-bar-1, cross-bar-2 and cross-bar-3]

while running over four concrete pavements representing various surface

textures (surface finishes) — smooth, brushed, sand blasted brushed,

and terrazzo finished concrete. All test tires were mounted in dual

pairs on the drive axle of a 1973 CMC Astro 95 tractor. The tires were

inflated as per Tire and Rim Association recommendations and the vehicle

was loaded such that maximum rated tire load was achieved. Neutral rib

tires were mounted on the steering axle of the vehicle. As per J-57,

all runs were at 50 mph, all measurements were taken at 50 feet with a

minimum of three repeat runs for any given set of test conditions.

In addition, the two selected cross-bar tires were tested at 60 mph

while running on the smooth and sand blasted brushed concrete surfaces.
Since time was still available, after the tests in the initial

matrix had been accomplished, it was decided to run the cross-bar tires

on two additional surfaces — (1) asphalt and (2) dorset pebble.

Also, some runs were made with neutral rib tires at all wheel positions

except two; cross-bar-1 tires were mounted at the right outside

and right inside locations. This is similar to the mix-and match

studies run during the DOT/NBS work.

For the bed height studies, a Ford single-chassis, flat-bed vehicle

was utilized as the test truck. Tests were run with the standard bed

location and with the bed raised above its normal position. The

truck was equipped with cross-bar-3 and cross-bar-2 tires and ran on

sand blasted brushed and brushed concrete surfaces. NBS felt that

the bed height would not be a problem since the effective source

height of tire-road interaction noise is very near the tire-road

Interface; therefore, we made no measurements during the runs associated

with the bed height investigation.

NBS otherwise made simultaneous measurements with those made

by the SAE Committee; the major difference between the data being that

SAE tape recorded the data and took on-the-spot A-weighted slow response sound level readings utilizing a B&K 2606 measuring amplifier

while NBS made no on-the-spot readings but tape recorded the passbys

utilizing the data acquisition system shown in Figure 1. The tapes were

Figure 1. NBS data acquisition system.

MICROPHONE

B&K 4145

(MODIFIED)

SOUND LEVEL

METER

B&K 2204

TAPE

RECORDER

NAGRA

2
returned to NBS for reduction and analysis. All passbys were analyzed

to determine the A-weighted sound level that would be read utilizing

both "fast" and "slow" meter ballistic characteristics of a sound level

meter. These data are tabulated in Appendix A along with the SAE data.

The reduction and analysis instrumentation are shown in Figure 2.

oo CZ3 • •

TAPE MEASURING SOUND LEVEL

RECORDER AMPLIFIER METER

NAGRA B&K 2606 B&K 2204

Figure 2. NBS data reduction and analysis system.

To provide some indication of the agreement between the SAE and NBS

A-weighted, slow response sound level data a histogram showing L slow

(SA.E)-L^ slow (NBS) [Figure 3] was developed. It should be noted that

there was good agreement between the SAE and NBS slow response data.

For 80% of the runs the agreement was within IdB; while for 95% of the

runs the two sets of data agreed within 1.5dB. The distribution was

not Gaussian but appeared to be biased slightly to the high side, i.e.,

in general the SAE data would tend to be higher rather than lower than

the NBS data.

A second histogram [Figure 4] was plotted to provide an indication

of the differences one could expect to observe between data taken

utilizing the "slow" and "fast" meter ballistic characteristics (based

on the NBS data). Based on these data ( L^ f ast - L^ slow), one would expect

that approximately 60% of the time the difference would be on the order of
16.

§ 14h

^ 121- w

S 10-

4

2.

-2.0 -1.0 0.0 +1.0 +2.0

DIFFERENCE, dB

Figure 3. Histogram showing

L slow (SAE) - slow (NBS)for

a total of 80

identical runs.

26

24

22

20

18

16

w 14

>

0 12

OSw

1

10

8

6-

4

2-

0.0 +0.5 +1.0 +1.5 +2.0 +2.5

DIFFERENCE, dB

Figure 4. Histogram showing

L fast (NBS) - slow (NBS) for

a total of 80

identical runs.

4
1.0-1. 5dB; however, differences as great as 2.5dB were noted. To further

investigate the meter response question, two additional plots were

developed [Figures 5 and 6] to see if the differences one observes between the slow and fast response are constant for both rib and cross-bar

type tires. From these data one can conclude that in general larger

differences will be observed for cross bar-type tires but that the

largest difference was observed for the rib-type tires. The distribution

for the rib-type tires is nearly Gaussian while the distribution for the

cross-bar-type tires is biased toward the greater differences.

