Sound: vibrations, pitch and loudness — Science, 11–13 years
Sound begins with vibrations and travels through matter to reach an ear or a microphone. Science, 11–13 years.
What is sound?
Sound starts when something vibrates, such as a guitar string or your vocal cords. The vibration makes nearby particles push and pull on one another, carrying a pattern through air, water or a solid. Your ear detects that pattern and your brain experiences it as sound; empty space cannot carry it.
Why study vibrations?
People needed to explain why a quiet-looking object could make a sound and why different sounds could be recognised. Measuring vibrations gave a useful answer: frequency affects pitch, while the size of the vibration affects loudness. This connects musical notes, speech and noises to something that can be observed and measured.
Comparing two notes
A tuning fork vibrates at 440 times each second, so its frequency is 440 hertz, or 440 Hz. A second fork vibrates at 220 Hz. Since 440 is twice 220, the first fork vibrates twice as often and produces the higher note. If its vibrations are also larger, it will sound louder too, but pitch and loudness are separate ideas.
Loud is not high
A common mix-up is to call a loud sound a high sound. That is reasonable because both can feel more intense when someone turns up music. But a higher pitch comes from faster vibrations, while a louder sound comes from bigger vibrations. A low drumbeat can be loud, and a high whistle can be quiet.
Sound in real life
Microphones turn vibrations in air into electrical signals, allowing phones and recordings to carry speech. Ultrasound uses very high-frequency sound to make images inside the body, while sonar uses reflected sound to find objects underwater. These devices work because vibration patterns can travel, be detected and analysed.
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