Hearing Aid User Manual

170 FONIX 7000 Hearing Aid Analyzer
6.9.2.2 BI-CROS
Unaided—Measurement of “better” ear canal (baffled by head)
Set up the 7000 test system as follows.
• Reference microphone ON
• Sound field LEVELED
• Unaided set to CUSTOM
• Reference microphone over pinna
of “bad” ear
• Probe microphone inside ear
canal of better ear
• Hearing aid in better ear, on, set
at use gain
• Transmitter on bad side turned off
• Loudspeaker at 90º, 12 inches
from bad ear
Aided—Measurement of “better” ear
canal (baffle overcome by aid)
Same setup as above, except
• Transmitter on bad side turned on
The difference curve, labeled “Insertion Gain” on screen, shows the benefit of
adding the second microphone for sound arriving from the “bad” side.
6.9.3 Measuring Overall Insertion Gain
The methods for measuring the overall insertion gain of CROS and BICROS aids
are described in this section.
Since it has not been shown for CROS and BI-CROS instruments that a 45º
position of the loudspeaker improves the reliability of insertion gain measure
-
ments, we recommend a 45º position of the loudspeaker only for monaural
instruments, and a 0º position for CROS and BI-CROS instruments.
REFERENCE MIC
PROBE MIC
12"
BETTER
EAR
BAD
EAR
SPEAKER