The effects of noise-bandwidth, noise-fringe duration, and temporal signal location on the binaural masking-level difference.
The effects of forward and backward noise fringes on binaural signal detectability were investigated. Masked thresholds for a 12-ms, 250-Hz, sinusoidal signal masked by Gaussian noise, centered at 250 Hz, with bandwidths from 3 to 201 Hz, were obtained in N(0)S(0) and N(0)S(π) configurations. The signal was (a) temporally centered in a 12-ms noise burst (no fringe), (b) presented at the start of a 600-ms noise burst (backward fringe), or (c) temporally centered in a 600-ms noise burst (forward-plus-backward fringe). For noise bandwidths between 3 and 75 Hz, detection in N(0)S(0) improved with the addition of a backward fringe, improving further with an additional forward fringe; there was little improvement in N(0)S(π). The binaural masking-level difference (BMLD) increased from 0 to 8 dB with a forward-plus-backward fringe as noise bandwidths increased to 100 Hz, increasing slightly to 10 dB at 201 Hz. This two-stage increase was less pronounced with a backward fringe. With no fringe, the BMLD was about 10-14 dB at all bandwidths. Performance appears to result from the interaction of across-time and across-frequency listening strategies and the possible effects of gain reduction and suppression, which combine in complex ways. Current binaural models are, as yet, unable to account fully for these effects.
UCL Ear Institute, 332 Grays Inn Road, London WC1X 8EE, United Kingdom. i.yasin@ucl.ac.uk
Ifat
I
Yasin
G Bruce
GB
Henning
D001309:Auditory Threshold / Q000502:physiology; D006801:Humans; D009622:Noise; D010470:Perceptual Masking / Q000502:physiology*; D011571:Psychoacoustics; D011594:Psychometrics; D017603:Signal Detection, Psychological / Q000502:physiology; D013017:Sound Localization / Q000502:physiology*; D013018:Sound Spectrography