The effect of masker bandwidth on signal detectability

Abstract

The effect of masker bandwidth on the detectability of narrow‐ and wideband signals was investigated. The signals were pure tones and noise bands. The noise bands varied from 50–792 Hz, center frequency being 1500 Hz. Stimuli were computer generated and the noise bands had nearly rectangular spectra. Log‐log plots of threshold as a function of masker bandwidth (Fletcher plots) were found to be well fitted by two line segments. An iterative least‐squares procedure was employed to determine slopes and intercepts of the line segments. These parameters were found to depend on the bandwidth of the signal. An energy detection model [Green, J. Acoust. Soc. Am. 32, 121–131 (1960)] was modified by the addition of internal variability that is bandwidth‐dependent. This modified energy‐detection model was able to predict the results obtained with narrow bandwidth signals. The relative magnitude of internal variability was estimated and the ratio of internal‐to‐external variability agreed with estimates presented by Raab and Goldberg [J. Acoust. Soc. Am. 57, 437–447 (1975)]. In contrast, the results obtained with wideband signals were not predicted by the simple model. They may reflect the operation of a mechanism for the enhancement of spectral contours.