Hi. I would like to export the envelope (Level vs. time) of the waveform to an XY file so that I can compare different recordings in Excel. It doesn’t have to be high resolution. This seems like it should be trivially easy, but I haven’t figured out a way to do it.
I have tried Sample Data Export, which looks like what I want to do, but when I plot the resulting data, it just looks like noise. It doesn’t resemble the waveform view at all.
Any help would be appreciated.
A Google search of “waveform to Excel” reveals several programs written expressly for that purpose.
The reason for that is because “Sample Data Export” exports the values of each sample. If you zoom in very close on a waveform, you will see that it is comprised of discrete points in rapid succession - by default there are 44100 samples per second.
I’m guessing that you want to see the “shape” of the waveform over longer time periods (as you see at normal zoom levels.
One thing to consider is that waveforms are not always vertically symmetrical, though in most cases the positive side of the waveform is close to a reflection of the negative going waveform. If we assume that the waveform is symmetric, then we can do a special kind of resampling, to capture the absolute maximum value at intervals that are much longer than the sample rate. For example, we can look at the maximum (either positive or negative amount) for each interval of 4410 samples (1/10th second).
This code, when applied to a track using the Nyquist Prompt performs the kind of “resampling” that I’ve described:
(setf step (truncate (/ *sound-srate* 10.0)))
(s-avg *track* step step op-peak)
Note that the processed track is MUCH shorter than the original. Use “Ctrl + E” to zoom in on the processed audio (Zoom to selection).
Now that the “shape” of the audio has been reduced to one sample per 1/10th second, you can now use “Sample Data Export” to export the values of each point to a text file.
Thank you so much! That is perfect! Exactly what I was looking for!
Now I just have to learn what all of the Nyquist commands mean. 
A good list of documentation is on my blog here: Documentation | AudioNyq
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