. . .


Mechanisms of forward masking

Magdalena Wojtczak and Neal F. Viemeister
Department of Psychology, University of Minnesota, Minneapolis, Minnesota

Experiments involving forward masking were run with the aim of elucidating the mechanism underlying this phenomenon. Two possible mechanisms were considered: adaptation following masker offset, and persistence of excitation. In one experiment, detection of a 10-ms noise probe following a 150-ms noise masker was measured as a function of the level of a 20-ms burst of noise temporally centered on the probe. Model predictions were generated assuming either a reduction of gain applied to the probe (adaptation) or additivity of persisting masker excitation and excitation produced by the probe. Both models accounted for the data equally well. In the second experiment, listeners performed an image centering task involving binaural presentation of a 4-kHz 10-ms probe. In one ear, the probe was preceded by a 150-ms noise forward masker. The level of the probe in the unmasked ear was adjusted until the image of the probe was centered. In general the image was centered when the probe level in the unmasked ear was much lower (by 10-20 dB) than that in the masked ear. This result could be explained in terms of adaptation underlying forward masking but not in terms of persistence of excitation. [Supported by NIH/NIDCD DC00683].

      
       Wojtczak, M. and Viemeister, N.F. (2004). Mechanisms of forward masking. Presented at the 147th Meeting of the Acoustical Society of America.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .