Localization training results in individuals with unilateral severe to profound hearing loss

Abstract

Adults with unilateral hearing loss often demonstrate decreased sound localization ability and report that situations requiring spatial hearing are especially challenging. Few studies have evaluated localization abilities combined with training in this population. The present pilot study examined whether localization of two sound types would improve after training, and explored the relation between localization ability or training benefit and demographic factors. Eleven participants with unilateral severe to profound hearing loss attended five training sessions; localization cues gradually decreased across sessions. Localization ability was assessed pre- and post-training. Assessment stimuli were monosyllabic words and spectral and temporal random spectrogram sounds. Root mean square errors for each participant and stimulus type were used in group and correlation analyses; individual data were examined with ordinary least squares regression. Mean pre-to post-training test results were significantly different for all stimulus types. Among the participants, eight significantly improved following training on at least one localization measure, whereas three did not. Participants with the poorest localization ability improved the most and likewise, those with the best pre-training ability showed the least training benefit. Correlation results suggested that test age, age at onset of severe to profound hearing loss and better ear high frequency audibility may contribute to localization ability. Results support the need for continued investigation of localization training efficacy and consideration of localization training within rehabilitation protocols for individuals with unilateral severe to profound hearing loss.

Figure 1

Display diagrams used during localization training sessions. Panel A is the diagram as viewed by the participant with the loudspeaker location set-up and play button. Panels B–E depict the progression of cue specificity, from exact source (B) to no cues (E). Examples of cued loudspeaker locations are indicated in black (B–D).

Figure 2

Individual participant localization results. Results are shown for Words (left column of panels, squares), Spectral RSS stimuli (middle column of panels, triangles) and Temporal RSS stimuli (right column of panel, circles). For each participant and stimulus type, scores in grey-filled symbols are pre-training results and in black-filled symbols are post-training results. Symbols represent mean responses in degrees azimuth. X-axis represents the stimulus speaker location and the y-axis represents the response speaker selection. Significant differences between the pre- and post-training conditions for a given stimulus type are indicated with asterisks in the lower right corner of each panel.

Figure 3

Group mean RMS error scores. Group means are shown for Words and Spectral and Temporal RSS stimuli. Scores in grey are pre-training results and in black are post-training results. * p < 0.05; ** p < 0.01.