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121 Cards in this Set
- Front
- Back
Recording of synchronous neural activity generated in the auditory brainstem in response to a transient stimulus
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ABR
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how is ABR recorded?
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Recorded with electrodes
Generated by click (100 microsec) or tone burst |
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Is ABR a true hearing test?
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No...not a true test of hearing and no behavioral response is needed
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where are electrodes put on the clients head?
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top of head, forhead, and behind each ear...4 total
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Which waves are you interested in the ABR?
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interested in first 5
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What do the ABR waves represent?
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neural activity from specific structures in auditory brainstem
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What generates the 5 ABR waves?
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I - distal portion of the VIIIth nerve
II - proximal portion of the VIIIth nerve III - cochlear nucleus IV - generators are uncertain (possibly SOC) V - lateral lemniscus and inferior colliculus |
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Main factor assessed with ABR
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latency
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measure of time in msec
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latency
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time between stimulus presentation and generation of specific waveform
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Absolute Latency
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time between waves
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Inter-peak Latency
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comparison of absolute latencies for wave V(5) between ears
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Inter-aural Latency
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Used to test for retrocochlear pathology
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Neurologic ABR
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What dos neurologic ABR access?
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Assess Absolute, Inter-peak, and Inter-aural latencies
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What would pathology (like tumor) do to ABR?
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eliminate wave or may increase latency
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Presence of pathology should eliminate wave or may increase latency is called
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abnormal neural adaptation
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Used to infer hearing sensitivity
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threshold ABR
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test is very difficult to test populations
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threshold ABR
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What ranged dow threshold ABR test for?
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2000-4000 HZ
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how do you Assess V absolute latency in threshold ABR?
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as stimulus intensity is decreased
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occurs when the sound presented to the test ear (TE) is heard by the non-test ear (NTE)
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Cross-hearing
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what does cross hearing do to a patient's hearing exam?
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give a false picture
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sound presented to TE “crosses over” to the NTE
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Cross-over
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sound which has “crossed over” from TE to NTE is perceived by NTE
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cross hearing
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How does sound cross-over?
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bone conduction
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the amount of the signal “lost” in the cross-over process
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Interaural Attenuation
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Interaural Attenuation is inversely related to
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the contact area between the headphone and the head
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Interaural Attenuation ranges
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40-70 dB HL
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average Interaural Attenuation ranges
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50-65 dB HL
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what are the minimum values for inernaural attenuation?
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minimum value of 40 dB HL for AC and 0dB for BC
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when is IA greater?
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for insert earphones (70-90 dB HL)
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What is the minimum value for insert phones for IA?
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60db
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where is noise presented in masking?
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to NTE & is ALWAYS presented by AC
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Masked threshold symbols
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□, Δ, ], [
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Unmasked threshold symbols
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x, o, >, <
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what does the noise in the NTE do?
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stops it from hearing the cross-over tones
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What types of stimuli are used for testing?
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Pure tones, Speech
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filtered white noise having energy only in narrow bandwidth around pure tone
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Narrow Band Noise
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filtered white noise having qualities of long-term average speech
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speech shaped noise
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what are some good rules of thumb for masking?
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Good instructions for patient.
To determine if masking is needed, know bone conduction thresholds. The air-bone gap is greater than 10dB in the TE. Difference of 40dB or greater of AC threshold of TE and BC threshold of NTE. |
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what causes noise in one ear can cause a threshold shift in the other ear?
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interaction in the Central Auditory Nervous System
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how much does noise in one ear can cause a threshold shift in the other ear?
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5 dB shift in threshold
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when will the tone was heard by the TE
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If a masked threshold remains within 5 dB of the unmasked threshold
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minimum amt that must be added to a tone’s level to effectively mask it
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Minimal Effective Masking Correction (MEMC)
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how many db for MEMC?
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5 db
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what is the formula for Initial Masking Level-BC?
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IML BC=HL(NTE) +MEMC (5dB)+ 10dB SF + OE
OE-occusltion effect SF-safety factor |
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what is the forumla for Initial Masking Level-AC?
