Tinnitus masking

Tinnitus maskers are a range of devices based on simple white noise machines which are used to add natural or artificial sound into a tinnitus sufferer's environment in order to mask or cover up the ringing. The noise is supplied by a sound generator which may reside in or above the ear or be placed on a table or elsewhere in the environment. The noise is usually white noise or music, but in some cases it may be patterned sound or specially tailored sound based on the characteristics of the person's tinnitus.

The perceived loudness of tinnitus, called 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 efficacy of a tinnitus masker may depend on the wearer's capacity to experience residual inhibition, the temporary suppression of tinnitus in response to particular sound patterns.

The mechanism of sound masking can be explained by analogy with light. In a dark room where someone is turning a lamp on and off, the light will be obviously noticeable. However if the overhead lights are turned on, turning on the lamp will no longer be as distracting because it has been "masked".

The concept that an external sound could suppress perception of an internal one was first realised clinically in the mid 1970s by Dr. Jack Vernon, when he reported that white noise was effective in alleviating tinnitus.

Tinnitus suppression is different than but related to tinnitus masking. It is an acoustic or neurological effect that results in temporary suppression of tinnitus by listening to an appropriately tailored sound for a short period. After the sound is withdrawn, tinnitus may be fully (complete silence) or partially suppressed. Most (70-90%) of persons can experience the effect. There is usually a period of complete silence followed by a gradual return of tinnitus to its original level. The effect lasts for 5 minutes or less in 90% or persons but in rare cases, an hour or more. The period of complete silence is usually seconds to about a minute. If the trigger sound is repeated at intervals, tinnitus can be suppressed as long as the repetition lasts.

The residual inhibition (RI) effect first noted in 1903: the capacity of a sound of the right frequency and intensity to briefly attenuate or suppress tinnitus. To distinguish the tailored sound used for inhibition from the broadband undifferentiated sound employed in tinnitus maskers, it is usually referred to as the 'trigger' or 'quieting' sound. The trigger sound is closely matched to the pitch and spectrum of the tinnitus, and as loud or somewhat louder than the perceived loudness of the tinnitus. The trigger sound is applied to the ear or ears with tinnitus and typically lasts a minute or two. Not everyone can experience RI; for those who do not, tinnitus masking is likely to be ineffective.

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Wikipedia