Correlation of Noise Measurement Types in the Arizona Quiet Pavement Pilot Program

Abstract

In cooperation with FHWA, the Arizona Department of Transportation initiated a program to reduce highway traffic noise in the Phoenix, Arizona, metropolitan area by overlaying many freeway segments constructed of transversely tined portland cement concrete pavement with an asphalt rubber friction course. The acoustic performance of this noise mitigation approach was documented with three types of measurements: tire–pavement noise source levels, short-term neighborhood noise measurements, and roadside noise measurements at research sites. Initial comparison of the noise reductions produced by the asphalt rubber friction course indicated good agreement between the Type 1 and Type 3 measurements. Reductions for the Type 2 measurements were about 3 to 4 dB lower on average than were the other two types. Almost all of the Type 2 locations had features that provided noise reduction prior to the overlay. The effect of these features on the Type 2 noise reductions were examined using a research version of the FHWA Traffic Noise Model that accounts for differences in tire–pavement noise source levels. With the use of Type 1 data and the characteristics of the Type 2 sites, it was found that when the effect of the reduced tire–pavement source strength was added to the already existing noise-reducing features, the predicted reductions were consistent with the Type 3 results. In this sense, Type 2 and Type 1 results were found to correlate with each other and, by extension, to the Type 3 results.