Disclosed herein are systems and methods for information organization whereby characteristics regarding entities are inferred from the characteristics of similar entities. The duct includes a first wall 2 made of a porous material, wherein a film 4 is implemented which is sufficiently thin for avoiding any incidence upon the acoustical characteristics, having notably a surface mass of less than 100 grams per square meter. Then a foreground sampling window having a non-patterned area defined by the entry object is defined.