Communication in regiment

[Duc_dAuerstaedt]

Mumble, Ventrillo and Teamspeak are all viable.

I believe Mumble uses less resources so if you were hosting a server yourself it would be a better option and is more than sufficient for small groups
Teamspeak has the most flexibility when it comes to channels, server permissions, channel permissions etc which generally makes it a better option for large groups of people.
Unless they updated it Ventrillo is the middle ground but it has been a long time since I checked in on it

Thanks for your opinion, I will try to choose the right one for us. Now I have established TeamSpeak server but I will try also Mumble and Ventrillo.

[MrTiki]

For your purposes TeamSpeak sounds like the best option, because as mentioned before, you can have a whisper list set up either with a particular channel or to individual people so that if you want to talk to just one group, you can, and if you want to talk to the other, you also can.
That being said I'm not as familiar with Vent, so it may also be possible to do similar things as this point.