Hello,
I have the same problem described in the two links below. A surround system with one Beam and two One SL. When no sound is coming to any of the two One SL (either because of no source or low volume) I can hear a humming noise.
Any idea what the solution could be?
Thanks,
Rudolf
https://en.community.sonos.com/troubleshooting-228999/sonos-one-humming-6818353
https://en.community.sonos.com/troubleshooting-228999/sonos-one-speakers-humming-noise-6847593