FONIX® 8000 - Frye Electronics

Coupler Multicurve 55
3.2.2 Leveling the 8120 Polar Plot Sound Chamber
When performing Coupler Multicurve or automated test sequence coupler measurements
such as ANSI or IEC, it is not necessary to position the hearing aid in
the 8120 Polar Plot chamber on the rotating shaft. If desired, you can place the
8120 Removable Test Surface over the cavity and perform the coupler measurements
with the hearing aid placed on the basket. This procedure describes how
to level the sound chamber for this type of testing. If you are going to measure
the hearing aid with it placed on the rotating shaft, see Section 6.2 for leveling
instructions.
1. Place the 8120 Removable Test Surface over the cavity containing the rotating
shaft in the chamber.
2. Unplug any battery pill from the sound chamber.
3. Place the microphone on the test surface with the microphone grill over
the reference point at a 90° angle to the speaker in the back of the chamber
(Figure 3.2.2). Close and latch the sound chamber lid.
Warning: Leveling is valid only when the microphone position is not
changed after leveling. Each significant change in microphone location
requires new leveling. This includes positioning the hearing aid on the
rotating shaft for Coupler Directional testing.
4. Press [F1] to enter the Coupler Multicurve screen.
5. Press [LEVEL] to start the leveling sequence. The system responds by presenting
a complex composite signal consisting of tones from 100 to 8000 Hz.
It measures the signal and stores correction factors, so that the sound field is
flat for testing.
6. Look at the display. After a few seconds, the video monitor should display a
“Leveled” message under the Curve Characteristics box. If the FONIX 8000
Test System doesn’t level, it could be an indication that your microphone
needs to be calibrated or replaced.
Figure 3.2.2—Leveling the 8120 Polar Plot Sound Chamber with the removable test surface