Coupler Measurements 79
Figure 3.8.2C—Make the measurement
16. Press [START/STOP] to start the measurement. When it stabilizes, press
[START/STOP] to stop the measurement.
17. Press [F1] to select CRV 2.
18. Repeat Steps 9-10 to select the same source type and level as used for CRV1.
19. Press [START/STOP] to start the measurement. As it is running, slowing
rotate the hearing aid, maintaining the same distance from the sound field
speaker. The response of the aid should gradually diminish as the sound
field enters the directional aid’s “null” spot. When the response is at its min-
imum level, press [START/STOP] to stop the test.
20. Compare CRV 1 and CRV 2. See Figure 3.8.2D. If the hearing aid’s response
didn’t change when you rotated the aid in Step 15, it is a very good indica-
tion that the aid’s directional microphones are not working properly.
