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Waves

What is a Sound Wave?

Sound is a longitudinal wave that can travel through
gases (air), liquids (under water) or solids (the Earth).
Sound cannot travel through a vacuum.


What is the Speed of a Sound Wave?

The speed of a sound wave depends on the
density of the medium (substance) through which it is travelling.
The more dense the medium, the faster the sound wave will travel.
Sound waves travel faster through the Earth than under water,
and sound waves travel faster under water than in air.
The speed of sound in air is approximately 330 m/s (see calculations).
Sound waves travel much more slowly than light waves.


How are Sound Waves made?

When an object vibrates (moves backwards and forwards) in air
it produces sound waves.
The sound waves carry energy which can move other objects,
such as the ear drum or a microphone diaphragm.
The sound wave will have the same frequency
as the frequency of the vibrating object that made it.
The object may be a column of air (a flute, clarinet or a whistle)
or a string (a guitar, violin, double bass or a piano)
or a paper cone (loudspeaker) or a firework.

Sound waves can be reflected, refracted or diffracted.

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