EDIT: Do note, though, that each process pulling audio will be denoising independently, so the usage scales linearly with the amount of clients. This is due to how ALSA plugins work, but regardless of that, on a Ryzen 5 1600x (the only CPU I can test on), the plugin uses 2.5% of a single core when recording mono 48k
I'm testing this right now and am noticing that some more info about the installation could be helpful. Specifically, when installing rnnoise as shown in the readme it of course goes to /usr/local/lib, but /usr/local/lib/pkgconfig was not in the PKG_CONFIG_PATH of my distro. Maybe there could be a hint to set that when calling `meson build` if rnnoise can't be found?
Packaging software is always annoying, sorry for dragging you into that mud. Ideally distros will pick it up and compiling manually unnecessary. I would have left this as an issue but saw no issue tracker on the project page.
As for packaging, that's my field of work for some projects I'm working on so it's not unfamiliar to me, the only problem is that the RNNoise upstream lacks releases, although there's discussion about something happening about that.
With extreme sounds (vacuum) in the background the voice gets a bit more distorted than ideal, but something like a keyboard gets filtered nicely to be less noisy. I assumed that's just how RNNoise behaves, I'm just mentioning it because of the sound quality discussion above. Maybe also to that: Just activating the alsa_rnnoise filter does not significantly lower recording quality, at least not that I can notice.