Active hearing, active speaking

A static view of the world permeates most research in speech and hearing. In this idealised situation, sources don’t move and neither do listeners; the acoustic environment doesn’t change; and speakers speak without any effect of auditory input from their own voice or other speakers. Corpora for speech research and most behavioural tasks have grown to reflect the static viewpoint. Yet it is clear that speech and hearing takes place in a world where none of the static assumptions hold, or at least not for long. The dynamic view complicates tradi- tional signal processing approaches, and renders conventional evaluation processes unrepeatable since the observer’s dynamics influence the signals received at the ears. However, the dynamic viewpoint also provides many opportunities for active processes to exploit. Some of these, such as the use of head movements to resolve front-back confusions, are well-known, while others exist solely as hypotheses. This paper reviews known and potential benefits of active processes in both hearing and speech production, and goes on to describe two recent studies which demonstrate the value of such processes. The first shows how dynamic cues can be used to estimate distance in an acoustic environment. The second demonstrates that the changes in speech production which take place when other speakers are active result in increased glimpsing opportunities at the ear of the interlocutor.