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Amplification I > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

What is the conversion for hearing aid fittings from audiometric data to sound delivery in the canal?

A

Audiometric data from dB HL to dB SPL

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2
Q

What are the 6 targets and 2cc values we need to take into consideration?

A
  • Ear Canal Resonance
  • Real-Ear to Coupler Difference (RECD)
  • Microphone Location Effects
  • Earmold of BTEs (tubing and venting effects)
  • Shell modifications on custom hearing aids (fit and venting effects)
  • *Reserve Gain
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3
Q

What does REUG/REUR mean?

A

Real-Ear-Unaided Gain/Real-Ear-Unaided Response

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4
Q

What does REAG/REAR mean?

A

Real-Ear-Aided Gain/Real-Ear-Aided Response

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5
Q

What does REIG mean?

A

Real-Ear Insertion Gain

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6
Q

What does REOR mean?

A

Real-Ear Occluded Response

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7
Q

What does RECD mean?

A

Real-Ear to Coupler Difference

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8
Q

What is the REUR?

A
  • What is the response of sound in an ear canal
  • The Real-Ear Unaided response is the sound pressure level, across frequencies, measured in an open and unaided canal for a signal that is delivered (it is what the ear is bringing to the table that effects sound)
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9
Q

Is every ear the same? What will vary person to person?

A

There is variability in this measure (REUR) across patients due to unique shape of their ear canal

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10
Q

REUR - what is the typical adult resonance? Where does it peak?

A

Increase in sound pressure usually between 1500-7000 Hz, with a peak nearing 2700-3000 Hz

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11
Q

What are 4 other terms for REUG?

A
  1. Ear canal resonance
  2. External Ear effects
  3. Unoccluded response
  4. Free-field to eardrum transfer function
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12
Q

What is the REUG?

A
  • The gain or “boost” in sound provided by the pinna and the ear canal itself when un-occluded
  • What is the ear bringing to the table in terms of gain because of unique characteristics?
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13
Q

What is the typical REUG?

A

Typical between 10-20 dB of gain

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14
Q

Why do we have to account for the REUG?

A
  • Need to account for this because of the hearing aid
  • Want to make sure not overboosting these frequencies because of the natural gain effect from the pinna
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15
Q

What does an average REUG look like in measurement?

A

REUG measurement, will look like this hillside effect, upside slope between 2700 and 3000 Hz

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16
Q

Explain the relationship between gain and response

A
  • REUR with a 50 dB input across the frequencies
  • The difference between the input and output is the gain
  • This particular measurement involves a probe mic, within 5 mm of the eardrum ideally, playing a sound (broadband noise, pink noise) from a loudspeaker
  • The reference mic needs to be facing outwards & is near the ear because need to make sure the level that you are playing the sound at from the speaker is actually reaching the ear before reaching the probe tone
  • If you have a lot of soft wax, probe tube might get blocked because of picking it up as you place the probe tube
  • If lots of hard wax, that will affect the resonance, might need to do cerumen management first
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17
Q

What are the 5 steps to measure REUR and REUG? What type of stimulus?

A
  1. Otoscopic Examination
  2. Probe tube is place in the ear canal, placed to approximately 5mm of the TM (black marker to inter-tragal notch)
  3. Patient is placed in front of the verification equipment speaker
  4. Select and deliver a stimulus (usually broadband sound)
  5. Measure the REUR/REUG
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18
Q

What is the approximate length for a probe tube?

A
  • 28mm for female
  • 30mm for male
  • 20-25mm for pediatric patients
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19
Q

Label the REM diagram

A
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20
Q

Where is the probe tube placed?

A

Put the probe tube in the front of the retention cord (want to hold it in place)

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21
Q

What does the probe reach in the ear canal?

A

The bony portion

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22
Q

What is the REAR?

A
  • What is the response delivered to the ear canal with a hearing aid turned on
  • A real ear aided response looks at the total response of the hearing aid delivered in the ear canal, taking into account the gain provided by the hearing aid and the patient’s ear canal when a signal is delivered
  • This is the number 1 way to perform the verification portion of fitting
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23
Q

What unit is REAR measured in?

A

dB SPL

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24
Q

What is the REAG?

A
  • What is the response delivered to the ear canal with a hearing aid turned on
  • A real ear aided gain looks at the total gain of the hearing aid delivered in the ear canal, taking into account the gain provided by the hearing aid and the patient’s ear canal when a signal is delivered
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25
Q

What is the REAG determining?

A

Difference of Input and Output with hearing aid active

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26
Q

What is REIG?

A
  • What is the amount of gain provided by the hearing aid
  • Insertion Gain is another method of verifying the hearing aid output (in dB)
27
Q

What is REIG determining?

A

Insertion Gain = Real Ear AIDED Response-Real Ear UNAIDED response

28
Q

What prescriptive formula is used for REIG?

A
  • We use NAL-NL1 because it gives us target across levels
  • NAL-NL2 and DSL will give only 1, which is good for linear compression (only providing same gain across frequency)
  • REIG is not used as well currently because we can only use NAL-NL1 to take compression into account, but it is an outdated prescription!
29
Q

What happens when unaided response and aided response are the same?

