Auditory threshold shift following air pressure change in the external auditory canal

Auditory threshold shift for air conduction following various air pressure changes in the external auditory canal was examined. The obtained figure was named “tympanoaudiogram”. It was applied for normal subjects and patients with middle ear diseases. The results were compared with tympanogram. When artificial static air pressure (positive or negative pressures) was established in the ear canal of normal subjects, hearing attenuation was observed in low and middle frequencies. The curve was similar with the theoretical curve for increased stiffness of the tympanic membrane. Thus, 250Hz threshold curve as a function of air pressure change was similar with the shape of A type tympanogram. Tympanoaudiograms in the patients with congenital incudostapedial disconnection slowed an absolutely different pattern, although conventional tympanogram showed A or Ad types. Thresholds were elevated by +200mmH2O, however, marked threshold gains were measured by -200mmH2O in low and middle frequency tones. Differences in the threshold levels between +200 and -200mmH2O were 26 to 39dB in 250Hz. Further study should be performed to clarify the mechanism of these results. However, they indicate that this test can be of value in differential diagnosis of the ossicular diseases.