The experiment was designed to test a general model of the discrimination process. The discriminability of a given amplitude difference (in decibels) was found to be virtually independent of both the signal-to-noise ratio and the frequency of the tones to be discriminated, provided that the ratio of signal energy to noise-power density is sufficiently great. These findings lend support to a general model of the discrimination process suggested by Henning [G. B. Henning, J. Acoust. Soc. Am. 40, 1250(A)(1966)].