[Horizontal sound localization in young and middle-aged patients with symmetric sensorineural hearing loss in noisy environments].

Objective: This study evaluates the horizontal sound localization ability of young and middle-aged individuals with symmetric sensorineural hearing loss (SNHL) in noisy environments. It also examines the impact of hearing loss severity and signal-to-noise ratio (SNR) on localization accuracy. Methods: In this cross-sectional study, conducted from April 2023 to April 2024, 135 young and middle-aged patients (73 males and 62 females, aged 18~60 years) with SNHL who sought care at Beijing Chaoyang Hospital, were categorized into mild, moderate, and moderate-to-severe hearing loss groups (45 per group), with 45 normal-hearing controls (23 males and 22 females, aged 20~60 years). Participants completed localization tasks in quiet and noisy environments with SNR levels of 5 dB, 0 dB, -5 dB, and-10 dB. Root mean square error (RMSE) was used to measure localization accuracy. Repeated measures ANOVA assessed the effects of hearing loss and SNR on RMSE, while Pearson correlation evaluated the relationship between binaural 4-frequency pure-tone average (4fPTA) and RMSE. Multiple linear regression analyzed the predictive role of 4fPTA and age. Results: (1) Two-way repeated measures ANOVA showed that both hearing loss severity and SNR significantly affected RMSE [F=92.67,P<0.01;F=430.29,P<0.01], with a significant interaction between the two factors(F=92.67,P<0.01). (2) RMSE increased with hearing loss severity. At SNRs of 5 dB, 0 dB, and-5 dB, the moderate-to-severe group had significantly higher RMSE than the mild and moderate groups (P<0.01). No significant differences were found between mild and moderate groups (P=0.53, 0.57, 0.22). At-10 dB SNR, significant differences were observed across all groups (P<0.01). (3) RMSE increased non-linearly as SNR decreased. Mean RMSE values under quiet conditions and at SNRs of 5 dB, 0 dB, -5 dB, and-10 dB were (7.43±5.01)°, (9.80±5.74)°, (11.60±6.22)°, (14.56±7.07)°, and (18.74±8.02)°, respectively. (4) RMSE was significantly positively correlated with binaural 4fPTA (r=0.54~0.58, P<0.01). Multiple linear regression analysis indicated that the binaural average 4fPTA significantly predicted RMSE (P<0.01), explaining 30.5%-34.1% of RMSE variance. Age did not significantly contribute to RMSE variation. Conclusions: The degree of hearing loss and background noise SNR significantly affect horizontal sound localization in young and middle-aged SNHL patients. RMSE increases with hearing loss severity and decreases with higher SNR. The interaction between hearing loss and SNR is significant, and RMSE correlates with binaural 4fPTA. However, the regression model based on 4fPTA and age explains only part of the RMSE variance, suggesting other contributing factors.