THE EFFECTS OF REVERBERANT BLAST WAVES ON THE AUDITORY-SYSTEM

Chinchillas were exposed to 1, 10, or 100 reverberant impulses at 150, 155, or 160 dB peak SPL. The impulses were generated by one of two di fferent shock tubes, each producing blast waves having a different spe ctral composition, with one emphasizing low frequencies (<0.5 kHz) and the other midfrequencies (2-4 kHz). Impulses were presented at the ra te of one per minute. This parametric paradigm yielded 18 exposure con ditions with 15 animals/condition. Hearing thresholds were measured us ing auditory-evoked potentials and the sensory epithelium was evaluate d with the surface preparation. In general, trauma increased as the to tal energy of the exposure, determined by the peak SPL and number of p resentations, increased. The dependent variables (permanent threshold shift and sensory cell loss) Varied in an orderly fashion across frequ ency as the peak and number of presentations were increased for both b last wave sources. There were, however, consistent differences between the effects of the low- and high-frequency energy ''content'' blast w aves. Correlations between the dependent variables and the energy of e xposure were highest for P- or A-weighted energies [Patterson et al., J. Acoust. Sec. Am. 93, 2860-2869 (1993)]. (C) 1996 Acoustical Society of America.