Homophasic and antiphasic masking as a function of signal bandwidth and frequency region

Abstract

Thresholds for homophasic and antiphasic multicomponent tonal complexes were measured as a function of bandwidth in broadband noise to replicate and to extend the classic masking experiment [G. Gassler, Acoustica 4, 408–414 (1954)]. Gassler reported that masked thresholds for tonal complexes were nearly constant for bandwidths less than a nominal “critical bandwidth,” beyond which thresholds increased 3 dB/oct. Three experiments were conducted in broadband noise employing (a) homophasic signals similar to Gassler's (1 to 20 sinusoids spaced 20 Hz apart extending downward from 1100 Hz); (b) homophasic and antiphasic signals composed of 1 to 23 sinusoids centered at 500, 1000, and 2000 Hz; and (c) homophasic and antiphasic signals centered at 500 Hz with bandwidths to 800 Hz (71 sinusoids). The slope of the threshold/signal bandwidth function beyond 100 Hz was < dB/oct at each center frequency, ranging from 0.3 dB/oct (2000 Hz) to 1.9 dB/oct (1000 Hz). The data indicate that the integration of signal energy continued beyond the so‐called “critical band” estimates reported by Gassler. There were no substantial differences between the slopes of the homophasic and antiphasic conditions at 500, 1000, and 2000 Hz. [Work supported by VA Medical Research Service.]