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 suppress or mask the perceived ringing.
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". Tinnitus maskers increase the level of sound in the listener's environment and therefore mask the ringing in the sufferer's head with a calming, less intrusive sound.
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 maskers are commonly used by tinnitus sufferers when trying to sleep or relax, as it is within these quiet environments that the tinnitus is at its most noticeable. They commonly take the form of CD or MP3 recordings, or bedside noise generators. When used in conjunction with a sound pillow (which contains small embedded speakers) they can mask a person's tinnitus sounds without disturbing his/her partner.
These masker devices use soothing natural sounds such as ocean surf, rainfall or synthetic sounds such as white noise, pink noise, brown noise to help the auditory system to become less sensitive to tinnitus, and promote relaxation by reducing the contrast between tinnitus sounds and background sound.
More advanced software based tinnitus maskers can use a combination of natural and synthetic sounds tailored or a filtered noise generator to mask the specific frequencies at which the tinnitus signal is experienced.
Some sufferers require masking at all times. These people may employ wearable hearing aids which amplify ambient sound, or generate low level wide band sounds such as white noise, or combination devices that mix both functions into one device.
It is widely believed that continued use of tinnitus masking can promote a neurological process known as habituation. This is a physical process which involves neuronal remapping in the auditory cortex of the brain leading to desensitisation of tinnitus.
The promotion of habituation is the key clinical outcome of tinnitus retraining therapy which uses a combination of sound therapy and counselling.
The use of sound in a clinical setting using specialist equipment can be used to completely mask tinnitus in 95% of tinnitus patients. However, it has been argued that it is counter-productive to completely mask tinnitus, as this may prevent habituation. A more effective approach may be to provide sound masking at a level just below the perceived intensity of the tinnitus signal.
See also 
- 'Masking devices and Alprozolam' Vernon J A et al, J or Otolaryngol Clin North Am (2003), 36, 307–320
- 'Tinnitus', McFerran D J et al., J of Laryngology & Otology (2007), 121, 201–208