Sound Therapy Fitting and Verification Tips

Default sound therapy outputs in hearing aids can vary by as much as 15 dB across different brands. This finding comes from a new study that used standard clinical tools to measure how hearing aid features interact, revealing that these interactions can sometimes work against the patient’s goals.

How Researchers Measured the Interactions

Andreea Hajas, Sarah H. Hayes, and Jack Scott wanted to see how sound therapy interacts with other hearing aid features. They tested five different receiver-in-the-ear hearing aids from major manufacturers. To simulate real-world conditions, they used a manikin system (the CARL manikin) and a standard hearing aid analyzer (Audioscan Verifit 2).

The devices were programmed for two common types of hearing loss. The team also tested each device with two coupling methods: a standard dome and a custom earmold. This approach allowed them to measure the pure electroacoustic output of the sound therapy feature in isolation and then observe what happened when other features like feedback cancellation and noise reduction were switched on.

Brand Variability and Coupling Effects Dominate Output

The first major finding was inconsistency. With sound therapy activated at its default setting, the actual sound output measured at the eardrum differed widely across the five brands. A user’s specific audiogram and whether they used a dome or a custom mold were the primary factors influencing this output.

This means two patients with similar tinnitus but different hearing aids could receive markedly different levels of therapeutic sound, even if their audiologist selected the same nominal setting. This variability underscores why verified, personalized fitting is so important, as generic programming is unlikely to meet individual needs.

Sound Therapy Can Trigger Audible Feedback

A more concerning interaction was with feedback cancellation systems. Hearing aids have a maximum amount of stable gain they can provide before they begin to whistle. The study found that enabling the sound generator often consumed a large portion of this “headroom.” In many test scenarios, activating sound therapy pushed the device past its stable limit, causing immediate and audible feedback.

For a patient, this could mean their hearing aid starts to whistle as soon as they turn on their tinnitus relief sounds, a frustrating and counterproductive experience. It highlights a direct conflict between two standard features designed to improve the user’s experience.

Noise Reduction May Quiet the Wrong Sounds

The third key interaction involved noise reduction algorithms. These features are designed to identify and reduce steady-state background noise to improve speech clarity. The researchers found that in open-fit configurations (using domes), the noise reduction systems frequently misclassified the steady therapeutic sound as “noise” and reduced its level.

Essentially, the hearing aid’s left hand was turning down the volume of the sound its right hand was producing for therapy. This could make the sound therapy ineffective without the user or clinician realizing why.

Verification in the Clinic is Non-Negotiable

The central message of the study is that these interactions are not hidden or theoretical. They are measurable with the verification equipment found in most audiology clinics. Relying on manufacturer defaults or programming hearing aids without verifying the real-ear output is a gamble.

The authors argue that post-fitting verification should be a mandatory step for any patient using sound therapy. This practice aligns with findings from studies on audiologist-delivered tinnitus management, where structured, verified protocols lead to better patient outcomes. The research team translated their findings into five specific clinical fitting practices to help audiologists systematically check for and prevent these issues.

Connections to Broader Hearing Health

These findings resonate beyond tinnitus management. For individuals with conditions like hyperacusis or sound sensitivity often reported in autistic adults, precise control of sound output is critical. An unpredictable or self-contradicting hearing aid could worsen anxiety rather than alleviate it.

The study also reflects a broader principle in managing chronic auditory conditions: effective treatment depends on precise, verified technology. Just as baseline factors predict outcomes in cognitive behavioral therapy for insomnia, the baseline electroacoustic performance of a device predicts its success in sound-based therapy. A hearing aid must be a reliable tool, and this research provides a clear method for clinicians to ensure it is.

The work by Hajas and colleagues, published with the DOI 10.3389/fauot.2026.1861736, provides a practical, evidence-based roadmap for improving the reliability of sound therapy in modern hearing aids.