Over the last several years, highway pavement rehabilitation projects have incorporated open-graded asphalt, also referred to as "popcorn pavement" for its skid-resistant properties. Subjective observations have noted a decrease in overall noise levels in areas where popcorn pavement has been used. The results are presented of a field testing program conducted in June 1989 along the Baltimore Beltway (I-695) to determine the difference in the overall noise level from typical highway traffic travelling on concrete versus open-graded asphalt pavement. Noise levels were measured simultaneously adjacent to the concrete and asphalt surfaces to determine the difference in noise level, and classified traffic counts were made to determine the effect of truck percentage in the traffic stream on the overall noise reduction attributable to the open-graded pavement. An analysis of the third-octave band frequency spectrum for traffic on the concrete and open-graded asphalt is also presented. The results showed a consistent 2- to 4-dBA reduction in the overall L sub eq that could be attributed to the open-graded pavement. In the higher-frequency bands, 1,000 to 5,000 Hz, the third-octave band analysis showed a significant reduction (2 to 4 dB at 1,000 Hz to 6 to 7 dB at 2,000 to 4,000 Hz). Future studies are planned to expand the baseline data to include other ages and types of concrete and asphalt surfaces, as well as to determine whether ageing of the pavement affects its noise reduction capacity.
Samenvatting