For everyone's convenience, here's the work-around from CR 6885862 http://bugs.opensolaris.org/view_bug.do?bug_id=6885862
In B131 and later, "xset b off" cannot dismiss the system bell completely. To disable it completely, you can run $pfexec pkg install gconf-editor $gconf-editor then unselect the "/apps/metacity/general/audible_bell" checkbox. -- This message posted from opensolaris.org
