FONIX® FP35 Touch - Frye Electronics

General Operation 39
• OFF turns off all pure-tone warbling in all measurements.
• AUTO makes the following warbling selections:
- OFF for all sound chamber measurements and real-ear measurements
made with NORMAL or SHORT pure-tone sweeps.
- FAST for real-ear measurements made with either a FAST pure-tone sweep
or SINGLE pure-tone with an AID TYPE of STANDARD or AGC.
- SLOW for real-ear measurements made with either a FAST pure-tone
sweep or SINGLE pure-tone with an AID TYPE of ADAPTIVE.
2.5.1.5 Adjusting the Signal Skew
The SIGNAL SKEW selection, available in the Custom Menu of several measurement
screens, is the number of samples from when the source signal leaves the
speaker and when it is measured by the microphone. (The USER LEVEL must be
set to ADVANCED. See Section 2.3.2.)
The amount of time it takes for a sound signal to travel from the speaker, through
the hearing aid (or device being measured), and to the ear or coupler, where it is
measured by the FP35’s microphone, varies naturally depending upon the distance
of the FP35 microphone from the speaker and the amount of digital processing
delay inherent in the hearing aid. This time delay is normally so small that
it does not affect the quality of the hearing aid measurements. However, some
digital hearing aids have a signal processing delay significant enough to make this
amount of time more meaningful.
A warbling pure-tone signal, in particular, is dependent upon the FP35’s ability to
synchonize the source signal and the measurement processing. When the hearing
aid adds additional delay through its internal signal processing, it can throw the
FP35’s internal synchonization off. The SIGNAL SKEW menu item lets you adjust
for this delay by specifying the number of samples between the source emitting
the signal and the FP35 processing it. There are 39 uS (microseconds) in each
sample for 100 Hz-interval frequency. The SIGNAL SKEW selection is applied to
all source types, but it should only have an effect on pure-tone measurements.
2.5.1.6 Three-Frequency Averages
Three-frequency averages are usually performed within an automated test
sequences. When the USER LEVEL is set to ADVANCED (see Section 2.3.2), you
can also perform them from within the Coupler Multicurve, Target Coupler, or any
of the real-ear measurement screens. The three frequencies that are used to perform
the average measurements are chosen in a menu selection and represented
by the last frequency of the three-frequency average. Here is a complete listing of
the available averages.