Blank noise is when people talk about things that are not important or relevant to the conversation. You know when your parents are talking to their friends and they start talking about things that you don't understand, like money or politics? That's blank noise! It's like when the radio makes an annoying sound when you can't find a station to listen to, or when someone is talking but they're not really saying anything that makes sense. It's not very helpful or interesting, so it's best to try and avoid it or change the subject to something more fun and understandable for everyone.