Abstract:
At its most basic, hazard to hearing is the result of energy arriving at the cochlea. However, the conductive path to the cochlea has many nonuniformities which profoundly shape the driving forces that actually reach it. The normal tuning of the ear as well as the azimuth of the source, an amplitude-dependent nonlinear middle ear, and time-varying middle ear muscle activity are in the conductive path and add to the complexity of interpreting the intracochlear events which culminate in hearing loss. To deal with this complexity, a mathematical model of the ear is being developed to predict hazard accurately. An earlier model for the cat ear [G. R. Price and J. T. Kalb, J. Acoust. Soc. Am. 90, 219--227 (1991)] has been adapted for the human ear and calculational procedures to allow for the effect of the azimuth of the source and middle ear muscle responses have been added. The model allows waveform input from the free field as well as at the ear canal entrance or ear drum position and calculates a hazard based on the stresses at the level of the basilar membrane. This number will be correlated with hearing losses measured from experiments with human ears.