In concert hall acoustics, it's the opposite of reflection; the Sabin is a unit of it
Performers may request to rehearse in the concert hall prior to a 
... A sabin is a unit of acoustic absorption equivalent to the absorption by a 
square... [DOC] [TLE] Architectural Acoustics [PAR] Architectural acoustics is defined as the science of controlling sound in a space, 
from grand concert halls to one's living room.