Sound Waves and Hearing

This lesson covers sound waves — their nature, properties, and how humans hear them — as required by AQA GCSE Combined Science Trilogy (8464), Physics Paper 2, section 6.1. You need to know that sound is a longitudinal wave, understand the range of human hearing, and be able to describe echoes and ultrasound.

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Sound as a Longitudinal Wave

Sound is a longitudinal wave. When an object vibrates (e.g. a loudspeaker cone or a guitar string), it pushes and pulls on the surrounding air particles, creating alternating compressions (high-pressure regions) and rarefactions (low-pressure regions) that travel outward from the source.

graph LR
    subgraph "Sound Wave Propagation"
    direction LR
    S["Vibrating source"] --> C1["|||| Compression"]
    C1 --> R1["  |  |  |  Rarefaction"]
    R1 --> C2["|||| Compression"]
    C2 --> R2["  |  |  |  Rarefaction"]
    end

Key Facts About Sound