Using the FONIX 7000 to Verify Coupler and Real-Ear Performance ...

Real Ear Measurements 54
Note… Verification of the feedback feature requires three measures. The first measure is to
determine the Maximum Stable Gain with the feedback feature off (MSBFBoff). The second is
Maximum Stable Gain with the feedback feature on (MSGFBon). The final measure is Added
Stable Gain (ASG) which is simply MSGFBon (-) MSBFBoff. ASG documents the amount of
additional gain provided to the patient with the activation of the feedback feature. MSGFBoff is
measured by increasing the overall gain of the hearing aid until the spectrum analysis as shown
in Figure 70 is illustrated on the monitor. At this point, the clinician would reduce the gain by 1
dB or until the spectrum analysis as show in Figure 68 is reported. This measure provides the
clinician with a “picture” of the “maximum” output of the aid available prior to the presence of
feedback. Now, the clinician activates the feedback feature and repeats this measure
(MSGFBon). If the feedback feature is effective, then the MSGFBon will report greater output than
MSGFBoff and the difference between these two measures (ASG) is the effectiveness of the
feedback feature in providing the patient with greater useable gain/output.
2.12 Measuring the real-ear attenuation of a hearing protector device.
STEP-BY-STEP
Figure 71 – Real ear attenuation of a foam earplug
1. From the Opening screen, press [F2] to enter the Real Ear Navigation screen.
2. Press [F3] to enter the Insertion Gain screen.
3. Set the patient up for real ear measurements as described in Section 2.1.
4. Press [LEVEL] in order to calibrate the sound-field speaker and the reference
microphone.