It still amazes me that soooo long after the game has come out people still dont know how to mute on their own, so this is my contribution to the community.

When you're in-game and someone is destroying your eardrums. Press [Esc] to get to the main CS menu. Look for a button that says "Player List" Click on it, find the person's name, and click "Mute In-Game Voice". Abracadabra, no more mic spam. Feel free to close this now since it doesnt need responding to