2 different alert sounds playing at once in Ubuntu 17.10

Solution 1:

I'm not sure how reproducible this is but I was able to disable the default sound in 17.10. Here's what I did:

1. Change the sound theme to gnome using the dconf-editor (under org.gnome.desktop.sound).
2. Under Sound Effects in the Sound Settings (shown in your picture), disable alerts.

For good measure, I also logged out and logged back in between steps.

Now, I still get the alerts (at least, I do when I test it at the terminal), but I don't get two alert sounds. It is also worth noting that I upgraded from Ubuntu GNOME, so I may have different sound themes available.

If you want a different alert sound than the GNOME default, you will probably need to make a new theme. My themes were in /usr/share/sounds (each folder contains a theme). You should be able to copy a theme, change the name in the new index.theme, and then add the alert sound you like (as described in this AskUbuntu post).

Solution 2:

@desilvai's answer didn't work for me, but it helped me find a workaround. In dconf-editor, I changed org/gnome/desktop/sound/event-sounds to OFF. Now I only hear one sound. The drawback is that I can not customize which sounds it plays, but at least it is less ugly than having two sounds...