.... Excuse the clickbait title, I couldn't help it :)
Amazing story - watch the video, I was blown away.
http://www.theguardian.com/technology/2014/aug/05/mit-crisp-packet-eavesdrop-audio-sound
That's truly amazing. This technology is going to make it into some thriller books/movies.
I read about this a while back where they were trying to do it with a glass of water. Crisps though??? I'm glad I've got nothing worth knowing!