Week 5: DPOAEs Flashcards
(32 cards)
What are DPOAEs
distortions resulting from 2 tones presented together (looking at the interference between the 2)
—moderately loud sounds that are close together in freq
what is a basal distortion
has a higher frequency than the signals used to create it
what is an apical distortion
has a lower frequency than the signals used to create it
what would happen to DPOAEs if there is hair cell loss at F2
no DPOAE
what is higher in frequency: F1 or F2
F2
what would happen to DPOAEs if there is hair cell loss at F1
no DPOAE
what would happen if there was hair cell loss at 2F1-F2
there would still be interference between the two frequencies, so distortion would still be generated
—this is a mixed OAE because distortion and reflection and here the response would exist, but would not have the expected amplitude
HL in audiogram is correlated with frequencies at F1 or F2?
F2
what are the 2 theories of DPOAE propagation
1) backward traveling theory
2) compressional wave
- –research supports compressional wave
3 factors that would affect the measurement of DPOAEs
- status of the external and middle ear
- fit if the probe in the external canal
- –the depth of insertion is important to avoid standing waves because the deeper the probe is makes the cavity smaller, creating a higher resonance frequency hopefully above that of the tones used
- noise (ambient and physiological)
DPOAE test parameters: stimulus frequency
- uses 2 stimuli: F1 which is lower in frequency and F2 which is higher (aka primary)
- –the ratio between F2/F1 should be about 1.2 (between 1.15-1.3)
- the cubic difference tone is what is being measured and is 2F1-F2
- multiple sets of frequencies are presented within a given octave (between 2-8/octave)
fine structure of DPOAE stimulus frequency
- is high resolution and shows the micropattern of fluctuating DPOAE levels
- obtained by measuring every 100-200 Hz
- really shows the 2 components of distortion and reflection
DPOAE test parameters: stimulus intensity
generally between 40-70 dB SPL
- –below 40 is too low to generate measurable response
- –above 70 is loud enough that OHCs done amplify so can’t measure response of OHCs
DPOAE intensity of F1 and F2
L1 and L2 for F1 and F2
- –L1-L2= 10 to 15 dB
- –L1 is generally 65 dB SPL
- –L2 is generally 55 dB SPL
- **L1 is louder
- ——–can have L1=L2, but then the response is 3dB less in amplitude
number of tests as DPOAE parameter
will the test repeat on its own?
- you can chose this
- you want it to run twice to check for respeatability
2 ways DPOAEs can be displayed
1) DP-input-output function
- –less commonly used
- –increases F1 level and measure response amplitude (increase intensity of the same frequency)
2) DP-gram
- –clinically most often used
- –plots different frequencies on x-axis and is done at one intensity level (65 and 55 dB)
- —–x-axis represents the primary frequency (F2)
- –is associated with the configuration of the audiogram
* **same intensity, different frequencies
DPOAE test protocol for infant hearing screening
- intensity: L1=65 L2=55
- frequency ratio: 1.21
- frequency range: 2000-4000 Hz
- 4-5 frequencies per octave
DPOAE test protocol for general diagnostics
- intensity: L1=65 L2=55
- frequency ratio: 1.21
- frequency range: 500-8000Hz
- 3-5 frequencies per ocatve
DPOAE test protocol for ototoxicity monitoring
- intensity: 66-55; 55-45; 45-35
- frequency ratio: 1.21
- frequency range: 2000-8000
- 8 per ocatve
reliability with DPOAEs
- have good reliability
- do a test/ retest
- want responses within 2 dB between the different tests, if it is more it is not reliable and should be repeated
should you start with high or low frequencies with DPOAEs
start with high and then go to low because ambient noise is louder at lower so it will want to keep going and keep measuring the lows. if testing a child, they might quit cooperating within this time. if you test highs first and they quit at least you have some usable data (and the high frequencies are what we really care about)
Boys-Town normative data for DPOAEs
- based on norms of large number of people with HL and normal hearing to see where the amplitude of responses falls
- plotted the 95th %ile of hearing impaired as the top line
- plotted the 90th %ile of hearing impaired the second line from the top
- plotted the 10th %ile of normal hearing the 3rd line from the top
- plotted the 5th %ile of normal hearing as the bottom line
- —-overall, the colored area is where they overlap and is called the area of uncertainty
- —-in general, above this area is probs normal, below the area is probs hearing loss, and within the area is abnormal
creating own normative data for DPOAEs
- take a normal hearing group mean +/- 2 SD
- this will give the 10th and 90th %ile for normal hearing
- collect and average the DP amplitude and noise floor
shortcut for not having norms for DPOAEs
basically, if the response is above 0dB SPL amplitude it is normal and below 0 DB SPL is absent or abnormal
—only reason to use is if there is no normative data
