Detection of spectrally complex signals : Effect of difference in levels within components
Résumé
Several authors have demonstrated that detection can be improved by the presence of signal energy in many auditory channels. The subjects were likely to adopt a broadband listening strategy. The results can be reasonably well understood in terms of the multiband energy detector model (Green [1]). Whereas this rule is well established for equally detectable components, it seems to fail for equally intense components (Buus and Grose [2]). In this study, the detection of multicomponent signals that are not equally detectable was investigated precisely as a function of the level difference between components. In the first condition, detection thresholds were determined for seven-tone complex signals (80, 160, 320, 640, 1280, 2560, 5120 Hz), all equally detectable, with random starting phases masked by white noise. In a second condition, variation of the level relation between the components was examined: one of seven frequencies was increased by 5, 10, 15, 20 and 25 dB and then, three of them were increased by 5, 10 and 15 dB. Finally, we investigated the influence of masker type. The masker was a broadband noise with a set of harmonic partials, similar to an interior car sound. We examined the relative effectiveness of broadband noise masker with harmonics compared to white noise.