[Effects of the perforation of the tympanic membrane on its vibration--with special reference to an experimental...

Using canine temporal bone, perforations were surgically prepared at the anterior, inferior and posterior parts of the tympanic membrane, and the influences of these perforations on the tympanic vibration were observed and analyzed by holographic interferometry. Normal canine tympanic membrane had its respective single maximum amplitude points at its anterior and posterior parts at a frequency from the low compass to 2 kHz or so and showed a concentric circular vibration pattern centering mainly there around. At 3 and 4 kHz or so, the posterior and anterior parts began to show their respective sectional vibrations and with an increase in frequency, showed their further complicated multi-sectional vibrations. Resonance frequency was 1 or 2 kHz or so. The tympanic vibration following the preparation of perforations was as follows: 1) For the posterior perforation, the frequency at which the anterior sectional vibration began passed to a higher frequency, while for the other perforations, no change was noted in vibration pattern of the remaining tympanic membrane. 2) Comparative examination of the vibration amplitude at the mallear tip revealed that for a small perforation, no change in resonance frequency was noted regardless of the location of perforation and an increase in vibration amplitude was noted near the resonance frequency. 3) For the anterior perforation, no change in resonance frequency was noted even with an expansion of perforation and an increase in vibration amplitude was noted near the resonance frequency. 4) For the posterior and inferior perforations, the resonance frequency passed to a higher frequency with an expansion of perforation and an increase in vibration amplitude was noted near the resonance frequency.(ABSTRACT TRUNCATED AT 250 WORDS)