There are several methods of testing a child’s hearing. The method chosen depends in part on the child’s age, development, or health status.
Behavioural Tests: involve careful observation of a child’s behavioural response to sounds like calibrated speech and pure tones. Pure tones are the distinct pitches (frequencies) of sounds. Sometimes other calibrated signals are used to obtain frequency
Physiologic Tests: are not hearing tests but are measures that can partially estimate hearing function. They are used for children who cannot be tested behaviourally due to young age, developmental delay, or other medical conditions.
Auditory Brainstem Response (ABR) Test: an infant is sleeping or sedated for the ABR. Tiny earphones are placed in the baby’s ear canals. Usually, click-type sounds are introduced through the earphones, and electrodes measure the hearing nerve’s response to the sounds. A computer averages these responses and displays waveforms. Because there are characteristic waveforms for normal hearing in portions of the speech range, a normal ABR can predict fairly well that a baby’s hearing is normal in that part of the range. An abnormal ABR may be due to hearing loss, but it may also be due to some medical problems or measurement difficulties.
Auditory Steady State Response (ASSR) Test: an infant is typically sleeping or sedated for the ASSR. Sound is transmitted through the ear canals, and a computer picks up the brain waves in the hearing section of the brain and establishes what the hearing
capacity is. The ASSR is often done together with the ABR.
Otoacoustic Emissions (OAE) Test: this test is performed with a sleeping infant or an older child who may be able to sit quietly. In this brief test, a tiny probe is placed in the ear canal. Numerous pulse-type sounds are introduced, and an “echo” response from the inner ear is recorded. These recordings are averaged by a computer. Certain types of recordings are associated with normal inner-ear function.
Tympanometry: this is not a hearing test but a procedure that can show how well the eardrum moves when a soft sound and air pressure are introduced in the ear canal. It’s helpful in identifying middle ear problems, such as fluid collecting behind the eardrum. A tympanogram is a graphic representation of tympanometry. A “flat” line on a tympanogram may indicate that the eardrum is not mobile, while a “peaked” pattern often indicates normal function. An ear inspection should be performed with tympanometry.