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

Abstract

The degree to which supra-threshold hearing deficits affect speech recognition in noise is poorly understood. To clarify the role of hearing sensitivity in different stimulus frequency ranges, and to test the contribution of low- and high-pass speech information to broadband speech recognition, we collected speech reception threshold (SRTs) for low-pass (LP 1.6 kHz) and broadband (BB) speech-in-noise stimuli in 34 listeners. Two noise types with similar long-term spectra were considered: stationary (SSN) and temporally modulated noise (ICRA5-250). Irrespective of the tested listener group (i.e., young normal-hearing, older normal- or impaired-hearing), the BB SRT performance was strongly related to the LP SRT. The encoding of LP speech information was different for SSN and ICRA5-250 noise but similar for HP speech, suggesting a single noise-type invariant coding mechanism for HP speech. Masking release was observed for all filtered conditions and related to the ICRA5-250 SRT. Lastly, the role of hearing sensitivity to the SRT was studied using the speech intelligibility index (SII), which failed to predict the SRTs for the filtered speech conditions and for the older normal-hearing listeners. This suggests that supra-threshold hearing deficits are important contributors to the SRT of older normal-hearing listeners.