This study investigates a new type of auditory evoked brain potentials for the quantification and classification of peripheral hearing damage (The CochSyn Test). The study will investigate the characteristics of this new auditory evoked potential marker in a cohort of people with and without self-reported hearing difficulties and test a new type of hardware that was developed to conduct the test (the CochSyn Device) in clinical practice.

Cochlear synaptopathy (CS) is a new type of sensorineural hearing loss (SNHL) and is related to ageing, noise exposure and ototoxicity. There is currently no diagnostic test of CS on the market, whereas CS is an important form of SNHL. CS occurs before the golden standard clinical hearing test (pure- tone audiogram in which participants raise their hand when hearing tones of different frequencies and the threshold of hearing is determined), shows any signs of hearing damage.

The sponsor has developed a new test, the CochSyn test that may quantify SNHL earlier than the audiogram. The newly developed test is based on auditory evoked potentials. This is a method in which an auditory stimulus is presented, and encephalogram (EEG) electrodes capture the sound-evoked brain potentials. The most popular auditory evoked potential metric to diagnose sensorineural hearing loss (SNHL) is the auditory brainstem response (ABR). Even though it can be assumed that the ABR wave-I amplitude will be sensitive to CS in humans, it may not be a differential marker for it, and hence other candidate auditory evoked potential markers for CS have been investigated. In particular, the envelope-following-response (EFR), has also been shown to be specific to CS.

The sponsor has performed several research studies on the CochSyn test that used commercially available research equipment in either humans or research animals . These data show that our marker is sensitive to ototoxic-induced CS in research animals and demonstrates an age-related decline in humans, and a superiority in terms of test-retest reliability and sensitivity compared to clinical ABR wave-I, or other evoked potential, markers. These promising data, the lack of a method to identify CS and the lack of commercially available hardware to conduct the CochSyn test in a clinical setting motivate the need for the development of the CochSyn test and device.

In this study, the sponsor wish to test the performance of its new method (the CochSyn test) in listeners with or without self-reported hearing difficulties using a newly developed hardware prototype (the CochSyn device), dedicated for the CochSyn test in clinical practice.

Inclusion Criteria:

• Age 18-77 years (limits included)

• Ability to fill out a questionnaire and to perform a speech intelligibility test

• Dutch or French as native language

  • Control group

• No self-reported hearing difficulties according to HHIE-s questionnaire (score of ≤4)

  • Test group

• Self-reported hearing difficulties according to HHIE-s questionnaire (score of >4)

  • Subgroup DFNA9:

• Genetically tested and confirmed to have DFNA9 related hearing loss. Note: This genetic testing was performed through standard of care testing, prior to participation in the study.

Exclusion Criteria:

• Audiometric hearing loss classifications of Moderate, Moderately severe, Severe, Profound as defined by (Clark, 1981) of the tested ear
• Asymmetrical hearing loss Note 1: Asymmetrical hearing loss is defined as an average difference of more than 15dB between both ears across the frequencies of 500, 1000, 2000 and 4000 Hz. The sum of loss in dB is divided by 4 and rounded up. A frequency not perceived is considered a loss of 120 dB.

Note 2: This exclusion criterium is not applicable for the DFNA 9 subgroup

• Tinnitus with a clinical handicap index (TFI) > 25.
• Patients with type AD, AS, B or C tympanograms
• Conductive hearing loss on the tested ear at the discretion of the investigator
• Genetic hearing loss of the tested ear Note: This exclusion criterium is not applicable for the DFNA9 subgroup.
• Congenital hearing loss of the tested ear Note: This exclusion criterium is not applicable for the DFNA9 subgroup.
• Blocked ear canal(s) of the tested ear
• Pregnant or breast-feeding
• Hearing aid user on the tested ear
• Middle ear surgery on the tested ear
• Acute ear infection of the tested ear
• Acute external auditory canal trauma on the tested ear
• Participation in session 2 of previous clinical trial NCT06114680