Just like: I have a stereo system, and I want to test it, but I don't have any music :/ or I got a car but I don't have gas to get it for a drive.
Put a MIC in it and see if it works...
cat /dev/random /dev/audio
cat /dev/random > /dev/audio
cat /dev/gpmdata > /dev/audio
If you have internet connection, visit www.rollingstone.com and C-Net for free live music and check your SB to see if you get any sound out of it..
Or if you have a CD-ROM, play a CD-audio on it.