Audiology exam 2 - chapter 5

What is TE

Test ear- the ear intended to be teated during a hearing exam 

What is NTE

non test ear- it recieves masking noise to prevent interference 

False Response - What circumstances may cause a false negative responses in test ear

• malingering 

• tinnitus 

• poor headphone placement for air conduction 

• poor oscillator placement for bone conduction 

• lack of experience with hearing test or stimuli 

False responses - What circumstances may cause false positive responses in Test Ear 

Guessing 

Tinnitus 

Cueing from audiologist 

Tactile responses 

Cross hearing 

What is the purpose of masking the Non-Test Ear (NTE)?

To keep the NTE “busy” so it doesnt respond to sounds meant for the Test Ear

What is cross hearing?

When the sound meant for one ear (TE) is heard by the other ear (NTE) causing false responses/positives 

How can cross hearing occur ?

through air conduction (AC) or Bone Conduction (BC)

Why is bone conduction a common cause of cross hearing ?

Because sound vibrations can travel through the skull to the better hearing ear (NTE)

What happens if a tone is louder than the NTE’s bone conduction threshold?

The NTE might hear it first and respond, giving a false positive during the TE test 

How can cross hearing occur in air conduction?

sound leaks through headphones/inserts

how can cross hearing occur in bone conduction?

sound vibrations travel through the skull to the other ear

What is interaural attenuation?

The reduction in sound intensity as it travels from one ear to the other

What is the typical IA for air conduction with standard headphones?

40 dBHL

What is the typical IA value for air conduction with insert earphones (martin)

60dBHL

What is the IA value fro insert headphones

60 dBHL

What factors can cause interaural attenuation (IA) to vary ?

• Frequency of sound

• Individual differences

• Type of transducer used (headphones or inserts)

is interaural attenuation heard by the test ear or the non test ear?

non- test ear 
- it is the sound that gets lost in transmission when traveling from the test ear to the non test ear

When is cross hearing likely to occur in air conduction ?

When the level of tone presented in the test ear minus the interaural attenuation is equal to or higher than the bone conduction threshold of the non-test ear 

formula for dangers of cross hearing in air conduction

AC te - IA greater than or equal to BC nte 
(air conduction of test ear minus IA is greater than or equal to the bone conduction of NTE)

Why/when do you need to mask ?

When you want to get a true threshold

How do you mask?

put sound in the non test ear in order to keep it busy

How will masking effect TE responses ?

make them poorer with masking because the client no longer has the help of the non test ear 

How will masking effect thresholds

it will never improve them

if masking will change the diagnosis do you need to mask?

Yes

In what types of hearing will masking change the diagnosis

• Conductive 

• Mixed (conductive and sensorineural in both ears)

• Asymmetrical (one ear has better hearing than the other 

if masking will not change the diagnosis do you need to mask?

no

in what types of hearing will masking not change the diagnosis

• Sensorinerual/Symmetrical ( both ears have the same hearing loss)

• Normal hearing ( the client has no hearing loss)

Do most audiologist mask even when it might be unnecessary

Yes, it is better to mask than to not mask

What is a shadow curve ?

It looks like the worse ear is hearing better than it really is - but it is actually the better ear picking up the sound 

Why is a shadow curve bad

• No masking us being used

• cross hearing is happening (so the better NTE is given the bad test ear good results)

• Results are misleading

What does a shadow curve show?

A shadow curve shows a FALSE hearing loss

What happens when masking is applied during a shadow curve situation ?

The true threshold is revealed, often showing a more severe sensorineural loss in the test ear 

What is the formula to determine if masking is needed for air conduction with headphones ?

AC (Test Ear) – 40 dB > (or equal to)BC (Non-Test Ear)

What is the formula for masking with insert earphones ?

AC (Test Ear) – 60 dB > (or equal to)BC (Non-Test Ear)

What type of noise is used for AC pure tone masking?

White noise or broadband (Gaussian) noise

Why is White/broadband nosie used for masking ?

It evenly covers a wide range of frequencies,

narrowband noise

noise of frequencies that are surrounding the test stimuli

narrowband noise - headphones

can deliver masking noise

Narrowband noise - inserts

can deliver masking noise

What does narrowband noise do ?

• decrease occlusion effect in bone conduction testing when ear is covered

• causes Larger IA when tip is deeply inserted into ear canal

∆

• TE is right ear 

• NTE is left ear

• the right ear air conduction threshold has been obtained with masking delivered to the left ear 

• =Right masked air conduction

☐

• TE is left ear 

• NTE is right ear

• The left ear air conduction threshold has been obtained with masking delivered to the right ear 

• Left masked air conduction

What is Air- Bone Gap (AGB) ?

AC threshold - BC threshold in the same ear

When do you need to mask in Bone Conduction?

When the ABG in the test ear is greater than 10
AGB in TE > 10

Why do you need to mask in bone conduction testing ?

You might get a response, but it could be from the wrong ear (NTE)
Masking helps find the true threshold in the Test Ear

What type of noise is ideal for BC masking in pure tone audiometry ?

Narrowband noise - focused around the test frequency

What is white/broadband noise, and why is it not ideal for pure tone masking ?

Its noise with equal energy across all frequencies; not ideal becasue it can mask more than the tone being tested 

What is the occulsion effect ?

When covering the ear during BC testing makes low-frequency sounds seem louder than they really are

How can the occlusion effect be reduced during BC testing?

Use insert earphones and insert them deeply into the ear canal

What is one advantage of insert earphones in BC masking ?

