The Accuracy of Envelope Following Responses in Predicting Speech Audibility.
Vijayalakshmi Easwar, Jen Birstler, Adrienne Harrison and 2 others
PMID 33136646WHAT IT FOUND
Brain responses to speech sounds were easier to detect for high-frequency fricatives than for vowel stimuli in 21 young adults with normal hearing.
A detected response usually meant the sound was audible; a missing response often did not prove inaudibility.
Key findings
01At the traditional 5% error threshold, Hotelling’s T2 and phase coherence detected EFRs in 68.4% and 68.8% of audible stimuli, while the F-test detected 59.5%; the F-test had higher specificity at 97.3%.
02EFRs evoked by the high-frequency fricatives /∫/ and /s/ were detected significantly more often than EFRs evoked by vowel stimuli when the sound was audible, and /∫/ gave the highest confidence that a missing response meant the sound was inaudible (76%).
03The expected mean sensation level needed to detect an EFR at threshold ranged from 2.3 dB above behavioral threshold for /s/ to 21.7 dB above behavioral threshold for /a/ F1.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only 21 young adults with normal hearing were tested, so the results do not show how EFRs perform in infants or people with hearing loss. The best overall detection rate was 68.8%, so many audible sounds did not produce a detectable response. Specificity comparisons were limited because there were few inaudible samples, especially at higher test levels. The study used modified band-limited phonemes, not full-bandwidth vowels or running speech. The authors state that accuracy in individuals with hearing loss requires additional investigation.
Declared interests
The supplied article text does not include a conflict-of-interest or funding declaration. The publication types list NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not read these results as evidence that EFRs are ready to confirm speech audibility in infants or people with hearing loss. The study tested only 21 young adults with normal hearing, and the best overall detection rate was 68.8%, so many audible sounds did not produce a response.