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Second Yr Comps > Amp I > Flashcards

Amp I Flashcards

1
Q

Careful visualization of this area of the external auditory canal during otoscopy allows audiologists to identify the location of the second bend.

A

Anterior canal wall

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2
Q

Ideally, the canal length of an earmold impression will reach this depth to supply all the necessary information on anatomy an earmold manufacturer requires

A

2mm past the second bend

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3
Q

Combines 1:1 polyvinyl-siloxane parts of paste

A

Addition-cured silicone

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4
Q

Dimethyl-siloxane paste mixed with hardener

A

Condensation-cured silicone

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5
Q

Pre-measured acrylic powder and liquid formulas are rapidly mixed together

A

Methyl-Methacrylate

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6
Q

What is the primary reason for using high-viscosity impression material when making earmold impressions?

A

It supplies maximum stretch of the aperture

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7
Q

Which three case history questions must be asked immediately before every earmold impression is taken (even when you’re working with a well-established patient!)

A

Are you immunocompromised; have you ever had surgery on your ears; do you take blood thinners

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8
Q

To effectively assess the external auditory canal using diagnostic otoscopy, the audiologist may sit or stand. The viewing position and angle do not make a difference

A

False

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9
Q

Earmold impressions should not be taken when a perforation of PE tube is present

A

False

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10
Q

This type of otoblock allows the audiologist to create a longer impression of the external auditory canal with less patient discomfort.

A

Cotton otoblock that’s equal in size to the EAC entrance

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11
Q

You feel resistance during otoblock insertion suggesting you’ve chosen the correct size. If the resistance suddenly decreases as you move it more deeply in the canal it indicates

A

the patients ear canal widens beyond the 2nd bend

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12
Q

Open jaw impressions

A

Increase the size of the aperture

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13
Q

What would you do for PT with BTE in humid environments that sweats a lot?

A

High ingress protection rating

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14
Q

What does changing a vent size effect

A

Low frequencies and high frequencies

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15
Q

3 temporal resolution cues

A
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16
Q

What would not change with length of impression?

A

Standing waves in the ear canal

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17
Q

Explain how Electric mic transduces an acoustic signal into an analogous electric signal

A

The electret mic has an electret film applied to the backplate that is pre-charged with electrons to provide the voltage that is needed to transduce a signal. The acoustic signals arrive at the mic where they are transduced into an analog electric signal. The acoustic signal pushes against the diaphragm, decreasing the space between it and the pre-charged electric backplate. The pushing in of the diaphragm to the back plate condenses the particles causing a positive analog signal. When the diaphragm pulls back out it causes rarefaction of the particles and a negative analog signal. This push and pull of the diaphragm in sync with the acoustic sine wave against the pre-charged backplate creates the + and - analog electric signal in an electret mic

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18
Q

What are the limitations of electric microphones? How does MEMS overcome these problems?

A

The electret microphone requires a diaphragm and electron stability to maintain microphone sensitivity. Environmental factors, such as humidity, and temperature extremes can degrade the microphone. The diaphragm can absorb moisture which limits movement, and breakdown the adhesive required to hold it in place. Temperature extremes can cause electron loss from the electret backplate
The MEMS mic overcomes these concerns by using a silicone disc for the diaphragm, so it does not rely on adhesives, and by the addition of a charge pump to replace lost electrons and maintain the electrical held.

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19
Q

A PT has digital HA. HA distorts when they have louder acoustic signals, like a symphony. Could be front end distortion. What is it and how is it caused

A

Front-end distortion describes a microphone limitation associated with its dynamic range. The microphone dynamic range is the difference between the mics noise Roor and the loudest signal it can collect. 16-bit digital hearing aids can ahly collect signals up to 96 dB before going into saturation. Signals louder than this will be clipped adding distortion to the output signal.

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20
Q

Real world snr is ______ because of head shadow and polar plots

A

2-3

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21
Q

If Signal was 76 and noise 74 what is SNR?

A

2 dB

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22
Q

Greatest directivity index -

A

hypercartiod

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23
Q

There is a blockage at the back port. Why can this mic no longer make nulls and no longer function as a directional mic but an omnidirectional mic

A

When something plug the port, the sound coming in from the back doesn’t reach the diaphragm which doesn’t cause an out of phase signal which means no directionality occurs

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24
Q

How does a telecoil create an analog electric signal

A

A telecoil transduces an electromagnetic signal instead of an acoustic signal by applying the induction principle. A small magnet sits inside a tightly wound copper coil creating an electromagnetic field. The electromagnetic signal pushes and pulls the magnet. This movement inside the copper coil produces a positive and negative electrical current flow analogous to the incoming electromagnetic signal.

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25
Q

directional microphone function which is true:
Directivity index reduces as diaphragm adhesive degrades
All of these answers are true
Directional microphone roll off increases as the external time delay decreases
Directivity index reduces when directional microphone ports are not parallel to the floor

A

all

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26
Q

Issues understanding at a bar. Lombard reflex increases the intensity of your friend’s voice in this environment. They speak at 76 dB SPL. Noise level is 74 dB. SPL What is the SNR

A

2

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27
Q

As the distance increases between an acoustic signal and microphone:
The arriving signal to noise ratio decreases
The arriving signal becomes softer but the signal to noise ratio does not change
The arriving signal to noise ratio increases

A

The arriving signal to noise ratio decreases

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28
Q

The hypercartiod polar plot supplies the highest directional microphoneDI, In a research lab, the Hypercartiod polar plot DI is ________ dB. The Di reduces in the real world to ________ dB because of the head shadow effect

A

6
2-3

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29
Q

How does an acoustic signal’s input and output change with 2.5:1 compression ratio

A

Each time the input signals intensity increases by 2.5 dB SPL, the output signal increases by only 1 dB SPL

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30
Q

How does WDRC help to restore normal loudness growth but linear signal processing cannot?

A

Linear signal processing adds the same amount of gain to soft, moderate, and loud input signals, white WDRC adds more gain to soft input signals than it does to loud. As a result, when the volume of a linear signal is increased soft signals remain under-amplified and inaudible, moderate signals may be raised so the output is comfortable, but loud signals are then over amplified and perceived as too loud.
In contrast, WDRC adds more gain to soft input signals for improved audibility but slowly reduces gain as the input signal becomes louder. In this way, the amplified signal is squeezed or reshaped into the dynamic range so that soft sounds are audible and are perceived as soft.
moderate sounds are perceived as comfortable and loud sounds are perceived as loud but remain below uncomfortable loudness levels.

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31
Q

Equilization filters

A

adds LF gain when _____

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32
Q

Vertical telecoil

A

optimizes collection of signals in a looped room

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33
Q

Horizontal telecoilf

A

optimizes collection of signals in a telephone

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34
Q

OLC

A

7:1 CR is applied, _____

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35
Q

WDRC:

A

1.3:1 CR is applied, ___

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36
Q

Fast acting compression

A

reduces the chance of discomfort _____ overshoot?

