NoSo and NoS pi thresholds as a function of masker level for narrow-band and wideband masking noise.

NoSo and NoS pi thresholds for a 500-Hz signal were determined as a function of masker level for masking noises having 600- and 50-Hz bandwidths centered on 500 Hz. Noise levels of 0, 10, 20, 30, 40, 50, and 60 dB/Hz were used for the 600-Hz bandwidth, and noise levels of 0, 10, 20, 30, 40, 50, 60, and 70 dB/Hz were used for the 50-Hz bandwidth. The So thresholds increased as a function of increasing noise level with a slope close to 1.0, for both the 50- and 600-Hz masker bandwidths. For the 600-Hz-wide masker, the S pi thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 20 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 20 dB/Hz. For the 50-Hz-wide masker, the S pi thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 40 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 40 dB/Hz. The results are discussed in terms of different binaural processes involving interaction between monaural critical bands centered on the signal frequency, and interaction involving monaural critical bands outside the monaural critical band centered on the signal. It was suggested that the narrow-band noise results are probably more appropriate than the wideband noise results when considering binaural interaction involving monaural critical bands centered on the signal frequency.