I don't have any solutions for you, but to help those who might ...
Do you hear this humming coming from the Roku itself, or is it coming through the TV (and/or sound system) speakers?
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X