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Amplification I > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

What do we know about loudness tolerance and dynamic range with normal hearing, conductive hearing losses, and sensorineural hearing losses?

A
  • Normal hearing has a large dynamic range
  • SNHL has a smaller dynamic range
  • CHL: when we get over the conductive component, we usually see a large dynamic range
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2
Q

What is loudness comfort?

A

The term we use to describe the upper levels of comfort/the point of discomfort in loudness are numerous
- LDL (Loudness Discomfort Level)
- UCL (Uncomfortable Loudness)
- ULL (Uncomfortable Loudness Level)
- TD (Threshold of Discomfort)
- ULC (Upper Level of Comfort)
- HCL (Highest Comfortable Level)
Top two are the most popular

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3
Q

Average UCLs and MCLs (picture)

A
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4
Q

Variability in UCL (picture)

A
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5
Q

What is the maximum power output?

A

MPO refers to the maximum output of the hearing aid when specific settings have been set/determined such as gain for various inputs and compression specific to the patient’s audiological needs, their prescriptive targets, and their comfort

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6
Q

Is MPO and OSPL90 the same thing?

A
  • MPO is not necessarily the OSPL90 (the maximum potential output of the hearing aid)
  • MPO can not be higher than the OSPL90, but the OSPL90 can be higher than the MPO
  • OSPL90 has nothing to do with patient audiologic profile
  • MPO has to do with your patient
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7
Q

What is the process for MPO?

A
  • Like setting appropriate levels of gain for our patients based on soft, average, and loud targets, setting of the MPO is another highly important measurement as we do not want to have the hearing instruments amplify to a level of discomfort
  • Like measuring gain for soft, average and loud inputs, MPO is also determined, measured and verified, with adjustments being made as needed
    • Can be done in test box
    • Can be done on-ear (if patients can tolerate it)
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8
Q

What are we measuring with MPO?

A

What are we measuring: the SPL the hearing instrument is delivering to the ear, and adjusting the maximum power output as needed

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9
Q

The procedure of MPO is similar to a REAR with speech stimuli except…

A
  • The test signal is LOUD (85 to 90 dB SPL)
  • Short pure tones rather than speech (evaluating where the frequency response falls)
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10
Q

What do we have to do once the MPO test is completed?

A

Once the test is completed, we need to evaluate if the MPO needs adjustment:
- Turning DOWN MPO is the patient cannot tolerate the test signal
- Turning UP MPO if there is insufficient headroom (and if the patient can tolerate MPO)
- Between gain and MPO

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11
Q

Set MPO in ____ and measuring on ____

A

Software, verification equipment

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12
Q

What is a common complaint with HA users and what does this lead too?

A
  • “Aids are too loud” is often a common complaint with hearing aid users
    • This complaint can lead to rejection of use
  • 42% of hearing aid users are satisfied with the loudness settings of the hearing aid when measured and set appropriately
  • When set appropriately, this a a component of fitting that leads to high satisfaction
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13
Q

What are the 2 consequences of setting the MPO too high?

A
  1. Discomfort (leading to hearing aid rejection)
  2. Over-amplification (leading to noise induced hearing loss (either a TTS or PTS))
    Note: patients will reject amplification if the MPO is too loud, not due to gain being off
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14
Q

Do MPO problems go away?

A

“Maximum Power Output problems don’t go away.
Either you take care of them when you fit the hearing aids, or you take care of them with repeat visits— or return for credits”

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15
Q

Example pic of before and after adjustments

A
  • Previous to adjustment, the MPO is measuring above the UCLs of the patient
  • When you make an adjustment you always have to re-measure
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16
Q

What is happening in this MPO measurement?

A
  • At some points in the MPO measurement, primarily at 250 and near 3000 Hz, the 99th percentile for this speech input is reaching the MPO
  • Ideally, we would first attempt to raise the MPO to create headroom
  • If this is tolerable, doing so will lead to better sound quality.
17
Q

How does loud speech saturation work when using obnoxious stimuli?

A

Was looking if you could stimulate something obnoxious (marbles) and bring it down to a comfortable level

18
Q

How do we create more headroom?

A

To create more headroom, we either increase the MPO (if tolerable) or decrease gain

19
Q

What happens when we don’t set MPO correctly?

A
  • If MPO is set too high… discomfort, or rejection if loudness is perceivably too loud
  • If MPO is set too low… sound quality issues may arise
    • Distortion, muffled quality to sound when loudness nears the MPO
    • Unnatural perception of the differences between soft, average, and loud sounds
20
Q

What should you tell the patient about MPO?

A
  • Explaining the procedure to patient, focusing on why we are performing this procedure
  • “You will hear a series of loud beeps. We are measuring how the hearing aids will respond to those sounds. We want to ensure that the hearing aid is not boosting those sounds above your loudness tolerance”
  • “if something loud happens in your environment, we are making it so that it isn’t going to be uncomfortable for you”
21
Q

What do you do when the measured MPO is not representing the MPO of the hearing aid

A
  • Regardless of adjusting gain, the MPO measurement does not seem to be changing…
  • What to look at:
    • What is the REUR of the ear? REUR gives a lot of good information about what the ear itself is bringing to the table
    • This is a point where counselling is very important
22
Q

Where are UCL targets derived from?

A
  • Average or patient specific measures
  • There is general agreement amongst clinicians that the MPO should be set below the level of discomfort
  • There are differences of opinion amongst clinician on how to do this
    • Should MPO setting be based on a measured UCL for an individual patient? Should we get that info from within the sound booth?
    • Should clinician relay on a prescriptive rationale (NAL-NL2/DSL) that uses an average UCL calculation?
23
Q

What are the pros and cons of average vs patient specific measures?

A
  • Many clinicians don’t measure patient specific UCL’s (it takes a lot of time)
  • Can calculate a average UCL based on thresholds, age, etc.
  • But if we measure patient specific UCL’s, it is much more targeted to the patient
24
Q

To measure or not to measure UCL?

A
  • Fewer post-fitting hearing instrument adjustments were needed, based on patient comments, when UCLs are measured pre-fitting
  • Patients who were tested for UCLs reported greater satisfaction with the hearing instruments compared to patients who had no UCL testing
  • Measured patient specific LDLs may not be required if verification (with predicted LDLs) and validation measures of loudness perception are completed
25
Q

What are the approaches for the selection of UCL targets?

A
  • Base the targets on estimated UCLs from pure tone thresholds, using prescriptive rationales (the system will give you an average UCL for the patient)
  • Base the targets on measured, patient specific UCLs, enter this data manually in verified
26
Q

What are 4 factors that influence patient-specific UCLs?

A
  1. Instructions given to the patient
  2. Initial Discomfort, Definite Discomfort, or Extreme Discomfort (this could potentially have upwards of 30 dB variability)
  3. Type of test signal used
  4. Duration of test signal used
27
Q

How does the test signal influence the UCL?

A

Test Signal Matters: more complex sounds are perceived to be louder than less complex sounds of an equal intensity (i.e. speech/broadband signals vs. pure tones/narrowband signals)

28
Q

Should testing be done with pure tones, warble tones, NBN, or speech stimuli?

A
  • Test with frequency-specific signal
  • UCLs that are measured with speech stimuli can be difficult to extrapolate a large frequency range
  • If present a pure tone and speech at 100dB, speech will be perceivably louder to the patient
  • Testing with warble tones can give very frequency specific information
  • pulse tones are often used
29
Q

What does stimulus duration do?

A
  • Stimulus duration also affects loudness judgments
  • We want a short duration (if a tone is presented longer, the patient will say the longer sound was louder, even though it was the same level)
30
Q

What are 5 patient factors that influence the UCL?

A
  1. Fatigue
  2. Anxiety
  3. Mood
  4. Underlying Conditions (i.e. hyperacusis and tinnitus patients)
  5. Most patients with hyperacusis also report tinnitus, while 30-40% of patients with tinnitus exhibit symptoms of hyperacusis
31
Q

Explain the loudness categories for for the cox contour test?

A

7.Uncomfortably Loud
6.Loud, but OK
5.Comfortable, but slightly loud
4.Comfortable
3.Comfortable, but slightly soft
2.Soft
1.Very Soft

32
Q

What are the instructions for the Cox Contour test

A

“The purpose of this test is to find your judgments of the loudness of different sounds. You will hear sounds that increase and decrease in volume. You must make a judgment about how loud these sounds are. Pretend you are listening to the radio at that volume. How loud would it be? After each sound, tell me which of these categories best describes the loudness. Keep in mind that an uncomfortably loud sound is louder than you would ever choose on your radio no matter what mood you are in.”

33
Q

What is the testing procedure and guidelines for the cox contour test?

A
  1. Provide the patient with the loudness categories (sheet)
  2. Begin obtaining UCLs at 2 frequencies minimally (ideally measuring 500 Hz, and 2000 Hz), obtaining more information when possible
  3. Use an ascending method
  4. Begin testing at an “average” comfortable level (65 dB HL) increase in 5 dB steps. Start above patient threshold
  5. When a patient reports that the test signal is “uncomfortably loud” (#7)
  6. Do a second run, mark the UCL (if there is disagreement, do a third run)
34
Q

If all measures and done, and verification indicates that gain for soft, moderate, loud inputs are ideally set, and patients still note that sound is too loud, what do we do?

A

Is this a matter of adjusting to amplification as a whole?
Do we need to utilize an adaptation manager?

35
Q

Verification and Validation of MPO Settings

A
  • Verification, through probe mic measures, or through test box is the best practice to determine if the MPO measurement is set appropriately.
  • Validation, through follow-up can confirm is these setting are comfortable in the real world
  • Adjustments can be made based on both outcomes

Amplification I (14 decks)

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