Pset_DuctSilencerPHistory Duct silencer performance history common attributes. IfcDuctSilencer IfcDuctSilencer AirFlowRate Air flow rate. Volumetric air flow rate. Air Flow Rate 風量 体積風量 AirPressureDropCurve Air pressure drop as a function of air flow rate. Air Pressure Drop Curve 圧力降下曲線 風量の関数としての空気圧力降下 ダクト消音器の性能履歴共通属性。