HIS 125 - The Audiologic Evaluation


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HIS 125 - The Audiologic Evaluation

  1. 1. THE AUDIOLOGIC EVALUATION• Critics of clinical audiology assertthat audiometry can bedelegated to a minimally trainedtechnician, since these tests havethe appearance of being quitesimple to administer.
  2. 2. THE AUDIOLOGIC EVALUATION• The assumption that audiometrycan be administered by someonewith minimal understanding is afailure to recognize the complexityof the principles underlyingaccurate audiometric assessment.
  3. 3. THE AUDIOLOGIC EVALUATION• Pure-tone audiometry hasdeveloped from the basicprinciples of the tuning fork tests.• There are many problems inherentin the use of tuning forks, andresults can be variable.
  4. 4. THE AUDIOLOGIC EVALUATIONFor example: Patients withlongstanding hearing loss have lostthe ability to localize sound and areapt to provide tuning fork test resultsthat are inconsistent with theirhearing loss.
  5. 5. THE AUDIOLOGIC EVALUATION• However, the value ofunderstanding tuning fork testsexist in modern audiometry. Everyaudiometer used in diagnostictesting has the capacity topresent tones by air conductionand bone conduction.
  6. 6. THE AUDIOLOGIC EVALUATION• The comparison of air and boneconduction results provides thebasis for determining if middle eardysfunction and conductivehearing loss exists.
  7. 7. THE AUDIOLOGIC EVALUATION• The two tuning fork tests which aremost commonly used inaudiometry are:1. The Weber test2. The Rinne test
  8. 8. THE AUDIOLOGIC EVALUATION• The Weber testWhen the tuning fork is placed atthe mid-line of the forehead and itstone/sound localizes to the betterear; this indicates that the oppositeear has the greatest sensorineuralloss. (It determines the better cochlea)
  9. 9. THE AUDIOLOGIC EVALUATION• The Rinne testThis compares the loudness of thetone/sound presented by first bonethen air conduction. Asensorineural loss is determined ifthe air conduction sound is heardlouder or longer than the boneconduction. (a “positive Rinne”)
  10. 10. THE AUDIOLOGIC EVALUATION• The Rinne testA “negative Rinne” result revealsthe presence of a conductivehearing loss.
  11. 11. THE AUDIOLOGIC EVALUATION• Finding a THRESHOLD is defined asthe minimum effective soundpressure that is capable ofevoking an auditory sensationwhich the patient/client willrespond to fifty percent of thetime.
  12. 12. THE AUDIOLOGIC EVALUATION• The pure tone audiogram isobtained by establishing air-conduction and bone-conductionpure-tone thresholds at severalfrequencies especially 500Hz,1000Hz, 2000Hz, 3000Hz, 4000Hz.
  13. 13. THE AUDIOLOGIC EVALUATION• During air-conduction testing, theentire auditory system is underexamination.• Air conduction thresholds areaffected by influences from thepinna, external and middle ear,and cochlea.
  14. 14. THE AUDIOLOGIC EVALUATION• During bone –conduction testingthe middle ear is bypassed andthe result represents an estimationof cochlear function of the ear.
  15. 15. THE AUDIOLOGIC EVALUATION• Bone Conduction TestingThe major problem, unique to themeasurement of bone-conduction,Is the lack of effective acousticseparation of the two cochlea.Bone conduction activates bothcochlea simultaneously and nearlyequally.
  16. 16. THE AUDIOLOGIC EVALUATION• Bone Conduction TestingWeber test results can provideinformation as to the first ear to test.Always perform bone-conductionon the ear which the Weber testlateralizes to.Note: There is no need to maskwhen no air-bone gap is revealed.
  17. 17. THE AUDIOLOGIC EVALUATION• NOTE• With today’s digital hearinginstruments, it is critical to alsomeasure the half octavesdisplayed on the audiometer.• Half octaves normally displayedare 750Hz, 1.5K, 3K, 6K.
  18. 18. THE AUDIOLOGIC EVALUATION• NOTE• When more that a twenty decibeldifference is found betweenoctaves (500Hz, 1000Hz, 2000Hz,4000Hz, 8000Hz) it is alsorecommended to measure thathalf octave.
  19. 19. THE AUDIOLOGIC EVALUATION• There are three methods used toby the tester to establish puretone thresholds. They are:1. Ascending method2. Descending method3. Bracketing method
  20. 20. THE AUDIOLOGIC EVALUATION• You have learned the bracketingmethod (five decibels up—ten decibelsdown). It is a combination of theascending and descendingmethod.• We will continue to use thismethod in our audiometric testingprocedure.
  21. 21. THE AUDIOLOGIC EVALUATION• Assessing Hearing Handicap and Disabilityfrom Pure Tone Audiometry1. Hearing handicap means thedisadvantage imposed by a hearing loss.2. Hearing disability is the determination ofcompensation for the hearing loss.Let’s review Northern, chapter four, page #50.(The hearing loss “label” based upon average hearingloss level revealed from 500, 1K, 2K average results)
  22. 22. THE AUDIOLOGIC EVALUATION• Speech audiometry attempts tomeasure two clinical quantities.They are:1. Speech Recognition Thresholds(SRT)2. Word Recognition Ability (WR)
  23. 23. THE AUDIOLOGIC EVALUATION• SPEECH RECEPTION THRESHOLDThis test uses thirty-six spondeewords (two-syllable words withequal stress on both syllables).
  24. 24. THE AUDIOLOGIC EVALUATION• SPEECH RECEPTION THRESHOLDAudiometers have been calibratedso that there is close agreementbetween the revealed pure toneaverage and speech receptionthreshold results—within fivedecibels of each other.
  25. 25. THE AUDIOLOGIC EVALUATION• SPEECH RECEPTION THRESHOLDWhen there is a large discrepancybetween the PTA and the SRT, thismay be one of the first indicationsof nonorganic hearing loss.If the SRT is substantially better thanthe PTA other tests may bewarranted.
  26. 26. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGThese are administered atsuprathreshold levels.They consist of fifty word lists of wordsthat are phonetically balanced (PBwords).This represents the frequency ofoccurrence of sounds in everydayEnglish.
  27. 27. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGThe variabilities introduced by live-voice speech testing make thatapproach unacceptable for diagnostictesting.The use of recorded speech stimuliensures that exactly the same stimulusis presented on test-retest conditions.
  28. 28. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGMost WR word lists are administeredat thirty, forty or fifty sensation levels(above threshold average)When PB max tests are not used,most WR word lists are presented atthe patient/client’s mostcomfortable listening level (MCL).
  29. 29. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGPB max tests are used in diagnosticevaluations to determine if a retro-cochlear lesion may be present.When the signal/loudness isincreased, the WR score willbecome worse.
  30. 30. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGAlso, when WR scores are grosslypoorer relative to the revealedthresholds--such as a forty decibelPTA hearing loss with WR scores lessthan twenty-five percent; a retro-cochlear problem may exist.
  31. 31. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGGenerally, those with conductiveloss have excellent WR scores.Those with cochlear hearing losshave poorer WR scores which willbe also be consistent with a greaterdegree of hearing loss.
  32. 32. THE AUDIOLOGIC EVALUATION• WORD RECOGNITION TESTINGWhen unusually poor WR results arerevealed relative to thresholdresults, a neural lesion may bepresent.
  33. 33. THE AUDIOLOGIC EVALUATIONRoutine audiometric tests do notprovide information about factorsaffecting the centralhearing/auditory pathways.Speech-in-noise tests are muchmore revealing for identifyingCentral Processing Disorders.