Sound

Science

Definition

Sound is a mechanical wave that travels through matter (solids, liquids, and gases) as vibrations of particles. It cannot travel through a vacuum because it requires a medium. Sound waves are longitudinal, meaning particles vibrate parallel to the direction of wave travel.

Examples

  • A guitar string vibrating and pushing air molecules to create sound
  • Thunder heard after lightning because sound travels slower than light
  • Sonar using sound waves underwater to map the ocean floor
Key Fact

Speed of sound in air ≈ 343 m/s at 20°C; faster in solids and liquids

Related Terms

Sound waves Wave properties Doppler effect Interference

Study This Concept

Practice sound with free review games in these units:

AP Physics 1 Unit 7: Waves and Sound