The theory of geometric optical diffraction has been used to investigate the effects of sound diffraction at the edge of a loudspeaker cabinet. The asymptotic assumption of the optical theory is examined by the use of the finite-element method. Comparisons are made between the two different methods, indicating the accuracy of the optical method for perpendicular incidence of the sound wave. Experimental evidence indicates that the optical method is not correct for nonperpendicular incidence. An improved formulation of the optical method is proposed which yields results more consistent with experiments with accepted theoretical approaches.
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