Page 25 addresses this, and the feature is called the "Melody"
Melody; Off / Low / Medium / High
A melody sound can be set to come on when the TV is powered On or Off.
It can be found in the SETUP Menu.
Does that help?
I just got a new Samsung and I love it - except for the startup and turn off sounds. I see on the forum there is a way to disable these sounds on other models - is there a way to turn these off on the 540?