Comparison of Vehicle Responses to Rumble Strip Inputs of Varying Design

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. Considerable variation in the response of the vehicles was found particularly for steering column vibration and interior noise where the overall differences ranged from about 9 to 17 decibels (dB). The exterior measures produced smaller ranges, from 2 to about 71/2 dB; however, the rank ordering of vehicle response was different for the pass-by and exterior on-board results. It was concluded that the interior noise and steering column responses were strongly influenced by vehicle specific characteristics both in terms of isolation and modal response. The results of this study are presented in overall and in. octave band levels that compare the different test vehicles and test rumble strips.