Residual Low-to-Mid Frequency Hearing in the Poorer-Hearing Ear Is Associated with Better Sound Localization in Single-Sided Deafness.

Background

Single-sided deafness (SSD) impairs spatial hearing because of the loss of binaural cues. However, some individuals with SSD show unexpectedly accurate localization, suggesting compensatory mechanisms. This study investigated whether residual hearing in the poorer-hearing ear is related to localization ability and whether this relationship varies across frequency bands.

Methods

Fourteen SSD patients participated in a sound localization task using broadband (BB), low-pass (LP), and high-pass (HP) filtered noise stimuli. Residual hearing thresholds (125-20 000 Hz) were measured across 7 frequency bands, and their associations with localization performance were analyzed. Clinical variables (duration and onset age of SSD) were also assessed.

Results

Significant correlations between localization performance and residual hearing were observed only under BB conditions and only in the poorer-hearing ear. The strongest associations emerged in low-to-mid frequency bands (up to approximately 4000 Hz) and remained significant after controlling for clinical variables and for high-frequency hearing in the same ear. No significant associations were found with HP- or LP-filtered stimuli. Neither onset age nor duration of SSD was significantly associated with localization performance after correction for multiple comparisons. Localization was also more accurate for stimuli presented on the better-hearing side, an asymmetry that reached significance only for stimuli containing high-frequency energy.

Conclusion

Preserved low-to-mid frequency hearing in the poorer-hearing ear was associated with better localization in patients with SSD when the stimulus contained rich spatial cues, such as broadband noise. These findings highlight the relevance of frequency-specific residual hearing, particularly at low-to-mid frequencies, to spatial hearing in this population.