Distributing absorption randomly scatters sound while concentrated absorption leaves modes intact

Evidence

It is not just physically observable bumps on the wall that can cause diffusion of the sound. In fact, any change in the reflecting characteristics of the surface will cause diffusion. The change from an absorbing region on a wall to a reflecting one is an example of a change that will cause the sound to scatter. Thus it is always better to distribute the absorption in small random amounts around a room rather than concentrate it in one particular area. As well as encouraging diffusion, this strategy will avoid the possibility that some modes might shuttle between surfaces with minimum absorption. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2102

Categorization

• QUESTION: Why do concentrated absorbers let certain modes shuttle between minimally absorptive surfaces? Worth chasing the modal interaction mechanism.