Abstract
A variational method for treating the diffraction of sound is applied to the case of an infinitely thin rigid rectangular plate, for which no exact solution is known at present. Utilizing the integral equation, the diffraction coefficient is expressed in a form which is stationary with respect to small variations (relative to the correct values) of the difference in velocity potential on opposite plate faces. And numerical calculations of the diffraction coefficient and the radiation pressure on the plate are made for a/b=1, 0. 5, and 0. 25, where 2a and 2b are the lengths of the sides respectively.
