Hi there happy to help.
The way to do this should be as follows ........
Let me know,
If this answer helped you please click the ACCEPT button.
.Am in settings but no "start up" prompt
this means you need to do a firmware update on your TV.
Sony added this feature later.
You can get it here......
You'll notice in the description of the system software update that they added the option to turn this sound off.
Then see my instructions above.
the option will be there.
Hope this helps,
Thank you. Am in settings but no start up. Only start up I see is "network start up" which does not have a sound element in it!!
You need the update.
Then you will see it.
anything else I can clarify here?