I forget the exact process but you can calibrate in windows.
For a while my squaddies told me i sounded like i was gargling on razorblades everytime i would say something so i fixed it.
In windows, i forget where, there is an option to calibrate the microphone, where you're supposed to read a paragraph, and you have level bars indicating the volume.
What i did was read the paragraph louder than i normally speak in the game so the volume lights would be near maxed out in red with the microphone volume on the "volume control" maxed out.
Now i set the mic slider on the volume control between the 1st and 2nd line without boost, so when i speak, i don't hear myself in the headphones, but when i do the sound recorder test, and tune to myself in game, i'm 5x5.
You might have to do it a couple of times to get it right.
Edit----The sound recorder test is a good indicator of weather or not your too loud, or too low.
Just curious, do people normally hear themselves through there headphones or speakers when they talk into the mic?