Audiometry

enUK

Audiometry

The quantitative assessment of individual hearing, either normal or defective. Three types of audiometric tests are used: pure tone, speech, and bone conduction tests. Such tests may serve various purposes, such as investigation of auditory fatigue under noise conditions, human engineering study of hearing aids and communication devices, screening of individuals with defective hearing, and diagnosis and treatment of defective hearing. In all of these situations, individual hearing is measured relative to defined standards of normal hearing.

The pure-tone audiometer is the instrument used most widely in individual hearing measurement. It is composed of an oscillator, an amplifier, and an attenuator to control sound intensity. For speech tests of hearing, word lists called articulation tests are reproduced on records or tape recorders. Measurements of detectability or intelligibility can be made by adjusting the intensity of the test words. To make bone conduction tests, sound vibrations from the audiometer activate a vibrator located on the forehead or mastoid bone.

Scientific advance in audiometry demands careful control of all environmental sound. Two types of rooms especially constructed for research and measurement of hearing are the random diffusion, or reverberation, chamber and the anechoic room. In the reverberation chamber, sounds are randomly reflected from heavy nonparallel walls, floor, and ceiling surfaces. In the anechoic room, the fiber glass wedges absorb all but a small percent of the sound.

The measurement of hearing loss for pure tones in defective hearing is represented by the audiogram (see illustration). Sounds of different frequencies are presented separately to each ear of the individual, and the intensity levels of the absolute thresholds for each frequency are determined. The absolute threshold is the lowest intensity which can be detected by the individual who is being tested.

Audiogram for determining the audibility curve for pure-tone hearing loss at various frequency levels

In clinical audiometry the status of hearing is expressed in terms of hearing loss at each of the different frequency levels. In the audiogram the normal audibility curve, representing absolute thresholds at all frequencies for the normal ear, is represented as a straight line of zero decibels. Amount of hearing loss is then designated as a decibel value below normal audibility. The audiogram in the illustration reveals a hearing loss for tones above 500 Hz. Automatic audiometers are now in use which enable individuals to plot an audiogram for themselves.

Articulation tests are speech perception or speech hearing tests used to assess hearing and loss of hearing for speech. The threshold of intelligibility for speech is defined as the intensity level at which 50% of the words, nonsense syllables, or sentences used in the articulation test are correctly identified. The hearing loss for speech is determined by computing the difference in decibels between the individual intelligibility threshold and the normal threshold for that particular speech test. Discrimination loss for speech represents the difference between the maximum articulation score at a high intensity level (100 dB), expressed in percent of units identified, and a score of 100%. The measure of discrimination loss is important in distinguishing between conduction loss and nerve deafness.

Bone conduction audiograms are compared with air conduction audiograms in order to analyze the nature of deafness. Losses in bone conduction hearing generally give evidence of nerve deafness, as contrasted to middle-ear or conduction deafness. See Ear (vertebrate), Hearing impairment

Audiometry

acoumetry, measurement of the acuteness of hearing. Since acuteness of hearing is defined generally by the threshold of perception of a sound, audiology consists in the determination of the weakest sound perceived by man. The simplest audiometric methods are the detection of the perception of sounds of various volumes produced by human speech and by tuning forks of varying lengths. In general, audiometry is performed by special electrical acoustic devices—audiometers. For a change in pitch (from 100 to 8,000 cycles per second) and volume of sound (from 0 to 125 decibels) on the audiometer, the minimum intensity for which the sound is still barely audible (threshold of perception) is ascertained. The results of audiometry are recorded in the form of an audiogram—a curve drawn on a special audiometric grid. By determining the patient’s threshold intensity of sound on a scale, the degree of hearing loss is determined. Audiometers are also used in other, more complicated tests.

L. V. NEIMAN

audiometry

[‚ȯd·ē′äm·ə·trē] (acoustics) The study of hearing ability by means of audiometers.

audiometry

enUK

Audiometry

Definition

Audiometry is the testing of a person's ability to hear various sound frequencies. The test is performed with the use of electronic equipment called an audiometer. This testing is usually administered by a trained technician called an audiologist.

Purpose

Audiometry testing 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 hospital audiology 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, which might include hearing aids, corrective surgery, or speech therapy, can be prescribed.

