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Verifit User’s Guide Version 2.8
Page 66
12.2 REM directional testing
FastFacts 12.2: REM directional testing
Best results are obtained for this test if an external front REM speaker is used in
place of the internal REM speakers because this eliminates sound reflections from
the display screen and test chamber lid. See
10.2: External REM speaker setup
.
1)
Refer to
10: Real-Ear Measurement Setup
to prepare the system for use and
for proper positioning of the client and the probe tube.
2)
Insert the earmold or custom hearing instrument into the ear, being careful not
to advance the probe tube further into the ear canal. A lubricant applied to the
earmold or custom instrument shell in the vicinity of the probe tube will make
insertion easier and prevent slit leaks around the tube.
3)
Press <Tests> then highlight and <PICK> [Directional] from the REM tests list.
4)
Highlight and <PICK> button 1, 2, 3 or 4 in the REAR column. Test signals are
presented from both speakers and two real-time curves appear on the screen.
The heavier one is the response to the front speaker signal and the lighter one
the response to the back speaker signal.
5)
On the Test control poster, highlight and <PICK> [Level], then highlight and
<PICK> a level from the list box. Switch the instrument between non-directional
and directional mode and observe the curves change from nearly identical to
two well-separated curves.
Adaptive
systems become directional at levels from
45 - 70 dB SPL so vary the level to observe the change in curve separation.
Some systems take several seconds to respond to changes in level and both
curves may change with time.
Verify that the lighter (back) curve is well
below the heavier (front) curve
over much of the frequency range.
6)
Press <Continue> to capture curves. Curves are labeled
F
(front speaker
response) and
B
(back speaker response) followed by the test number (1 - 4).
Because the REM reference microphone is close to the hearing aid, no head
shadow effect will be observed by moving the rear speaker to the inactive side.
