listen sound with user permission

environment:
 - debian 4.0

problem:
I have a problem about sound.
I can listen sounds with Super user account. (root)
but, I can't listen sounds with (normal)user account.

solved:
 - $sudo adduser useraccount audio
 - reboot

or

 - open /etc/group
 - add useraccount to audio group.
  - ex> audio:x:29:seungrye