The efficacy by which sound energy is spread evenly in a given space. In a diffuse sound field sound propagates with the same energy in all directions. This is often created for measurement rooms in acoustic laboratories. In a non-diffuse sound field sound can be more dominating is some directions. Non-diffuse sound fields can be found in more or less all rooms outside laboratories. A room with a very non-diffuse sound field is for example, a room with a sound-absorbing ceiling and no furniture.