Pure tone testing lecture 2012

Pure tone testing lecture 2012 - 2/9/12 Types of...

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Unformatted text preview: 2/9/12 Types of Audiometers  Clinical (diagnostic) audiometer Pure ­tone Audiometry Basic Components of Audiometers  Power (on/off)  Frequency selector (oscillator)  Intensity selector (attenuator)  Router selector (left, right, both)  Presentation button  Continuous/interrupter selector (on/off)  Patient response indicator  Screening (portable) audiometer  Other components (not all found on portable audiometers)  Masking noise selector and router  Speech channel (microphone, CD, computer)  VU Meter  Talk over/talk back system  Transducer selector 1 2/9/12 Transducers Used in Audiometry  Air ­conduction (AC) transducers TRANSDUCERS  Bone ­conduction (BC) transducers  Microphone for speech testing and communicating with patient   Air ­conduction (AC) transducers   Earphones   Supra ­aural   TDH ­39, 49, 50   Headband   Disposable covers   Insert   ER ­3A or ER ­5A (Etymotic or EAR ­Tone)   Sound field (SF) speakers (varied)   Bone ­conduction (BC) transducer   Radioear B71 or B72   Single transducer (switch sides)   Mastoid vs forehead placement   Disposable foam cuffs   High frequency (circumaural)   Sennheiser HDA 200   Used for special populations 2 2/9/12 Problems with supra ­aural earphones Advantages of insert earphones   Potential ear canal collapse   Sound leakage   No ear canal collapse   No sound leakage   Background noise   Reduced background noise   Lower interaural attenuation   Higher interaural attenuation; therefore less need for masking Microphones in Audiometry   Speech channel microphone Problems with bone oscillator   Limited frequency response   Reduced output limits   Not good for speech testing   Can be felt (vibro ­tactile) in low frequencies/ moderate level   Placement is a little tricky, especially when also putting on supra ­aural earphone   Have to switch sides Pure Tone Testing & Troubleshooting   Talk forward microphone   Talk back or patient microphone 3 2/9/12 Pure Tone Tes:ng   Instructions   With hearing aids on or through audiometer   Headphones and response button   Order of testing Pure Tone Tes:ng   Air conduction   250 to 8000 Hz, octave frequencies plus 3000 and 6000 Hz half octaves   Generally it is recommended to test the better ear first       This lets the patient become comfortable with test procedure Patient is familiar with task when the poorer ear is tested Can give a baseline for comparison Defining Threshold Working definition: A pure ­tone threshold is the lowest sound level of a pure ­tone that the patient voluntarily responds to at least 50% of the time in at least 3 trials at each level. i.e., 2/4 trials (50%) may be needed, but must be at least 2/3 trials (2/3 =67%). Both examples would have had less that 50% at one level lower.   Bone conduction   250 to 4000 Hz, octave frequencies   Usually test in 5 dB HL steps of intensity Pure Tone Tes:ng   Frequency presentation: Hz 2000 Hz 3000 4000 Hz 6000 8000 Hz back to 1000 Hz (reliability) 500 Hz 250 Hz   The above order is typical, but you can be flexible in testing order   If retest at 1 kHz differs by more than 5 dB, start over (Patient may not have understood directions or got used to the procedure)   1000 Guidelines for Audiometry in ANSI (2004) and ASHA (2005). 4 2/9/12 Procedure for Obtaining Thresholds   Modified Hughson ­Westlake (a.k.a.) “up 5, down 10” (or “down 10, up 5”). If no response, increase level 5 dB If response, decrease level by 10 dB   Familiarization phase   Starting point:   30 dB starting point if you suspect fairly well hearing   50 dB staring point if you suspect some hearing loss   Present the first tone:   If patient responds, continue descending in 10 dB steps until no response is obtained   If no response to first tone, increase intensity by 20 dB.   Threshold search phase (bracketing with up 5 down 10) Decibel Level (dB HL)   Ascending 0 5 10 15 20 25 30 35 40 45 50 55 _ + + _ _ _ + _ _ _ + + _ _ (+) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Presentation (Trial) Number Frequency (Hz) Decibels Hearing Level (dB HL) re: ANSI-2004 -10 250 500 1000 2000 4000 8000 Audiogram Key 0 10 20 30 40 50 60 70 80 AC (unmasked) <X < X <X Right Left Ear Ear O X AC (masked) BC (unmasked) <X X < > BC (masked) <X [ No response (on any symbol) Sound-field (non ear specific) S 90 100 110 120 5 2/9/12 “No Response” symbols If no response is obtained at a frequency, a down-pointing arrow is affixed to the bottom of the symbol at the highest intensity the tone was presented. Notice the lower out put limits for bone conduction! Checking Equipment Func:on/Calibra:on   Daily Listening Check   Each day prior to the first use of the audiometer   To ensure that the equipment is in proper working order   To prevent technical errors   To identify problem areas Electro ­acous:c Calibra:on   When   Every 6 ­12 months   Purpose   To ensure test accuracy   Usually done professionally ­ not by audiologist   Can be done by audiologist using sound level meter   If problems found, take appropriate steps 6 ...
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This note was uploaded on 02/09/2012 for the course MUSI 109 taught by Professor Chan during the Spring '10 term at Miramar College.

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