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Amplification II > 8 - Signal Processing > Flashcards

8 - Signal Processing Flashcards

1
Q

When is reaching targets problematic?

A

Steeply sloping losses

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2
Q

What are 3 reasons why steeply sloping losses are problematic?

A

1) Achieving target gain does not make speech intelligibility better
2) Achieving target gain does not actually lead to audibility
3) Achieving gain leads to audible feedback

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3
Q

What is the problem with this picture?

A
  • Patient isn’t hearing those gain targets in the high frequencies
  • Clarity of speech, high frequency consonants, /s/, plurals
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4
Q

What is frequency lowering?

A
  • Bring the high frequencies (speech signals preferably, and environmental sounds) to a lower frequency region so that they can be audible
  • Shift the higher frequencies into a lower frequency range that is audible for the patient
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5
Q

Frequency lowering is ____ distortion

A

deliberate (we know the signal will be distorted)

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6
Q

What are the 3 types of frequency lowering used by manufacturers?

A

1) Frequency compression
2) Frequency transposition
3) Frequency translation (high frequency “reinforcement”)

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7
Q

What does frequency lowering do exactly?

A

Addresses dead regions in the cochlea

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8
Q

Hearing loss = ____ and ____ damage

A

OHC, IHC

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9
Q

Damage to OHC results in hearing loss up to ____ or ____

A

~50 dB HL (low frequencies), ~65 dB HL (high frequencies)

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10
Q

For loss greater than ____dB HL, there is likely also IHC damage

A

60-70

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11
Q

What is a cochlear dead region?

A
  • A region in the cochlea where IHC are damaged, but a tone that produces peak vibration of the basilar membrane in that region will be detected at an adjacent location (if the vibration is great enough)
  • IHC immediately adjacent to the dead region pick up the tone
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12
Q

What is used to diagnose dead regions?

A
  • TEN test (Threshold-Equalizing Noise) may be used to diagnose dead region
  • Measuring pure tone thresholds in TEN (threshold equalizing noise) masked noise
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13
Q

Where are dead regions most common?

A

More common in high frequencies than low frequencies

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14
Q

What does the prevalence of dead regions increase with?

A

Increasing degree of hearing loss

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15
Q

Prevalence of dead region at 4000 Hz is more than 50% when hearing thresholds exceed ____

A

70 dB HL

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16
Q

What 5 things does providing amplification to a dead region NOT do?

A

1) may not restore audibility
2) may not lead to better intelligibility
3) may not lead to ideal listening experience
4) make speech intelligibility worse
5) affect the potential for feedback

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17
Q

What 2 reasons are frequency lowering technologies recommended?

A

1) Dead regions
2) When high frequency targets cannot feasibly be met

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18
Q

What might patients with cochlear dead regions complain of?

A
  • They aren’t hearing things well
  • Things are mumbled
  • Subtle differences in high frequencies
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19
Q

What are the 4 steps of verifying frequency lowering?

A

1) Conduct speech mapping as per standard guidelines with no active frequency lowering, with a full spectrum reference (speech), with patient thresholds present
2) Play high frequency filtered stimuli, or /s/ stimulus at 65 dB SPL (make sure noise reduction is off)
3) Does /s/ appear to be audible for the patient?
- If yes, frequency lowering may not be needed
- If no, frequency lowering may be warranted
Activate frequency lowering, replay the /s/ signal at 65 dB SPL
4) Have you observed a shift for improved audibility?

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20
Q

Frequency lowering: before and after (picture)

A
  • /s/ not audible before frequency lowering
  • /s/ is audible after frequency lowering
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21
Q

How does the frequency lowering technique; transposition work?

A
  • High frequencies are “cut and pasted” to a lower frequency region; high frequency band eliminated
  • The HA is making an assumption that at a particular area, there is going to be a region that is unaudible
  • The HA will take the peak that was there and cut and paste it into a lower region of the audible spectrum
  • Now we have frequencies that are stacked on top of one another
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22
Q

Who would do good with transposition and who would do poorly?

A

Good:
- This requires really good central auditory functioning so the patient’s brain can sort it out for distinction and meaning

Poor:
- APD and cognitive impairments won’t do as good with this

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23
Q

What is the benefit of transposition?

A

Giving accessibility (access to information they otherwise wouldn’t have access to)

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24
Q

How do you verify transposition? (picture)

A
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25
Q

How does the frequency lowering technique; frequency compression work? What are we reducing?

A
  • High frequencies are “squeezed” to a lower frequency region, reducing the bandwidth and spectral details
  • We are distorting the signal of the patient to give them access to these cues
  • Other high frequency cues can be affected by this (can create some distortion for the patient)
  • Processing has to be good in order to make good use of this
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26
Q

Frequency compression has a ____ and ____ associated with it.

