I managed to get the sound working by following instruction for MBP5,5/Lucid here https://help.ubuntu.com/community/MacBookPro5-5/Lucid#Sound
Basically I added the following to /etc/modprobe.d/alsa-base.conf and restart
options snd-hda-intel model=mbp55
also make sure the front speaker is not muted
I managed to get the sound working by following instruction for MBP5,5/Lucid here https:/ /help.ubuntu. com/community/ MacBookPro5- 5/Lucid# Sound
Basically I added the following to /etc/modprobe. d/alsa- base.conf and restart
options snd-hda-intel model=mbp55
also make sure the front speaker is not muted