Measurement and Prediction of Binaural-Temporal Integration of Speech Reflections.
Jan Rennies, Anna Warzybok, Thomas Brand and 1 others
PMID 31234732WHAT IT FOUND
Normal-hearing listeners understood speech better when a delayed echo was louder or gave both ears a useful timing cue.
A model that only counted early sounds missed these cases.
Key findings
01With the same timing cue at both ears, the direct-sound-only threshold was -12.0 dB SNR, and thresholds rose to -8.6 dB SNR when a reflection was delayed 150 or 200 ms.
02When the delayed reflection alone carried the useful timing cue, thresholds stayed between -18 and -16 dB SNR across delays, including long delays.
03A model that treated only early sounds as useful failed when a late reflection was much louder than the direct sound; a flexible model predicted all but one condition within 2 dB.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only eight listeners were tested in each part, and all had normal hearing, so the results do not show what happens for patients with hearing loss. The echoes were artificial and presented through headphones in stationary noise, not in real rooms with real furniture, background talkers, or hearing aids. The flexible model used advance knowledge of the noise timing cue, which a listener does not have, so it is not a ready clinical tool. The model parameters were adjusted to match the binaural benefit seen in this listener group and speech material. The American English matrix talker produced lower thresholds than previous material, which may affect how well the model generalizes.
Declared interests
The supplied metadata tags the article as N.I.H. and non-U.S. government research support. The article text provided here gives no author conflict-of-interest declaration.
The easy way to misread this
Do not conclude that delayed echoes or amplified copies will improve hearing for patients. The work used young normal-hearing listeners, artificial reflections, and headphones, and the flexible model needed advance knowledge of the noise timing cue.