Originally Posted by dann
OK, I did exactly that, to focus, in focusing on a shorter, more accurately representative sample of 2.31 seconds of duration:
Then in magnifying the "size" [Taille
] of the frequency spectrum from 1024 to 65536 [changing Audacity's language from French to English on the fly had a funny effect, which disappeared after a restart], which gave the following spectrum [screencapped]:
Lots of well defined peaks and harmonics in what appeared as an undifferentiated mound at low "sizes". Both 40Hz and 50Hz AC peaks and their harmonics (until ~240Hz) are present. And also 15, 17, 25, and 30Hz peaks (all those ± 2Hz).
The mound morphed into a fancy fractal.