Noise Reduction Using Wunderlich Curve and Shape Optimization

Low frequency acoustic noise remains a challenge in many fields ranging from residential to aerospace applications. The large wavelength of low frequency waves can only be absorbed by impractically thick mediums. Recent studies demonstrated the possibility of low-frequency noise reduction using sub-wavelength acoustic metamaterials. In this work, we proposed a novel metamaterial design developed by a combination of shape optimization and Isogeometric Analyses. A classical Wunderlich curve was considered as the initial design and the shape and size of the metamaterial was developed numerically to optimize noise reduction in free space. More specifically, the metamaterial cells were placed inside a duct and subjected to an incoming plane wave with low frequency. The numerical analysis captured the wave manipulation inside and around the metamaterial cell. It was shown a combination of two cells is necessary to achieve the desired noise reduction levels. As a result of this study, we designed an optimum metamaterial that can significantly reduce noise levels in a sparse arrangement with promising civil and military applications.