Sound

Sound is a concept that many people on the planet have "heard" of (pun intended) but in physics, sound, while being the same concept we hear in our everyday lives, is slightly more than just something you hear.

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A more hardcore definition of sound is that it's a vibration that propagates as a wave. Vibrations are just mechanical oscillations, like the ones discussed in the waves section. Sound is a longitudinal wave but in many diagrams, it is represented as a transverse wave for simplification purposes. If we go down to the individual atoms that make sound, the disturbance of those atoms caused by vibrations is what makes sound waves. These atoms compose air molecules, which serve as the medium of propagation for the sound itself.

The vibrations create variances in pressure known as compressions and rarefactions. Compressions are areas of low pressure and rarefactions are areas of high-pressure regions. These pressure disturbances generate sound as they push particles in and out to create constant waveforms.

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The human sense of hearing is just our perceptions of sound waves coming into our ears.

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The amplitude of a sound wave is its loudness or volume. This makes sense with the implications of a wave's amplitude, as a wave's amplitude correlates with the wave's intensity. This means that by nature, loudness is the intensity of a sound wave. The frequency of sound is more commonly known as its pitch. Higher frequency sounds produce more pitched up, potentially "squeaky" noises, whereas lower frequency sounds produce more pitched down noises.

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The speed of sound is of great interest because of just how much it changes in different mediums. Below is a table for the speed of the sound in different materials.