A

CT, CR

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27
Q

What is the lower cutoff and upper cutoff indicating?

A
  • The lower cut off = the first region is a conditional compression (the HA will be monitoring)
  • The upper cut off = maximum audible bandwidth, maximum point of applying gain to the frequencies, always in compression
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28
Q

When we are moving towards audibility, we are…

A

…moving frequencies into a lower range

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29
Q

When we are moving towards distinction, we are…

A

…keeping frequency lowering to a minimum

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30
Q

Who is frequency lowering best for?

A

This is best for adults with an acquired hearing loss (getting the distinction of the /s/ back)

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31
Q

How does the frequency lowering technique; frequency translation work?

A
  • High frequencies are not lowered.
  • Instead, the hearing aid first identifies if high frequency energy is present (in a region that is probably not audible to a patient); if so, it replicates the envelope at a harmonically related lower frequency (where it is audible to a patient)
  • 2 humps = 2 bands of energy that have been replicated
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32
Q

What is another name for frequency translation?

A

High frequency reinforcement

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33
Q

What manufacturers use the frequency lowering strategy of compression?

A
  • Phonak: SoundRecover 2
  • Unitron: Frequency Compression 2
  • Signia/Sivantos: Frequency Compression
  • Resound: Sound Shaper
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34
Q

What manufacturers use the frequency lowering strategy of transposition?

A
  • Widex: Enhanced Audibility Extender
  • Oticon: Speech Rescue
  • Bernafon: Frequency Composition
35
Q

What manufacturers use the frequency lowering strategy of translation?

A

Starkey: Spectral IQ

36
Q

What can too much frequency lowering do? Tradeoff between what 2 things?

A
  • Keep in mind that the use of frequency lowering strategies is a deliberate distortion of the signal being delivered.
    -Tradeoff between improved audibility of high frequencies vs increased perceived distortion
  • Generally, excessive amounts of frequency lowering should be avoided- use the minimal amount to get the desired effect!
37
Q

What 4 people need frequency lowering?

A

1) Some manufacturers say “use it for everyone!”
2) Suitable for people with cochlear dead regions or severe sloping high frequency loss when targets are hard to match
4) Some research show improvement in speech production skills of children if sounds are made audible, but distinction is important and should be maintained ideally
5) Also, works well for solving feedback issues (without plugging up a vent or drastically changing the acoustics)

38
Q

If a patient has no residual hearing above 3000Hz, is meeting gain above 3000Hz any benefit to the patient?

A

No

39
Q

S-REM with and without frequency lowering. What is happening in this picture?

A
  • Bringing the gain a bit further in with frequency lowering
  • Check in with patients and see if they are getting the high frequency stimuli
40
Q

____ has a more narrow frequency band than ____

A

/s/, /sh/

41
Q

What are the 5 steps in verification with verefit 2?

A

1) First fit to target with frequency lowering “off”
2) Check audibility of “s” on Verifit2.
3) Activate frequency lowering
4) Re-verify with frequency lowering “on”.
- Is “s” audible with frequency lowering activated?
5) Can the patient distinguish high frequency information /s/ or /sh/?
- Can use a word list with your mouth covered

42
Q

How do you counsel patients on frequency lowering? What do you set to?

A
  • Counsel patients about adjustment period, particularly if frequency lowering is new to the patient (may need a couple of weeks to adjust)
  • Set to the highest cut-off frequency (higher kneepoint), and smallest frequency compression ratio, at which the person can detect and discriminate /sh/ and /s/.
43
Q

What is in-situ audiometry?

A
  • Manufacturers offering “In-Situ” hearing testing are offering a pure tone hearing test performed through the hearing aids themselves while they are connected to the software either in office or during a remote session
  • Tones are presented through the hearing aids, and patients respond using an ascending method
  • The audiologist can choose to use that information to recalculate the fitting, or disregard
  • This test is being done through the manufacturer’s software
  • Available on many hearing aids (e.g., Widex “Sensogram” or Phonak “Audiogram Direct”)
  • In-situ thresholds may take into account (i.e coupling details)
  • Acoustics and ambient noise level in the room are very important (not in a sound booth, in an office)
  • Does not replace booth testing
44
Q

How valid is in-situ testing?

A
  • Some studies have suggested a high level of correlation between standard audiometry and insitu audiometry (thresholds within 15 dBHL), suggesting this could be a fast and accurate check of pure- tone audiometry thresholds
  • Potentially useful in determining if there may be a change in hearing requiring further evaluation (a full audiological assessment).
  • Does not replace booth testing as it does not account for BC testing, or speech testing
  • Other limitations includes FB testing, MPO adjustment, and REMs
45
Q

When and where is in-situ testing important?

