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AUDE 5450 > midterm 1 > Flashcards

midterm 1 Flashcards

1
Q

input

A

intensity of acoustic signal entering the device
-as dB or loudness descriptor in the software

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2
Q

gain

A

amount of amplification added to the input signal
-the dB added to each frequency range and the input level

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3
Q

output

A

intensity of the signal thats delivered to the ear canal
-the signal arriving at the tympanic membrane

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4
Q

equation to describe what is arriving at the tympanic membrane

A

dB input + dB gain = dB output

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5
Q

dB is always within _______

A

dB SPL
-remember there are different conversion factors but these are not intended for everyone

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6
Q

acoustic horn principle

A

as a signal arrives to a large horn and is channeled down to a smaller space, this causes the signal to increase (SPL increases)
-these horns amplify sound when waves are reflected into a narrower area

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7
Q

what are the acoustic benefits with hand cupping

A

-can add clarity to consonants
-can add 5-10 dB of gain
-can attenuate acoustic signals arriving from the rear
-effective for some with borderline hearing/very mild HL around the 1500 Hz area

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8
Q

explain the carbon microphone process and how it goes from acoustic signal to an electrical signal

A

the acoustic signal arrives to the microphone and vibrates the diaphragm which gets compressed and when it moves inward, the carbon balls get pushed together (positive voltage flow). the sound waves goes outward and will bring the diaphragm out with the carbon balls (negative signal)
-this back and forth direction results in an electrical wave that matches the input acoustic signal

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9
Q

what is the purpose of the receiver

A

converting that electrical signal back to an acoustic signal for the ear to hear
-after it becomes an electrical signal it will go through the receiver and will become an acoustic signal again

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10
Q

quick overview of a carbon microphone

A

sound wave → arrives at microphone → pushes on diaphragm and compresses carbon balls → creates a analog signal as the sound wave continues → creates a analog electric signal → receiver picks up the electric signal and makes it back to an acoustic wave

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11
Q

importance of a vacuum tube amplifier

A

this was the first HA with an amplifier that added gain to increase the amplitude of the analogous electrical signal
-vacuum tube amplifier was the first one created/used

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12
Q

transistors

A

electrical component used to increase current flow of the signal
-amplifies the amplitude of a signal

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13
Q

resistors

A

electrical component used to add or remove resistance to the flow of the current
-modifies the output
-can add more or less of certain frequencies

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14
Q

potentiometer

A

small resistors that the amount of control used can modify the output signal in the ear analog HA

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15
Q

function of the potentiometer

A

controls the flow of the signal
-can increase clarity, output and can add in certain frequencies
-can decrease output
-can reduce feedback

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16
Q

3 impression materials

A

addition cured silicone, condensation cured silicone and methyl-methacrylate

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17
Q

viscosity

A

how easily it flows before it is cured
-high will provide resistance during flow, will stretch the aperture
-low is runny, no resistance, no stretch to aperture

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18
Q

shore value

A

if it will remain its shape or will it be altered after its cured
-high or low shore value (will stay or will change)

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19
Q

stress relaxation

A

the materials ability to return to shape after removal from canal
-high and low stress relaxation (bounces back and does not bounce back)

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20
Q

contraction ratio

A

looking at the shrinkage over a 7 day period
-will it be the same or does it shrink

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21
Q

addition cured silicone

A

low viscosity, high shore value, high stress relaxation, will not shrink

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22
Q

condensation cured silicone

A

high viscosity, high shore value, high stress relaxation, will not shrink

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23
Q

methyl-methacrylate

A

medium viscosity, low shore value, low stress relaxation, will shrink

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24
Q

what is the ideal depth for an ear mold impression

A

2 mm beyond the second bend

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25
Q

risk factors within patient Hx

A

-immunocompromised or diabetic (infection risk)
-therapeutic blood thinner (bleeding risk)
-Hx of ear surgery (potential ear canal malformation)
-any allergies to silicone, lubricant ingredients, etc.

