Effect of Audibility and Suprathreshold Deficits on Speech Recognition for Listeners With Unilateral Hearing Loss.
Tim J M Bost, Niek J Versfeld, S Theo Goverts
PMID 31242137WHAT IT FOUND
For people with unilateral hearing loss, the impaired ear needs more speech information than the good ear to understand words, even when sound is loud enough.
This gap, caused by processing deficits rather than just volume loss, was estimated at 2.1 dB in signal-to-noise ratio.
Key findings
01The impaired ear in unilateral hearing loss requires a higher signal-to-noise ratio to achieve the same speech recognition performance as the unaffected ear, indicating suprathreshold deficits.
02In this study, the estimated contribution of suprathreshold deficits to the speech recognition difference between ears was 2.1 dB SNR, with audibility accounting for the remaining 3.1 dB of the 5.2 dB total difference.
03Speech recognition in the unaffected ear of people with unilateral hearing loss was comparable to that of people with normal hearing, suggesting no compensatory increase in function in the good ear.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used monaural testing, which does not reflect the complex binaural listening conditions of daily life. The sample size for the Speech Intelligibility Index analysis was small (11 participants for the DIN65 condition, 19 for DIN80), which limits the precision of the deficit estimates. The study focused on mild-to-moderate cochlear hearing loss, so results may not apply to those with profound loss or retrocochlear pathology. The digit triplet and CVC word tasks may not fully capture the cognitive load of understanding sentences in real-world conversations.
Declared interests
The authors have no conflicts of interest to disclose.
The easy way to misread this
Do not assume that fitting a hearing aid to the impaired ear will fully restore speech understanding. The study found that suprathreshold deficits, not just volume loss, cause a persistent need for a better signal-to-noise ratio (about 2.1 dB) that amplification cannot fix.