What is sound? How is sound propagated?

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Sound is a mechanical, longitudinal wave that is caused by the vibration of molecules. In order to fully understand this definition, the meaning of “mechanical wave” and “longitudinal wave” need to be understood. Each term is defined below:

Mechanical wave- A mechanical wave is a wave that requires a medium through which to travel, as opposed to electromagnetic waves which do not require mediums. Therefore, mechanical are not able to travel through vacuums.

Longitudinal wave- A longitudinal wave moves in the same direction as the displacement of the medium through which the wave travels. Thus, a longitudinal wave appears to move in a “back and forth” motion, which cases compressions and rarefactions.

Sound propagates through compressible medium through which it travels. As sound propagates, it can be reflected, refracted, or diffracted.

Additionally, the speed of a sound wave is affected by the type of medium through which it travels. Recall that sound waves result from the vibrations of particles. Thus, due to the proximity of the particles, sound waves usually travel the fastest in solids. Likewise, sound travels the slowest through gases because gas particles are spread so far apart from one another. The state of the medium through which a sound travels is not the only factor that affects a sound’s speed. Speed of a sound wave can also be affected by the density, temperature, and elasticity of the medium through which the sound waves travels.

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