Spectral and binaural loudness summation for hearing-impaired listeners.
Level 4 - case-series / case-control
Small comparative laboratory psychophysical study
PubMed 27006003 · doi:10.1016/j.heares.2016.03.010
What was done
Categorical loudness scaling was measured in 9 normal-hearing (NH) and 10 hearing-impaired (HI) listeners for signals of varying bandwidth and spectral shape in monaural and binaural conditions. Frequency- and level-dependent amplification was applied to HI listeners to match the narrowband monaural loudness perception of NH listeners.
What was found
Monaural broadband loudness functions showed good agreement between NH and HI groups after narrowband compensation. However, for binaural broadband signals, HI listeners perceived sounds as substantially louder than NH listeners at comparable levels above "medium loud": on average, HI listeners required a 14.1 dB lower sound level (range: -3.7 to 30.8 dB) to reach the "very loud" category. Exaggerated binaural summation did not occur for narrowband signals or at categories below "medium loud". Large individual variation was observed that was not accounted for by audiograms or narrowband loudness functions.
Why it matters
Standard hearing aid fitting strategies that restore narrowband monaural loudness can cause broadband everyday sounds to become uncomfortably loud when heard through both ears. Hearing aid algorithms may need specific binaural gain corrections for loud broadband inputs.
Limits
The sample was small (10 hearing-impaired and 9 normal-hearing participants), limiting statistical power and generalizability across diverse hearing loss etiologies. The study evaluated laboratory psychophysical stimuli rather than real-world speech or complex acoustic environments, and the underlying mechanism for the large individual variability remains unexplained.
Cited by
- supports Hearing loss commonly reduces the dynamic range of hearing, making quiet sounds inaudible while louder sounds quickly become uncomfortable or painful.