Definitions of deaf and hard of hearing are based on the type and degree of hearing loss. Hearing depends on a series of steps that change sound waves in the air into electrical signals. Our auditory nerve then carries these signals to the brain.
First, sound waves enter the outer ear and travel through the ear canal, which leads to the eardrum. Next, the eardrum vibrates from the incoming sound waves and sends these vibrations to the bones in the middle ear. The bones in the inner ear amplify the sound vibrations and send them to the cochlea, a snail-shaped structure filled with fluid, in the inner ear. Hair cells on the cochlea then turn the sound waves into electrical signals carried through the auditory nerve to the brain (National Institute on Deafness and Other Communication Disorders, 2022).
Figure \(\PageIndex{1}\): “Highlighted Anatomy of Inner Ear by Annie Campbell” by dundeetilt is licensed under CC BY-NC-ND 2.0.
Sound is described in terms of loudness and frequency. Loudness refers to the intensity of a sound and is measured in decibels (dB). The larger the dB number, the louder the sound. Zero dB represents the lowest level of sound that a typically hearing person can perceive.
The frequency of sound waves is measured in cycles per second, or hertz (Hz). The ear can detect frequencies from 20 Hz to 20,000 Hz, but most speech occurs in the 200–6,000 Hz range, most occurring between 300 and 3,000 Hz. However, hearing loss can occur at various frequencies, affecting how well an individual hears different sounds. Hearing loss is described in relation to the age of onset. Audiologists may administer a speech reception threshold test to determine an individual’s specific ability to hear and understand speech (Scheetz, 2012; Smiley et al., 2022).
Types of Hearing Loss
The type of hearing loss is often associated with a physiological or neurological problem with the transmission of sound. There are three types of hearing loss, which are described below.
A conductive hearing loss happens when sounds cannot get to the inner ear. This type of hearing loss may be caused by infection, fluid, earwax, or benign tumors or other problems that block access to the inner ear.
A sensorineural hearing loss happens when there is damage to the inner ear. Problems with the nerve pathways from the inner ear to the brain can also cause sensorineural hearing loss. This type of hearing loss may be caused by illness, aging, injury, or genetic predisposition to hearing loss.
A mixed hearing loss is a problem with the outer or middle ear and the inner ear. For example, there may be damage to the outer or middle ear and damage to the inner ear or nerve pathways to the brain. Anything that causes a conductive hearing loss or a sensorineural hearing loss can lead to mixed hearing loss (ASHA, 2022b).
In addition, hearing loss can be unilateral (i.e., affecting only one ear) or bilateral (i.e., affecting both ears), and can be stable or progress over time (Smiley et al., 2022).
Degree of Hearing Loss
Degree of hearing loss is described on a scale from slight to profound and is based on decibels. For example, students who can hear sounds only at 30 dB have a mild hearing loss. Students who can hear only sounds closer to 50 dB have a moderate hearing loss. Table \(\PageIndex{1}\) lists hearing loss classifications.
Table \(\PageIndex{1}\): Hearing Loss Classifications
Degree of Hearing Loss
Hearing Loss Range (dB HL)
Normal
-10 to 15
Slight
16 to 25
Mild
26 to 40
Moderate
41 to 55
Moderately Severe
71 to 90
Profound
91+
Educators and clinicians should keep in mind that the type or degree of hearing loss does not necessarily describe a student’s ability to engage in classroom learning. For example, the student might utilize their residual hearing or use amplification devices to hear the teacher and the other students in the class. A functional hearing assessment is necessary to determine how a student’s learning and communication abilities may be affected (ASHA, 2022a; Smiley et al., 2022).
Age of Onset
Hearing loss may also be described based on age of onset. Students with congenital hearing loss had hearing loss at birth. Students with adventitious hearing loss experienced hearing loss after birth. Prelingual hearing loss occurs before the development of speech and language, and postlingual hearing loss occurs after the development of speech and language. Speech and oral language development may be influenced by age of onset as well as the type and degree of hearing loss. Therefore, hearing loss must be identified early to avoid developmental issues (Smiley et al., 2022). The Joint Committee on Infant Hearing (2007) suggests that “all infants should have access to hearing screening using a physiologic measure at no later than 1 month of age.”
The IDEA Definition
The Individuals with Disabilities Education Act (IDEA) uses the term hearing impairment. Some people in the Deaf community consider this term offensive because it focuses on what a student cannot do. This term should not be used to refer to a student who is deaf or hard of hearing. The IDEA defines deafness and hearing impairment as the following.
Deafness means a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification, that adversely affects a child’s educational performance (IDEA, Part B, Subpart A § 300.8(c)(3)(2004)).
Hearing impairment means an impairment in hearing, whether permanent or fluctuating, that adversely affects a child’s educational performance but that is not included under the definition of deafness in this section (IDEA, Part B, Subpart A § 300.8(c)(5)(2004)).
The ASHA Definition
The American Speech–Language–Hearing Association (ASHA) definitions of communication disorders include the following definition of a hearing disorder.
A hearing disorder is the result of impaired auditory sensitivity of the physiological auditory system. A hearing disorder may limit the development, comprehension, production, and/or maintenance of speech and/or language. Hearing disorders are classified according to difficulties in detection, recognition, discrimination, comprehension, and perception of auditory information. Individuals with hearing impairment may be described as deaf or hard of hearing.
Deaf is defined as a hearing disorder that limits an individual’s aural/oral communication performance to the extent that the primary sensory input for communication may be other than the auditory channel.
Hard of hearing is defined as a hearing disorder, whether fluctuating or permanent, which adversely affects an individual’s ability to communicate. The hard of hearing individual relies on the auditory channel as the primary sensory input for communication (ASHA, 1993).
The Illinois Definition of Deafness and Hearing Impairments
Deafness means a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification, that adversely affects a child’s educational performance.
Hearing Impairments means an impairment in hearing, whether permanent or fluctuating, that adversely affects a child’s educational performance but that is not included under the definition of deafness (ISBE, 2022).
Activity \(\PageIndex{1}\): Compare and Contrast
Directions: Compare and contrast the IDEA, ASHA, and Illinois definitions of communication disorders. Consider the differences and similarities between diagnostic criteria.
Individuals With Disabilities Education Act, Part B, Subpart A § 300.8(c)(3)(2004).
Individuals With Disabilities Education Act, Part B, Subpart A § 300.8(c)(5)(2004).
American Speech–Language–Hearing Association. (1993). Definitions of communication disorders and variations [Relevant Paper]. https://www.asha.org/policy/rp1993-00208/
