3700 Exam 2: Weeks 7-8

Front 1

When do we have to retest the patient via air conduction and find a threshold in either ear while we are masking the non-test ear?

Back 1

If the AC threshold of the TE is 40 dB greater than the BC of the NTE, then we need to mask the NTE and retest the TE.

Front 2

Do we need to retest bone conduction in either ear or both ears while we are masking the non-test ear?

Back 2

If there is a 10 dB or greater ABG in the TE ? If yes, then mask the NTE and retest the BC in the TE.

Front 3

Steps in Masking Procedure:

Back 3

1. Explain to the patient exactly what is going to happen and how they are to respond. (If not properly counseled, the patient will respond to the masking
noise rather than the stimulus)

2. The patient should be told that they will hear some noise similar to static in one ear, but that they should respond only when they hear the tone in addition to the noise.

3. Let the patient know to respond whenever they hear the tone, no matter which
ear they hear it in.

Front 4

Types of Masking Noise

Back 4

White Noise and Narrow Band Noise

Front 5

White noise: AKA broadband or wideband noise

Back 5

• All of the frequencies from 125-8000 Hz to cover the testing spectrum
• Not a good choice both inefficient and unnecessarily loud

Front 6

Narrow Band Noise or NBN:

Back 6

filtered White Noise, so you have bands of noise that surround a particular frequency.
• NBN consists of a narrow range of frequencies of equal intensity. • If we are then testing with a pure tone stimulus of 2000 Hz & we want to mask
the NTE then we would need to change the corresponding NBN with a central frequency of 2000 Hz. So each time we change the frequency we need to change the NBN so it is the same. This is done automatically on a diagnostic audiometer.
• Narrow Band Noise is more effective and easily tolerated than white noise for pure tones.

Front 7

appropriate masking depends..

Back 7

The appropriate type of masking depends of the signal being masked. If the signal has a wide spectrum (Speech or Clicks) then the masking noise must also have a wide spectrum.

Front 8

Effective Masking (EM)

Back 8

Effective Masking (EM) eliminates crossover from occurring. EM determines how much noise is appropriate to ‘cover up’ or ‘keep busy’ the better ear or NTE from taking part in the test.

Front 9

Undermasking

Back 9

Undermasking occurs when the masking noise presented to the better or NTE is not loud enough to eliminate crossover or Interaural Attenuation.
• An increase in the masking noise causes the false threshold to shift from the NTE, and drop to the true threshold of the TE.
• Undermasking occurs more commonly in air conduction testing.

Front 10

Overmasking

Back 10

Overmasking is the condition when the noise presented to the NTE is intense enough to cross over to the TE and mask it.
• You will know that this is occurring when each 10 dB increase in masking shifts the hearing threshold 10 dB or more above the plateau.
• Overmasking occurs more commonly in bone conduction testing.

Front 11

Hood-1960

Back 11

Plateau Method of Masking - Hood described this method in 1960

Front 12

Describe Plateau Method of Masking

Back 12

The non-test ear is masked by progressively greater amounts of sound until the threshold of the test ear does not continue to increase. The plateau is a range of masking levels in which there is no increase in threshold of the TE. Most audiologists use 3 consecutive masked levels (5 or 10 dB steps) with the same response to be a threshold.

Front 13

UNDERMASKING as part of plateau method

Back 13

UNDERMASKING: When a tone is really being heard by the NTE via cross hearing, then raising the level of the masking noise will cause the masked threshold to increase.
• This occurs because the noise and tone are both in the same NTE.

Front 14

PLATEAU

Back 14

• When the tone is really being heard in the TE, then raising the masking noise level will not cause the threshold to change.
• Plateau reveals the true masked thresholds for the TE
• Once the noise is effectively masking the non-test ear, you can add more noise
without affecting the threshold because the amount of noise covering the NTE has nothing to do with the TE. However, this has limits.

Front 15

OVERMASKING: If the level of the noise presented to the NTE becomes ___ _____, then it can _______ and mask the TE. Once this occurs then the threshold in the ______ will start to rise again as the _______ level is increased.

Back 15

Too loud, cross over
Test ear, masking

Front 16

UNDERMASKING: When a tone is really being heard by the _____ via ______ hearing, then raising the level of the masking noise will cause the masked threshold to increase.
This occurs because the _____and_____are both in the same NTE.

Back 16

NTE, cross hearing,
noise and tone

Front 17

In the plateau, what is happening? why?

Back 17

Threshold stays at
65 dB, despite the masking noise level being raised from 40 to 60 dB HL. This is because when the tone is really being heard in the TE, then raising the masking noise
level will not cause the threshold to change. Plateau reveals the true masked thresholds for the TE Once the noise is effectively masking the non-test ear, you can add more noise
without affecting the threshold because the amount of noise covering the NTE has nothing to do with the TE.

