Abstract
In order to get the detailed diagnostic information from the tympanogram, we devised a new tympanometric system, in that the frequency of the probe tone changed continuously from 45Hz to 5000Hz. This system was applied to 11 subjects with normal hearing and normal ear drum.
The curves of the tympanogram varied from a V-shaped in low frequencies of the probe-tone to an inverted V-shap in higher frequencies showing a W-shape in mid-frequencies, as the frequency of the probe tone was shifted. The frequency that provoked the pattern change of V to W in the tympanogram was different from subject to subject, and varied from 1400Hz to 2200Hz. Additional model experiment suggested us strongly that the stiffness of the middle ear was one of the most decisive factor in determining the frequency in which the tympanogram pattern changed its V-shape to W-shape.
It was also observed that the asymmetry of the tympanogram appeared as the frequency of the probe tone increased. Several causes of this asymmetry were discussed.
Further study should be performed, that is, application of this system to make a differential diagnosis for the ossicular discontinuity or the ossicular fixation.
