Tire Noise Generation and Propagation over Porous and Nonporous Asphalt Pavements

Abstract

Acoustic measurements were made on several asphalt test pavements at the National Center for Asphalt Technology test track, including five porous pavements. Onboard sound intensity (OBSI) measurements were taken to quantify the tire–pavement noise source strength as a function of pavement parameters. The OBSI results fell into three pavement groupings based on spectral shape. More than other parameters, these groupings were determined by whether the pavement was porous or not and whether it was new or older. The OBSI results also indicated that single-layer porous pavements were particularly effective at reducing tire–pavement noise source strength at frequencies above 1,250 Hz for designs 18 to 33 mm thick. For a thicker, double-layer porous pavement, source strength reductions extended down to 630 Hz. Porous pavements were also found to be effective in reducing the source strength of the tire–pavement interaction by reducing some tire noise mechanisms and by reducing the sound power level of the source through local sound absorption. Testing was also conducted to evaluate the additional attenuation for sound propagating over porous, sound-absorbing pavements compared with nonporous pavements. From the propagation measurements, all porous pavements produced additional sound attenuation over that produced by the nonporous pavements. The additional attenuation also increased with distance from the source.