Mechanics of a single-ossicle ear: II. The columella footplate of the pigeon.

The motion of the columella footplate (CFP) was measured in the pigeon using the Mössbauer technique. At the upper frequency limit of the cochlea the measured CFP response exhibited anti-resonant phenomena. These high-frequency responses were dependent on the orientation of the radiation detector, in a way which could not be explained by the cosine effect. The dependence of the recorded phase response on the measurement axis implies an additional vibration mode, which was out of temporal phase and non-colinear with the presumed translational vibration mode. The anti-resonant phenomena were not observed when the cochlear labyrinth was extirpated, thus excluding an explanation in terms of extraneous vibrations in the experimental apparatus or of loading by the Mössbauer source. Intra-cochlear reflection is proposed as the origin of the interference mode.