midterm Flashcards
otoacoustic emissions (OAEs)
emissions that are detected by placing a microphone within the ear canal that are being measured from the cochlear
-can be spontaneously or can be evoked by a sound stimuli
OAEs are related to the proper function of the ______
outer hair cells
what systems are involved with OAEs
outer, middle and inner ear, cochlea and the efferent system
list some factors that can influence OAE results
age, gender, ear difference, binaural effects, genetics, race, body temp and position, state of attention, poor probe placement or seal, things within the canal, uncooperative patient and noise
list some factors within the middle ear that can impact an OAE
tubes, perforations, fluid and negative ME pressure
outer hair cells
3 rows arranged that act as biochemical amplifier’s
-they have the ability to change their lengths in the response to stimuli
-motility allows us to be sensitive to soft sounds
-active process
inner hair cells
1 row arranges in a linear pattern that act as a sensory receptor
-transforms sound vibrations from the OHCs into an electrical signal that travels inward
-passive process
how does a traveling wave relate to the hair cells
the traveling wave causes the hair cells to shorten and elongate which causes the basilar membrane to move
-this causes those OHCs to move which is vital for basilar membrane movement
what is a overview of the process of an OAE
probe insertion, inward propagation, electromotility action, outward propagation, hits microphone and is recorded
inward propagation
the inward movement of the stimulus
-passes through the outer, middle and turns around in the inner ear
electromotility
the changing in length of the OHCs as they shorten and lengthen
-helps trigger an OAE to be recorded
outward propagation
the outward movement of the measurement
-what is reflected
explain the process in the inner ear during a OAE recording
-stimulus arrives and invokes movement of the basilar membrane
-this causes OHCs to move, their sterocilia will bend which changes the potential
-changes in voltage lead to length changes
-this action has a feedback effect on the membrane which causes it to vibrate and amplify the signal as it passes onto the IHCs
-from the IHCs it goes to the brain, but out signal that we are measuring gets reflected outward
explain ions in terms of the hair cell movement
ions rush in and out which results in changing the membrane potentials within the hair cells
-these changes cause electromotility
what is the relation between efferent connections and OAEs
the efferent system is a small part of OAEs
-the role is unsure however it should be included when discussing OAEs
what would occur is we put in too high of a stimulus
the stimulation of inner hair cells may occur
-plus we could no longer compare it to norms as it is playing outside of what the norms fall under
what are the three types of OAEs
transient evoked, distortion product and spontaneous
transient evoked OAEs (TEOAEs)
most used within NBHS but can be effective for validating testing
-done with the usage of clicks as a broad band stimuli
-within the probe, one sound playing and one microphone
what are the stimulus protocols for TEOAEs
present at 80-85 dB SPL
-rate at less then 60/second
-can play down to 74ish dB SPL
explain the measurement process for TEOAEs
completed by using time synchronous averaging
-alternating responses are stored in memory banks, A and B
-data that correlates between the two banks are considered a response
-data that does not correlate are considered noise
what is seen on a result screen for TEOAEs
stimulus, frequency response, stimulus intensity level in dB SPL, stability of the series, temporal waveform, spectrum of the TEOAE response and correlation in percentage
describe the difference of a good and bad/absent stimulus for a TEOAE
good : one distinct cycle present
bad/absent : no distinct cycle or can show many rapid signals, ringing occurs with too many cycles shown
what is our response for TEOAEs
emissions and noise floor showing the SNR
what is our response waveform for TEOAEs
SPL and time, looking at reproducibility
what values do we use to determine a pass/refer for a TEOAE
band reproducibility, sweeps completed and SNR
what is the pass/refer criteria for a TEOAE
-band reproducibility : 50% at 1600 Hz, 70% at 2400-4000
-sweeps completed : 40-50
-SNR : 3-6 dB
-absolute amplitude : greater than or equal to 10 dB SPL
pass TEOAE means…
normal or near normal peripheral hearing for the specified frequency region
refer TEOAE means ….
