The causes of deafness can be broadly grouped into conductive problems in the ear canal and middle ear (conductive hearing loss) or sensori-neural problems, which is a problem with the translation of the sound waves into an electrical signal by the inner (sensorineural hearing loss).
A conductive hearing loss can occur due to wax blocking the ear canal, or infection, a collection of fluid, trauma or fixation of the ossicles in the middle ear. Fortunately they can usually be treated.
A sensorineural hearing loss is due to a problem of the inner ear or of the nerve that carries the signal to the brain. There are many causes, the commonest being that of hearing loss in old age (presbyacusis), but other causes include virus infections, trauma, drugs, noise exposure and congenital causes. Some inner ear problems are reversible, but usually loss is permanent. Extremely rarely it may be due to a growth or tumour in the brain.
Hearing aids are continuing to improve and help to amplify the sounds that are heard by the inner ear and so partially overcome the hearing loss.