William A. Ahroon
Sheau-Fang Lei
Roger P. Hamernik
Auditory Res. Lab., State Univ. of New York, Plattsburgh, NY 12901
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 different
shock tubes each producing blast waves having a different spectral composition;
one emphasizing low frequencies (<0.5 kHz), the other mid-frequencies (2--4
kHz). Impulses were presented at the rate of 1/s. This parametric paradigm
yielded 18 exposure conditions; 15 animals/condition. Hearing thresholds were
measured using auditory evoked potentials and the sensory epithelium was
evaluated with the surface preparation. In general, trauma increased as the
total energy of the exposure, determined by the peak SPL and number of
presentations, increased. The dependent variables (permanent threshold shift
and sensory cell loss) varied in an orderly fashion across frequency as the
peak and number of presentations was increased for both blast wave sources.
There were, however, consistent differences between the effects of the low- and
high-frequency energy ``content'' blast waves. Correlations between the
dependent variables and the energy of exposure were highest for P- or
A-weighted energies [Patterson et al.,