Understanding diffusion versus scattering devices and how they work

Abstract

Nearly 50 years ago, Dr. Manfred Schroeder defined the word “Diffuser” as both a process and a product. Since then, many product manufacturers, acousticians and academics have come to use the term for many different products and designs. A careful reading of Dr. Schroeder's 1975 and 1978 papers reveals a lot of significant information as to why certain products are diffusers and why other products do not meet his criteria for diffusion. This paper will show, with the aid of Schroeder's interpretations and modern particle simulations, exactly what he had in mind when he, and others he was working with, created what ultimately became the Quadratic Residue Diffuser or QRD. Additionally, it will show his journey from primitive-root theory to his final quadratic designs. A discussion of the term “Scattering” will also be included to define how Schroeder uses the word and why we need to be careful as to how it is used as well. Test data showing phase models will be used to show the importance of phase manipulation in describing diffusion.