Kurtosis measurements: Implications for noise exposure criteria

Two conventional measures of an industrial noise environment are the overall sound‐pressure level (SPL) and the power spectrum. While these two measures are necessary, they may not be sufficient to describe a noise environment for the purposes of evaluating the hazard to hearing. This presentation will describe the results of an experiment designed to test the hypothesis that for equal SPL and power spectrum a high‐kurtosis noise exposure is more hazardous to hearing than is a low‐kurtosis noise. Two groups of chinchillas, with two animals per group, were exposed continuously for 5 days, to one of two classes of noise at a 90 dB SPL. The power spectrum of both noises was identical but the noises had different values of kurtosis. The results clearly showed that there was up to a 20 dB greater permanent hearing loss for the animals exposed to the high‐kurtosis noise. Detailed results of asymptotic and permanent threshold shifts and sensory cell losses will be presented. These results would appear to be a clear indication that, even for moderate levels of exposure, energy is not a sufficient variable upon which to base noise exposure standards. [Work supported by NIOSH.]