Silencer for industrial and civil buildings with General purpose low pressure centrifugal fan in support. For example: 4-72, 4-73, 5-48, 6-48 series machine, fan, ventilation, boiler blast can be used in the series muffler for lowering the fan intake and exhaust noise. When the silencer through the flow in the 1000-700000m3/h range, muffler compressive <8000Pa, silencing more than 25dB (a).