Contributions of Low- and High-Frequency Sensorineural Hearing Deficits to Speech Intelligibility in Noise

Abstract This study investigates the role of hearing sensitivity, age and supra-threshold hearing to speech recognition in quiet, stationary, and modulated noise. Three participant groups were tested: young normal hearing (yNH), older normal-hearing (oNH), and older hearing-impaired (oHI) listeners. The relative importance of near and supra-threshold hearing deficits was assessed in different frequency regions by measuring speech reception thresholds (SRTs) using broadband speech targets and noise maskers (BB), but also low- and high-pass (LP & HP) filtered versions of these stimuli. Interrelations between SRTs in different conditions were studied and SRTs were compared to amplitude-modulation detection sensitivity as a metric for supra-threshold hearing ability in the spectral and temporal (envelope) domains. The main results are: (i) LP SRT performance dominates overall BB speech recognition. (ii) LP SRTs determine individual differences in BB SRTs for stationary noise while HP SRTs determine individual differences in BB SRTs for modulated noise. (iii) Masking release (the improvement in intelligibility produced by the modulations of noise) was present for BB, LP and HP conditions and related to the modulated (not stationary) SRT performance. (iv) Sensitivity to temporal-envelopes is important for HF masking release and SRTs in modulated noise, whereas spectral resolution is a better predictor of LF speech recognition in modulated noise. This study identified the role of near and supra-threshold cues in the perception of amplitude-modulation and speech-in-noise, and can steer the development of hearing-aid algorithms targeted to mediate supra-threshold hearing deficits.