A brief overview of factors affecting speech intelligibility of people with hearing loss: implications for amplification

Purpose: The authors aimed to determine the predictability of speech intelligibility of people with different degrees of hearing loss from audibility and other factors. Method: After a brief overview of why people with hearing loss have greater difficulty in understanding speech than people with normal hearing, the authors describe a study that was aimed to predict speech intelligibility from audibility, psychoacoustic abilities, cognitive ability, and age. Results: The study showed that the ability of people with hearing loss to extract speech information from an audible signal decreased with increase in hearing loss. This hearing loss desensitization was significantly related to hearing thresholds, sharpness of psychophysical tuning curves, presence of dead regions, age, and cognitive ability. After allowing for the effects of hearing loss, the authors found that speech intelligibility was significantly related to age and cognitive ability. The effects did not vary with frequency. Conclusions: The current evidence supports the allowance of hearing loss desensitization in prescribing amplification that is aimed to maximize speech intelligibility. There is insufficient evidence to recommend the inclusion of estimates of frequency resolution or dead regions in prescribing amplification.