Room acoustics describes how sound waves originate, propagate, and are absorbed within a building. Architects consider reverberation time, reflections, and absorption already during the design phase. Hard surfaces such as concrete or glass reflect strongly, while textiles, wood paneling, or acoustic panels absorb sound. Concert halls, speech rooms, and offices require different acoustic profiles. Digital simulation tools allow prediction of acoustic behavior before construction. Room geometry, such as curved ceilings or diffusers, also directs sound waves deliberately. Errors in planning lead to disturbing echoes or poor speech intelligibility.