Comment 68 for bug 437429

Those seeking a GUI workaround, there is a solution! You just need to
pick a different sound theme. Unfortunately there's next to no
selection, but you can install the package sound-theme-freedesktop
(the one Fedora uses), which is VERY tastefully done. Ubuntu's is a
tad out of date vs. Fedora (no pop sound when you adjust volume,
mainly), but the login sound is recorded at a sane volume and a bit
shorter.

Right now there's a big chunk of GUI to configure the alert sound from
the sound preferences. Seems a bit arbitrary; definitely could use
some review to decide which sound options are most important to
people. Maybe a nice way to fix this would be to identify the priority
of sounds done via Canberra and give the user an option for whether he
wants low priority ones.