Hearing loss: Probably the most common cause for tinnitus is hearing loss. As we age, or because of trauma to the ear (through noise, drugs, or chemicals), the portion of the ear that allows us to hear, the cochlea, becomes damaged. Current theories suggest that because the cochlea is no longer sending the normal signals to the brain, the brain becomes confused and essentially develops its own noise to make up for the lack of normal sound signals. This then is interpreted as a sound, tinnitus. This tinnitus can be made worse by anything that makes our hearing worse, such as ear infections or excess wax in the ear.
Atherosclerosis. With age and buildup of cholesterol and other deposits, major blood vessels close to your middle and inner ear lose some of their elasticity — the ability to flex or expand slightly with each heartbeat. That causes blood flow to become more forceful, making it easier for your ear to detect the beats. You can generally hear this type of tinnitus in both ears.