Has anyone recorded audio from a microphone using Linux? If so, how?

I just want to record my voice saying hello world and save it as an .wav or .mp3 file. I've tried using Knoppix 4.0.2 by starting Audacity (K > Multimedia > Audacity ) and then clicking on the red Record button, but all I get is a loud hum. Do I need to configure something else first, e.g. load a module, configure a device, something?

The machine is an eMachines T23341. lspci lists the sound card as "multimedia audio controller: VIA Technologies, In.c VT8233/A/8235/8237 AC97 Audio Controller (rev 50)." Been googling but haven't found anything helpful, yet. I've also been reading the Audacity tutorials.

BTW, if I boot the same machine with Windows XP, everything works just fine using Sound Recorder, but I can only record 75 seconds.

Regards,
- Robert
http://www.cwelug.org