The military has radio communications mastered. Lives depend on how well they communicate, so everyone has to communicate in the same manner. Rule #1 of military communications, NEVER say the word repeat. Repeat is the signal for artillery to repeat their last barrage, on the same spot. If everyone is on the same page for voice comms, then they work great.
"Any station net, any station net, this is USS Nimitz, USS Nimitz, radio check, over." Notice the pattern, the first name is the unit being called, then the calling unit, followed by the message. In a game this would take too long, so it needs to be shortened. The worst thing to say in a FPS voice communication is, "Behind you". Of 8 people on the channel, 7 will think that someone is behind them, and turn to look. "GI, behind you", is a better way to convey the message.
Game communications should be standardized for everyone on the team. Person being called, followed by a short message, and then, if needed, the person calling. This format works quickly, and will aid in making the voice communication relevant. If you can use a short typed message, that will usually work quicker with less distraction.