Noise and Vibration Studies

Quieter Pavement studies are on-going. These studies demonstrate that pavement acoustics vary with pavement parameters and these studies track how the acoustics change with time. Sometimes, acoustical differences between various types of pavements can be significant - age, environment, and traffic loads also factor into the acoustic behavior. Portions of this material have been presented in various forms at conferences such as TRB, INCE, InterNoise, and SAE during the last decade. Three different pavement acoustic measurement procedures have been developed from this work and are being drafted as AASHTO Standards: 1) Onboard Sound Intensity (OBSI) Measurement, 2) Continuous Time Integrated Measurement (CTIM), and 3) Stastical Isolated Pass-By (SIP) Measurement. Several long-term studies have recently been updated and are available for downloading :

The I-80 Davis OGAC Pavement Noise Study is the longest running quiet pavement study in the nation. This study definitively demonstrated that pavement selection can impact roadside noise levels and the acoustic benefits of quieter pavements lasts much longer than a couple of months or years. At this site an aged and worn flexible pavement was replaced with an OGAC and before and after wayside noise measurements were taken. OBSI measurements were added to the measurement series in September 2002, after the new technique was developed. The wayside measurement process would later be used as a reference to develop the AASHTO CTIM Measurement Standard. Seasonal and meteorological variations were also tracked in this lengthy, 12 Year study.

I-80 Davis OGAC Pavement Noise Study, May 2011 (2.8 MB)

This long-term study focused on acoustic characteristics of several typical flexible pavements used by Caltrans. On a relatively quiet two-lane road in the high desert, 80 miles north of downtown Los Angeles, five different pavements were placed adjacent to each other and exposed to the same traffic loads in the same environment. The pavements included a Dense Graded Asphalt Concrete (DGAC 30mm thickness), an Open Graded Asphalt Concrete (OGAC 30mm thickness), a thicker OGAC (75mm), a Rubberized Asphalt Concrete - type Open-Graded (RAC-O 30 mm thickness),and a Bonded Wearing Coarse (BWC). Noise levels were measured at the tire/pavement interface, at the roadside, and in the vehicle interior. [Notes: Caltrans has renamed some of these pavements since this project started, but this report retains the original naming convention. It has been determined that the BWC OBSI noise level was atypically higher than other BWC sites in the state.]

Eight Yr Evaluation Of The Noise Performance Of The Caltrans Asphalt Research Pavements on LA 138, June 2011 (3.0 MB)

This long-term study focused on acoustic characteristics of various rigid pavement surface textures. This test section is located on the four lane divided Mojave-58 Bypass which carries a growing amount of heavy truck traffic. This site is also in the high desert, about 40 miles from the LA-138 flexible pavement site. Several base textures were evaluated initially and then grinding and grooving variations were added and measured. Follow-up OBSI measurements were taken to monitor acoustic changes.

Initial and Long-Term Evaluation of the Tire/Pavement Noise Produced by Various PCC Surface Textures, June 2011 (1.6 MB)

European research into quieter pavements preceded work in the USA by more than a decade and their measurement equipment requires a vehicle pulling a specialized trailer. The US measurement equipment bolts to the wheel lugs and requires only a standardized test tire -- making the USA AASHTO OBSI measurement approach much less expensive and very portable. The NITE, or Noise Intensity Testing in Europe, Study was the first definitive side-by-side comparison of European and American (CA and AZ) quiet pavements - all measured with the same equipment, by the same operator, under similar operating conditions. Even though the European community had spent more time experimenting with acoustically optimized pavements, standard off-the-shelf pavements in the USA compared very favorably to European low noise pavements.

Comparative Measurements of Tire/Pavement Noise In Europe And The United States; Noise Intensity Testing in Europe (NITE) Study, July 2006 (8.6 MB)

The Volpe Center Acoustics Facility also measured the various flexible pavements at the LA-138 site. At the time of this study, Volpe conducted only Statistical Pass-By measurements (based on an ISO draft standard) and examined the effects of pavement noise relative to overall vehicle noise levels at the roadside. Volpe measured how the noise propagated from the vehicles on the road to distant receivers. The extensive data set from this study is referenced for on-going improvements to the FHWA Traffic Noise Model and used for developing the AASHTO SIP Measurement Standard.

Caltrans Thin Lift Study: Effects of Asphalt Pavements on Wayside Noise, June 2010 (3.3 MB)

Much of the knowledge from these noise studies was applied to constructing low noise pavement surfaces on the new San Francisco Oakland Bay Bridge. Both the Skyway and Oakland Touchdown portions of the bridge have used pavement textures designed to lower traffic noise levels. This is particularly beneficial for the pedestrians and cyclists using the impressive sidewalk to Yerba Buena Island. See project images below.

Images from the LA-138 test site below:

• - Noise Protocol, groundborn vibration issues/guidance, home insulation, hydroacoustics, training
• - Tire/pavement noise, bridge noise, truck noise, bioacoustics, noise protocol, TNM support, contracts