1993 Volume 1993 Issue Supplement66 Pages 75-80
Hearing altered during or immediately after changing in ambient pressure, has not yet actually been examined but just presumed. In this study, the way in which alterating the ambient pressure on hearing in normal subjects was examined using our sound-proof pressure chamber. Twenty six healthy subjects were included in this study. The subjects were placed in the sound-proof pressure chamber in a supine position and instructed not to perform active equilibration of the middle ear pressure. The pressure was changed± 500 mmH2O at 33 mmH2O/sec. Results were as follows: 1) Hearing levels by both air and bone conduction deteriorated.2) At low frequency tones, the threshold of bone conduction increased more than that of air conduction. At high frequency tones, the threshold of both bone and air conduction were only slightly changed.3) The grade of deterioration was greater in cases where the chamber pressure was increased (descent) than that in cases where the chamber pressure was decreased (ascent). The major part of deterioration in bone conduction was considered functional and due to an increase in both the stiffness and damping of the sound transmission mechanism.
