Frye FONIX 7000 - Manual (Page 88)

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FONIX 7000 Hearing Aid Analyzer
is in a vertical position. If necessary, use Fun Tak to help hold the aid in
that position. See Figure 3.4.10B.
5. Use [∧, ∨] to change the intensity of the magnetic field. The choices are:
OFF, 1.00, 1.78, 3.16, 5.62, 10.0, 17.8, 31.6, 56.2, and 100 mA/m. 31.6 is the
default source intensity.
6. Press [STOP] to stop the measurement or continue to test, as desired.
Figure 3.4.10B—Testing with the Telewand
3.4.11 Measuring directionality
Although directional hearing aids can have different types of polar maps and
two or even three microphones, the basic concept is fairly simple: speech sound
from in front of the hearing aid wearer is louder than noise from behind him.
The FONIX 7000 hearing aid test system cannot give you a polar plot of the
directional hearing aid response, but it can provide you with the basic informa-
tion of how much directional benefit the hearing aid wearer is receiving and at
which frequencies.
The directional test takes advantage of the speaker placement in the large sound
chamber and the flat testing surface that makes it easy to position the hearing
aid for testing. There are two measurements: one where the hearing aid is posi-
tioned so that it is facing towards the sound chamber speaker, and one where
the hearing aid is positioned so that it is facing away from the sound chamber
speaker. You should use the same input signal for both measurements. The
source amplitude used for this measurement should be greater than the noise
floor of the testing environment but less than the compression knee point of the
hearing aid, if possible. 50 dB SPL is usually a good choice.