In 1787 the German jurist, musician, physicist and astronomer Ernst Florens Friedrich Chladni published Entdeckungen über die Theorie des Klanges (Discoveries Concerning the Theory of Sound), laying the foundations for what came to be called acoustics, the science of sound. Chladni introduced a method to make sound waves visible and to show how sound actually does affect physical matter and has the quality of creating geometric patterns: With the help of a violin bow which he drew perpendicularly across the edge of flat plates covered with sand, he produced those patterns and shapes which today are known as Chladni Patterns (see also HERE & HERE & HERE & HERE).
These Patterns show primarily two things (see below): areas that
are vibrating and areas that are not. When a flat plate of an elastic material is vibrated,
the plate oscillates not only as a whole but also as parts. The boundaries
between these vibrating parts, which are specific for every particular case, are
called node lines and do not vibrate. The other parts are oscillating
constantly. If sand is then put on this vibrating plate, the sand (black in the
illustration) collects on the non-vibrating node lines. The oscillating parts or
areas thus become empty. The converse is true for liquids;
that is to say, water lies on the vibrating parts and not on the node lines.
