Last week I lost sound after upgrading from f22 to f23. I'm not sure if it could be
the same problem. In my case, I don't know exactly what happened, but after upgrading,
the system couldn't find the corresponding version of kmod-nvidia and it seems that
fedora automatically got a previous kernel version with an existing kmod-nvidia to be able
to boot, but the sound died :(
Once I realized that the system couldn't find the sound card, I checked my kernel
version ( uname -a ) and I found that it wasn't the latest one. In my boot folder I
found a newest kernel but grub wasn't using it. So after expending an hour checking
what was happening, I changed kmod-nvidia with akmod in order to boot fedora with the
latest kernel available and boila, sound came back.