Sound absorption is responsible for the “audibility” in a room. How “reverberant” a room seems or how loud a source of sound appears is dependent on the sound absorption. How do you define “sound absorption”?
What we understand by this is reducing the sound energy in a room through sound waves losing energy on component surfaces. The energy of the sound waves is absorbed or reflected by the enclosing surfaces, as well as objects and people within the room. The correct sound absorption ensures that the sound in a room is perceived as louder or quieter. The ability of a material to “swallow” sound waves depends on the materials properties. Porous, open-cell or perforated materials normally absorb sound very well.
“Good audibility” in a room describes the conditions that enable the best possible transmission of a sound source to the listener.