Structural radiation mode sensing for active control of sound radiation into enclosed spaces

In the recent article by Cazzolato and Hansen [J. Acoust. Sec. Am. 104, 2878-2889 (1998)] it was shown that it is possible to derive for a structure some set of surface velocity distributions, referred to as radiation modes, which are orthogonal in terms of their contributions to the acoustic potential energy of a coupled cavity. The technique used an orthonormal decomposition to derive an expression for the radiation modes which was based on prior work for free-field sound radiation. It will be shown in the following letter that for the special case involving the calculation of global internal potential energy it is possible to use a simple approach which requires no orthonormal decomposition since the expression for the global potential energy is already in a form that can be easily diagonalized. (C) 1999 Acoustical Society of America. [S0001-4966(99)04112-0].