By Viji Easwar, Ph.D.
Hearing loss is one of the most common congenital conditions, affecting up to 3 of every 1,000 children born. Although hearing loss can be detected at birth and hearing aids can be fit to improve access to sounds by 2 to 3 months of age, it is very challenging to know whether the hearing aids indeed provide adequate access to speech in order to facilitate speech and language development. This is because babies are too young to do hearing tests until 8 to 10 months of age, and at such young ages, tracking brain waves to sounds is the only reliable way to assess hearing.
Our team—comprising researchers at Western University in Canada, the University of Wisconsin–Madison, and the National Acoustic Laboratories in Sydney, Australia—has been working toward developing novel techniques that can assess access to speech by measuring brain waves.
Speech is a dynamic signal, and our brains tend to follow the changes closely over time to decipher what is being said. Two such speech features that our brains follow are the pitch of voice and the slow rhythm caused by interleaving vowels and consonants in words and sentences.
Until recently, we used voice pitch cues that tend to be the rapid changes in speech (~100 to 400 times/second) to measure access to speech, as we published in Trends in Hearing in March 2023 (and summarized here).
In our most recent study, published in Trends in Hearing in March 2024, we demonstrated the additional utility of using the slow rhythm of speech (~2-8 times/second) to measure access to speech using the same speech tokens that were used to measure voice pitch cues. Accuracy in determining whether or not speech was audible ranged between 80 and 100 percent in children with typical hearing and hearing loss.
This recent progress could allow for a faster clinical test or potentially a more accurate test than what would be possible with using one of the cues.
Our team at the National Acoustic Laboratories, in collaboration with Western University, is continuing to improve the technique, and will soon evaluate the accuracy and efficiency of the novel approach in infants who have just been fitted with hearing aids.
A 2019 Emerging Research Grants scientist funded by the Children’s Hearing Institute, Viji Easwar, Ph.D., is the lead researcher of the pediatric hearing research program at the National Acoustic Laboratories in Sydney, Australia.
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