Theory of Sound Transmission through Suspended Ceilings over Partitions

Abstract

Two adjoining rooms are considered to be separated by a perfect partition extending only to a suspended ceiling. A source in one room produces there a reverberant field of energy density D1. In the other room an energy density D2 is produced by sound which originates in the source room and travels the path : source room ceiling, plenum, receiving room ceiling. A theory is developed which relates the ratio (D1/D2) to the transmission coefficient of the suspended ceiling, the absorption coefficients of the plenum boundaries, the total absorption of the receiving room, the lateral dimensions of the two rooms, and the depth of the plenum. The ratio (D1/D2) is found to be quite sensitive to variation of both the transmission coefficient of the suspended ceiling and the absorption coefficients of the horizontal plenum boundaries. For three types of suspended ceilings calculated values of (D1/D2) are compared with experimental values obtained by Hamme, some of which he published in NOISE Control [5, 64 ff (January, 1959)]. Agreement between theory and experiment is encouraging.