The influence of Mossbauer source size and position on phase and amplitude measurements of the guinea pig basilar membrane.

Phase and amplitude measurements were made from the incus and basilar membrane in guinea pig using the Mossbauer technique. The basilar membrane/incus ratio had a maximum of about 60 dB and a phase accumulation of between 9 and 12 radians to CF. Two source sizes were used (60 X 85 and 20 X 60 microns) and the source was placed either on the modiolar edge of the basilar membrane or in the middle. Notches in plots of the basilar membrane/incus ratio occur at stimulus frequencies that appear to be associated with source size rather than position, suggesting that artefacts could be produced by the presence of the Mossbauer source.