Design and Optimization of Acoustic Metamaterial for Focusing and Noise Reduction

Wave manipulation of low-frequency sound remains a major challenge in the field of acoustics. It is desired to amplify or diminish the sound intensity efficiently using rather small devices. This is challenging because the dimension of conventional acoustic devices should be more than the wavelength of the sound leading to designs well beyond a meter in dimension. Hence, it is quite impractical and costly to use conventional methods to manipulate low-frequency sound. Acoustic metamaterials can be designed to more effectively manipulate sound waves even when they are quite smaller than the wavelength. In this work, we present analysis and optimization of meta-materials for focusing and noise reduction at targeted frequencies. For noise reduction, a simple Wunderlich curve was chosen as the initial design and its size and shape were optimized to reduce noise levels at the outlet of a duct while allowing passage of fluids. For sound focusing, an optimum design was found which outperformed previous designs while reducing the number of cylinders required. As a result, we were able to reduce noise inside the duct by over 99% and magnify the intensity at a point by 16 dB at targeted frequencies of sound. The efficiency and tunability of the metamaterial designs allow numerous applications in fields of biomedicine, aerospace, civil, military, and communication.