One thing to perhaps try, is to see if using the speaker in a different power socket elsewhere in the Home makes a difference as it might (possibly) be an ‘earth’ issue on the power supply that’s causing the noise.

It can be the case that Sonos Staff may not get to see your post here, particularly over a weekend period, so if the problem persists, you perhaps may find you get better success by speaking/chatting to Sonos Support online via this LINK. HTH