Wave phenomena can be studied with scaled-down mockups by scaling frequency inversely to size.

Evidence

For a thin wall, the scale of the picture is set by the wavelength. The left panel in figure 2.10 is about 10 wavelengths across in both directions. If someone declares that the frame is physically 100 m across, then the wavelength is about 10 m; from f λ = c, the frequency is about 34 Hz. If the frame is only 10 m across, the wavelength is about 1 m and the frequency is 344 Hz. The picture is correct either way. By this principle, a mockup only 1 meter high could be used to study the diffraction of sound around a highway barrier that in reality is going to be 10 m high, provided all the sound frequencies are increased correspondingly by a factor of 10. This is our first encounter with the law of similarity, which allows us to scale up and scale down studies of wave propagation, diffraction, and so on by scaling the physical dimensions such as wavelength λ by some factor such as 1/10, and scaling the frequency by a factor of 10 so that f λ = c both before and after the scaling. — Eric J. Heller, Why You Hear What You Hear- An…, 189

Categorization

• XREF: The law of similarity also governs optics (diffraction around objects scales with λ) and model testing in aerodynamics — connects to the reader’s understanding of wave mechanics in physics.