There are a number of causes of tinnitus, ranging from genetic types of hearing loss to muscle spasms to medications.
Subjective tinnitus is more common, and is often associated with hearing loss.
The most common causes of the hearing loss are noise exposure or presbycusis, the hearing loss that comes with age. These people often have high-frequency hearing loss, and the sound they hear is usually at the same frequency where their hearing is the worst. Some injuries may cause tinnitus, and aspirin is a well-known cause. Other medications can also cause tinnitus, and some doctors may recommend that a person with tinnitus also quit smoking and avoid caffeine. With objective tinnitus, a person is actually hearing another part of their body, such as blood vessels which can produce a throbbing sound, or a muscular contraction of the palate which can produce clicks.