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37
Q

Slow compression release time:

A

reduces audibility of soft sounds _____

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38
Q

ACG-i:

A

level detector that _____

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39
Q

Compression shaping channels

A

allows frequency specific compression of ___

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40
Q

Frequency shaping bands:

A

allows frequency specific compression of ____

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41
Q

Fast acting compression:

A

alters the speech envelope ____

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42
Q

AGC-i:

A

TK input level increases ____

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43
Q

AGC-o:

A

TK input level decreases ____

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44
Q

which statement about the threshold kneepoint (TK) IS NOT TRUE
Lowering the TX to a softer inout intensity increases the output of the louder input signals
lowering the TK to a softer input intensity will not change the output of the louder input signals
raising the TK to a loader input signal decreases the output of signas below the le
lowering the TK to a softer input intensity increases the output of sigruls below the TK

A

Lowering the TX to a softer inout intensity increases the output of the louder input signals

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45
Q

Peak-clipping adds extra frequencies to the input signal causing distortion of the output signal. Output limiting compression does not cause distortion. Is this true or false

A

FALSE- all compression modifies the signal in a way that allows the addition of frequencies which result in distortion. Lower compression ratios are associated with less distortion than higher compression ratios. Linear signal processing does not add distortion

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46
Q

Very soft acoustic signals below the first threshold kneepoint (TK) are attenuated by applying

A

Expansion

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47
Q

Why is slow-acting compression recommended for patients with reduced cognitive function?

A

Slow-acting compression is recommended because in last-acting compression, it alters the temporal envelope of the signal and this altering results in a different signal than what was stored in our brain of what the signal should be. Fast acting compression results in us using more working memory and listening effort in order to make sense of this signal that no longen matches what the brain has stored. Therefore, the opposite happens with slow acting compression. it restores the temporal envelope and is easier for those with reduced cognitive function to understand because it better matches what is stored in our brain causing them to use less working memory and less listening effort

Fast Ats significantly change the spectral envelope shape. More working memory is needed to interpret the temporal characteristics of this new speech signal. Patients with lower cognitive abilities have a difficult time “matching” the compressed signal to their memory of the signal

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48
Q

What does the test mic do?

A
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49
Q

What does the coupler mic do?

A
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50
Q

What signal is emitted from the T in the box

A

electromagnetic

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51
Q

What is SPLIT & RSETS?
What is SPLIV & RTSLP? How are they different?

A
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52
Q

Advantages for each type and disadvantages of each type of earmold material

A
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53
Q

find the tragus on the mold, antihelix & the aperture

A
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54
Q

what is input

A

Intensity of acoustic signal entering the device

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55
Q

what is gain

A

amount of amp added to input

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56
Q

what is output

A

Intensity of signal that is delivered into the ear canal

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57
Q

if soft is 50dB and we add 17 at around 3300 Hz, output signal?

A

output = 67dB

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58
Q

SPL-o-gram

A

Shows audiometric thresholds in SPL

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59
Q

what is the acoustic horn principle

A

as a signal arrives to a large horn, channeled down into a small space, the signal is increased (SPL increases)
1: wider opening more sound is collected (more input energy in)
2: longer the horn the more amplification you get (channeling signal into smaller spaces into longer period of time

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60
Q

Increased horn length =

A

SPL increase energy to the ™

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61
Q

what are frequency response curves

A

Compare intensity of the input signal to either the added gain or final output of the device

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62
Q

Acoustic benefits associated with hand cupping

A

Added +5 to 10dB of gain to the input signal in mid to high frequencies

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63
Q

what is amplified in hand cupping

A

consonant sounds
soft that do not have a lot of energy are collected by the hand and are going into the narrower space to get louder (10-15 dB)

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64
Q

Understand how a carbon microphone works. Specifically, how it converts an acoustic signal to an electrical signal

A

sound waves come, hit diaphragm and compress it
when it moved in, the carbon balls are pushed together creating pos voltage flow, sound waves go back and forth so when it goes back so does the diaphragm so the balls decompress
compression and decompression of carbon creates a + and - electrical current
sound has positive peaks and negative
these hit d, compress/decompress the carbon balls, and because it created the +/- current flow, the electrical current matched the acoustic sign wave
input signal is blue and comes in it changed and what came out looks the same but it wasn’t sound
transferred acoustic signal to electric signal that looked identical
it is an analog electric signal

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65
Q

Describe the purpose of the receiver

A

The receiver converts analogous electric signal back to an acoustic signal

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66
Q

Describe the purpose of the vacuum tube amplifier

A

Vacuum tube amplifier added gain to increase amplitude of the analogous electrical signal

heater element, catho (plate) and by process of the grid opening and closing it could be used to increase/expand the amplitude of the signal

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67
Q

what is a translator

A

Electrical component used to increase current flow of electronic signals (increases amplitude)
to increase current flow of electric signal (amplifier)
takes analog electric signal and increases its amplitude
amplify the electric signal

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68
Q

Resistor

A

Electrical component used to add or remove resistance to the flow of electrical current (modifies frequency response or output)
manipulate the signal in some way
electrical component
added to resist flow
maybe we dont want amplitude in all frequencies, maybe we want to add compression to the signal so we use these to change and manipulate the electrical flow of the signal

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69
Q

what are integrated circuit

A

combine multiple transistors & resistors into a single component

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70
Q

conduct electrical sine signal

A

transistors

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71
Q

impede the electrical sine signal

A

resistors

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72
Q

A small resistor control used to modify output signals in early analog HAs
Manipulated output signal, frequency response, amount of gain added & compression ratio
Aka trimmer pot or pot screw

A

Potentiometer

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73
Q

becomes the helix lock for retention

A

valley

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74
Q

two goals of impressions

A

Goal 1: go 2mm beyond
Goal 2: stretch aperture

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75
Q

How easily material flows before it cures; thickness

A

viscosity

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76
Q

Flows easily with little resistance
Most suitable for devices requiring deep insertion

A

low viscosity

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77
Q

Thick; more energy to force the material into the ear canal
Provides resistance during flow
stretches aperature

A

high viscosity

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78
Q

Describe the importance of stretching the aperture

A

stretching this area for a well fit earmold
if we do not do this we get an uncomfortable earmold because the skin rubs against the plastic

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79
Q

Materials ability to return to its shape after removal

A

stress relaxation

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80
Q

you can pull on it and it will pop back into shape and won’t change at all

A

High stress-

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81
Q

Shrinkage over a 7 day period

A

contraction ratio

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81
Q

distorts as you pull it out of the ear

A

low stress

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82
Q

After cure hardness
Stability in the impression box

A

shore value

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83
Q

ideal otoblock placement

A

2mm beyond second bend

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84
Q

should be larger than entrance of the external canal

A

foam

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85
Q

should be about the same size as the entrance

A

cotton

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86
Q

purpose of open jaw impressions

A

Increases the size of the aperture for a snugger fit

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87
Q

If you have a threshold loss, can you hear soft sounds?

A

no

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88
Q

Impact of Threshold loss on audibility

A

i can hear people but I don’t understand them

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89
Q

critical for speech understanding

A

hf audibility

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90
Q

what supports intelligibility

A

audibility of hf consonants

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91
Q

The relative contribution of the consonant frequencies to the understanding of speech is shown by the fact that nearly 70% of word recognition is determined by speech energy between

A

500-2000 Hz

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92
Q

What’s the difference between linear and nonlinear amplification

A

linear: Adds an equal amount of gain to soft, moderate and loud input levels

nonlinear: increase intensity of soft signals while decreasing intensity of loud signals

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93
Q

what is automatic gain control

A

Applies different amounts of gain to different input levels

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94
Q

what is dynamic range

A

range bw softest audible sound and loudest tolerable sound

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95
Q

what is loudness growth

A

Perception of loudness as stimulus intensity increases

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96
Q

Loudness grows more rapidly for certain listeners than normal listeners with changesin level, reducing the persons dynamic range

A

abnormal loudness growth

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97
Q

Individuals with threshold loss perceive sound shifting from too soft to too loud more rapidly

A

abnormal loudness growth

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98
Q

what results in abnormal loudness growth

A

OHC damage
abnormal growth happens (perception) due to PT not hearing softer sounds because the amplifiers are gone and rapidly the sound goes from soft to too loud

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99
Q

How do modern hearing aids manage frequency specific variations in a person’s dynamic range?

