This has happened randomly for the past 4-5 months now, I normally play videos to fall asleep to, like a calming thunderstorm and the 'turn on' noise will play at full volume over my thunderstorm video. It happens randomly as I can go weeks without hearing it then randomly as I walk out of my room, as I fall asleep, or as I wake up.
At first I thought it was a glitch, but while trying to look up what was going on showed that nobody else had/has this problem. I'm not 100% sure what roku tv I have considering I've had it for 10-11 years. It still works great, just hearing the 'turn on' sound randomly. If anyone has any ideas or solutions, please let me know. Thanks!