Audio is working, but the speaker test doesn't work

I've installed Ubuntu 12.04 LTS from a minimal cd on a netbook (Asus 1001 PXD). I've installed the ubuntu-desktop package using the --no-install-recommends option.

Everything works fine, except the "sound test" for headphones or analog speakers.

Clicking on the "test" buttons (front left and front right) I don't hear any sound. Despite this, the audio is working properly.

I've checked the audio levels with alsamixer; I have also checked that the test sounds actually exist in /usr/share/sounds/alsa.

I tried an installation of Ubuntu 12.04 LTS made with the desktop-cd, and in this case the speaker test works properly.

I suppose, therefore, that the problem could depend on the lack of a package, but I have not identified which one.

I've found the solution:

it is needed to install the libcanberra-pulse package, that is recommended for the gnome-session-canberra package, which is one of the packages on which depends ubuntu-desktop.

I had the same problem after updating to Ubuntu 20.04. and rebooted.

I solved using:

sudo apt-get install -y libcanberra-pulse