Larson Davis System 824, Reference Manual

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11-4 824 Reference Manual 11/2/00
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FFT Repeat
Once the average count is completed you can choose to con-
tinue repeating the FFT or have the FFT stop.
• No - Stops the count when the average count has been
reached.
• Yes - Repeats the count continuously.
Window
The Hanning window is typically
used for most measurements. The time weighting window can be the following:
• Rectangular
• Hanning
• Flat-top
The Rectangular window provides the best frequency dis-
crimination but can have significant filter leakage or effects
of a truncated series. The Hanning window minimizes the
filter leakage with the cost of a wider main lobe. The Flat-
top window gives better amplitude accuracy in the passband.
Overload Skip
Overload skip allows you to throw away or keep spectra that
contain overloaded data.
• No - Averages in spectra with overload data.
• Yes - Does not average spectra in that contains over-
loaded data.
Transducer
When a condenser microphone is
used, the 824 requires a stablization
time of approximately 45 seconds
before a measurement can be taken. • Condenser - This indicates that the microphone being
used is an air condenser type and the 824 will generate
the appropriate polarization voltage.