Insertion loss of stiffened enclosures

The paper reports a theoretical study of the insertion loss of close-fitting enclosures made of stiffened plates in low frequencies. The theoretical analysis is based on, the Finite Element Method for the structural part, and the classical solutions suggested in [1] for the acoustic part. The effects of, boundary conditions, acoustic resonances and structural resonances on the insertion loss, are studied. The theory shows two important points; 1) the contribution of the non-fundamental mode of the source plate is important for insertion loss as the enclosure; and 2) Stiffeners can be used to enhance the insertion loss ability of an enclosure plate at the frequencies below the fundamental resonance. However, in other frequencies, the enclosure plate could give worse insertion loss performance.