[RainDawg]

Five, I believe the issue with your spectral plot is that it only shows the activity where your cursor is currently placed. The first one, it may have been at the beginning of the file where nothing was happening yet. When you clicked in the middle of the display, presumably to a spot there there is more "music", it suddenly shows you a more interesting plot.

One of the weaknesses with the freq analysis in CEP is that it will only display for one sample at a time, so even if you select a large portion, it will only display the information for the sample where the cursor is actually located. AnalFreq will run a progressive analysis, and display either the current position, or an average of what it has scanned so far.

This is why lossy stuff is so much easier to spot with AnalFreq than with CEP. Since the high end content on an mp3 file is just random noise, taking the average of it over an long period of time is going to result in a perfectly flat line, whereas each instantaneous plot (as in the pics above) is going to have some activity present. It will also accentuate that steep dropoff as it takes the average, making FM vs. MP3 much easier to definitively state. FM and TV have, as you said, a nice smooth rolloff when you take the average over the whole file.

I'm just not a fan of CEPs freq analysis tool, as it doesn't seem to really be useful for spotting sources as much. The Spectral Analysis tool is great though.