A

Amplification applies different compression ratios across frequency ranges to shape an output signal into a reduced dynamic range

this is done by manipulating compression in frequency shaping channels

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100
Q

what is frequency resolution

A

Auditory systems ability to detect discrete frequencies in the cochlea

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101
Q

Describe how frequency resolution changes with SNHL. Why does reduced frequency resolution make it difficult to understand speech in noise?

A

When frequency resolution is decreased, the primary signal is no longer enhanced making it difficult to differentiate the desired signal (speech) from the undesired signal (noise).

The brain can’t “untangle” the desired speech signal from the undesired noise, so understanding is diminished

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102
Q

what is upward spread of masking

A

Intense low frequencies mask weaker higher frequencies

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103
Q

what is temporal resolution

A

AS ability to detect small time related changes in acoustic stimuli over time
Good auditory

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104
Q

what are the auditory processes that support temporal resolution

A

Gap detection
brief gaps of pauses between syllables, words, sentences, etc (spoon vs soon)

Phonemic duration - differences in duration and order (can vs cant)

temporal ordering - boots vs boost

suprasegmentals - provides meaning (patterns of stress, intonation, rhythm)

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105
Q

temporal envelope vs temporal fine structure
How will audibility of these features impact speech intelligibility?

A

TFS - Very rapid fine oscillations that provide information on timing within the temporal envelope
Supports detectioin of speech & nonspeech signals in noise

TE - Slow overall change in intensity over time
cues are associated with speech perception in quiet

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106
Q

Describe the benefits spatial hearing supplies

A

Makes it possible to tell where a sound is coming from in space
determines direction of a sound source

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107
Q

what are interaural timing differences

A

Amount of time bw sound arriving to one ear to the other ear
One arrives faster than the other

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108
Q

what are interaural level differences

A

Difference of volume bw two ears

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109
Q

Which frequencies supply the most information on interaural level differences?

A

High frequencies (>3 kHz) to identify ear to ear head shadow level differences

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110
Q

Which frequencies supply the most information on interaural timing differences?

A

Low frequencies (<850 Hz) to identify spatial location & sound source

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111
Q

Spatial hearing allows us to

A

Determine location of a sound source
Unmask sounds otherwise masked by noise
Brain combines and analyzes info arriving from both ears for improved signal detection & identification of speech in noise
Shift our attention and focus on one sound source while ignoring another
Feel connected with the environment

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112
Q

Explain HRTF. What information do these monaural spectral cues supply?

A

describes the spectral characteristics of sound as measured at the tympanic membrane when the sound source originates in 3D space

Each pinna interacts with incoming sound waves differently, depending on the sound’s source relative to our bodies.
This interaction provides a monaural spectral cue that is helpful in locating sounds that occur above or below and in front or behind us.

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113
Q

Does a discussion of audiometric thresholds sufficiently explain why a patient is experiencing communication difficulties? How could an audiologist supply a patient with a better understanding of their auditory rehabilitation needs during post diagnostic counseling?

A

Audiograms are not predictive of the activity limitations resulting from a hearing loss

Amplification will not restore any of these functions, in fact, it can make it worse at times
Diagnosing the problem doesn’t help the PT. Providing a comprehensive plan of care that includes amplification does. How you approach the treatment plan will determine if you are a doctor or simply a salesman

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114
Q

Explain the five benefits associated with use of bilateral amplification. Recognize how each benefit supports improved speech intelligibility in quiet or in noise.

A

1 Allows audibility of ILD, ITD & HRTF signals

2 Binaural loudness summation
Results in PT perceiving greater loudness w/ bilateral devices
In quiet?
Less gain is needed to reach comfortable listening levels
Can fit a PT with less loudness in order for them to hear the words

3 Improved localization

4 Binaural squelch (binaural release of masking)
Signal to noise ratio:
if speech is louder than noise, makes it easier to understand in noise = +
if speech is softer than noise, makes it challenging to understand in noise = -

Leads to improved intelligibility in noise & ability to focus on 1 signal while ignoring others by taking advantage of these differing SNRs
The brainstem uses the differences in speech and noise ITDs/ILDs to enhance focus on speech signals while suppressing noise
Research shows binaural hearing offers an SNR improvement of 2-3 dB

5 Minimizes risk of “unaided ear effect”

6 Suppresses bilateral tinnitus

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115
Q

Explain binaural loudness summation. Its suprathreshold benefits and how this benefit supports hearing aid fitting strategies.

A

Results in PT perceiving greater loudness w/ bilateral devices
Less gain is needed to reach comfortable listening levels
Can fit a PT with less loudness in order for them to hear the words

@ threshold increase only around 2-3dB
@ suprathreshold increase around 6-8dB

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116
Q

Explain binaural squelch and the benefit this auditory process supplies

A

ability of the auditory system to combine the information from both ears centrally and segregate the speech from the noise by the differences in sound between both ears.

Leads to improved intelligibility in noise & ability to focus on 1 signal while ignoring others by taking advantage of these differing SNRs

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117
Q

Describe the research findings related to the “unaided ear effect

A

Research found ~25-33% of individuals with symmetric loss suffered from reduced word recognition scores following 1 year of monaural hearing aid use.

likely due to a central mismatch due to a strong consistent signal received though the aided ear.
The brain pays more attention to the dominant ear overtime, ignoring the ear with the weaker signal

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118
Q

Be prepared to explain each binaural process in a simple way that supports a patient’s understanding of the benefit

A

amp is less loud and more balance
more natural and better tolerated
easier to hear higher pitches
easier to hear speech in noisy environment
easier to better hear speech in the presence of noise

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119
Q

amp is less loud and more balance
more natural and better tolerated
easier to hear higher pitches
easier to hear speech in noisy environment
easier to better hear speech in the presence of noise

A

Reduced intelligibility in noise with bilateral amplification

Reported in 5-10% of older PTs with bilateral amp
Progressive age-related atrophy of the corpus callosum reduces speech intelligibility with binaural input

poorer speech recognition with both ears than with the better ear alone

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120
Q

Near normal low frequency hearing typically doesn’t require an amplified signal because the intensity of a “direct signal” is audible without amplification

A

true

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121
Q

what is feedback

A

amplified sound that leaks back out and is reamplified
makes squealing sound

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122
Q

What causes a hearing aid to feedback?

A

HA isn’t snug enough in the ear, output leaks out side of HA and the amp signal is picked up by the HA and creates a feedback loop

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123
Q

What causes patient complaints of occlusion?

A

increased perception of your own voice when something blocks the ear canals
can occur with ha that has dome that closes off ear or HA with earmold with not large enough vent size

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124
Q

What happens when a microphone gets closer to a receiver?

A

closer microphone and receiver are together the less output you can get because it drives feedback

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125
Q

Describe signal changes resulting from the pinna effect

A

Pinna naturally adds gain & provides valuable spatial awareness cues
The pinna effect boosts the intensity of HF signals (specifically 3k Hz region) by ~7 dB SPL

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126
Q

How will microphone placement impact the intensity of the output signal arriving to the TM?

A

The combination of the pinna effect & microphone location will increase the output signal and decrease wind noise

CIC & IIC get pinna benefits the most

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127
Q

How will the canal volume b/w the receiver and TM impact the intensity of the output signal arriving to the TM?

