Disable sound during sound volume adjustment

[Tancredi Orlando <turlando mlist gmail com>]

Hello everyone,
I've never used mailing lists and this is my first post here, I hope I
won't make mistakes.
When you adjust the system sound volume, Gnome plays a sound; in Mac OS
X happens the same thing, but you can mute this noise if you keep
pressed the shift key. This is a very cool feature because if you are
listening to music or watching a film, hearing other sounds could be
very annoying.

Thanks for your attention,
Tancredi Orlando.