An OAE, or otoacoustic emission, is a faint sound produced by healthy inner ear cells. Clinicians measure these sounds with a small ear probe to check whether the inner ear is working properly. OAE testing is one of the most common hearing screenings in the world, used routinely on newborns within the first few days of life and on adults being monitored for hearing damage.
How the Inner Ear Produces Sound
Your inner ear doesn’t just receive sound. It also generates it. Deep inside the snail-shaped cochlea, specialized cells called outer hair cells physically change shape in response to incoming sound vibrations. These cells contain a protein that contracts and expands with each vibration, amplifying the signal and sharpening the ear’s ability to distinguish different pitches. This amplification process is what gives healthy hearing its sensitivity and precision.
As a byproduct of that process, the outer hair cells vibrate the surrounding fluid and structures, sending tiny sound waves back out through the middle ear and into the ear canal. These outgoing sounds are otoacoustic emissions. They’re extremely quiet, far too soft to hear with the naked ear, but a sensitive microphone can pick them up. If the outer hair cells are damaged or missing, the emissions weaken or disappear entirely, which is what makes OAE testing so useful as a quick check of inner ear health.
What Happens During the Test
An OAE test is painless and fast. An audiologist or screener places a small probe into the outer ear canal. The probe contains tiny speakers that play brief sounds and a microphone that listens for the emissions coming back from the cochlea. The entire measurement takes roughly 10 to 30 seconds per ear, and the full appointment usually wraps up in a few minutes.
No response from the patient is needed, which is why OAE testing works so well for newborns, infants, and people who can’t communicate reliably. The person being tested simply needs to sit or lie still. For babies, the test is often done while they’re sleeping.
Types of OAE Tests
There are three main types of otoacoustic emissions, and each one tells clinicians something slightly different.
- Spontaneous OAEs (SOAEs) occur without any sound stimulus at all. About 83% of women and 62% of men with normal hearing produce detectable spontaneous emissions, and they’re more common in the right ear than the left. These aren’t typically used for clinical screening but confirm that the outer hair cells are active.
- Transient-evoked OAEs (TEOAEs) are triggered by short clicks played into the ear. They capture a wide range of frequencies at once, making them fast in quiet environments. TEOAEs perform especially well in the lower-mid frequency range, roughly 500 to 1,500 Hz.
- Distortion-product OAEs (DPOAEs) are generated when two tones at slightly different pitches are played simultaneously. The outer hair cells produce a third tone, a distortion product, that the microphone picks up. DPOAEs test frequencies one at a time but are stronger at higher pitches above 4,000 Hz, making them better for detecting damage in the range where noise exposure and medication side effects tend to hit first.
Both TEOAEs and DPOAEs perform well between 1,500 and 4,000 Hz, and neither is reliable below 500 Hz. Which type a clinic uses often depends on the specific clinical question and the age of the patient.
OAE Screening in Newborns
Most hospitals screen every baby’s hearing within the first one to three days of life, and OAE testing is a primary tool for that screening. A pass result means the cochlea produced measurable emissions, indicating the outer hair cells are functioning. A “refer” result means emissions weren’t detected and the baby needs further evaluation.
A refer result doesn’t always mean hearing loss. In the first 24 hours after birth, residual birth material in the ear canal can block the signal and cause a false refer. Fluid in the middle ear has the same effect. For this reason, many hospitals use a two-step approach: if a baby gets a refer on the initial OAE, an automated auditory brainstem response (ABR) test is performed right away to get a second data point. This two-step protocol reaches about 92% sensitivity for detecting true hearing problems.
What “Pass” and “Refer” Actually Mean
The screening device compares the strength of the emission signal to the background noise in the ear canal. A pass generally requires the emission to be at least 6 decibels louder than the noise floor. If the signal clears that threshold, it’s strong evidence that the outer hair cells at that frequency are healthy.
Overall, OAE testing has 80 to 90% sensitivity and about 90% specificity. That means it catches the large majority of ears with outer hair cell problems while correctly passing most healthy ears. It’s a reliable frontline screening tool, but it’s a screening, not a full diagnostic. A refer result triggers more detailed testing rather than an immediate diagnosis.
What OAE Testing Cannot Detect
OAE tests have two significant blind spots worth understanding.
The first is middle ear problems. Because emissions travel from the cochlea through the middle ear to reach the microphone, any fluid or congestion in the middle ear space dampens or eliminates the signal. In children with middle ear infections and fluid buildup, emissions are absent in roughly two-thirds of affected ears. The cochlea may be perfectly healthy, but the test can’t see past the middle ear obstruction. This is why an abnormal OAE result in a child with a known ear infection is interpreted differently than the same result in a child with clear ears.
The second blind spot is a condition called auditory neuropathy spectrum disorder (ANSD). In ANSD, the outer hair cells work fine, so OAE results come back normal. But the auditory nerve that carries signals from the cochlea to the brain is damaged or dysfunctional. A person with ANSD can pass an OAE screening and still have significant hearing difficulties. Diagnosing ANSD requires an ABR test, which measures nerve activity directly. This is one reason high-risk newborns receive both OAE and ABR testing rather than OAE alone.
OAE Testing in Adults
OAE screening isn’t just for babies. In adults, one of its most valuable uses is monitoring for early hearing damage caused by certain medications, particularly some chemotherapy drugs and high-dose antibiotics that are known to harm outer hair cells. OAE testing can detect changes in hair cell function before the damage shows up on a standard hearing test, giving doctors a chance to adjust treatment before permanent loss sets in.
This early-detection advantage makes OAEs especially useful for patients who can’t participate in traditional hearing tests, such as young children with short attention spans or hospitalized adults who are sedated or unresponsive. Because the test requires no behavioral response, it provides objective data regardless of the patient’s ability to cooperate.
There are limits to OAE monitoring in adults. If someone already has hearing loss greater than about 40 decibels or has abnormal middle ear function, OAE testing becomes unreliable. In those cases, other tools like ABR are more appropriate for tracking changes over time.