Any change in surface reflectivity, not just bumps, causes sound diffusion

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. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2102

Categorization

• SEED: Distributing absorption in small random amounts rather than one area — a metaphor for resilience and redundancy that could anchor a crossover essay on acoustic design philosophy.
• XREF: Connects to the reader’s interest in how room acoustics shape perception, echoing points in One Square Inch of Silence about how surfaces scatter or absorb sound.