Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Amplification II > 5 - Digital Technology > Flashcards

5 - Digital Technology Flashcards

1
Q

What are three types of HAs?

A

1) analog
2) programmable (digitally controlled analog)
3) digital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are 3 components of analog HAs?

A

1) The electrical voltage is analogous to the acoustic signal
2) Analog HA are now obsolete
3) Processing was 1:1 up to the output limit of the hearing aid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are 2 components of programmable HAs?

A

1) Programming is performed through digital technology but signal processing remains analog
2) Also obsolete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are 2 components of digital HAs?

A

1) Digital processing of signals
2) Classified as entry, intermediate, and advanced levels depending on features available.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does processing happen in analog HAs?

A

Mic—amplifier—receiver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does processing happen in digital HAs?

A

Mic—preamp—LP filter—digital conversion—digital signal processing—analog conversion—LP filter—receiver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does a HA process sound?

A
  • Sound: condensations and rarefactions of air (particles moving back and forth over time)
  • HAs break up this continuous information, break it down, store it, and put it back together
  • HAs are recording this, and reproduce after the signal has been manipulated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 4 steps of how digital HAs process sound?

A

1) Mic picks up signal and converts it into electrical energy
2) Analog to Digital Conversion (ADC or A/D)
3) Digitized numerical codes are assigned binary digits (bits) or “0” and “1”.
- Signal processing occurs through manipulation of these digits
4) Digital to Analog Conversion (DAC or D/A)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How can a HA represent sound well?

A
  • There has to be enough samples to accurately represent the information
  • Specifically, we must consider the NYQUIST theorem.
    • We need at least double the sampling points as the highest frequency we want to represent.
    • The Nyquist FREQUENCY is half the sampling rate.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the aliasing error?

A

When the input frequency is greater than the Nyquist frequency, a “new” sine wave, not present in the original signal, is created
- aliasing signal
- distortion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a visual example of the aliasing error?

A

Visual example: car wheels that appear to turn backwards in movies
- Camera samples the movement at specific times
- The wheel turns faster than the sampling frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are HAs understanding sound?

A

HAs understand sounds as discrete points of information

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What if there aren’t enough sound points to represent the sine wave?

A
  • If not enough points to represent the sine wave, it will fill in the blanks
  • If we don’t have a good signal understanding on the input, the output cannot be beneficial and accurate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Analog to digital conversion - how do you avoid aliasing in HAs?

A
  • Problem of aliasing if input signal contains frequencies above the Nyquist frequency.
  • Low-pass filter (anti-aliasing filter) rejects the frequencies higher than the Nyquist prior to A/D conversion.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where does the anti-aliasing filter happen in digital HAs?

A

Anti-aliasing happens before the digital conversion of the signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are BITS?

A
  • Not using a “standard” 10 base number system
  • HAs are using Binary digits (BITS) 1 or 0
  • It’s as easy (or as complex) as 0 1, 1 0, 1 1
  • Basically, we can represent EXPONENTIAL AMOUNTS OF INFO!
17
Q

Why do HAs want more BITS?

A

More BITS, smaller error, more dynamic range!

18
Q

How many BITS does a HA generally use?

A
  • HAs generally use 12 to 24 bit processing—-16 bits usually… or higher
  • 16 bit: can represent a wide range of frequencies (speech frequencies and a good representation of DR)
19
Q

Each BIT has a ____dB dynamic range

A

6 dB

20
Q

16-bit A/D converter has a dynamic range of ____dB.

A

96 dB

21
Q

What do HAs need a lot of processing for?

A

Need a lot of processing to represent music well in a HA

22
Q

What happens to very loud inputs in a HA?

A
  • Inputs that exceed the upper limit of the A/D converter’s dynamic range will be peak clipped, or HA uses compression to reduce input level before processing.
  • A distorted signal at the front-end cannot be improved at a later stage.
23
Q

What happens when speech is in very loud noisy backgrounds?

