Effect of stiffener resonances on the vibration response and sound transmission loss of periodically stiffened structures

Abstract

In analyzing the problem of vibration response and sound transmission through periodically stiffened plates and cylinders, the stiffeners are very often represented by line supports or by springs with equivalent translational and torsional stiffnesses. Sometimes, the effects of the stiffeners are also smeared out. As a result, the vibrational response and the transmission loss at low frequencies are often predicted to be stiffness controlled. Recent studies at Boeing has shown that in the “stiffness controlled” region, the structural response and noise transmission may be governed by the resonances of the stiffeners, depending upon the relationship between the natural frequency of the plate between the stiffeners and that of the stiffener. Therefore, noise transmission in the “stiffness controlled” region may be effectively controlled by applying damping treatment on the stiffeners. This recent understanding has grown out of the “intrinsic structural tuning” concept presented earlier (G. SenGupta and E. F. Small, J. Acoust. Soc. Am. 58, S (A)(1975). The problems under consideration are discussed in terms of (1) stringer‐stiffened plates and (2) frame‐stiffened cylinders. Analytical as well as experimental results are presented. [Work supported by NASA‐Langley Research Center.]