Frye FONIX FP40D - Manual (Page 97)

Real-Ear Measurements 89
5.3.5 Testing Open Fit Hearing Aids
Open fit hearing aids have been known to interfere with the reference microphone measurement
outside the ear. To determine if a particular hearing aid is interfering with the reference micro-
phone, perform the following measurement in the insertion gain screen. The feedback cancellation
and other features normally used by the patient should be enabled on the hearing aid.
1. Measure the aided response as described in Section 5.3.3.
• The sound field speaker should be LEVELED.
• The reference microphone setting should be ON. The reference microphone status is dis-
played in Status box.
• [F3] should be set to AIDED 1.
• The source amplitude should be set to 65 dB SPL. Use the Amplitude knob to adjust the
source if necessary.
• [F7] should be set to DIGSP ANSI or COMPOSITE.
2. Press [START/STOP] to start the measurement. Press [START/STOP] again when the measure-
ment has stabilized.
3. Use [F3] to select AIDED 2
4. Press [F1] to open the menu. Use the Amplitude and Frequency knobs to select REFERENCE
MIC under PROBE SETTINGS. Press [START/STOP] to change the setting to OFF. Press [F1] to
return to the Insertion Gain screen..
5. Measure the aided response as described in Section 5.3.3.
• The source amplitude should be set to 65 dB SPL. Use the Amplitude knob to adjust the
source if necessary.
• [F7] should be set to the source type used in Step 1.
6. Press [START/STOP] to start the measurement. Press [START/STOP] again when the measure-
ment has stabilized.
7. Look at the difference between AIDED 1 and AIDED 2.
If there is no more than 2 dB of difference between AIDED 1 and AIDED 2 at any frequency, you
can perform real-ear measurements using that particular model of open ear hearing aid without
adjusting the hearing aid analyzer. If the two measurements are different by 3 dB or greater at any
frequency, it is recommended to disable the reference microphone when performing REMs using
this type of device. To disable the reference microphone, follow the instructions found in Step 4
above.
When performing a real-ear measurement while the reference microphone is disabled, it is par-
ticularly important to make sure the patient doesn’t move after the sound field speaker has been
leveled because the reference microphone will not be able to compensate for any changes in the
patient’s position.