Precautions

Testing with audiometry equipment is simple and painless. No special precautions are required.

Description

A trained audiologist (a specialist in detecting hearing loss) uses an audiometer to conduct audiometry testing. This equipment emits sounds or tones, like musical notes, at various frequencies, or pitches, and at 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 of a 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 of tones or frequencies from very deep, low sounds, like the lowest note played on a tuba, to very high sounds, like the pinging of a triangle. Each ear is tested separately. It is not unusual for levels of sensitivity to sound to differ from 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 to conduct sound through the bones of the skull. The patient being tested senses the tones that are transmitted as vibrations through the bones to the inner ear. 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 called an audiogram. This graph is generally set up with low frequencies or tones at one 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 charts the volume of the tones used; from soft, quiet sounds at the top of the chart to loud sounds at the bottom. Hearing is measured in units called decibels. Most of the sounds associated with normal speech patterns are generally spoken in the range of 20-50 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 being tested. The patient repeats each word back to the audiologist as it is heard. An adult with normal hearing will be able to recognize and repeat 90-100% of the words.

Preparation

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.

Normal results

A person with normal hearing will be able to recognize and respond to all of the tone frequencies administered at various volumes in both ears by the audiometry test. An adult with normal hearing can detect a range of low and high pitched sounds that are played as softly as between nearly 0-20 decibels. Normal speech is generally spoken in the range of 20-50 decibels.

Abnormal results

Audiometry test results are considered abnormal if there is a significant or unexplained 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.

Resources

Organizations

American Academy of Audiology. 8201 Greensboro Drive, Suite 300, McLean, VA 22102. (703) 610-9022. http://audiology.org.Audiology Awareness Campaign. 3008 Millwood Ave., Columbia, SC 29205. (800) 445-8629.

Other

"How to Read Your Hearing Test." Hearing Alliance of America. http://www.earinfo.com."Understanding Your Audiogram." The League for the Hard of Hearing. http://www.lhh.org.

Key terms

Audiogram — A chart or graph of the results of a hearing test conducted with audiographic equipment. The chart reflects the softest (lowest volume) sounds that can be heard at various frequencies or pitches.Decibel — A unit of measure for expressing the loudness of a sound. Normal speech is typically spoken in the range of about 20-50 decibels.Otoscope — A hand-held instrument with a tiny light and a funnel-shaped attachment called an ear speculum, which is used to examine the ear canal and eardrum.

audiometry

[aw″de-om´ĕ-tre] measurement of the acuity of hearing through generation of tones of known frequencies and amplitudes. See also audiogram (def. 2). adj., adj audiomet´ric.electrocochleographic audiometry measurement of electrical potentials from the middle ear or external auditory canal (microphonics" >cochlear microphonics and eighth nerve action potentials) in response to acoustic stimuli.pure tone audiometry audiometry utilizing pure tones that are relatively free of noise and overtones.speech audiometry that in which the speech reception threshold in decibels and the ability to understand speech (speech discrimination) are measured.

au·di·om·e·try

(aw'dē-om'ĕ-trē), 1. The measurement of hearing. 2. The use of an audiometer. 3. Rapid measurement of the hearing of one person or a group against a predetermined limit of normality; auditory responses to different frequencies presented at a constant intensity level are tested.

audiometry

The testing a person’s hearing at different thresholds and frequencies.

audiometry

The measurement of hearing. See Play audiometry, Pure tone audiometry, Speech threshold audiometry.

au·di·om·e·try

(aw'dē-om'ĕ-trē) 1. The measurement of hearing. 2. The use of an audiometer. 3. Rapid measurement of the hearing of an individual or a group against a predetermined limit of normality; auditory responses to different frequencies presented at a constant intensity level are tested.

audiometry

Measurement of the sensitivity, or threshold, of a person's hearing at different pitches (frequencies). Hearing loss is never uniform over the whole range of sounds, from low to high pitch, so it is necessary to test the hearing with sounds of different pitches. In people with a hearing defect, audiometry can give warning of factors causing hearing loss so that these can be avoided. It also helps to determine the suitability, and best kind, of a hearing aid and helps in decisions about surgery.

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audiometry

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Synonyms for audiometry

noun the measurement of hearing

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Related Words

noun measuring sensitivity of hearing

Related Words