Ear Speech

Microphones for use in noisy places, e.g., military aircraft, have always been a headache for acoustic engineers. If placed close in front of the mouth, they pick up a great deal of "ambient" noise, as well as sounds that come from the wearer's breathing. Throat microphones are noisy, too, and not ideally intelligible. Both types can be a nuisance to the wearer and interfere with other equipment.

At Ohio State University, Drs. Henry M. Moser, John J. Dreher and Herbert Oyer, backed by the Air Force, are trying to develop a special ear microphone. They have found that when a speaker's mouth is covered by a sound-absorbing baffle, his speech can be heard, weakly but distinctly, through a stethoscope in one of his ears. Picked up with a microphone, ear speech can be amplified until it is as loud as desired. It has a rather "bright" sound, but is not very different from mouth speech.

The beauty of the system is that an ear microphone does not get in the wearer's way and is easy to isolate from noise around it. The Ohio scientists tested the intelligibility of ear speech by giving six men the same test sentence to speak through both ears and mouth. When the outside noise level was low, both kinds of speech came over well, but as the noise was increased, ear speech forged ahead.

In practice, an airplane pilot will probably listen through one ear and talk through the other. The whole apparatus will be tightly enclosed in his helmet. Outside noise will have a hard time working its way into this communication system, which is almost as private as if it were entirely inside the wearer's head.

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