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Old 08-11-2006, 02:29 PM
amandawaack amandawaack is offline
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Join Date: Aug 2006
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Default Power Spectra Calculation - Comparing "old" method with "new" Raven 1.3 method

Raven 1.3 introduces a slight change in the calculation of power spectra. The new method includes energy in the negative frequency bins of the Discrete Fourier Transform (DFT), and normalizes the power spectrum by the number of points in the DFT window. The power spectra calculation method that Raven 1.3 uses can be changed by editing Raven’s preferences file.

Also, the performance of the two power spectra calculation methods can be compared by simultaneously. This process of opening two instances of Raven (one using the Raven 1.3 (new) method and the other using the Raven 1.2 (old) method) is explained in detail below.

To compare the two power spectra calculations in Raven:

1. Start Raven 1.3. This instance of Raven 1.3 will continue to use the current method, which in most cases will be the one that was chosen the first time that Raven 1.3 was started.

2. Open (from the Windows menu) the Raven preferences file: Start > Programs > Raven 1.3 > RavenPreferences.txt

3. Scroll to the last line of the text, which should read as either:

raven.compatibility.computation.spectrogram=1.3
or raven.compatibility.computation.spectrogram=1.2

This statement indicates the power spectra computation method that Raven is currently using.

4. Change the version number 1.3 to 1.2, or vice versa. This change will affect only the power spectra computation method.

5. Save and close RavenPreferences.txt

6. Leaving the first instance of Raven 1.3 open, open a second instance of Raven 1.3.

7. The previous preference settings will continue to apply to the first instance of Raven 1.3 as long as it remains open. So, it uses the power spectra computation method that was set previously, while the second instance uses the power spectra computation method that was just set.

Using the current Raven 1.3 power spectra calculation in one instance, and the earlier Raven 1.2.x power spectra calculation in the other instance, open the same file in each and view them simultaneously.

Last edited by amandawaack : 03-29-2007 at 12:33 PM.
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