A mass-spring analogy for modeling the acoustic behaviour of a metamaterial

Absorbing sound almost completely at specific frequencies with conventional acoustic materials whose thickness is least 60 times smaller than the wavelength a challenge, particularly low frequencies. Fort this purpose, metamaterials are of great interest. Here, metamaterial called multi-pancake cavities. It composed main pore repetition thin annular cavities (pancake cavities). Previous research has shown that increases effective compressibility pore. This increase makes it possible to decrease speed in material and, consequently, resonance At these resonances, presents absorption peaks, first one can have ratio more (subwavelength material). To complete analysis and prediction peaks (especially secondary peaks) metamaterials, proposed adapt mass-spring model metamaterial. Due small cavity length-to-diameter ratios, radial propagation considered inside shows good agreement results obtained by finite element method impedance tube measurements. Finally, comparisons previous theoretical approaches presented discussed.