I posted about my Arotherm 7kW compressor noise issues (see Vaillant maximum output capacity testing - #132 by Plug1). Of course, the noise in the video is a lot louder due to the side panel being removed, but the main observation was that there was a qualitative change at higher frequencies due to resonance in the compressor assembly.
To follow up on this, a Vaillant engineer tried to fix this (under warranty) and had partial success. The slightly disappointing thing is that he started to apply quite a bit of noise-suppressing tape around the compressor before observing it running at high speeds, so did not find the root-cause of the problem. The outcome was that noise is now a lot quieter at very high speeds (90-120 rps), but there is still some noticeable resonance in the 75-90 rps which can be heard inside at certain places in my house close to the main flow and return pipes. Having seen what the Vaillant engineer did, I can probably improve this further. BTW, I find this app (https://play.google.com/store/apps/details?id=org.intoorbit.spectrum&hl=en_US&pli=1) very useful for monitoring the noise that is definitely coming from the compressor, as you can pick out the precise frequency that matches the compressor speed (e.g. 88rps will show up as a 88Hz spike in the app).