Say these commands into the headset during gameplay to trigger the corresponding team actions:

"Bravo defuse bomb": Put your crosshairs on the bomb and say this to... you guessed it... defuse the bomb.
"Bravo open door": Same idea. Point crosshairs at door and speak.
"Breech, bang, clear": Point your crosshairs into an open room and your team will throw grenades inside.
"Hands up, get down": Sneak up behind an enemy and yell this, and guess what?
"Team low profile": Your crew will go into stealth mode.
''Hands up, get down:'' Say this to guards to get them to do it.
''Don't ask, don't tell:'' Your teammates will not help you very much.
''Bravo snipe:'' Your teammate will use their sniper rifle.
''Bravo kill me:'' Your team will kill you.
''Bravo report status:'' Your team will tell you their details.
''I got a gun; what do you got?:'' Find out what weapons they have.