A Pathway for Information Transmission to the Ear

The use of implantable hearing aids and cochlear implants as an aid to neurosensory deafness is becoming an established procedure. The transmission of a processed speech signal is accomplished either transcutaneously via radiofrequency or percutaneously by connector coupling. Whereas the former is sensitive to electromagnetic interference, the latter increases the risk of infection. To overcome these disadvantages, an infrared (IR) system for transmission through the tympanic membrane was devised and tested. The transmitter/receiver consisted of an IR light emitting diode (LED;920nm) and a photovoltaic cell. The LED was placed inside the auditory canal of four dogs and the photovoltaic cell in the tympanic cavity over the cochlear promontory. A sinusoidal signal modulation was applied to the LED. The emitted signal was detected undistorted after crossing the tympanic membrane, with an average absorbance of 20%. High-frequency cut-off was adequate for cochlear implant purposes and audio prosthetic devices in general. The authors conclude that the tympanic membrane may be used as a translucent sealed interface to transmit data in the audio range to the middle and inner ears, with small power loss, good frequency response, and immunity to interface.