There are multiple types and degrees of hearing loss. A otolaryngologist is a doctor specialized in diagnosing and treating hearing loss. Often times, the otolaryngologist will refer you to an audiologist, a person specialized in hearing, for a formal evaluation. The audiologists may conduct a hearing test, which they record on an audiogram. Treatment options are often provided based on the type and degree of hearing loss.

There are many causes for hearing loss. Presbycusis, which is hearing loss with aging, is one of the more common reasons for hearing loss. Other causes for hearing loss include loud noise, viral/bacterial infections, heart conditions, strokes, head injuries, tumors, and certain medications. There are many ear conditions that could result in hearing loss including cholesteatoma, chronic otitis media, eardrum perforation, exostoses, Ménière's disease, tinnitus, superior semicircular canal dehiscence, and otosclerosis.

In general, hearing loss can be categorized as conductive, sensorineural, or mixed hearing loss. Conductive hearing loss occurs when sound waves have difficulty traveling through the outer ear canal and the bones of the middle ear. People with conductive hearing loss often complain of a reduction in the volume or ability to hear faint sounds. Sensorineural hearing loss occurs when there is damage to the inner ear or the nerve pathways between the inner ear and the brain.

The degree of hearing loss is classified by the hearing threshold on an audiogram (a graph that shows the softest sounds a person can hear at different pitches or frequencies), and is described in the chart below (World Health Organization):

Abbreviation: dBHLa - Decibel hearing level, as determined in an audiogram