A
  • Both speech and noise are distorted!
  • We need the processing on the front end so the HA can manage delivery and noise
24
Q

What are the 3 steps of digital to analog conversion?

A

1) Numerical format is converted back into an analog signal.
2) Through this process, some unwanted noise (images) is created.
3) An anti-imaging filter (low pass filter) rejects the noise.

25
Q

Where does the anti-imaging filter happen in digital HAs?

A

An anti-imaging filter is on the back end (the anti-aliasing is on the front end

26
Q

What is the processing delay?

A

Digital processing takes time: analog sound is sampled, converted to digital info which is then manipulated, and then re-converted into analog signal.

27
Q

How long does the processing delay take?

A

1) Complex processing takes longer.
2) Delay is about 5-6 ms in many HA.
3) Ideally 1 or 2 ms (the shorter the better).
4) Problematic if 10-15 ms or longer (this is when patients perceive sound quality issues).

28
Q

Processing delay (echo effect) may be perceived by people with what 3 things?

A

1) Normal hearing in one ear and a unilateral fit on the poor ear.
2) Open fittings: sound also enters the ear naturally.
3) Bilateral fittings: processing delay may cause the lip movements to be out of sync with the signal heard.

29
Q

When trying to match targets, what 2 problems can occur if your test input is not speech or speech-like?

A

1) Digital noise reduction system can interpret the test signal as noise and reduce the gain.
2) Feedback cancellation feature of HA may think that test signal is feedback.

30
Q

What 3 ways do we mitigate the problems that can occur if your test input isn’t speech or speech-like?

A
  • Some manufacturers have a “verification setting” in the software that turns off noise reduction features for REMs
  • We use speech input (e.g., “carrot passage”, or the ISTS signal)
  • If you only have access to a sweep or composite noise test input, deactivate the automatic features (e.g., noise reduction) before real- ear verification of targets.
31
Q

How do entry level HAs differ from high end HAs?

A
  • Entry and high-end HAs have the same processor
  • Compared to entry level HAs, high-end HAs generally have:
    • More activated features
    • In entry level HAs, several of the features are disabled within the firmware (not visible to the audiologist)
    • More bands/channels for frequency shaping and for signal processing (e.g., noise reduction algorithm)
    • More automatic programs
32
Q

What are the 3 values of having more bands or channels?

A

1) Greater fitting precision for frequency shaping (gain and MPO)
2) Better control of compression parameters
3) Better signal processing performance (e.g., noise reduction, feedback management)

33
Q

Is more channels better, e.g., is a 20-channel HA better than an 8-channel HA?

A
  • Manufacturers, and many audiologists, seem to believe that more is better
  • However, with at least 6 channels of processing, your patient should do well with the HA
34
Q

Who does the number of channels effect?

A
  • Even if the patients select the most premium devices, if we don’t verify targets and meet their audibility, we aren’t providing them with effects of the premium HAs
  • The number of channels make a difference for us as audiologists, not the patients
35
Q

What 3 things does having more channels mean (cons)?

A

1) Increase in processing load and group delay
2) Increased battery consumption
3) Higher HA cost

36
Q

How many channels does an entry level and premium level HA have?

A
  • Entry level = 6 channels
  • Premium level = 20-25 channels
37
Q

Is advanced level better than entry level?

A
  • Results showed no difference between technology levels for improvements in speech perception and quality of life.
  • Participants did not report better outcomes with advanced technology HAs for any of the measures
38
Q

What did the study find that advanced HAs did better than entry level?

A

Entry and advanced HA had similar performance except that advanced level HA performed better for localization of HF stimuli in the quiet condition.

39
Q

Is newly launched technology really better?

A
  • Usually lots of hype when a new product or feature is introduced.
  • New products are typically launched by the manufacturer at a major conference (e.g., CAA or AAA conference).
  • Manufacturer may have “evidence” to support the new feature, e.g., “in clinical trials, X number of users preferred this new technology”.
  • How strong is this evidence? Is it real evidence or is it the placebo effect? Yes (only 2% preferred)

Amplification II (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions