By Viji Easwar, Ph.D.
Children frequently need to communicate in environments that have distracting noises and echoes. These environments are a major problem for children, particularly for those with hearing loss who are mainstreamed in classrooms with typically developing children. They have a harder time understanding speech in noisy or echoey environments, even when they use hearing aids.
Factors like vocabulary size and working memory have been known to facilitate speech understanding in noise. However, little was known until recently about the role of sound processing in the brain that may make speech understanding more difficult for some children than others.
This image shows the waveforms and spectra (visual representations of sound frequencies) of the different audio stimuli the researchers used to compare and analyze their characteristics. Credit: Easwar et al./Ear and Hearing
In our most recent study, we set out to examine how children’s brains process one specific part of speech: the fundamental frequency of a person's voice, which is essentially the basic pitch heard when someone speaks.
To do this, we measured brain responses to vowels in 14 children with hearing loss wearing hearing aids similar to how they would be fit clinically and 29 children with typical hearing in multiple conditions. One was clean (quiet conditions) and three were difficult conditions that reflected the presence of noise, echoes and both noise and echoes. In the same four conditions, we also measured children’s ability to identify speech sounds.
As published in the July/August 2024 issue of Ear and Hearing, we found that among children with hearing loss, their ability to process lower-pitched sounds was linked to how well they could understand speech in the most challenging conditions (both noisy and echoey).
These findings show that even with appropriate amplification via hearing aids, children with hearing loss still have trouble processing certain aspects of sound, particularly the basic pitch of voices. These objectively measurable brain responses may explain why children with hearing loss struggle more in noisy or echoey environments.
This study is one of four studies completed by my lab at the University of Wisconsin–Madison, aimed at using brain responses to evaluate how well children with hearing loss hear with and without hearing aids and what factors contribute to their speech understanding abilities.
Viji Easwar, Ph.D, is a 2019 Emerging Research Grants (ERG) scientist generously funded by the Children’s Hearing Institute. She is currently the lead of the pediatric hearing research program at the National Acoustic Laboratories in Sydney, Australia. One of the study’s coauthors is Z. Ellen Peng, Ph.D., a 2020 and 2022 ERG scientist generously funded by Royal Arch Research Assistance.
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