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Audiometry

audiometry, audiometry test
Audiometry from Latin: audīre, "to hear" and metria, “to measure" is a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies1 Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise Acoustic reflex and otoacoustic emissions may also be measured Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and often make use of an audiogram

Contents

  • 1 History and development
    • 11 Mechanical "acuity meters" and tuning forks
    • 12 Pure tone audiometry and audiograms
    • 13 Electrophysiologic audiometry
    • 14 Otoacoustic audiometry
  • 2 Auditory system
    • 21 Components
    • 22 Hearing process
  • 3 Sensory and psychodynamics of human hearing
    • 31 Cocktail party effect
    • 32 Understanding speech
    • 33 Non-linearity
    • 34 Temporal synchronization – sound localization and echo location
  • 4 Parameters of human hearing
    • 41 Frequency range
    • 42 Amplitude sensitivity
    • 43 Impulse response
    • 44 Phase response
    • 45 Temporal processing "gap detection"
    • 46 Distortion products
  • 5 Audiometric testing
    • 51 Normative standards
  • 6 Types of audiometry
    • 61 Subjective audiometry
    • 62 Objective audiometry
  • 7 Audiograms
  • 8 Hearing assessment
    • 81 Hearing loss classification
  • 9 Clinical practice
    • 91 Schools
    • 92 Occupational testing
    • 93 Noise-induced hearing loss
  • 10 Research
  • 11 See also
  • 12 References

History and developmentedit

The basic requirements of the field were to be able to produce a repeating sound, some way to attenuate the amplitude, a way to transmit the sound to the subject, and a means to record and interpret the subject's responses to the test

Mechanical "acuity meters" and tuning forksedit

For many years there were a desultory use of various devices capable of producing sounds of controlled intensity The first types were clock-like, giving off air-borne sound to the tubes of a stethoscope; the sound distributor head had a valve which could be gradually closed Another model used a tripped hammer to strike a metal rod and produce the testing sound; in another a tuning fork was struck The first such measurement device for testing hearing was described by Wolke 1802

Pure tone audiometry and audiogramsedit

Following development of the induction coil in 1849 and audio transducers telephone in 1876, a variety of audiometers were invented in United States and overseas These early audiometers were known as induction-coil audiometers due to

  • Hughes 1879
  • Hartmann 1878

In 1885, Arthur Hartmann designed an “Auditory Chart” which included left and right ear tuning fork representation on the abscissa and percent of hearing along the ordinate

In 1899, Carl E Seashore Prof of Psychology at U Iowa, United States, introduced the audiometer as an instrument to measure the “keenness of hearing” whether in the laboratory, schoolroom, or office of the psychologist or aurist The instrument operated on a battery and presented a tone or a click; it had an attenuator set in a scale of 40 steps His machine became the basis of the audiometers later manufactured at Western Electric

  • Cordia C Bunch 1919

The concept of a frequency versus sensitivity amplitude audiogram plot of human hearing sensitivity was conceived by German physicist Max Wien in 1903 The first vacuum tube implementations, November 1919, two groups of researchers — KL Schaefer and G Gruschke, B Griessmann and H Schwarzkopf — demonstrated before the Berlin Oto-logical Society two instruments designed to test hearing acuity Both were built with vacuum tubes Their designs were characteristic of the two basic types of electronic circuits used in most electronic audio devices for the next two decades Neither of the two devices was developed commercially for some time, although the second was to be manufactured under the name "Otaudion" The Western Electric 1A, developed by <who> was built in 1922 in the United States It was not until 1922 that otolaryngologist Dr Edmund P Fowler, and physicists Dr Harvey Fletcher and Robert Wegel of Western Electric Co first employed frequency at octave intervals plotted along the abscissa and intensity downward along the ordinate as a degree of hearing loss Fletcher et al also coined the term “audiogram” at that time

With further technologic advances, bone conduction testing capabilities became a standard component of all Western Electric audiometers by 1928

Electrophysiologic audiometryedit

In 1967, Sohmer and Feinmesser were the first to publish ABRs recorded with surface electrodes in humans which showed that cochlear potentials could be obtained non-invasively

Otoacoustic audiometryedit

In 1978, David Kemp reported that sound energy produced by the ear could be detected in the ear canal The first commercial system for detecting and measuring OAEs was produced in 1988

Auditory systemedit

Main article: Auditory system

Componentsedit

The auditory system is composed of epithelial, osseous, vascular, neural and neocortical tissues The anatomical divisions are external ear canal and tympanic membrane, middle ear, inner ear, VIII auditory nerve, and central auditory processing portions of the neocortex

