Tinnitus is the sensation of hearing a sound, such as a
ringing or roaring, that does not come from your surroundings (nobody else
can hear it). The sound may be continuous or intermittent, or it may keep
time with your heartbeat. To the person affected with tinnitus, the sound
seems to come from one ear or from somewhere in the head. In rare cases, clicking
or crackling sounds in the ear can be heard by the doctor as well as by the
person with tinnitus.
Normal sounds that come from your surroundings are "heard"
when sound waves strike the eardrum. The eardrum vibrates, and those vibrations
enter the inner ear, where they stimulate nerve cells to create signals that
travel along the acoustic nerve to the brain. The brain then translates the
signals into patterns that you recognize as sounds.
Tinnitus occurs when there is no external source of sound
waves. For reasons that are not understood, the brain receives signals, either
from inside the head or from within the ear, that cause the sensation of hearing
a sound.
Tinnitus is most noticeable (and bothersome) when the affected
person is in a quiet environment. The condition is often treated by using
background noise to mask the ringing or roaring caused by tinnitus.
