Role of dynamic cues in monaural and binaural signal detection.

Abstract

Three experiments were carried out to investigate the importance of dynamic cues in monaural and binaural detection tasks. All experiments employed a two-interval forced-choice procedure, in which the signal, a 500-Hz tone, 128 msec in duration, was added to the masker prior to gating in one of the two intervals. Both monaural (signal and masker diotic: M0–S0) and binaural (diotic masker, signal phase-reversed in one ear relative to the other: M0–Sπ) conditions were investigated. The masker (70 dB SPL) was either a tone of 500 Hz (Experiment 1), a 500-Hz carrier tone modulated by a 50-Hz tone (Experiment 2), or a 500-Hz carrier tone modulated by a band-pass noise centered at 60 Hz (Experiment 3). The angle of addition of the signal to the masker (α) was either 0°, 45°, 90° or 135°. In general, for all values of α, S0 thresholds increased from Experiment 1 to Experiment 3, indicating that monaural signal detection is more difficult in a dynamic than in a static environment. Sπ thresholds did not change significantly from Experiment 1 to Experiment 2, thus giving no support to the notion that detection of regularly varying interaural cues (at a modulation frequency of 50 Hz) is easier than detection of static cues. However, Sπ thresholds in Experiment 3 were slightly higher than in Experiment 2, indicating that detection of randomly fluctuating interaural cues is more difficult than detection of regularly fluctuating cues.