Volpe Center Updates on Tire/Pavement Noise Studies

Judith L. Rochat, Ph.D. U.S. DOTVolpe Center Acoustics FacilityEnvironmental Measurement and Modeling

TRB ADC40 Summer MeetingWilliamsburg, VAJuly 2006

Outline

Variability of pavement noise benefit by vehicle type

Caltrans LA 138 study

Pavement effects as a function of distanceFHWA Traffic Noise Model® (TNM) analysisADOT QPPP data

Current FHWA / Volpe projects

VARIABILITY OF PAVEMENT NOISE BENEFITBY VEHICLE TYPE

LA 138 Quiet Pavement Study

Asphalt Concrete (AC) study funded by Caltrans

Primary sponsors:Bruce RymerJim Andrews

LA 138 AC Pavement Study Location

LA 138

~4 mi (6.4 km) relatively flat desert area

~80 mi (~130 km) north of Los Angeles, CA

Study Overview

Long-term study examining 5 asphalt pavements for durability, safety, and noise

Wayside MeasurementsSide of highway measurements at multiple distances and heights applying the Statistical Pass-By Method

Source Measurements (Illingworth & Rodkin)On-Board Sound Intensity measurements at the tire

AnalysisCompare reference and test sections over timeObserve degradation of individual sections over time

Pavement Sections

Five Pavement TypesS1 – Dense-Graded Asphalt Concrete (DGAC)S2 – Open-Graded Asphalt Concrete (OGAC) 75 mm thicknessS3 – Open-Graded Asphalt Concrete (OGAC) 30 mm thicknessS4 – Rubberized Asphalt Concrete Type O (RAC type O)S5 – Bonded Wearing Course (BWC)

Section 2(75mm OGAC)

Section 1(30mm DGAC)

Section 3(30mm OGAC)

Section 4(30mm RAC)

Section 5(30mm BWC)

Wayside Measurements – instrumentation diagram

1

2

1

2

1 = 1 microphone at 5-ft height; on tripod

2= 1 person + incident log= 1 video camera;

on tripod

= 2 microphones, 1 at 5-ft height and 1 at 15-ft height; on 2 tripods

= 1 met sensor at 5-ft height; on tripod

Caltrans Pavement Study: full set-up

25 ft ___

50 ft ___

200 ft ___

100 ft ___

75 ft ___

1

2

1

Section 2(chosen section; 75mm OGAC)

22

Section 1(reference; DGAC)

Section 3(30mm OGAC)

Section 4(30mm RAC)

Section 5(30mm BWC)

11 1

Wayside Measurements – instrumentation

Data Collection

Baseline measurements (March 2002)Leveling course (DGAC in all sections) completed in December 2001Allows for the determination of site bias

Subsequent measurements (with pavement overlays)October 2002 – pavement aged ~4 months March 2003 – pavement aged ~10 monthsOctober 2003 – pavement aged ~16 monthsPlanned for October 2006 – pavement aged ~ 52 months

Data Analysis (part 1)

Modified Statistical Pass-By Method (ISO 11819-1)Accounts for autos, medium trucks, and heavy trucksCalculate Lveh as average Lmax (dBA) for each vehicle type

Broadband paired pavement analysisCompares each of the quieter pavements to DGAC:

DGAC and 75mm OGACDGAC and 30mm OGACDGAC and RAC

Identical vehicle sets for paired dataAccounts for site biasWill show paired noise reduction deltas for autos and heavy trucks (HT)

Results – broadband noise reduction by vehicle type

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-2.7

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-1.0

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Ave

rage

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ax D

elta

, Site

x -

Site

1 (

dBA

)

OGAC 75 mm, Site 2 OGAC 30 mm, Site 3 RAC type O 30 mm, Site 4

0.0 auto HT auto HTauto HT

(comparing each of the quieter pavements to DGAC, 25 ft from road)

Results – broadband observations

For the pavements tested in this study …

Quieter pavements provide a greater reduction for auto noise than heavy truck noise

Increasing the thickness of OGAC overlay provides additional benefit for both autos and heavy trucks

With the same thickness, RAC provides additional benefit over OGAC for autos

Data Analysis (part 2)

Spectral “paired” pavement analysisDirectly compares four pavements:

DGAC, 75mm OGAC, 30mm OGAC, RACIdentical vehicle set for all sitesDoes not account for site bias (too few baseline events)Will show average measured levels for autos and heavy trucks (HT)

Results for Autos – spectral data by pavement type

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10 100 1000 10000

Frequency (Hz)

Ave

rage

Lm

ax 1

/3-o

ctav

e ba

nd le

vels

(dB

A DGAC

OGAC 75mm

OGAC 30mm

RAC 30mm

(25 ft from road)

Results for Heavy Trucks – spectral data by pavement type

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30

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10 100 1000 10000

Frequency (Hz)

Ave

rage

Lm

ax 1

/3-o

ctav

e ba

nd le

vels

(dB

A DGAC

OGAC 75mm

OGAC 30mm

RAC 30mm

(25 ft from road)

Results – spectral observations

For the pavements tested in this study …

Quieter pavements provide noise reduction in a critical range around 1 kHz

Reduction range is more beneficial to autos than heavy trucks due to energy distribution