Front 18

In the Undermasking what is happening?

Back 18

noise and tone are both in the same NTE. n the graph it shows that raising the masking noise from 20-40 dB HL caused
the apparent TE threshold to rise from 45 to 65 dB HL.

Front 19

In the Overmasking what is happening?

Back 19

If the level of the noise presented to the NTE becomes too loud, then it can cross
over and mask the TE. Once this occurs then the threshold in the TE will start to rise again as the
masking level is increased.

Front 20

PROPERLY USED MASKING PROCEDURE: AIR CONDUCTION

Back 20

1. Obtain and record the AC threshold of the TE unmasked.
2. Then compare the AC threshold of the TE with AC and BC thresholds of NTE to determine if masking is needed.
3. If masking is needed, next you need to select the initial amount of masking (IM) using Narrow band noise on the audiometer for the NTE.
4. Reestablish threshold in the TE with this initial amount of masking in the NTE.
5. Each time the patient responds to the PT signal presented to the TE, increase masking noise in the NTE by 10 dB.
6. Each time the patient does not respond to the PT signal in the TE, increase the tone in the TE in 5 dB steps until the patient responds again.
7. This procedure is continued until the masking noise can be increased over a 30 dB interval (3 consecutive 10 dB steps) without producing a shift in the threshold level of the TE.
8. Now you have reached the “Plateau” and the AC pure tone intensity level you reached is the actual threshold of the TE.

Front 21

Rules for masking state that masking is required in the
better ear when the difference between ___ thresholds of the TE and the ____ thresholds of the NTE is ___ dB or more if using supra-aural headphones and ___ dB or more if using insert earphones.

Back 21

AC, BC, 40 dB , 70 dB

Front 22

To determine the initial amount of masking, most audiologists use this formula:

Back 22

IM = AC NTE + 10 dB EML

Front 23

Each time the patient responds to the Pure Tone signal presented to the TE, increase _______ noise in the NTE by ___ dB. Each time the patient does not respond to the PT signal in the TE, increase the _____in the TE in __ dB steps until the patient responds again.

Back 23

Masking 10 dB.
tone, 5 dB

Front 24

Continue to fool with the masking until (up 10, up 5) until masking noise can be increased over a ____ dB interval or __ _________ _____, with out producing a shift in the threshold level of the TE.

Back 24

30 dB interval (3 consecutive 10 dB steps)

Front 25

Similarity and difference of BC conduction masking procedure to AC masking

Back 25

Similar to AC Masking procedure except Placement of headphones and Bone Oscillator is very important due to occlusion effect potential impact on BC thresholds

Front 26

Describe occlusion effect and BC

Back 26

because the earphone is placed over the NTE, then the occlusion effect, which we talked about earlier, may be created in that ear. The occlusion effect may cause BC thresholds to shift once headphones are placed on the head.

Front 27

stimulus delivered via BC can crossover with ___dB difference between ears.

Back 27

0

Front 28

BC Masking Procedure

Back 28

1. obtain and record the BC threshold of the TE unmasked and unoccluded.
2. compare the AC thresholds with the BC thresholds.
If there is a difference of 10 dB or more between the AC and BC results, then masking is required.
3. Select the initial amount of masking (IM) for the NTE using NBN.
4. Then you must reestablish threshold in the TE with this initial amount of masking in the NTE.
5. Each time the patient responds to the PT signal presented to the TE, increase masking noise in the NTE by 10 dB.
6. Each time the patient does not respond to the PT signal in the TE, increase the tone in the TE in 5 dB steps until the patient responds again.
7. Continue this procedure until the masking noise can be increased over a 30 dB interval (3 consecutive 10 dB steps) without producing a shift in the threshold level of the TE.
8. This is the “Plateau” and the BC pure tone intensity level you reached is the actual threshold of the TE.
9. Replace unmasked thresholds symbols on the audiogram with the masked threshold symbols:

Front 29

Formula to select initial masking for BC

Back 29

IM = AC NTE+ 10 dB EML (effective masking level) + the amount needed to overcome the OE (occlusion effect).

In low frequencies, additional masking should be added to the starting levels at low frequencies. 15 dB should be added to 250 Hz and 500 Hz and 10 dB should be added at 1000 Hz.

Front 30

What is this symbol?

Back 30

Right Ear UNmasked Air Conduction (Red, Right, Round)

Front 31

What is this symbol

Back 31

Right Ear Masked Air Conduction

Front 32

What is this symbol

Back 32

Right ear bone conduction unmasked

Front 33

What is this symbol?

Back 33

Right ear masked Bone Conduction

Front 34

what is this symbol

Back 34

left ear UNmasked Bone Conduction

Front 35

What symbol is this?