A

Sound bore proximity to ™ increases device output

The output arriving to the TM increases by ~6 dB SPL when the volume b/w the TM and receiver reduces

The combination of a deep microphone placement and deeply fit devices increases output by ~13 dB SPL

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128
Q

What does an IP rating indicate? What does a 6/8 IP rating suggest?

A

what we look at in BTE to decide is the device dust and moisture resistance

IP68
Dust light
Protects against long periods of liquid immersion

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129
Q

BTE fitting range

A

all degrees of HL
no pinna effect
output can modify based on acoustic parameters

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130
Q

what are the acoustic parameter

A

venting
damping
sound bore

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131
Q

slim tube fitting range (RITA)

A

mild to mod
25-55
no PE
HF output is limited by vent size and tube soundbore

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132
Q

RIC fitting range

A

minimal to severe
-10 to 90
no PE
output dependent on receiver size and earmold style

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133
Q

ITE fitting range

A

WNL in the lows (250-1) to severe (>1)
-10 to 70
minimal OE
output limited by receiver & concha size & depth in the canal

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134
Q

ITC fitting range

A

around 20 dB (WNL) to 500 Hz then mod severe
20-70
minimal PE
output limited the same as ITE

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135
Q

CIC fitting range

A

mild to mod severe
25-70
has PE
output is better due to depth of mic and receivers proximity to TM

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136
Q

IIC

A

mild to mod severe
best for LF HL
25-70
has PE
output increases up to 7dB if mic depth allows PE & up to 6 dB due to proximity to tm

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137
Q

what is a cros

A

Contralateral routing of sound
Single sided deafness - one ear is normal and poorer ear is unaidable

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138
Q

What is a bicros

A

Bilateral contralateral routing of sound
Bilateral asymmetric HL - one ear has threshold loss & poorer ear is unaidable

139
Q

for cros or bicros when the PT wears the devices will they get binaural hearing?

A

No because they still only have one ear and will not have spatial awareness

140
Q

what is ampcros

A

For asymmetric HL
bad and better ear
bad ear is not good for hearing aids (poor discrimination etc.) but not unaidable
fits two HA’s on the PT’s ear but in the two is a transmitter so you amplify both ears but then also routing the poor ear over to the other ear for extra boost of understanding

141
Q

adv and disadv of vinyl and when would it be used

A

used for infants, firm ears, high gain devices, facial flex issues, older adults w/ dexterity issues

adv- snug fit for high gain, easily modified, inexpensive to remake

dis - shrinks, hardens, discolors, requires replacement every 6-12 mos

142
Q

adv and disadv of silicone and when would it be used

A

used for peds, high gain devices, allergies, facial flex problems

adv - durable, doesn’t shrink, hypoallergenic for most

dis - sticky grip can cause blisters, hard to modify, costs more

143
Q

adv and disadv of lucite/acrylic and when would it be used

A

used for adults, mild to severe losses, floppy or soft pinnas

adv - no shrinkage, durable, discreet, easily modified, smooth surface for insertion and removal

disadv - increased risk of feedback w/ movement, potential injury if hit, harder to move beyond narrow/tortuous areas

144
Q

Understand the importance of the acoustic seal

A

Understand the importance of the acoustic seal
a tight acoustic seal reduces feedback

145
Q

full shell fitting range

A

used for higher output in severe to profound
70- >90
maximized retention & acoustic seal

146
Q

skeleton mold fitting range

A

mild to sev
25-90
subtle
maximized retention & acoustic seal

147
Q

canal mold fitting range

A

mild to sev
25-90
retention needs 2mm beyond 2nd bend
lowest degree of acoustic seal

148
Q

canal lock fitting rang

A

mild to sev
25-90
Adds projection into concha for improved retention by antitragus

149
Q

half shell fitting range

A

Mild to severe HL
-25 to 90 dB HL
Fills ½ of concha to improve retention & ease insert

150
Q

Describe the cause of the occlusion effect (OE) and associated patient complaints. Describe the degree of LF threshold loss associated with OE concerns
Describe two management techniques used to reduce OE

A

Skull transduces LF energy generated by your own voice and the signal becomes trapped in the ear canal
Increased perception of one’s own voice when something is blocking the ear canal
Common complaint occurs when LF threshold is better than 50 dB

Causes
Dome closes off the ear
Mold with too small of a vent
Insufficient venting and/or insufficient canal length

Vent size & stabalizing the device in the bony canal are two management techniques to reduce OE

151
Q

fitting range for open domes

A

</= 20 dB up to 1.5 kHz

152
Q

fitting range for closed dome

A

20-29 dB at 500 Hz
thresholds better than 40 below 1khz

153
Q

fitting range for power dome

A

30-39 at 500 Hz
thresholds better than 40 below 1kHz

154
Q

Name the primary frequency range impacted by the vent effect

A

primarily impacts frequencies below 1.5k Hz

155
Q

“direct signal“ and “amplified signal”

A

Direct Signal
Refers to unamplified signal arriving to the TM
Allows PT to hear LF signals & environmental sound naturally when LF thresholds are better than 40dB

156
Q

Direct Signal
Refers to unamplified signal arriving to the TM
Allows PT to hear LF signals & environmental sound naturally when LF thresholds are better than 40dB

A

the two combine being perceived as one signal arriving to the ™

157
Q

Amplified signal is 20 dB SPL louder than the natural direct signal

A

audibility of the amplified signal dominates

158
Q

If intensity of direct signal is louder than the amplified signal

A

direct signal will mask the amplified signal

159
Q

Describe the impact of standing waves occurring inside a vent

A

The final output and frequency response arriving to the TM may be unexpectedly altered when the direct signal moving inward is in-phase or out-of-phase with the amplified sound moving outward

in phase double the intensity
out of phase signals cancel portions out

160
Q

what is vent size needed for 50-60 dB at 500

A

.5 to no vent

161
Q

what is vent size needed for 40-49 dB at 500

A

1-2 mm

162
Q

what is vent size needed for 30-39dB at 500

A

2-3 mm or power

163
Q

what is vent size needed for 20-29 dB at 500

A

3-3.5mm or closed

164
Q

what is vent size needed for </= 20 dB at 500

A

open

165
Q

A change to the internal diameter will change the device output and frequency response

A

true

166
Q

smaller diameter of inner tube

A

more attenuation in high frequency signals

167
Q

Outer wall thickness increases to

A

reduce tube vibration
This reduces feedback in high gain devices

168
Q

tube lock is used

A

w/ silicone molds
brass grommet for friction in mold

169
Q

libby horn is used

A

as amp signal goes thru tube to horn you get a boost of amp in the high frequencies
increase output of highs by about 6dB
PT not ready for new ha and need a little more output in highs, create a mold with this to help some

170
Q

Continuous flow adapter (CFA) is used

A

for small canals that cannot accommodate standard tube sizes
Maintains internal diameter of sound bore bw a BTE & ear mold providing a continuous inner diameter & unimpeded flow of amplified sound

171
Q

Dry Tube is used

A

to reduce moisture buildup issues in tubinh

172
Q

Describe the impact of hardening tubes on the device’s frequency response output signal

A

Length shrinks
Displaces mold causing increased feedback

Hardens
HF gain reduces as inner diameter shrinks

173
Q

thin cement is used with

A

lucite/acrylic

174
Q

vinyl cement is used with

A

vinyl

175
Q

If HL 50dB or more in low frequencies you have to have a mold

A

true

176
Q

Describe the piezoelectric effect and the limits of piezoelectric microphones

A

twisting, compressing or distorting a thin electrified crystal creates a +/- electrical voltage required to make an analog electrical signal
This salt crystal replaced carbon balls in the mic for early electric HA’s
*this mic was short because it was affected by humidity and temps >110 deg F

177
Q

Compare & contrast Electret microphones and MEMS Microphone

A

electret - years of humidity, moisture, dirt, debris etc. degrades the mic & reduces sensitivity of the mic

MEMS - Stability: more stable
Silicone doesn’t absorb moisture
Has decreased battery drain in the device due to space being smaller bw diaphragm and backplate

178
Q

Define microphone sensitivity
What input frequency range can a microphone collect?

