Response of Cochlear Models to Random Noise

Abstract

In most experiments reported here responses were recorded from a single-scala model at various points along the partition by means of a condenser probe after Bekesy (1941). It was ascertained by direct observation that the events as recorded occurred in the same manner in the usual dua-scala model. It was found that the models acted with distance as low-pass filters in response to random noise in the same way as to sinusoidal frequencies; also that responses were purely random; furthermore, locations of displacement maxima were determined in response to various noise bands in reference to those of sinusoidal frequencies equal to the center frequencies of these bands. The experimental results permitted the following conclusions: Each individual transient contained in the noise sets up its own traveling bulge. These bulges are superimposed randomly; thereby their original time sequence is not necessarily preserved with distance due to differences in propagation velocity. Even when the original noise band did not contain energy at low frequencies because of high-pass filtering, displacement occurred along the most distal portions of the partition, although at a reduced rate, since each individual bulge traveled the entire length. The latter fact may explain the phenomenon of remote masking (Bilger and Hirsh, 1956). (This work was supported by a Public Health Service grant.)