Listening bandwidths and frequency uncertainty in pure-tone signal detection^a)

The effect of frequency uncertainty on the detection of tonal signals in noise was studied using a modified probe-signal method.Widths of the listening bands used during detection were measured directly, allowing for an analysis that separates the effects of having to monitor multiple independent bands from those due to limited frequency resolution. Uncertainty was varied by beginning each trial with a cue consisting of one, two, or four randomly chosen, simultaneously presented tones. An expected signal, whose frequency matched one of the components in a cue, was presented on a majority of trails. However, on remaining trails, the signal was a probe, which meant that its frequency differed from one of the components in the cue by a constant ratio. Performance as measured in percent correct declined for probes at increasingly distant ratios from the expected values. The results were converted to dB using individual psychometric functions for expected signals and listening bands were fitted using the rounded exponential filter of Patterson et al. [J. Acoust. Soc. Am. 72, 1788–1803 (1982)]. The obtained bandwidths are comparable to those reported using notched-noise maskers, but there is a small but consistent increase in bandwidth with increased numbers of components in the cues. The primary result is that the effects due to uncertainty are well described by a 1-of-M orthogonal band model, which takes into consideration limitations of the detector, including the widths of the listening bands.