The role of envelope beat cues in the detection and discrimination of second-order amplitude modulation.

Abstract

The present study extends previous work from Lorenzi et al. [J. Acoust. Soc. Am. 110, 2470–2478 (2001)] by investigating the respective contribution of two temporal cues (fast modulation sideband and slow envelope beat cues) to the detection and discrimination of “second-order” sinusoidal amplitude modulation (SAM). Second-order SAM detection and rate discrimination abilities were measured at low beat rates (fm′⩽128 Hz) with a “carrier” modulation rate fixed at a high value (fm=256 Hz). The second-order SAM data were compared with first-order SAM detection and rate discrimination thresholds measured in similar conditions at rates fm between 1 and 256 Hz. The results showed that (1) through 64 Hz, first- and second-order SAM detection thresholds increased similarly when stimulus duration decreased from 2 s to 250 ms, whereas first-order SAM detection thresholds remained unaffected by changes in duration when fm⩾128 Hz, and (2) through 32 Hz, first- and second-order SAM rate discrimination thresholds were similar and substantially lower than first-order SAM rate discrimination thresholds measured at fm⩾128 Hz. These data demonstrate that the perception of second-order SAM is mainly based on the slow envelope beat cues. They also suggest a substantial contribution of the slow envelope beat cues appearing at the output of modulation filters tuned to or near fm to the perception of second-order SAM.