Comparison of Detectability and Discriminability of Tones of Different Durations under Homophasic and Antiphasic Conditions

Abstract

Using a two-alternative, temporal, forced-choice technique (2ATFC), the detectability of four (50, 60, 100, and 200 msec) 500-Hz signals in a continuous noise masker (50-dB spectrum level) was determined. The ability of the observers to discriminate the 50-msec tone from each of the three longer tones was also measured using a similar psychophysical technique. Psychometric functions for detection and for the discrimination of duration were obtained under both homophasic (N0-S0) and antiphasic (N0-Sπ) conditions. Under the homophasic condition, the observers required an increasing amount of signal energy as the difference in duration became smaller in order to perform as well in discrimination as they did in detection. With the antiphasic condition, a similar effect was observed, except that the displacement of the psychometric functions for discrimination toward greater signal energies was much more pronounced than in the homophasic condition. In addition, the slopes of the psychometric functions for discrimination were generally lower than the corresponding ones for detection.