The idea is to use the existing PC microphone to listen to whatever is heard in the background, be it music, your phone going off or the TV turned down. The PC then identifies it, using fingerprinting, and then shows you relevant content, whether that’s adverts or search results, or a chat room on the subject.
The process behind this is rather neat, but it’s yet another way that our privacy will be invaded. Holding all of our search terms is enough, but this is getting ridiculous. Though the article doesn’t mention which Google products this will be introduced in, you can be sure it would be Talk first up to the plate.