Evaluating Speech-in-Noise Deficits in Conductive Hearing Loss: the Underestimated Role of Low-Frequency Air-Bone Gaps.

INTRODUCTION:This study aimed to investigate the impact of conductive hearing loss (CHL) on speech perception in noisy environments, with a particular focus on the role of low-frequency air-bone gaps. While CHL is traditionally considered a peripheral auditory disorder, emerging evidence suggests that it may also affect central auditory processing, especially under complex acoustic conditions. METHODS:Thirty individuals diagnosed with CHL and thirty age-matched participants with normal hearing were recruited from the Audiology Unit of Gazi University. All participants underwent comprehensive audiological evaluations, including the Turkish Hearing in Noise Test (T-HINT). Speech recognition thresholds (SRTs) were measured adaptively in four listening conditions: quiet and noise presented from the front, right, and left. Speech-spectrum noise was delivered at 65 dB SPL. RESULTS:Participants with CHL demonstrated significantly elevated SRTs across all noise conditions compared to the control group, indicating reduced speech-in-noise intelligibility. However, speech discrimination scores in quiet did not differ significantly between groups. Notably, larger air-bone gaps at low frequencies were strongly correlated with poorer SRTs, suggesting a frequency-specific vulnerability in noisy environments. CONCLUSION:CHL substantially impairs speech perception in noise, primarily due to the detrimental effects of low-frequency air-bone gaps. These findings underscore the crucial role of low-frequency auditory input in the temporal and spectral processing of speech, underscoring the need for frequency-specific diagnostic and rehabilitative strategies in clinical audiology.