The Impulse Response Vibration of the Human Ear Drum

Acoustical Dirac impulses (15 μsec duration, sound energy from 600 Hz to 25 kHz) are used under free field conditions for evoking impulse responses in the tympanic membranes of awake, unrestrained human volunteers. The impulse responses are analysed in the time- and frequency domains. The impulse responses within different frequency bands add to a total impulse response of complex shape (Fig. 3). The frequency spectrum of the vibration velocity of the mallear handle (umbo) shows several maxima in amplitude and corresponding deflections of phase, but the maxima are mainly caused by changes in the spectrum of the sound travelling to the ear drum. In contrast, the transfer function of the umbo (sound pressure to vibration) is smooth with only little variation in amplitude and a gradual development of phase. It is argued that the common notion of the middle ear as a low-pass filter is misleading.