Background: Tinnitus has been associated with altered neural gain mechanisms in the central auditory system, potentially due to reduced peripheral input. Although neural overactivity and gain modulation are well-documented in animal models, their impact on speech-sound processing and perceptual outcomes in humans remains less clear. Investigating both the neural encoding and behavioral discrimination of speech-relevant sounds in listeners with tinnitus can provide insights into how central gain affects everyday auditory function.

Methods: The study included data from 120 participants evenly distributed across six groups: young normal-hearing individuals with and without tinnitus (18–35 years), older normal-hearing individuals with and without tinnitus (45–65 years), and older hearing-impaired individuals with and without tinnitus (45–65 years). The test protocol includes tonal audiometry up to 16 kHz, distortion product otoacoustic emissions, Flemish Matrix sentence test in quiet and in noise, a behavioral psychoacoustic vowel discrimination task (/o/-/u/) in quiet and in noise, frequency following response measurements using vowel /u/ and questionnaires on tinnitus and hyperacusis (TFI, THI, HQ).

Results: While audiometry and DPOAE’s showed no significant differences between the groups, we observed that tinnitus-groups scored overall better on the behavioral vowel discrimination task compared to the control groups. Correspondingly, the young tinnitus group showed stronger neural encoding of the vowel envelope component in the FFR, while no significant group differences emerged for the temporal fine-structure response or in the older cohorts.

Conclusions: These results suggest that tinnitus may be associated with enhanced central encoding of slow temporal envelope cues and improved perceptual discrimination of vowels, consistent with compensatory central gain mechanisms.

Funding: Work supported by FWO G068621N AuDiMod.