When i make an ambient_generic and browse the announcers voices i cannot hear them. I have found out where in my steam folder they are and extracted them to my desktop using gcfscape, but what do i do now to get them to work.

You can find out which sound files you want here: http://theportalwiki.com/wiki/Announcer_voice_lines

They will play in game.

Thanks, i have the voices working now.