Multiplayer Mic Problems

For some reason I have been experiencing a problem in multiplayer where apperantly I cause an Echo to other players.

This would make sense, if I had a mic plugged in at all....... I am playing on a desktop with no mic. I even tried turning off my sound so like none of the sound from players would echo back, but it still echos. 

I feel like my mic is simply taking what players say and sending it right back to them, as if my output sound is also being turned into my input sound.

Any fixes?

Thanks