I’ve seen a bunch of similar posts re this issue but thought I'd give it a shot just in case a solution was now known:

Playbar was packed up (safely and fully protected) for a few months between moving house. Having installed in new home, there is now a constant high pitched tone when tv is off/muted and player should be idle (there normally is a delay before the high pitched noise creeps in). 

Have tried factory-resetting and power cycling without any success. Can anyone advise on solution or should I go straight to reporting (the auto-chat bot doesn't present suitable options for this problem,. annoyingly)? 

Thanks guys!