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With the growing recognition that pavement selection can be an effective traffic noise abatement tool, there has been increased need for developing methods to characterize tire/road noise generation for existing and experimental highway surfaces. To address this need, sound intensity measured on-board a test vehicle has been developed as an alternative technique to wayside, passby, or trailer methods. As part of this development, the relationship between sound intensity measured close to a moving tire contact patch and coastby sound pressure data measured at stationary point 7.5 meters away has been demonstrated for different tires and road surfaces. A protocol for sound intensity measurement on existing highways in traffic has also been developed. Using these, a library of the tire/road noise levels has been assembled for California State Highways and experimental highway test sections.

In previous literature, sound intensity has been used to quantify the strength of tire-pavement interaction noise sources very near an operating tire under non-driven, cruise conditions as measured on trailers or actual vehicles. In the current investigation, the relationship between such on-board sound intensity data and coast-by sound pressure levels measured 7.5 meters away from the centerline of vehicle travel were examined. When compared either in terms of overall A-weighted levels or 113 octave band spectra, these data demonstrate a strong correlation between the two types of measurements. Given this correlation, the sound intensity technique was then used to quantify the tire/pavement interaction noise for the driven tires of a passenger car under accelerating conditions such as those specified in the ISO 362/SAE 51470 or SAE 5986 passby noise procedures.