This paper describes an analytical calculation of breakout noise by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The breakout noise phenomena from cavities are important at low frequencies, and the coupling between acoustic waves and structural waves plays a critical role in prediction of the transverse transmission loss. The first step in the breakout noise prediction is to calculate the inside cavity pressure field and the normal cavity wall vibration by using an impedance-mobility approach, which results in a compact matrix formulation. The second step is to calculate the radiated sound power from an unbaffled plate formulation that poses formidable challenges on computational time. The proposed formulation helps in reducing the computational time substantially by converting quadruple integrals into single integrals using an appropriate coordinate transformation technique. Analytical results are validated with the finite element/boundary element numerical models. © 2008 Acoustical Society of America.