16

14

^12

H

W

wlO

o

Qi 8

w

Q

4-

2-

0.0 +0.5+1.0+1.5+2.0+2.5

DIFFERENCE, dB

16

14

^ 12

>

^ 10

fao

0.0 +0.5 +1.0 +1.5 +2.0

DIFFERENCE, dB

Figure 5. Histogram showing

L fast (NBS) - slow (NBS) for a total of 43 identical runs with the truck equipped with

rib type test tires.

Figure 6. Histogram showing

L fast (NBS) - slow (NBS) for a total of 37 identical

runs with the truck

equipped with cross- bar type test tires.

5
In order to further emphasize the problem existing with the response

of commercial precision equipment to transient signals, two sets of

test runs (the three repeat runs for rib-3 and cross-bar-3

tires on the smooth concrete surface at a vehicle speed of 50 mph) were

selected for further analysis. In addition to the B & K 2204 sound level

meter, a B & K 3347 real-time, 1/3-octave analyzer set for fast random

and slow random response and a B & K 2305 graphic level recorder set up

for slow and fast response according to the specifications described in

the B & K manual for the 2305 graphic level recorder were used. In

addition, a second set of graphic level recorder settings were utilized.

The second set was that recommended by Jerry Donavan and Tom Ketcham of

B & K Instruments in their recent article in the October 1973 issue of

Sound and Vibration entitled "Transportation Noise - It's Measurement and

Analysis." The major difference between the two recommendations concerns

the writing speed chosen. The B & K manual specifies a writing speed

of 16mm/sec for slow response and lOOmm/sec for fast response. The

Donavan/Ketcham article on the other hand recommends a writing speed of

200mm/sec for slow response and 315mm/sec for fast response. The results are tabulated below. What these data show, of course, is the

problem that exists among precision instruments concerning their response

to transient signals. It is an area that is not covered well by the

existing standards. These data are shown here as a cautionary measure,

since it is our understanding that each participant of the Pecos test will

receive a duplicate set of data tapes for further analysis. Depending on

the instruments chosen for such analysis, various results can be expected.

6
RIB-3 TIRES

SAE

NBS

SLM

NBS

RTA

NBS

GLR

X1 fi\J mmHull / Gpr* 1 O

NBS

GLR

900 mm/ spr

67.0 68.0 67.0 69.0 70.0

67.0 68.0 67.0 69.0 70.0

67.0 68.5 67.0 70.0 70.0

"SLOW"

NBS NBS NBS/GLR NBS/GLR

SLM RTA lOOnra/sec 315nun/sec

69.0 68.0 71.0 70.7

69.0 68.0 72.0 71.0

69.0 68.0 72.0 71.0

"FAST'

CROSS-BAR-3 TIRES

SAE

NBS

SLM

NBS

RTA

NBS/GLR

16nrni/ sec NBS/GLR

200mm/sec

80.5 CO.O 7o.O 82.0 31.5

79.5 78.0 76.0 79.0 81.5

79.5 78.5 77.0 80.0 80.5

"SLOW"

NBS NBS NBS/GLR NBS/GLR

SLM RTA lOOnun/ sec 315inm/sec

81.5 81.0 83.0 82.0

80.0 81.0 84.0 82.5

80.0 79.0 83.0 31.5

"FAST"
Results that have been obtained to date in controlled test programs

exploring the variation in noise level produced by truck tires while

running on surfaces with varying degrees of surface roughness indicate

that the noise generated by cross-bar type tires is relatively unaffected

by the surface roughness while the characteristic noise of rib-type tires

generally increases slightly with increasing surface roughness. These trends

are further substantiated by the Pecos study as shown in Figure 7.

o

w

>

O

cnw

H

I

80

75 -

70

65 -

A

O

o

A

A

O

CROSS-BAR

O

RIB

« RIB-1

«• RIB-2

A RIB3

O CROSS-BAR-1

ca CROSS-BAR-2

A CROSS-BAR3

o w

O Pi

IS O

o

a

o o w

N W H

Nl 33 U

<: M

« M O

3 z z W M O

H PtH U

w

a H

pa w

33 Pi

ai o

Q

W

H W

CO w H

W

PQ a § z

O o

o

Figure 7. A-weighted, slow response sound level as per SAE J-57 versus surface finish based on the SAE COMMITTEE DATA.

n
APPENDIX A

SAE/NBS DATA COMPILATION

In this Appendix are tabulated the SAE A-weighted (slow response)

sound level results as well as the comparable NBS results utilizing

both the slow and fast meter ballistic characteristics. The average

for each passby as well as the J-57 value (average at the highest two

runs) are also tabulated.

