I'm currently using Dapper (xubuntu). In the System Menu, I can see a Login Window item. I selected that, and in the Accessibility tab there's a Sounds section where you can disable the sound. To lower the volume, you may use any volume control app but what I usually use is aumix.
** Changed in: gdm (Ubuntu) Status: Unconfirmed => Rejected -- Drum sound too loud and can't be disabled https://launchpad.net/bugs/54767 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs