Cat in the Hat Knows A Lot About That! - episode: 302
When Sally accidentally destroys Nick's model of a mountain, the Cat takes them to meet Sara of Serendip, an inventor who helps them understand that you can make new discoveries through your mistakes. Nick discovers that Sally can't hear him when he yells from his bedroom window if their bedroom windows are closed. The Cat takes them to the Soundy Sea and they learn that sound travels in waves.