Heavy Truck Pass-by Noise Levels for Different Pavements and Operating Conditions

As part of a larger study to identify heavy truck noise sources, statistical pass-by measurements were made on 1,289 heavy trucks. The measurements were made at 20 sites located in California and North Carolina and represented various pavement types and truck operating conditions induced by flat, uphill, and downhill sites, as well as low speed acceleration. Logarithmic regressions of sound level verses speed were constructed for each site and compared. The slopes of level versus speed were found to vary as well as the levels at comparable speeds. Some of this variation was due to the pavements and some was due to the operating condition. Comparison to the U.S. Federal Highway Administration (FHWA) truck pass-by database indicated that individual sites varied in level and gradient from the database. When the data from all level and downhill sites were regressed as one data set, they compared favorably to the FHWA cruise results. When the uphill data were regressed as one data set, they compared favorably to the FHWA interrupted flow data. The results of this analysis and comparison of some spectral data of interest are presented.