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Study the Sound Insulation of Elastically Restrained Panel

Experimental determination of the acoustic characteristics of a sound insulation panel often requires a standard measurement suite consisting two rooms connected via a window onto which the panel is mounted. While such a facility is quite expensive to build and maintain, the measurement results can show a significant variance, especially at low frequencies. The potential causes may include the characteristics of the rooms, the placement of the sound source(s), the installment of the panels, etc. To better understand the variance of the results and identify the directions for improving the sound insulation designs and applications, a virtual testing capability is developed based on an analytical parametric model. This model consists of a source room, a receiving room, and a partition wall with a mounting window. The sound insulation structures can represent a simple panel or a complex structure with various structural and/or acoustical design features. This model can be effectively used to virtually test the acoustic performance of sound insulation designs under different environments and application conditions. Introduction Structural-acoustic coupling is of interest to automotive, aerospace and other industries. The sound transmission through an elastic panel between two rooms is of significance to the calculation of the sound transmission loss of panel-like structures. A literature survey of the structural-acoustic coupling shows that a large amount of work has been done in calculating free and forced responses of cavity-panel-cavity systems. The standards for the determination of sound insulation of building elements are derived assuming that the sound fields in both rooms are perfectly diffuse, i.e., with equal probability of energy flow in all directions[1]. The diffuse field assumption is only valid in medium and high frequency ranges, since at low frequencies the sound field in the reverberation chambers is dominated by a few normal modes. It has been concluded that the actual standards did not provide essential improvements of the accuracy at very low frequencies[2]. To better understand the sound transmission through the two rooms via the panel, analytical and numerical methods have been used. Modal analysis[3] is adopted to study the errors in sound transmission measurements. Maluski and Gibbs[4] have employed the FEM to study how the configuration of two identical reverberant rooms influences the transmission loss of a partition at low frequencies. Jo and Elliott[5] studied the sound insulation properties of the panel mounted between adjacent rooms and give a strategy for active control of the low-frequency sound transmission between rooms. Xiang, et al.[6] studied the sound energy decays consisting of multiple exponential decay rates in the coupled-volume systems. Papadopoulos[7] proposed a virtual laboratory to represent a real laboratory consisting of two reverberation rooms to study the TL of the panel based on the technology of acoustic measurements and standards. Compared to the conventional level difference method to measure the TL of the panel, newer technique base on the measurements of sound intensity on the receiving room side of the partition are widely used due to the advances in instrumentation and technology. Halliwell and Warnock[8] compared the conventional method and the intensity method to measure the TL of the panel and found significant differences between the two measurement techniques at low frequencies and high frequencies.