A Middle Ear Microphone Design Based on the Physiology of the Human Ear

A capacitive displacement sensor matching the physiological characteristic of the human middle ear is presented. The transducer measures tiny deflections of the umbo, a part of the middle ear bone chain, to evaluate sound events stimulating the eardrum. Compared to other approaches, our sensor delivers a lower susceptibility to gravity due to a higher resonant frequency. Furthermore, measurement results in the lower frequency range are competitive to other research groups. Within the frequency range of 200 Hz to 10 kHz, a resolution of 4 pm is achieved using a signal processing bandwidth of 100 Hz. This resolution is equivalent to the lower threshold of speech or to a loudness level of 40 phon.