The tilde~ key opens a chat line, and when followed by one of the F1 through F12 keys will send a preset .wav sound and chat line to other players. The 12 sounds that are preset are editable in the chat.txt file located in the FA folder. The source of these .wav files is the FA program, so players can only hear sounds that are common to all players FA folder.
There are many other sounds to choose from -- The .wav file can be changed, as well directing it to only a target, only your team mates, or to all players. Look on some of the fan sites for a text file which lists the filenames of FA sounds, or make friends with people online, then ask for a copy.
