Sound Waves

This lesson covers sound waves — how they are produced, how they travel, their properties, and their uses including echoes and ultrasound, as required by the Edexcel GCSE Combined Science specification (1SC0).

---

How Sound Is Produced

Sound is produced when an object vibrates. The vibrations cause the particles of the surrounding medium to oscillate, creating a longitudinal wave that transfers energy from the source to the listener.

• A drum vibrates when struck → the air particles next to the drum surface vibrate → the vibration passes through the air as a longitudinal wave.
• A guitar string vibrates when plucked → sound wave is produced.
• A loudspeaker cone vibrates back and forth → sound wave is produced.

---

Sound as a Longitudinal Wave

Sound is a longitudinal wave:

• The particles oscillate parallel to the direction of energy transfer.
• The wave consists of alternating compressions (high-pressure regions) and rarefactions (low-pressure regions).

graph LR
    subgraph "Sound wave in air"
    direction LR
    A["|||| Compression (high P)"] --- B["  |  |  |  Rarefaction (low P)"]
    B --- C["|||| Compression (high P)"]
    C --- D["  |  |  |  Rarefaction (low P)"]
    end