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October 9, 2012 at 3:53 PMComments: 2 Faves: 0

Droppin' Chladni Plates

By E.M. Wollof from SLN More Blogs by This Author

"One must be sane to think clearly, but one can think deeply and be quite insane." - Nikola Tesla

In my first entry into the Resonate series, I included a video of a plate with sand on it. In this video the sand was being manipulated into intricate shapes by tones that caused the plate to vibrate at equivalent frequencies, or to resonate at said frequencies. These demonstrations of resonate frequencies are actually based on the invention of one man, Ernst Chladni.

The Early Years

Chladni was a child of 18th century Germany. I will spare you the wiki-tails of his younger years as they are rather common for the time. His father was a lawyer and a man of the cloth (yea, those two used to go well together...I can't grasp the concept either) and expected the same for his son, who was a lover of music and science.

"None of that hoodoo voodoo magic in this 18th century household!"

That was his dad...get it?

Well, in true genius fashion, Chladni just waited for the old prude to kick the bucket and then pursued both science and music with a burning passion. As was common of the time, Chladni showed enough intelligence to be given funding to do pretty much whatever he wanted.

TANGENT: How freakin' awesome would it be to have recognition of talent turn into a profession instantly? To have your work actually be an extension of your joy and talent? To not purely be an extension of another being's vision?

The Discovery

What he chose to do with his time led to many an interesting discovery. He posited that meteors came from space, not volcanoes, as was the thought at the time. Influenced by Benjamin Franklin's use of beer bottles and water as an instrument, Chladni created a couple of his own. The first, the "Euphon," was created using glass rods of different pitch compositions. The second was an improvement of Robert Hooke's musical cylinder, called the "Clavicylinder."

chladniChladni's most well known discovery, and the one that earned him the title "The Father of Acoustics," came when he ran a violin bow across a metal plate with sand on it. What he found was that by reaching peak resonance with different plates and with different tones, he could produce intricate patterns, symbolic of both the tone and the plate.

Fascinated by this apparent connection of sound and physical reality, Chladni went on to publish "Die Akustic (The Acoustics)" and toured Europe, displaying his findings.

TANGENT: Rumor has it that, while in France, Chladni met with a rather enterprising young Emperor named Napoleon Bonaparte, who was also fascinated by the sciences. Impressed by Chladni's discovery, Bonaparte financed the translation of Chladni's work into French and offered up 3000 francs to anyone who could scientifically explain the phenomenon.

In his book, Chladni detailed out the various designs created by his experimentation, they went on to become the "Chladni Plates."

Chladni Plates

The Chladni Plates ended up being much more than just beautiful images created by sound, they are actually used to find resonance in the wood of acoustic instruments.

This is done by measuring the modes and nodes of the wood. What are modes and nodes, you ask? Great question.

Modes represent the moving parts of a vibrating surface, while nodes represent the parts that chladniremain still. Imagine, if you will, a xylophone key. Once struck, the middle of the key is pressed down and immediately bounces back up, creating vibration and emitting the tone that the material resonates at. This is the keys mode. The node of the key (the ends) remains still, allowing for sustained vibration and, consequently, the tone.

The same concept holds true for finding wood to work with in the construction of an acoustic instrument. Luthiers test the wood by using black sand on the underside of the top piece and the top side of the bottom piece. They vibrate the wood until resonance is achieved and a pattern emerges in the sand. The pieces are then matched with those that showed the same frequency pattern. This is called, "tuning to frequency."

Unfortunately this process really only occurs in custom made instruments, not the mass produced instruments we commonly find in stores today.

Well, that's all for this week folks. Make sure to check out the amazing vocal project being done using Chladni patterns and plates below.

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2 Comments

  • Cool video, I mean how do you know when to stop - numerous times the plate look pretty cool to me!

  • Each of the patterns represents a different tonality. So, it is less about when to stop and more about the changing of each tone. As the waves that comprise the tone become either more compact or more lengthy, the pattern on the plate changes.

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