The Hazard of Exposure to 2.075 kHz Center Frequency Narrow Band Impulses

Abstract : A previous report by Patterson et al., (1991) derived a frequency weighting function from audiometric and histological data gathered on 118 chinchillas exposed to a variety of narrow band impulses at various peak intensities. The weighting function clearly demonstrated that equivalent amounts of impulsive energy concentrated at different frequencies is not equally hazardous to the auditory system. However, on the basis of a preliminary analysis of a large amount of audiometric data obtained from chinchillas exposed to high level blast waves (Patterson and Hamernik, 1991), there appeared to be some inconsistencies between the narrow band impulse data and the blast wave data in the region of 2.0 kHz. To resolve this discrepancy, two additional groups of animals were exposed to narrow band impulses with a center frequency of 2.075 kHz and peak intensities of 134 dB and 139 dB. The results of these two additional groups confirm the shape of the original P-weighting function and indicate that changes must be made in our approach to the analysis of the blast wave data referred to above.