5.11
How to test the directional microphone
Directionality measurements as described in the hearing instrument test standards cannot be performed with regular desk-
top test chambers such as Aurical® HIT. Such measurements require large anechoic chambers. Small test chambers always
exhibit acoustic reflections that obscure the true directional behavior of the hearing instrument.
However, in Aurical® HIT you can make a functional test of the directional microphone in a hearing instrument. In this test,
the signal is first presented to the front of the hearing instrument and then to the back of the hearing instrument. This is
done automatically when you start a directional test. The signal used for this test is a flat spectrum Broad Band Noise, band-
pass filtered between 750 Hz and 5 kHz, and presented at 70 dB SPL.
The procedure
1. Position the hearing instrument as described in
Traditional BTE hearing instruments
,
and
depending on the type of hearing instrument.
2. In the field
Directionality Adaptation
(Directionality Adaptation) in the Otosuite HIT module, you can define the dur-
ation of the signal presentation before the actual measurement is made. This value accommodates any adaptational
behavior of the hearing instrument. Adaptive directionality often takes 10 to 15 seconds or more before the dir-
ectionality of the hearing instrument is fully efficient.
3. You can either combine the
Directional Test
(Directional Test) with your standard test sequence by checking the
sequence checkbox, or run it separately by clicking the
Start
(Start) button.
The result
The
Directional Test
(Directional Test) result is shown as a 1/3 octave curve of the difference between the measurement
with noise presented from the main loudspeaker and the measurement with noise presented from the rear loudspeaker.
The numerical directionality result shown in the
Measurements
(Measurements) table indicates the average front/back
difference in the measured frequency range.
The
Measurements
(Measurements) table also includes the adaptation interval used in seconds.
6
Maintenance and Calibration
Warning
•
Under no circumstances disassemble Aurical® HIT. Contact your supplier. Parts inside Aurical® HIT
must only be checked or serviced by authorized personnel.
Calibration
Calibration of the coupler microphone, and calibration of a new reference or coupler microphone must only be performed
by authorized personnel.
Maintenance
Aurical® HIT requires no preventive maintenance except for cleaning and regular calibration of the reference microphone.
Repair
For any type of repair, please contact your supplier.
16
Aurical HIT
6 Maintenance and Calibration
Summary of Contents for Aurical HIT
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