Emilio Segrè Visual Archives

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Bell Labs F3

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Bell Labs F3

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Image title: 
Bell Labs Sound Experiments
Credit line: 
Bell Laboratories / Alcatel-Lucent USA Inc., courtesy AIP Emilio Segrè Visual Archives, Physics Today Collection

Caption reads: "Two heads are better than one for Bell Telephone Laboratories research into the ways people locate the direction of sound. Practical results of the recent 'double dome' research at Murray Hill, NJ, may be the improvement of stereophonic radio and TV programs, which are transmitted nationwide over telephone facilities. In the experiments, two microphones in the ears of the dummy, 'Oscar II' were substituted for human ears. Oscar's head reproduced the 'shadowing' of sound by a human head. Persons participating in the tests -- such as Mary Lou Hartig, shown -- wore the extra head so that motions of their heads would be reproduced, for even very small movements influence hearing. The natural sounds received in each microphone were altered electronically by acoustics scientist, R. L. Hanson (right) and were delivered to the earphones. Listeners were asked to point to the apparent direction of the altered sound. Normally, the ear that is closer to a sound hears it earlier and louder than the other ear. Here, however, artificial differences in time delays and intensity were introduced, and it was found that the factor of intensity is more important than previously believed. If sound reaches one ear first but reaches the other ear somewhat louder, the hearer is completely confused."

Photo date: 
Bell Labs Innovations