Tinnitus masker sensation level (SL), is how much louder the tinnitus is above the ambient noise of the environment. By raising the ambient level of noise (playing white noise into the ear), the apparent loudness of tinnitus is reduced. The noise level is close to and usually somewhat louder than the perceived loudness of the tinnitus. The generated noise is designed to be a calming, less intrusive sound than the ringing or hissing of tinnitus. Depending on the loudness of the noise, tinnitus may be fully or partially masked. Tinnitus masking cannot reduce or eliminate tinnitus, only reduce awareness of it. The
Tinnitus retraining therapy large proportion of dropouts; reported 'success' ratios may not take these subjects into account. There are few available studies, but most show that tinnitus naturally declines over time (years) in a large proportion of subjects surveyed, without any treatment. The annoyance of tinnitus also tends to decline over time. In at least some, tinnitus spontaneously disappears. A Cochrane review found only one sufficiently rigorous study of TRT and noted that while the study suggested benefit in the treatment of tinnitus, the study quality was not good enough to draw firm conclusions. A separate Cochrane review of sound therapy (though they