Comment 62 for bug 204536

I have this problem too. I am not sure if it is caused by setting the /tmp/ and the /var/log to ramdisk. (I am using SSD drive)

fixes I tried:
1. Adding amixer -q set Master some_number% unmute to /etc/rc.local didn't help.

2. Entering the same command manually after Ubuntu starts:
It only works if the % number is different than the previous one. For example the volume suppose to be at 30% and it shows correctly in gnome volume control. However when I play something, the volume is actually at max. Entering amixer -q set Master 30% unmute does not help but a different number do set the volume correctly. The problem is, I am too lazy to type the command every time. It is much faster to press the volume button from my keyboard.

3. Finally I use similar methods raevol suggested. I change the script to

amixer -q set Master 20% unmute
amixer -q set Master 30% unmute

and it works.
Hope Ubuntu got this problem fixed soon, and thanks for all the information all people provided :D