In Sound, the inhabitants of Mammoth Island learn how sound energy travels in waves. While herding their mammoths toward fresh pasture through a maze of canyons, someone sneezes and the sound reverberates, startling the timid mammoths and causing them to run away! A visiting inventor explains that sounds are caused by the movement of molecules -- what scientists refer to as vibrations. Thinking about how our ears translate vibrations into sound leads a bright young Islander, Olive, to create a primitive microphone. The islanders use this device with an amplifier and loudspeaker to send out a loud trumpeting mammoth call, and the lost herd reunites and travels to greener pastures.