[An implantable microphone for electronic hearing aids].
Fully implantable hearing aids and cochlea implants of the future require an implantable microphone. A hermetically sealed implantable microphone based on the idea of a microphone implanted in the posterior wall of the auditory canal, as suggested by Ohno et al. in 1988, is presented. Through consistent technological and clinical design optimization, it was possible to achieve a membrane diameter of only 4.5 mm (as opposed to 8 mm in the Japanese system) and a significant volume reduction of nearly 50%. The microphone weights only 0.4 g. In spite of this miniaturization, the performance characteristics of the microphone equal those of the Japanese model or are superior. The sound-pressure transfer function shows a very small ripple and the bandwidth amounts to approximately 10 kHz. Because of its high tuning and high no-load resonance frequency, the microphone is mostly insensitive to post-operational changes to the loading mass on the microphone membrane initiated by the covering skin of the auditory canal. The sound-pressure transfer factor at 1000 Hz is approximately 1.5 mV/Pa. Using different manufacturing technologies, this value can be increased in the range of 6-8 dB with a corresponding reduction in bandwidth. Due to the small mass, the microphone is highly insensitive to environmental mechanical disturbances. The module is made of pure titanium and is hermetically sealed according to Mil-Std 883 D. Full metal encapsulation and additional internal electronic components protect the microphone well against environmental electromagnetic influences (EMC).
Leysieffer
H
H
Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Tübingen.
Müller
G
G
Zenner
H P
HP
D000818:Animals; D001309:Auditory Threshold; D002417:Cattle; D003054:Cochlear Implants; D003638:Deafness / Q000209:etiology / Q000534:rehabilitation*; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000534:rehabilitation*; D006801:Humans; D011474:Prosthesis Design; D013018:Sound Spectrography; D014159:Transducers