A tentative criterion for acceptable noise levels in passenger vehicles

Abstract

Whilst a tremendous amount of work has been published in recent years on criteria for acceptable noise from motor vehicles very little work has been reported on the noise climate inside the vehicle. As a consequence there is no criterion for acceptable noise levels inside either passenger or goods vehicles. This paper describes the results of the measurement of noise inside a variety of passenger vehicles over the frequency range 2 Hz–16 kHz and an attempt to find a satisfactory measure of subjective response. It is shown that the noise has characteristically greatest energy below 20 Hz (in the infrasonic range) and that this produces a different sort of subjective reaction to that of external vehicle noise. The existing subjective rating procedures of dB(A), NR, PLdB, etc., are shown to have severe limitations for predicting subjective response for vehicle interior noise. Much work needs to be done to produce a more satisfactory measure of subjective acceptability. But in the interim the following criteria based upon noise levels measured on the dB(A) scale is proposed:∗∗Criterion for noise in vehiclesNoise level not exceedingSubjective rating(dB(A))Quiet67Noticeable73Intrusive79Annoying85Very annoying91