The qualitative results provide supportive evidence that complex movements of the stapes footplate may lead to cochlear activity. Further experiments are necessary to confirm and quantify these effects.

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For the description of the normal hearing process mechanical models are appropriate and distinct pathological situations can be simulated by changing specific parameters. Nonlinear behavior is found due to nonlinear constitutive equations of the ear drum, the ligaments and the coupling between implant and ossicles as well as due to active processes in the inner ear. Based on multibody system approach models of natural middle ears and reconstructed ears with active implants have been established including some rough assumptions of the nonlinear behavior. To study the dynamic behavior frequency domain methods and time integration has been used. A high risk of damaging the hearing organ of the inner ear is given for loud sound events especially in transient cases. Some measurements in the clinical practice are based on nonlinear effects to detect pathological situations. With simulated multifrequency tympanometry the effect of incudo-stapedial separation on umbo motion is shown. For actively driven implants the effect of different working conditions of the middle ear structure on sound transfer due to prestress in the coupling region has been simulated.

Traditionally, the evaluation of auditory functioning in the hearing-aided patient has been limited to subjective response measures. This report demonstrates that brainstem evoked responses can provide an objective and reliable measure of auditory performance in such individuals. Moderate-output body-level aids were worn by three normal-hearing adults, on whom unaided responses had previously been obtained. Highly reliable responses to clicks, tone, and noise bursts were obtained from all subjects. Increases in the gain of the aid, and thus signal loudness, produced shorter latency and larger amplitude responses, as expected on the basis of unaided input-output functions. The number of decibels above physiological threshold required to generate a 6.0-msec latency response was smaller in the aided when compared to the unaided condition, thus mimicking the electrophysiological finding in “recruiting” patients. Variations in the low-frequency portion of the aid's frequency-response curve produced little change in the evoked response, while increases in its high-frequency cutoff produced shorter latencies. The reliable and systematic relation between subjective sensation, hearing-aid characteristics, and neuro-electrical response appears to warrant the continued investigation of the use of brainstem evoked responses for hearing aid fitting in hearing-impaired populations.

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