Improvement on sound transmission loss through a double-plate structure by connected with a mass-spring-damper system

Abstract

It is well-known that the acoustic performance of double-plate structures deteriorates rapidly around the mass-air-mass resonance frequency. In this study, a mass-spring-damper system connected between incident and radiating plates is used to improve the sound transmission loss at low-frequency ranges. First, a full structural-acoustic modal coupling model is developed to analyze the vibration and acoustical behaviour of the double-plate structures with mass-spring-damper system. Because there are in-phase or out-of-phase vibrations between double plates, tuning the natural frequency of the mass-spring-damper system exactly to the mass-air-mass resonance frequency cannot guarantee the maximum improvement on transmission loss. Optimal natural frequency and mass of the mass-spring-damper system were found as a solution of optimization problem with a global cost function defined as frequency-averaged sound transmission loss in the desired frequency range (around mass-air-mass resonance frequency). Finally, some numerical calculation results are presented. The calculated results show that the sound transmission loss of a double-plate structure can be improved significantly using optimally tuned mass-spring-damper system. The results indicate that an overall improvement of 12 dB below 1000 Hz can be achieved when the mass of the mass-spring-damper system equals to 10% weight of the double-plate structure.