Sound Therapy Fitting in Hearing Aids

Default sound therapy outputs in hearing aids can vary by as much as 15 dB across different brands, according to a new study. This variability is just one finding from research that measured how these built-in tinnitus management features actually perform and interact with other hearing aid technology. The work, led by researchers Andreea Hajas, Sarah H. Hayes, and Jack Scott, provides clear, objective data to guide clinicians in fitting hearing aids for patients with tinnitus.

How the Study Measured Real-World Performance

The researchers adopted a methodical, two-part approach to evaluate sound therapy in modern hearing aids. They focused on objective electroacoustic measurement, moving beyond manufacturer specifications to see how devices behave in simulated real-world conditions.

For the first part, they selected five popular receiver-in-the-ear hearing aids from different manufacturers. Each device was programmed for two standard audiograms representing different hearing loss profiles. They were tested using both open dome fittings and sealed custom earmolds to account for a common variable in daily practice. Using the CARL manikin and an Audioscan Verifit 2 hearing aid analyzer—tools found in many clinics—they measured the actual output of the default sound therapy signals.

The second part of the study investigated interference. The team specifically tested how the sound therapy feature interacted with two other standard digital signal processing (DSP) features: feedback cancellation and noise reduction. They measured whether activating therapeutic sound triggered feedback or was affected by automatic noise management algorithms.

Brand Variability and Feature Conflict Are the Norm

The results revealed significant inconsistencies. The output level of the default sound therapy signal was not standardized. A setting labeled “medium” on one brand’s software could be much louder or quieter than the same setting on another brand’s device. This variation was primarily dictated by the user’s specific audiogram and whether they used a dome or an earmold. A dome fitting, which allows more environmental sound in, often resulted in a higher sound therapy output from the device to compensate, while a sealed earmold produced a different output profile.

More critically, the study documented direct technical conflicts. When the sound generator was activated, it frequently caused the hearing aid to exceed its pre-set stable gain limit. This triggered the feedback cancellation system, often resulting in audible whistling that would be bothersome to the user. This finding indicates that fitting a hearing aid for amplification alone does not guarantee it will remain stable when therapeutic sound is added.

A second conflict arose with noise reduction. In open-fit configurations, the hearing aid’s algorithm designed to suppress background noise sometimes misinterpreted the constant sound therapy signal as unwanted noise. Consequently, the system would automatically turn the therapeutic sound down, undermining its intended purpose. This interaction would be invisible to both the clinician and patient without proper verification.

Practical Implications for Clinicians and Patients

The core conclusion is that verification is non-negotiable. “These interactions are measurable using standard clinical verification tools,” the authors state, highlighting that clinicians already have the equipment needed to check for these problems. Relying on manufacturer defaults or software presets without verification can lead to a suboptimal or even counterproductive fitting for tinnitus management.

Based on their evidence, Hajas, Hayes, and Scott proposed five clinical fitting practices. While the full protocols are detailed in their paper, the principles include verifying sound therapy output in the specific coupling to be used, checking for feedback with the sound generator on, and ensuring noise reduction features do not attenuate the therapeutic signal. This proactive fitting process helps ensure the patient receives a consistent, intended sound level that can effectively support tinnitus management strategies.

For patients, this research underscores the importance of working with a clinician who performs real-ear measurement and verification. It also explains why a hearing aid might whistle when tinnitus sounds are turned on or why the soothing sound might seem to fade in and out in noisy places. Understanding these are known technical issues, not a fault of the patient’s hearing or the device being “broken,” is important. For those with complex conditions like hidden hearing loss or misophonia, where sound tolerance and precise auditory input are critical, such precise fitting is even more vital.

A Call for Standardization and Informed Fitting

This study moves the conversation about sound therapy from theory to measurable practice. It demonstrates that the digital ecosystems within modern hearing aids are complex, and features do not operate in isolation. The findings call for greater transparency from manufacturers and potentially, industry-wide standards for sound therapy output levels.

Ultimately, the research empowers clinicians with evidence. By using verification protocols, they can navigate brand variability and internal feature conflicts to deliver reliable, effective sound therapy. This objective approach helps ensure that hearing aids fulfill their dual promise of improving hearing and providing a solid foundation for tinnitus management.

Source: Hajas, A., Hayes, S.H., & Scott, J. (2026). Objective Identification of fitting and programming considerations for sound therapy in hearing aids based on electroacoustic characterization across brands. Frontiers in Audiology and Otology. DOI: 10.3389/fauot.2026.1861736.