Your Own Voice under Earphones

Abstract

Probe microphone measurements show that there is more over-all sound pressure underneath a talker's unactivated headset than there is directly in front of his mouth! Experiments indicate that these sound pressures are not primarily attributable to the leakage underneath the earcushions or to the voice “coming out of the ear,” but arise mainly from the coupling of a cavity to the vibrating skull. Data obtained using three commercially available earphone cushions and a variable cavity showed that the size of the cavity was a more important factor than the type of material coupling the cavity to the head. Decrements as great as 26 db were achieved in under-the-earphone sustained vowels by picking up the fundamental voice frequency and introducing it into the earphones after appropriate adjustments of its phase and amplitude. The subjective experience of talking with this “phased-sidetone” condition was surprising: the localization of the voice changed radically to the middle of the head and the subject experienced great effort in speaking—similar to a slight case of laryngitis. These results indicate that the auditory mechanism is exposed to unsuspected sound pressure when a talker is wearing commercial type headsets, and that he experiences a marked subjective change when this signal is attenuated. Parts of this research were sponsored under U. S. Army Signal Corps Contract No. DA 36-039 sc-42562.