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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

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)