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Effect of Diamond Grinding on Noise Characteristics of Concrete Pavements in California

The construction of sound walls along highways has been the primary noise mitigation strategy in California and in many other western States. Sound walls cost approximately $1.5 million per mile and are effective only in close proximity to the highway, on the “far” side of the sound wall, so to speak. In its efforts to explore other noise mitigation strategies, the California Department of Transportation (Caltrans) recently conducted a study to determine the effect of diamond grinding on the noise characteristics of existing concrete pavements. Since the noise generated at the tire– pavement interface is the greatest contributor to highway noise, quieter pavement surfaces can reduce overall noise levels for both road users and neighborhoods—whether sound walls are used or not. On-board sound intensity (OBSI) measurements were conducted on six routes in California, for a total of 42 evaluation sections; each evaluation section was 440 ft (136.8 m) long. OBSI measurements before and after diamond grinding were recorded. Following are the overall conclusions that were reached after the pre- and post-grinding OBSI levels were measured: (1) There is a significant and readily audible reduction in OBSI levels (and hence in tire–pavement noise) after grinding. (2) An average 2.7 dBA reduction in OBSI levels was observed for all test sites. (3) Among the six routes, the highest average reduction of 4.4 dBA was observed on I-5 near Richards Boulevard in Sacramento County, and the lowest reduction of 1.2 dBA was observed on State Route 60 (on a single test section) in San Bernardino County. (4) The highest reductions in sound intensity levels on a 1/3-octave band basis occurred in the 1600 Hz band, while the lowest reductions occurred in the 1000 Hz bandwidth.