Thresholds were measured for detecting a brief 6-kHz sinusoidal signal preceded by a broadband noise masker (forward masking), followed by the masker (backward masking), or both preceded by and followed by the masker (combined masking). The masker-signal interval was systematically varied. Consistent with the literature, thresholds in the combined-masking condition were higher than would be predicted by an energy-sum of the effects of the individual forward and backward maskers. This is often referred to as 'excess' masking. The data were modeled by subjecting the amplitude of the stimuli to a power-law nonlinearity followed by a sliding temporal integrator ('window'). It was assumed that threshold corresponds to a fixed signal-to-noise ratio at the output of the window. The best fits to the data were obtained using a power less than unity (0.5 to 0.7), i.e. by a compressive nonlinearity. Generally good fits to the data were achieved, indicating that the model is able to account for the decay of forward and backward masking as well as the effects of combining pairs of maskers (excess masking). The temporal windows derived from the data are also able to predict thresholds in decrement and increment detection tasks, and to account for the longer-term effects of masker duration in forward masking.
Bibliographical noteFunding Information:
This work was supportedb y the Medical Research Council (UK), by a Research Studentshipa wardedb y the Sciencea nd EngineeringR esearchC ouncii (UK) to the first author and by Meridian Audio. We thank Brian Glasberg for assistancew ith programminga nd modelinga nd Tom Baer, Michael Stone, David Green and one anon~ous reviewerf or helpful commentso n an earlier version of this paper.
- Temporal integration
- Temporal resolution