Application of acoustic metamaterial with stop band to panel and cylinder

With regard to improving the acoustic insulation of mechanical structures, such as payload fairings, the alternative to conventional methods (e.g. by mass law, sound absorption materials) is demanded. Owing to the absence of the wavelength dependence, acoustic metamaterials with stop band, the frequency zone preventing the propagation of sound wave, based on the principle of localized resonances have attracted much interest in recent years. The aim of this study is to develop new types by applying the proposed resonance: the panel with a new twist and the cylinder whose resonators are tuned to around the frequency zone of ring modes, which sound transmission is remarkable. Acoustic properties of each products, such as an acoustic sensitivity and a transmission loss, were measured and calculated by using finite element method where relevant as well as normal models. The former experimental result suggests the potential of the new design concept and the latter indicates the obvious wave attenuation around the frequency zone compared with a normal cylinder. These imply the validation of both demonstrators, which is expected to be applied for actual products.