Improvement on sound transmission loss through a double-plate structure by using electromagnetic shunt damper

Abstract

It is well-known that the acoustic sound performance of double-plate structures deteriorates rapidly around the mass-air-mass resonance frequency. In this study, a electromagnetic shunt damper (EMSD) connected between incident and radiating plate is used to improve the sound transmission loss at low frequency ranges. The EMSD consists of a coil, a permanent magnet, and a specially designed shunt circuit. First, a full structural-acoustic coupling modal model is developed to analyze the vibration and acoustical behaviour of the double-plate structures with EMSD system. Then two EMSD shunt circuit configurations, namely negative resistance (NR) and negative resistance series with capacitance (NR-C), are proposed to control the sound transmission. The control performance of the EMSD is investigated based on different parameters of the shunt circuits. Finally, the experiment was performed to verify the proposed theoretical model of EMSD. The numerical and experimental results show that, the sound transmission loss around the mass-air-mass resonance frequency can be improved significantly by using the EMSD with NR or NR-C shunt circuit. However, EMSD cannot control the first in-phase mode of the double-plate structure.