[libvirt] Libvirt audio xml format

Hi, excuse the possible dumb question from a new KVM/Libvirt user - I'm very impressed overall but struggling to work out how to define an audio device in the libvirt xml. I have a virtualised windows XP up & running, now want to add an audio device. I can see how to do it in kvm and I believe audio devices are now supported in libvirt, but could not find documentation on how to write the xml. System is Ubuntu 8.10 on AMD64. Thanks in anticipation.