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26
Q

risk factors based on otoscopy

A

-collapsing canal (may limit depth)
-perforation or PE tubes
-malformations
-thick hair growth
-piercings (need to cover)

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27
Q

what is the purpose of the open jaw impression

A

they can increase the size of the aperture for a snugger fit
-the condyle of the mandible moves forward and will pull the anterior canal wall with it

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28
Q

how to treat bleeding post impression

A

apply pressure to the wound for 10 minutes using a large cotton otoblock soaked in a vasoconstrictor
-recheck a week later

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29
Q

what frequencies contribute the most to speech intelligibility

A

95% of the information we need to understand a word comes between 500-5000 Hz
-within this, 2000 Hz has the most contribution

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30
Q

linear amplification

A

adds equal amount of gain to soft, moderate and loud input levels
-does not take the dynamic range into account

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31
Q

nonlinear amplification

A

uses compression to increase the intensity of soft signals while decreasing the intensity of loud signals
-output signal is shaped into a reduced dynamic range by adding more gain to soft sounds and less gain to loud sounds

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32
Q

describe the abnormal loudness growth function

A

individuals with HL can have troubles with hearing soft sounds, but loud sounds are equally as loud as normal hearing
-this the is premise behind the abnormal loudness growth
-they have limited/no hearing in low frequencies than perceive louder sounds at that level, results in a reduced dynamic range

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33
Q

how can HL result in an abnormal loudness growth

A

with sensory loss and OHC damage, this can result in the loss of amplification of those soft signals

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34
Q

how do HAs manage frequency specific variations in a persons dynamic range

A

they can alter soft sounds to add gain and can remove gain from loud sounds
-can be done through compression ratios (CR) that can shape the output signal into a reduced dynamic range

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35
Q

frequency resolution

A

refers to the auditory system ability to detect discrete frequencies in the cochlea

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36
Q

how does frequency resolution change with SNHL

A

when OHCs can no longer amplify soft inputs, the basilar membrane can no longer produce the sharp tuning curve, which creates a difficulty hearing in noise
-the primary signal is no longer enhanced and get tangled in with background noise
-these sharp peaks supplies the frequency resolution we need for speech intelligibility

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37
Q

temporal resolution

A

the auditory systems ability to detect small time related changes in the acoustic stimuli over time
-the ability to rapidly pick up and identify different timing elements and processes in order for speech to be intelligible

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38
Q

what processes support temporal resolution

A

-gap detection (spoon vs. soon)
-phonemic duration (the length of words/statements/sounds)
-temporal ordering (boots vs. boost)
-suprasegmentals (patterns of stress, intonation and rhythm)

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39
Q

temporal envelope

A

slow overall change in intensity over time
-the outline, low detail
-supplies speech intelligibility in quiet

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40
Q

temporal fine structure

A

rapid oscillations within the temporal envelope
-detail, more information
-supports detection of signals in noise

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41
Q

what are some benefits of spatial hearing

A

-makes sound localization possible
-able to focus on one conversation
-can unmask sounds that are otherwise obscured by noise

42
Q

interauarl level differences (ILD)

A

differences in loudness arriving to one ear and the other based on where it is coming from
-relies on higher frequencies

43
Q

interauarl timing differences (ITD)

A

differences in timing delays of the signal arriving to one ear and the other ear
-relies on lower frequencies

44
Q

head related transfer function (HRTF)

A

pinna and head affects
-explaining how sound can arrive and be altered in various ways
-measurements within the canal shows patterns of amplitude peaks and notches within high frequency amplitudes as they arrive from different angles

45
Q

explain why two ears are better than one ear

A

-allows ILD, ITD and HRTF signals to be audible
-binaural loudness summation
-improved localization
-binaural squelch
-minimized risk of the unaided ear effect
-suppresses bilateral tinnitus

46
Q

binaural loudness summation

A

action potentials in the brainstem increase loudness when two ears receive auditory input signals
-the patient will perceive greater loudness with bilateral devices
-lower output levels reduce the risk of loudness discomfort or feedback

