Temporal and Directional Cue Effects on the Cocktail Party Problem for Patients With Listening Difficulties Without Clinical Hearing Loss.

Abstract

To evaluate the listening difficulty in a cocktail party environment in the sound field in order to better demonstrate patients' difficulties listening in noise, and to examine temporal and directional cue effects on the speech intelligibility in patients with listening difficulties in noise in comparison with control subjects. This study examined and analyzed 16 control subjects without any complaints of listening difficulties and 16 patients who had visited the outpatient clinic of the Department of Otolaryngology-Head and Neck Surgery, Tohoku University Hospital, with complaints of listening difficulties, especially in background crowded conditions, despite having relatively good hearing on routine audiograms and speech audiometry. Using five loudspeakers located in front of the subject and at 30° and 60° to the left and right from the front, word intelligibility for the target voice (female talker) presented from one of the loudspeakers in random order with four distractor voices (male talker) was assessed under the following cue conditions: (1) "no additional temporal/directional cue (only talker sex as a cue)"; (2) "fixed temporal cue without directional cue" (white noise bursts [cue sounds] were presented from the five loudspeakers just before word presentation at 500-ms intervals); (3) "directional + variable temporal cues" [cue sounds were presented from the loudspeaker where the next target word would be presented with a variable inter-stimulus interval [ISI] of 500, 1000, 1500, or 2000 ms between the cue sound and word presentation); and (4) "directional + fixed temporal cues" (cue sounds were presented from the loudspeaker where the next target word would be presented with a fixed ISI of 500 ms). The results indicated the following: (1) word intelligibility under distractors was significantly deteriorated in patients with listening difficulties compared with control subjects, although the clinical speech in noise test using the headphone system did not show any significant differences between the two groups; (2) word intelligibility under distractors for patients with listening difficulties was significantly improved with directional cues presented in advance; and (3) under most cue conditions, individual differences in word intelligibility among patients with listening difficulties were significantly correlated with their dichotic listening ability, which is one of the indicators used to assess auditory selective attention ability. The results of this study indicate the usefulness of the presentation of directional cues for speech comprehension in the cocktail party situation in patients with listening difficulties, as well as the importance of evaluating the degree of listening difficulties spatially in the cocktail party situation.