Aud 705 Diagnostic Audiology Exam 2

Front 1

Immittance

Back 1

A term used in audiology that refers to a group of tests that allows one to infer the status of different parts of the auditory system by measuring changes that occur in the dB SPL of a tone (called probe-tone) that is delivered to the ear canal.

Front 2

Impedance

Back 2

Opposition to the flow of energy. Z Ohms. Z = 1/Y

Front 3

Admittance

Back 3

Amount of energy admitted. Y mmhos. Y = 1/Z

Front 4

What frequency and SPL tone is used for tympanometry?

Back 4

226 Hz at 85 dB SPL

Front 5

Smallest equivalent volume

Back 5

Highest SPL
Least AGC increase
Highest impedance
Lowest admittance

Front 6

Medium equivalent volume

Back 6

Medium SPL
Medium AGC increase
Medium impedance
Medium admittance

Front 7

Largest equivalent volume

Back 7

Lowest SPl
Highest AGC increase
Lowest impedance
Highest admittance

Front 8

Axes for admittance tympanogram

Back 8

Y-axes: Admittance (mmho)
X-axes: Air Pressure (daPa)

Front 9

Ytm

Back 9

Static acoustic admittance of the middle ear. Normal = 0.30-1.70 mmhos

Front 10

Vec

Back 10

equivalent volume of ear canal. Normal = 0.6-2.0 ml

Front 11

TW

Back 11

Tympanometric width. Measured at the point half of Ytm. daPa

Front 12

TPP

Back 12

Tympanometric peak pressure.

Front 13

How does the admittance instrument perform acoustic reflex testing?

Back 13

Tympanometer.
The instrument is measuring the change in admittance that should occur when the middle ear muscle (stapedius) contracts in response to a loud tone, the reflex eliciting tone,that is presented to the ear. If there is an abrupt decrease in admittance when the reflex eliciting tone is presented then the stapedius muscle contracted.
Reflex eliciting tone: 500, 1000 and 2000 Hz
Probe tone: 226 Hz

Front 14

Ipsilateral

Back 14

Probe and stim in same ear.

Front 15

Contralateral

Back 15

Probe and stim in different ear.
Right contra means stim right probe left.

Front 16

What is the criteria to define acoustic reflex threshold?

Back 16

The lowest dB HL of the reflex eliciting tone that produces a repeatable admittance change of at least 0.02 mmhos (or 0.02 ml).

Front 17

What three conditions must be satisfied in order to measure an acoustic reflex?

Back 17

1) Reflex pathway must be sufficiently intact.
2) No OE/ME pathology in probe ear.
3) Reflex eliciting tone loud enough in stim ear. If the ABG is greater than 30 dB the acoustic reflex will usually be absent.

Front 18

Caveats for ART/ARD

Back 18

Normal ARTs do not mean normal hearing.
Abnormal reflexes do not identify pathology.
When differentiating cochlear vs. 8th nerve, must rule out conductive loss.
Can not do ARD without reflexes.
Use reflexes as part of battery.
Ears can have more than one pathology.

Front 19

What frequencies do you use for ARD? Why?

Back 19

500 and/or 1000 Hz reflex eliciting tone using a contralateral recording condition. Higher frequency tones are not useful because a large number of normal hearing ears show positive reflex decay above 1000 Hz.

Front 20

Tympanometry

Back 20

Measures how the probe tone (dB SPL) changes as a function of changes in applied air pressure.

Front 21

Define effective masking levels and give an example.

Back 21

Effective masking is the amount of NB noise necessary to elevate the test signal to a given dB HL (for a given frequency).
These EM levels are calibrated into the audiometer as the amount of EM (in dB) that is needed for 0 dB HL (ANSI, 2004).
E.g. 1000 Hz NB noise, set at 50 dB HL, had an EM level that is sufficient to just mask out a 1000 Hz tone at 50 dB HL.