9
Brushed Concrete Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

- La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

73.5 73.5 74.0 75.0 75.0 77.0 72.0 72.0 74.0 74.0 73.0 73.5

74.0 74.0 75.0 74.7 75.0 77.0 71.0 71.5 72.5 72.5 72.0 73.5

75.5 75.0 76.0 75.0 75.0 76.5 72.5 72.5 75.0 73.0 72.0 74.0

74.0 74.0 74.5

Avg. 74.2 74.1 74.9 74.9 75.0 76.8 71.8 72.0 73.8 73.2 72.3 73.7

J-57 Ih.l 74.5 75.5 75.0 75.0 77.0 72.2 72.2 74.5 73.5 72.5 73.7

RIB-2

Brushed Concrete Sand Blasted Smooth Concrete Terrazzo

Brushed Concrete Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

72.0 72.0 73.5 73.5 74.0 75.0 70.0 71.5 71.5 71.5 71.5 73.0

73.0 73.5 74.0 73.0 73.5 74.0 70.0 70.5 71.5 71.5 72.0 73.0

72.5 72.5 73.0 73.0 73.0 74.0 70.0 70.5 71.5 72.0 72.0 73.5

73.0 72.0 72.0 73.0

Avg. 72.5 72.7 73.5 73.1 73.5 74.3 70.0 70.8 71.5 71.7 71.9 73.1

J-57 72.7 73.0 73.7 73.2 73.7 74.5 70.0 71.0 71.5 72.0 72.0 73.2

10
50 MPH

CROSS-BAR-1

Brushed Concrete Sand Blasted

Brushed Concrete

Smooth Concrete Terrazzo

Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fa s t LaSlow

La La

Slow Fast

La

Slow

La

Slow

La

Fast

71.5 76.0 77.0 78.0 77.0 77.5 78.0 77.0 78.5 78.5 77.5 77.5

78.0 77.0 78.5 77.5 76.5 77.5 78.0 77.0 78.5 73.5 77.5 79.0

77.5 76.5 78.0 78.0 77.0 78.0 78.0 76.5 77.5 78.0 76.5 ..77.0

79.0 77.0 78.0

78.0 76.0 76.0

Avg. 77.7 76.5 77.8 77.3 76.3 77.7 78.0 76.3 78.2 78.4 76.9 77.5

J-57 77.7 76.7 78.2 78.0 77.0 77.7 78.0 77.0 73.5 78.5 77.5 78.5

CROSS-BAR-2

Brushed Concrete Sand Blasted Smooth Concrete Terrazzo

Brushed Concrete Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

80.5 30.0 81.0 80.5 80.0 81.0 80.0 79.0 79.5 80.5 79.0 80.0

79.5 79.0 79.0 81.0 30.5 82.5 79.5 79.0 81.0 30.5 78.5 80.0

79.5 79.0 80.0 79.5 79.5 80.0 80.5 80.0 80.0 80.5

Avg. 79.8 79.3 30.0 80.3 80.0 81.2 80.0 79.3 80.1 80.5 78.7 30.0

J-57 80.0 79.5 30.5 80.7 80.2 81.7 80.2 79.5 80.5 80.5 78.7 80.0

11
50 MPH

CROSS-BAR-3

Brushed Concrete Sand Blasted

Brushed Concrete

Smooth Concrete Terrazzo

Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

78.5 79.0 80.0 78.0 77.0 78.5 80.5 80.0 81.5 80.0 80.0 81.0

78.5 78.5 30.0 79.0 79.0 81.0 79.5 78.0 80.0 80.0 80.0 81.5

78.0 77.5 79.0 78.5 78.0 80.0 79.5 78.5 80.0 80.0 79.5 81.0

Avg. 78.3 78.3 79.7 78.5 78.0 79.8 79.8 78.8 80.5 80.0 79.8 81.2

J-57 78.5 78.7 80.0 78.7 78.5 80.5 80.0 79.2 80.7 80.0 80.0 81.2

Brushed Concrete Sand Blasted Smooth Concrete Terrazzo

Brushed Concrete Finished Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

71.0 73.0 74.0 71.5 72.5 73.5 67.0 68.0 69.0 68.5 68.5 69.0

72.5 74.0 75.0 72.5 74.0 75.5 67.0 68.0 68.0 69.0 68.5 70.0

71.0 72.5 73.0 71.5 72.5 73.5 67.0 68.5 69.0 68.0 67.5 68.0

72.5 74.0 74.5 72.5 74.0 75.0 69.5 68.5 70.5

72.0 73.0 74,0

72.5 74.0 74.0

Avg. 71.9 73.4 74.1 72.0 73.2 74.4 67.0 68.2 68.7 68.7 68.2 69.4

J-57 72.5 74.0 74.7 72.5 74.0 75.2 67.0 68.2 69.0 69.2 68.5 70.2

