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FFT Analysis - needs more resolution and another zoom level (or two)...


ChrisVH

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Hello. I really like the FFT analysis in Wavepad, but would like to see higher resolution in the X axis. When zoomed-in to highest resoultion, it still isn't enough to plot exact frequency of specific peaks. It appears the software is not correlating the measurement correctly- as is listed in Hz, and "note" in upper right corner, when cursor is placed on the frequency peak. Looking at the div lines these frequencies displayed are not matchng with the position on X axis, within each division (I am not using the logatithmic scale, to gain highest resolution).

 

Are there plans to increase this funcitonaility, or can you confirm that the peaks as shown in the graph are plotting exactly to the graph (example 50% between divs = 50% of the value)?

 

Lastly, the extreme low frequencies (under 100 Hz) need more separation. I am trying to identify fundamental notes below 60 Hz or so, and this software is bunching everything up in that area...

 

So, it's a long question, but the bottom line is I NEED another 1 - 2 levels of zoom function, at least on the X axis...., and the frequency listed in the upper right corner should be gapless (1 Hz precision) when moving cursor along X axis, and displaying that value. There are big gaps now.

 

Please advise.

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Guest Alex Chapman

Hi Chris,

 

For the FFT window, WavePad currently uses a 4096-sample window when performing the FFT. This means that it has a resolution down to about 10Hz if your file has a 44100Hz sample rate (a quick way to calculate this is to divide the sample rate 44100 by 4096). But here's something that may help you: WavePad uses this 4096-sample window regardless of the file's sample rate. So to increase the resolution you can just decrease the sample rate of the file: A 16000Hz file will have a resolution of 16000 / 4096 ~= 4Hz. Just be aware that the lower sample rate will reduce the maximum sound frequency that can be represented (16000 / 2 = 8000Hz maximum frequency).

 

In case that wasn't clear, if you don't care about frequencies above 3000Hz, and you want a frequency resolution of around 1.5Hz, then you can do this:

  1. Load your file,
  2. Convert the sample rate to 6000,
  3. Use the FFT tool.
  4. When you're done, close the file without saving or use Undo to change back to the original sample rate.

Alex

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