In principle, sound generated inside a building can be separated into two sources of transmission – airborne sound and sound transmitted through the building itself. Airborne sound, from human activities in adjacent living spaces or from mechanical noise, travels through air, walls, floors and ceilings. Building-transmitted sound can come from occupants in living spaces above, or low frequency noise transferred through the ground and buildings. Measures for controlling noise and reducing unwanted sound are interior sound reverberation reduction, inter-room noise transfer mitigation and exterior building skin augmentation.
Reverberation time is an important parameter for the acoustical experience of indoor spaces. Buildings with ‘soft’ interior surfaces are often more appreciated by occupants and visitors.