I don't even remember what program I used to generate them. It's NOT NCH, because I just looked there. But basically you set a bottom frequency, an upper frequency, and a sweep rate, and it sweeps up and down between those too points at the rate you specify. Hmmmm, now that I think about it, I don't think I found a free program that could generate them, so I think I may have done them manually... a sweep down, a sweep up, insert one to the end of the other, then cut/paste it onto itself repeatedly. I dunno now, but I sure seem to have some vague memory of doing that.
Anyway, if you want to at least hear some, you can download the ones I generated here
. They are MP3s, which may not be as "pure" as you're looking for, but at least you can play with them. I probably have the unadulterated wavs somewhere.
The tracks with the "-" in between two numbers are the warbles... the bottom number being the bottom frequency, and the upper one the top frequency. Looks like they span 1/4 octave (it's been a while since I did these). When taking measurements using single frequency tones, I used 1/12th octave spaced tones (also in that zip). But I also wanted to take some full spectrum measurements, and 1/12th oct tones would have taken forever. Using the 1/4 octave warbles go a lot faster, but since they are sweeps, they cover "every" frequency.