Frye FONIX 7000 - Manual (Page 180)

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FONIX 7000 Hearing Aid Analyzer
6.9.4 Measuring Insertion Loss to the “Good” Ear (CROS)
The method for measuring insertion loss in the patient’s “good” ear is described
in this section. They are the same for CROS and BICROS hearing aids.
When a CROS aid has been prescribed to overcome a severe unilateral high-fre-
quency loss, you may want to ensure that inserting an open ear mold into the
good ear has not significantly attenuated the acoustic transmission to the good
ear.
Since this is a monaural measurement, a 45º position of the loudspeaker is rec-
ommended.
Unaided—Unoccluded Ear canal Response of “good” ear
Set up the 7000 test system as follows.
• Reference microphone ON
• Sound field LEVELED
• Unaided CUSTOM
• Reference microphone over pinna of
good ear
• Probe microphone inside unoccluded
ear canal of good ear
• Loudspeaker at 45º toward good ear, 12
inches from surface of head
Aided—Occluded Response of “good” ear.
Same setup as above except
• Earmold in place in good ear
• Hearing aid is turned off
The difference curve, labeled “Insertion Gain” on screen, shows insertion loss, if
any, caused by inserting the earmold into the good ear.
REFERENCE MIC
PROBE MIC
12"
SPEAKER
GOOD
EAR
BAD
EAR