I used the default alert sound in Ubuntu 17.04. When I upgraded to 17.10, the same sound played. When trying different sound settings, I clicked on a sound and now I hear that sound + the old one. If I set "Alarm volume" to OFF, there's obviously no sound. If I set it to ON, I hear 2 sounds.
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:
- Change the sound theme to
gnomeusing the dconf-editor (under
- 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).