Frequency discrimination in amplitude-modulated maskers

Abstract

Under some conditions, the detection threshold for a pure tone signal masked by a bandpass Gaussian noise can be reduced by the introduction of amplitude modulation (AM) to the masker. Previous data suggest that this advantage may be reduced for discrimination tasks, such as frequency discrimination of a masked tone [Hall et al., J. Acoust. Soc. Am. 102, 1746–1754]. In the present study, frequency discrimination thresholds were estimated for a 500-Hz pure tone presented at a range of levels (3, 6, and 12 dB re: masked detection threshold). The masker was either a Gaussian noise or an AM noise (bandpass filtered 50–4000 Hz), with a range of square wave AM rates (10–40 Hz). Masking release was greater for 10-Hz AM than 40-Hz AM, but frequency discrimination was better for the 10 than the 40-Hz rate when measured at equal sensation levels. This result suggests that temporal resolution and integration may have important contributions to frequency discrimination measured for tones presented in modulated maskers. [Work supported by NIH NIDCD Grant R01 DC000418.]