I have slackware 13.1 and current installed on my laptop, but from I upgrade from slackware 12.2 and 13.0, I meet no voice issue. I have tried to add my user to audio group, then alsaconf, alsamixer, but not work.
Today I need a free call to USA on my computer, I have to fix the problem. It’s not hard, just look at the following code if you are using Thinkpad
bash-4.1$ cat /etc/modprobe.d/sound.conf
alias snd-card-0 snd-hda-intel
alias sound-slot-0 snd-hda-intel
options snd-hda-intel model=thinkpad