A

ability of the mic to pick up sounds
Sensitive collection from <100 Hz to as high as 15000 Hz

179
Q

Differentiate the causes of acoustic noise from the causes of electrical noise.

A

Acoustic - gasses & air flowing around us goes into sound port and moves the diaphragm
Electrical - comes from circuits in HA that are after the mic in ha

180
Q

What is an acceptable intensity of a mics internal noise floor?

A

~ 25 dB SPL

181
Q

What is the dynamic range of an analog hearing aid microphone? Of a digital hearing aid microphone?

A

Analog mic = 115 dB SPL (can collect input signals up to this before input distortion
Digital mic = ONLY 96 dB SPL (anything > results in input distortion)

182
Q

Define front-end distortion and its cause. Describe why digital HA’s have a lower mic dynamic range. Describe how front-end distortion is managed in digital hearing aids.

A

mic has a dynamic range and FED happens when the input signal exceeds this
Distortion in analog - input >/= 115 dB SPL (anything louder sounds distorted)
Distortion in digital mic happens with input >/= 96 dB SPL (0-96, anything louder sounds distorted)

Shift mic dynamic range by lifting the 96 higher to collect more loud sounds but does so by sacrificing soft
If we shift the range of mic in loud situations you can collect loud sounds without peak clipping but can’t collect soft
If we shift range in soft situations you can collect soft sounds but not loud ones anymore
Move form 16 bit to 19 bit HA in other digital devices allowing 108 dB dynamic range

183
Q

why digital hearing aids have a lower microphone dynamic range

A

due to analog to digital converter (ADC)
Used to transduce an analog electric signal to a digital signal
16 bit ADC supplies a 0-96 dB dynamic range and louder sounds are peak clipped

184
Q

Describe the impact of microphone distance on SNR

A

SNR becomes poorer as distance bw mic and desired signal increases

Further it is from the mic harder it is to hear over the noise because noise becomes louder - reduced SNR

Closer to the mic the louder it is over the noise - Improved SNR

185
Q

What is the ideal distance for sound collection?

A

Ideal mic sensitivity w/in 6 ft

186
Q

Which frequency range is associated with undesired background noise?

A

<1500 dB

187
Q

DI 0.0

A

omniDI

188
Q

DI 4.8

A

cartiod

189
Q

DI 5.7

A

Supercartiod

190
Q

DI 6

A

hypercartiod

191
Q

How does a directional mic use in-phase and out-of-phase signals to create a polar plot null

A

If acoustic signals arrive at the same time in phase, they move the diaphragm creating an analog electric signal
In phase = analog electric signal
If acoustic signals arrive at different times and out of phase they STOP diaphragm movement not creating an analog electric signal
Out-of-phase = STOP diaphragm and no analog electrical signal

192
Q

function of a directional microphone so you can explain how signals arriving from behind a patient are attenuated

A

Signals arriving from behind reach the two ports at different times creating an external time delay.
The delay causes out of phase signals that doesn’t allow the sounds to pass through and push on the diaphragm. This causes the sounds from behind to be attenuated

193
Q

Define directional mic roll-off. What causes it and how is it managed?

A

Happens when directional mics are turned on
because LF are broad and wide they are more likely to arrive out of phase causing them to be lost
results in 6dB/octabe LF roll off causing a reduction in volume

managed by equalization filters that add LF energy to replace the attenuated output signal

194
Q

Describe the importance of electret microphone matching and calibration

A

stop working when they fall out of calibration
has to be positioned parallel to the floor to keep the external time delay
If difference is greater than 1dB you lose directionality

195
Q

What causes reduced microphone drift?

A

Microphones that fall out of calibration over time
Occures due to:
High temps reducing mic sensitivity
Moisture causes damage to diaphragm tension ring
cerumen/debris clog mic port

When something plug the port, the sound coming in from the back doesn’t reach the diaphragm which doesn’t cause an out of phase signal which means no directionality occurs

196
Q

Describe the principle of induction

A

Telecoil uses this principle to transduce an electromagnetic signal to an analog electrical signal
Mic is turned off (NO ACOUSTIC SIGNAL)
takes electromagnetic signals and transduces it into an electrical sine wave
Electromagnetic signals move a magnet with a copper coil
This movement bw copper coil & magnet turns electromagnetic signals to a +/-analog electrical signal without adding an additional power source

197
Q

Benefits of telecoil

A

inexpensive
no external power source needed because magnetic field generates its own
no telephone feedback because mic is off
improved SNR on phone or in loop room

198
Q

pick-up room loop signals

A

vertical telecoil

199
Q

pick-up telephone signals

A

horizontal telecoil

200
Q

Engages AFTER volume control

A

Output compression (AGC-o)

201
Q

Engages BEFORE volume control

A

Input compression (AGC-i)

202
Q

what is threshold kneepoint

A

Changing from 1 compression ratio to another

203
Q

> /= 85dB SPL
Used to limit output of a HA so it doesn’t exceed the individual’s loudness discomfort levels & to maximize listening comfort

A

high TK

204
Q

</= 50dB SPL
Used to improve audibility of softer components of speech and/or
threshold that when amp reaches it compressor kicks in

A

low TK

205
Q

time it takes for level detector to identify input is loud enough to turn on and compress the signal

A

attack time

206
Q

shorter duration of overshoot & shorter period of time individual hears sounds louder than desired

A

faster AT

207
Q

Period of overamplification as input SPL increases above TK
Output signal overshoots targeted SPL

A

slow AT

208
Q

Amount of time for compressor level detector that the intensity fell below TK and needs to release the compression

A

release tie

209
Q

sudden loud sounds

A

fast attack

210
Q

best for conversational speech to maintain the shape of the spectral envelope

A

slow attack

211
Q

brief, intense sounds (door slamming)

A

fast release time

212
Q

longer intense sounds (such as a raised voice)

A

long release time to maintain a comfortable output level during brief gaps of silence

213
Q

How much compression to apply

A

compression ratio

214
Q

2.5:1 CR

A

For every 10 increase in input intensity, output increases by 4

215
Q

Presence of frequency components in HA’s output that were not present in the input signal

A

harmonic distortion

216
Q

shifting tk down

A

adds signal below TK

217
Q

increasing tk up

A

removes signal below TK

218
Q

Differentiate AGC-o from AGC-i

A

I - WDRC
b/w 20-50 dB SPL
Manages incoming sound
input compression

O- OLC
>/= 80dB SPL
manages loud sounds at output level

219
Q

good for those with lower cognitive capacity because temporal envelope is not compressed and looks more like what our brain stored of the sounds; while someone speaks, amp of temporal envelope shape is closer to auditory memory of signal for longer periods of time

A

slow compression

220
Q

gets compressed, work harder to match sound is sort of a memory to understand and causes more listening effort resulting; doesn’t take a lot of volume for it to compress & envelope doesn’t look like memory of it working harder to understand what was said

A

fast compression

221
Q

needed when someone complains about some of soft sounds they do not need to hear are too loud

