Hearing Tests for Children
Behavioral hearing tests
The child (and typically the parent) is seated in a sound booth. Sounds of varying intensity are presented to the child via calibrated speakers or earphones. The sounds may consist of speech or music as well as specific frequencies that are critical to access (hear) the different sounds of speech. The audiologist looks for and records the child's responses to the softest sounds presented and plots them out on a graph called an audiogram. Behavioral hearing tests include the following methods for the following developmental ages:
- Behavioral Observation Audiometry (BOA) for developmental ages of 0 to 5 months: child's responses may consist of quieting, eye widening, startle, etc.
- Visual Reinforcement Audiometry (VRA) for developmental ages of 6 months to 2 years: child turns to the sound stimulus and a puppet lights-up to reward (reinforce) the child's listening behavior.
- Conditioned Orientation Reflex (COR) Audiometry: same as VRA, but more than one sound source and puppet reinforcer used. Many parents describe it as a "sound finding game."
- Conditioned Play Audiometry (CPA) begins to emerge around age 2 years and consistent between developmental ages of 2 to 3 years: a listening game that uses toys to maintain the child's attention and focus to the listening task. For example, the child holds a block, waits and listens for the sound. When the child hears the sound, they drop the block in a bucket. This is no different than raising one's hand in response to the sound, but the toys establish and maintains the child interested in the listening task for much longer than hand-raising alone. This "listening game" is demonstrated to the child by the audiologist, and once the child understands the game testing is underway.
- Conventional Audiometry consistently used in children ages 5 and older: child raises hand or provides verbal response (for example, "beep", "I hear it") in response to the sound stimulus.
Tests of auditory function
These are not direct measures of hearing, but rather measures of auditory function. However, some of these measures are correlated with difference degrees of hearing or hearing loss.
- Tympanometry (tympanogram): assesses health of the middle ear system and takes about 3 to 5 seconds. Small probe tip is placed in the ear canal. Sound is presented and recorded. A computer plots the movement of the eardrum by measuring the amount of sound reflected back. It is not painful, but does feel a little stuffy for a few seconds.
- Acoustic reflexes: assesses the integrity of a neural loop from the inner ear to the brainstem and back to the middle ear system. Same probe tip assembly used as in tympanometry.
- Otoacoustic emission (OAE) measures: provides indices of outer hair cell function in the inner ear (cochlea) and takes about 3 minutes per run. A probe tip is placed in the ear canal. Sounds are presented and an elicited response recorded. The response is very faint so the child must be extremely quiet during the test. Because the response is so faint, it may be obscured by the presence of ear wax, middle ear pathology (for example, fluid, pressure) or the presence of pressure equalization (PE) tubes.
- Auditory Brainstem Response (ABR) is an electrophysiological test. It is used in two ways: to assess auditory nerve function and to estimate hearing levels. Sounds are presented through an earphone while three small surface electrodes (one on or behind each ear and one usually placed on the forehead) pick-up the response to sound from the inner ear (cochlea) and auditory nerve. A computer averages the auditory responses and the audiologist interprets the results. Usually, the results are shared with the family immediately following the test. The test is not uncomfortable to the patient. When this test is used to estimate hearing levels for children 6 months and older, sedation is required for ABR recording. At our center, sedation is determined and monitored by the Children's Hospital at Dartmouth-Hitchcock (CHaD) Pain Free Clinic anesthesia team. On the day of the ABR test, the child is also seen by the otolaryngology (ear, nose, and throat) staff to determine if the ears are "clear" (for example, free of wax, middle ear fluid/infection) just prior to testing.
If you have questions regarding ABR testing at our center, please contact the audiology department. If your child is scheduled for a sedated ABR and you have questions regarding sedation, please contact the Pain Free anesthesia team at (603) 650-2908.