Unplug everything. Unplug every cord from every end. Then plug it all back in. This way you can rule out loose connections as a potential cause.

Is your bedroom the only place you hear this? Test the same electronics in other rooms (or even at someone else's home) to make sure.

Are your current electronics the only electronics producing this noise? Buy/rent/borrow similar electronics that have never been in your home before and test them in both the bedroom and other rooms to be sure.