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					Pure Tone Audiometry




      SPA 4302
     Summer 2007
       The Pure-Tone Audiometer
• Electronic device that generates tones for
  determining _________________
• Manufactured to specifications of the American
  National Standards Institute (ANSI)
• Air/Bone Conduction
• Testable frequencies (A/C): 125, 250, 500, 750,
  1000, 1500, 2000, 3000, 4000, 6000, 8000 Hz
• Testable frequencies (B/C): ___ through _____ Hz
• Masking control available
              Test Environment
• Background noise may affect audiometric results
  by __________ thresholds
• Three ways room noise may be ___________
• Earphone enclosure device
• Insert earphones – foam tipped receivers that are
  inserted directly into the ears
• ______________________
             The Patient’s Role
• Patients must be aware that they are to indicate
  when they hear a tone
• Patient response: hand raise, finger raise, signal
  button, vocal response, play
• False responses
  – False negatives: patient _______________________
    __________; misunderstood or forgotten instructions,
    feigning or exaggerating loss
  – False positives: patients responds when
    _______________________ – usually occurs when
    there are long silent periods in the test
            The Clinician’s Role
• Convey task instructions to patient
• Ensure understanding
• Patient position
  – ____________________________________________
    ____________________________________________
      Air-Conduction Audiometry
• Specifies ______________ at various frequencies
• Can’t tell whether deficit is conductive or
  sensorineural, or mixed
• Earphone placed with diaphragm aimed directly
  over ____________
• Be careful of canals that collapse due to the
  pressure of the earphones – use ______________
  if this is a potential problem
      Air-Conduction Audiometry
• Test the known or suspected ___________ first
• Begin at 1000 Hz – easily heard by most and high
  test-retest reliability
    ORDER of FREQS: 1000, 2000, 4000, 8000,
            recheck of 1000, 500, then 250
• Test at the octave points and the mid-octaves (750,
  1500, 3000, 6000 Hz) if there is a difference of 20
  dB or more between adjacent octaves
Measuring a Threshold at Each Freq.
• Start presenting pure tones at ________ HL
  – No response? Raise the level to 50 dB HL
  – Still no response? Raise the level in 10 dB increments
• Whenever person responds, _____________ dB
• Whenever no response, ________________ dB
• Threshold=the lowest level at which the patient
  can correctly identify the tone presentation at
  least 50% of the time, with a minimum of 3
  responses at a given level.
        Air-Conduction Audiometry
• The Audiogram
  – Frequency (in hertz) on the x-axis, Intensity (in dB
    HL) on the y-axis
  – Moving left to right, frequency increases; moving top
    to bottom, intensity increases
  – Symbols are placed to correspond to threshold at a
    given frequency:
         Air conduction Bone conduction Air—Masked Bone—Masked

Right         O                                        [
                            <
Left          X                                        ]
                            >
   The
Audiogram
• Thresholds
  by frequency

• Hearing by
  air and bone
  transmission
Severity of Hearing Loss
      Air-Conduction Audiometry
• Pure-tone average (PTA)=average of air
  conduction thresholds obtained at ___, _____, and
  _____ Hz in one ear
  – Useful for predicting threshold for speech
• Percentage of Hearing Impairment
  – Ignores audiometric configuration and looks only at
    average hearing loss
  – Often confusing and misleading to patients
Air-Conduction Audiometry

    PTA (dB)   Degree of Communication
                        Impact
      0-15          None
     16-25          Slight
     26-40        _______
     41-55        Moderate
     56-70     Moderately Severe
     71-90         ______
      > 91        Profound
     Bone-Conduction Audiometry
• 3 Mechanisms of Bone Conduction
  – _______________ Bone Conduction
  – ____________ Bone Conduction
  – ______________ Bone Conduction
• Bone Oscillator Placement
  ___________,
       or,                            _________
     Bone-Conduction Audiometry
• Occlusion Effect
  – When the ears of patients with normal hearing or SNHL are
    covered or occluded, there is an _________ in intensity of sound
    delivered via a bone oscillator
  – Affects ________ Hz and below
  – Result of increase in SPL in the ear canal when the
    outer ear is covered
  – Markedly decreased when insert phones are used (as
    opposed to supra-aural headphones)
     Bone-Conduction Audiometry
• No matter where the oscillator is placed, you can
  never be sure which cochlea is being stimulated!
  (more on this to come)
• Frequencies usually tested:
  – 250, 500, 1000, 2000, and 4000 Hz
• Symbols for bone conduction are only connected
  on the audiogram (with dashed lines) when there is
  a __________ or __________ loss.
        Audiogram Interpretation
Look at:
• hearing sensitivity by AC
• hearing sensitivity by BC
• AC/BC difference (a.k.a. the air-bone gap)
       No air-bone gap = ________________
 AC worse than BC = ______________ hearing loss

• Watchout: low frequencies at high levels via BC
  can be perceived as a __________ signal!
  Another Thing to Watch Out For:
• Cross Hearing: sound delivered to one ear but
  perceived in the other ear.
• Interaural Attenuation (IA)—How much sound it
  takes to reach the other side:
  – Air conduction IA = __ dB
  – Bone conduction IA = __ dB
• Danger for cross-hearing
  – For AC—If AC threshold in the test ear, minus IA, is
    greater than or equal to the BC threshold of the
    opposite ear
  – For BC—If Air-bone gap of test ear exceeds ___ dB
                       Masking
• Masking—keeping the non-test ear ―busy‖ in order
  to ensure that it is actually the test ear which is
  responding
• Noises used to mask:
  – ____________—has approximately equal energy per cycle &
    covers a broad range of frequencies
  – _____________—made up of frequencies that immediately
    surround the pure tone being tested
• Insert earphones recommended because:
  – They lessen the ____________
  – They provide much more __________________
           Effective Masking:
          Calibration of the noise

• dB EM (Effective Masking) describes the level to
  which a threshold will shift in the presence of a
  given level of noise

• So, 45 dB EM should raise the threshold for a tone
  to 45 dB HL in the ear in which both are
  presented.
                    Masking
• Masking for air conduction
  –   ―Shotgun‖ Approach
  –   Minimum-noise method
  –   Maximum-noise method
  –   ____________ method
• Masking for bone conduction
  – Similar to air conduction
  – Beware of _____________, and ___________
       Computerized Audiometry
• Using a device remotely operated by a computer
  and data is stored
• Computer can control all aspects of testing and
  masking and analyze patient responses
• Used more often for __________, ___________,
  and ____________ applications (large number of
  people to test)

				
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