Topic Card 1: Tests Used to Assess Hearing Loss

ID-10063603

Related Terms:

Audiologist; Audiogram; Auditory Brainstem Response Test (ABR); Auditory Steady State Response Test (ASSR); Behavioral Observation Audiometry/Visual Reinforcement Audiometry/Conditioned Play Audiometry; Otoacoustic Emissions (OAE); Tympanometry

Questions

What is an audiologist?

What do we need to know about a child’s hearing?

What is an audiogram?

How can an infant or a young child’s hearing be tested?

What other tests are performed as part of a hearing evaluation?

  • What is an audiologist?

An audiologist is a university trained, licensed professional specializing in testing hearing and management of hearing loss. The audiologist conducts tests to determine severity and type of hearing loss. If hearing loss is diagnosed, the audiologist will recommend further evaluation and suggest treatment options. Selecting an audiologist who has experience testing infants or young children is important.

  • What do we need to know about a child’s hearing?

When the hearing system works as it should, a person can hear very soft sounds that vary in frequency (pitch) from extremely low frequency to extremely high frequency. The ability to hear all these sounds at soft levels is important for children to learn language and to learn to speak. When the audiologist performs a hearing test, he/she wants to know the softest sound that the child can hear at each different pitch from low pitch to high pitch, and the softest speech sound the child can hear. By measuring these “thresholds” of hearing the audiologist is able to tell if the child has a hearing loss, how severe it is and what kind of treatment is needed to help the child to learn language and communication.

  • What is an audiogram?

An audiogram is a graph of the result of a hearing test. The softest tone heard (threshold) at each different frequency tested is plotted on the graph for the right and left ears. When children are tested through a loudspeaker (because they will not wear earphones), we cannot tell which of the two ears hears the sound.

  • How can an infant or young child’s hearing be tested?

Electrophysiological Tests – ABR and ASSR Children may be tested using the Auditory Brainstem Response Test (ABR). In this form of testing electrodes are placed on each ear and sound is sent into each ear separately. The electrodes measure the child’s “brain waves” and a computer selects the part that is related to hearing. The ABR test tells us if the sounds are moving through the brainstem toward the brain.The child must be very still and quiet during this test. Because young children often will not be still and quiet, they must sometimes be given a sedative to help them sleep during the test.The Auditory Steady State Response Test (ASSR) is a test similar to an ABR. The benefit of the ASSR is that the results may provide more accurate frequency information about a profound hearing loss at an earlier age than is possible with an ABR. Audiometry A hearing test given in a sound proof room, either with earphones or loudspeakers, requires that the child “tell us” if they can hear. This kind of test is called a “behavioral” test, because we must observe behavior to determine if the child hears. The kind of response we look for depends on the age of the child. Behavioral Observation Audiometry (BOA) Children less than 9 months of age may be testedin a sound proof room using an audiometer to produce sounds of different pitch and loudness. The audiologist knows if a child hears a sound by watching the child’s behavior (changes in the child’s facial expression including eye-widening or eye-blinking, increased tension or changes in sucking behavior). Because children at this age respond inconsistently, this kind of testing is not reliable. All children of this age should have an ABR in addition to a behavioral test. Visual Reinforcement Audiometry (VRA) Between about 9 months of age and about threeyears of age, the child is taught to look at a toy that is lighted and moves when a sound is heard. The child’s head turn is a reliable way to measure hearing thresholds. However, some children are not very interested in the lighted toys, or are not ready to perform this response. When the results of this testing is not considered accurate the child should also be tested using an ABR. Conditioned Play Audiometry (CPA) Children older than about three years of age are taught a“play” response (like putting a peg in a pegboard) when they hear sounds. Children who understand this game can be tested very reliably using Play Audiometry. If the audiologist doubts the test accuracy, an ABR should be recommended. When children are about 5 years of age, they can be taught to raise a hand or push a button when they hear a very soft sound.

  • What other tests are performed as part of a hearing evaluation?

Otoacoustic Emissions (OAE) An otoacoustic emissions test gathers basic information about the function of the inner ear. A small probe is placed into each ear separately and soft sounds of different pitch are sent into the ear. The probe measures “echoes” in the ear canal that occur when a child has normal or near-normal hearing. A hearing loss is suspected if no “echoes” are recorded. This test will not tell us the severity of a hearing loss. Tympanometry Tympanometry is a test that measures the movement of the eardrum (tympanic membrane), and the ability of the ear to send sound to the inner ear. During this test a small probe is placed into each ear separately, and the pressure in the ear canal is changed. A graph is drawn which shows the condition and health of the middle ear. This test is important because temporary conditions of the middle ear may affect our interpretation of other hearing tests.