Human ear tympanum oscillation recorded using a magnetoresistive sensor

A magnetic probe using a commercial magnetoresistive sensor for monitoring the dynamics of the human tympanic membrane has been developed. The method is based on the measurement of the magnetic flux changes produced by the vibrations of a small magnet attached to the tympanic membrane. The system was evaluated with respect to its applicability to detect displacement amplitudes in the tympanum by measurements performed in an excised temporal bone. A sensitivity sufficient to detect vibrations down to about 65×10−9 m was observed for a wide range of frequencies between 200 Hz and 5.0 kHz. Displacement amplitudes of 400 nm on average were detected with an error of ±65 nm.