Abstract
Fully implantable hearing devices (FIHDs) have been developed as a new technology to overcome the disadvantages of conventional acoustic hearing aids. The implantable microphones currently used in FIHDs, however, have difficulty achieving high sensitivity to environmental sounds, low sensitivity to body noise, and ease of implantation. In general, implantable microphones may be placed under the skin in the temporal bone region of the skull. In this situation, body noise picked up during mastication and touching can be significant, and the layer of skin and hair can both attenuate and distort sounds. The new approach presently proposed is a microphone implanted at the tympanic membrane. This method increases the microphone’s sensitivity by utilizing the pinna’s directionally dependent sound collection capabilities and the natural resonances of the ear canal. The sensitivity and insertion loss of this microphone were measured in human cadaveric specimens in the 0.1 to 16 kHz frequency range. In addition, the maximum stable gain due to feedback between the trans-tympanic microphone and a round-window-drive transducer, was measured. The results confirmed in situ high-performance capabilities of the proposed trans-tympanic microphone.
Highlights
Implantable hearing devices (FIHDs) have been developed to assist the hearing impaired [1,2,3,4,5,6,7].most Fully implantable hearing devices (FIHDs) are still impractical because reliable, high-performance implantable microphones, which are crucial for FIHDs, have yet to be realized
We propose a new implantable microphone using a trans-tympanic ventilation tube in order to enhance the sensitivity and safety and to mitigate sound feedback from the middle-ear transducer
These measurements demonstrate that the proposed trans-tympanic microphone has minimal impact on the normal function of the tympanic membrane (Figure 6), has high sensitivity (Figure 7), and has a high gain margin outside of the middle-ear resonance frequency of approximately 1 kHz (Figure 8)
Summary
Implantable hearing devices (FIHDs) have been developed to assist the hearing impaired [1,2,3,4,5,6,7].most FIHDs are still impractical because reliable, high-performance implantable microphones, which are crucial for FIHDs, have yet to be realized. Implanting the microphone under the skin at the temporal bone, such as for Carina and TIKI, gives rise to potential problems These include significant body noise pickup during mastication, sound attenuation, and distortion from head touching due to the skin’s sound-filtering effect, and vulnerability to damage as a result of external impacts. Positioning the microphone in the ear canal or the middle ear, like for Esteem and TICA, results in less pickup of body noise and less sound attenuation. This method introduces an inherent feedback problem between the sound source and the implanted microphone. New implantable microphone designs that can overcome the problems of existing designs are needed
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