Hearing tests for young children
The tests selected to assess hearing in infants and young children depend on the:
- child's age and ability to undertake the test
- information that is needed about the child's hearing.
Most children will be assessed using a combination of behavioral and physiological tests.
Behavioral tests
Behavioural tests are based on eliciting or observing a change in behaviour in response to sound.
- Behavioral observation audiometry (BOA) noisemaker testing is carried out with infants younger than seven months of age and with older children who cannot respond when they hear a sound. Behavioural responses include startling to loud noises and stirring from sleep in response to a sound. An assortment of noisemakers, such as crunching cellophane, tiny bells and chimes, are used and most can be classified as low, mid or high frequency sounds.
- Visual reinforcement orientation audiometry (VROA) is used to test the hearing of children between seven months and three years of age. VROA involves the child turning towards the loudspeaker when a sound is presented. By altering the frequency and intensity of the sounds, it is possible to find out about the child's ability to hear sounds across a range of frequencies.
- Play audiometry is used to test the hearing of children from three years of age. This is also used to test the child's hearing when hearing devices are worn. Play audiometry works the same way as pure tone audiometry (person indicates when they can hear a tone), except when the child hears a tone, they put a marble in a marble race, press a computer key or put a piece in a puzzle.
Electro-physiological tests
Physiological tests help determine which part of the auditory system is involved in the child's hearing loss. Physiological tests measure a physical response of a specific part of the auditory system and require little or no co-operation from the child.
- Oto-acoustic emission testing (OAE) gives an idea about how hair cells in the cochlea are working. They respond to sound by producing a very soft sound of their own called an oto-acoustic emission.
- Brainstem evoked response audiometry (BERA) provides information on electrical activity generated in response to sound along the nerve pathway, also called the brainstem, to the brain. It may be carried out while a baby is in natural sleep. If this is not possible, testing must be carried out in hospital.
- Electro-cochleography (ECochG or EcoG) is performed in hospital, under anesthetic. It picks up the tiny electrical signals generated in the cochlea in response to sound. It provides information about the functioning of the cochlea and the start of the nerve pathway to the brain.
- Tympanometry and acoustic reflex give information about the middle ear which is just behind the eardrum. A tympanogram, which shows if the eardrum is moving normally, may indicate a problem in the middle ear that can cause a conductive hearing loss. When a child has a normal tympanogram, it may be possible to test for the presence of a muscle reflex - acoustic reflex - in the middle ear. The absence of this reflex to different sounds gives information about the auditory system.
