The Fundamentals of Sound
All sound comes from vibrations. These vibrations move through the air as waves. Imagine waves in water, ripples moving through a pond. Instead of these waves moving through the water, imagine them being pushed through the air. This is how sound would appear, if we could see it.
Sound waves are longitudinal waves, with alternating levels of compression and rarefaction. We can see these in graphic forms called waveforms.
The movement of sound is called vibration. Sound is pushed and pulled (compression and rarefaction), causing it to vibrate back and forth. The sound vibrates around the place where it initially was before the sound wave arrived. This original place of origin is called the equilibrium.
Sound has the ability to move through any form; gases, liquids or solids. The object which the sound is traveling through is the medium. Sound cannot exist if it has nothing to travel through, no medium. For this reason, sound couldn't exist in outer space, as this is a vacuum, containing no gases, liquids or solids, therefore nothing to carry sound.
How do we create sound? Sounds are formed by vibrating an object. For example, when we strike a guitar string with a plectrum, it vibrates up and down. The vibration causes a sound by moving the air around it. As the string moves up, the air above it is compressed, and when the string moves down, the air moves with it and expands. The compressing and expanding of the air produces differences in air pressure. The differences in pressure in the air, moving away from the guitar string, create a wave of sound. This is how the guitar produces a sound that we can hear. The sounds we can hear vary as our ears are subject to various characteristics.
Often we are tasked with characterizing sounds. When describing sounds, we often use words like; loud, quiet, soft, harsh, high and low. We characterize sounds in terms of volume and pitch. The scientific equivalent of this is: amplitude or intensity and frequency. There are some characterizations that the human ear cannot detect. For example, the human ear is unable to detect the wavelength of a sound. Despite us not being able to hear the wavelength of a sound, we can see it when the sound is represented as a wave.
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