Abstract:

When cat ears were exposed to an airbag impulse in an open, closed, or sealed passenger compartment, a mean-threshold shift of 60 dB occurred immediately and resolved into a 37-dB permanent threshold shift [Price et al., J. Acoust. Soc. Am. 99, 2464 (1996)]. A mathematical model of auditory hazard for the cat ear ``explained'' the results [Price and Kalb, J. Acoust Soc. Am. 99, 2464 (1996)]; but there was still a question as to what the implications would be for human ears exposed to such impulses. A parallel model has been created for the human ear and the hazard reevaluated. For the human ear, the presence of middle ear muscle activity is calculated to be a key element in preserving hearing as is the (paradoxically) protective effect of a closed or sealed passenger compartment as compared with one that is open. The individual exposed in a vented passenger compartment and who did not see the accident coming is, therefore, predicted to be at greatest risk. Algorithms are being developed and validated for connecting the model's output (auditory damage units) to projected changes in threshold for a human population whose susceptibility is normally distributed.