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After a brief discussion of the past use of and clinical need for high frequency hearing tests, a new technique is described that uses a special electric transduction mode: a 60-kHz carrier frequency is modulated by the desired audiofrequency. The combined signal is applied to the skin over the mastoids by Mylar-covered electrodes. On perception, the audiofrequency part of the input shows all the properties of a bone-conduction signal. The carrier frequency is dispersed in the tissues. Production and calibration of electrical high frequency signals, up to 20 kHz, is straightforward and easier than that of conventional air-conduction and (vibromechanical) bone-conduction signals. The efficacy of the method is illustrated by means of preliminary hearing tests conducted on several subjects.
Tonndorf et al. (Thu,) studied this question.