'Colour Sound' video shows the geometry of sound

Musician Kenichi Kanazawa's 'Colour Sound' video offers a glimpse into how sound waves interact with the world around us.

Science Notebook

You may have heard a Tibetan singing bowl before. It’s essentially an inverted bell that is sounded by running a mallet around the lip of the bowl, causing it to vibrate and produce several frequencies of delicate sound. But what about a “singing table"? That’s essentially what musician Kenichi Kanazawa has created, producing a steel tabletop that vibrates at particular frequencies when it’s struck with a rubber mallet.

Mr. Kanazawa is a sculptor and artist whose work focuses on making invisible forces visible. In the video “Colour Sound,” he places four small piles of sand, colored red, yellow, green, and blue, on top of his “singing table” and strokes the edge of the table with a special mallet. As the table vibrates, the piles of sand spread out, forming geometric shapes.

Kanazawa employs several different mallets, each of which causes the steel table to vibrate at a different frequency. At a very low vibrating frequency, the sand forms a simple circle; at higher frequencies it forms more complex shapes, such as stars and snowflakes.

The “singing table” art piece is an example of cymatics, the study of sound through visible vibrations. Scientists employ cymatics by coating a thin plate or membrane with liquid or a layer of particles (such as Kanazawa’s sand), then vibrating the apparatus in accordance with a certain sound wave to see how that wave behaves. The English astronomer and physicist Robert Hooke, who observed Mars and Jupiter through early telescopes and pioneered the use of microscopes in scientific work, used cymatics in 1680 to observe the wave patterns created by certain sounds.

How does it work? Every sound causes the air to vibrate at a particular frequency. Complex sounds such as music and human speech take place over a variety of frequencies, but Tibetan singing bowls, on which Kanazawa’s table is based, generally vibrate at a single fundamental frequency, with one or two harmonic overtones above it. The fundamental frequency is a sound wave with a particular wavelength; the first harmonic is a wave exactly half as long as the fundamental; the second harmonic is a wave a third as long as the fundamental; and so on.

As Kanazawa’s table vibrates at different frequencies, the sand arranges itself in a visual analogy of the sound wave being produced. Higher frequencies produce more complicated shapes, in an illustration of Chladni’s Law, named after Ernst Chladni, a German musician and physicist who studied vibration modes in flat surfaces.