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121 Cards in this Set

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