Sound Radiation from a Housing Having a Latticed Rib

Regarding a latticed rib as a sound reflector, its effect on sound radiation from a housing is discussed. A module of the reflector, a box with a baffle, surrounding four rectangular reflector plates and an aperture, is taken up for proposing a new formulation in terms of mirror images. Taking multiple reflections into account, the reflecting process is replaced by diffractions from an array of mirror images toward the aperture through the diffraction windows corresponding to the reflectors. And only centripetal diffractions to the aperture are selected for the convergence in calculation. The formulation is applied to a latticed reflector by summing the sound radiation from each module of reflector, When the ratio of bending wavelength in the housing plate to the wavelength of sound in air is greater than 1, the rib has some effect of decreasing the radiation power. Under the contrary condition, the power increases remarkably due to the existence of the rib.