You can’t hear sounds without air
　 　
There are so many sounds all around us. The sounds of cars, footsteps, bouncing balls, and so on. We hear sounds with our ears. But the air is what actually carries sounds to our ears so we can hear them. Deep in the ear is the eardrum. The eardrum is necessary to hear sounds. Sounds make the air vibrate like waves on an ocean. The air vibrations in turn vibrate the eardrum, which we sense as sound. We hear all kinds of different sounds — high-pitched sounds, low-pitched sounds, noisy sounds, quiet sounds — because each sound creates air vibrations of different sizes and intensities.