Informational masking in the modulation domain

• Published in: The Journal of the Acoustical Society of America 2021-05, Vol.149 (5), p.3665-3673
• Main Authors: Conroy, Christopher, Kidd, Jr, Gerald
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation; Attention; Auditory Threshold; Perceptual Masking; Psychometrics
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/10.0005038

Uncertainty regarding the frequency spectrum of a masker can have an adverse effect on the ability to focus selective attention on a target frequency channel, yielding informational masking (IM). This study sought to determine if uncertainty regarding the modulation spectrum of a masker can have an analogous adverse effect on the ability to focus selective attention on a target modulation channel, yielding IM in the modulation domain, or "modulation IM." A single-interval, two-alternative forced-choice (yes-no) procedure was used. The task was to detect 32-Hz target sinusoidal amplitude modulation (SAM) imposed on a broadband-noise carrier in the presence of masker SAM imposed on the same carrier. Six maskers, spanning the range from 8 to 128 Hz in half-octave steps, were tested, excluding those that fell within a two-octave protected zone surrounding the target. Psychometric functions (d'-vs-target modulation depth) were measured for each masker under two conditions: a fixed (low-uncertainty/low-IM) condition, in which the masker was the same on all trials within a block, and a random (high-uncertainty/high-IM) condition, in which it varied randomly from presentation-to-presentation. Thresholds and slopes extracted from the psychometric functions differed markedly between the conditions. These results are consistent with the idea that IM occurs in the modulation domain.