AS 1277-1983

Applies to the objective measurement performance of silencers for ducted ventilating and air-conditioning systems for two types, viz. Type A which have the same dimensions as those of the test duct and the same direction for the inlet and outlet connections, and Type B which have different dimensions from those of the test duct and/or different directions between the axis of the inlet and outlet connections. Two methods are supplied for the determination of the insertion loss of ducted silencers, viz. the direct method and the substitution method.