47
Q

how much gain is seen from binaural loudness summation

A

-in normal thresholds, there is 2-3 dB of gain
-in suprathresholds, there is 5-8 dB of gain

48
Q

binaural squelch

A

the brainstem will manipulate the signal to enhance it
-comparing two signals and the decision is being made for what it should detect and what to ignore

49
Q

benefits of binaural squelch

A

improved intelligibility in noise and the ability to focus on one signal while ignoring others by taking advantage of these different SNRs

50
Q

describe the unaided ear effect

A

it has been found that 25-33% of people with symmetrical loss has suffered from reduced WRS following 1 year of monaural HA usage
-pure tones did not change, but speech intelligibility declined within the unaided ear due to a central mismatch

51
Q

explanation of the binaural process benefits

A

sound localization, sound amplification is more comfortable, better understanding of speech in a noisy environment, better sound quality and can help prevent sensory deprivation

52
Q

bianural interference

A

binaural signals interfere with the ability to understand
-occurs due to age related atrophy of the corpus callosum
-reduced intelligibility in noise occurs

53
Q

what causes HA feedback

A

occurs due to not a snug fit within the canal causing the output to slip outside and can reamplify creating a feedback loop
-sounds like a squawking noise

54
Q

what causes patient complaints of occlusion?

A

the sound of a hollow voice
-occurs due to cartilage vibrating

55
Q

what happens when a microphone gets closer to a receiver?

A

output will decrease when the microphone is closer to the receiver

56
Q

how does microphone placement impact the intensity of the output signal

A

the deeper the microphone is, the more pinna affect will occur so it will increase the signal

57
Q

how does the necessary output relate to recevier and canal size

A

more output calls for a larger receiver which might not fit within small canals

58
Q

ingress protection (IP) rating

A

describes how a device is protected from various materials or contaminants
-various degrees for protection against solids and liquids
-can look at different rates for what the patients is and what they need

59
Q

soft materials are recommended for ___________, harder materials are recommended for _____________

A

hard pinna (pediatrics) ; soft pinna (older adults)

60
Q

vinyl

A

soft but not grippy, can bend
-greatest for infants (up to 4)
-easily modified
-snug fit required fro high gain devices
-shrinks and discolors quickly

61
Q

why is vinyl recommended for infants

A

due to the quick shrinkage and discoloring, there needs replacements often and within the under 4 age group they get replacements around every 3 months. so you can “beat” the pace of shrinkage and discoloration that can occur

62
Q

silicone

A

soft and grippy, can bend and be altered in some ways
-pediatrics are preferred
-tight seal to hold high gain
-durable, does not shrink
-can cause blisters, difficulty to modify, and can get expensive
-platinum and heat cure

63
Q

platinum vs. heat cure

A

most popular type vs. good for high precision needs

64
Q

lucite/acrylic

A

hard material
-best for adults
-easy insertion/removal
-mild to severe loss
-durable, no shrinkage over time
-discrete
-increased risk for feedback

65
Q

earmold retention

A

can occur within various parts of the mold like the cymba, antitragus, tragus, or canal

66
Q

importance of the acoustic seal

A

the output will depend on the acoustic seal
-movement of the ear canal impact this seal
-so choosing the correct material is needed for the proper seal

67
Q

full shell with snap o-ring

A

connects body aid receiver mold
-severe to profound losses

68
Q

full shell mold

A

higher output for severe/profound losses
-easy insertion
-maximized retention and acoustic seal

69
Q

skeleton mold

A

mild to severe HL
-maximized retention and acoustic seal
-like a full shell but hallowed

70
Q

semi skeleton variations

A

portions of the outer rim may be removed allowing easier insertion while maintaining retention

71
Q

canal mold

A

lowest degree of acoustic seal
-good for cosmetics

72
Q

canal lock

A

adds projection into concha for improved retention by antitragus
-good for cosmetics with the retention lock

73
Q

half shell

A

fills half of the concha to improve retention and ease insert
-ease of insertion and retention

