This episode is an ear-tickler! Guess your way through eleven mystery sounds — one from a scientist, and ten from listeners like you! Plus, another mystery: what’s making Marc and Sanden dance to the sounds of a door jamb and a printer? Stick around for all these reveals, and the answer to a new Moment of Um: Why is air invisible?

This episode of Brains On is sponsored by the Kevin Henkes book, "Sweeping up the Heart,” Panama City Beach (visitpanamacitybeach.com), and Philo (philo.tv/brains). You can support the show at brainson.org/donate