Dirasat, Engineering Sciences, Volume 36, No. 2, 2009 - 118 - Partition Sound Insulation of 51 STC for the Jordan Gate Project Rizeq Hammad and Hani Obeid* ABSTRACT A double-leaf gypsum board partition was tested under laboratory conditions to investigate if it meets the Hilton Hotels criterion for sound insulation between bedrooms of 51 STC. According to American Gypsum, this partition should provide sound insulation of 50 STC (Gypsum Association, 2003). Testing revealed that only 45 STC was achieved. Additional horizontal studs were used to increase the stiffness of the partition and a third layer was added on one face to overcome the resulting coincidence effect. This yielded a partition with insulation of 51 STC, which meets the Hilton Hotels criterion. Keyword: Sound Transmission Class, Transmission Loss (SLD), Normalized level difference (DnT). 1. INTRODUCTION This paper describes laboratory sound-insulation testing of a double-leaf gypsum board partition. According to American Gypsum, (Gypsum Association, 2003) this should provide sound insulation of 50 STC. The contractor of a 40-story building as part of a twin tower of Jordan Gate project, to minimize the dead load of the building, suggests this partition. The partition was tested in the laboratory of the Faculty of Engineering and Technology, Jordan University, but failed to meet the Hilton Hotels criterion of 51 STC or the recommended STC insulation by the Gypsum Company. We added elements to improve the insulation and obtained a partition that meets the criterion of Hilton Hotels. 2. BACKGROUND The insulation provided by a double-leaf partition with an air gap of thickness d is described by the equation: (Balilah, 1987) 2 2 1 2 10 TL 10 log 1 cos cos cos sin 2 m m c c θ ω ω θ β θ β ρ ρ ⎡ ⎤ ⎛ ⎞ = + − ⎢ ⎥ ⎜ ⎟ ⎢ ⎥ ⎝ ⎠ ⎣ ⎦ Where: cos kd β θ = ; 2 k π λ = ; θ is the incident angle for sound wave; m1 and m2 represent the density of the two layers [kg/m 3 ]; ω: is the angular frequency; ρc: is the characteristic impedance; And λ is the wavelength of the sound wave [m]. When the sound wave is incident in all directions, i.e., a diffuse field, the transmission loss (TL) is calculated according to: (Beranek, 1960) 10 4 1 1 1 TL TL 10log dB 2cos 2 sin θ θ θ ⎡ ⎤ = − − ⎢ ⎥ ⎣ ⎦ . If θ=78°, the equation becomes: TL TL 28 dB θ = − . This is valid when the two layers are of the same material, the incident waves are less than the critical wave, and the mass law is valid. (Hammad, 2006) For practical use, the above equation can be simplified to: (Ginn, 1978) ( ) [ ] 10 1 2 10 TL 20log 20log 1 0.3 dB m m f d k = + + + − Where k varies between 26 and 41, depending on the connection elements between the two layers. 3. DESCRIPTION OF THE PARTITION The partition is described by the Gypsum Association as two layers of type X gypsum board applied parallel to each face. Each layer is 12.5 mm thick with 125-mm steel studs (600 mm o.c.) with 25-mm type S drywall screws (300 mm o.c.). A 50-mm mineral wool fiber of 80 kg/m 3 * Department of Architecture, Faculty of Engineering and Technology, University of Jordan, Amman, Jordan; Department of Electrical Engineering, Applied Science University, Amman, Jordan. Received on 17/9/2008 and Accepted for Publication on 11/11/2009. © 2009 DAR Publishers/University of Jordan. All Rights Reserved.