Hearing processedit

Main article: Hearing

Sound waves enter the outer ear and travel through the external auditory canal until they reach the tympanic membrane, causing the membrane and the attached chain of auditory ossicles to vibrate The motion of the stapes against the oval window sets up waves in the fluids of the cochlea, causing the basilar membrane to vibrate This stimulates the sensory cells of the organ of Corti, atop the basilar membrane, to send nerve impulses to the central auditory processing areas of the brain, the auditory cortex, where sound is perceived and interpreted

Sensory and psychodynamics of human hearingedit

Cocktail party effectedit

Understanding speechedit

Non-linearityedit

Further information: Fletcher-Munson curves and Equal-loudness contours

Temporal synchronization – sound localization and echo locationedit

Parameters of human hearingedit

Frequency rangeedit

Main article: Hearing range

Amplitude sensitivityedit

Main article: Absolute threshold of hearing

Impulse responseedit

Phase responseedit

Temporal processing "gap detection"edit

Distortion productsedit

Audiometric testingedit

  • objectives: integrity, structure, function, freedom from infirmity

Normative standardsedit

  • ISO 7029:2000 and BS 6951

Types of audiometryedit

Subjective audiometryedit

Subjective audiometry requires the cooperation of the subject, and relies upon subjective responses which may both qualitative and quantitative, and involve attention focus, reaction time, etc

  • Differential testing is conducted with a low frequency usually 512hz tuning fork They are used to assess asymmetrical hearing and air/bone conduction differences They are simple manual physical tests and do not result in an audiogram
    • Weber test
    • Bing test
    • Rinne test
    • Schwabach test, a variant of the Rinne test
  • Pure tone audiometry is a standardized hearing test in which air conduction hearing thresholds in decibels db for a set of fixed frequencies between 250hz and 8,000hz are plotted on an audiogram for each ear independently A separate set of measurements is made for bone conduction There is also high frequency Pure Tone Audiometry covering the frequency range above 8000hz to 16,000hz
  • Threshold Equalizing Noise TEN test
  • Masking Level Difference MLD test
  • Psychoacoustic or Psychophysical Tuning Curve test
  • Speech audiometry is a diagnostic hearing test designed to test word or speech recognition It has become a fundamental tool in hearing-loss assessment In conjunction with pure-tone audiometry, it can aid in determining the degree and type of hearing loss Speech audiometry also provides information regarding discomfort or tolerance to speech stimuli and information on word recognition abilities In addition, information gained by speech audiometry can help determine proper gain and maximum output of hearing aids and other amplifying devices for patients with significant hearing losses and help assess how well they hear in noise Speech audiometry also facilitates audiological rehabilitation management

Speech audiometry may include:

    • Speech Awareness Threshold
    • Speech Recognition Threshold
    • Suprathreshold word-recognition
    • Sentence testing
    • Dichotic listening test
    • Loudness levels determination
  • Békésy audiometry, also called decay audiometry - audiometry in which the subject controls increases and decreases in intensity as the frequency of the stimulus is gradually changed so that the subject traces back and forth across the threshold of hearing over the frequency range of the test The test is quick and reliable, so was frequently used in military and industrial contexts
  • Audiometry of children
    • Conditioned play audiometry
    • Behavioral observation audiometry
    • Visual reinforcement audiometry

Objective audiometryedit

Objective audiometry is based on physical, acoustic or electrophysiologic measurements and does not depend on the cooperation or subjective responses of the subject

  • Caloric stimulation/reflex test uses temperature difference between hot and cold water or air delivered into the ear to test for neural damage Caloric stimulation of the ear results in rapid side-to-side eye movements called nystagmus Absence of nystagmus may indicate auditory nerve damage This test will often be done as part of another test called electronystagmography
  • Electronystagmography ENG uses skin electrodes and an electronic recording device to measure nystagmus evoked by procedures such as caloric stimulation of the ear
  • Acoustic immittance audiometry - Immittance audiometry is an objective technique which evaluates middle ear function by three procedures: static immittance, tympanometry, and the measurement of acoustic reflex threshold sensitivity Immittance audiometry is superior to pure tone audiometry in detecting middle ear pathology
    • Tympanometry
    • Acoustic Reflex Thresholds ART
    • Acoustic reflectometry
    • wide-band absorbance audiometry also called 3D tympanometry
  • Evoked potential audiometry
    • N1-P2 Cortical Audio Evoked Potential CAEP audiometry
    • Auditory brainstem response ABR is a neurologic tests of auditory brainstem function in response to auditory click stimuli
    • Electrocochleography a variant of ABR, tests the impulse transmission function of the cochlea in response to auditory click stimuli It is most often used to detect endolymphatic hydrops in the diagnois/assessment of Meniere's disease
    • Audio steady state response ASSR audiometry
    • Vestibular evoked myogenic potential VEMP test, a variant of ABR that tests the integrity of the saccule
  • Otoacoustic emission audiometry - this test can differentiate between the sensory and neural components of sensorineural hearing loss
    • Distortion Product OtoAcoustic Emissions DPOAE audiometry
    • Transient Evoked OtoAcoustic Emissions TEOAE audiometry
    • Sustained Frequency Otoacoustic emissions SFOAE audionetry - At present, SFOAEs are not used clinically
  • In situ audiometry: a technique for measuring not only the affliction of the person's auditory system, but also the characteristics of sound reproduction devices, in-the-canal hearing aids, vents and sound tubes of hearing aids23

