<title>Moire-shift interferometer measurements of the shape of human and cat tympanic membrane</title>

Abstract

The shape of the tympanic membrane is fairly complicated and seems to be of significant importance in the coupling of the acoustic sound pressure in the external ear canal to the motion of the middle ear ossicles. Precise measurements of the tympanic membrane shape are not available in literature. To measure the shape of a very thin, curved biological membrane a technique is required which does not deform the surface during the measurement. Casting techniques are therefore not well suited. A noncontacting measurement technique based on moire interferometry proved to be a better tool. A moire shift interferometer was used to measure with great precision the shape of the external surface of human and cat tympanic membrane. The dense matrix of z(x,y) values thus obtained does not only describe the shape with high spatial resolution but may also be used to calculate different geometrical parameters. As an example of direct application the authors have calculated the area of the curved surface to the pars tensa and pars flaccida for a human and a cat tympanic membrane.