I do a lot of work with MythTV and find it invaluable to run changes and latest builds inside a virtualization platform like VMWare or KVM. When using KVM through virt-manager in Ubuntu Hardy Heron, you don’t have an option to add a soundcard to a virtual machine. To get sound to work though, all you need to do is start the virtual machine from the command line and provide the -soundhw option like so.
kvm -m 1024 -soundhw all /home/jason/MythBuntu-1.img
Where -m is the amount of memory allocated to this vm.