Objective Binaural Loudness Balancing Based on 40-Hz Auditory Steady-State Responses. Part II: Asymmetric and Bimodal Hearing.
Maaike Van Eeckhoutte, Dimitar Spirrov, Jan Wouters and 1 others
PMID 30334496WHAT IT FOUND
Brain responses roughly matched loudness balance in asymmetric hearing, but errors were common; in bimodal users they were closer at 500 Hz and less accurate at 2000 Hz.
Key findings
01For asymmetric hearing, brain-response ratios at behaviorally balanced loudness levels were close to 1, but the predicted balance levels were often not within 5 dB of the behavioral levels.
02For bimodal hearing, brain-response estimates were better at 500 Hz than at 2000 Hz, where the median ratio was 1.94.
03The authors state that variability and poor estimates for mid implant channels mean the method needs better understanding before clinical use.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included only nine participants with asymmetric hearing loss and seven participants with bimodal hearing. Behavioral loudness balancing itself was variable, with differences between the two adjustment tracks reaching up to 16 dB. For asymmetric hearing, ASSR prediction errors were common: 37% of data points were within 5 dB and 53% within 10 dB. For bimodal hearing, estimates were poor at 2000 Hz and for mid implant channels. The authors say the cause of the variability is not understood, so the method is not ready for clinical practice.
Declared interests
Funding included Cochlear Ltd and IWT Belgium / Agentschap voor Innovatie door Wetenschap en Technologie. Cochlear Ltd also provided the CI research processor and programming device used for electrical stimulation.
The easy way to misread this
Do not read the close-to-1 median ratios as proof that this brain response can replace behavioral loudness balancing in clinic. The reported errors were large, and the authors say variability and poor mid-channel estimates must be understood first.