Sound energy

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Content – Forms of energy


Sound is produced when a force causes an object or substance to vibrate.

Sound energy is transferred through the environment (matter) by wave motion caused by the vibrating object.

Sound energy is often measured by its pressure and intensity, in units called decibels.


A vibrating object that is connected to its environment (matter) will transfer energy to its environment. The vibrations and the resulting energy is transferred though the environment from “neighbour to neighbour” i.e the wave motion. Waves transfer energy through a matter without changing the physical location of the matter.

Longitudinal waves

When waves transfer energy by pushing neighbours in the same direction that the energy moves, the waves are called longitudinal waves.

Sound waves are examples of longitudinal waves

Waves are called pressure waves when the particles cluster together in volumes of “high pressure”. Sound waves are an example of pressure waves that move through matters such as gases, liquids and solids.

The speed of the sound waves increases by the density of the matter they travel through.

Speed of sound through iron = 5130 m/s
Speed of sound through water (seawater) = 1531 m/s
Speed of sound through air =344 m/

Formula – Sound energy

The total sound energy will equal the maximum kinetic energy:
E= \dfrac{1}{2}mv^2 = \dfrac{1}{2}m(A\omega)^2
m = density of the medium the sound waves travel through
Aω = the maximum transverse speed of particles
A = \dfrac{\nu}{2\pi}
A = amplitude