Transient Evoked Otoacoustic Emissions (TEOAE)

OAE Guides

What Are Transient Evoked Otoacoustic Emissions (TEOAEs)?

Transient Evoked Otoacoustic Emissions, or TEOAEs, are sounds generated by the cochlea in response to auditory stimulation. These emissions can be detected in the ear canal of individuals with normal outer hair cell function.

During this OAE test, the instrument delivers a sequence of clicks into the ear canal and records the returning acoustic signal. These clicks are typically presented at a stimulus level of approximately 84 dB peak equivalent sound pressure level, which is optimal for eliciting a measurable response from the outer hair cells without causing discomfort. The response is then averaged and analyzed. Averaging allows the system to separate the otoacoustic emission from background noise. In addition to averaging, the system uses band-pass filters to display frequency-specific OAE responses. Using these filters, the device estimates outer hair cell function across a broad frequency range, providing valuable insight into cochlear health.

 

 

Clinical Applications of TEOAE

TEOAE testing is employed to objectively assess the functional status of the outer hair cells within the cochlea. These cells are essential for cochlear amplification and contribute significantly to auditory sensitivity and frequency resolution. 

By presenting brief clicks, TEOAE testing elicits otoacoustic emissions that are measurable in the ear canal. These emissions indicate normal outer hair cell function, particularly in the frequency range that contains speech information. 

TEOAEs are typically absent when hearing thresholds exceed around 30 dB, making the test most effective for identifying mild to moderate cochlear dysfunction. 

This test is especially valuable in: 

  • Screening populations unable to provide reliable behavioral responses such as preschool and school screening
  • Newborn hearing screening 
  • Cross-validating behavioral audiometric findings, particularly when malingering hearing loss is suspected
  • Differentiating cochlear hearing loss from neural pathology 

 

 

TEOAE Device

Hardware

The hardware includes a probe system that houses a miniature loudspeaker to deliver transient (click) stimuli and a sensitive microphone to record the emissions generated by the cochlea. These probes are designed for both pediatric and adult patients and often feature automatic in-ear detection and fit verification to ensure optimal placement and reliable results. 

The device can range from compact handheld models, such as the GSI Novus™ and GSI Corti™, to PC-connected modules, such as the GSI Audera Pro™.  

Software

TEOAE systems offer control of the frequency bands and duration. Advanced response analysis tools provide real-time monitoring of acoustic and electrical signals, with adjustable filters and response windows to fine-tune data collection. 

Visualization options such as bar graph displays help interpret responses across frequency bands. Noise management is a key feature, with automated rejection algorithms and customizable thresholds to ensure clean data, even in noisy environments. Most systems include a pass or refer logic and rules that allow tests to conclude early once a pass has been confirmed. 

For data management, integration with platforms like OtoAccess®, Noah, GSI Suite, and GSI Data Manager enables seamless storage, retrieval, and comparison of patient results over time. Additionally, many devices support protocol flexibility, offering preset screening and diagnostic options as well as the ability to create and save custom protocols tailored to specific clinical needs. 

 

Preparing the Patient for TEOAE Testing

TEOAE testing can be conducted on individuals of all ages. The procedure typically begins with an otoscopic examination to ensure the ear canal is clear. If the patient has significant cerumen buildup, debris, or foreign objects, these must be removed prior to testing to avoid interference with probe placement and signal detection. 

Once the ear canal is clear, position the patient comfortably to allow unobstructed access to the ear. The probe tip should be inserted securely to create an acoustic seal. A poor seal can result in weak or absent emissions, so it's important to verify probe placement before starting the test. The patient should remain still throughout the procedure, as movement or vocalization can compromise the results. 

The test should be conducted in a quiet environment, minimizing background noise from sources such as HVAC systems, medical equipment, or hallway traffic. Even subtle environmental sounds can mask otoacoustic emissions, especially in the lower frequency range. 

 

Newborn Hearing Screening

Although this test can be performed on patients of all ages, TEOAE is often used in newborn hearing screening. For optimal results, perform the test while the infant is sleeping. Sucking, crying, or excessive movement can interfere with the probe stability and allow noise into the recording. In some cases, swaddling or feeding the infant beforehand can help facilitate a successful test. 

Test duration is typically brief, under two minutes per ear, but may vary depending on the equipment and the patient’s cooperation. If you're having a difficult time getting responses, consider rechecking probe placement, reducing ambient noise, or repeating the test after calming the infant. 

 

TEOAE Test Results

TEOAE test results are displayed in two different ways depending on the purpose of the test: screening or diagnostic. 

Screening TEOAE

Screening TEOAE test results are displayed as either Pass or Refer. It is important to note that a refer result does not confirm hearing loss, but it does indicate the need for further diagnostic testing, such as repeat OAE screening or follow-up ABR testing.

  • Pass: Indicates that otoacoustic emissions were detected, suggesting that the outer hair cells in the cochlea are functioning properly. This result implies a low likelihood of significant hearing loss. Typically, a response must be detected in at least 3 out of 4 frequency bands within the speech frequency range, usually 1,000 to 4,000 Hz. 
  • Refer: Indicates that OAEs were not detected, which could be due to the following: Excessive background noise during testing, middle ear issues such as fluid or a blockage, sensorineural hearing loss.

 

Diagnostic TEOAE

Diagnostic test results are displayed in real time, either using signal-to-noise ratio bars or a value graph. A higher signal-to-nose ratio indicates a stronger OAE response and a higher likelihood of normal hearing. Below are the interpretation guidelines for diagnostic TEOAE results: 

  • Emissions present across all frequency bands: This indicates that the outer hair cells are functioning normally, producing emissions consistent with healthy cochlear activity. 
  • Emissions absent in all bands: The lack of emissions suggests that the outer hair cells did not respond as expected, which may point to cochlear dysfunction or a middle ear issue. Further diagnostic testing is recommended to determine the underlying cause. 
  • Low SNR or inconsistent waveforms: These results may be due to poor probe placement, environmental noise, or ear pathology. To ensure accurate results, the patient should be re-prepped, the test environment controlled, and the test repeated. 

 

 

What are the differences between TEOAE and DPOAE?

TEOAEs measure a broad frequency spectrum all at once, making this test fast and efficient, especially in quiet environments. This makes them ideal for newborn hearing screenings and quick assessments of cochlear health. However, they are more sensitive to ambient noise, which can affect the accuracy of results in uncontrolled settings. 

Distortion Product Otoacoustic Emissions (DPOAEs) are produced when the ear is stimulated by two continuous pure tones. The cochlea responds by generating a third tone—a distortion product—that provides detailed information about specific frequency regions. DPOAEs cover extended high frequencies and are particularly useful for detecting high-frequency hearing loss. Though it’s traditionally slower to measure due to their frequency-by-frequency approach, modern equipment has significantly improved their speed. DPOAEs are also more robust in noisy environments, making them suitable for clinical diagnostics, ototoxicity monitoring, and research applications. 

In terms of underlying mechanisms, TEOAEs reflect linear reflection processes in the cochlea, while DPOAEs are the result of nonlinear distortion mechanisms. This distinction gives each method unique strengths in evaluating cochlear function. Clinicians often choose TEOAEs for quick screenings and DPOAEs for more detailed, frequency-specific diagnostics.