In the United States, much has been learned about pavement acoustics in the past eight years with the development of the On-Board-Sound-Intensity (OBSI) measurement methodology. OBSI allows researchers to examine pavementacoustics in great detail, and most understanding of pavement noise generating mechanisms is that it occurs at the mega and macro texture levels. A demonstration project provided the opportunity to examine how tire/pavement noise levels could be influenced with changes in microscopic surface texture on both flexible and rigid pavements. The OBSI spectral measurements provided additional insight on how the shot peening process (Skidabrader® or skidabrading) altered the pavement surfaces. Overall A-weighted noiselevels were not significantly changed by shot peening, but there were slight increases in the flexible pavements, and slight decreases in the rigidpavements. Spectral shifts in low and high frequencies were observed and the magnitude of the shifts varied between the flexible and rigid pavements. At frequencies below 1000 Hz, the shot peening raised the one third octave band levels. At frequencies of 1600 Hz and greater, shot peening consistently lowered the one third octave band level. The process removed fine surface material and exposed larger aggregates which increased macrotexture depth and greatly improved friction, but generated more low frequency noise. This increase in low frequency tire/pavement noise was compensated by a reduction in high frequency noise. Pairing the acoustic data with thefriction data implies that improving microscopic texture reduces high frequency noise.
Abstract