Sound-source enumeration by hearing-impaired adults

To help measure the veracity with which the auditory world is heard by hearing-impaired listeners, we studied the ability to count the number of discrete sources that are present. In two experiments, stimuli were newly selected 5-s samples of concatenated sentences from 1 to 7 locations in simulated rooms of varying reverberation, presented from a circular loudspeaker array. In the first experiment, listeners responded with the number of locations heard after each presentation. In the second experiment, listeners heard two presentations, an interval with n sources (one talker per location) and an interval with n + 1 sources; listeners responded which interval had more sources. Results corroborate recent work showing the maximum number of identifiable sources is roughly four. Asymmetry in hearing impairment reduced the ability to enumerate locations. Various conditions of presentation were tested: headphone and aided results were not markedly different from unaided results, and reverberation had only a modest inflating effect on the perceived number of sources. The ramifications for complex listening as well as the potential relation to cortical representations of auditory space are discussed. [Work supported by the MRC (U135097131) and the Chief Scientist Office (Scotland).]