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
-4.1
-2.7
-3.6-3.4
-1.4 -1.4
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
Ave
rage
Lm
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
20
30
40
50
60
70
80
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
20
30
40
50
60
70
80
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
30.0
40.0
50.0
60.0
70.0
80.0
90.0
0 200 400 600 800 1000 1200 1400 1600
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
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
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)
10
20
30
40
50
60
70
80
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
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
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
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
0
2
4
6
8
10
12
0 50 100 150 200 250 300
Distance (ft)
Pave
men
t ben
efit
(dB
A)
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
Site 3ASite 3BSite 3CSite 3DSite 3E
Spectral Examination of Site 3C Data
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
10 100 1000 10000
Frequency (Hz)
Ban
d le
vel,
aver
age
LAeq
5min
(dB
(A))
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xx
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