If you've installed Kubuntu and find that you have no system sounds, open a terminal and type:
When you've hit the Enter key, the control panel for your sound card will appear in the terminal window.
Make sure that the Master & PCM volume levels are not set to zero by using the left/right arrow keys to select the playback type and the up/down arrow keys to set the levels.
F4 will give you access to the Capture (input) levels and F5 will display both input & output levels. Hitting the Esc key returns you to the command prompt.
Sources & References: