AUDITION BY BONE CONDUCTION

Abstract

Audition resulting from vibration of the skull is investigated in various respects using audiometers with bone conduction receivers and other equipment. Applying the driving element at any point sets the entire skull into vibration, and the stimulus in one ear resulting from driving the skull on that mastoid is found to exceed the stimulus in the other ear by only 3.4±2.2 decibels. The statistical accuracy of bone conduction observations is found and compared with published air conduction results. The sensitivity on the mastoid exceeds that on the forehead by 5 db on the average. Tests of instruments for measuring air conduction and bone conduction sensitivity to determine the amount of desired over undesired type of stimulation are described and the results given. The effect of a telephone receiver in producing hearing in the opposite ear is observed with two available cases of assured total deafness on one side and the data given. Beats involving bone conduction are observed. The fact that bone conduction sensations often seem in one ear is compared with similar results for air conduction stimuli under certain conditions and a general statement of all results is made. The problems of apparent hyper-sensitivity resulting from abnormality and occlusion are discussed in the light of the foregoing results.