gms | German Medical Science

Hearing impairment is highly individual in both its underlying causes and in its consequences. A much-repeated statement is that the audiogram does not contain enough information to characterize a patient’s hearing performance. We have recorded tone detection thresholds in different noise types in 20 volunteers with either age-typical hearing or mild hearing loss. We also measured their speech recognition thresholds in noise. As expected, audiometric thresholds correlated with hearing-in-noise thresholds, but unexplained variance remained. We then added auditory filter bandwidth as a third analysis parameter, derived from the threshold improvement in notched noise. This revealed that audiometric thresholds are correlated with auditory filter width, in line with the correlation between inner- and outer hair cell loss. However, audiometric thresholds did not correlate with the threshold signal-to-noise ratio within the estimated auditory filter. This missing correlation supports the concept of a second orthogonal dimension of hearing impairment, that cannot be mitigated by hearing aid amplification. Elevated within-filter thresholds even occurred in individuals with normal audiometric thresholds but are independent of age. The simplistic characterization allows for new viewpoints on suprathreshold hearing performance. Its potential diagnostic value and consequences for hearing device recommendations and settings will be discussed.