How To Build A Quadratic Residue Diffuser (QRD)

FREE Soundproofing Workshop: QRD Calculator: One of the most effective and efficient types of diffusers are reflection phase grating diffusers otherwise known as Schroeder diffusers. A type of Schroeder diffuser is the Quadratic Residue Diffuser (QRD) and in this article I will teach you how the diffusers work, the theory behind them, and how to build one. 1) How Does a QRD work? Manfred R. Schroeder developed the quadratic residue diffuser by using a series of wells of different depths with a constant width that are separated by thin dividers to evenly disperse sound back into the room. (Everest, 265). He found that a number sequence based on prime numbers can be used to calculate the depth of each well. This number sequence can also be repeated over and over (in periods) to expand diffusion across a wall or ceiling. When designing a QRD the maximum frequency for diffusion is deter