The Bone-conduction Threshold Measurements under the Masking Noise.

Abstract

When the level of air-conducted thermal noise reaches about 30phones, it begines to mask a bone-conducted pure tone which is applied to the same ear. The bone-conduction threshold value increases in proportion to the noise level above 30phones. Thermal noise applied to the opposite ear begines to mask the bone-conducted pure tone at about 60phones. The transmission loss from one ear to the other is about 50db for thermal noise or pure tones which is applied to one ear by an air-conduction receiver, but is 7db for bone-conducted pure tones. The change of the bone-conduction threshold due to the attachment of the masking air-conduction receiver is avoided by a sufficiently large cavity put between the receiver and the ear.