If there is no sound, he may have had some alsa files changed. Run "alsa-conf" as root. Sound may simply be muted.
If pulse audio is used, run padevchooser and make sure the default sink setting is correct
Play a file in mplayer and try different audio output devices.
mplayer -ao alsa song.ogg
mplayer -ao pulse song.ogg
Running "mplayer -ao help" will list the audio output devices you could try.
A program may have a lock on a device. Run "lsof | egrep '(/dev/snd/|/dev/dsp)"
Make sure the user is a member of the "audio" group.
Look at "getfacl /dev/snd/*" and "getfacl /dev/dsp". Is the regular user listed
# file: dev/snd/timer
# owner: root
# group: audio