Increasing the thickness of OGAC overlay provides additional benefit for frequencies ≥ 1 kHz for both autos and heavy trucks

With the same thickness, RAC provides additional benefit over OGAC at 1 kHz for both autos and heavy trucks

LA 138 AC Study Observations

Applying quieter pavement overlays can reduce wayside-measured sound levels

Amount of noise reduction due to pavement is vehicle-type dependent

Longevity of noise reduction has yet to be determined

Compared to DGAC …OGAC 75 mm provided greatest noise reduction (~3-4 dBA)

Noticeably more reduction than thinner overlays at frequencies ≥ 1 kHz

OGAC 30 mm and RAC also provided noise reductionRubberized provided extra reduction at some critical frequencies (~1 dBA for autos)

Each of the quieter pavements provided greater noise reduction for autos than for heavy trucks

To further reduce heavy truck noise, pavements should be designed to reduce noise at 500 Hz

PAVEMENT EFFECTS AS A FUNCTION OF DISTANCE

FHWA TNM® Predictions

Used TNM v2.5 to model flat, open site with mixed trafficReceivers at multiple distances2 types of roadway pavements: louder and quieter (part of noise emission database in TNM)2 types of sites adjacent to road: acoustically hard and soft ground (soft is more sound absorptive)

Calculated results on a 1/3-octave band basis

Sound Pressure Level over Distance

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Distance (ft)

TNM

-pre

dict

edLA

eq1h

(dB

A)

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xx

louder pavement, hard ground

quieter pavement, hard ground

louder pavement, soft ground

quieter pavement, soft ground

Effect of Pavement over Distance

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0.5

1.0

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3.0

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0 200 400 600 800 1000 1200 1400 1600

Distance (ft)

TNM

-pre

dict

edno

ise

redu

ctio

n (d

BA

) xx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

noise reduction, hard gorund

noise reduction, soft ground

Spectral Examination at 3 Distances (soft ground)

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10 100 1000 10000

Frequency (Hz)

TNM

-pre

dict

ed1/

3-oc

tave

ban

d le

vels

(dB

A)

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

xx

louder @ 50 ft, 76.8 dBAquieter @ 50 ft, 73.7 dBAlouder @ 500 ft, 55.1 dBAquieter @ 500 ft, 52.9 dBAlouder @ 1000 ft, 47.9 dBAquieter @ 1000 ft, 47.0 dBA

Additional TNM PredictionsAdded noise barrier to site

Elevated road 10 ft

Depressed road 10 ft

Effect of Pavement over Distance – 4 site types, soft ground

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Distance (ft)

TNM

-pre

dict

edno

ise

redu

ctio

n (d

BA

) xx

xxxx

xxxx

xxxx

xxxx

xxxx

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xxxx

flat open site

barrier site

10 ft elevated road

10 ft depressed road

TNM Predictions – Observations

The effect of pavement on noise levels is …Distance dependentSite dependent

Ground type, intervening objects, and site geometry will affect the noise reduction due to pavement

For predicting sound levels, the effect of pavement should be accounted for at or near the source to allow for propagation effects

At farther distances, low frequencies …… are contributing more to overall sound level… are affected very little by pavement type

ADOT QPPP

Study to evaluate the effectiveness of quiet pavement (ARFC), funded by ADOT

Primary sponsors:Christ Dimitroplos (ATRC)Mike Dennis

ADOT QPPP Data

Wayside time-averaged data at Type 3 sitesCollected continuously with free-flowing trafficPre-overlay: transversely tined PCC (variation by site)Post-overlay: ARFC (rubberized asphalt)

Benefit of ARFC over Distance

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0 50 100 150 200 250 300

Distance (ft)

Pave

men

t ben

efit

(dB

A)

xxxx

xxxx

xxxx

xxxx

xxxx

xxxx

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xxxx

Site 3ASite 3BSite 3CSite 3DSite 3E

Spectral Examination of Site 3C Data

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d le

vel,

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age

LAeq

5min

(dB

(A))

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50 ft, PCC, 83.2 dBA 50 ft, ARFC, 74.4 dBA141 ft, PCC, 72.6 dBA141 ft, ARFC, 66.0 dBA

ADOT Data Observations

There is variation of pavement noise benefit over area adjacent to highways

General trend: less benefit with increasing distance from road (there are exceptions)

At farther distances, low frequencies …… are contributing more to overall sound level… are affected very little by pavement type

Summary

It is extremely important to examine the noise benefit of pavements in terms of autos and heavy trucks

“Turning down the volume” at the source does not equate to the same “volume adjustment” throughout an area adjacent to a highway

These types of examinations will help us to understand how communities adjacent to highways are affected by pavement type

Investigate the implementation of pavement effects into TNM (funded by FHWA Pavements, Mark Swanlund)

Trial adjustment of tire/pavement source noise using OBSI data

Trial addition to vehicle noise database using “REMEL light” data (data for various pavement types)

Current FHWA / Volpe Projects

Effective flow resistivity (EFR) measurements – determining sensitivity to pavements

Accounting for change in source noise – investigating possibilities