Diffraction

Diffraction is the bending of sound waves around obstacles and through openings. Unlike light, sound diffracts readily around everyday objects because its wavelengths (0.017–17 m in air) are comparable to the dimensions of walls, screens, and barriers. Low-frequency sounds diffract more than high-frequency sounds, which is why bass passes easily around office partitions while speech consonants are blocked. Diffraction is quantified in barrier insertion loss calculations using methods from ISO 9613-2 and the Maekawa formula. In room acoustics, diffraction affects the effectiveness of partial-height screens in open-plan offices (ISO 3382-3) and explains why small gaps around doors significantly reduce sound insulation. Proper detailing of seals and junctions is critical to achieve rated insulation performance.