Did you know that hearing can be tested shortly after birth? There are two ways to test a newborn’s hearing: otoacoustic emissions (OAEs) and the auditory brainstem response (ABR).
Otoacoustic emissions (OAEs) are clinically important because they are the basis of a simple, non-invasive, test for hearing defects in newborn babies and in children who are too young to cooperate in conventional hearing tests. An otoacoustic emission test measures an acoustic response that is produced by the inner ear (cochlea), which in essence bounces back out of the ear in response to a sound stimulus. The test is performed by placing a small probe that contains a microphone and speaker into the ear. As the patient rests quietly, sounds are generated in the probe and responses that come back from the cochlea are recorded. Once the cochlea processes the sound, an electrical stimulus is sent to the brainstem. In addition, there is a second and separate sound that does not travel up the nerve, but comes back out into the ear canal. This “byproduct” is the otoacoustic emission. The emission is then recorded with the microphone probe and represented pictorially on a computer screen. The audiologist can determine which sounds yielded a response/emission and the strength of those responses. Research has shown that babies with normal hearing have measurable OAEs as soon as six hours after birth.
The auditory brainstem response (ABR) can be used to estimate the sensitivity of the ear to sounds, in addition to assessing the integrity of the auditory nervous system. The lowest level required for various types of sounds to cause a nerve response can be measured, which can then be used to estimate hearing ability. Tiny electrodes are pasted and taped to the baby’s scalp and soft foam or rubber eartips are inserted into the baby’s ear canals. Varying levels of different types of sounds are presented and nerve responses are obtained and measured. Screening ABR testing has become so advanced that testing can often be completed in less than 30 minutes per ear while the infant is asleep.
Universal newborn hearing screening is recommended or mandated in most states across the country. About 6 out of every 1000 babies are born with a hearing loss; others may develop hearing loss after birth.
Babies learn to talk and understand language through their sense of hearing from the very moment they are born. Identifying and treating hearing loss before the age of six months is the best way to assure normal speech and language development. If you are concerned that your child may have a hearing loss, consult an audiologist immediately.
Use our handy Hearing Development Chart to check your baby’s hearing development!