A
  • When: COVID
  • Where: long-term care facilities
46
Q

How is speech generated?

A
  • Speech is generated from the vocal tract, inclusive to oral cavities, nasal cavities, and with the use of articulators (tongue, palate, lips)
  • These factors, even in different languages, have limitations
  • This consistency has allowed hearing aids to be able to process that information well
47
Q

What 4 factors make speech speech-like?

A

1) Patterning
2) Modulation and rate
3) Envelope characteristics
4) Amplitude

48
Q

What is speech to a hearing aid?

A

Hearing aids can understand speech characteristics very well, and generally do a very good job with speech

49
Q

What 4 characteristics make music music-like?

A
  • Patterning, modulation, envelope characteristics, and amplitude can be highly variable
  • Music to a HA is like a wild card (it can be exceptionally different from speech)
50
Q

Hearing aids are primarily concerned with the goal to amplify ____

A

speech

51
Q

Compared to speech, music has what 3 things?

A

1) Music has a greater intensity range (or, very small)
2) Music has lower frequency components (or, none at all)
3) Music may have variability and pattern unlike speech (not like speech!)

52
Q

Before the A/D converter, with 16 bits of processing, a compressor in the hearing aids generally limits inputs greater than ____

A

~96 dB SPL (i.e., loud components of music)

53
Q

Where is the design problem for music processing?

A

It’s a design problem at the “front end” (input), not a programming issue

54
Q

What is the problem with very loud inputs?

A
  • Each bit has a 6-dB dynamic range, so 16-bit A/D converter has a dynamic range of 96 dB.
  • This dynamic range is OK when the input to the HA is speech, but not necessarily when the input to the HA is music!
55
Q

What happens to these very loud inputs?

A

Inputs that exceed the upper limit of the A/D converter’s dynamic range will be a major limitation if music is loud (a distorted signal at the front-end cannot be improved at a later stage)

56
Q

What is the crest factor?

A
  • Crest Factor: Average Speech, at 1 meter distance is approximately 65 dB and the peaks of that same speech is 12 dB
  • It measures the difference between the highest and average levels of sound.
  • A high crest factor means there are significant peaks in the sound signal, which could potentially lead to distortion
57
Q

Music programming can be ____ or ____

A

Automatic, manual

  • All manufacturer’s have a music setting
  • In a lower end HA, the music program is manual
  • In a high end HA, the music program is automatic
58
Q

Generally, the music program has what 6 features?

A

1) adaptive DM turned off
2) noise reduction system turned off
3) transient noise reduction turned off
4) feedback management system turned off or less aggressive
5) no frequency lowering
6) more linear processing (to maximize the bandwidth and input)

However these don’t solve the “front-end” hearing aid limitations

59
Q

How can we as clinicians, make music listening optimal?

A

Trick #1: Dampen the sound. How? Scotch tape is one suggestion!

Trick #2: Decrease music volume; increase HA volume

Trick #3: Use an Assistive Listening Device (like FM, or remote microphone)

Trick #4: Remove the Hearing Aid (Really?)

60
Q

What is tinnitus?

A
  • Subjective tinnitus is characterized by the perception of sound in the absence of externally generated sound. While it is commonly referred to as “ringing in the ears”, tinnitus can be experienced as different auditory sensations such as: buzzing, hissing, whistling, swooshing, or clicking
  • Tinnitus effects patients in a number of ways. Some patients are not bothered by this perception, while some are extremely bothered by its presence
61
Q

What causes tinnitus?

A
  • Common causes of tinnitus may include noise exposure, ototoxic medications, head trauma, TMJ dysfunction, Ménière’s disease, acoustic neuroma, high level of stress, and anxiety disorders
  • Hearing losses are often associated with tinnitus
62
Q

What are some management strategies for tinnitus?

A
  • Tinnitus can be managed by bringing sound back into the auditory scene as part of many other approaches (counselling, managing other health conditions if relevant, CBT)
  • Aiding hearing loss is one part of the approach
  • Noise generation from within the hearing aid can also be used to “mask” tinnitus
63
Q

What is a good comparison to tinnitus?

A
  • Tinnitus to a patient is a candle lit in a room
  • It is relative to the background (what auditory enrichment do you have otherwise)
  • If all the lights are on, the candle blends into the background
  • When the lights get shut off, you can really see the candle
64
Q

How do most manufacturers deal with tinnitus?

A
  • noise generator (white noise, pink noise, audiogram-shaped)
  • programmable noise characteristics
  • mic activated or not
65
Q

Explain the difference between white noise, pink noise, audiogram-shaped noise.

