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Two methods are described for determination of the microphonic generator transfer characteristic using data from bitonal stimulation experiments. In one method, the filtered high-frequency microphonic output component is measured at the extreme points of the modulation envelope for a sequence of intensity levels of the lower-frequency component. This method is applied to data derived from a modulation test procedure making use of a wide range of test intensities for both the high- and low-frequency components and also to data generated in a test using a single sequence of stimuli with increasing intensity of the lower frequency. In a second method, the modulation envelope of the higher-frequency microphonic response to a bifrequency acoustic stimulus is used to determine a segment of the generator transfer characteristic. The results of a sequence of determinations for different lower-frequency intensities show good agreement with each other and with the transfer characteristic derived by the first method. However, the second method shows that there is an appreciable level-dependent hysteresis, the mechanism for which has not been determined. The transfer characteristics determined would give rise to a pronounced dc rectification component in the direction of positive summating potential.

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