Quake 4 has commands available that allow wav files prefixed with voc_ to be played back when using global and team binds in multiplayer, this is similar to radio messages in Doom3, Quake3 CCTF and Alliance. The command set clientVoiceChat sends voice and text to everyone on the server while clientVoiceChatTeam sends voice and text messages to team members.  Example bind r clientVoiceChatTeam voc_incomingQuad

Unfortunately Quake4 does not ship with a set of voice commands, these could easily be created by the Quake4 community. For these to work the .pk4 file containing the voc_ wav files must be installed on both the server and on the client.