Multiple Sound Cards
Can't hear sound? Is the sound icon missing in the bottom panel? You likely have more than one sound card and ALSA chose the wrong one at boot. To correct this, you could create a .asoundrc file in your home directory specifying the default card. Unfortunately, Firefox does not read this file so you would continue to have no sound in Firefox. To remedy this, you will need to specify via modprobe in which order to load sound drivers so that your prefered card is selected first by ALSA.
First, run the following command to see which order ALSA assigned your cards:
cat /proc/asound/cards
In my case I got:
0 [HDMI ]: HDA-Intel - HDA Intel HDMI
HDA Intel HDMI at 0xe0510000 irq 61
1 [PCH ]: HDA-Intel - HDA Intel PCH
HDA Intel PCH at 0xe0514000 irq 59
Now, tell the kernel to load the intel driver with 1 as the default:
sudo bash -c 'echo "options snd_hda_intel index=1,0" > /etc/modprobe.d/alsa.conf'
You can verify the driver name to use above by running
lsmod | grep snd
Reboot the computer and you should have sound!