Another thing i would do is run the DxDiag test.
Go to Windows start menu, bring up the command line with "Run". Type DxDiag.
Now in DxDiag, go to "network" and click on 'Direct Play Voice Otions'. This takes you through testing your mic in windows. If it works there, youre good to go ingame and adjust the otions there.
To test the mic ingame, open radio and type your name in the last pulldown box (Voice channel). Now hit enter. If you press 'T' while talking, you should hear your own voice now.
Or up on a field where theres friendlies around and ask for a 'radiocheck' over range (hold F12 while talking). If you get a 5 by 5 back, it means youre transmitting loud and clear.