One way of testing very young children is to use a special computer to measure the activity in the auditory areas of the baby's brain.   The Auditory Brainstem Response (ABR) is a tiny amount of brain activity that happens when a sound is heard.  The baby will be tested while they are asleep.   Sensors will be placed on the baby's forehead, temple and the back of the neck.   Then small earphones will are placed over the ears.  If the baby stays asleep and quiet, the ABR screening takes about 3 minutes per ear. If the baby passes the screening, no further action is needed.  If the baby doesn't pass in both ears, a second ABR will be done at the audiologists office. The threshold ABR defines the hearing loss using different types of sounds (clicks and tone bursts) as well as using both air and bone conduction.  

If your baby requires a threshold ABR, they will need to take a mild sedative, usually Chloral Hydrate so they stay asleep for the entire test.  The audiologist will provide you with more specific directions on how to prepare your baby so the test is accurate and is completed as quickly as possible.