74
Q

3 non-custom couplers

A

open, closed/tulip, and power

75
Q

open dome

A

high frequency loss with normal hearing to 1500 Hz

76
Q

closed or tulip dome

A

hearing thresholds better than 40 dB HL below 1000 HL
-provides some mid frequency amplification

77
Q

power (double) dome

A

requires hearing thresholds better than 40 dB HL below 1000 Hz
-provides some amplification to mid and low frequencies

78
Q

what are the primary frequencies affected by the vent effect

A

20-1300 Hz
-lower frequencies

79
Q

purposes of venting

A

-releases low frequencies from the ear canal
-reduces the occlusion effect
-allows unamplified signals to travel directly to the eardrum
-allows aeration of the canal and pressure release

80
Q

vent effect

A

anything that allows for the exchange of air between the EAC and outside air is referred to as a vent effect

81
Q

what can cause the vent effect

A

earmolds with drilled vent bore, open dome, loosely fit closed domes/power domes, and custom earmolds with slit leaks

82
Q

explain the relationship between frequency and the acoustic mass of the vent

A

within the vent, the air has an acoustic mass so in order to cross there needs to be enough inertia to get through
-high frequencies have less energy
-low frequencies have more energy

83
Q

what frequency can travel through the vent

A

low frequencies

84
Q

occlusion effect

A

occurs when lower frequencies of the voice are vibrating within the cartilage portion of the canal
-a common complaint when low frequency threshold loss is better than 50 dB HL
-voices can sound boomy, hollow or like they are in a barrel

85
Q

what can cause the occlusion effect

A

insufficient venting and/or insufficient canal length

86
Q

how do low frequencies correlate with occlusion effect complaints

A

the skull is able to transduce low frequencies generated by the voice and when this bone conduction signal gets trapped in the canal it can release the vibration

87
Q

two techniques to reduce the occlusion effect

A

venting and extending canal length

88
Q

how can venting help reduce the occlusion effect

A

it can release lows out of the canal
-vocalized sounds that cause the OE are within the low frequencies so with venting (and what we know about the inertia needed to get through the vent) it can release these frequencies

89
Q

how can extending canal length help reduce the occlusion effect

A

by extending the canal length (canal portion of the mold) into the bony portion, the waves bouncing around are not able to make it to the cartilage therefore they cannot vibrate within the canal and the OE will not occur
-the waves will be bouncing around within the bony portion so this blocks off the cartilage portion and can reduce the OE

90
Q

as the canal length gets longer, the OE ________

A

decreases

91
Q

direct signal

A

the sound that travels through the vent and hits the TM
-allows patient to hear low frequency signals and environmental sounds naturally when these low frequencies are better than 40 dB

92
Q

amplified signal

A

the sound that goes through the HA and gets to the TM at a higher level
-what has gain

93
Q

3 relationships between the direct and amplified signal

A
  1. the direct signal can be masked by the amplified signal
    -amplified signal is louder than direct signal (20 dB louder)
  2. correct balance occurs
    -equal intensity levels, a good thing
  3. the amplified signal can be masked by the direct signal
    -direct signal is louder than the amplified signal, will complain they cannot hear in noise
94
Q

impact of standing waves in the canal

A

can cause distortion
-can sound fuzzy or distorted

95
Q

increasing vent sizes causes _____ high frequency output

A

less

96
Q

occluding molds allow for around _____ dB of gain

A

40
-supports audibility for 60 dB HL

97
Q

3 mm vent allows for around _____ dB of gain

A

30
-supports audibility to 60 dB HL

98
Q

open domes allow for around _____ dB of gain

A

25
-supports audibility to 50 dB HL

99
Q

parallel vent

A

sound bore and vent travel through the earpiece side by side and do not intersect
-best vent for a custom style

100
Q

angel vent

A

vent intersects the sound bore as close as possible to the tip of the canal
-decreases high frequency output
-increases potential for feedback
-use as a last resort

101
Q

half external vent and trench vent

A

channel from the canal tip, halfway down the canal length that transitions to an internal vent
-behaves like a parallel vent

102
Q

bigger vents are good for _______ thresholds

A

better

AUDE 5450 (4 decks)

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