Sound

waves · physics · hearing · vibrations

How we hear. Sound travels as invisible waves of pressure that move through air, water, and other materials. When these waves reach your ear, they make your eardrum vibrate, and your brain turns those vibrations into the sounds you recognize.

Human hearing range. Your ears can pick up sounds between 20 Hz and 20,000 Hz (called kilohertz). Very low sounds like a rumbling truck are around 20 Hz, while a squeaky whistle might be 10,000 Hz or higher.

Sound needs a material. Sound can't travel through empty space like light can, because it needs something to push against. It travels through air, water, solid objects, and other materials that can be squished and stretched.

Medical superpower. Doctors use sound waves in special imaging machines called ultrasounds to peek inside your body without any cuts. These waves bounce off your organs and create pictures that help doctors understand what's happening inside.

Communication and music. Sound is how we speak, sing, and share our thoughts and feelings with other people. Music, talking, and laughter are all ways we use sound to connect with others.