By Mishaela DiNino, Ph.D.
Each speech sound, such as the “eh” vowel in “SET” or the “aaa” vowel in “SAT,” contain various timing and frequency components that make the sound unique. Listeners use these auditory cues to differentiate between speech sounds, helping them to understand what a conversation partner is saying.
However, age-related changes in the auditory system may reduce older adults’ ability to perceive the auditory cues that contrast speech sounds, potentially contributing to listening difficulties in both quiet and in noise.
We recently conducted an investigation to compare young and older adults’ ability to use a frequency cue and a duration cue to differentiate between “SET” and “SAT” sounds in quiet and in noise. We created sounds whose frequency content and duration ranged on a continuum from those most like “SET” to those most like “SAT.”
Young and older adults listened to these sounds and identified them as either being “SET” or “SAT,” even though most sounds contained frequency content and duration somewhere in between actual “SET” or “SAT.”
We then conducted an analysis to determine the extent to which each listener relied on each cue. For example, if a sound was presented that had frequency content more like “SET” but duration more like “SAT,” and the listener identified the sound as “SAT,” they would have relied more on duration and less on frequency content to identify that sound.
Previous research has shown that frequency cues are the most important auditory cues for identifying vowel sounds. However, relative to young adults, we found that older adults were less able to use the frequency cue to categorize “SET” and “SAT.”
Instead, they used the duration cue more than did young adults, in both quiet and in noise. Frequency cues require more precise coding in the auditory system than do duration cues.
As published in JASA Express Letters in June 2024, our results therefore suggest that age-related changes in the auditory system decrease perception of frequency cues for identifying speech sounds, causing an individual to switch to relying on auditory cues that are more available to them to perceive speech.
Young and older adults’ reliance on the duration cue to identify “SET” and “SAT” sounds in quiet (left panel) and in noise (right panel). As the duration of the sound changed from most like “SET” to most like “SAT” (from left to right on the x-axes), participants identified the sound as “SAT” more often (higher up on the y-axis). Steeper slopes of the lines indicate greater reliance on the cue; older adults exhibited significantly steeper slopes for this cue than did young adults, demonstrating that they used this cue to a greater extent than young adults for all sounds presented. Young adults: light blue triangles. Older adults: dark blue circles. Error bars represent +/- 1 standard error of the mean.
This is interesting, as it demonstrates that older adults can adjust their perceptual strategy when particular auditory cues, such as frequency cues, are not useful for them. This ability to change perceptual strategy is crucial for understanding speech in noisy listening environments, situations in which background noise itself reduces the reliability of auditory cues.
Older adults commonly report difficulty understanding speech in background noise, but some individuals experience greater difficulty than others. The results of our research suggest that individual differences in the ability to use auditory cues in noise may contribute to the range of communication challenges experienced by older adults. This study has laid the foundation for continuing research on older adults’ perceptual strategies when listening in background noise.
Mishaela DiNino, Ph.D., is an assistant professor in the department of communicative disorders and sciences at the University at Buffalo. DiNino’s 2020 Emerging Research Grant was generously funded by the Meringoff Family Foundation, which was renewed for a second year in 2023.
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