How does wavelength affect the diffraction of sound around an obstacle?

Diffraction is the process by which waves spread around obstacles or through apertures. The extent to which sound diffracts is fundamentally dependent on the relationship between the wavelength of the sound and the physical dimensions of the obstacle.12

• Comparable Sizes: Diffraction is most pronounced when the wavelength is of the same order of magnitude as the obstacle. Because audible sound waves often have wavelengths around one meter, they readily diffract around everyday objects, which is why sound can be heard around corners.32
• Large Wavelengths: If the wavelength is large relative to the obstacle, the wave passes by virtually unaffected, diffracting around the object in a series of Huygens’ wavelets.2
• Small Wavelengths: As frequency increases and wavelength shrinks, the ability of a sound wave to diffract decreases. When the wavelength is small compared to the obstacle, the wave does not diffract strongly, instead forming a distinct shadow similar to those produced by light.2

This relationship explains why lower-frequency sounds (longer wavelengths) bend around corners more easily than higher-frequency sounds, which tend to form more directional beams.2