| Summary: | Road traffic noise is becoming a major public concern. Many transportation agencies are looking for practical and economical means to reduce traffic noise generation and propagation. In 2003, the University of Waterloo’s Centre for Pavement and Transportation Technologies (CPATT) and the Regional Municipality of Waterloo embarked on a partnership to design quiet pavement test sections and to conduct controlled sound level measurement on four different types of asphalt surface courses.
Four different surface courses, two Rubberized Open Graded Friction Course Asphalt Pavements (rOFC and rOGC), Stone Mastic Asphalt Pavement (SMA), and a control mix Hot-Laid 3 (HL-3), were placed in lengths of 600 m. The overall 2.4 km test area was closed to traffic and test vehicles were driven through the test area at the prescribed control speeds with sound level meters recording sound levels both at the tire/pavement interface as well as at the monitoring stations off the roadway. Impedance Tube Method and Reverberation Time Method were performed to determine the sound absorption coefficients of the pavement mixes.
In order to evaluate the sound attenuation ability of the mixes, the results from rOFC, rOGC, and SMA were used to compare with the result from the control mix HL-3. Statistical analysis of measurement results was performed to see whether the differences between mixes are significant at a 95% confidence interval. Life cycle cost analysis was also performed in order to determine the cost effectiveness of each asphalt mix.
Results indicate that traffic sound level increases as vehicle speed and size increase regardless of asphalt types. rOFC and rOGC perform significantly better than HL-3, but the performance slightly deteriorate after one year because of the clogging problem. SMA does not attenuate sound as effectively when compare to HL-3 at the early age. However, sound attenuation ability improves after one year of service. Overall result indicates that rOGC performs the best among all mixes in terms of the sound attenuation ability. Life cycle cost analysis shows that HL-3 is the most economical mix but it is the worst mix in terms of sound attenuation ability.
It is recommended to conduct additional sound level and skid resistance measurements in the future to monitor the long-term pavement performance. Also investigation of the relationship between the sound level and sound absorption coefficient measurements is beneficial for the future acoustical evaluation for the asphalt mix.
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