Bimodal stimulus presentation and expanded auditory bandwidth improve older adults' speech perception

A pair of experiments investigated the hypothesis that bimodal (auditory-visual) speech presentation and expanded auditory bandwidth would improve speech intelligibility and increase working memory performance for older adults by reducing the cognitive effort needed for speech perception.

Although telephone communication is important for helping older adults maintain social engagement, age-related sensory and working memory limits may make telephone conversations difficult.

Older adults with either age-normal hearing or mild-to-moderate sensorineural hearing loss performed a running memory task. Participants heard word strings of unpredictable length and at the end of each string were required to repeat back the final three words.Words were presented monaurally in telephone bandwidth (300 Hz to 3300 Hz) or expanded bandwidth (50 Hz to 7500 Hz), in quiet (65 dBZ SPL), or in white noise (65 dBZ SPL with noise at 60 dBZ SPL), with or without a visual display of the talker.

In quiet listening conditions, bimodal presentation increased the number of words correctly reported per trial but only for listeners with hearing loss and with high lipreading proficiency. Stimulus bandwidth did not affect performance. In noise, bimodal presentation and expanded bandwidth improved performance for all participant groups but did so by improving speech intelligibility, not by improving working memory.

Expanded bandwidth and bimodal presentation can improve speech perceptibility in difficult listening conditions but may not always improve working memory performance.

Results can inform the design of telephone features to improve ease of communication for older adults.