A

expansion

222
Q

Lower output with very very soft sounds
really low CR (<.9:1)
0-20dB input

A

expansion

223
Q

needed to get soft sounds louder & expand dynamic range
manages incoming signal
Engages BEFORE volume control
input compression
activates at the pre-amplifier when TK is low input level & signal is louder than this (bw 20-50)
low TK
low CR (1.1:1-4:1)

A

WDRC

224
Q

need this to protect the ear
AGC-o
loud sounds
engages after vc
high tk (>80)
high CR (>/= 5:1)

A

output compression

225
Q

allows frequency specific compression of

A
226
Q

Frequency range is defined by the frequencies included in range based on dynamic range of loss
Frequency response is a series of volume controls called bands/handles

A

frequency shaping bands

227
Q

shape compression characteristics into individuals dynamic range to restore normal loudness growth
use these channels to squeeze gain for soft & loud into the persons dynamic range

A

compression shaping channels

228
Q

as input increases amount of gain applied is reduced

A

compression

229
Q

as input increases amount of gain applied is rapidly increasing too

A

expansion

230
Q

Very soft acoustic signals below the first threshold kneepoint (TK) are attenuated by applying

A

expansion

231
Q

Explain the process of converting:
An analog electrical signal to a digital signal
Include an explanation sampling rate, Nyquist frequency, quantization, quantization error, and processing speed
You should have an understanding of how each of these factors impacts the output signal
A digital signal back to electrical

A

Sound comes into mic (either in or out of phase; in goes on out is nulled), MEMS or ECM mic transduces acoustic signal by compressing and decompressing the diaphragm and the backplate creating the + and - analog electrical signal

NOW, sound leaves mic and goes through a bunch of circuits that either compress or amplify the signal
Signal is either amplified (transistor) or compressed (resistor) and is either routed to AGC-i or AGC-o

Then sound goes to the analog to digital converter to go from an analog electric signal to a digital signal
ADC - when converting an analog signal to a digital signal the signal is sampled at discrete intervals (sampling rate)

Digital signal now has numbers associated w/ it and moves to DSP

Moves to Receiver
converts amplified electric signal back to an acoustic signal

*acoustic signal, transduced to electric at mic, amp at different levels, electric changed to digital signal, algorithms added, digital converter back to electric analog signal that is amp, now to receiver to transduce back to acoustic signal

232
Q

number of times per second an analog signal is sampled to create a digital signal - how we capture frequency information

A

sampling rate

233
Q

more snapshots taken- the more accurate the original continuous wave is represented due to more sampling points

A

high sampling rate

234
Q

Nyquist theorem

A

Half of the sampling rate
If sampling ate is 20,000 Hz, nyquist frequency is 10,000 Hz

235
Q

more possible vertical amplitude values & more precisely the exact amplitude of a given sample can be recorded

A

higher bit depth

236
Q

Higher quantization = more fluid sample
Lower = more choppy sample
Rounds each snapshot to nearest fixed level

A

quantization (bit resolution)

237
Q

The difference between the original acoustic signal and the transduced digital signal

A

quantization error

238
Q

1 bit = front end DR by _____ dB

A

6

239
Q

16-bit digital word = DR of 96 dB
18-bit digital word = DR of 108 dB

A

quantization error

240
Q

Noise floor in the hearing aid is noise created in the circuit due to

A

quantization error

241
Q

Explain front end limitations associated with 16-bit processing, and how this impacts microphone sensitivities. How are these limitations resolved?

A

16-bit processing has a dynamic range of 96 dB - it can collect sounds up to this but past this the sound becomes distorted
We get this dynamic range because each digital bit increase the front end dynamic range by 6dB
Every bit only has 6 dB of dynamic range
Solution: the dynamic range shifts by lifting the 96 dB higher to collect more sound sounds but it does this by sacrificing soft sounds

242
Q

The function of auditory filters (critical bandwidths) in the cochlea (included number and size of filters

A

There are 25 bands that do this
Narrow LF bandwidths - only 160 Hz wide)
Wide HF bandwidths - up to 2.5 kHz wide)

Cochlea is a series of overlapping band pass filters (frequencies that are grouped together because they are close together on the cochela) that allow certain regions on it to stimulate to a specific frequency region while ignoring frequencies outside of the band

243
Q

The effect of low frequency masking on the damaged cochlea.

A

Broadening of the filters is mainly on the LF side, leading to the increasing of LF masking. So the LF noise masks the region it normally would but also spills over to the overlapping HF bands around it making it more difficult for the PT to use the cues to understand the speech over the noise

w/ HL, the curve is broader and noise can easily affect perception of the desired signal

244
Q

Frequencies impacted by noise

A

Noise energy peaks around 250 Hz but upward spread of masking impacts audibility up to about 1500 Hz

245
Q

what are methods of sound cleaning technology used in the spatial domain

A

automatic mic switching (fixed, adaptive, beamforming)

246
Q

ONLY thing we can do in digital ha tech to improve speech intelligibility is

A

enable direction mics

247
Q

fixed vs adaptive directional mic

A

fixed - one polar plot
adaptive - multiple polar plots

248
Q

superior when only a few noise sources are present

A

adaptive

249
Q

superior in the presence of multiple noise sources

A

fixed

250
Q

what is beamforming mic

A

Has a very narrow beamwidth (only azimuths of + 25°, + 35°, + 50°
Monitors overall intensity of environment
When signal is <55 SPL widest beamwidth activates
As environmental intensity increases (>75 SPL) smallest beamwidth is activated

251
Q

what are the methods of sound cleaning technology used in the temporal domain

A

modulation rate vs depth
digital noise reduction

252
Q

modulation rate vs depth

A

Speech = slow rate
Noise = fast rate

depth
Speech = highly variable
Noise = steady over time

253
Q

fast modulation rate & depth is stable over time =

A

noise

254
Q

Digital noise reduction: describe the attenuated signal
Describe the benefits and limitations of digital noise reduction

A

acts on steady state noises (idling engine, hair dryer, vacuum etc)

only acts on fast mod rate & low mod depth

doesn’t improve speech intelligibility

Can improve listening comfort, reduce listening effort, reduce cognitive load

255
Q

what are methods of sound cleaning technology in the spectral domain

A

HA here looks at a signal’s frequency to control the signal
Theory is that If noise is below 1.5 and then understanding speech comes from mid and high frequencies reducing the output in low frequencies will improve speech intelligibility in noise
if we attenuate and reduce lf amp and leave in hf, then we will probably improve speech intelligibility
not a lot of improvement by doing this
some noise is hf and not lf
ex: listen to music and speech is disruptive (talking in background) when you reduce lf then you take bass away but still hear person talking

256
Q

Explain Weiner filter function and limitations

A

Spectral subtraction approach, measures short term noise spectrum during gaps in speech

Works good on steady noise but not fluctuating so it is not effective in real time noisy situations
Reads between the lines in desired signal and takes out background noise found in the modulations of speech

257
Q

what are 3 methods to reduce external feedback

A

adaptive digital feedback suppression (DFS)

  1. reduce external feedback loop
  2. digital notch filtering
  3. digital feedback cancellation
258
Q

describe reducing external feedback loop for ADFS

A

Increase snugness of mold to reduce size of slit leaks
Or decrease vent size to stop feedback path
Limitation: both increases OE

259
Q

describe digital notch filtering in ADFS

A

Removes frequencies around the noise - reduces gain around 2-4 kHz where feedback occurs

Limitation 35% of intelligibility comes from this range alone so you stop feedback but stopped audibility of important speech sounds so reduced speech intelligibility

