Evidence Of Temporal Coding In A Forward Masking Task

The use of masking to study the auditory system\u27s frequency selectivity characteristics has been quite extensive. From these studies, a specific model of spectral analysis has been developed that emphasizes the energy distribution across frequency. This perspective is acceptable when describing the processing of simple tones, but certainly lacking when interest is in a description of the processing of more complex stimuli. The following experiments examined the ability of sinusoidal signals to mask single- and double-frequency probes. The paradigm was similar to that used in psychophysical tuning curve studies: the masker level was adapted to just mask a low-level probe of fixed frequency. The results showed that knowledge of masking with single-frequency probes cannot predict performance with the double-frequency probes. Further, it was found that these effects could be demonstrated in the binaural system, where the detection of difference tones could not play a role. A third experiment demonstrated similar effects with a different masking paradigm. It is obvious from these data, that the auditory system encodes more than the power spectrum of the signals; for example, aspects of the time structure of the waveforms are also coded and analysed. This is hypothesized to explain the observed differences. Therefore, it is incorrect to describe auditory frequency selectivity as simply a matter of power spectrum analysis