Audiogramsedit

Main article: Audiogram

The result of most audiometry is an audiogram plotting some measured dimension of hearing, either graphically or tabularly

The most common type of audiogram is the result of a pure tone audiometry hearing test which plots frequency versus amplitude sensitivity thresholds for each ear along with bone conduction thresholds at 8 standard frequencies from 250hz to 8000hz A PTA hearing test is the gold standard for evaluation of hearing loss/disability Other types of hearing tests also generate graphs or tables of results that may be loosely called 'audiograms', but the term is universally used to refer to the result of a PTA hearing test

Hearing assessmentedit

Apart from testing hearing, part of the function of audiometry is in assessing or evaluating hearing from the test results The most commonly used assessment of hearing is the determination of the threshold of audibility, ie the level of sound required to be just audible This level can vary for an individual over a range of up to 5 Decibels from day to day and from determination to determination, but it provides an additional and useful tool in monitoring the potential ill effects of exposure to noise Before carrying out a hearing test, it is important to obtain information about the person’s past medical history, not only concerning the ears but also other conditions which may have a bearing on possible hearing loss detected by an audiometric test Hearing loss may be unilateral or bilateral, and bilateral hearing loss may not be symmetrical The most common types of hearing loss, due to age and noise exposure, are usually bilateral and symmetrical Wax in the ear can also cause hearing loss, so the ear should be examined to see if syringing is needed; also to determine if the eardrum has suffered any damage which may reduce the ability of sound to be transmitted to the middle ear

Hearing loss classificationedit

Main article: Hearing loss

The primary focus of audiometry is assessment of hearing status and hearing loss, including extent, type and configuration

  • There are four defined degrees of hearing loss: mild, moderate, severe and profound
  • Hearing loss may be divided into four types: conductive hearing loss, sensorineural hearing loss, central auditory processing disorders, and mixed types
  • Hearing loss may be unilateral or bilateal, of sudden onset or progressive, and temporary or permanent

Hearing loss may be caused by a number of factors including heredity, congenital conditions, age-related presbycusis and acquired factors like noise-induced hearing loss, ototoxic chemicals and drugs, infections, and physical trauma

Clinical practiceedit

Audiometric testing may be performed by a general practitioner medical doctor, an otolaryngologist a specialized MD also called an ENT, a CCC-A Certificate of Clinical Competence in Audiology audiologist, a certified school audiometrist a practitioner analogous to an optometrist who tests eyes, and sometimes other trained practitioners Practitioners are certified by American Board of Audiology ABA Practitioners are licensed by various state boards regulating workplace health & safety, occupational professions, or

Schoolsedit

Occupational testingedit

See also: Workplace health surveillance, Hearing conservation program, and Occupational hearing loss

Noise-induced hearing lossedit

Main article: Noise-induced hearing loss See also: Environmental noise and Industrial noise

Workplace and environmental noise is the most prevalent cause of hearing loss in the United States and elsewhere

Researchedit

  • Computer modeling of patterns of hearing deficit
  • 3D longitudinal profiles of hearing loss including age axis presbycusis study

See alsoedit

  • Hearing test

Referencesedit

  1. ^ Patrick J Willems 2004 Genetic hearing loss CRC Press pp 34– ISBN 978-0-8247-4309-3 Retrieved 23 June 2011 
  2. ^ Vashekevich MI, Azarov IS, Petrovskiy AA, Cosine-modulated filter banks with a phase conversion: realization and use in hearing aids - Moscow, Goryachaya liniya-Telecom, 2014 -210 p
  3. ^ ↑ Vonlanthen A Hearing Aids / Vonlanthen A Horst A - Rostov-on-Don: Phoenix, 2009 -304 p

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