A novel butterfly double-panel metastructure filled with porous materials for broadband low-frequency sound absorption

Traditional resonant sound-absorbing materials and structures, as the main components of building sound-absorbing structures, have limited overall noise reduction capabilities under spatial dimension constraints, and cannot meet the requirements of indoor low-frequency broadband sound absorption and deep subwavelength characteristics. This poses new challenges for the acoustic performance design of building sound-absorbing structures. Based on that, a novel butterfly-shaped double-layer Helmholtz resonator acoustic metamaterial structure lined with porous materials in the present work. The structure was simulated using the finite element software COMSOL and verified by acoustic absorption test experiments with standing wave tubes. The results show that the melamine foam lining of the structure can make the structure have excellent sound absorption performance in the frequency range of 400 600Hz, and the average sound absorption coefficient is greater than 0.9, and the average sound absorption coefficient is greater than 0.8 in the frequency range of 600 700Hz. Quasi-perfect absorption of sound waves is achieved. The resonant absorption peak of the sound-absorbing structure at 420Hz is 0.99, and the thickness of the structure is only 1/14 of the wavelength corresponding to the absorption peak frequency, which reflects the characteristics of its deep subwavelength size. When the height of the structure is 60 mm, there is still a wide sound-absorbing frequency band with a bandwidth ratio of 76 % (sound-absorbing coefficient >0.5). The design of the novel butterflyshaped double-layer Helmholtz resonator acoustic metamaterial structure provides a new approach to noise reduction in building sound-absorbing structures.