The effect of spatial separation on informational masking of speech in normal-hearing and hearing-impaired listeners.

The ability to understand speech in a multi-source environment containing informational masking may depend on the perceptual arrangement of signal and masker objects in space. In normal-hearing listeners, Arbogast et al. [J. Acoust. Soc. Am. 112, 2086-2098 (2002)] found an 18-dB spatial release from a primarily informational masker, compared to 7 dB for a primarily energetic masker. This article extends the earlier work to include the study of listeners with sensorineural hearing loss. Listeners performed closed-set speech recognition in two spatial conditions: 0 degrees and 90 degrees separation between signal and masker. Three maskers were tested: (1) the different-band sentence masker was designed to be primarily informational; (2) the different-band noise masker was a control for the different-band sentence; and (3) the same-band noise masker was designed to be primarily energetic. The spatial release from the different-band sentence was larger than for the other maskers, but was smaller (10 dB) for the hearing-impaired group than for the normal-hearing group (15 dB). The smaller benefit for the hearing-impaired listeners can be partially explained by masker sensation level. However, the results suggest that hearing-impaired listeners can use the perceptual effect of spatial separation to improve speech recognition in the presence of a primarily informational masker.