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FONIX FP40 Portable Hearing Aid Analyzer
3.4 Frequency responses
The Main Coupler Screen lets you take the frequency response of the hearing aid. You can:
• Use a variety of signal sources
• View multiple responses at once
• Find the single frequency response of the aid
• Take a three frequency average
• View the harmonic distortion in bars or in a separate table
• Switch between viewing curves in output and gain
• Test with or without the reference microphone
This section will tell you how to do all of these things.
3.4.1 Choosing a source type
The first step in taking a frequency response is to choose the signal you will be using as a source.
The sources available on the FP40 analyzer are described in Section 2.4.
To select a pure-tone source:
1. Press F1—MENU to enter the General Setup Menu.
2. If you have the Composite signal, you will see the item SOURCE as the first item in the left
column. If you don’t see this selection, skip to step 3.
a. Select SOURCE with the FREQUENCY and AMPLITUDE knobs.
b. Push START/STOP to select TONE.
3. Select SWEEP TYPE with the FREQUENCY and AMPLITUDE knobs in the middle column of
the screen. See Figure 3.4.1.
4. Select the desired pure-tone sweep type using START/STOP. In general, select NORM to per-
form a single sweep containing many frequencies. Select FAST to perform continuous sweeps
containing fewer frequencies.
5. Press F1—EXIT to return to the Main Coupler Screen.
