Harmony in motion

Sound, as you probably know, is the result of pressure waves travelling through the air. As the pressure wave enters your ear, it causes the tympanic membrane to vibrate. This, simultaneously, causes your inner ear bones to dance around like a teenager at a rock concert. In turn, this moshing vibrates tiny hairs in your cochlea, creating electrical signals which pass to the brain. This convoluted, dancing procession of movement allows you to hear.

The sounds that cause this complicated conga line are, unfortunately, invisible. The beautiful sequence of high and low pressure movements of air molecules that emanates from your favourite singer’s vocal chords will only ever be appreciated by one pair of sense organs. However, as the below video shows, we can make the audible visible with nothing more than a handful of salt.

The series of salty artworks form due to a physical property of materials known as fundamental frequencies. When the sound wave from the speaker corresponds to a particular resonant frequency of the metal certain areas begin to vibrate. The salt sprinkled on top quickly shuffle off to those areas not in motion. As the frequency from the speaker increases, different patterns begin to emerge, which you can see in the video.

Posted on August 17th 2011 in Blog with 1 comment | Tags: ,


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  1. […] This is a lovely short article by Charles Harvey about the transmission of pressure waves created by sound. It’s nicely illustrated with a film, where the patterns of these pressure waves are visualised with dancing grains of salt. The beautiful sequence of high and low pressure movements of air molecules that emanates from your favourite singer’s vocal chords will only ever be appreciated by one pair of sense organs. However, as the below video shows, we can make the audible visible with nothing more than a handful of salt. […]