Acoustic effects in in-the-ear hearing aid response: results from a computer simulation.

The response of a hearing aid depends on the design of the instrument and on the characteristics of the individual ear. In this paper a computer simulation of an in the ear (ITE) hearing aid is used to determine the effects on the hearing aid response caused by variations in the size of the ear canal, the magnitude of the eardrum impedance, and the vent size and damping. The simulation results indicate that, for an unvented hearing aid, changes in the size of the ear canal or the eardrum impedance shift the average sound pressure level at the eardrum but have relatively small effects on the overall shape of the frequency response. A vented instrument presents a more complicated situation since the vent modifies the low-frequency response in a predictable manner but can have unexpectedly pronounced effects at high frequencies due to the acoustic feedback.