L6: Immittance COPY

Question 1

What do “stim” and “contra” represent on an audiogram?

Answer 1

they are reflex thresholds

Question 2

what population is tympanometry most common to do in and why?

Answer 2

pediatric because they commonly have middle ear problems

Question 3

What is acoustic immittance?

Answer 3

it is a measaurement of of how easily sound energy can flow through the middle ear.

Question 4

what information does tympanometry provide us?

Answer 4

rich information about the middle ear– it measures acoustic immittance by collecting information about the movement of the eardrum and the pressure in the ear

Question 5

Tympanometry is ___ to obtain

Answer 5

easy

Question 6

what information do acoustic reflexes provide us?

Answer 6

• mainly info about auditory and facial nerves and the lower brainstem
• some information about hearing

Question 7

acoustic reflexes are ____ to obtain

Answer 7

easy

Question 8

what is acoustic impedance?

Answer 8

the degree to which a sounnd is absorbed or not absorbed by something

Question 9

High impedance = (____) absorption

Answer 9

low absorption

the material is impeding the absorption

Question 10

Low impedance = ____ absorption

Answer 10

high absorption

low impedance means very little stopping the absorption

Question 11

How does impedance work in the ear (where is sound absorbed)?

Answer 11

sound is absorbed from the ear canal into the ossicular chain when acoustic energy sets the ossicular chain in motion

Question 12

Under what impedance condition would the ossicular chain move well?

Answer 12

low impedance

Question 13

If your at a bar and your favourite song comes on and it makes you want to dance your life away, what level of impedance are you experiencing?

Answer 13

Low impedance (things are moving more freely)

Question 14

does low impedance equate to better hearing?

Answer 14

NO
there might be low impedance, and the ossicular chain freely moving BUT it is due to ossicular disconnection (bad hearing outcome)

Question 15

What are the three componnents of impedance?

Answer 15

Stiffness, Mass, Resistance

Question 16

In the middle ear, friction is basically ____

Answer 16

negligible

Question 17

How would increasing the resistance (friction) in the system impact impedance?

Answer 17

there would be a loss of energy that is NOT dependent on frequency

resistance is minnimal in ear system

Question 18

Which two components do play a role in the ear system?

Answer 18

stiffness and mass

Question 19

What is mass reactance?

Answer 19

• the opposition to the movement of a mass in a system due to its inertia
• it is a component of impedance
• it increases as frequency goes up

Question 20

why is it more difficult to move larger masses back and forth quickly?

Answer 20

due to acceleration – takes longer to aaccelerate and decelerate the mass

Question 21

a larger mass will have ____ mass reactance and ____ impedance for high frequencies

Answer 21

higher, higher/more

Question 22

a larger mass will move better at a ____frequeny

Answer 22

low

Question 23

for a larger mass at low frequencies, there is ____ mass reactance and thus ____ impedance

Answer 23

less, lower

Question 24

Examples of lower frequency things that make sounds

hint: bigger things make lower frequency sounds

Answer 24

tuba, kick drum,

Question 25

What is stiffness reactance?

Answer 25

- component of impedance that involves elastic properties

Question 26

stiffness reactance _\_\_\_ as frequency _\_\_\_

Answer 26

stiffness reactance decreases as frequency goes up

Question 27

If something is very stiff it wants to return to the resting position _\_\_\_, than if it was looser

Answer 27

faster

Question 28

what does high stiffness interfere with?

Answer 28

low frequencies

Question 29

at low frequencies there is _\_\_\_ stiffness reactance and thus _\_\_\_ impedance

Answer 29

low frequencies: more stiffness reactance and more impedance

Question 30

what frequency level would a highly stiff system move best at?

Answer 30

high frequency level

Question 31

at high frequencies, a highly stiff system would have _\_\_\_stiffness reactance anda thus _\_\_\_ impedance

Answer 31

at high frequencies: a highly stiff system would have less stiffness reactance anda thus less impedance

Question 32

Which frequencies will be heard better when our tympanic membrane and ossicles are stiff?

Answer 32

high frequencies

Question 33

which frequencies will be heard better if our middle ear unit is more relaxed/looser?

Answer 33

lower frequencies

Question 34

why is resistance on a different plane than stiffness and mass?

Answer 34

because resistance is independent to frequency, whereasa stiffness and mass are influenced by frequency

Question 35

mass reactance and stiffness reactance are _\_\_\_ related to frequency

Answer 35

inversely

Question 36

How does increasing the frequency influence mass reactance and stiffness reactance?

Answer 36

increasing frequency will increase mass reactance but decrease stiffness reactance

Question 37

how will decreasing frequency influence mass reactance and stiffness reactance?

Answer 37

decreasing frequency will decrease mass reactance and increase stiffness reactance

Question 38

what mass and stiffness are in balance (cancel out), the frequency would be \_\_\_

Answer 38

resonant

Question 39

what is the resonant frequenccy of the middle ear?

