Hearing Impairment Defined

The Individuals with Disabilities Education Improvement Act of 2004, formerly the Education of the Handicapped Act (P.L. 94-142), includes “hearing impairment” and “deafness” as two of the categories under which children with disabilities may be eligible for special education and related service programming. While the term “hearing impairment” is often used generically to describe a wide range of hearing losses including deafness, the regulations for IDEA define hearing loss and deafness separately.

Hearing impairment (called auditory impairment in Texas) is defined by IDEA as “an impairment in hearing, whether permanent or fluctuating, that adversely affects a child’s educational performance.”

Deafness is defined as “a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification.”

Thus, deafness may be viewed as a condition that prevents an individual from receiving sound in all or most of its forms. In contrast, a child with hearing loss can generally respond to auditory stimuli, including speech.

Characteristics

There are four major types of hearing loss that are categorized by the site of the disorder in the auditory system. These hearing disorders can be caused by genetic or hereditary factors, infections, developmental abnormalities, or environmental/traumatic factors.

Conductive Hearing Loss is caused by damage or obstruction in the external or middle ear that disrupts the efficient passage or conduction of sound through those chambers. Most conductive losses can be treated medically; however, repeated conductive losses can affect children’s language development.

Sensorineural Hearing Loss is caused by damage to the inner ear (cochlea) or auditory nerve that transmits impulses to the brain. Sensorineural hearing loss tends to be more severe, permanent, and usually affects oral language development.

Mixed Hearing Loss is a combination of both a conductive and a sensorineural hearing loss.

Central Hearing Disorders are the results of a disorder or dysfunction in the central auditory system between the brain stem and the auditory cortex in the brain.

It is useful to know that sound is measured by its loudness or intensity (measured in units called decibels, dB) and its frequency or pitch (measured in units called hertz, Hz). Impairments in hearing can occur in either or both areas and may exist in only one ear or in both ears. Hearing loss is generally described as slight, mild, moderate, severe, or profound, depending upon how well a person can hear the intensities or frequencies most greatly associated with speech. Generally, only children who cannot hear sounds generating less than 90 decibels (dB) are considered deaf for the purposes of educational placement.

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