I have a 50

Bees!

This may be too broad to answer because of insufficient explanantion.

Does it BUZZ when not on a channel... an untuned channel or the DVD channel without a DVD playing.

Is it some patrt of the chassis or plastic surround that is vibrating with the volume level.
There are electrical components that will buzz.. (relays ) when they are failing or being overloaded.

So despite being a seemingly simple question, it is more involved than at first glance.

Test some of the things mentioned.. off channel to see if it still buzzes.. put pressure on varios parts of the case to detect loose fitting cover etc.

If you want to risk it open cover and see if you can at least locate the region of the sound on its internal boards. Be carful with this though as it is HIGH Tension Power and is dangerous. Check the simple ones first and then call a service person or someone with electrical knowledge to check the inside.

Thanks for using FIXYA kindly rate my help