Investigating the effects of age and hearing loss on speech intelligibility and amplitude modulation frequency selectivity

The perception of amplitude modulation (AM), characterized by a frequency-selective process in the modulation domain, is considered critical for speech intelligibility. Previous literature has provided evidence of an age-related decline in AM frequency selectivity. Additionally, a notable sharpening of AM tuning with hearing loss has been observed, which was proposed to be related to a perceptual advantage resulting from peripheral compression loss. This study explores whether such changes in AM tuning with age and hearing loss contribute to the speech intelligibility challenges older listeners often face in noisy environments. Young (n = 10, aged 22-28 years) and older (n = 9, aged 57-77 years) listeners with normal hearing as well as older listeners with hearing impairment (n = 9, aged 64-77 years) participated in the study. All had previously taken part in studies on AM tuning. Speech-reception thresholds (SRTs) were collected under conditions including stationary, fluctuating, and competing-speech maskers. The results revealed an age-related increase in SRTs, with an additional negative impact of hearing loss. Beyond age and audibility, a measure of AM tuning significantly contributed to explaining the variance in SRTs across listeners for specific maskers. These findings motivate further exploration of the relationship between AM frequency selectivity and speech intelligibility in noise.