After you has compilled and installed the kernel modules, you need to tell to the kernel and module loader utils that you have did it.
As root user, do
# depmod -a
If you see any unresolved symbols messages, try to load the ac97_codec module first with
# modprobe ac97_codec
# modprobe nvaudio
If it don't wotk, may be you kernel version and you audio module version don't be the same.
if you can provide more info (if it don't work), I can help you more
PlayStation 2 Linux Kit