Usually two definitions are used: "hearing impairment" and "deafness" as two categories under which children may be eligible for special education.

Hearing impairment is „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 a hearing loss can generally respond to auditory stimuli, including speech. The latter category also is addressed as “Hard-of-hearing”. Very generally said : a child that is Hard-of-hearing can –with or without the help of an hearing aid- mainly rely on the audible information, a deaf child –also with or without any hearing aid- mainly depends on the visible transfer of information like speech-reading, signing, written language.

Sound is measured by its loudness or intensity (measured in decibels, dB) and its frequency or pitch (measured 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. Children whose hearing loss is greater than 90 decibels (dB) are considered deaf for the purposes of educational placement.

There are four types of hearing loss. Conductive hearing losses are caused by diseases or obstructions in the outer or middle ear (the conduction pathways for sound to reach the inner ear). Conductive hearing losses usually affect all frequencies of hearing evenly and do not result in severe losses. A person with a conductive hearing loss usually is able to use a hearing aid well or can be helped medically or surgically.

Sensorineural hearing losses result from damage to the delicate sensory hair cells of the inner ear or the nerves which supply it. These hearing losses can range from mild to profound. They often affect the person's ability to hear certain frequencies more than others. Thus, even with amplification to increase the sound level, a person with a sensorineural hearing loss may perceive distorted sounds, sometimes making the successful use of a hearing aid impossible.

A mixed hearing loss refers to a combination of conductive and sensorineural loss and means that a problem occurs in both the outer or middle and the inner ear. A central hearing loss results from damage or impairment to the nerves or nuclei of the central nervous system, either in the pathways to the brain or in the brain itself.

Hearing loss or deafness does not affect your child’s intellectual capacity or ability to learn. However, children who are either hard of hearing or deaf generally require some form of special education services in order to receive an adequate education.

Nowadays Cochlear Implantation, a medical-technical solution, is possible: a hearing device placed under the skin that enables direct electrical stimulation of the hearing nerve circuit. When adapted and trained successfully it can help to overcome the inaccessibility of sound, especially of spoken language.

In this section you will find pages about specific topics on Deafness and Hard-of-hearing and links to relevant other websites.