| Abstract #437, Date 2/16/99, Session M, Podium , 8:15a |
| Three-dimensional vibration of the stapes in the cat middle ear |
| *W.F.S. Decraemer (University of Antwerp, RUCA); S.M. Khanna (Columbia University, New York) |
The acoustical energy is transmitted from the tympanic membrane to the inner ear by the middle ear ossicles. It is generally accepted that the ossicles rotate around a fixed axis and function as mechanical levers. Under this concept the motions of malleus and stapes are one-dimensional. A series of measurements of malleus vibration made through the intact ear canal has clearly shown that the malleus motion is not a rotation about a fixed suspension axis but that translation and rotation components in all three dimensions are present and change dramatically over the frequency of hearing. An important question is what role these 3D vibrations play in the function of hearing? If the three components of vibration were utilized in the stimulation of the inner ear, they should also be present in the motion of the stapes. The motion of the stapes has been difficult to measure in the past because access is limited and only a small portion of the crura can be seen. In order to get a better access to the stapes a novel preparation of the cat temporal bone was utilized. To determine its 3D motion, the vibration of the stapes was measured with a confocal heterodyne interferometer at three points from different viewing angles. Its geometry was also measured. Assuming that the system behaves as a rigid body this data was used to generate an animation of the stapes motion. The stapes motion was found to be three dimensional. This suggests that these vibrations play a functional role in hearing. Part of this work was presented at the 3rd International Conference on Vibration Measurements by Laser Techniques, Ancona, Italy, June 16-19, 1998. |