Audiometry (Hearing Evaluation Test)

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An audiometry evaluation is a painless, noninvasive hearing test that measures a person’s ability to hear different sounds, pitches, or frequencies.Patients who have a tumor in or around the ear may undergo audiometry testing to determine whether hearing loss has occurred or to monitor their hearing before and after surgery. It is also used to evaluate whether hearing aids or surgery may improve one’s hearing.

An audiometry exam tests your ability to hear sounds. Sounds vary, based on their loudness (intensity) and the speed of sound wave vibrations (tone).

Hearing occurs when sound waves stimulate the nerves of the inner ear. The sound then travels along nerve pathways to the brain.

Sound waves can travel to the inner ear through the ear canal, eardrum, and bones of the middle ear (air conduction). They can also pass through the bones around and behind the ear (bone conduction).

The INTENSITY of sound is measured in decibels (dB):

  • A whisper is about 20 dB.
  • Loud music (some concerts) is around 80 to 120 dB.
  • A jet engine is about 140 to 180 dB.

Sounds greater than 85 dB can cause hearing loss after a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time.

The TONE of sound is measured in cycles per second (cps) or Hertz:

  • Low bass tones range around 50 to 60 Hz.
  • Shrill, high-pitched tones range around 10,000 Hz or higher.

The normal range of human hearing is about 20 to 20,000 Hz. Some animals can hear up to 50,000 Hz. Human speech is usually 500 to 3,000 Hz.

OAE Hearing Evaluation

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What is an OAE (Otoacoustic Emissions) Hearing Test?

OAE or otoacoustic emission testing is the recording of sounds that the ear produces itself. Clicks or tones are played through soft earphones into the baby’s ears. Three electrodes placed on the baby’s head measure the hearing nerve’s response. Otoacoustic Emissions (OAE)—This test measures sound waves produced in the inner ear. A tiny probe is placed just inside the baby’s ear canal.

Why is OAE Used?

Otoacoustic Emissions Hearing tests are usually performed on newborn babies to detect deafness. The test can also partially estimate hearing sensitivity and test for functional hearing loss. Functional hearing loss is also sometimes referred to as non organic hearing loss and is a condition where you have symptoms or behaviors of hearing loss but there is nothing actually wrong with your hearing. Some sources might refer to this as feigned hearing loss but that’s probably not completely accurate as this implies that someone is “faking it” and this type of hearing loss has multiple origins that are not always within an individuals control.Otoacoustic Emissions Hearing tests are commonly used in conjunction with the ABR (Auditory Brainstem Response) hearing test or other hearing tests.

How is OAE Performed?

Otoacoustic Emissions Hearing testing is not painful and many babies sleep right through it. Small probes are placed in the ear. One delivers sound and the other is a microphone. If the cochlea is functioning properly it should echo in response to the sound.

 

There are four types of sounds that the cochlea produces:

  1. Spontaneous acoustic emissions – the cochlea produces these sounds spontaneously (not in response to another sound). These only occur in approximately 40-50 percent of people with normal hearing.
  2. Transient otoacoustic emissions – produced in response to another sound of short duration (transient). Usually clicks or tone-bursts. These are commonly used to evaluate hearing in infants.
  3. Distortion product otoacoustic emissions – produced in response to two simultaneous tones of different frequencies. These are particularly useful in detecting damage to the cochlea early on (for example damage to the cochlea from ototoxicity or noise induced damage).
  4. Sustained – frequency otoacoustic emissions – produced in response to a continuous tone. These are not typically used in the clinical setting.
  5.  

    Some conditions can cause the absence of OAE’s. These include: cysts, external otitis (swimmer’s ear for example), stenosis, or abnormal middle ear pressure, a perforated ear drum, otosclerosis, cholesteatoma.

    OAE testing cannot definitively diagnose hearing loss or deafness. If you fail OAE testing you will need further hearing tests to determine if there is hearing loss or not.

    Sometimes OAE testing is inaccurate because an infant is fussy during the test and sometimes babies have fluid in their ears or other conditions that can cause them to fail the test even though they do not have any permanent hearing loss.

     

    Other factors that can cause OAE testing to fail or be inaccurate include:

    • Poor seal around the ear probes.
    • Ear wax blockage, especially if it prevents getting a good seal around the ear probe.
    • Debris or foreign objects in the ear canal.
    • An uncooperative patient.

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Dr. Priyata Singla

Dr. Jatinder Singla