On the perception of the direction of sound

Source abstract

Abstract The nature of the clue by which we are able to pronounce whether a sound of low pitch reaches us from the right or form the left was long a mystery, seeing that in such cases the difference of intensities at two ears, used singly, is inappreciable. By some special laboratory experiments conducted about three years ago, I was able to show that the discrimination depends upon the phase-difference at the two ears, and the sound is judged to be on that side where the phase is in advance. When the pitch is higher (much above g') no distinct lateral effect accompanies a phase-difference, and the discrimination of right and left in ordinary hearing undoubtedly depends upon intensities. Commenting on these results, I remarked (p. 224): "The conclusion, no longer to be resisted, that when a sound of low pitch reaches the two ears with approximately equal intensities, but with a phase-difference of a quarter of a period, we are able so easily to distinguish at which ear the phase is in advance, must far-reaching consequences in the theory of audition. It seems no longer possible to hold that the vibratory character of sound terminates at the outer ends of the nerves along which the communication with the brain is established. On the contrary, the processes in the nerve must themselves be vibratory, not, of course, in the gross mechanical sense, but with preservation of the period and retaining the characteristic of phase-a view advocated by Rutherford, in opposition to Helmholtz, as long as 1886."