Impaired noise adaptation contributes to speech intelligibility problems in people with hearing loss.

Understanding speech in noisy settings is harder for hearing-impaired (HI) people than for normal-hearing (NH) people, even when speech is audible. This is often attributed to hearing loss altering the neural encoding of temporal and/or spectral speech cues. Here, we investigated whether this difference may also be due to an impaired ability to adapt to background noise. For 25 adult hearing-aid users with sensorineural hearing loss, speech reception thresholds (SRTs) were measured for natural and tone-vocoded words embedded in speech-shaped noise (SSN). The stimuli were preceded or not by a 1-second adapting SSN precursor. Adaptation was calculated as the difference in SRT between the two precursor conditions. Corresponding data for 28 NH listeners were taken from a previously published study. SRTs were worse for HI listeners, confirming that hearing loss diminishes access to speech acoustic cues. Furthermore, noise adaptation was negatively correlated with the age-controlled hearing loss both for natural (rho=-0.56, N = 52, p < 0.001) and vocoded (rho=-0.45, N = 39, p = 0.002) words. Impaired adaptation contributed up to 10% of the SRT loss in HI listeners. We conclude that HI listeners suffer from poorer speech in noise recognition not only because of impaired access to speech acoustic cues but also because they are less able to adapt to background noise.