FONIX® FP35 Touch - Frye Electronics

38 FONIX FP35 Hearing Aid Analyzer
aids have become more sophisticated and better able to handle loud signals, making
harmonic distortion a more useful measurement at 90 dB SPL. The DIST 90 dB
RULE is still available, but we have turned it OFF by default.
Definitions
• 2ND Harmonic: Energy of the second harmonic or twice the presented frequency.
• 3RD Harmonic: Energy of the third harmonic or three times the presented
frequency.
• TOTAL: Combined 2ND and 3RD harmonic distortion.
2.5.1.3 Noise Reduction
Noise reduction is used in noisy testing environments. Pure-tone noise reduction
takes several measurements at each frequency and averages those measurements
together. Larger noise reduction numbers lead to smoother curves but increase the
amount of time it takes to complete a pure-tone sweep.
For example, if you select “4” as the pure-tone noise reduction setting, 172 measurements
(43 x 4) will be taken with every normal pure-tone sweep
2.5.1.4 Warble Rates
When you take pure-tone measurements in a sound field environment, it is useful
to warble the tones to reduce standing wave effects and create more accurate measurements.
(Warbling is not usually necessary in a sound chamber testing environment.)
The FP35 analyzer allows you to change the warbling rate of its pure-tone signals.
You do this by altering the WARBLE SOURCE selection in the Custom Menu of
the Coupler Multicurve Screen and the Real-Ear Measurement Screens. The USER
LEVEL must be set to ADVANCED. See Section 2.3.2.
Some types of warbling can cause problems when used to test digital hearing aids.
This is because the digital processing delay of the aid conflicts with the warbling
timing. We have altered our SLOW warble signal to account for this problem. This
type of warbling is automatically selected during real-ear measurements when the
AID TYPE is set to ADAPTIVE in the local menu of the measurement screen.
Here is an explanation of the available warble selections:
• FAST is usually used in real-ear measurements. In all screens except the
Audiogram Entry Screen, it warbles at a rate of 33 Hz. In the Audiogram
Entry Screen, it warbles at a rate of 20 Hz, ±5% deviation from the central
frequency.
• SLOW is used for testing digital hearing aids and for audiometric measurements.
It warbles at a rate of 6.25 Hz, ±5% deviation.