Back 35

Left Ear Masked Bone Conduction

Front 36

What symbol is this?

Back 36

Left Ear Masked Air Conduction

Front 37

What Symbols Is This ?

Back 37

Left ear unmasked air conduction

Front 38

Interpret this Audiogram-Is masking Required?
-Unmasked audiogram tested using supra-aural headphones-

Back 38

Normal AC and BC thresholds in the LEFT ear. Moderate AC thresholds and normal BC thresholds may mean CONDUCTIVE HEARING LOSS If the AC threshold is 40 dB or greater than the BC of the NTE, then we need to mask – close, but no need to mask for AC. The AC stimulus did not cross over from the right ear to be heard by the left ear. However, the other rule for BC is that masking is needed if there is a 10 dB or greater ABG in the TE (right ear). In this case the answer is yes. So we need to mask the NTE (Left) and retest the BC in the TE (Right) and we’ll see what happens.

Front 39

Interpret this audiogram-Patient 1
Masked and retested the BC in the right ear.

Back 39

It is in fact a conductive hearing loss. The BC thresholds remained at 0-5 dB. Jenny has a normal inner ear in both the left & right ear. She has something happening in her outer or middle ear that is causing the conductive hearing loss in her right ear.

Front 40

Interpret this audiogram

Back 40

Bilateral moderate SNHL unmasked. Is there a 40 dB difference between the AC in the left ear & BC in the right ear? No. Is there a 40 dB difference between the AC in the right ear & BC in the left ear? No, so AC does not need to be masked. Is there a 10 dB or greater ABG in the right ear? No. Is there a 10 dB or greater ABG in the left ear? No, so we do not need to retest BC with masking. This audiogram is complete. It truly is a symmetrical bilateral SNHL.

Front 41

Interpret this audiogram

Back 41

Appears that he has a normal to mild SNHL in the right ear & a mild to moderate mixed HL in the left ear. This is your classic mixed HL. He has some SNHL & some conductive HL. Where is the conductive portion of the HL? It is the area between the BC and AC symbols. The area above the BC symbols is the SN portion of the HL. So, do we need to mask this patient? Look at the right ear. Is there a 40 dB difference between AC in the right ear and BC in the left ear? No, so AC is fine. Is there a 10 dB or greater ABG between the AC & BC results? No, so the right ear does not need to be masked. So, now let’s
make the left ear the TE. Are the AC thresholds in the left ear 40 dB or greater than BC in the right ear. At 500 Hz the AC thresholds of the left ear is 55 and the BC threshold of the right ear is 20. The difference is 35 dB, so we don’t need to mask. However, when you look at all of the frequencies, you should determine that we do need to mask for AC in the left ear. There is a 45 dB difference between the left ear AC thresholds and the right ear BC thresholds at 2000 Hz. At 4000 Hz there is a 40 dB difference. So, we will need to mask for AC.
What about BC? Is there a 10 dB or greater ABG? Yes, so we will need to retest BC in the left ear while masking the right ear.

Front 42

Interpret audiogram

Back 42

After AC and BC masking have been completed. Because masking was needed for 2000 and 4000 Hz and the other frequencies were right on the edge, we decided to mask them all. When masking was placed in the right ear, the AC thresholds in the left ear dropped slightly. When BC was retested using masking, the BC symbols fall down very close to the AC. Note the symbols at 250 & 4000 Hz have the arrow coming out of
the symbol. This means that we reached the limits of the audiometer and he did not respond. So his threshold must have been worse than that. So after masking, Rick Lambert, has a normal to mild SNHL in the right ear and a moderate to severe SNHL in the left ear. Go back & compare the before and after masking audiograms on these patients so that you understand what a difference masking can make. Without masking, Rick would have been diagnosed with a mild to moderate mixed hearing loss instead of the actual moderate to severe SHNL that he has.

Front 43

Interpret audiogram

Back 43

After AC and BC masking have been completed. Because masking was needed for 2000 and 4000 Hz and the other frequencies were right on the edge, we decided to mask them all. When masking was placed in the right ear, the AC thresholds in the left ear dropped slightly. When BC was retested using masking, the BC symbols fall down very close to the AC. Note the symbols at 250 & 4000 Hz have the arrow coming out of
the symbol. This means that we reached the limits of the audiometer and he did not respond. So his threshold must have been worse than that. So after masking, Rick Lambert, has a normal to mild SNHL in the right ear and a moderate to severe SNHL in the left ear. Go back & compare the before and after masking audiograms on these patients so that you understand what a difference masking can make. Without masking, Rick would have been diagnosed with a mild to moderate mixed hearing loss instead of the actual moderate to severe SHNL that he has.

