TESTING FM SYSTEMS USING
REAL EAR MEASURES
AND
BEHAVIORAL MEASURES
EVALUATION OPTIONS
A.
Audio-Visual Checks
B.
Electroacoustic Measurements
Verifying Performance
Matching FMs to HAs
C.
_________________Evaluation
**Matching FMs to HAs**
D.
Behavioral Evaluation
_________________ Recognition
Real Ear Measurements:
The _______________ Assessment
Same
principles re: matching _______________ apply
Main
difference is to place FM mic as close to _______________mic as possible
Use same
inputs as for Electroacoustic Measures
Gain-Complex
Signal: HA 65 & FM _______________
Max
Output-Sweep Pure tone: Both at _______________
Assumption
that HA fitting already verified via probe mic measures
Goal is
to ________________ FM to HA Characteristics as done with
Electroacoustic Measures
Preliminary Setup
Set System to present _______________ Signal
Set
System to show Output, not _______________
STEP 1 - Level & SETUP
Insert
Probe Mic in Ear Canal
Reference
Mic is placed _______________ test ear
Level the
test system
After
leveling, Turn _______________ mic off
STEP 2 - Match FM and HA
Output
Change
setting to Aided 1
Curve
1. Test HA alone with 65 dB _______________ complex input-
Well call this RHA65
Change
setting to Aided 2
Curve
2. Test HA&FM system (set to FM only) with _______________dB SPL
complex input
Compare
Curves 1 and 2
Adjust
volume of HA with FM Receiver boot to
match HA output
STEP 3 - Match FM and HA
Output
Change
setting to Aided 1
Curve
3. Test HA alone with _______________ dB SPL pure-tone sweep input
Change
setting to Aided 2
Curve
4. Test FM+HA (set to FM only) with 90 dB SPL _______________sweep input
Compare
Curves 3 and 4
Adjust
max output of HA with FM Receiver Boot, if possible, to match HA _______________
Recall More Difficult Case,
Charlie
Severe to
Profound Hearing Loss (thresholds greater than 80 dB HL)
If the
typical use mode is FM+_______________
Then Set FM gain to match HA gain first with 65 dB SPL,
1000-Hz tone
Then give 80 dB Signal and adjust gain if output does not
increase by 10 dB
If
increase was: _______________ dB- Then reduce FM output by 5 dB
5 dB- Then _______________ the FM
volume by 5 dB
0 dB- Increase the FM _______________by
5 dB
Run
Frequency Response with complex signal
RHA65
RFM80
Compare
curves and be sure RFM80 is 10 dB higher than RHA65
Then
match outputs via 90 dB SPL sweep frequency pure tone signals
RHA90
and RFM90
(Demo -- Real Ear testing)
Then test
RFM90 and RHA90
EVALUATION
OPTIONS
A.
Audio-_______________ Checks
B.
Electroacoustic Measurements
Verifying Performance
Matching FMs to HAs
C.
Real Ear Evaluation
Matching FMs to HAs
D.
**Behavioral Evaluation**
Speech _______________
There are
two main reasons why it is
not advisable to do _______________ testing with the FM system.
The first one stems from the suggestion
to place the FM mic 6 inches from the
loudspeaker and place the child _______________ the booth
..
1) There
is too much _______________ in
vertical and horizontal dimensions
which may result in variability in
the _______________arriving at the FM mic.
2) In addition, the FM
systems may
operate differently for low level
signals than for higher level ones
like speech because of _______________.
THEREFORE
..
Threshold testing with the
FM system is not recommended!
Rather
.
Speech _______________ Testing
Hearing Aid alone
FM System
FM Only
FM+ENV
Mode
Test each
arrangement in _______________ and in Background noise if time permits
Select
appropriate test with _______________ lists
Set FM
and HA controls to user settings
Place FM
mic on examiner but turned off
Place HA
and FM receiver on Patient
Seat
Patient in soundbooth at _______________ degrees azimuth
Test
Conditions
HA-Quiet
(Speech at 55 dB HL)
HA-Noise
(Add Speech Noise at _______________dBHL)
HA&FM-Noise
(Keep levels, Turn _______________ FM Mic)
HA&FM-_______________
(Keep levels, Turn off noise)
Speech
Recognition Testing
Sample Scores
HA-Quiet 80%
HA-Noise 50%
HA+FM-Noise 85%
If score decreases
significantly, then FM gain too _______________
HA+FM-Quiet 80%
If score _______________
significantly, then FM gain too low
SUMMARY
Audiologist
is responsible for selection and fitting of FM systems and the necessary _______________
and _______________
FM
systems must be monitored on a regular basis by trained personnel under _______________
supervision
Fitting
goals for amplification via the ENV mic on FM systems do not differ from those
for _______________
The
additional goal for amplification via the FM mic is that the signal level and
S/N ratio _______________ be preserved
Audiologist
should confirm appropriateness of fit through _______________measures,
if possible, and/or electroacoustic and behavioral measures
Functional
gain measures are _______________as an appropriate technique to fit _______________systems