Sorry, but this is pointless. You are not giving us any info about your system, your footage, comp settings, render settings and so on. Nobody can help you based on a "this doesn't work" post.
Make sure that the speaker icon in the Playback Controls Panel is turned on. Preview is NOT started with the space bar. You use the playback controls panel or press the . key on the numeric keypad. If you've done all this and you still have no audio then you need to tell us about your system and the files you're trying to use.