A tutorial on complex sound fields for audiometric testing.

A fundamental understanding of soundfield characteristics in enclosed spaces is required in order to appreciate and predict the behavior of complex sound fields (i.e., sound fields created with at least two uncorrelated sound sources on different axes) used in auditory tests for evaluating hearing aid performance, especially speech-in-noise tasks. This article is a tutorial starting with idealized definitions of acoustical spaces. Next is an exploration of the interactions between practical sound fields and the enclosures that contain them, based on a synthesis of ideas formed from a review of classical acoustical theory combined with direct observation. Finally, the discussion turns to the application of complex sound fields for speech-in-noise testing in typical audiometric test rooms and a practical realization of such a sound field with consideration given to the limitations imposed by factors covered in the foregoing discussions.