A
  • White noise: equal energy across all frequencies
  • Pink noise: different tonal quality to white noise
  • Audiogram-shaped noise: personalized noise dependent on their audiogram
66
Q

How does the widex: zen program work?

A
  • best manufacturer for tinnitus
  • initially developed for relaxation
  • fractal technology (random music-like tones)
  • programmed to patient preference
67
Q

Data logging: what 5 things might a HA keep track of?

A

1) how often HA is in each environment classification.
2) how often HA automatically switches to DM, NR, etc.
3) overall intensity of input signals in patient’s environments.
4) actions taken by the user: VC change, hours of use per day, manual selection of programs, etc.
5) may recommend programming changes for the audiologist to do

68
Q

What can it mean if data log > self-report

A

does patient turn off HA when it’s not worn (e.g., at night)?

69
Q

What can it mean if self-report > data log

A
  • does patient want to please? Is patient using HA with dead battery? Does HA usage vary from day to day (may be harder for patient to track hours of use)?
  • Has patient not been using HA at all for a couple of days? (avg hrs of use = total hrs ÷ # of days since last programmed)
70
Q

When do we get a more accurate self-report?

A
  • More accurate self-reports when patients are aware of data-logging
  • Manufacturers are beginning to recommend obtaining consent for datalogging
71
Q

What should you tell patients about data logging?

A
  • these HAs are going to try to collect information based on what type of environments you are in, how much noise, how often the HAs are being worn
  • When you come back for your follow up we want to see if we made good programming choices or if we can tweak anything for you
72
Q

What are 5 examples of data logging being helpful?

A

1) Use for counselling purpose but use tactfully.
2) If discrepancy between data log and HA use: try to figure out why (patient wanting to please, not turning off HA at night, sick for a few days with no HA use, etc.). Is the date of data logging activation the same as date of HA fitting?
3) Reports trouble hearing on the phone: is the patient using the telephone program correctly?
4) How often are manual programs used? Are they really needed?
5) What kinds of environments is the patient typically in?

73
Q

What is data learning/trainable hearing aids?

A
  • aka self-learning hearing aids
  • Following a period of data logging, the HA automatically makes changes, based on patient behaviour/preferences
  • Feature can be deactivated in software
74
Q

What are the drawbacks of data learning/trainable hearing aids?

A
  • May not be suitable for 1st time user who “plays” (or experiments) with hearing aid a lot
  • Patients may alter the fitting that should not be altered
75
Q

How does VC work on a HA?

A
  • VC change on one HA adjusts the VC of both aids simultaneously
  • Program button on one HA changes the program of both HA simultaneously
  • Can program the VC for right HA and program button for left HA (or vice versa).
  • If dexterity issues on one side, activate the controls on the good side.
76
Q

What 3 patients would want to be able to adjust VC on each HA separately?

A

1) car driver with passenger: turn down VC on left side
2) restaurant: turn down VC on noisy side
3) Asymmetric hearing losses (patients may want to individually manipulate the VC)

77
Q

What does a HA often have indicators for?

A

Low battery, program change, VC change (max, min, prescribed), etc.

78
Q

What do indicators depend on?

A
  • Should all beeps be kept active? Will this be confusing? Which one(s) do you keep on?
  • Beeps vs spoken language on some HAs
79
Q

When should you tell your patient about indicators?

A

Demonstrate (play) to the patients after programming & REM are completed, before disconnecting HA.

80
Q

6 functions of a HA app include:

A

1) VC and program changes
2) Home: Quick return to everyday program
3) Directionality focused to left, right, front, rear
4) On/Off - is “Off” a mute? Mute = battery drain
5) Frequency response adjusted by patient
6) Geo-tagging - patients save their preferred settings for a specific location (e.g., favourite restaurant); HA automatically goes to preferred settings when phone GPS shows HAs are in that location

81
Q

What type of HAs do you need if you want to connect to the app?

A

Pairing is required between phone and hearing aid, so wireless hearing aids are required.

82
Q

How does app remote programming work?

A
  • Programming changes to hearing aids without the patient being present
  • At time of fitting, hearing aids are paired to patient’s smartphone
  • App requires downloading
  • Post-fitting fine tuning is done remotely without the need for the patient to come to the clinic
  • Audiologist downloads the programming, makes changes, and sends to patient; patient receives changes and transfer them into the hearing aids
83
Q

For what kinds of patients would app remote programming be particularly useful?

A

Need to be tech savvy, don’t have REMs to verify changes, good for patient’s that can’t get to the clinic

Amplification II (13 decks)

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