Middle-Ear Characteristics of Anesthetized Cats

TLDR

The study aims to compare middle‑ear characteristics between cats and humans. The authors measured ossicular motion with stroboscopic illumination across 30–10,000 Hz tones, derived a middle‑ear transfer characteristic from stapes displacement with open tympanic cavities, and assessed the effect of closing the cavities by recording round‑window electric responses. The stapes moves piston‑like up to 130 dB SPL with displacement linearly related to sound pressure; below 3 kHz the ossicles act as a rigid body, while above 3 kHz the incudo‑malleolar joint flexes, yielding a transfer characteristic for the middle ear with intact tympanic cavities.

Abstract

Ossicular motion was measured visually with stroboscopic illumination. Tonal stimulation ranged from 30 to 10 000 Hz. Up to 130 dB SPL (sound-pressure level), the motion of the stapes is predominantly piston-like, and its displacement amplitude is linearly related to sound pressure. At frequencies under 3000 Hz, the ossicles move as one rigid body; at higher frequencies, the stapes and incus displacements lag behind the malleus displacement, which suggests that the incudo-malleolar joint flexes. From measurements of stapes displacement at known sound pressures, we calculate a transfer characteristic for the middle ear with the tympanic cavities open. The effects of closing the tympanic cavities on the transfer characteristic were determined from measurements in which the electric response recorded from the round window was used as an indicator of middle-ear output. By combining these data, we obtain a transfer characteristic for the middle ear with the tympanic cavities intact. An attempt is made to compare middle-ear characteristics of cat and man.