Download sound from google translation

Hello. I'm trying to save the sound of google translate on my computer without recording it. I found a video that say you can find the mp3 files of the text to speech in the temporary internet files http://www.screenr.com/zjo8 But as on firefox we can't access the temporary internet files (at least not in a easy way) the trick doesn't work!! I've tried the cache viewer add-on but it's not working yet I think. Thanks to all Best regards.