I've had this same sound issue but I found the solution (at least for me). My computer is a Dell XPS 13 9350 Ubuntu 14.04 factory preinstall.

Follow these steps to solve the no sound issue saying dummy output by running these commands:

1. Type "sudo apt-get install alsa-base alsa-utils alsa-tools libasound2 libasound2-plugins pavucontrol pulseaudio dkms" without the quotes and press .
2. Type "gksudo gedit /etc/modprobe.d/alsa-base.conf" without quotes, enter in admin's password and press , go to the very bottom and add "options snd-hda-intel model=generic", and then save and close the file.
3. Type "sudo alsa force-reload" without the quotes and press .
4. Now reboot your laptop and you should have sound and the speaker message instead of dummy output.

If your volume keybinding on the audio F-keys don't do anything prior to all of this then run these commands to fix that:

1. Type "gsettings reset org.gnome.settings-daemon.plugins.media-keys volume-up" without the quotes and press .
2. Type "gsettings reset org.gnome.settings-daemon.plugins.media-keys volume-down" without the quotes and press .
3. Type "gsettings reset org.gnome.settings-daemon.plugins.media-keys volume-mute" without the quotes and press .

You may also want to read through the link below to see if it applies to you.

http://en.community.dell.com/techcenter/os-applications/f/4613/t/19682246

I've encountered the same issue after applying the latest update ( Kernel 3.19.0-59-generic)

I have it working again and I had to execute the following steps:

1) boot , go into system settings menu (F2)

2) In System settings look for the Audio entry. In mine it said no sound card

3) Reset to factory settings. Reboot. Even I never changed anything here the reset enabled the detection of the soundcard.

4) Sound was working but high static was on the built in speakers. To fix this do the following:

sudo vi /etc/modprobe.d/alsa-base.conf

And add the following line to the bottom:

options snd-hda-intel vid=8086 pid= 8ca0 snoop=0

if you have a entry for options snd-hda-intel just comment it out.

5) Save file. reboot

After these steps my sound was back. No static and headset plugin, built in speakers all worked.

Cheers

Hi,

I'd like to have some help from you guys on this topic. I tried both the workarounds suggested at this page (this one and the one of May 24 few lines bottom) and they do not work.

In audio menu the dummy output

In the following some things I checked: 

aplay: device_list:268: no soundcards found...

cat /proc/asound/cards
--- no soundcards ---

Thank you in advance!

Hi! Thanks for the hint!

I switched off the pc (for pure chance) and everything now works. 

Just for other users, who may face the same trouble, for me the first of the two proposed methods made the trick.

Cheers, 

Luca

Awesome!!! I am glad.

I have been trying to solve this problem for sometime now too. (I have an XPS 13 9360 with Ubuntu factory installed). Along the way, I have upgraded to the latest 16.04 LTS release. Standard sound troubleshooting suggestions did not solve the problem for me. Increasingly, it seemed like the path to a solution would require the installation of a bleeding edge linux kernel with the requisite ALSA driver "built in."  Indeed, this seems to be the way to go eventually.

Someone pointed out that, with the current release, the requisite ALSA driver is considered a "3rd party" kernel module. With Dell secure boot enable, installation of the driver (at boot time) is blocked. I disabled secure boot (in the BIOS settings) and low and behold audio now works for me. Disabling secure boot has its downside. But, a worthwhile test/check before embarking on a manual kernel upgrade.

It hadn't occurred to me that secure boot might be an issue.  It does explain the symptoms many people have experienced and something to keep in mind when future issues arise.

Hi @WiseIsle I apologize for the issues you're having with the sound card.  I ran this by Jon on our tech support team and this was his recommendation:

“to try to see if this is a hardware issue you can use a Canonical live 16.04 image. If the sound issue remains, please open a ticket to have the hardware replaced.  if the issue is resolved a re-install is needed:

http://www.dell.com/support/article/bb/en/bbdhs1/how12105/how-to-perform-a-factory-reset-on-a-computer-with-the-dell-oem-ubuntu-1404-and-1604-linux-developer-edition-installed?lang=en

if that option is not there, you will need to obtain your dell image and create a usb"

HTH