12
60 MPH

CROSS-BAR-2 CROSS-BAR-3

Smooth Concrete Sand Blasted

Brushed Concrete

Smooth Concrete Sand Blasted

Brushed Concrete

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

32.0 81.5 82.0 83.0 83.0 85.0 81.5 81.0 84.0 81.0 80.5 82.0

32.2 81.5 82.5 82.0 82.0 83.0 82.0 81.0 83.0 80.0 79.5 79.5

32.0 81.5 83.0 83.0 82.5 84.0 82.0 81.5 83.5 81.0 80.0 81.0

Avg. 82.2 81.5 82.5 82.7 82.5 84.0 81.8 81.2 83.5 30.7 80.0 80.5

J-57 82.1 81.5 82.7 83.0 82.7 84.5 82.0 81.2 83.7 81.0 80.2 81.5

RIB3

CROSS-BAR-1

Terrazzo

Finished Concrete

Smooth Concrete

SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

77.0 74.5 75.0 77.5 76.0 76.5

75.0 74.5 76.0 75.5 74.0 75.5

77.0 77.0 77.5 77.5 76.5 77.5

75.0 74.5 76.0 75.5 74.5 76.0

13
50 MPH

CROSS-BAR-1 CROSS-BAR-3

Asphalt Dorset

Pebble

Asphalt Dorset

Pebble

SAE NBS SAE NBS SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

SloXvT La

Fast

La

Sl0Xi7 LaSlow

La

Fact

La

Slow

La

Slow

La

Fast

77.5 78.0 77.5 79.0 77.0 76.5 77.0 78.5 77.5 78.0

78.0 77.0 78.5 78.5 78.0 78.5 77.0 * * 78.5

78.0 77.0 79.5 78.5 77.5 78.5 78.0 * * 78.5 77.5 78.0

79.0 78.0 78.5 77.5 *

Avg 77.8 77.0 78.7 78.5 77.8 78.6 77.4 78.5 77.5 78.0

J-57 78.0 77.0 78.7 78.7 78.0 78.7 77.7 78.5 77.5 78.0

CROSS-BAR-2

Asphalt Dorset

Pebble

SAE NBS SAE NBS

La

Slow

La

Slow

La

Fast

La

Slow

La

Slow

La

Fast

79.0 J. 78.5 * A

79.5 78.5 * *

79.5 78.5 A *

Avg. 79.2 78.5

J-57 79.5 78.5

*WINDS TOO HIGH FOR RECORDING

ON LINEAR.

14
NBS-IUA (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATlOiN' OH Ri:PORT NO. NBSIR 74-446

2. Gov't Accession

No.

3. Recipient's Acces.'sion No.

4. TITLK AND SLBl ITLH Pecos Truck Tire Noise Study: A Summary of Results

5. Publication Date January 1974

6. Performing Organization Code

7. AUTHOR(S)

William A. Leasure> Jr. and Denzil E. Mathews

8. Performing Organ. Report No. NBSIR 74-446

9, PKRFOR.MING ORGANIZATION NAME AND ADDRICSS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No.

11. Contract/Grant No.

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

Department of Transportation

Office of the Secretary

Office of Noise Abatement

" — " N

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLE.MENTAR^ NOTE.S

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

bibliography or literature survey, mention it here.) The Society of Automotive Engineers, Inc. (SAE) Truck Tire Noise Subcommittee

conducted a series of truck tire noise tests at the Automotive Proving Grounds,

Inc. in Pecos, Texas, November 5-7, 1973. At the request of DOT, NBS participated

in these tests and made simultaneous measurements with those made by the SAE

committee. This report presents a summary of the results obtained during these

tests.

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) ; tire noise; transportation noise;

trucks

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