A

There is no effect of the gain (ineffective)

30
Q

Is it Better to focus REIG or REAR?

A
  • Evaluating what method may be best in clinical practice requires an understanding of what both measurements show in terms of hearing aid benefit
  • Today, REAR is a popular method for speech mapping verification on ear as it shows the total effect (hearing aid gain and individual characteristics) and the performance of the hearing aid/benefit on our patient
  • Want to look at the aided response in comparison to thresholds
31
Q

What is the REOR?

A
  • The Real-Ear Occluded response measures how the hearing aid or earmold changes the REUR when the hearing aid is in place and is turned off (i.e if the hearing aid is acting like an earplug)
  • Looking at how the hearing aid is changing the resonance
  • It is an estimation of venting effects (it will tell us if we are occluding the response that we want to get inside of the ear)
  • This is looking at how much blockage am I getting from external sound sources
32
Q

What type of dome is most occluding?

A

Power dome=most occluding, drop off in gain around 500 Hz, acting like a pseudo plug, occluding the gain that we want to give

33
Q

The open dome is most similar to the ____

A

REUR

34
Q

Closed dome gives us a bit of a drop in ____

A

Mid-high frequencies

35
Q

Why do we want to know the REOR?

A

We may be interested in looking at an occluded response if we want to be sure that an “open fit” hearing aid is not attenuating sound!

36
Q

Are we measuring the occlusion effect with REOR?

A
  • No because with the occlusion effect there is internal noise, increase in low frequency sound pressure, echoing through the ET, mandible, and condyle
37
Q

What is the RECD?

A
  • Difference, as a function of frequency between to output of the hearing aid in the ear and in coupler
  • Boyle’s Law: space matters! Pressure changes inversely with volume
  • RECD takes into account unique differences in ear canals- creating a more tailored fitting
  • Coupling to measure the RECD may be with an insert earphone or the patient’s earmold
  • This is like the difference between a shirt and a tailored shirt
  • Can use the patients ear mold to give us an RECD reading
38
Q

What is the tric adaptor?

A
  • Tric adaptor: the rubber piece attached to the cavity
  • Knowing the difference of the SPLs in a cavity vs in the ear
39
Q

How do you do RECD measures on pediatric patients?

A
  • Achieving RECD measures on pediatric patients to ensure amplification is ideal
  • Smaller ear canal volumes will mean relatively higher SPL than a standard 2cc coupler
  • Because ear canals are much much smaller, means the SPL will be bigger because smaller cavity
  • Can put the probe tube against the earmold itself, then place the earmold into the ear, and then attach the transducer onto the top of the earmold itself (red arrow)
  • Bring the clip across from the body to opposite side to help reduce slack
40
Q

Explain the RECD values as a child grows

A
  • When child is younger, the value of SPL is higher, as the child is aging, decrease in the SPL relative to the original stimulus because space is increasing, getting bigger
  • Ideal to do these measured RECD or taking normative values for these ages, ideal to do this every 6 months
  • Need to change ear molds every few months anyways
41
Q

What are the 4 factors that influence RECD values in pediatric and adult patients?

A
  1. Ear canal volume size- age dependant
  2. Vents, slit leaks, open fittings
  3. Myringotomy tubes/pressure equalizing tubes
  4. Perforations
42
Q

What is the MLE?

A
  • Microphone location effects or Field to microphone transformation effects
  • Without use of a hearing aid, the combined pinna effects produce an increase in SPL
  • The amount of boost in gain will be partially dependant on where the microphone is located (i.e the change in the frequency response simply by changing the location the microphone)
43
Q

What does MLE depend on? Explain.

A
  • MLE will depend on the HA style- (BTE vs IIC)
  • BTE, not in the ear, microphones are on top
  • IIC, will retain the pinna effect and part of ear canal resonance because deeply set into the ear
44
Q

Explain the MLE values in free-field vs. diffuse field

A
  • In an acoustic free-field there are no reflections; sound waves reach an observer directly from the sound source. No reflections of sound are present (like our sound booth, no reverberation)
  • A diffuse-field describes an acoustic field where sound waves reach the observer from all directions (reflective surface, sound waves reaching observer from all directions)
45
Q

MLE in BTE vs CIC (picture)

A
  • BTE slight increase due to where that is
  • CIC has more pinna effect, looks more similar to regular ear boost from pinna
  • Bigger boost with sound to the ipsilateral side, compared to the front with CIC
46
Q

A BTE hearing aid provides 30 dB of gain at 4000 Hz, what gain and output would be occurring at the TM with a 60 dB input?

A
  • MLE = 4
  • RECD = 2
  • HA gain (2cc values) = 30 dB
  • Microphone effects=+4
  • 60 + 2 + 4 + 30 dB gain = 96 dB output
  • 36 dB of gain – notice how this differs from the gain that we inputted, not 30 dB it is 36 dB
47
Q

What is the TEREO?

A
  • The Transform for Estimating Real-Ear Output
  • We have 2cc values, and we wish to know the estimated real-ear equivalent
  • Add the values of the RECD and the MLE
    • TEREO= RECD + MLE
  • We have ear canal SPL values and we wish to know the coupler equivalent
    • Subtract the values of the RECD and MLE
48
Q

What is reserve gain?

