Install sound-theme-freedesktop by entering the following commands in the terminal:
sudo apt update sudo apt install sound-theme-freedesktop
Description:
freedesktop.org sound theme
The default freedesktop.org sound theme following the XDG theming specification. It contains a full set of sounds for different desktop events. . These sounds come from various sources: KDE, Ekiga, Pidgin/Purple, ALSA.
Homepage: https://www.freedesktop.org/wiki/Specifications/sound-theme-spec/
Version: 0.8-2ubuntu1
Section: sound