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IML AC = HL(NTE) + MEMC + SF
IML AC = HL (NTE) + 15dB |
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the noise is not enough to mask the tone in the NTE.
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Undermasking
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Increase noise, the TE threshold stays the same
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Plateau
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Noise in NTE crosses over to TE and masks it
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Overmasking
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ML(NTE)> IA + BC(TE) + MEMC
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ML(NTE)> IA + BC(TE) + MEMC
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what is masking procedure?
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Proper headphone placement
Tone-TE; start at unmasked threshold Noise-NTE; start at determined IML Activate noise and then present tone. Increase tone 5 dB-no response Increase noise 5 dB-response Plateau-3 consecutive increases in noise |
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what is IA for speech?
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40dB (phones), 60dB (inserts)
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S(TE) – IA > BC( NTE)
IML = SRT(NTE) + MEMC + SF IML SD = Presentation level(TE)- 20dB |
S(TE) – IA > BC( NTE)
IML = SRT(NTE) + MEMC + SF IML SD = Presentation level(TE)- 20dB |
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Instrument used to measure magnitude of sound
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Sound Level Meters
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most exact
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Type O/Lab models
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Type O/Lab models measure
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+0.7dB, 100-4000Hz
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used for exact calibration and reference in lab conditions
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Type O/Lab models
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precise measurement
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Type 1/Precision
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Type 1/Precision
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1dB, 50-4000Hz
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used in lab or field
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Type 1/Precision
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field measurements
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Type 2/General purpose
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Type 2/General purpose
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1.5dB, 100-1250Hz
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limited number of functions, intended for specific uses
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Type S/Special purpose
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overall sound pressure level
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Linear measurement
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De-emphasizes low frequencies
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dBA
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also e-emphasizes low frequencies-not as much
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dBB
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almost linear
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dbC
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what does noise spectrum measure?
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Can measure the spectrum of the noise with octave band filters or third octave band filters
Gives us measurements in dB of each frequency band within the noise. Can determine which frequencies are the loudest. |
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Change in hearing sensitivity following exposure to loud noise. Hearing recovers completely
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Temporary Threshold Shifts
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Change in hearing sensitivity following exposure to loud noise. Hearing does not completely recover
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Permanent Threshold Shifts
aka Noise Induced Permanent Threshold Shift or Noise Induced Hearing Loss |
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______ broadband noise can cause TTS
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75-80 db
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when is TTS greatest?
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2 minutes after exposure
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PTS is smaller or greater than TTS
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ALWAYS SMALLER!
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Loss at ______ increases rapidly for first 10 years of exposure to occupational noise, then plateaus
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4000Hz
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Loss at _____ increases slowly for first 10 years of exposure to occupational noise, then increases progressively.
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2000Hz
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Regulates exposure, monitoring, guidelines
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OHSA
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what does OHSA stand for?
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Occupational Safety and Health Act and administration
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what are the guideslines for OHSA?
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90dBA for 8 hours. As increases past 90dBA, decrease time by ½ for each 5 dB (4 hours for 95dBA).
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defines requirements for hearing conservation programs
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HCA (Hearing Conservation Amendment)
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What are TWA standards?
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All employees exposed to levels of 85dBA TWA (time weighted average-equal to an 8 hour work day)
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when to take baseline audiograms?
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w/in first 6 months of exposure to levels > 85dBA TWA and then take annually
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what do you test for (hz) for baseline audiograms?
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Air conduction-500, 1000, 2000, 3000, 4000, 6000 and 8000Hz
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Significant threshold shift
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greater than 15db
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what are controls for industry?
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admin-schedual rotation
engineering-reduce machine noise hearing protectors |
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Term used to describe people exhibiting hearing loss greater than what is expected
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non organic hearing loss
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Pseudohypacusis
Psychogenic Hearing Loss Malingering Functional Hearing are terms for |
non organic hearing loss
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Non-organic
Malingering Pseudohypacusis Functional are terms for |
someone faking hearing loss
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Hysterical
Psychogenic are terms for |
faking hl is at unintentional level
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what do you say when someone is faking?
