Contributions of binaural processing to segregating and selecting speech in a complex sound mixture

Intuitively, we all believe that binaural processing plays a critical role in communication, especially at the venerable “cocktail party.” Indeed, if you attend a poster session at a large conference (like the ICA), close your eyes, plug one ear, and try to follow a scientific discussion, you will experience the importance of having two ears. Here we will discuss how binaural processing contributes to two key aspects of understanding speech in crowded settings: focusing attention on whichever source is important in the sound mixture (selection), and separating that source from other sources in the mixture (segregation). Behavioral data show that binaural cues help with source selection, or focusing of auditory attention. When it comes to sound segregation, the contributions of binaural hearing depend on the time scale that one considers. For segregating one speech syllable from a sound mixture, the data suggest that binaural cues are not very salient; they are overridden by other cues such as common onset and offset. However, when connecting together syllables into a continuous stream of speech, spatial cues play a much stronger role. Understanding the role of binaural hearing, and the time scales on which spatial cues matter, perceptually, can guide how binaural cues are used in hearing devices, such as hearing aids, to improve speech understanding in everyday settings.