Acoustical materials are define as "the materials having acoustical function". Their function is various, such as absorption, sound insulation, dumping, and so on. Historically, they were started to use in architecture, but now, they are very widely used at the place where the quietness is desired, like sound packages and interior materials in automobiles and aircrafts. Formerly, it took very long time for the development of such acoustical materials. It is necessary to stack several materials as layers to obtain a good absorption or sound insulation performance with thin and light-weight construction. Especially, to predict the acoustical performance of such layered materials has been very difficult. The simulation software STRATI-ARTZ from Nittobo Acousitic Engineering is an evolutional software to predict these acoustical performance.