Understanding Otoacoustic Emissions Testing
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As medical science continues to advance rapidly, the quest to understand and diagnose auditory pathologies has reached new heights. Otoacoustic Emission (OAE) testing stands at the forefront as a cornerstone of modern audiological evaluation.
Sound transmission through the inner ear
The human ear consists of three parts: the outer, middle, and inner ear. Tests are available to assess the function of each component, helping healthcare professionals diagnose and understand pathologies affecting the auditory pathway.
The inner ear consists of two primary structures: the cochlea, also known as the hearing organ, and the semicircular canals, which are responsible for balance regulation. Within the cochlea are microscopic hair cells that respond to sound vibrations. These hair cells include inner and outer hair cells, each specific to transmitting distinct sound frequencies. Signals produced by the movement of these hair cells are conveyed to the auditory nerve, which then transmits them to the auditory centers in the brain 1,2.
What are OAEs?
When you hear a sound, your cochlea reacts by making tiny hairs on its outer part vibrate. These vibrations create very quiet sounds called otoacoustic emissions (OAEs). OAEs are like echoes bouncing back into your ear. They travel in the opposite direction of incoming sound, going from the cochlea to the outer ear canal, where they can be measured objectively, without the need for the patient/client to respond. Checking for the presence of OAE responses is an easy way to see if your inner ear is healthy and if you might have trouble hearing1.
How does it work?
During OAE tests a specialized instrument called a probe, equipped with speakers and a microphone, is placed in the ear canal to measure otoacoustic emissions (OAEs). These emissions tell us if the tiny hairs in your cochlea are working well, which is important for your hearing health. OAEs are very helpful in checking babies' hearing when they're born, and also in diagnosing hearing problems in people of different ages2.
What does it mean?
When otoacoustic emissions (OAEs) are detected, it indicates that your cochlea is working well, your outer hair cells are healthy, and your hearing sensitivity is normal. This provides important information about your auditory system up to the level of the cochlea and shows whether:
- Your ear's conductive mechanism is functioning properly,
- There are no blockages in your ear canal,
- Your eardrum can move normally,
- Your impedance matching system is working.
Finding OAEs also suggests that your outer hair cells are doing their job2. OAEs are very good at catching even mild hearing problems, like damage from loud noises or certain medicines, before they show up on regular hearing tests. If OAEs aren't detected, it could mean there's a problem with your cochlea, but more tests might be required to establish if the problem is in the middle or inner part of your ear, and how much hearing loss you have.
Types of OAEs
There are two main types of otoacoustic emissions (OAEs): Distortion Product OAEs (DPOAEs) and Transient Evoked OAEs (TEOAEs). TEOAEs are low-level sounds emitted from the cochlear outer hair cells, subsequent to stimulation of the cochlea from click stimuli. hearOAE generates a series of clicks over a broad frequency range which is presented into the outer ear canal. The click stimuli alternate in level and polarity which gives rise to the non-linear response quantifying the OAE. Outer hair cell function is estimated across a limited range of frequencies, from 1kHz to 4kHz3. DPOAEs are low-level sounds emitted from cochlear hair cells in response to two closely presented stimulating tones at different frequencies (f1 and f2). The result is a distortion product tone at the specific test frequency (2f1-f2). hearOAE presents a sequence of tones directed into the outer ear canal and measures the DPOAE produced by the cochlear outer hair cells. Cochlear function is estimated across a larger range of frequencies, from 1kHz to 8kHz3
If you would like to find out more about otoacoustic emissions testing, its use cases and associated technological advancements, contact our helpful team of experts at: sales@hearxgroup.com
