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Daqarta
Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
Science with your Sound Card!

The following is from the Daqarta Help system.
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Spectrum Averager Peak Mode

Controls: Spect Avg Dialog >> Peak
Macro: SpavgMode=Peak

This isn't really an "averager" mode at all. In this mode, the peak value is retained at each frequency, for as many frames as you have specified. Typically, you would set this value very high and terminate the operation manually by hitting the Pause button.

You can specify Continuous Peak mode by setting the frames request to 1. (A single frame wouldn't otherwise be useful.) In this mode the total frames display will continue to increase until it reaches 2147483647, after which it will show 'Cont Peak' instead of a number. Peak operation will continue until you hit Pause, or toggle Average off to abandon it.

A typical use for Peak mode is to generate a swept frequency response that appears on a single trace. You set a very slow frequency sweep to drive the system under test, and the Peak mode will record the maximum amplitude at each frequency. See Swept Frequency Response for details.

You should typically use a Flat Top spectral window function for this application, to insure accurate peak amplitude capture.

Another use is in determining how much noise a vehicle makes as it passes by at a fixed distance. You just start the "average", wait for the vehicle to pass, and then hit Pause to see the result. You don't usually need to worry about precise timing because the vehicle will be much louder than anything else at most frequencies, so the peak will only reflect that one source.

Peak mode is also ideal for looking at explosions, animal calls, music recordings, or anything else where you might want to know about spectral peaks but the source is not well-behaved or repeatable enough to use with a normal sync.


See also Averager and Spectrum Averager Controls.

Applications:

Frequency response

Distortion measurement

Speech and music

Microphone calibration

Loudspeaker test

Musical instrument tuning

Animal sound

Evoked potentials

Rotating machinery

Vehicle pass-by noise

Product test

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