Pure tone Audiometry

  1. Reliability of a hearing test (4 factors)
    calibration, test environment, examiners expertise, patient performance
  2. Pure tone audiometry
    • tests hearing sensitivity by air and bone conduction
    • freq range 125-8000
    • intensity range -10 to 120 db HL
  3. Test environment
    background noise may elevate threshold (can insert headphones or use a sound treated chamber, don't try to measure 0 dB HL)
  4. Patient's role: Variables affecting the test
    age, education, willingness, motivation, IQ
  5. Threshold of hearing sensitivity
    the lowest level needed  for a person to detect the presence of a signal 50% of the time (barely audible tone)
  6. basis for pure tone audiometry
    establish auditory thresholds at different frequences
  7. two types of false responses
    • false negatives: patient may have forgotten their role or misunderstood, can suggest hearing is worse than it is, malingerer
    • False Positive: can be frustrating, overly motivated patient
  8. patient's position during test
    • patient should not be able to see the clinician
    • -seat the listener at a right angle to the clinician
  9. Air conduction Audiometry
    • can only specify the degree of hearing loss not the type
    • -
  10. Modified Hughson Westlake Method: a compromise between accuracy and time
    • measure a threshold for each frequency to get a base
    • 1) choose a freq
    • 2) adjust the dB to see when they can hear it.
    • 3) go up by 10 then once they hear it go down by 5dB to see if they can hear it
    • 4)if not then go back up to the original intensity level that they could hear and that becomes your threshold
  11. Bone conduction Audiometry
    • determines hearing levels at the cochlea
    • when used with AC thresholds they can tell us sensorineural hearing loss, conductive hearing loss, mixed hearing loss
  12. Why transducer on mastoid process? (2)
    • 1. tones are louder at the MP in NH listeners
    • 2. each mastoids nearness to the test ear (although we know that it does not just test this one ear but both)
  13. masking threshold
    40dB, anything higher will cross over to the opposite ear
  14. when to mask?
    • -when air bone gap is 10dB or greater
    • -if the difference between ears is more than 40dB
    • -mask the better ear
  15. no air bone gap
  16. conductive loss
    air threshold is out of normal range but bone is within normal range
  17. mixed loss
    air and bone are both out of normal range, and there is an air bone gap
  18. O
    right unmasked AC 40 dB threshold
  19. X
    left unmasked AC 40 dB threshold
  20. triangle
    ac right masked
  21. square
    left ac masked
  22. V
    BC forhead unmasked
  23. <
    right BC unmasked
  24. >
    left BC unmasked
  25. [
    left BC masked
  26. ]
    right BC masked
  27. Air reading
    can only read up to 100dB on the audiometer
  28. bone reading
    can only go up to 70dB on the audiometer
Card Set
Pure tone Audiometry
Pure tone Audiometry