How to make peoples mouth move when using voip

Does anyone have any idea what the command or addon that you need to activate this is? A server owner has employed my help but all i could find was https://wiki.facepunch.com/gmod/GM:MouthMoveAnimation which dosnt explain a whole lot

What gamemode are you trying to do this in. I believe darkrp already does this automatically, but if you are in something else like sandbox you should look into a way to monitor the incoming voice data, and get peaks of the audio and use the move mouth function to make the mouth move