How to turn off menu sounds?

This may be a stupid question, but how do you turn off the annoying menu sounds? Especially the snare when you press enter? Looked in the Graphics/Sound Options page but didn't see anything.

Also, why are these even on by default? They really tasteless and remind me of 90s web sites. Same goes for the default theme.

Sounds are theme specific. What theme are you referring to with the annoying snare?