260
Q

describe digital feedback cancellation in ADFS

A

When HA detects feedback (identified due to steady state noise bw 2-4 kHz) an algorithm creates an out of phase clone of the signal (duplicate of the feedback) and this causes the clone to be subtracted from the amp path and in turn attenuates the feedback

261
Q

Describe the limitations of each feedback reduction method (DFS)

A

Algorithms can cause brief feedback until the out of phase tone can activate
Any sustained tone can start an algorithm (whistle, violin, etc.)
Audible beep when an external signal is mistaken for feedback - entrainment
Feedback cancellation can distort or attenuate parts of speech
Faster battery drainage and life

262
Q

what are 3 types of frequency lowering

A

linear frequency transposition
nonlinear frequency compression
spectral envelope warping

263
Q

when is freuqency lowering used

A

Only works from high to low
Best for steeply sloping HF HL
tries to improve HF audibility by shifting it down to LF
used with someone that has residual hearing and loss in HF makes it impossible to reach hf amplification (cannot get them to ever hear these sounds again)

264
Q

what is linear frequency transposition

A

CUT AND PASTE into LF, takes the highs and shoves it into the lows
Improves HF audibility by moving HF band one octave down to LF region

265
Q

what is nonlinear frequency compression

A

HF range is compressed into a LF range; squishes it down into the audible region
maintain tonotopic order more

266
Q

what is spectral envelope warping

A

Leave the HF where it is but also COPY and PASTE into LF
Keeping a portion in HF but also transposing portion down to LF range

267
Q

Describe digital wind noise reduction methods

A

Wind can increase output by 20-25 dB

Wind turbulence only affects one diaphragm so the HA talk to each ither and take the signal on the opposite side and transmit it and overlay it so it seems like the noise went away and improves snr in that environment

268
Q

benefits of wireless binaural processing technology

A

wind noise management
dual phone
volume control
program
WDRC

269
Q

how does wireless binaural processing support improved awareness of ILD in HA’s

A

As it arrives to second ear it is lower and wdr adds more gain on that same side so the ILD are gone so you cannot hear well in noise so binaural wireless the one ha tells that ha to not add as much wdrc
One ear will tell the other ear to not add as much wdrc so it doesn’t lose ILD

270
Q

automatically senses if it is noisy or not & decides if omni or directionality is needed

A

automatic mic switching

271
Q

adaptive vs fixed directional mic

A

Adaptive: null repositions itself (steer) to the loudest signal behind the person
Uses all the polar plots

Fixed: Picks a polar plot and stays using this position

272
Q

Which is better for high noise environments?

A

Fixed is better for more noises because it attenuates all the signals
Adaptive is better for a few noise sources because it is not smart enough to determine which ones to attenuate; it doesn’t know how to function

273
Q

Narrowband
Directional mic focuses in on a very narrow field (25-30 deg)
Good for talking with one person at a time and block out as much sound as possible
Can be to front, side (if driver in car), in back if you want to hear someone from behind

A

beamforming

274
Q

only circuit in HA that will improve this in noise

A

directional mic in the spatial domain

275
Q

After DSP, digital data stream is converted back to the analog electrical signal by

A

Converting from digital signal to analog electrical signal and goes directly to the receiver (less distortion, less noise, cleaner signal)
Or digital signal is converted to analog electrical signal that then gets amplified by an AGC-o (output amplifier to boost or add output compression) before entering the receiver

276
Q

Sets guidelines & standards for all diagnostic equipment and for instruments etc.

A

ANSI

277
Q

Compare results to standards of manufacturers and ANSI

A

SPEC sheet

278
Q

Acoustic chamber
Reduces reflections
Low ambient room noise
Calibrated sound sourcc

A

test box

279
Q

Emit measurement signal

A

speakers

280
Q

Calibrates SPL output from speakers

A

reference micc

281
Q

Measurement mic collecting output from the HA

A

coupler mic

282
Q

Simulates size of the canal
Custom products - ITE & ITC
Uses fun tak to attach HA to it

A

HA-1 coupler

283
Q

Traditional BTE w/ earhook
Attach directly to hook

A

HA-2 Coupler

284
Q

Only for verifit 2
Used for CIC, IIC, RIC
Smaller cavity volume mimics the deeper placement of the device
Realistic picture of frequency response in >HFs
ANSI requires use of same coupler used by manufacturer

A

.4cc wideband coupler

285
Q

Better simulates characteristics of the ear canal
Avg canal has HF SPL that is higher than the LF SPL

A

zwislocki coupler

286
Q

This shows output for a 90dB SPL input signal (MPO)
Loudest possible output point device can produce for a 90 dB input signal & represents a single frequency

A

OSPL 90- Output SPL @ 90 dB

287
Q

Calculates the average OSPL 90 output for 1, 1.6 and 2.5 kHz
*3 triangles at the bottom
Useful to tell what the max output of HA is and whether it will get too loud for the PT

A

HFA OSPL 90- HF Avg output SPL @ 90dB

288
Q

Shows avg gain for 1, 1.6, 2.5 for a 50 dB signal
Estimates the max gain available at different frequencies when an avg input signal is amplified

A

HFA FOG - HF avg full-on gain

289
Q

Measures the internal noise of the HA
Typically 25- 30 dB SPL is acceptable

A

equivalent input noise (EIN)

290
Q

Measures signal distortion
Determines if output signal contains harmonic frequencies that were not present in the input signal

A

total harmonic distortion

291
Q

Should be below 5-10%
High DL are indicators the device is close to failing (most likely the receiver) & needs sent in for a repair

A

% THD

292
Q

3 steps for looking at ansi measurements

A

step one: look at manufacturer value on spec sheet
step two: look at summary of tolerances
step 3: look at data point; is it in or out of spec

293
Q

what is emitted from the T in the test box

A

electromagnetic signal

294
Q

what is SPLITS & RSETS
what is SPLIV & RTSLP
How are they different

A

SPLITS - measured output response of the HA w/ electromagnetic signal
RSETS - calculates the difference between the mic output and the telecoil output (SPLITS)

+ RSETS = telecoil output it louder than the mic output
PT will turn HA down when telecoil is on
- RSETS = telecoil ouput is softer than the mic output
PT will turn HA up when telecoil is on

SPLIV
SPL in a vertical magnetic field
Looped environment
RSLS - relative simulation for loop sensitivity
SPLIV - output of telecoil
RTLS - difference bw mic and telecoil

295
Q

what if SPLITS is larger than SPLIV

A

telecoil is more sensitive in the horizontal position

296
Q

what if the SPLIV is higher than the SPLITs

A

telecoil is more sensitive in the vertal position

297
Q

output of the telecoil

A

SPLITS

298
Q

difference bw mic and telecoil output

A

RSETS

299
Q

+ RSETS

A

tcoil output is louder than the mic output

300
Q
  • RSETS
A

telecoil output is softer than the mic output

301
Q

first limitation to frequency response of HA

A

sampling rate
ADC sampling rate determines the highest frequency a device can produce

302
Q

dynamic range of mic is impacted by

A

bit rate of an ADC converter

303
Q

Describe the purpose and function of a receiver

A

converts amplified electric signal back to an acoustic signal

armature (flexible strip of metal balanced between two magnets like a diving board) is magnetized as the electrical current flows through the coil and it moves up in the positive direction towards that magnetic and down to the negative magnetic mimicking the electrical sine wave which is attached to the diaphragm above it and as the armature moves so does the diaphragm and this diaphragm movement causes the push and pull of the air creating an acoustic signal

304
Q

How are receivers designed differently to achieve the greatest high frequency output for severe hearing losses

