Hearing Impairment

• Hearing impairment or hard of hearing or deafness refers to conditions in which individuals are fully or partially unable to detect or perceive at least some frequencies of sound which can typically be heard by others.

Classification of Hearing Loss

Hearing impairments are categorized by their type (conductive, sensorineural, or both), by their severity, and by the age of onset. Furthermore, a hearing impairment may exist in only one ear (unilateral) or in both ears (bilateral).

A conductive hearing impairment is an impairment resulting from dysfunction in any of the mechanisms that normally conduct sound waves through the outer ear, the eardrum or the bones of the middle ear.

A sensorineural hearing impairment is one resulting from dysfunction in the inner ear, especially the cochlea where sound vibrations are converted into neural signals, or in any part of the brain that subsequently processes these signals. The vast majority of human sensorineural hearing loss is associated with abnormalities in the hair cells of the cochlea. This dysfunction may be present from birth due to genetic or developmental abnormalities, or arise through trauma or disease during the lifetime of an individual.

Causes of Hearing Loss

Age: presbycusis, the progressive loss of ability to hear high frequencies with increasing age, begins in early adulthood, but does not usually interfere with ability to understand conversation until much later. Although genetically variable it is a normal concomitant of aging and is distinct from hearing losses caused by noise exposure, toxins or disease agents.

Long-term exposure to environmental noise

Genetic

Disease or illness

Medications

Exposure to Ototoxic Chemicals

Physical trauma