Pitch Changes Produced by Bone-Transmitted Thermal Noise or Pure Tone

Abstract

During the course of some experiments on listening by bone conduction, the author noticed an increase in the pitch of a pure tone in the middle audiofrequency region when a pure tone of lower frequency was sounded, and the qualitative results of several ensuing experiments were reported in a letter to the editor. The work to be described here dealt with the rise in pitch of a pure 2000-cps tone in the presence of a broad band of thermal noise and also in the presence of pure tones of lower frequency. All sounds were presented by bone conduction using the air and bone conduction audiotesting assembly developed at U.C.L.A. The results of extensive tests on one observer are presented as well as the results of pitch rise tests on several different listeners. All listeners had normal hearing as indicated by audiograms and otological examinations. It was found that the pitch of the 2000-cps tone rose with increasing level of the disturbing sound and that the greatest pitch rise occurred just before the pure tone was masked. Individual differences were evident among listeners. The effect on the pitch of the 2000-cps tone of clenching the teeth is discussed for one observer. A tentative explanation of the phenomena is given.