They reduce the occlusion effect and increase interaural attenuation for more accurate results 

[ 

• Right masked bone conduction

• TE is right ear (via bone conduction) 

• NTE is left ear (via air conduction )

• the right ear bone conduction threshold has been obtained with masking delivered to the left ear via air conduction 

]

• Left ear masked bone conduction

• TE is left ear (via bone conduction)

• NTE is right ear (via air conduction)

• The left ear bone conduction threshold has been obtained with masking delivered to the right ear via air condcution

How to know when to mask?

• Is it needed

• how much masking noise is required

• When is a masking noise too much (confound test results)

What is the shotgun approach?

Just throw masking noise into the NTE

What is the risks of the Shotgun Approach?

Might use too little masking - allowing non test ear to respond

Might use too much masking - leading to overmasking 

In the minumum-noise method, which ear’s threshold is used to determine masking need ?

The threshold of the non-test ear(NTE)?

What does it mean if maskign the NTE doesnt change the TE threshold ?

The TE threshold is valid (true response from the test ear)

What does it mean if masking the NTE results in no response from TE?

The NTE was contributing; original TE threshold was not valid

What is Initial masking (IM) in diagnostic testing ?

The minimum effective amount of masking noise = AC threshold of NTE

formula for initial masking (IM)

IM = Air conduction threshold of non test ear

What is minimum masking?

Same as Initial masking (IM) starting point for effective masking 

What is Maximum masking (Mmax)

The highest masking level before overmasking occurs 

Formula of maximum masking

Mmax= BC TE + IA - 5

Why is there a limit of how much masking can be used ?

Too much masking in the NTE can cross back to the TE and interfere

What is it called when the masking of the NTE is too much and interferes with the TE

overmasking

What is effective masking ?

The range from initial masking to maximum masking - enough to mask NTE without overmasking 

What is central masking ?

A small threshold increase (5 db) when masking is introduced into the opposite ear due to neural inhibition form the auditory brain centers 

What is a masking dilemma?

A situation where overmasking is a real risk because it is hard to find a safe masking level 

What type of hearing loss is most common for a masking dilemma 

Bilateral conductive hearing losses 

What is overmasking?

When masking noise in the NTE is so loud is crosses over to the TE and interferes with TE hearing 

What formula indicates overmasking is occuring?

Effective masking NTE > BC TE + IA

What is the Plateau method in masking?

A systematic approach to determine the true threshold of the test ear while ensuring the non-test ear (NTE) is effectively masked, without causing overmasking 

What is the first step in the plateau method?

Begin with intial masking (IM) level in the NTE- which is the air conduction threshold of the NTE 

What does it mean if the tone is not heard after initial masking is applied ?

It indicates the non-test ear (NTE) was responding originally. The test ear did not detect the tone, so the TE threshold needs to be re established using masking 

How is the test ear threshold re established after confirming NTE was responding 

• Keep masking in the NTE

• Increase the tone level in the TE until patient responds again 

• This helps find the true threshold of the test ear 

Once the patient responds to the tone again, how is the masking confirmed to be effective 

• increase masking noise in the NTE in 5 db steps 

• Keep the TE tone at the same level 

• Do this for three consecutive 5 db increases where the response remains the same

What does the maintainign the same TE threshold across 3×5 db increases in masking indicate

That you are within masking plateau - the NTE is effectively masked, adn the threshold you’re getting from the TE is accurate 

What is the masking plateau ?

A range of masking levels where increasing the masking noise does not change the test ear threshold. It confirms the threshold is valid and unaffected by cross-hearing or overmasking 

What are the two main benefits of using insert headphones durign masking 

1. Decrease chances of overmasking - inserts provide more interaural attenuation, reducing cross over

2. Widen the masking plateau- more room to increase masking without reaching overmasking levels

Why do insert earphones help reduce the risk of overmasking ?

Because they create a better acoustic seal and provide greater interaural attenuation (typically 60 dB) making it less likely for masking noise to cross over to the test ear

What confirms you are in the correct masking plateau using plateau method

When you increase the masking level in the NTE by 15dB total (3×5 dB) without a change in the TE threshold. This confirms the TE result is valid and unaffected by crossover

What kind of noise is used for speech masking

Speech noise - a type of filtered broadband noise designed to match the spectrum of speech 

How is speech noise different from the white noise ?

• Filtered white noise above 100hz

• more energy in lower frequencies 

• mimics the overall energy distribution of speech 

Why is speech noise used for masking instead of white noise ?

Because it better matches the frequency of speech, making it more effective at masking speech signals without being unnecessarily loud 

At what levels are speech recognition tests typically adminstered ?

At suprathreshold levels - above the listeners threshold to evaluate speech understanding, not just detection 

Why is the danger of corss hearing greater in speech recognition tests that in threshold test?

because speech is presented at louder (suprathreshold) levels which are more likely to cross over to the non test ear via bone conduction (BC)

How can air conducted speech signals be heard in the opposite ear?

Through bone conduction - when loud AC signals the skull and reach the cochlea of the non-test ear 

How does the risk of cross- hearing change with speech presentation level

The higher the presentation level, the more likely the non- test ear (NTE) will detect the signal and contribute to the response 

What is the formula to determine the risk of cross hearing in speech testing

SRT of test - Interaural attenuation > best BC threshld of the NTE ; if true masking is needed

What is the typical IA for speech testing with headphones ?

40 dB

What is the typical IA fro speech testing with insert earphones ?

60 dB

What does this formula indicate: SRT TE - 40dB > best BC NTE

It means that cross hearing is possible, and masking is required when using headphones for speech testing 

How does the formula for insert headphones ?

SRT: TE- 60dB > best BC NTE

What are the two key questions if speech masking is necessary

1. Was the response coming from the non-test ear?

2. If so, what is the actual threshold of the ear?

What is the purpose of masking in speech testing

to eliminate the non-test ears contribution when cross hearing is suspected, ensuring the test results reflect the true hearing ability of the test ear