Rippled-spectrum resolution dependence on masker-to-probe ratio

Resolution of rippled sound spectrum (probe) in the presence of additional noise band (masker) was studied as a function of masker-to-probe ratio and sound level in normal listeners. The probe bands were 0.5-oct wide (ERB) centered at 2 kHz; the masker band either coincided with the probe (on-frequency masker), or was 3/4 octaves below (low-frequency masker), or 3/4 octaves above the probe (high-frequency masker). Ripple-density resolution in the probe band was measured by finding the highest ripple density at which an interchange of ripple peaks and valleys was detectable (the phase-reversal test). (i) The effect of the low-frequency masker increased (resolution decreased) when masker-to-probe ratio changed from -25 dB to +20 dB; the effect increased (resolution decreased) with sound level increase. (ii) The effect of the on-frequency masker steeply increased (resolution abruptly decreased) when masker-to-probe ratio exceeded 0 dB; the effect was little dependent on sound level. (iii) The high-frequency masker was little effective unless the masker-to-probe ratio reached 30-40 dB; the effect increased (resolution decreased) with sound level decrease. Thus, different position of the masker band relative to the probe resulted in qualitatively different kinds of spectrum-pattern resolution dependence on both the masker-to-probe ratio and sound level.