When does binaural hearing benefit from ongoing envelope fluctuations

A number of classic and recent studies suggest that listeners’ access to ongoing binaural information in sounds with steady envelopes is significantly poorer than for sounds with stochastic or slowly modulated ongoing envelopes. For some types of binaural cues—e.g., envelope interaural time differences (ITD)—that result is consistent with the requirement of salient envelope features for accurate cue encoding. For interaural level differences (ILD) and fine-structure ITD, however, no such requirement exists and the result is therefore more surprising. Regardless, the overall results suggest that binaural-cue encoding-in general-relies heavily upon the occurrence of infrequent envelope fluctuations, such as sound onsets and slow (e.g., syllabic-rate) amplitude modulations. Here, the results of relevant studies are reviewed, along with conceptual and physiological models of sampling binaural cues during envelope fluctuations. Potential advantages for binaural hearing in reverberation and competing background...