162 FONIX FP35 Hearing Aid Analyzer
5.9 CROS, and BICROS
When using the FP35 probe with a CROS or BICROS aid, we suggest the follow-
ing setups and procedures.
Four Goals:
5.9.1 - Measuring the Head Baffle Effect
5.9.2 - Measuring the Overcoming of the Head Baffle Effect
5.9.3 - Measuring the Overall Insertion Gain
5.9.4 - Measuring the Insertion Loss to the “Good” Ear
Each of these measurements uses the insertion gain measurement technique,
taking advantage of the fact that the insertion gain is a difference curve between
two measured curves (usually the unaided and aided response). The techniques
assign the label of “unaided” to one measurement and a label of “aided” to
another measurement.
Take all measurements in the Insertion Gain Screen. For measurements labeled
“Unaided” (even if they aren’t unaided) follow the instructions in Section 5.4.2.
For measurements labeled “Aided” (even if they aren’t aided) follow the instruc-
tions in Section 5.4.4.
5.9.1 Measuring the Head-Baffle Effect
The measurements described in this section are for both CROS and BI-CROS
hearing aids.
Unaided—Real-Ear response on “bad ear” side
Set up the FP35 analyzer as follows.
•SystemUNLEVELED
•ReferencemicrophoneOFF
•UnaidedCUSTOM
•Probemicrophoneoverthebadear,tube
jutting just slightly forward of pinna
•Loudspeakerat90º,12inchesfrombadear
Aided—Real-Ear response on “good” ear side
Same setup as above except:
•Probemicrophoneoverthegoodear
The difference curve, labeled “Insertion Gain”
on the screen, shows the attenuation of sound
arriving at the good ear from the bad ear side.
Since this measurement excludes the external
ear, differences across individuals should be minimal.
12"
PROBE MIC
SPEAKER
GOOD
EAR
BAD
EAR
12"
PROBE MIC
SPEAKER
GOOD
EAR
BAD
EAR
