FONIX® 8000 - Frye Electronics

132 FONIX 8000 Hearing Aid Test System
6. Manually rotate the hearing aid (attached to the shaft) in a clockwise manner
so that a line made between the two microphones of the hearing aid point
directly towards the speaker in the back of the chamber. The forward microphone
of the hearing aid should be closest to the speaker, and the point halfway
between the two microphone should be over the part of the rotating shaft
that plug into the sound chamber (the axis of rotation). The faceplate of the
hearing aid should be perpendicular to the speaker. See Figure 6.3.2C. During
testing, the hearing aid is rotated counter-clockwise, so this type of positioning
should ensure the microphone cord is not tangled during testing.
Figure 6.3.2C: Setting up an ITE hearing aid in the 8120 Polar Plot Chamber
6.4 The Directional Polar Test
You can perform polar plot testing of directional hearing aids in the Directional
Polar test screen. The polar plot is a display of the gain or SPL at a single frequency
of the hearing aid response as a function of its angular position with
respect to the sound source. Eleven different polar plots can be displayed on the
Polar Plot graph at any one time. Each plot can also be displayed in tabular format
with the level (gain or SPL) and the angle of each measurement.
6.4.1 Viewing the Directional Polar Display
The Directional Polar test display consists of a polar plot graph, a Curve
Characteristics box displaying information about the source frequency and the
Directivity Index (2D-DI) of each polar plot curve, and a Settings box displaying
the test conditions and signal characteristics used for the selected curve and the
current test configuration.