Hearing loss can result from an obstruction or damage in any of the three parts of the ear. Types of hearing loss Hearing loss resulting from a problem located in the outer or middle ear is called a conductive hearing loss. A hearing loss caused by a damaged inner ear is called sensorineural. This is the most common hearing loss. Should the loss be the result of a combination of these, this is known as a mixed hearing loss.
The ear - a highly complex organ.

Possible causes of hearing loss in....

...the outer ear
Typical problems include excessive accumulation of earwax and infection of the auditory canal.

...the middle ear
Perforation of the eardrum, infection and otosclerosis (a calcification around the stapes limiting its ability to move) are the most common causes. Many outer and middle ear problems can be treated successfully with medication or surgery. Should this not be the case, remaining hearing loss can usually be helped by using hearing instruments.

...the inner ear
The majority of hearing problems result from damaged inner ear structures. Typical causes are the natural ageing process, excessive exposure to noise, medication that is toxic to the auditory system and head injuries. In such cases the tiny hair cells in the cochlea are damaged, obstructing the transfer of sound signals to the brain. As a rule this damage cannot be reversed medically. However, well-fitted hearing instruments can usually help a great deal to overcome the resulting problems.

Tinnitus
Tinnitus is the sensation of ringing or other sound in the head. It may occur in conjunction with a hearing loss. The causes of tinnitus are as varied as those of hearing loss and the cause may not be evident in the individual case.