Almost everyone with tinnitus has the experience that their tinnitus is worse when they're in a quiet room, and most will also be aware of some sounds that make their tinnitus more difficult to hear. However, the interaction between an external sound and tinnitus is not a simple one. The complex relationship is because tinnitus exists even when no external sound is present, and it appears to be coded, at least in some ways, unlike external sounds. Tinnitus isn't caused by physical sound vibrations; instead it's the brain's picture of a sound. Tinnitus does not obey all the rules which normally apply to listening to an external sound (Tyler, 2000). For example, tinnitus may be difficult to mask (cover) even with very loud sounds close to the pitch of the tinnitus. The unusual way that sound interacts with tinnitus means that sound therapy isn't as simple as covering one sound with another.

Sounds can evoke a wide range of responses in a person, including emotional reactions, muscle contractions and change in heart rate. When sound is being used to defeat tinnitus, it's important that the positive effects of sound are being promoted and any negative effects are minimized. It serves little purpose to replace tinnitus with a more annoying sound. In this chapter I'll introduce some of the principles surrounding the use of sound to treat tinnitus and, in addition, various “sound” or “acoustic” therapies and the devices developed to implement these treatments.

Attention and Distraction
“Learning to ignore things is one of the great paths to inner peace.”
R.J. Sawyer

Sound is used in many tinnitus therapies to distract attention away from tinnitus and to reduce the brain’s ability to fully process tinnitus activity. In our daily activities a mixture of sounds reaches our ears and the auditory system needs to choose the relevant sounds from the background noise. For normal hearing we must ignore irrelevant information so that we don't become distracted, but we must also be able to hear and react to important (potentially dangerous) events which we're not focusing on. For example, while crossing the street conversing with someone, we need to react to the sound of an ambulance siren. If we don’t, we end up needing the ambulance (or worse)! It appears that the brain’s attention is attracted to tinnitus as if it was an important sound. Have you ever noticed how you can hear your name above the background noise babble at a party? Tinnitus seems to have the same attention-capturing characteristics. The effect of tinnitus is partly dependent upon the attention given to it. A decrease in attention to tinnitus through distraction should lead to its reduction. This distraction can be achieved using tactics such as searching for and identifying sounds other than tinnitus. Henry and Wilson, two Australian psychologists, suggested some simple attention strategies can be applied easily for this purpose (Henry & Wilson, 2002).