Masking of rippled-spectrum-pattern resolution in diotic and dichotic presentations

Using rippled noise probes, spectrum-pattern resolution was measured with and without a narrow-band noise masker. Diotic presentation of both the probe and masker (S(0)N(0) mode) resulted in decreased spectrum resolution as compared to the control (no masker) conditions. The effects of the low- and on-frequency maskers differed quantitatively, however in both cases the ability to discriminate the probe spectrum pattern was suppressed completely when the masker/probe level ratio exceeded 10dB (on-frequency masker) or 10-25dB, depending on the probe level (low-frequency masker). The effect of the high-frequency masker was negligible. Slight but noticeable releasing of the spectrum-pattern resolution was found when the probe was presented to both ears in-phase and the masker counter-phase (S(0)N(pi) mode). In conditions of the probe delivered to one ear and the masker to the other ear (S(L)N(R) mode), the effect on the spectrum-pattern resolution was slight or negligible within a wide range of the noise/probe ratio.