Audiometry


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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 levelsenlarge picture
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.
References in periodicals archive ?
Comparison of mean pre- and postoperative pure-tone audiometry results 500 Hz 1,000 Hz 2,000 Hz 4,000 Hz Air-conduction threshold Preoperative (dB) 58.8 55.5 45.5 46.1 Postoperative (dB) 19.4 20.5 20.0 20.0 p Value <0.005 <0.005 <0.01 <0.01 Air-bone gap Preoperative (dB) 41.6 35.5 21.1 27.3 Postoperative (dB) 4.4 7.2 1.7 2.8 p Value <0.005 <0.005 <0.01 <0.005
Intraoperative audiometry. Laryngoscope 1995;105(2):214-16.
Speech audiometry findings were consistent with the pure-tone findings.
Based on the above, the objective of this study was to compare the findings for the minimum levels of air and bone pathways response between Visual Enhancement Audiometry and ASSR in children aged six to 12 months, with and without conductive impairment.
Subjects and grouping: Of the 134 enrolled patients, 120 cases (240 ears) with complete data of pure tone audiometry and acoustic immittance test were selected as an AN1 group.
The data collection process involved the following steps: inspection of the external auditory canal; the whispered voice test; and pure-tone and vocal audiometry.
However, a patient who has limited responsiveness may be required to undergo the same audiological evaluations, except speech audiometry. Patients who are responsive as well as those who have limited responses can undergo both behavioural and objective testing.
Caption: Figure 4: Pure Tone Audiometry recorded one, 14, and 60 days after onset of sudden hearing loss in the left ear (second episode).
Results: Pure tone audiometry (PTA) of 448 industry workers showed that 39(8.71%) had sensorineural hearing loss and 8(1.78%) had conductive hearing loss.
Postgame audiometry was conducted after the official's departure from the ice.
Hearing was assessed using Pure Tone and High Frequency Audiometry up to 12 KHz and Oto-Acoustic Emissions up to 6 KHz at the time of initiation of ART (Baseline), 3rd month and 9th month.
If proven to be accurate and comparable to the gold standard pure tone audiometry, it could become a revolutionary screening tool for detecting hearing impairment as these devices are very popular among people from all spectra and much cheaper compared to the conventional audiogram.