In modern society the problem of excessive noise in residential areas and workplaces caused by, such as road traffic and the HVAC system, is remained as an issue waiting to address in further. In 1958, the acoustic plenum chamber (PC) was introduced as a passive sound attenuator and acoustic silencer. Since then, it is widely used in HVAC systems and inside engines for noise attenuation, not only due to its ability of mitigating noise but also its guarantee of a satisfactory degree of natural ventilation and avoidance of consuming extra energy, maintaining sustainability. Nonetheless, at the same time, its limitations in bandwidth and the potential to further enhance the performance should not be ignored as well. Meanwhile, over the past two decades, the development and investigation of Acoustic Metamaterials (AM), such as Sonic Crystals (SC) and Locally Resonant Materials (LRM), have proven their significant ability in noise reduction (or even blocking) within specific frequency ranges. With this remarkable property, an acoustically stronger and more effective acoustic device that integrates AM into the PC comes with the territory. A few experimental and simulation results concerning simple embedded AM structure in PC do exist in literatures but the theoretical study of it (and of more complicated types of AM inclusion) remains untouched. The seminar will thereby focus on the theoretical aspect of this integration and a homogenization scheme stemmed from Effective Medium Approach (EMA) will be introduced in the hybrid modelling of rigid scatterers, Helmholtz Resonators, and elastic shell inclusions, using the Finite Element Method (FEM) at the low-frequency regime. In light of the precise accuracy of results, this hybrid modelling approach may be considered much computationally easier, cheaper, and more timesaving than direct modelling.
Mr. Wai Kit Lam (Adrian) is Ph.D. student from the Department of Building Environment and Energy Engineering (BEEE) of the Hong Kong Polytechnic University, and he has been a visiting research student at the Department of Mechanical Engineering of the University of Sheffield with the support of BEEE since November 2022. Under the supervision of Prof. Shiu Keung Tang (University of Hull) and Dr. Anton Krynkin (University of Sheffield), Adrian is currently focusing on a practical research topic of acoustic analysis of plenum chamber (or plenum window) embedded with Acoustic Metamaterials, which simultaneously provides a satisfactory level of sound insulation and maintains sufficient natural ventilation. His research is conducted using theoretical analysis, numerical simulation, experimental method and as well as other hybrid approaches. He has published one journal paper and two conference papers on the experimental and numerical results respectively.