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inconsistent results
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stimlus response matrix
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stimulus response matrix
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What is the Strenger test?
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If same sound is presented at both ears, hear image in midline
If increase dB at one ear, image shifts to that ear and only “hear” it at that ear Procedure Present tone to “Good” ear 10 dB > admitted threshold Present tone to “Bad” ear 10 dB < admitted threshold Present at same time (no response is + for pseudohypacusis) (response is – for pseudohypacusis) |
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where do we get OAE from?
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Result of motility of healthy outer hair cells.
Causes signal to be sent “backward” through the middle ear and ear canal. |
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Probe assembly similar to that used for immittance testing
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OAE
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Measurable in the ear with a probe mic
Present in the absence of stimulation |
spontaneous OAE
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where do you generally get spontaneous OAEs?
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More common in right ears
More common in women than men |
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Present sound into system & get something in addition to input stimulus present in ear canal (distortion)
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evoked OAE
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first to describe OAEs
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Kemp in 1978
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click or tone burst presented then complex waveform comes back into ear canal 5-20 msec post-stimulus presentation
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TEOAE
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what is TEOAE's stimulus?
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High Hzs first, then Mid, followed by Low
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ranges of TEOAS
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500 Hz – 4500 Hz (adults) 500-6000Hz (babies and children)
Larger in babies than adults |
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when isn't TEOAS present?
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Present unless loss > 30 dB HL and Absent with conductive HL
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Present two primary tones into system (f1 & f2)
Get a third tone out with Hz |
DPOAEs
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what happens with latency in DPOAEs?
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Latency decreases with increasing stimulus Hz
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when are DPOAEs not present?
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Present unless loss > 50 dB HL
Also absent with conductive HL |
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formulas for DPOAEs
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Present two primary tones into system (f1 & f2)
Get a third tone out with Hz = 2f1 – f2 DPOAE (-60 dB re: Primaries) Strongest when f1 and f2 are between 1000-4000Hz |
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used to Determine if sensorineural hearing loss has cochlear or retrocochlear basis
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site of lesion testing
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loudness recruitment
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cochlear
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abnormal neural adaptation
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retocochlear
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what to do if cochlear?
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hearing aid amplification
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what to do if retrocochlear?
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surgery
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Abnormal perception of the growth of loudness
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Loudness Recruitment
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what happens to cause Loudness Recruitment?
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Loss of OHC
Cochlear site of lesion |
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Neural firing rate to a constant stimulus decreases over time
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neural adaptation
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what causes Abnormal Neural Adaptation?
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Individuals with retrocochlear pathology may exhibit an abnormal, rapid decline in neural firing
Basically, the neurons cannot keep up the level of firing to code the stimulus PI-PB Rollover |
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Can Pt. Detect the presence of a 1 dB increment imposed on a constant tone
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Short Increment Sensitivity Index (SISI)
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explain SISI
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Short Increment Sensitivity Index
Can Pt. Detect the presence of a 1 dB increment imposed on a constant tone? Based on loudness recruitment Present constant tone at 20 dB SL Start increments at 5 dB, 2 dB, then 1 dB Present 20, 1 dB increments and determine how many Pt. can detect |
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what is interpretation of SISI
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Each 1 dB increment detected is worth 5%
> 70% + for cochlear (loudness recruitment) < 30% - for cochlear (normal, retro, conductive) 30 - 70% is difficult to interpret |
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what is tone delay?
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Pts. with normal hearing will start to experience neural adaptation after a few minutes
Pts. with retrocochlear path. should experience abnormal neural adaptation (decay) to a constant intense tone within one minute |
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What is STAT?
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Suprathreshold Adaptation Test
Present tone (500, 1000, or 2000 Hz) 100 dB HL at 500 & 1000 Hz, 105 at 2kHz Present tone for 60 sec. Pt. perceives tone 60 sec. (- for retro) Tone decays within 60 sec. (+ for retro) Recruiting ears may have tough time tolerating these levels |
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test for tone decay
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Suprathreshold Adaptation Test (STAT)
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