Preliminary audio device checks

Is your sound system plugged in and switched on. I spent an hour trying to diagnose a sound issue when the problem was that I had switched off the speakers to answer a phone call and forgot that I had done so. :-(

Checking volume levels

Before messing around with uninstalling and installing various sound programs to fix a problem, check your volume levels. It is often the case that a muted channel is the problem, even though the description may not sound immediately relevant. In this regard, muted Surround or Center channels are common culprits. So unmute and raise the volume of one channel at a time and check whether sound is then produced by a running sound application e.g. Rhythmbox.

You can access the volume levels for the various channels from the command line or the GUI.

  1. From command line: Open a terminal window and launch alsamixer. Then unmute as described above.
    • Note: Often you need to specify the card you want to control, do that by launching alsamixer -c0 or alsamixer -c1 etc, where the number after -c corresponds to your soundcard’s index. To know what indexes your soundcards have, see below (under “Checking sound device assignment”).
  2. From GUI: This can be done by running something like gnome-alsamixer from a terminal window or navigating to your your Volume Control. Then unmute as described above. Also check that your switches are set correctly – for instance that if you use the analog output the analog switch is set ON or that the digital or S/PDIF switch is set OFF. You can select which tracks/switches are visible in Volume Control (see above) under Edit->Preferences.
    • Note: These controls have equivalent functionality to alsamixer but with a graphical interface. Checking or unchecking devices in the these accomplishes the exact same thing as unmuting or muting devices, respectively, in alsamixer.
    • Starting with Ubuntu 7.04, the sound volume control is also accessible from Menu->Sound&Video->Volume Control. It may be hidden in your menus but can be shown by going to System > Preferences > Main Menu and under Applications > Sound&Video ticking Volume Control.

Checking sound device assignment

  1. Most sound applications output to card0 by default. In some cases, other audio devices (like a USB MIDI Keyboard) might be recognized as a soundcard and take card0, bumping your real soundcard to card1. To see which devices are connected to which cards, do the following:
    •  cat /proc/asound/cards
  2. You can manipulate the device number assignment by adding modifying /etc/modprobe.d/sound.conf (create it if necessary). Next boot, the snd-usb-audio device will get index 1 (by default it will be 2).
    •  options snd slots=,snd-usb-audio

The index numbers (0, 1, … 7) signify the priority of the device, with the highest priority device being 0, then 1, and so forth. In theory, applications should first attempt to use the highest priority device first, but if for some reason the application is unable to use the device, it will use the next highest priority device. For example, if you have a USB sound card that can get picked up with OSS, which browsers, flash, and skype may not output, if you set your USB card at first priority, it will play when using, say, Rhythmbox, but your other applications will play through your other soundcard. FIXME PLEASE: for more information go to the ALSA-Configuration kernel document.

Checking permissions and resources

  1. Make sure that all users needing access to the Sound Device can “Use audio devices” in the “User Privileges” tab of users-admin (System->Administration->Users and Groups).
  2. Test different “Sound Servers”: Go to System > Preferences > Sound (“Multimedia Systems Selector” in earlier editions of Ubuntu). From there, you can test the different options. In some scenarios several different sound servers may be installed, and only one may work. This is probably the origin of the problem if you cannot play audio with xine or rhythmbox, but you can with xmms or helix/realplayer.
  3. If you application sounds works, but your system sounds does not (login, logout, error sounds…) try removing the .asoundrc* files from your own directory (e.g. with ‘rm .asoundrc*’). It should make the system sounds work without a reboot.
  4. If you can get absolutely no sound and you have an onboard sound chip you can try to disable it in the BIOS. This solves the problem is some cases.
  5. If you have no sound and you have a regular sound card type “lsmod | grep snd” in the terminal and see if there is more than one card listed. It’s possible that you have a motherboard sound chip that is interfering. Add it to the bottom of the blacklist file. For example, sudo nano /etc/modprobe.d/blacklist then add “blacklist snd_via82xx” to the bottom.

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