cocktail party phenomenon

n. The observation that humans will notice background sounds which have importance to them while focusing on a different source of sound. Thus, a person who is carrying on a conversation with one person in a crowded cocktail party and is not attending to other people's conversation will nonetheless hear his or her own name or some other personally important thing if it comes up in one of the other conversations. This is used as evidence that we at least partially process information to which we are not attending or of which we are not conscious.