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Diagnostics > Masking > Flashcards

Masking Flashcards

1
Q

What is clinical masking?

A

A method of keeping the non-test ear busy in order to determine the true threshold of the test ear

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2
Q

What is the goal of clinical masking?

A

Eliminate cross hearing; make the test signal inaudible in the NTE without affecting the true response of the TE

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3
Q

When do you mask for air conduction?

A

Difference between the AC of test ear and the best bone of the non-test ear is greater than or equal to IA

AC of TE - best bone of NTE >= IA*
or
AC of TE - AC of NTE >= IA

*(40, headphones or 60, inserts)

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4
Q

When do you mask for bone conduction?

A

AC of TE - Unmasked BC = ABG
ABG >= 15 dB

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5
Q

When do you mask for SRT?

A

PTA - best bone of NTE >= IA

or

ST of TE - ST of NTE >= IA

*use PTA to estimate SRT

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6
Q

When do you mask for WRS?

A

Unmasked SRT of test ear - best bone of NTE at (.5, 1, 2, 4k Hz) > IA (40 dB)

–

Pres Level of TE > BC PTA of NTE
Pres Level of TE > BC SRT of NTE
Pres Level of TE > AC SRT - ABG of NTE

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7
Q

What is the difference between masking FOR and masking in?

A

Mask FOR the test ear
Mask IN the non-test ear

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8
Q

What is the overmasking?

A

when the masking level is crossheard in the test ear

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9
Q

What is undermasking?

A

When the tone is crossheard in the non-test ear

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10
Q

What is effective masking?

A

Masking level in the non-test ear that is not crossheard in the test ear and the tone is not crossheard in the non-test ear

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11
Q

What is the masking dilemma?

A

Unable to plateau due to bilateral active conductive component. Stimulus increases with masking noise level and true thresholds are not obtained at limits of the equipment

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12
Q

Describe the Max Safe Masking Level

A

Highest intensity that does not overmask presented in the NTE

IA + BC of TE - 5 dB

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13
Q

Describe the Min Safe Masking Level - M(min)

A

Level that provides at least some masking of the test signal in the NTE; could still be undermasking

AC of NTE + MEMC + 10 dB + OE
or
Pres Level of TE - IA + ABG of TE (+5)

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14
Q

How do you find the effective masking level?

A

Plateau method

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15
Q

What is the shadow curve?

A

Occurs during unilateral asymmetric hearing loss. The unmasked AC thresholds are crossheard from the better ear and mimic its configuration.

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16
Q

What is interaural attenuation?

A

Amount of energy that is absorbed or lost in the skull

17
Q

Describe the plateau method

A

Present the stimulus at the same level as AC and masking noise at 10 dB above the best bone of the NTE. If tone is not heard, increase tone by 5 dB. If tone is heard, increase masking noise by 10 dB. After increasing the masking noise three consecutive times while the stimulus tone stays the same, true threshold is determined.

18
Q

What is SAL?

A

Not used routinely
-
Each AC thresholds are tested twice. First threshold is in quiet and second threshold with masking noise at max level from bone vibrator at the forehead. Noise is transmitted via bone conduction to cochlea to mask AC test tone.

SAL test measures size of threshold shift (small ABG) and compare to norms.

Must know max BC level to get SAL Norm at each frequency

19
Q

When considering the use of masking technique is needed, one must consider the difference between the _______________ in the ____________ ear and the ______________ in the _____________ ear

A

Air conduction, test ear
Bone conduction, non-test ear

20
Q

In a person with SSD, failure to utilize _____________ during air conduction will result in ________________

A

Clinical masking
Shadow curve

21
Q

The __________________ is achieved when the test signal is not heard in the _______ ear and the masking noise is not heard in the _____________

A

Effective masking
Non-test ear
Test ear

22
Q

Effective masking can be achieved when the _________________________ in the non-test ear is close to or greater to ______________________ of the transducer, in which case ________________________ is said to occur

A

Min masking level
Interaural attenuation
Masking dilemma

23
Q

When does the masking dilemma typically occur?

A

Bilaterally active conductive component

24
Q

Use of insert earphones may help against the masking dilemma as would the ________________ method.

A

Plateau

25
Q

What is central masking?

A

Phenomenon where simply the presence of noise raises the auditory threshold as much as 5-10 dB in some individuals

26
Q

Right ear = 0 dB thresholds, all freq.
Left ear = 1000 Hz, 55 dB

What level should the masking noise be presented?

What level should the tone be presented?

A

Masking noise = 10 dBEM (10 dB above NTE AC)

Tone = 55 dB EM (same presentation level)

27
Q

Explain criteria of plateau method to determine true threshold

A
  1. Present stimulus at 55 dB.
  2. If sound is not heard, present at 60 dB. Increase by 5 dB increments until sound is heard.
  3. If sound is heard, increase masking noise by 10 dB. If sound is heard, increase masking noise by 10 dB. If sound is heard, increase masking noise by 10 dB.
  4. After the third consecutive increase of masking noise with the stimulus staying at the same level, I’ve reached true threshold
  5. If masking level exceeds the IA of the transducer and I still cannot reach a plateau, there is a possibility of cross-hearing.
  6. True threshold cannot be determined due to masking dilemma.
28
Q

T/F: With the masking dilemma, the IA is greater than the ABG

A

True

29
Q

In puretone audiometry, when should you mask?

A

Whenever it is suspected that the nontest ear is participating or is responsive during the evaluation of the test ear

30
Q

How do you calculate interaural attenuation (IA)?

A

Unmasked AC (TE) - Unmasked AC (NTE) = IA

31
Q

What makes a masking stimulus an efficient masker?

A

Noise that produces a given effective level of masking with the least overall sound pressure level

Example: narrowband, speech spectrum, white noise

32
Q

What is initial masking?

A

Initial masking level (dB EM) = air conduction threshold (dB HL) of NTE

Initial masking level = AC of NTE + 10 dB

33
Q

What are two solutions to the masking dilemma?

A
  1. Use insert earphones
  2. Perform SAL test

Diagnostics (17 decks)

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