Evaluation of Hearing (Audiology)

Evaluation of Hearing (Audiology), classification and amplification

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Evaluation of Hearing (Audiology)

Audiology evaluations consist of a series of tests used to determine whether a hearing loss exists and, if so, measure its type, degree and configuration. An audiologist will assess the results of each individual test in order to develop a treatment plan geared toward your unique hearing loss.

Hearing loss is a progressive condition that often develops slowly. Many people are not aware of a change in their hearing because they gradually adapt to the subtle changes in their hearing ability over time. Studies indicate that it takes seven years, on average, for a hearing impaired individual to seek treatment.

An audiology evaluation should be the first course of action for anybody who even suspects a hearing loss. The sooner a diagnosis of hearing loss is made, the more successful treatment will be. Early detection means more options for the patient.

Types of Tests Used to Evaluate Hearing in Children and Adults

Otoscopy: An otoscopy is an examination of the ear using an instrument called an otoscope, which consists of a handle, a light source, a magnifying lens and a cone that is inserted into the ear canal. It is performed by gently pulling the outer ear upward and backward, straightening the external canal and inserting the device. Sometimes air is puffed into the canal so the physician can see how the eardrum responds to pressure. Abnormal findings include perforation of the eardrum, blockage of the ear canal (sometimes causes by excess wax) and irritation/infection.

Bone Conduction Testing: Bone conduction testing is another type of pure-tone test that measures the inner ear’s response to sound. If there is damage or a blockage in the outer or middle ear, bone conduction audiometry testing may be used.

Instead of sending the tones through the ear, this type of testing is able to bypass the outer and middle ear and send the tone directly to the inner ear. A small vibrator is placed behind the ear. The device sends out a vibration that passes through the skull bone to reach the inner ear.

If the results of this test are different than the air conduction test, your audiologist can use this information to determine whether you have a conductive or sensorineural hearing loss.

Alternatively, a two-pronged metal tuning fork may be placed behind the ear or on the forehead. When vibrated, it produces a tone that travels to the cochlea via the skull. Your response determines how well sound travels through different parts of your ear, helping the audiologist diagnose your type of hearing loss.

Speech Testing: Speech (or word recognition) testing is used to measure your speech reception threshold (SRT), or the faintest speech you can understand 50 percent of the time. This is compared with your pure-tone test results to confirm the diagnosis. In addition, your ability to separate speech for background noise may be recorded.

Speech testing may be administered in either a quiet or noisy environment; results are recorded along with the audiogram for easy visual reference.

Tympanometry: Tympanometry is a test of the middle ear used to detect fluid, wax buildup, eardrum perforations and tumors. It measures movement of the eardrum in response to air pressure; the results are recorded on a chart called a tympanogram.

Acoustic Reflex Testing: The acoustic reflex test measures involuntary muscle contractions of the middle ear, and is used to determine the location of your hearing problem (the ossicles, cochlea, auditory nerve, etc.) as well as the type of hearing loss.

Auditory Brainstem Response (ABR): Auditory Brainstem Response Testing tells us how the inner ear (cochlea) to the brain pathways for hearing are working. This test is used with children and patients who cannot complete behavioral hearing testing. It is also used if symptoms may be due to hearing loss in the brain or in the auditory pathway.

The ABR test is often called “Auditory Evoked Potential Testing.”

Otoacoustic Emissions (OAEs): Otoacoustic emissions (OAEs) are sounds generated by vibrations of the hair cells in the cochlea of the inner ear. OAE testing utilizes a tiny probe fitted with a microphone and speaker that is used to stimulate the cochlea and measure its response. Individuals with normal hearing will produce emissions; when a hearing loss exceeds 25-30 decibels, no sound will be produced.

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OAE testing is often included in newborn hearing screening programs.

Threshold equalizing noise (TEN) test: This test determines if you have any pitch regions in the inner ear that no longer respond to sound stimulation, thus creating “dead zones.” Your audiologist may use information about any nonfunctional regions of the inner ear in determining how to adjust hearing aids and how much help the hearing aids can provide.

Sentence-in-noise (SIN) test: This test evaluates your ability to understand conversational speech in noisy environments and compares your performance to that of listeners without difficulty hearing speech in noise. Your audiologist uses these test results to determine whether you might benefit from hearing aids in noisy situations and what type of hearing aid circuitry might be needed.

Pure Tone Testing: Pure-tone testing (also known as pure tone audiometry) uses air conduction to measure your ability to hear sounds of various pitches and volumes. Wearing headphones, you will be asked to identify a series of tones by raising a hand, pressing a button, or responding verbally.

The results are charted on an audiogram, a graph that shows the type, degree and configuration of your hearing loss by comparing pitch (frequency) with loudness (intensity). The pattern recorded will help your audiologist determine your hearing threshold.

Tuning Fork Tests (Rinne’s and Weber’s tests)

How to do Weber’s Test

  • To perform Weber’s test strike the fork against your knee or elbow, then place the base of the fork in the midline, high on the patient’s forehead
  • It is important to steady the patient’s head with your other hand so that reasonably firm pressure can be applied
  • Then ask the patient: Do you hear the sound louder in one ear than the other?”
  • If so, in which ear is it louder?
  • If the patient is unclear, you may ask if they hear it “everywhere.” Be careful not to ask the question in a leading manner

How to do Rinne’s Test

  • This test aims compare air conduction with bone conduction
  • Rinne’s test has a high sensitivity (0.84) though this varies with the skill of the examiner. Rinne’s test can only detect a conductive hearing loss of at least 30dB

Explain the test first:

“I’m going to put this vibrating tuning fork in two positions, one touching the bone near you ear, one a short distance from the ear. I want you to tell me which position you hear the tuning fork loudest in”

  • Begin by striking the tuning fork against your knee or elbow
  • Hold the tuning fork in one hand and place the base against the patient’s mastoid process
  • Allow it to stay there for 2-3 seconds to allow them to appreciate the intensity of the sound
  • Then promptly lift the fork off the mastoid process and place the vibrating tips about 1cm from their external auditory meatus
  • Leave it there again for a few seconds before taking the tuning fork away from their ear
  • Ask the patient in which of the positions they were able to hear the note the loudest in

Hearing loss classification.

ClassificationVocal EquivalentDecibel (dB) Range
NormalSoft whisper0–20 dB
MildSoft spoken voice20–40 dB
ModerateNormal spoken voice40–60 dB
SevereLoud spoken voice60–80 dB
ProfoundShout> 80 dB

Hearing Amplification

Patients with hearing loss not correctable by medical therapy may benefit from hearing amplification. Contemporary hearing aids are comparatively free of distortion and have been miniaturized to the point where they often may be contained entirely within the ear canal or lie inconspicuously behind the ear.

For patients with conductive loss or unilateral profound sensorineural loss, bone-conducting hearing aids directly stimulate the ipsilateral cochlea (for conductive losses) or contralateral ear (profound unilateral sensorineural loss).

In most adults with severe to profound sensory hearing loss, the cochlear implant—an electronic device that is surgically implanted into the cochlea to stimulate the auditory nerve—offers socially beneficial auditory rehabilitation.

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