Binaural detection as a function of signal frequency and noise level

Abstract

This is a continuation of work by a number of investigators on the dependency of binaural masking-level differences (MLDs) upon signal frequency and noise spectrum level. Monaural (SM) and binaural (Sn]signals of 150, 250, 500, and 1,200 Hz were employed. The spectrum level of correlated noise (NO) was varied between + 10 and +55 dB. The results show that, with very low noise levels (+10 dB), the largest MLDs for monaural and binaural signals are obtained at 500 Hz (4 and 9 dB, respectively). As the noise level is raised to +55 dB, the signal frequency at which the largest MLDs occur shifts to 250 Hz (12 and 18 dB). At 150 Hz, the MLD increases from less than 1 and 3 dB to about 10 and 17 dB as the noise level is increased from + 10 to +55 dB. At 1,200 Hz, the MLD is relatively independent of noise level. Data are presented to support the argument that the small MLDs found with low-frequency signals at low noise levels are a special case of the effects upon detection of reducing the correlation of the masker due to the presence of uncorrelated acoustic noise generated under earphones and internal auditory system noise .