Hidden Hearing Loss: Audiology and Tinnitus Research

A scoping review of 29 studies has found that noise exposure leads to measurable dysfunction in both the peripheral and central auditory systems in people with hidden hearing loss. The work, led by researchers Meliha Başöz Behmen, Merve Kaygusuz, and Elif Kuru, consolidates evidence on how to detect this elusive condition, where standard hearing tests appear normal despite real-world listening difficulties.

How Researchers Compiled the Evidence on Hidden Hearing Loss

The team conducted a systematic scoping review following established Joanna Briggs Institute and PRISMA-ScR guidelines. They searched two major databases, PubMed and ScienceDirect, for English-language studies published between 2010 and 2023. The search focused on the terms “hidden hearing loss” and its biological correlate, “cochlear synaptopathy.” From this pool, they identified and included 29 studies involving adult participants. The analysis synthesized results from standard audiological test batteries alongside more specialized psychophysical and perceptual assessment methods. The full methodological details are available in the published review (DOI: 10.5152/b-ent.2026.251978).

High-Frequency Threshold Shifts Signal Early Noise Damage

A primary finding challenges the notion that a “normal” audiogram means a healthy ear. The review indicates that in populations at risk for hidden hearing loss—such as people with significant noise exposure or tinnitus—even a mild elevation of hearing thresholds at high frequencies (e.g., 8-16 kHz) is meaningful. This subtle shift is associated with the early effects of noise exposure and acts as a preliminary red flag for auditory impairment long before it affects the standard speech-frequency range. It suggests clinicians should pay closer attention to the extreme ends of the audiogram in at-risk patients.

Physiological Tests Reveal the Neural Breakdown

Where the audiogram falls short, electrophysiological tests show clear abnormalities. The evidence from the 29 studies is consistent: noise exposure causes a significant decrease in the amplitude of Wave I in the auditory brainstem response (ABR). Wave I is generated by the cochlear nerve, so a smaller amplitude strongly indicates a loss of synaptic connections between inner hair cells and auditory nerve fibers, the hallmark of cochlear synaptopathy.

Another test, electrocochleography (ECochG), provides supporting data. Researchers see a decrease in the action potential (AP) amplitude on ECochG, along with an increase in the ratio between the summation potential (SP) and the AP. These combined electrical changes further help in assessing the integrity of the initial neural response in the cochlea.

Noise Disrupts the Entire Auditory Pathway

The review moves beyond the cochlea to confirm that the impact of noise is system-wide. The conclusion states that noise exposure leads to dysfunction in both the peripheral and central auditory systems. Peripheral damage, like synaptopathy, reduces the clarity and amount of sound information sent to the brain. The central auditory system, which must decode this degraded signal, can become overworked or maladapted. This central dysfunction is a likely contributor to the classic symptoms of hidden hearing loss: struggling to understand speech in noisy environments and the perception of tinnitus, which may arise from the brain’s attempt to compensate for lost input.

This model of combined peripheral and central disruption provides a useful framework for understanding related conditions. For instance, the neural hypersensitivity seen in misophonia may share pathways with the central changes triggered by the degraded signals of hidden hearing loss.

Practical Implications for Patients and Clinics

For individuals, the most critical implication is preventative. The finding that high-frequency threshold shifts are an early warning reinforces the absolute necessity of using effective hearing protection in loud environments to preserve both cochlear function and neural integrity.

In clinical practice, this review supports the adoption of a more nuanced test battery for patients who report hearing difficulties despite a normal audiogram. Referral for an ABR test to measure Wave I amplitude or an ECochG could provide objective evidence of cochlear synaptopathy. Recognizing hidden hearing loss as a valid diagnosis is the first step toward management, which may include auditory training, counseling, and technology like programmable sound therapy devices designed to address both peripheral deficits and central tinnitus.

Ultimately, the work by Başöz Behmen and colleagues moves hidden hearing loss from a theoretical concept to a measurable condition. By defining its electrophysiological signatures, they provide the tools needed for better detection, clearer patient communication, and a stronger foundation for future treatment development.