Thursday, June 29, 2006

Chladni Day at Soundwave Research Labs

Sometimes referred to as Ernest Florenz Friedrich Chladni. He lived from November 30, 1756 to April 3, 1827. We celebrate June 29th as Chladni Day in Massachusetts, Maine and Puerto Rico. I have asked Hallmark to produce commemorative cards to celebrate the life and work of Chladni.

Today we honor Ernst Chladni, the German scientist who elucidated fundamental principles of quantum theory through his investigations of vibrating plates. "Chladni Plates" are metal discs or squares upon which sand is poured. The edge of the plate is bowed with a violin bow, the vibrations propagate across the plates and moves the sand, and all sorts of interesting interference effects and patterns become visible, as the sand collects in the antinodes.

I like Chladni a lot because his work explains why ribbon microphones sound better than condenser microphones. The basic reason is that the ribbon microphone is predominantly a two dimensional system, with fewer overtones. lateral modes and generally unwanted resonances ("forbidden modes" to you quantum folks) in the band of interest (music) than the three-dimensional system of a disc moving with tympanic action, AKA the condenser membrane.

Investigate quantum principles without doing the math! Select "rectangle" Let m = 1 and let n = 10. Click on "plot" and observe. What do you see?

Then switch to "Circle". Plug in m= 1 and n = 5 ( which can be the case with a large diaphragm condenser) What do you see? "Tuners" re-tension the capsule for reduced lateral modes. You can too.

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