1' Is there anything really new that I need to know for fitting infants and children

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1. Is there anything really new that I need to
know for fitting infants and children?

• I think so.
• Verification is the important stage in hearing
  aid fitting when we measure the hearing aids
  performance.
• The accuracy of frequency response measurement is
  affected by the processing of different hearing
  aid and different test signals.

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2. Cant I just push the ANSI test button on my
test box?

• Im not talking about running standard test box
  ANSI data.
• What Im talking about is measuring the hearing
  aid at user setting.
• Be sure the aid has been set to the prescribed
  targets for that persons ear.

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3. Does the test signal really matter?

• Absolutely.
• Since the goal is to program the patients
  hearing aids to process speech effectively, many
  believe that speech signals are best suited to
  determine how the hearing aid will work in the
  real world.

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4. Why dont we always use speech signals?

• It was fairly costly to build a system that could
  digitally store pre-recorded calibrated speech
  signals, play them to the hearing aid, analyze
  the amplified speech coming from the hearing aid
  .
• Generation One of speech-based fitting system

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5. Why the test signal really matters that much?

• The result showed that verification accuracy
  depends a lot on what type of test signal you
  use,and hoe you use it.

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6. I thought you couldnt test digital hearing
aids with older test signals, like pure tone.

• To some extent thats true.
• Level, shape, bandwidth, and envelope of test
  signals can interact with some features of modern
  hearing aids.

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7. How does test signal level matter?

• A WDRC hearing aids, obtain more gain for soft
  speech and less for loud speech.
• You need to know what input levels were used to
  derive targets for your favorite prescriptive
  method.
• The DSLi/o uses a 53-dB-SPL speech spectrum to
  represent soft speech.

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8. What about bandwidth?

• The long-term average speech spectrum (LTASS) has
  a bandwidth of almost 5 octaves (about 200 to
  5000 Hz).
• Individual speech sounds, /s/, peak at 7000 to
  10,000 Hz.
• Test signals that have very broad or very narrow
  bandwidths may cause the hearing aid to produce a
  different amount of gain than it would for
  speech.

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9. If I have a broadband test signal, does its
shape matter?

• Speech-shaped test signal should be shaped like
  thispeaking around 500 Hz and rolling off
  gently.
• The shape of the LTASS varies with vocal effort,
  but at average vocal effort it peaks at 500 Hz
  and rolls off afterward at about 3dB per octave.
• Speech-shaped test signals were more accurate
  than the flat test signal for the majority of
  hearing aids.

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10. If the shape of the test signal is the same
for REUG and REAG measurements ,do different
shapes still have an effect on gain?

• Shape matters less.
• For accurate verification in the high frequencies
  or for loud speech, it is more accurate to use a
  precisely shaped signal.

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11. Whats the envelope of a test signal?

• The envelope of the test signal is the modulation
  in level .
• Speech at an overall level of 65dB SPL has
  moment-to-moment changes in level that span a
  30-dB range.
• Test signals with modulated envelopes were more
  accurate for testing digital hearing aids with
  noise detector.

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12. What should I do if Im testing a digital
hearing aid with noise reduction and I dont have
a modulated test signal?

• The simple solution would be to turn off the
  noise reduction.

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13. The more my test signal is like real
speech,the more accurately it estimates the gain
for speech?

• Even a creatively made, speech-like test signal
  may be unable to test all current or future
  hearing aids perfectly.
• Most of our noise-detecting hearing aid used
  envelope to decide if something is speech-like or
  noise-like.

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14. In an ideal world, would we all have
real-speech test systems?

• Right now, theres no standard for verifying user
  settings of hearing aids with speech.
• Some test systems use prerecorded, calibrated,
  shaped signals, and with others you talk to the
  aid yourself.Some offer both.
• If we all used similar speech signals, calibrated
  to the same levels and shapes,verification with
  speech could become a standard procedure.

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15. Whats the next step?

• The format also is important.
• Even if all systems use the same signal, they
  still can give different results just because of
  format.

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16. Any system that made speech measurement are
the same.How much difference can there really be?

• Speech envelope can be a big difference.
• Long-term average speech level is about 65dB at
  500Hz, the peaks of speech will be 77dB
  SPL.(unaided)
• If add 20dB of real-ear gain, aided result would
  be 85dB SPL or 97dB SPL.(aided)
• Unless these are referring to the same type of
  units, mismatches can occur.

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17. Cant I just use the manufactures automatic
fitting to target?

• In a recent Hearing Journal article,David and
  Jodi found that manufactures estimates of
  hearing aid gain were not accurate in all ears.
• However, for infants and children, with smaller
  ear canals and limited ability to tell us how the
  hearing aids sound to them ,using automatic fits
  without verification is pretty scary.

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18. What can I do to make sure that my pediatric
patients receive accurate fittings?

• Dont rely only on functional gain.
• Measure their individual RECD, use the corrected
  coupler targets to set the hearing aids.
• Measure the hearing aids with as speech-like a
  signal as you can, making sure that your test
  inputs and format and target inputs and format
  are in close agreement.

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19. Is all of this necessary?

• The experts at AAA seem to think so.
• Childrens ears are smaller and highly variable,
  and automatic fits arent always accurate and may
  not always be appropriate for infants and
  children.

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20. Is that okay if I do an aided audiogram in
the test booth?

• Its sometimes helpful to have test results that
  tell you that the child perceives amplified
  sound.
• Unfortunately, a better aided audiogram doesnt
  necessarily mean a better hearing aid fitting.
• The aided audiogram does not verify aided
  function for the types and levels of signals that
  we hear in real life.