You can test your mic one of few ways. Make sure your mic is plugged in
1) (Assuming you have Vista or win7) Richt click on your volume control on your system tray (bottom right of your desktop) >> Recording devices >> and talk, you should see the bar go up and down according to your face
2) Open up DoD >> Audio >> Test your mic
3) press console >> type voice_loopback 1 >> and press f (default key for recording in valve games) and you should hear your own voice.
Let us know of any complications.