Better Linux Sound Managment With ALSA, Part 2

A quick and horrid way to see if sound is working is to pipe the contents of a file to dev/dsp:

$ cat  /dev/urandom > /dev/dsp

A more pleasant way is to use alsa-utils. It includes a number of useful commands for testing your setup. The speaker-test command tests your speaker channels. This example is for a simple two-speaker stereo setup:

$ speaker-test -t wav -D plug:front -c2 -l2  

speaker-test 1.0.14

Playback device is plug:front
Stream parameters are 48000Hz, S16_LE, 2 channels
WAV file(s)
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 16 to 16384
Period size range from 8 to 8192
Using max buffer size 16384
Periods = 4
was set period_size = 4096
was set buffer_size = 16384
 0 - Front Left
 1 - Front Right
Time per period = 2.731660
 0 - Front Left
 1 - Front Right
Time per period = 2.986495

You should hear a pleasant woman's voice saying "Front left, front right". -c2 means two channels, and -l2 means run the test twice.

It's common to have 5:1 surround sound even with onboard sound chips, so you can test this too:

$ speaker-test -t wav -D plug:surround51 -c6 -l2 

Note how the different channels are numbered. To test a single speaker, select it with the -s option. This example generates a sine wave tone at 45 Hz, which sounds like power hum, on the LFE channel:

$ speaker-test -t sine -f 45 -D plug:surround51 -c6 -s6 

Beware the channel-numbering gotcha- speaker-test output numbers from zero, but the -s option starts from one. Aren't computers fun!

LFE means Low Frequency Effects, which usually means your subwoofer. Of course it's more complex than that; see What is the LFE Channel? for more information.

Next: Digging Into Sound Cards »