National security and a beautifully resonant violin have found a surprising link — a classic experiment in acoustics, recently replicated at the quantum scale as part of a collaborative project on quantum-enhanced motion sensing.
UC Merced Professor Michael Scheibner and U.S. Naval Research Laboratory scientist Samuel Carter’s discovery — the cover story in a recent issue of Applied Physics Letters — may one day lead to technologies that help uncover hidden nuclear threats.
Physical objects can be made to resonate at particular frequencies depending on the size, shape and material from which they’re constructed. But visualizing an object’s acoustic properties wasn’t possible until the late 18th century, when physicist Ernst Chladni devised a pioneering experiment that bridged the gap between sight and sound.
The Chladni plate experiment was an ingeniously simple way to visualize resonance. Placing a thin layer of sand on a metal plate, Chladni drew a violin bow along the plate’s edge to produce vibrations. As the plate resonated, the sand on the plate’s surface was sent scuttling, until it finally came to rest in striking geometric patterns.
The sand wasn’t settling just anywhere. It was collecting at nodes, points on the plate’s surface that remain still while the rest of the plate vibrates. The sand was forming patterns that were essentially visual representations of sound waves traveling through the solid surface.