Potential Consequences of Spectral and Binaural Loudness Summation for Bilateral Hearing Aid Fitting.
Maarten van Beurden, Monique Boymans, Mirjam van Geleuken and 3 others
PMID 30353784WHAT IT FOUND
Hearing-impaired listeners perceived broad binaural sounds as louder than normal-hearing listeners after narrowband loudness normalization.
Audiogram type and monaural tests did not predict individual loudness summation, so bilateral hearing aid fitting rules with fixed gain reductions may not capture individual loudness needs.
Key findings
01After narrowband loudness normalization, hearing-impaired listeners perceived broad binaural signals as louder than normal-hearing listeners.
02The audiogram classification and monaural loudness measures did not predict individual binaural loudness summation.
03Individual binaural loudness summation for broadband input signals was higher than 30 dB, while NAL-NL2 proposes bilateral gain reductions of 2 to 6 dB.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study included only seven listeners with steep sloping audiograms, and they were combined into one group. The normal-hearing reference group was nine listeners from an earlier study, not measured in this experiment. The loudness ratings were laboratory psychoacoustic measurements, not hearing aid fitting outcomes or patient comfort. Narrowband loudness compensation was limited to 105 dB HL, so some listeners may not have been fully compensated. The measured level differences depend on the six-channel compressor, the headphone setup, and the categorical loudness scaling procedure. The authors state that implications for hearing aid fitting require further research.
Declared interests
The supplied text names the Heinsius Houbolt fund as funder. It does not report author conflicts of interest in the supplied text.
The easy way to misread this
Do not use the 30 dB figure as a standard bilateral gain correction. The study measured loudness summation in a laboratory, and individual results varied so widely that the audiogram class and monaural tests did not predict them.