Glimpsing speech in temporally and spectro-temporally modulated noise.

Speech recognition in fluctuating maskers is influenced by the spectro-temporal properties of the noise. Three experiments examined different temporal and spectro-temporal noise properties. Experiment 1 replicated previous work by highlighting maximum performance at a temporal gating rate of 4-8 Hz. Experiment 2 involved spectro-temporal glimpses. Performance was best with the largest glimpses, and performance with small glimpses approached that for continuous noise matched to the average level of the modulated noise. Better performance occurred with periodic than for random spectro-temporal glimpses. Finally, time and frequency for spectro-temporal glimpses were dissociated in experiment 3. Larger spectral glimpses were more beneficial than smaller, and minimum performance was observed at a gating rate of 4-8 Hz. The current results involving continuous speech in gated noise (slower and larger glimpses most advantageous) run counter to several results involving gated and/or filtered speech, where a larger number of smaller speech samples is often advantageous. This is because mechanisms of masking dominate, negating the advantages of better speech-information sampling. It is suggested that spectro-temporal glimpsing combines temporal glimpsing with additional processes of simultaneous masking and uncomodulation, and continuous speech in gated noise is a better model for real-world glimpsing than is gated and/or filtered speech.