I have read the posts Below relating to the machine gun noise coming from my Sonos beam two.
Last night I had a very similar experience I had Which scared the life out of me my wife and cat.
The only way I could stop this was to unplug the HDMI and As it would not let me into the Sonos S2 app to control on yetpower cable, As it would not let me into the Sonos S2 app to control or mute.
Ccan the Sonos community or Sonos them selves please indicate what can be done to resolve this issue, I have had many issues since starting to use my beam two, correction failures Wi-Fi and compatibility changing Wi-Fi channels we are all tried to make the pairing of my new Sonos possible. The final result was me returning returning the first beam to back to the hi-fi retailer, where even the could not get the initial unit pair up for update.