[Vibration analysis in middle ear model with artificial ossicles, total ossicular replacement prosthesis (TORP) by holographic interferometry].

Vibration of tympanic membranes of the middle ear model with TORP and flat membrane made of gum were studied by means of holographic interferometry. Results were as follows. 1) As the tension of the gum became high, the amplitude decreased in low frequency. The segmental vibration was observed in low frequency as the tension became low. 2) The difference between 0.03mm and 0.06mm was not significant though the gum was used in the thickness of 0.03mm, 0.06mm and 0.3mm. In 0.3mm, inhibition of the vibration was found in all frequencies, especially in high frequency. 3) Amount of the volume of middle ear cavity was in proportion to the vibration amplitude of tympanic membrane in 250Hz and 500Hz. The proportionality, however, was not found at 1kHz or more. 4) Center zone of the model moved best like a piston in 250 and 500Hz though intermediate zone of normal middle ear moved best. Segmental vibration was observed in lower frequency than normal human ear. The difference between ceramic TORP and Plasti-Pore TORP was not significant. In high frequency, both have poor sound transmission because of the flat tympanic membrane and TORP like umbrella as amphibian and reptilian. It was ideal that the tympanic membrane like curved cone with the wide frequency characteristics should be made in tympanoplasty.