Listen up, scientists. Bill Nye is here to make some noise in the "Sound" episode. Your vocal cords do it. Speakers playing rock music do it. Even a school bell does it. They all vibrate; and that's how sound is made. Plucking a stretched rubber band makes the rubber band vibrate. Air molecules around the rubber band move, pushing other air molecules. As the rubber band continues to vibrate, it sends waves of sound through the air. It's a lot like the ripples you see when you drop a rock into a pond. You hear sound when rippling air pushes on tiny bones in your ears. Nerves in your ears send a message to your brain about the sound you're hearing. Different sounds make different patterns of waves with different distances between them. Plucking, banging, whispering, and yelling are all vibrations in air, yet they all sound very different. Sound vibrations can be thought of as waves moving through molecules. Low-pitched sounds have big gaps between waves, while high-pi