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A measurement program was completed to assess driver input versus exterior noise generation for four vehicle designs and two different rumble strip designs. The vehicles included a small compact car, an immediate size car, a full sport utility vehicle, and a medium duty dump truck. The first rumble strip was a conventional design providing shorter wavelength input to the tire. The second was designed to provide longer wavelength, more harmonic input to the tire. The measurements included exterior pass-by noise and on-board exterior noise and interior measurements of sound pressure level and vibration level at the seat track and steering column. In general, the results indicated that the longer wavelength strips produced less overall A-weighted pass-by noise with little or no reduction in interior noise and vibration.

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.