[Influence of liquid volume in the middle ear on tympanic membrane vibration (experimental study by holographic...

The influence of middle ear liquid on the tympanic membrane (TM) vibration was studied using the holographic interferometry. The physiological saline solution was injected into the middle ear cavity of the canine temporal bone. The liquid volume in the middle ear cavity was changed into 3 grades in order to observe the difference of the vibration pattern between them. The vibratory patterns of a normal canine TM remained unchanged in their first mode up to a frequency of approximately 2 kHz. In this mode, there were peak displacement regions in the posterior and anterior quadrants. The TM vibrations showed sectional patterns, above 3 kHz in the posterior and above 4 kHz in the anterior. After liquid retention, the following were observed. 1. The frequency at which sectional patterns occurred shifted to a lower frequency in the immerged portion, but showed no definite tendency in the unimmerged portion. 2. Maximum amplitudes of the anterior and posterior quadrants of the TM and the mallar tip shifted to somewhat higher frequencies for the liquid volume below the level of the tip portion, but contrary, shifted to lower frequencies for the liquid volume there above. 3. The ossicular chain tended not to make normal function for the TM vibration with an increase of liquid volume.