I know it changes it to a weird electric ping, and I know what changing the duty for other channels does, but what does it do to the waveform of the Noise channel? It seems that at low pitches it doesn't change much, and I can't notice a big difference in the waveforms.
it changes it from a staticky noisey sequence of 32767 steps of 1s and 0s, to a looped mode of a much shorter 93 step sequence. Apart from one being shorter than the other, the psuedorandom sequences are actually different too.
Yes, it's a "pre-recorded" noise pattern, which repeats over time. You can hear this quite well with the high frequencies. As the sound is going, it's going through this "recording" like the pages of a book. With the looped mode, you simply lock it to making sound out of just one page as opposed to reading through all of it.
Try enabling the electric looped mode then a bit of static, then electric again. You'll notice that the timbre is different because during the static it read through a bit more of that book, but then the looped mode made it repeat the same page over and over again.
