A NEW APPROACH TO COMPARING BINAURAL MASKING LEVEL DIFFERENCES AT LOWAND HIGH-FREQUENCIES

A new experimental technique for studying binaural processing at high frequencies is introduced. Binaural masking level differences (BMLDs) for the conditions N0Spi and NpiS0 were measured for a tonal signal in narrow-band noise at 125, 250, and 4000 Hz. In addition, ''transposed '' stimuli were generated, which were centered at 4000 Hz, but were de signed to preserve within the envelope the temporal ''fine-structure'' information available at the two lower frequencies. The BMLDs measure d with the 125-Hz transposed stimuli were essentially the same as BMLD s from the regular 125-Hz condition. The transposed 250-Hz stimuli gen erally produced smaller BMLDs than the stimuli centered at 250 Hz, but the pattern of results as a function of masker bandwidth was the same . The patterns of results from the transposed stimuli are different fr om those of the 4000-Hz condition and, consistent with the low-frequen cy masker data, generally show higher BMLDs. The results indicate that the mechanisms underlying binaural processing at low and high frequen cies are similar, and that frequency-dependent differences in BMLDs pr obably reflect the inability of the auditory system to encode the temp oral fine structure of high-frequency stimuli. (C) 1997 Acoustical Soc iety of America.