The "script" you are talking about, is the "say" command, like DBR_ONIX said. There are three different 'sound' commands in OFP:
object say "soundname" -> makes the sound come from the object; stereo effect is heard
playsound "soundname" -> plays the sound at a fixed volume, no stereo effects
playmusic "musicname" -> same as playsound, only the music is defined differently in your description.ext, and can be better quality/stereo
You should grab bloodmixers sound tutorial from the ed depot. That will show you everything you want to know about sounds, and explain everything you don't understand about what I just said.