Front 44

Rule to remember- when it doubt, _____

Back 44

mask

Front 45

Explain Central Masking

Back 45

• It has been shown that a small shift is seen in the threshold of a pure tone when
a masking noise is introduced into the opposite ear. This increased shift
averages about 5 dB. • What that means is if you test an ear and get a threshold and then introduce
masking into the opposite ear, you'll note the threshold in the opposite ear has
increased or worsened by 5 dB. • It is believed that the elevation of threshold is produced by inhibition that is sent
down from the auditory centers in the brain and has, therefore, been called central masking.

Front 46

In BC Testing, cross hearing can be expected when:

Back 46

ABG (TE) > 10 dB

Front 47

In bone conduction testing, there's no....

Back 47

interaural attenuation.

Front 48

We have bone conduction scores in the right ear at 0-5 dB and the air
conduction thresholds in the right are at 35-40 dB. We have...

Back 48

an air bone gap.

Front 49

WHEN BC and AC thresholds are within 10 dB of each other, we have ______ loss

Back 49

SENSORINEURAL Loss (if inner ear is poor, then both AC and BC are poor).

Front 50

when you have an ABG in the TE > 10 dB, suspect ___ ______

Back 50

cross hearing

Front 51

ABG <=10 dB are .....

Back 51

not considered significant

Front 52

In AC testing, cross hearing can be expected when...

Back 52

AC (te) - IA > or = BC (nte)

Front 53

Formula that determines whether or not masking is needed for air conduction:

Back 53

It is that the danger of cross hearing for air conduction tone presents itself whenever the level of the tone in the test ear (TE) by air conduction, minus the IA, is equal to or higher than the BC threshold of the non-test ear (NTE).
AC(TE) – IA >= BC (NTE)
Where IA = 40 if using Supra Aural OR IA = 70 if using Inserts

Front 54

IA for BC has been established at ___dB because there isn’t any way of knowing which cochlea has been stimulated by a BC tone, cross hearing during BC tests is____ __ ______

Back 54

0, always a possibility

Front 55

Interaural Attenuation for pure tone conduction testing would be ___ dB HL

Back 55

40

Front 56

Many audiologists prefer to use insert earphones because:

Back 56

Since Insert earphones provide more IA than supra aural headphones, if the
clinician is using inserts, then: IA = 70 dB
This means that masking will be required much less frequently when using insert phones.

Front 57

If we're testing by air conduction, what will the interaural attenuation be?

Back 57

The patient’s Right AC threshold at 1000 Hz is 10dB HL. Even though
their left ear is completely deaf, they also responded to a 1000 Hz tone presented from the left earphone at 60 dB HL. This means that the 60 dB tone presented to the left ear must have reached a level of 10 dB HL in the right ear.
• This means that the IA at 1000 Hz for this patient must be 50dB (60dB- 10dB=50dB). Similarly, the amount of IA at 4000 Hz in this case is 55 dB.
• This is not the case in all patients.

Hint 57

If we're testing via bone conduction, what will the interaural attenuation be? ANSWER: No IA for BC

Front 58

What is cross over or shadow hearing?

Back 58

Cross Hearing - common to find that the sound being presented to one ear is actually being heard by the other ear, AKA shadow hearing. OR The reception of a sound signal during a hearing test or at the ear opposite the ear being tested. Cross over occurs when you present a sound to the TE, but the NTE hears the sound first. If clinician is unaware of this, could result in erroneous results

Front 59

what is cross over level

Back 59

Crossover level, or interaural attenuation, Interaural attenuation (IA) refers to the loss of the acoustic energy of a sound as it travels from the TE, across the head, to the NTE. It differs at each frequency, and varies slightly from patient to patient.

Front 60

what is a shadow curve or mirror audiogram.

Back 60

When the thresholds obtained are not the true thresholds. The point where the crossover occurs is being recorded instead.

Front 61

Explain the cross over effect in this picture

Back 61

As we're finding thresholds and working our way up to the limits what's probably going to happen is at around 50-60 dB in the left ear, the sound will cross the barrier of the head and be perceived by the right ear. If we don't understand cross hearing we assume the stimulus of 50 dB is correct rather than no response.

Front 62

Book definition of masking

Back 62

Book Definition: the process by which the threshold of a sound is elevated by the simultaneous introduction of another sound.

Front 63

Dr J definition of masking

Back 63

1. Masking occurs when an unwanted sound causes a wanted sound to be inaudible. 2. Masking is required to keep a better ear busy while testing a poorer ear. The poorer ear receives the tone while the better ear hears a controlled masking noise. TV(signal) and dishwasher (masker) example.

Front 64

Define Test Ear vs Non Test Ear

Back 64

Test Ear (TE) = ear currently being tested the test ear Non Test Ear (NTE) = ear one not being tested, opposite of TE