ABSTRACT
A diffuser needs to break up the reflected wavefront. This can be achieved by both shaping a surface and making the surface impedance vary across the front face of the device. Indeed, Schroeder diffusers are often interpreted as a set of wells that create a spatially varying surface impedance. In this chapter, varying impedance is achieved using patches of absorbent alongside reflecting materials. Unlike the Schroeder diffuser, these hybrid devices cannot be designed for minimum absorption. These surfaces are somewhere between pure absorbers and non-absorbing diffusers. Partial absorption is inherent in the design while any reflected sound is dispersed.
