turning off the dialog sound effect in Thunderbird

[Adam Funk]

At some point recently (possibly when I upgraded to Ubuntu 13.10),
Thunderbird has started playing that awful drumbeat sound [1] with
every dialog box that pops up.  I've looked in the GNOME sound
settings (I'm using gnome-flashback-session), the Thunderbird
about:config, & on the WWW.  The only solution I've actually seen
involves deleting the file from /usr/share/sounds/ubuntu!

Any suggestions?

Thanks,
Adam



[1] Yes, the same annoying one that lightdm plays & that the
    developers won't make it easy to turn off there.