Masking Flashcards
What are the 4 characteristics when describing an audiometry test?
Degree
Type
Configuration
Physiologic Basis/ Structural cause
What is the meaning of configuration? (2) and name them:
Descriptive titles
Graph form
Flat
Slope
Reversing Sloping
Precipitous
Cookie Bite
Reverse Cookie bite
High frequency
Left corner
4k Notch
(Remember law of 20 dB)
What is the meaning of Types in audiometry? (1)
Types of HL CHL vs. SNHL
you HAVE to do BC and AC to be able to know the type
What is the meaning of Degree in audiometry? (1)
Descriptive titles
Pure tone average (non-frequency-specific)
Percentage of hearing loss avg (.5,1,2,3 kHz) - 25 dB x 1.5
(non-frequency-specific)
What is the diagnostic for this audiogram?
Normal
What is the diagnostic for this audiogram?
Right Mild Flat CHL
What is the diagnostic for this audiogram?
Left Mild to Moderate Sloping SNHL
What is the diagnostic for this audiogram?
Left Moderate to Severe sloping Mixed HL
What is the diagnostic for this audiogram?
Right Reverse Cookie bite Mixed HL
- Moderate to Mild to Moderately severe
What is the diagnostic for this audiogram?
Right Mild to Profound Sloping SNHL
Left Moderate to Profound Sloping SNHL
What is the diagnostic for this audiogram?
Right: Normal to 1k drops precipitously from mild to moderate at high frequencies SNHL
Left: Mild Sloping to Moderate Mixed loss
What is the diagnostic for this audiogram?
vt = vibro tactile (can feel the vibrations)
No measurable hearing
What is the diagnostic for this audiogram?
Right: Cookie Bite Severe to Mild to Moderately severe SNHL
Left: Normal to 1k Precipitously dropping to Profound SNHL
What is the diagnostic for this audiogram?
Right Moderate 3k notch SNHL
Left: Moderately severe 4k notch SNHL
What is the diagnostic for this audiogram?
Right: Normal precipitously dropping at 1k SNHL
Why is it easier for testing one side in Optometry than Audiology?
What is Cross-Over?
When presenting sound to one ear, the earphone also vibrates the head a bit, this will stimulate BOTH cochleae by bone conduction (cross-over)
(use insert earphones to reduce this)
What is Interaural Attenuation?
- ‘Cross-over’ refers to sound energy that is crossing over via bone conduction
- The difference between the level presented and the level crossing over is called interaural attenuation
*Interaural attenuation is sound level minus the level getting to the other ear (generally through the bone, i.e., inefficiently)
What is an issue related to cross over from TDH headphones?
For TDH headphones, the skull may vibrate at a level that is only 40 dB less then the presentation level (i.e., the presentation level minus 40 dB may get to the other cochlea)
This drop in energy is called interaural attenuation
What is Cross-Hearing?
When the cross-over is loud enough that it is HEARD in the opposite cochlea -> cross hearing
There is always some cross-over, but it is usually too soft to be heard, because the sound is louder in the stimulated ear (due to the direct, more efficient route) (Interaural Attenuation)
When would this not be the case that cross-over isn’t too soft so you have cross-hearing? (Less effect of Interaural attenuation)
Using Bone Conductor
Threshold in the non test-ear is different than the test ear
When could cross-hearing occur?
Whenever the input to the TE is greater than the cochlear threshold in the NTE + IA, cross-hearing occurs, enough sound to ‘leak over’ and be heard
AC Input (TE) – IA < BC Threshold (NTE) … okay
AC Input (TE) – IA >= BC Threshold (NTE) … not okay
What does IA depend on? (3)
Head/Ear
Transducer Type
Varies as a function of Frequency
How much sounds leaks over in Cross-Hearing?
- Presentation level minus INTERAURAL ATTENUATION (IA)
- i.e., presentation level minus IA = cross over (and if this is heard on the non-test side, it is cross-hearing)
How much sounds leaks over in Cross-Hearing?
- Presentation level minus INTERAURAL ATTENUATION (IA)
- i.e., presentation level minus IA = cross over (and if this is heard on the non-test side, it is cross-hearing)
How do we know the IA depending on factors?
Assume minimum IA to be safe depending on the frequency and the transducer
For this class across frequencies:
40 dB for TDH (supra-aural)phones, 50 dB for ER-3 (insert) phones
If the presentation sound in the TE using TDH (supra-aural) phones is 65 dB:
Fill in the blanks and explain your answer.
Assume the worst 40 dB because of TDH (supra-aural) phones
If the presentation sound in the TE using TDH (supra-aural) phones is 80 dB:
Is it possible that on the NTE it could be cross-hearing if the threshold is 50 dB no conductive loss.
No, we assume 40 dB of skull attenuation with TDH phones, so 80 -40 dB only 40 dB reaches the NTE and it’s lower than the 50 dB threshold. So only Cross-Over
If the presentation sound in the TE using TDH (supra-aural) phones is 40 dB with 40 dB Conductive loss in the TE:
Fill in the blanks and which ear is hearing better
We don’t know which ear is hearing it because 0 reaching both cochlea because of 40 conductive loss and 40 dB attenuation
What is the hearing threshold in the left ear?
Trick question because of cross-hearing so you need to do masking
What is the threshold in the left ear?
Trick question because we know the left ear hears bad or not at all , we presented a sound that was of high intensity, and since we know that the right ear is better after AT of 40 dB, it results than cross-hearing so you need to do masking to take away the RE contribution
If the presentation sound in the TE using TDH (supra-aural) phones is 50 dB would there be Cross-hearing if we mask the NTE using a noise of 30 dB?
No, because on the NTE it wouldn’t reach the threshold adding the masker
Why do we use masking only with AC transducer and not BC transducer?
Because if we would use BC transducer the vibrations would cross-over and mask on both sides
What is Effective Masking Level?
The amount of masking required to bring a threshold to ‘x’!!
Calibrated in terms of the level to which your threshold would be raised (if the masker was in the same ear as the tone)
If the threshold of a patient is 20 dB HL and I apply a masker of 50 dB (in the same ear): What would happen?
It would shift the threshold to 50 dB HL
50 dB of masking (i.e., 50 dB Effective Masking Level) means the softest sound you can hear is ____ dB HL
50 dB HL
If your threshold is 60 dB HL, and you have 70 dB EML of masking (in the same ear), your masked threshold will be _______ dB HL and why?
70 dB HL because EML shifts threshold in this ear at this level
If your threshold is 60 dB HL, and you have 50 dB EML of masking (in the same ear), your masked threshold will be ____ dB HL and why?
Stay at 60 dB HL because the masker isn’t loud enough to shift your threshold
What are the steps for biological Calibration (when masking is not calibrated)? (5)
- Test threshold at frequency x
- Put masking noise in same ear
- Raise masker until threshold is shifted
- Repeat (raise masker and retest threshold)
- Dial difference is correction factor
What is Overmasking? Use the image to explain the concept.
Masker is too loud in NTE and exceeds IA, so is heard in TE (Shifts threshold too) In the example, we could use inserts instead to help increase IA to 50 dB.
What is Undermasking?
The masker isn’t loud enough so there is cross hearing
What is Undermasking?
The masker isn’t loud enough so there is cross hearing
What is a rule of thumb related to masking using TDH or for ER3
You should mask when the level difference between ears exceeds 40 dB for TDH, or 50 dB for ER3
What would be the steps to see if masking is required?
- Good ear air
- Poor ear air
- Bone
- if there is a at least 10 dB gap between bone and air then probably cross-hearing so you must mask
What do these two BC possibilities entail?
Masked BC helped find either possibilities
Maybe I find out (left) that the BC masked and AC overlap so it’s a sign of SNHL or maybe I find out (right) BC masked and AC gap so CHL which is why doing masked BC is important.
When should we mask and when is there no need?
No need if there is no ABG in both ears, but if there is an air-bone gap greater than 10 dB, use masking (i.e., mask NTE)
Should we mask in this case?
Yes there is asymmetry because when you’ll do BC on the right ear there will surely be an ABG because left ear is better so cross-hearing for sure so you’’ do bone and then mask bone.
Give a masking dilemma:
When just enough masking to prevent undermasking is already overmasking
By the time you introduce enough masking to prevent cross-hearing, the masker is intense enough in the test ear to artificially raise the threshold
