Otoacoustic Emissions Flashcards
Otoacoustic emissions is a test of _________ function.
Cochlear
Otoacoustic emissions tests are (subjective/objective)
Objective
Otoacoustic emissions do not indicate hearing ________
sensitivity
The gold standard for hearing sensitivity is:
pure tone audiometry
low-level acoustic signals of cochlear origin that may be recorded within the ear canal
Otoacoustic emissions (OAEs)
OAEs are sounds from the cochlea that are transmitted back through the _____ ear to the ______
middle ear to the external ear canal
OAEs are generated as a byproduct of:
the active process in a normal cochlea (the hair cells)
The most probable origin of OAEs are the:
outer hair cells
OAEs are absent in cases with:
outer hair cell loss
any signal presented to the ear has two components:
forward transmission
backward transmission
when the signal reaches the outer hair cells, the active processes generated by the OHCs causes a ‘ripple’ that moves backward along the traveling wave.
The ‘ripple’ is transmitted back through the ossicular chain in the middle ear and then converted to an acoustic signal by the TM.
This is called:
Backward transmission
The signal proceeds through the auditory system in an efficient manner.
This is called:
Forward transmission
Forward transmission travels along the ________
normal auditory pathway
During forward transmission the TM:
acts as a ‘microphone’
During backwards transmission the TM:
acts as a ‘loudspeaker’
The acoustic signal/acoustic emissions is very ______, ranging from __ to __ dB SLP, and is directly related to the level of the stimulus.
small; 0 to 20
Emissions only occur in _____ cochlea
Healthy - the outer hair cells need to be functioning in order to produce emissions
Technology to test OAEs
A probe assembly is seated in the ear canal (similar to tympanometry). The probe contains two ports:
1. Loudspeaker
2. Microphone
The microphone picks up the low level emissions and feeds them to a computer for signal averaging
Testing OAEs is subjective/objective and noninvasive/invasive.
Objective and noninvasive
What are the two types of OAEs?
Spontaneous OAEs Evoked OAEs (2 - Transient Provoked, Distortion Product)
Type of OAE that occurs in the absence of acoustic stimulation
Spontaneous OAEs
Type of OAE where a stimulus is required to elicit a response
Evoked OAEs
Spontaneous OAEs are very ____ level: about ___ to ___ dB SPL
low level; -10 to 10 dB SPL
Spontaneous OAEs ____ in size and ____ in old age. They are ____ in frequency regions with a hearing loss.
decrease in size and disappear in old age.
(T/F) Spontaneous OAEs have no diagnostic significance.
True - they are not used clinically
About ____% of people with normal cochlea have spontaneous OAEs
50%
OAEs elicited using a click stimulus
Transient Evoked OAEs (TEOAE)
In transient evoked OAEs, the characteristics of the click includes:
- clicks stimulate a wide range of frequencies along the basilar membrane
- produces a wide range of OAEs across frequencies
- they occur about 4 msec after the onset of the stimulus and last about 10 msec
- they are small in amplitude but stable over time
- the amplitude of the emissions grows nonlineraly with the stimulus level and eventually plateaus
- usually present between 1000 and 5000 Hz in normal ears
- absent at frequencies with thresholds >30 dB HL
these OAEs are evoked by presenting two tones simultaneously; the two tones interact to produce a third tone
Distortion product DPOAE (a type of evoked OAE)
In distortion product OAEs, the third tone can be calculated based on the relation between the two tones. This formula is:
(2F1-F2), where F2 is the higher of the two frequencies
Distortion product OAEs are present in _____ ears for frequencies between ____ and ____ Hz
normal ears; 1000 and 8000 Hz
Distortion product OAEs are ____ in amplitude
small
In distortion product OAEs results below ____ Hz are often contaminated by background noise
2000
Distortion product OAEs are absent in individuals with thresholds ______ dB HL
> 40 dB HL
Transient evoked OAEs, are _____ in amplitude, but ____ over time.
small; stable
we use DPOAE’s when we are interested in:
more specific frequency information
Transient evoked OAEs are present at frequencies between ____ and ____ Hz in normal ears.
1000 and 5000 Hz
Transient evoked OAEs are absent at frequencies with thresholds ______ dB HL
> 30 dB HL
In relation to hearing sensitivity, OAEs:
Are not an indication of hearing threshold - the emissions are cochlear responses
Results of OAEs can be used to tell if there is or is not a:
cochlear hearing loss at specific frequencies
DOES NOT tell us the degree of loss
After you look at the results, you only know if the thresholds are better than ____ dB HL for TEOAEs or better than ____ dB HL for DPOAEs and only for ______ frequency regions.
30; 40; specific
______ pressure in the middle ear affects the response to OAEs; the largest OAEs occur at the tympanometric peak pressure
Negative
Presense of middle-ear liquid will _______ OAEs
obliterate
Clinical application of OAEs: (3)
- Identify individuals with potential hearing loss - newborn hearing screening, difficult to test patients, functional hearing loss
- Monitor changes in cochlear function - ototoxicity, progressive hearing loss, noise exposure
- Differential diagnosis (cochlear vs. neural) - OAE measures are useful for narrowing the site of lesion to areas peripheral or central to the outer hair cells.
