SOME FACTORS INFLUENCING COMODULATION MASKING RELEASE AND ACROSS-CHANNEL MASKING

The purpose of this study was to determine whether comodulation maskin g release (CMR) and across-channel masking (ACM) are by-products of a similar across-channel mechanism. This was addressed by examining how the two are affected by stimulus manipulations expected to influence t heir magnitude. Subjects were required to detect a 1000-Hz signal in t he presence of a masker that consisted of a 1000-Hz (on-frequency) com ponent alone or that component and up to six flanking components (500, 600, 700, 1300, 1400, and 1500 Hz). The on-frequency and flanking com ponents typically were sinusoidally amplitude modulated at 10 Hz, alth ough not necessarily in phase with one another. In experiment 1, the a mount of CMR and ACM was highly influenced by whether the signal consi sted of one or three 50-ms tone bursts; in fact, ACM was only observed when the signal was a train of three 50-ms tone bursts. In experiment s 2 and 3, CMR tended to increase as the modulation depth or the numbe r of flanking components increased, whereas ACM was relatively unaffec ted by these manipulations. In addition, ACM was observed under dichot ic situations, whereas CMR was not. Taken together, the results sugges t that ACM and CMR may be mediated by different mechanisms. (C) 1995 A coustical Society of America.