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Acoustic greats - Ernst Chladni - Making Sound Visible

Ernst Florens Friedrich Chladni was born on 30th November 1756 in Wittenberg, Saxony and died 3 April 1827 in Breslau, Prussia. He was physicist and musician. According to Wikipedia, he is sometimes labelled as the “father of acoustics“. His experiments helped make sound ‘visible’. From there on, sound became known to travel in waves which, for us, is a common concept but, back then, was a novel idea. His work included research on vibrating plates and the calculation of the speed of sound for different gases.

Ernst Chladni came up with a technique to show the various modes of vibration of a rigid surface. When resonating, a plate or membrane is divided into areas that vibrate in opposite directions, bounded by lines where no vibration occurs. These are called nodal lines. Chladni was not the first to achieve this. He repeated previous experiments by Robert Hooke (FRS). In 1680, Hooke had observed the nodal patterns associated with the vibrations of glass plates. His technique involved running a violin bow along the edge of the plate covered with flour and observing the nodal patterns emerge as shown below:

Ernest Chladni

In 1787, Chladni published his findings in his book entitled: Entdeckungen über die Theorie des Klanges (“Discoveries in the Theory of Sound”). As per Hooke, his technique involved drawing a bow over a thin piece of metal whose flat surface was lightly covered with sand (not flour). The plate was bowed until it reached resonance, when the vibration causes the sand to move and concentrate along the nodal lines. The beautiful patterns formed by these lines are what we know now as Chladni figures.  Here are a few examples taken from his profile entry on Wikipedia:

Chladni plate   Chladni figure

Photos of a Chladni pattern/Author: Elmar Bergeler www.science-niblets.org

 

These are widely replicated but are still thrilling to observe!

The National Museum of America History have produced a video of the Chladni Plate Demonstration in real time which is visually fascinating to watch to understand the concept fully.  There are many other videos on the internet if you want find out more about this.

It is worth noting that variations of this technique are still used today in the design and construction of wooden musical instruments such as violins, oboes, guitars, and cellos most specifically to check the resonance conditions.

Are you interested in all things acoustics?  We have published a number of blogs in recent months that may be of further interest to you.  Please click on the following links to read our blog on anechoic chambers or on Lord Rayleigh, another great influencer in acoustics.

If you enjoyed this article, make sure you revisit our blog regularly for more information about important dates and figures from the world of sound and acoustics.

©Pulsar Instruments Published on 20th July 2015. Unauthorised use and/or duplication of the above content or picture without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Pulsar Instruments with appropriate and specific direction to the original content.

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