A

Receiver sizes determine the final HF output
HF signals need rapid diaphragm movements
This is done w/ smaller receiver because it makes the diaphragm smaller and stiffer

305
Q

Smaller contemporary receivers are capable of

A

higher frequency responses
as high as 10-12 kHz

306
Q

Trying to achieve HF in large receivers compromises LF gain that is needed for severe HL

A

true

307
Q

what are dual receivers (two receiver system)

A

Output from both receivers added together when it reaches the ™
One is for LF
One is for HF

2 receiver system that sums both receivers before reaching the ™ where one is optimized for LF and the other HF which reduces battery drain, gives a good EHF output w/out compromising a lot in LF and minimizes saturation distortion potential

Benefit:
Extended HF bandwidth in moderately high output receiver without compromising the LF

308
Q

This happens when the receiver output is reached resulting in peak clipping or the receiver having a higher voltage and battery drain
HA output range has been exceeded leading to distortion due to peak clipping

A

Receiver Saturation

309
Q

Caused by a dislodged receiver where the vibration goes back into the mic adding extra frequencies to the input signal leading to distortion

A

shock damage

310
Q

Can block the receiver diaphragm and cause reduced output of the receiver

A

cerumen/moisture/debris

311
Q

Define soundbore path

A

A column of air that sound waves pass through leaving a receiver that arrives to the ™

312
Q

Final output & bandwidth (frequency response) of device changes based on a sound bore paths acoustic parameters/physical properties

A

true

313
Q

RIC devices also have a sound bore path

A

false

314
Q

What frequency range is impacted by changes to the sound bore

A

Sound bore flaring
HF output is changed based on the side of the flare
Increases HF depending on length and size of the flare

Thin tube
Making the tube thinner decrease the HF output & shifts the peak resonance down to lower frequencies (1000 hz down to 800)

315
Q

Describe the impact of standing waves within the soundbore on the final output signal

A

This happens when reflection in the sound bore causes the wave to overlap with itself
This causes two waves of the same frequency to either be in phase creating a single sound that is louder or two identical waves 180 deg out of phase and cancel each other out

316
Q

Smaller internal diameters of a thin tube cause reduction in

A

HFO & shifts tube resonance down to around 800 Hz

317
Q

libby horn
internal horn shape

A

increases HFO

318
Q

what is an issue with libby horn

A

benefit depends on maintaining length of flare canal
cannot just be a flare has to have a certain length
cannot always get diameter or length to fit into individual horn

319
Q

Depth of soundbore in canal

A

Increased length = Increased SPL for ALL frequencies

320
Q

Describe the purpose and limitation of a damper

A

Acoustic resistor
Physical barrier to reduce sound
Smooths the resonances in the final frequency response
Does so by attenuating sounds slightly to smooth the peaks
Sound waves lose energy as they travel through the damped material

321
Q

Higher ohm = more resistance

A

true

322
Q

if a damper is replaced, any color can be put in

A

false
must be the same color

323
Q

Course
Used to modify silicone
Need to use at least 25k to 20k RPM for best results

A

blue stone

324
Q

For grinding acrylic or vinyl
Smaller one is for smaller areas

A

white stones

325
Q

Removes large amounts of material fast

A

low grit

326
Q

Smooths and restores shine
Only used w/ lucite/acrylic molds

A

fine grit

327
Q

Removes less material and smoother finish

A

medium grit

328
Q

Final edge smoothing

A

nail file

329
Q

pros of rechargeable batteries vs disposable

A

Rechargeable
Convenience
No small batteries
No keeping track of batteries
More eco friendly
No buying batteries

Disposable
Convenience
Smaller HA size
Lower HA cost
Better reliability

330
Q

what is the purpose of a listening check

A

subjective eval of HA, will only pick up significant device malfunction, should perform electroacoustic measure to compare to manufacturer specifications
Listening for unusual distorted bad sounds
Is it linear or nonlinear
Is it directional or omni

331
Q

Hold the device _____ from sound source

A

~12”

332
Q

linear ha

A

If there is no change in amplitude from soft to loud

333
Q

nonlinear ha

A

Amplitude is louder for soft and softer for loud

334
Q

directional mic

A

If you turn HA 360 deg and sound attenuates behind HA

335
Q

omnidirectional

A

If you turn HA 360 deg and it doesn’t attenuate from behind

336
Q

what are the 6 ling sounds? why are these used

A

“ah”, “ee”, “oo”, “sh”, “ss”, “mm”
Used to test across a frequency range

337
Q

what is SBAR communication method to relay a call for action to another healthcare provider

A

Get to the point asap
Situation: brief statement of the problem you are facing
Background: follow up with pertinent case details
Assessment: statement of concern
Recommendation/request: what are you asking of them

338
Q

what is patient centered care

A

Active involvement from PTs and their families to design new care models in decision making about their options for treatment
Takes time & dont get reimbursed but we can for other services - need to bill & code effectively to be reimbursed for services we do provide

339
Q

when will medicare reimburse

A

Evaluation of the cause of disorders of hearing, tinnitus, or balance;
Evaluation of suspected change in hearing, tinnitus, or balance;
Determination of the effect of medication, surgery, or other treatment;
Reevaluation to follow up regarding changes in hearing, tinnitus, or balance that may be caused by established diagnoses that place the patient at probable risk for a change in status, including but not limited to otosclerosis, atelectatic tympanic membrane, tympanosclerosis, cholesteatoma, resolving middle ear infection, Meniére’s disease, sudden idiopathic sensorineural hearing loss, autoimmune inner ear disease, acoustic neuroma, demyelinating diseases, ototoxicity secondary to medications, or genetic vascular and viral conditions;
Failure of a screening test (although the screening test is not covered);
Diagnostic analysis of cochlear or brainstem implant and programming;
Audiologic diagnostic tests before and periodically after implantation of auditory prosthetic devices.

340
Q

will medicare reimburse?

Evaluation of the cause of disorders of hearing, tinnitus, or balance;
Evaluation of suspected change in hearing, tinnitus, or balance;
Determination of the effect of medication, surgery, or other treatment;
Reevaluation to follow up regarding changes in hearing, tinnitus, or balance that may be caused by established diagnoses that place the patient at probable risk for a change in status, including but not limited to otosclerosis, atelectatic tympanic membrane, tympanosclerosis, cholesteatoma, resolving middle ear infection, Meniére’s disease, sudden idiopathic sensorineural hearing loss, autoimmune inner ear disease, acoustic neuroma, demyelinating diseases, ototoxicity secondary to medications, or genetic vascular and viral conditions;
Failure of a screening test (although the screening test is not covered);
Diagnostic analysis of cochlear or brainstem implant and programming;
Audiologic diagnostic tests before and periodically after implantation of auditory prosthetic devices.

A

yes

341
Q

when will medicare not reimburse

A

When the auditory/balance status is already known
When the reason for the hearing assessment is unrelated to hearing aids, or examinations for the purpose of prescribing, fitting, or modifying hearing aids

342
Q

will medicare reimburse?

When the auditory/balance status is already known
When the reason for the hearing assessment is unrelated to hearing aids, or examinations for the purpose of prescribing, fitting, or modifying hearing aids

A

no

343
Q

what are CPT codes

A

codes used to describe primary diagnostic procedures done

344
Q

what are ICD-10 Codes

A

codes used to classify a diagnosis or symptom

345
Q

what are hcpcs

A

codes describing services & supplies that are not defined or outlined in CPT codes

346
Q

can you code for doing a hearing check and repair? if so what are the codes

A

yes
**look up

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