The Location on the Skull of A Bone Conduction Receiver and the Lateralization of the Sound Impression

Abstract

During examination of patients, having normal ears in all respects, it was often observed that a tuning fork placed on top of the skull but outside the midline was heard with the contralateral ear and not, as one might expect, with the ipsilateral ear.

In normal test persons a tuning fork placed on top of the skull. outside the midline may be heard, depending on place and frequency, in the contralateral ear. This phenomenon was investigated by placing a bone conduction receiver along an adhesive strip attached to the head of the observer running from one ear over the top of the skull to the other ear.

For frequencies around 500 cps there was one region on each side of the skull where placing of the receiver gives lateralization of the tone to the contralateral ear. For frequencies around 1200 cps there is on each side of the skull a region with lateralization to the ipsilateral side and one with lateralization to the contralateral side.

It could be demonstrated that these lateralization impressions are due to interaural intensity relations rather than to interaural phase differences.

It is suggested and experimentally supported, that these intensity differences are due to regions of minimal and maximal amplitude existing in the vibrating skull.