A laboratory study on a capacitive displacement sensor as an implant microphone in totally implant cochlear hearing aid systems.
A totally implant cochlear hearing aids system, integrating an implant microphone, interface electronics, a speech processor, a stimulator, and cochlear electrodes, can overcome the uncomfortable, inconvenient, and stigma problems associated with the conventional and semi-implantable hearing aids. This paper presents a laboratory feasibility study on the use of an electret condenser microphone (ECM) displacement sensor, serving as an implant microphone, and combined with a spring coupler to directly sense the umbo acoustic vibration. The umbo vibration characteristics were extracted from literature to determine the coupler and sensor requirements. A laboratory model was built to simulate the vibration source and experimentally study the transmission coefficient. Experimental data demonstrate that by using a 5 N/m stiffness spring, the umbo vibration amplitude as high as 67% can be transmitted to the sensor. Measurement of the sensor system on the temporal bone was also made. The minimum detectable sound pressure level (SPL) at 1 kHz is 41 and 67 dB for laboratory and 38 and 64 dB for temporal bone measurement for 1 and 388 Hz bandwidth, respectively. Better performance was achieved in a higher frequency. Results and analysis of this study can be used as a guideline for the future design of displacement sensors as implant microphones.
Huang
Ping
P
Electrical Engineering and Computer Science Department, Case Western Reserve University, Cleveland, OH 44106, USA. pxh57@cwru.edu
Guo
Jun
J
Megerian
Cliff A
CA
Young
Darrin J
DJ
Ko
Wen H
WH
D000162:Acoustics / Q000295:instrumentation*; D003054:Cochlear Implants; D025802:Electric Capacitance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers