Fixed Missing Soundcard

https://help.ubuntu.com/community/SoundTroubleshootingProcedure

If you are using Ubuntu 12.04 LTS, Ubuntu 14.04 LTS, Ubuntu 15.10, or Ubuntu 16.04 LTS, then please execute this command and reboot:

sudo apt-get update;sudo apt-get dist-upgrade; sudo apt-get install pavucontrol linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; sudo apt-get -y --reinstall install linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; killall pulseaudio; rm -r ~/.pulse*; ubuntu-support-status; sudo usermod -aG `cat /etc/group | grep -e '^pulse:' -e '^audio:' -e '^pulse-access:' -e '^pulse-rt:' -e '^video:' | awk -F: '{print $1}' | tr '\n' ',' | sed 's:,$::g'` `whoami`

The same thing happened again... But only this cannot fix the whole thing.

I run the following commands in sequences and rebooted in between and solved the problem. I don't really know which is necessary and which don't...

killall pulseaudio; rm -r ~/.config/pulse/* ; rm -r ~/.pulse*

the reinstall alsa

sudo apt-get remove --purge alsa-base

sudo apt-get remove --purge pulseaudio

sudo apt-get install alsa-base

sudo apt-get install pulseaudio

sudo alsa force-reload

then download kernel from http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.8/ and 

sudo dpkg  -i linux-headers-4.8.0-040800_4.8.0-040800.201610022031_all.deb

then reinstall by aptitude

sudo aptitude --purge reinstall linux-sound-base alsa-base alsa-utils linux-image-$(uname -r) linux-image-extra-$(uname -r) libasound2

then follow the troubleshooting procedure

sudo apt-get update;sudo apt-get dist-upgrade; sudo apt-get install pavucontrol linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; sudo apt-get -y --reinstall install linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; killall pulseaudio; rm -r ~/.pulse*; ubuntu-support-status; sudo usermod -aG `cat /etc/group | grep -e '^pulse:' -e '^audio:' -e '^pulse-access:' -e '^pulse-rt:' -e '^video:' | awk -F: '{print $1}' | tr '\n' ',' | sed 's:,$::g'` `whoami`

and 

sudo reboot

After the first time, follow the procedure again

sudo apt-get update;sudo apt-get dist-upgrade; sudo apt-get install pavucontrol linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; sudo apt-get -y --reinstall install linux-sound-base alsa-base alsa-utils lightdm ubuntu-desktop  linux-image-`uname -r` libasound2; killall pulseaudio; rm -r ~/.pulse*; ubuntu-support-status; sudo usermod -aG `cat /etc/group | grep -e '^pulse:' -e '^audio:' -e '^pulse-access:' -e '^pulse-rt:' -e '^video:' | awk -F: '{print $1}' | tr '\n' ',' | sed 's:,$::g'` `whoami`

and shut down the computer then turn it back on. Do not reboot it, this is important and I don't know why.

Then the sound card is back.