Abstract
Metamaterials have emerged as promising solutions for manipulation of sound waves in a variety of applications. Negative dynamic mass has been explored in metamaterial applications to improve sound insulation in both three-dimensional (ball-in-rubber), and two-dimensional (membrane-type) approaches. Noise control utilizing locally resonant acoustic materials (LRAM) resulted in improved sound insulation by 500 % over acoustic mass law predictions at peak transmission loss (TL) frequencies. The LRAM contribute minimal added mass, making them appealing for weight-critical applications such as aerospace structures. In this study an overview of LRAM for noise control applications will be presented, including potential issues associated with scale-up of the structure. TL of single-celled and multi-celled LRAM was measured using an impedance tube setup with systematic variation in geometric parameters to understand the effects of each parameter on acoustic response. FEA (finite element analysis) was also performed to predict TL as a function of frequency for structures with varying complexity, including stacked structures and multi-celled arrays. [Work is supported by the Office of Naval Research.]
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