I have been using Ubuntu for some years now and have had very little trouble. Yesterday I upgraded to 12.04 without any problems.

Now the sound output is poor - the volume seems to be louder than before but the quality is poor. Music sounds distorted and scratchy. This happens with VLC, Gnome Media Player and with streamed music through Firefox.I get the same problem when using both the speakers and headphone outputs.

This also happens another computer - also upgraded yesterday. It also happens with both Xubuntu and Ubuntu.

Before upgrading I was getting very good quality music.

Any suggestions??