A
  • Reserve gain is an important selection in hearing aids as it leaves a “buffer”.
  • 10 -15 dB of gain at each frequency ideally.
  • Hearing sensitivity changes (aid can be reprogrammed to meet needs)
  • Volume control (accounts for listening preference)
  • Minimizing distortion (aid is not working at it’s maximum level)
  • Ideal to leave a little extra room for the hearing aid to give gain to
  • If sensitivity changes, can reprogram that hearing aid from that gain
  • With volume control, provide the ability for the patient to turn the sound up a bit if they need it
  • Don’t want the output to be crashing into the MPO, creates distortion
49
Q

What can we look at in our manufacturer software?

A

Using our manufacturer software, we can observe the hearing aid gain, receiver options, coupling options to determine if a hearing aid will be a suitable fit for our patients!

50
Q

What are we looking at with quality control in hearing aids?

A
  • How does hearing perform compared to how it should perform
  • This is NOT a measure of audiologic suitability for our patients (no consideration of audiogram)
51
Q

How do we test quality control in hearing aids?

A
  • In our hearing instrument analyzer (test box), we set the aid in test box for ANSI testing, connect to the programming software to TEST MODE. We will determine if the hearing aid is set to:
  • FULL ON GAIN (FOG) or REFERENCE TEST SETTING (RTS)
  • All adaptive features of the HA should be turned off (feedback managers, noise reduction features, compression, automatic gain control)
52
Q

What are the 8 ANSI tests?

A
  1. Output sound pressure level with 90dB input (OSPL90)
  2. High frequency average output sound pressure level 90dB input (HFA-OSPL90)
  3. Response curve full on gain with 50dB inputs (FOG)
  4. High frequency average full-on gain (HFA-FOG)
  5. Reference test gain (RTG)
  6. Total harmonic distortion (THD)
  7. Equivalent input noise (EIN)
  8. Battery current drain
53
Q

OSPL90
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? How much power output is the hearing aid capable of?
  • How are we measuring it? A 90 dB stimulus, across a frequency range is presented, and the output is measured in the coupler
  • TOLERANCES: Within 3 dB of specifications from manufacturer
54
Q

Is OSPL90 the same thing as MPO?

A
  • OSPL90 is very different than setting the MPO of the HA in fitting verification
  • MPO is dependent on the patient’s comfortable level (ANSI testing is different)
55
Q

HFA-OSPL90
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? What is the average output of the frequencies of 1000 Hz, 1600 Hz, and 2500 Hz **unless the manufacturer sets a different set of frequencies.
  • How are we measuring it? A 90 dB stimulus, across a frequency range is presented, and the output is measured, and the average of the frequencies aforementioned
  • TOLERANCES: Within 4 dB of specifications
56
Q

FOG
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? What is the output of the hearing aid when hearing aid gain is set to maximum, with a softer input?
  • How are we measuring it? A 50dB stimulus, across a frequency range is presented, and the frequency response output is measured
  • TOLERANCES: Within 5 dB of specifications set by the manufacturer
57
Q

HFA-FOG
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? What is the average output with the 50 dB input of the frequencies of 1000 Hz, 1600 Hz, and 2500 Hz **unless the manufacturer sets a different set of frequencies.
  • How are we measuring it? A 50 dB stimulus, across a frequency range is presented, and the output is measured, and the average of the frequencies aforementioned
  • TOLERANCES: Within 5 dB of specifications
58
Q

RTG
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? The response of the hearing aid at an appropriate user setting with a softer input (near average speech)
  • How are we measuring it? A stimulus is presented (usually at 60 dB) across a wide range of frequencies, the response is measured with the volume control at a “normal level”
  • TOLERANCES: Informational purposes only, no tolerances specified by ANSI
59
Q

THD
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? Is there good fidelity of the signal from input to output? Are there any other frequencies or harmonics generated?
  • How are we measuring it? Distortion is measured in percentages
  • TOLERANCES: no more than 3% compared to manufacturing specifications
60
Q

EIN
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • What are we measuring? How much internal noise is the hearing aid itself creating?
  • How are we measuring it? Calculation of the noise creating by the hearing aid with no signal present
  • TOLERANCES: no more than 3 dB above the manufacturer’s specifications
61
Q

Battery current drain
- What are we measuring?
- How are we measuring it?
- Tolerance.

A
  • Battery drain can depend on factors such as where the volume control is set, the inputs, the use of streaming, and other hearing aid processing features
  • What are we measuring? If the drain of the battery is reasonable, and is measured in mA
  • How are we measuring it? Testing the draw of the battery in the following settings:
    • Quiescent, with 65 dB input, and 90 dB inputs
  • Tolerances: Should not exceed 20% of the maximum value specified by the manufacturer
62
Q

What is expansion?

A
  • Expansion (reduce the output for low-level inputs)
  • The specifications sheets must note if expansion was used during measurement
63
Q

What 2 ANSI components deal with expansion?

A
  1. EIN
  2. Battery current drain

Amplification I (14 decks)

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