Room acoustics describe how sound behaves in an enclosed space: how it reflects off hard surfaces, gets absorbed by soft ones, and either creates a sense of calm or an exhausting background hum. Most people notice bad acoustics (echo in a tiled kitchen, the way every conversation carries in an open-plan flat) without being able to name the problem.
Material choice is the largest factor you can control. Dense, hard surfaces (concrete, glass, ceramic tile) reflect sound waves. Softer, porous materials (wool, cork, wood fibre, clay plaster) absorb them. A room with a mix of both can feel dramatically different from one dominated by hard finishes.
The Sound of a Room is a good entry point, covering the basics of how materials affect what you hear. Sound, Focus, and Walls That Listen applies acoustic thinking to workspaces. What Makes a Room Feel Calm connects sound to the broader sensory picture.
