According to the German Tinnitus League (Deutsche Tinnitus-Liga e.V.), approximately three million people in Germany suffer from tinnitus. The effects vary widely: For many people, the phantom sounds disappear on their own after some time. For others, tinnitus causes sleep and concentration problems or even leads to depression.

To date, the cause of ringing, beeping, or hissing in the ears remains unclear. As a result, most treatment methods focus on helping patients learn to live with the noise in their ears. Researchers have now developed a new model that explains tinnitus as a side effect of a mechanism designed to improve hearing.

It has been known for several decades that tinnitus is often associated with hearing loss. Special hearing aids combined with a tinnitus noiser can help counteract the ringing in the ear. The tinnitus noiser masks the disturbing noise with other sounds. Over time, this helps the brain learn to stop focusing on the tinnitus and instead perceive its surroundings.

Researchers have now proposed a new hypothesis regarding how tinnitus might develop: They believe that an additional mechanism—known as stochastic resonance—is involved. Stochastic resonance is a natural phenomenon based on stimulus thresholds that makes it possible to detect weak signals. To do this, noise is added to the signals. When the noise is at the optimal intensity, signal transmission works best.

The human auditory system could use this stochastic resonance to control the noise level via a separate control loop. This monitors the transmission of information from the cochlea to the brain. If necessary, the intensity of the noise is adjusted. As a result, fewer signals reach the human auditory system via the hair cells—for example, following damage to the inner ear.

According to the researchers, stochastic resonance means that hearing loss is at least partially compensated for by background noise. The added noise is perceived as tinnitus. If this is true, the sounds in the ear are no longer merely a pathological malfunction of the hearing system. Rather, they are a side effect of a mechanism that counteracts hearing loss in order to improve hearing performance.

According to an analysis by researchers from the working group at Erlangen University Hospital and the Erlangen ENT Clinic of nearly 40,000 patients with hearing loss, people with tinnitus in the speech-relevant frequency range have lower hearing thresholds than those without tinnitus. On average, the difference was approximately six decibels.

Thanks to this model, entirely new treatment strategies could emerge in the future. For example, several years ago, researchers conducted tests on participants that showed hearing thresholds improve when people are exposed to white noise. This could be one way to counteract tinnitus. This hypothesis has already been confirmed in a study with mice. The human trial is already underway.

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