How do I disable the drum beat sound on the login screen?

For Ubuntu 12.04+

LightDM Way

Also known as the FluteFlute Slap, the LightDM Way involves having to logout and on the LightDM Login Screen you can change the volume or even mute the sound.

In the Login Greeter you can see the Volume on the top right. Adjusting the volume there does not affect the volume when the session starts, so you can MUTE the sound in the Greeter without muting the sound when your session starts:

Ubuntu Tweak Way

The Ubuntu Tweak way involves having to download the Ubuntu Tweak app and then disabling the sound from there. Do the following steps and you can do it this way:

sudo add-apt-repository ppa:tualatrix/ppa
sudo apt-get update
sudo apt-get install ubuntu-tweak

Open Ubuntu Tweak and on the Tweak Tab select "Login Settings" option, you should see the Play Login Sound option. Yo need to click on the Lock button above to be able to change this.

For Ubuntu 11.10 and Below

Go to System -> Preferences -> Startup Applications

Disable the one called GNOME Login Sound

(uncheck the box and click close)

you can also go to System -> Preferences -> Sound and disable the whole sound system (Like windows sounds, alerts, etc..)

In older version you could go to the Sound Preference part and select each sound and what you wanted to do. It was removed around 9.04 or 9.10. It would be good if it came back.

The start-up sound can be disabled editing the Unity Greeter configuration. Running the following from a terminal will do this:

echo -e '[com.canonical.unity-greeter]\nplay-ready-sound = false' \
    | sudo tee -a /usr/share/glib-2.0/schemas/50_unity-greeter.gschema.override
sudo glib-compile-schemas /usr/share/glib-2.0/schemas/

If you are running Ubuntu 12.04 LTS make sure you have updates installed as this feature was added in an update.

12.04 - 16.10 (LightDM)

Here is what worked for me after I installed 12.04 last week.

The steps are these, adapted from http://www.liberiangeek.net/2012/05/disable-the-ready-drum-sound-in-ubuntu-12-04-precise-pangolin/:

gksudo gedit /usr/share/glib-2.0/schemas/50_unity-greeter.gschema.override

Add these lines:

[com.canonical.unity-greeter]
play-ready-sound = false

Save, then run:

sudo glib-compile-schemas /usr/share/glib-2.0/schemas/

Reboot and enjoy.