The baby websites and books tell me that the squirt can hear muffled noises. We recently bought a mom-car SUV so I have a pretty sweet Bose stereo system now. I mean, that thing can bass. So, I've been exposing the squirt to some nice rap music on the way to and from work. I like to turn it up so you can actually feel the bass, not just hear it. I'm going to love it when the baby comes out singing some serious beats.