The acoustic laboratories supplied by Landtop Technology are equipped with broadband composite absorbers (BCA) or asymmetric sound absorbers (ASA), both of which have been mass-produced stably for many years. This reactive absorber technology was jointly developed by Landtop and IBP, and multiple international patents have been granted in Europe and the United States (Patent Numbers: US5975238, US 6793037 B1, US 6073722, EP 0811097B1, DE10213107 A1, DE19861016 C2).