Front 22

White (broadband) noise

Back 22

Not very effective clinical masker. At the levels we need for masking it is too much for the patient to tolerate.

Front 23

Narrow band noise

Back 23

Noise centered around the frequency we are testing.

Front 24

Speech noise

Back 24

Centered around speech signal.

Front 25

Why is the NTE bone threshold is the “culprit”?

Back 25

Under some testing situations, the presented sound (AC or BC) can cause the skull to vibrate, resulting in vibrations being delivered to both cochleas (through BC).

Front 26

Why is the IA greater for inserts?

Back 26

Inserts have less contact with the skull than supra-aurals, therefore, the skull does not begin to vibrate until 55-75 dB HL and higher.

Front 27

The general rule used to decide if masking is needed for air conduction and bone conduction threshold testing.

Back 27

Whenever the presentation level to test ear exceeds the interaural attenuation and could be audible by BC in the NTE. Compare the presentation level in the TE (AC or BC) to the NTE BC: If this difference is greater than the IA, you must mask to prevent cross-hearing

Front 28

Two examples of when you would not need to mask for bone conduction

Back 28

1) When there is not ABG in the TE.
2) If you test one ear (poorer ear) and get a shift with masking, then the unmasked threshold could be assumed to be an estimate of the other ear without the need for masking.

Front 29

Why and when is the occlusion effect important to consider when masking?

Back 29

It is important when the NTE is using a headphone. Because the occlusion effect causes a noticable increase in low frequency tones when using a bone oscillator.

Front 30

What is masking?

Back 30

The elevation of threshold for one sound (test signal) due to the presence of another signal, called the masker.

Front 31

Why do we mask in clinic?

Back 31

To be sure that the responses we are measuring from the test ear (TE) are truly from the TE and not from the NTE. This is done by eliminating the possibility that the responses could be from the non-test ear (NTE) with a masker in the NTE to “mask out” any crossed over signal.

Front 32

Interaural Attenuation (IA)

Back 32

The amount that the signal level is “reduced” between the TE and the NTE bone. IA is actually due to the minimum dB HL it takes on one side that can cause the skull to vibrate at an audible level.

Front 33

Cross Hearing

Back 33

The level of the stimulus that can be heard by the NTE (after reduction due to IA).

Front 34

Occlusion effect

Back 34

An artificial improvement in the TE BC threshold because the the NTE being covered. This is due to vibrations of the cartilaginous portion of the ear canal.
Occlusion effect: 20 dB at 250 Hz, 15 dB at 500 Hz, 5 dB at 1000 Hz.
Insert earphones are advantageous because with proper placement there will not be occlusion.
You can determine the occlusion effect for a patient based on the ABG.

Front 35

Undermasking

Back 35

The TE response is actually from the NTE bone because there is not enough masking.

Front 36

Plateau

Back 36

TE stable with increases in masker (aim for 30 dB plateau).

Front 37

Initial masking level (IML) for AC masking

Back 37

10 dB above NTE AC threshold.

Front 38

Initial masking level (IML) for BC masking

Back 38

10 dB above the NTE AC threshold plus the occlusion effect if there is no ABG.

Front 39

Overmasking

Back 39

Occurs when masker level in NTE exceeds patient's IA and interferes with TE --> elevating TE threshold. Won't be a significant problem unless you have a bilateral conductive HL of moderate level or worst. The larger the ABG in the NTE, the smaller the available plateau. This is why you should usually test the poorer ear first.

Front 40

Is there a masking dilemma? Two questions to ask

Back 40

Do I need to mask?
Does the initial masking level have the potential to cross over and be a dilemma?

Front 41

Masking for Speech

Back 41

Select a single masker level. Masker level based on best (or estimated) BE in NTE.

Front 42

Rule of thumb for speech masking

Back 42

Present masker to NTE at a level that is 20 dB less than the speech presentation level in TE. However make sure you are not under or overmasking, especially for conductive loss in NTE.