Hearing loss can come from any part of the ear system; however, hearing loss due to a problem with the inner ear is by far the most common cause.
Excessive build-up of earwax, deformity of the ear canal, a hole in the eardrum or foreign objects. (Now where did I put that bean?)
Fluid behind the eardrum can cause a temporary hearing loss. Otosclerosis or other conditions that cause the chain of three tiny ear bones to not move properly and Cholesteatomas or other types of growths can cause hearing loss, which in some cases is surgically correctable.
Noise exposure, ototoxic medications, and the aging process can permanently damage the nerves of the inner ear. Other causes also include Meniere’s Disease, genetic conditions, illness, head injury, and autoimmune inner ear disease.
Very rarely a tumor on the auditory nerve leading from the inner ear to the brain will cause hearing loss.
FYI: If a hearing loss is due to a problem with the outer or middle ear it is called “conductive hearing loss,” if it is due to a problem with the inner ear or auditory nerve it is called “sensorineural hearing loss” and if the hearing loss is due to a combination of both conductive and sensorineural components it is called a “mixed hearing loss.”