School of Informatics and Computing

If you are having trouble getting audio output or sound recording to work on a CS Linux machine, please follow these steps:

1. Speakers or Headphones - In order to hear audio output, you must either have headphones or external speakers as most of the Dells do not have internal speakers. If you are using a system with a Dell LCD monitor, you may have a speaker bar mounted along the bottom of the monitor. Be sure the speakers are turned on and that the volume control on the speakers themselves is turned up. If you are using headphones, be sure they are plugged into the proper headphone audio jack. If you are using a Dell Optiplex computer, you can plug your headphones into the headphone jack on the front of the system. On some Dell systems the headphone jack is located under the gray cover on the front.

   If your computer doesn't have speakers and you would like to request a set, please let us know.

2. Microphone - Most of the Dells do not have built-in microphones so you will have to have an external microphone or headset. You can plug your microphone into the microphone jack on the front of the system.

3. Audio Control with Gnome (Playback) - If you are using Gnome, you should see a little speaker icon in the panel (in the upper right hand corner of the screen by default). Right click on the speaker icon and select "Open Volume Control" from the menu. On most of the Dell computers in the department, the volume is controlled by multiple sliders, including Master, PCM, and/or PCM-2. Other sound cards and other machines may behave differently, so your best bet is to experiment. But, on the Dells you can usually control the volume with the Master or PCM slider and leave all the others at full volume. Also make sure none of the mute buttons are checked as indicated by a little red X on the speaker icon below the slider. Just click the icon to toggle the mute status.

   Also be sure you have the correct audio device set. From the volume control application, select "Change Device" from the File menu and be sure the "Alsa" device is selected and not OSS.

   Once you have these sliders positioned, exit the volume control window and again right click on the speaker icon in the panel. This time select "Preferences" from the menu. This allows you to select the audio channel you want the Gnome volume slider to control. The selection here is dependent on the hardware but on most CS Dells you will want to select either Master or PCM.

   Also note that some systems have an internal speaker that is controlled independent of the external speakers. On most systems, the internal speaker is controlled by a Master Mono or PC Speaker slider so you probably want to just mute that one to disable it.

   Once you have this all set up, you can then control the volume by just clicking the speaker icon in the Gnome panel and using the slider that should pop up.

4. Audio Control with Gnome (Capture) - Many of the same issues discussed above apply to the microphone as well. From the Volume Control window, click on the Capture tab. Make sure the Microphone and Capture sliders are up and that neither is muted. You want to be sure not to unmute both the microphone and line-in inputs and, in most cases, you don't want to unmute the line-in at all.

5. Testing Playback - While you are experimenting with various volume settings, you will need a way to generate a test sound. One easy way to do this is using the audioping command that is installed on the local CS systems. This command just pings some host and generates a sound on each packet it receives. You can envoke this by just running "audioping localhost" and you should hear a "drip" sound each second. When you want to stop this, just hit Control-C.

6. Testing Capture - While you are experimenting with microphone settings, you will need a way to capture test audio. One easy way to do this is using the arecord command line tool. To capture and playback a sample message, just run the following at the command prompt:

   arecord | aplay

   When you are done, just hit control-c to quit.

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