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Diagnostic Audiology I > Hearing Aids I Final > Flashcards

Hearing Aids I Final Flashcards

(81 cards)

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1
Q

occlusion

A

blockage of ear canal

cartilaginous outer 1/3 - vibrates & trapped making own voice louder

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2
Q

microphone

A

converts acoustic to electrical

  1. sound energy enters inlet
  2. creates vibrations on diaphragm
  3. creates movement to & from electrate
  4. generates electronic sinal
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3
Q

low cut

A

inbuilt imperfection of microphone

very low sounds will be dampened due to length of wave

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4
Q

resonance

A

characteristic of cavity
vibrate at max amplitude due to dimentions
4k-5kHz in mic (helmholz)

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5
Q

microphone limitations

A 
low cut
resonance
easily damaged
sensitive to noise
wind noise
internal noise
adds distortions
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6
Q

omni vs directional mic

A

directional - more focus front, cardiod, reduces low freq sounds
omni - 360, sports, kids,

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7
Q

amplifier & parts

A

takes battery power & amplifies signal

diodes, integrated circut (IC), capacitors

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8
Q

peak clipping

A

done primarily by amplifier
sound input above max capacity of HA
adds distortions
(max amp range determined by battery power)

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9
Q

two types of peak clipping

A

symmetrical - odd harmonics clipped

asymmetrical - odd & even harmonics clipped

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10
Q

other distortions

A

complex sound

combination tones

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11
Q

digital hearing aids vs. analog journey

A

digital: M - AMP [analog - digital (numbers) - analog (electric)] R
analog all electrical signal

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12
Q

receiver

A

electric to acoustic transducer
resonance in cavities - all designs prone to resonance
solution - acoustic damper - smoothes peaks dur to resonance
cannot use damper in thin tube - moisture

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13
Q

ALD’s why?

A

hearing aid limits [ noise, distance, reverb ]

benefits everyone

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14
Q

classroom acoustics

A

unoccupied room <35dB SPL

reberb time

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15
Q

RECD

A

real ear coupler difference
use especially for pediatrics
could be dangerous

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16
Q

aural rehab

A
  1. case history
  2. candidacy
  3. HA fitting [verification or functional gain measurements]
  4. Validation
  5. Counseling/Aud training
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17
Q

cavities that simulate ears

A

coupler & ear simulator

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18
Q

limitations of ear simulators

A

delicate
expensive
good with low & high frequencies (better simulate ear)

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19
Q

ANSI Measurements

A

OSPL avg (HFA), OSPL 90, HFA at 50, THD, EIN

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20
Q

why OSPL 90?

A

90 - hearing aid gets saturated

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21
Q

EIN

A

equivalent input noise
only issue if TH in low f good
internal noise

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22
Q

THD

A

Percent not signal

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23
Q

Verification - insertion gain methods

A
  1. Speech mapping

2. Pure tones

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24
Q

dB SPL

A

dB HL+RETSPL+RECD

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25
speech mapping
meet 90% of targets
26
pure tone verification (insertion gain)
REUG - measures gain of ear canal w no amp REAG - with aid REIG - REAG-REUG
27
limitations to insertion gain methods
1. patient cooperation 2. audiologist confidence 3. cost
28
Functional Gain Measurements
unaided & aided gain through sound field testing
29
Advantage to FGA
patient's voice heard
30
resonance of adult canal
2600Hz, higher in kids up to 4k
31
3 types of coupling systems
1. earmold 2. earshell 3. domes (modulated)
32
earmold
deep impressions (fit) - beyond second bend & helix lock severe to profound losses good for pediatrics good hold
33
advantages of deep fit
``` better retention closer to TM: better quality avoids leakage & feedback avoid occlusion effect better self perceived voice ```
34
deep fit limitations
1. helix lock insertion with dexterity issues 2. requires good impression skills 3. pain insertion & removal 4. curvy ear canals
35
modifications of coupling
1. vent 2. dampers 3. sound bore
36
vent
any opening that allows air to move in & out of canal smaller = lower frequencies can escape larger= more higher frequencies can escape
37
adv to vents
1. occlusion affect - allows sounds out (315Hz) 2. helps high frequency HL - taking out low frequencies will prevent upward spread of masking 3. moisture control
38
Disadvantages to vents
1. feedback 2. low frequency hearing loss not rec (low cut) 3. less directionality 4. lower OSPL 90 5. direct sound
39
dampers
800-2500Hz removed for BTE | 1500-3500 Customs
40
Sound bore
horn & reverse horn
41
horn effect
wider opening at canal - changes resonance, +6-+12 in high frequencies
42
reverse horn
narrower at canal reduces amp in high frequency avoid downward spread of masking (high masking low)
43
compression threshold
where compression begins (gain changes)
44
knee point
any point compression ratio changes
45
compression ratio
change in input : change in output
46
limiting
CR = 8:1 or more slowly increasing gain before saturation
47
peak clipping vs. limiting
peak clipping is linear at saturation | limiting is nonlinear lower distortion
48
expansion
less gain to soft sounds | CR: 1:1.1 or more
49
attack time
time required to apply compression
50
release time
time required to release compression
51
overshoot
slow attack time: beyond required output
52
TILL
Treble increase in low levels | more compression in high intensity high frequencies
53
BILL
Bass increase in low levels | more compression in low frequency high intensity sounds
54
types of compression
1. low level - more compression in soft sounds, loud linear 2. wide dynamic range - compression at all levels 3. high level - more compression in loud sounds, soft sounds more linear
55
compression benefits
1. safe, comfort 2. SNR improvement 3. reduces intesity difference bt sp sounds 4. normalizes loudness 5. may improve intelligibility
56
compression limitations
1. distortion 2. benefits not as high older users - linear - power 3. AT/RT variation
57
bands
gain for specific frequencies
58
channels
compression ratio for specific frequency regions
59
open fitting issues for directionality
1. low frequency leakage 2. direct sound 3. creates third source of sound
60
directional benefit factors
1. directivity of hearing aid (internal & external delay) 2. reverberation 3. distance of noise & speaker
61
listening situations
1. speech close, noise far 2. speech far, noise close 3. noise close, speech close 4. speech far, noise far (same direction) - directivity not helpful
62
SNR benefit from directionality
2-3dB
63
directional processing happens when
first - affected by compression
64
compression affect on directionality
reduces front-back difference: reduces SNR benefit from front, helps back
65
localization & compression
cues are reduced by compression - reduces interaural time difference
66
directivity disadvantages
``` low cut responses target sounds from back or side greater internal noise reduced localization wind noise requires closed fitting ```
67
noise reduction
winer filter | spectral subtraction
68
noise characteristics
``` low f random low intensity less variation narrow modulation depth ```
69
winer filter
reduce gain in poor SNR channel
70
spectral subtraction
mic analyzes signal & estimates noise & eliminates
71
feedback reduction
closed fitting 1. gain reduction 2. phase cancellation 3. path cancellation
72
gain reduction
reduce overall gain or in specific region
73
phase cancellation
detects where feedback happens, alternate wave generated to cancel
74
path cancellation
feedback detector cancels signal before getting to the mic
75
frequency lowering
1. compression | 2. transposition
76
frequency compression
reduces frequency separation
77
frequency transposition
uses existing frequencies
78
free field
no reverb
79
diffuse field
exert substantial effects on waves, equally distributed
80
quasi - free
minimal reverb moderate affect
81
signals in sound field
pure tones - standing waves warbles (FM) narrow band noise

Diagnostic Audiology I (2 decks)

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