EXPERIMENTS RELATED TO THE DETECTION OF A TONE MASKED BY ANOTHER TONE

Five experiments were completed in an effort to determine which cues a llow the detection of a tone in the presence of another tone of a diff erent frequency. Four cues associated with the added tone were examine d (a) changes in overall level, (b) changes in envelope modulation (be ats), (c) changes in pitch, and (d) changes in phase (frequency) modul ation. Detection thresholds were measured using a two-interval, forced choice paradigm, and for maskers of 400 and 3000 Hz. The data suggest that the presence of beats acts as a cue for detection when the signa l and masker frequencies are within ten percent of one another. For la rger frequency separations the data did not support any of the detecti on models examined [(a)-(d) above]. Based on limited direct observatio ns and on the failure of the single-channel models tested, it appears that the detection of a tone in the presence of another tone depends o n the detection of changes in the pattern of intensity and/or the patt ern of temporal synchrony across frequency.