Just a quickie...
If you DO hear foot steps, and you ask someone if it's them, it might be a better option to quickly check your map to see if there's an arrow near you showing your team mate. This will probably be quicker than waiting for a response from your teammate to tell you whether or not it's them. I know I used it lots today for that purpose, and more than usual it was NOT a teammate and was able to take the guy out before he got near me.