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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

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Pure Tone Audiometry

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Pure tone audiometry l.jpg

Pure Tone Audiometry

SPA 4302

Summer 2007


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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


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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

  • ______________________


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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


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The Clinician’s Role

  • Convey task instructions to patient

  • Ensure understanding

  • Patient position

    • ________________________________________________________________________________________


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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


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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


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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.


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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:


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The Audiogram

  • Thresholds by frequency

  • Hearing by air and bone transmission


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Severity of Hearing Loss


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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


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Air-Conduction Audiometry


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Bone-Conduction Audiometry

  • 3 Mechanisms of Bone Conduction

    • _______________ Bone Conduction

    • ____________ Bone Conduction

    • ______________ Bone Conduction

  • Bone Oscillator Placement

    ___________,

    or, _________


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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)


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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.


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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!


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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

Insert Phones >60 dB


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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 __________________


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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.


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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 ___________


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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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