Once the referral to the appropriate professional has been made, an audiological examination is performed. An audiological examination is conducted by an audiologist to determine:
- if a hearing loss is present;
- which tones are affected;
- the degree of the hearing loss;
- the type of hearing loss (i.e. conductive, sensorineural, or mixed);
- the best method of treating the hearing loss; including selection of an appropriate hearing aid, if appropriate.
The audiologist begins the examination of the child by first taking a case history. The audiologist asks questions about the child’s medical conditions, hearing behaviors, hearing loss in the family, and any concerns of the child and the family.
The audiologist then performs several tests in order to obtain an accurate measure of the child’s hearing abilities to determine the existence and extent of the hearing impairment.
When these tests have been completed, the audiologist may conduct more specialized procedures, such as the evaluation of the mechanical functioning of the eardrum and bones of the middle ear (“intermittence teats”), and other measures to assess the function of the cochlea. Alternatively, if deemed necessary, the audiologist will make referrals to other professionals.
After reviewing the child’s information and test results, the audiologist will be able to describe a hearing loss as unilateral (affecting one ear) or bilateral (affecting both ears), the degree of hearing impairment (mild, moderate, severe or profound), and the type of loss (conductive, sensorineural or mixed). The audiologist will make recommendations regarding amplification and provide suggestions on how to best manage the hearing impairment. It is important to remember that every student is an individual and as Scheetz (2000) emphasizes, “One must be careful not to pigeonhole or label someone based on this information” (p. 52). To help the student we need to then individualize the supports that we provide by consulting with other professionals.
Below is information about some of the tests that are performed to assess hearing. They include:
- Otoscopy. Otoscopy is a physical examination of the ear that involves looking into the ear with an instrument called an “otoscope” (or “auriscope”) to examine the structures of the outer ear and the eardrum. Otoscopy can help detect problems such as a hole (perforation) in the eardrum and infections of the middle ear (such as acute Otitis Media, an infection that produces pus, fluid, and inflammation within the middle ear). The nose, nasopharynx (space within the skull that is above the roof of the mouth, and behind the nose), and upper respiratory tract are also examined.
- Tympanometry. Tympanometry measures the ability of the middle ear to conduct sound. It is particularly useful in detecting fluid in the middle ear; Eustachian tube dysfunction (such as negative middle ear pressure); disruption of the ossicles (bones); tympanic membrane (ear drum) perforation; and otosclerosis (abnormal growth of bone in the middle ear). To perform this test, a soft probe is placed into the ear canal and a small amount of pressure is applied. The instrument then measures mobility of the tympanic membrane and its response to the pressure changes. The results of the test are printed as a graph, called a “tympanogram” which can help identify middle ear problems. For example, a flat line on the tympanogram may indicate that the eardrum is not mobile or not vibrating properly due to fluid in the middle ear (Hain, 2002).
Audiometry is the testing of a person’s ability to hear sounds at a range of frequencies. This includes air conduction tests, bone conduction tests, and speech audiometry tests. An audiometric test is used to determine the types of sounds the child can and cannot hear.
Air conduction tests involve the presentation of beeps and whistle-like sounds, called “pure tones,” through headphones in a soundproof room. Sounds are of varying loudness (intensity measured in dB) and of different pitch (or frequencies measured in Hz) The pure tones go via the air, down the ear canal, through the middle ear into the inner ear. The child is asked to respond when he or she detects a sound (such as by raising a hand or pushing a button). The loudness of each tone is reduced until the child can just hear the tone. The softest sounds the child can hear constitute the hearing threshold. This is marked on a graph called an “audiogram,” which can be used to identify and diagnose hearing impairment (Martin & Clark, 2003).
A bone conduction test involves using a skull vibrator such as a vibrating tuning fork. It is placed behind the ear to measure the softest sounds that the child can hear to test the functioning of the inner ear. The child is asked to respond when detecting a sound produced by the device. As the sound travels through the bones of the skull to the inner ear (cochlea, auditory nerves), the sound sidesteps the outer and middle ear.
Interpretation of Air Conduction and Bone Conduction Results
- If air conduction and bone conduction thresholds are within normal limits, then hearing is normal.
- If the air conduction thresholds indicate a loss and the bone conduction thresholds do not indicate a loss, then a conductive hearing loss is present. In other words a person does not hear normally when sound has to go through the outer, middle and inner ear, but if the sound bypasses the conductive mechanism (i.e. the outer and middle ear), and goes directly to the inner ear, then hearing is normal.
- If there is a loss by both air- and bone - conduction and the abnormal thresholds are essentially similar, then a sensorineural hearing loss exists. In other words, there is a hearing loss by air conduction, such as when the sound goes through the outer, middle and inner parts of the ear. There is the same amount of hearing loss when the sound bypasses the outer and middle ear and goes directly to the inner ear. If there is a loss by both air conduction and bone conduction, but the loss by air conduction is worse than the loss by bone conduction, a mixed hearing loss exists. Both conductive and sensorineural components are present.
This involves presenting the child with a series of simple recorded syllables, words and sentences spoken at various volumes into the headphones. The test is designed to assess speech threshold (i.e., when the child can first hear speech) and the child’s ability to understand speech (Scheetz, 2000). The test requires the child to repeat each word back to the audiologist as it is heard. This provides information on the volume (quantity) of the speech sound that the child can hear and also the quality of the sound (clear vs. distorted) the child hears. The level at which the child can repeat 50% of test materials correctly provides information about the type and degree of hearing impairment (Lysons, 1996). This is useful to determine the candidacy for hearing aid and reaffirm the findings of the pure-tone audiometry test.
Chapter 1: The Spirit of Inclusion
Chapter 3: Technological and Medical Interventions
Chapter 4: Teaching Strategies and Accommodations
Chapter 5: Activities
Chapter 6: Social Skills
Chapter 7: Counseling Students with Hearing Impairment
Chapter 8: Working with Families