Answer 39

800 to 1200Hz

Question 40

changes in middle ear impedance are primarily due to changes in what?

Answer 40

stiffness (mass and resistance are negligible in middles ear)

Question 41

What are clinical impedance measure comparable to?

Answer 41

stiffness measures

Question 42

Which frequencies are not transmitted as well due to high stiffness and low mass in the middle ear?

Answer 42

low frequencies

Question 43

how could you improve low frequencies?

Answer 43

making the system less stiff

Question 44

which frequencies are not transmitted ass well due to the presence of some mass?

Answer 44

high frequencies

Question 45

how could we improve high frequency response?

Answer 45

reduce the mass and make it stiffer

Question 46

clinically what do we typically say instead of impedance?

Answer 46

admittance

Question 47

what is admittance?

Answer 47

opposite of impedance, it is how much energy is absorbed

Question 48

what is admittance measure?

Answer 48

mhos | usually milli-mhos

Question 49

what is immittance

Answer 49

general term that referes to both impedance and admittance

Question 50

\_\_\_ admittance = low impedance

Answer 50

high admittance=low impedance

Question 51

\_\_\_\_ admittance = high impedance

Answer 51

low admittance = high impedance

Question 52

what is acoustic admittance equal to?

Answer 52

sound flow (volume velocity)/sound pressure

Question 53

how can acoustic admittance be estimated?

Answer 53

by measuring the reflected sound, anything not reflected would be admitted

Question 54

when admittance is high, reflection is \_\_\_?

Answer 54

low

Question 55

when admittance is low, reflection is \_\_\_?

Answer 55

high ## Footnote not alot beeing absorbed, so high reflection

Question 56

when admittance is low, the middle ear unit has high impedance, what level of stiffness does it have?

Answer 56

high stiffness because it has low admittance

Question 57

what pathological conditions are associated with decreased admittance (more stiff)?

Answer 57

1. Otitis media (fluid cause ossicles to be stiffer) 2. ossicular fixation 3. no middle ear space (very stiff, admittance very low)

Question 58

what pathological conditions are associated with increased admittance (less stiff)?

Answer 58

ossiccular discontinuity (dislocataed ossicles)

Question 59

how does admittance relate to volume?

Answer 59

a larger volume space would absorb more energy (less reflection)

Question 60

Why is 226Hz used to test admittance? | related to volume and sea level

Answer 60

for a 226Hz tone at sea level, air in a 1cm^3 (or 1 ml) cavity hass about 1millimho of admittance so, 1mmho of admittance = 1cm^3 of space (one to one relationship)

Question 61

How do we measure ONLY middle ear admittance?

Answer 61

need to subtract the outer ear admittance from the total ear admittance

Question 62

how do we isolate the outer ear admittance?

Answer 62

- we need admittance to be of middle ear to be very low, so we can make the tympanic membrane very stiff by usinng air pressure, so that it does not move and acts as a wall - then the tympanic membrane will reflect energy, rather than admitting it to the middle ear space

Question 63

how much should we tighten the ear drum?

Answer 63

as much as possible without pain

Question 64

what are the 2 ways we can achieve zero middle ear admittance?

Answer 64

1. add pressure to the ear, creating negative pressure in the middle eaer space (retracted TM) 2. remove pressuree from the ear, creating positive pressure in the middle ear space (TM pushed out)

Question 65

In order to vary the pressure in the eaar, we ned a good \_\_\_\_?

Answer 65

seal

Question 66

review these points

Answer 66

- when pressure (on x-axis) is low or high, we are looking at ONLY outer ear admittance - the peak in between is both middle and outer ear admittance

Question 67

What did Paul Madson create?

Answer 67

the tympanometer

Question 68

what is a tympanometer?

Answer 68

it is a device that has a pump, speaker, and microphone

Question 69

what frequency tone does the tympanometer play?

Answer 69

226 Hz

Question 70

where on a tympannogram is the eardrum moving its best?

Answer 70

at the peak

Question 71

how do we release negative aair pressure in the ear?

Answer 71

we need to match the pressure - if there is negative pressure behind eara drum, then we need negative pressure in front of ear drum to equalize it

Question 72

what does the peak tell us about pressure levels

Answer 72

tells you what the pressure is behind the eardrum - if the person has -50 pressure behind ear drum then the peak of the tymp will be at -50 - if the person yawned and the pressure behind eardrum become 0, then the peak shifts to 0 - peak is at 0 when at atmospheric pressure

Question 73

what does the peeak of a tymp tell us about admittance?

Answer 73

it is peak admittance -- the TM and ossicles are maximally set in motion,

Question 74

what does thee line on a tympanogram represent?

Answer 74

the admittance at different pressure levels

Question 75

what is static compliance of middle ear

Answer 75

the admittance of the middle ear

Question 76

what is a compensated tympanogram?

Answer 76

it is when the OE admittance is subtracted from the OE+ME admittance automatically (the line gets shifted down to sit on x-axis) - the volume of ear canal will be given to you