Summer 2007 SPA 4302 Pure Tone Audiometry

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 Insert Phones >60 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 Masking for bone 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)