If you are one of the early users who have already upgraded to Ubuntu 11.10 Oneiric, you will discover that the startup login sound is activated by default. Worst still, there is no way that you can turn it off.
The reason for this is because the login sound entry (in the Startup Applications) is hidden by default. Why is it hidden is unknown, but here’s how you can unhide (and disable) it.
Note: This is an annoyance found in Ubuntu Oneiric beta. It might (or might not) be fixed in the final release.
1. Open a terminal and type in the command:
gksudo gedit /usr/share/gnome/autostart/libcanberra-login-sound.desktop
2. At the end of the file, change the “NoDisplay” from “true” to “false” (without the quote). Save and close the file.

3. Now, go to the Startup Application (from the power icon at the top right corner) and you should see the Gnome Login Sound entry. Uncheck it.

That’s it.
via Ubuntu Forums
Would be easier to just execute the following command from a terminal:
gsettings set org.gnome.desktop.sound event-sounds false
Thanks. It would be better to have the GUI so you can turn on/off easily.
Thanks for the tip. For some reason this has not been fixed in the final release.
THANK YOU!!!!!!!!111one!11!
You saved my ears!!!
Thanks! Agree this should have been in the final release.
thanks !
thanks
Awesome, thank you! That was really easy.
How awful! That’s no Linux for Human Beings at all! >:|
Thanks so much, that’s been annoying the hell out of me since I upgraded!
Seems to be corrected in proposed.
I use the final release of Oneiric. When I open that document, there is no line with NoDisplay. So I just had to insert it at the end of the document: “NoDisplay=false” (without the quote), and then only I found it in startup applications and disabled it. Thank you for the idea.
Great tip! Thank you very much!
I just don’t get it. How can free software developers make all these bad decisions. It should really be more easy to turn off this annoying startup sound.
Reminds me of the other bad decision gnome made recently: changing the shutdown option to hibernate.
But on the other hand I have to admit that I really like the rest of the direction gnome is heading with gnome shell.
loads of thanks.
Linux user since many years, and I guess I fall into the “power user” category by other people’s norms. I cannot understand what went through these developers’ minds when they created this whole new “paradigm” that “users will soon embrace”.
Think how many hours have gone into all this. Think of how they could have been better spent, not least in the name of free software.
Many years of telling people that Linux is not especially difficult to learn. Ubuntu is trying hard to flush that down the drain. F****** “gsettings set org.gnome.desktop.sound event-sounds false”, this is just a joke, coming from me who usually lives exclusively in the terminal.
Thank you for this page. It is insane that such a guide is needed.