further testing is needed
distortion product OAEs (DPOAEs)
most common type, a frequency specific responses
-two pure tones are presented at the same time
what are the stimulus protocols for DPOAEs
two tones are being presented at the same time
-L1 and L2 (aiming for 65 dB and 55 dB)
-f1 and f2, with a frequency ratio of at least 1.2
-the two signals are being presented to evoke a signal
L1 and L2
the two intensity levels being presented in a DPOAE
-separated by around 10 dB
-65 dB for L1, 55 dB for L2
f1 and f2
primary tones being played
-lower (f1) and higher (f2) frequencies
what are the recording parameters of a DPOAE
the microphone/probe is placed in the outer ear and the averaging of the ear canal sound pressure occurs in response to two stimulating pure tones called f1 and f2
explain the measurement process for DPOAEs
created as a by product of a nonlinear amplification of the basilar membrane motion due to movements of the OHCs
-amplitude of the signal ie being measured at the DP frequency
-presence is dependent on hearing sensitivity within the region of the primaries
what is seen on a result screen for DPOAEs
DP - absolute amplitude by frequency
NF - noise floor (noise present in the room)
SNR (DP-NF) - the interference of the amplitude with noise
distortion product (DP)
our absolute amplitude that we are recording
-DP = 2f1-f2
-being plotted with out f2
what is our response for DPOAEs
our DP and the SNR
-absolute amplitude with the SNR is what we are interested in
what values do we use to determine a pass/refer for a DPOAE
absolute DP value and the relative value (SNR)
what is the pass/refer criteria for a DPOAE
-absolute DP value : greater than -10 dB SPL
-relative value (SNR) : greater than or equal to +6 dB
pass DPOAE means ….
DPOAE is normal, replicated amplitudes are within normal range
refer DPOAE means ….
no replicable DPOAEs are detected at any frequency
what does a combination of a pass and refer of a DPOAE mean ….
some are normal and some are abnormal at different frequencies
spontaneous OAEs (SOAEs)
the first type to be reported, does not required any type of evoking stimuli
-occurs in normal cochleas
-can be detected in 35-50% of the population
in terms of stimulus stability, what is preferred?
higher stability
measurement factors with recording OAEs
noise going into the microphone, ambient test setting, patient breathing, or the rubbing of the tube against clothing or skin
DP-gram
a graphical representation of DPOAE amplitudes as a function of the f2 frequency
gorgagram
a type of DP-gram that represented amplitude as a function of f2 frequency however, it assigns a normal or impaired region based on results
-can only be used with DPOAEs
what is being plotted in a DPOAE
absolute amplitude
-dB SPL as a function of the f2 frequency
how do gorgagram results correlate with potential dB audiogram levels
with normal and present OAEs, you can say hearing thresholds are around 15-20 dB HL
-normal : hearing better than or equal to 20 dB HL
-borderline : hearing is most likely better than or equal to 20 dB HL
-abnormal : hearing is worse than 20 dB HL
if not using a gorgagram, what is the correlation to thresholds
with normal and present OAEs, you can say hearing thresholds are within the 25-30 dB HL range
the presence of OAEs tells us ….
-canal is clear
-middle ear function is normal/near normal
-cochlear sensory function is normal by inference only
the absence of OAEs tells us ….
-may be the blockage of the ear canal
-may be abnormal middle ear function
are OAEs a test of hearing?
no, they are not a direct measure of hearing
-you are able to infer about hearing health of the individual but it cannot be directly inferred for a threshold
some clinical uses of OAEs
assessment of functional HL, differentiation of cochlear vs. retrocochlear, monitoring ototoxicity, tinnitus and noise/music exposure
cross check principle
being able to check the validity of two tests to ensure the results are matching up and can be a valid source of what is occurring
-using 1 electrophysiology test and 1 behavioral test
what does it mean to have a robust recording
with anything robust, you are not able to quantify it
standing waves
cancellations and reinforcements of some sound waves or interaction between stimulus sound wave moving towards the TM and moving out to be measured as an OAE
standing waves are a problem with …
-higher frequencies are at higher risks
-are a problem with DPOAEs
what is the only way to resolve standing waves
place the microphone at the tympanic membrane
-which is not clinically feasible
in terms of TEOAEs, what does reproducibility mean
correlation
-two waves will overlap almost totally
how does the middle ear act as a amplifier
through impedance matching
-pay attention to size difference between the tympanic membrane and the oval window
-results in an increase in sound pressure
