On the Fusion of Sounds Reaching Different Sense Organs

Abstract

A simple place theory of hearing raises the problem that several mixed harmonics may be attributed by the listener to their appropriate fundamental frequencies: the recognition of a vowel sound in the presence of other sounds requires that the formants of the vowel be detected as such and not classified with the other sounds. Thus, the neural message from a particular part of the basilar membrane probably conveys in some way information on the fundamental frequency, to a harmonic of which that part of the membrane is responding. The problem of fusion of sounds on the two ears is merely an extension of the problem of fusion of different frequencies in one ear. It is shown that synthetically produced speech will fuse when the first formant is presented to one ear and the second to the other, but it will not do so if the formants are given different fundamental frequencies. Even when both formants are given to the same ear, the latter condition fails to fuse. A further experiment with sustained formants shows that binaural fusion is not explained by the identity of some of the Fourier components on the two ears.