FONIX® 8000 - Frye Electronics

Real-Ear Measurements 181
to change the speech weighting:
1. Press [MENU] from a real-ear measurement screen.
2. Use [, ] to select Composite Filter under Source.
3. Use [, ] to choose ANSI or ICRA.
4. Press [EXIT] to return to the real-ear measurement screen. Any Digital
Speech or Composite signal will use the new selected speech weighting.
Figure 8.5.2—A comparison of an aid being tested with Digital Speech using the ICRA (CRV 3)
and the ANSI S3.42 (CRV 2) speech weightings
8.5.3 Testing the digital filters
It is possible to add a bias tone to the Digital Speech signal in order to see how
the aid responds in the presence of noise at different frequencies. This is useful
for checking the filters of the hearing aid and determining how one channel of
the hearing aid reacts to noise in a different channel of the aid.
to introduce a bias signal in a measurement screen:
1. Enter the Real-ear Insertion Gain or Real-ear SPL screen, set up the patient
for real-ear measurements, and level the sound field speaker.
2. Select the Digital Speech signal source with [F5].
3. Press [MENU] to enter the local menu.
4. Select Bias Tone under Source using [, ].
5. Use [, ] to select the level of the bias signal. Choose from 40-90 dB SPL
in 5 dB steps.
6. Press [EXIT] to return to the measurement screen. The Digital Speech signal
will now include the pure-tone bias signal.
7. Press [START] to start the measurement.
8. Use [, ] to change the frequency of the bias signal. Notice how the aid
reacts when the bias frequency is changed. Some hearing aids don’t react at
all to the bias while other aids react dramatically. See Figure 8.5.3.