[Vibrations of the human tympanic membrane measured with Laser Doppler Vibrometer]

The knowledge of the physiology of the normal ear is important to understand the function of the ear. It is especially crucial in the reconstruction of the destroyed ear to apply the knowledge of the normal ear. We present results of tympanic membrane vibrations measurements using Laser Doppler Vibrometer in human temporal bone specimens. Six temporal bone specimens were harvested within 48 hours of death and stored cooled until preparation. The preparation included mastoidectomy with posterior tympanotomy and partial resection of the facial nerve to visualize the stapes with its footplate. We measured velocity and displacement of each quadrant of the tympanic membrane and the umbo with the laser Vibrometer equipped with velocity and displacement decoders. The sensor head OFV-534 produced and read the reflected laser beam directed at a measured point with a dedicated micromanipulator attached to an operating microscope. A retro-reflective tape was used to enhance the reflection of the laser beam. Vibrations were induced by a acoustic stimulation at the tympanic membrane. The results of the measurements were corrected to a sound pressure in the external ear canal. Laser Doppler Vibrometer system allows an undisturbed measurement of vibrations in the middle ear. Posterior quadrants of the tympanic membrane have greater velocity and displacement than anterior quadrants in lower frequencies up to 2 kHz.