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CDAP 350 Audiology > Perscriptive Formulas, Compression And Hearing Software > Flashcards

Perscriptive Formulas, Compression And Hearing Software Flashcards

1
Q

What are the four challenges regarding knowing how much volume is needed?

A
  1. The preferred amount of volume received depends on input volume
  2. Preferred volume depends on suprathreshold loudness perception and frequency resolution
  3. Preferred volume may depend on how they currently “hear”
  4. How important the input signal may determine preferred volume
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2
Q

What are the suprathreshold based prescriptions

A

SHAPIRO
CID (central institute for the deaf)
LGOB (loudness growth in half octave bands)
IHAFF/contour (independent hearing aid fitting formula)
ScalAdapt
DSL I/o (desired sensation level)

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3
Q

What Re the threshold based formulas

A 
NAL (national acoustic laboratories) 
Berger
POGO (prescription of gain and output) 
FIG6
CAMREST
DSLm i/o
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4
Q

What does the “target” do

A

Allows you to manipulate the gain of the hearing instrument to achieve the formulas

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5
Q

What predicts where the targets fall on the graph

A
  1. Severity of the hearing loss
  2. Specific formulas used
  3. Monaura or binaural fitting
  4. Conductive component
  5. Child or adult
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6
Q

What do the targets represent

A

Where the average individual with a specific hearing loss needs the volume of their hearing aids to achieve a specific formula

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7
Q

Why would you aim for above target?

A

If they are long term users
If they have a more severe hearing loss
Conductive component

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8
Q

Why would you aim for below target?

A

If they have had extended auditory deprivation

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9
Q

What does the prescriptive formula do?

A

Gives us a way to determine how much volume an individual needs for their hearing loss

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10
Q

What is the goal from the NAL, NL2, and NL1`

A

Goal of the non linear prescription is to maximize speech intelligibility at a volume comparable to what someone with normal hearing would need

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11
Q

How does the NAL achieve the goal

A

they determine how various hearing losses impact speech intelligibility and the perception of loudness

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12
Q

What is the goal of the DSL

A

Goal of this prescription is to normalize loudness

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13
Q

How does the DSL achieve their goal

A

all sounds would be the same for hearing impaired individuals as it would be for someone with normal hearing

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14
Q

What are the stages in the DSL m[i/o]

A
  1. Expansion
  2. Linear amplification
  3. Compression
  4. Output limiting
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15
Q

Who typically prefers the NAL vs the DSL

A

NAL - Adults

DSL - pediatrics

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16
Q

Is the DSL adult better for an adult with congenital hearing loss than another?

A

Nope

17
Q

What are the four issues with prescriptive formulas and expand

A
  1. Acclimatization
    - the more severe the loss and the longer they have gone through auditory deprivation acclimatizing to their HA volume is harder
  2. Preferred loudness levels
    - different people with the same loss have different preferred levels
  3. Dead regions
    - inner hari cells in cochlea stop functioning: amplify one octave higher in the dead region is appropriate
  4. Severe to profound high frequency losses
    - excessive high frequency information may lead to reduction in speech intelligibility
18
Q

Additional considerations for unilateral hearing loss

A

If a hearing loss in both ears but only wears one hearing aid you can increase formula by 3db (this is where we can perceptually hear a difference)

19
Q

Additional considerations for infants and young children

A

More volume than adults with similar losses because thy are developing and learning

20
Q

Additional considerations for conductive and mixed hearing losses

A

They have an attenuation of sound in their middle ear cavity
Many prescriptions add gain to overcome the conductive component
“Power junkies” they like the volume higher then clinicians would like

21
Q

What is the dynamic range

A

Range of sounds a given individual can hear
Cannot hear very soft sounds
Tolerance for loud sounds doesn’t change

22
Q

What is compression used for

A

To increase intelligibility we need to increase volume of softer sounds without overamplifying medium and loud sounds

Allows you to take a wide range of input volume and place these sounds comfortably into a smaller range

23
Q

Define input

A

Refers to the acoustic signal entering the microphone of the hearing instrument

24
Q

Define output

A

Refers to the amplified signal the ear receives

25
Q

Define gain

A

The difference between the input and output

26
Q

Define input/output graphs

A

Graphical representation of a hearing instruments output at various input levels

27
Q

Define compression

A

The output range is smaller than the input range

28
Q

What is the compression threshold

A

The input level at which the compressor switches from linear amplification to non linear amplification

29
Q

Define compression ratio

A

Determined by dividing the difference in input by the difference in output

30
Q

What is non linear amplification

A

Occurs when the difference between the input and output is not 1:1
Represented by a compression ratio I/O

31
Q

What is wide dynamic range

A

It’s the most common form of compression

This is he gradual application of compression over a wide range of input signals

32
Q

What do the attack and release times do

A

Protect against abrupt input changes

33
Q

Define attack time

A

Time it takes compression to kick in

34
Q

Define release time

A

Time it takes compression to turn off

35
Q

How fast is fast release time

A

Can be (5ms/100ms)

36
Q

How fast is slow attack and release time

A

(20ms/2s)

37
Q

How compression is applicable …..

A

1 avoids distortion

  1. Optimizes the residual dynamic range and restore normal loudness perception
  2. Maintain listening comfort
  3. Maximize speech intelligibility
  4. Reduce noise

CDAP 350 Audiology (4 decks)

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