THE INFLUENCE OF STIMULUS ENVELOPE AND FINE-STRUCTURE ON THE BINAURALMASKING LEVEL DIFFERENCE

A masking level difference (MLD) paradigm was used to investigate the influence of stimulus envelope and stimulus fine-structure characteris tics on monaural and binaural hearing. The degree of masker envelope f luctuation was manipulated by selecting narrow-band noises (50 Hz) on a continuum of values of the normalized fourth moment of the envelope. The noises were specified as low-noise noise (LNN), medium-noise nois e (MNN), and high-noise noise (HNN). Fine-structure cues were studied by measuring thresholds at 500 and 4000 Hz, regions in which the avail ability of such cues to the auditory system differ substantially. In a ddition, thresholds were measured for Gaussian noise maskers (GN) and for maskers having a flat magnitude spectrum, termed equal-magnitude n oise (EMN) maskers. The results indicated lower NoSo thresholds for LN N than for the other four masker types. Furthermore, there were no dif ferences in threshold for maskers having moderate and high degrees of envelope fluctuation (MNN and HNN). The NoS pi thresholds were not sig nificantly different across masker type and were characterized by larg e individual differences among the seven listeners. The results are co nsidered in relation to models of monaural and binaural processing. Co nsistent with previous reports, the results indicate that binaural det ection depends on interaural differences in the stimulus envelope and fine structure at low frequencies and changes in the envelope at high frequencies. (C) 1998 Acoustical Society of America.