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.