Hearing tests

The testing of a person's ability to hear various sound frequencies is knownas audiometry. The test is performed using electronic equipment called an audiometer and is usually administered by an audiologist, a trained technician.

Audiometry is used to identify and diagnose hearing loss. The equipment is used in health screening programs, for example in grade schools, to detect hearing problems in children. It is also used in the doctor's office or hospitalaudiology department to diagnose hearing problems in children, adults, and the elderly. With correct diagnosis of a person's specific pattern of hearing impairment, the right type of therapy can be prescribed. It might include hearing aids, corrective surgery, or speech therapy.

Testing with audiometry equipment is simple and painless. The equipment emitssounds or tones, like musical notes, at various frequencies, or pitches, andat differing volumes or levels of loudness. Testing is usually done in a soundproof testing room.

The person being tested wears a set of headphones that blocks out other distracting sounds and delivers a test tone to one ear at a time. At the sound ofa tone, the patient holds up a hand or finger to indicate that the sound is detected. The audiologist lowers the volume and repeats the sound until the patient can no longer detect it. This process is repeated over a wide range oftones or frequencies from very deep, low sounds, like the lowest note playedon a tuba, to very high sounds, like the pinging of a triangle. Each ear is tested separately. It is not unusual for levels of sound sensitivity to differfrom one ear to the other.

A second type of audiometry testing uses a headband rather than headphones. The headband is worn with small plastic rectangles that fit behind the ears toconduct sound through the bones of the skull. The patient being tested senses the tones that are transmitted as vibrations through the bones to the innerear. As with the headphones, the tones are repeated at various frequencies and volumes.

The results of the audiometry test may be recorded on a grid or graph calledan audiogram. This graph is generally set up with low frequencies or tones atone end and high ones at the other end, much like a piano keyboard. Low notes are graphed on the left and high notes on the right. The graph also chartsthe volume of the tones used; from soft, quiet sounds at the top of the chartto loud sounds at the bottom. Hearing is measured in units called decibels.Most of the sounds associated with normal speech patterns are in the range of20-50 decibels. An adult with normal hearing can detect tones between 0-20 decibels.

Speech audiometry is another type of testing that uses a series of simple recorded words spoken at various volumes into headphones worn by the patient. The patient repeats each word back to the audiologist as it is heard. An adultwith normal hearing will be able to recognize and repeat 90-100% of the words.

The ears may be examined with an otoscope prior to audiometry testing to determine if there are any blockages in the ear canal due to ear wax or other material.

Audiometry test results are considered abnormal if there is a significant orunexplained difference between the levels of sound heard between the two ears, or if the person being tested is unable to hear in the normal range of frequencies and volume. The pattern of responses displayed on the audiogram can be used by the audiologist to identify if a significant hearing loss is present and if the patient might benefit from hearing aids or corrective surgery.

A vibrating tuning fork held next to the ear or placed against the skull willstimulate the inner ear to vibrate, and can help determine if there is hearing loss.

Two types of tests with tuning forks are typically conducted. In the Rinne test, the vibrating tuning fork is held against the skull, usually on the bonebehind the ear (mastoid process) to cause vibrations through the bones of theskull and inner ear. It is also held next to, but not touching, the ear, tocause vibrations in the air next to the ear. The patient is asked to determine which sound is louder, the sound heard through the bone or through the air.A second tuning-fork test is the Weber test, which places the stem or handleof the vibrating tuning fork at various points along the midline of the skull and face. The patient is then asked to identify which ear hears the sound created by the vibrations. Tuning forks of different sizes produce different frequencies of vibrations and can be used to establish the range of hearing.

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