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
in the OTOsuite HIT module, you can define the duration of the signal present-
ation 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 directionality of the hearing
instrument is fully efficient.
3. You can either combine the
Directional Test
with your standard test sequence by checking the sequence checkbox,
or run it separately by clicking the
Start
button.
The result
The
Directional Test
result is shown as a 1/3 octave curve of the difference between the measurement with noise presen-
ted from the main loudspeaker and the measurement with noise presented from the rear loudspeaker. The numerical dir-
ectionality result shown in the
Measurements
table indicates the average front/back difference in the measured
frequency range.
The
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
Otometrics - AURICAL HIT
6 Maintenance and Calibration
