I have found this program, there might be useful.
The program allows you too see who is talking.
Unfortunately, you can't see who is joining your channel.
Here is some screenshots: (Sorry about the bad quality)
Here is a screenshot when I'm talking:
Here is a screenshot when noone talking:
And you can choose where the Clock and Speak List shall be on the screen, and add or remove FPS Counter.
It works with SWAT 4: TSS, but I don't know with Raven Shield.
It is in BETA version and you can get it here: http://www.teamspeakoverlay.com/
22nd [SAS] Elite Virtual Regiment