Description
The California Department of Transportation has been conducting preliminary field tests of a new procedure for quickly and accurately assessing the noise characteristics of various pavement surfaces in-situ, on board a vehicle operating at freeway speeds. This new process is physically simpler but more acoustically complex than existing pavement noise evaluation techniques. The approach is based on sound intensity, a vector quantity, while the established acoustical procedures measure sound pressure, a scalar quantity. The sound intensity approach is
highly selective and directional and this allows measurement of just the tire/pavement noise-at the exclusion all other surrounding noise sources. On passenger cars, the relationship between the on-board near field sound intensity measurements adjacent to the tire/pavement interface is highly correlated with the far field roadside sound pressure noise levels.
The findings from the study showed that as a group, PCC surfaces were found to produce higher noise levels than AC surfaces. Of the highway pavements tested, those asphalt surfaces that were open graded, rubberized, or both, produced the lowest noise levels.
