Sound transmission of cavity walls due to structure borne transmission via point and line connections

Abstract

The author has published equations for predicting the air borne sound transmission of double leaf cavity walls due to the structure borne sound transmission across the air cavity via (possibly resilient) line connections, but has never published the full derivation of these equations. The author also derived equations for the case when the connections are rigid point connections but has never used them or published them or their derivations. This paper will present the full derivation of the author's theory of the air borne sound transmission of double leaf cavity walls due to the structure borne sound transmission across the air cavity via point or line connections which are modeled as four pole networks. The theoretical results will be compared with experimental results on wooden stud cavity walls from the National Research Council of Canada because the screw spacing is given for these results. This enables connections via studs and screws to be modeled as point connections and avoids the need to make any assumptions about the compliance of the equivalent point or line connections.

The acoustic radiation impedance of a rectangular panel

“…The variable r is also the ratio of the power radiated by the resonant vibrational fields to the power radiated by the vibrational near fields for a panel excited by point forces acting at right angles to the panel [5]. The radiation efficiency of a panel excited by point forces acting at right angles to the panel is (see equation (28) …”

“…The ratio of the power radiated by the resonant vibrational fields to the power radiated by the vibrational near fields for a panel excited by line forces acting at right angles to the panel [5] is…”

Investigation of transmission loss through double wall structures with varying small air gaps using modal analysis.

“…To extend the theory, numerous papers have been published describing the effects of the different variables that drive the performance of the double wall structures [4][5][6][7][8]. These variables are experimentally studied in the literature and include but are not limited to the thickness of the individual walls, material of the wall, thickness of the gap between walls, composition of the gap, stud locations, stud material and screw spacing [4,8]. Typically, the research in the area of double wall transmission loss has been centered around the construction industry, focusing on relatively large wall areas and gap spacings [4,[8][9].…”

“…Additionally, there is a concentration in the literature on building materials such as wood, fiberboard, and gypsum boards [8][9]. There are studies that have investigated metal wall constructions including steel studs, and either steel or aluminum wall faces, but the focus on larger gap spacing has remained [4].…”

Recent advances in building acoustics: An overview of prediction methods and their applications

“…These structures include single-leaf M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 21 walls, double-leaf cavity walls, rib-stiffened plates, and floating wall systems. Davy [120] produced a method for predicting structure-borne sound transmissions across an air cavity via line and rigid point connections theoretically. Dickow et al [121] noted that the classical SEA method was not appropriate in conducting structural acoustic prediction of rib-stiffened plates.…”