Optimal design of broadband acoustic metasurface absorbers

Abstract

The absorption of low-frequency noise has always been limited by structural thickness, but the novel physical properties of sound-absorbing metamaterials provide a solution to this problem. Based on genetic algorithm, an acoustic metasurface absorber (AMA) composed of micro-perforated plates (MPPs) and impedance matching coiled-up cavities (IMCCs) is proposed. Different from previously reported metamaterials, this structure can easily provide flexible and accurate broadband sound absorption in different target frequency bands. The theoretical model behind the algorithm is established, and two optimal structures (AMA I/AMA II) are obtained for low and mid-high frequency bands. Broadband sound absorption is realized with a thickness of only 71 mm (about 1/13 of the relevant wavelength at 369 Hz), and an average sound absorption coefficient of 0.931 is achieved in the low-frequency band of 350–1000 Hz. Furthermore, by changing the frequency band of the quasi-perfect absorber to 500–2000 Hz, the average sound absorption coefficient exceeds 0.945 with a thickness of only 55 mm (about 1/11 of the relevant wavelength at 563 Hz). The reflection coefficient in the complex plane and theoretical impedance analysis are utilized to reveal the underlying mechanism of the absorption and the acoustic characteristics of the two structures, which show excellent broadband absorption performance in the low and mid-high frequency bands. This work provides a method of arbitrarily modulating surface acoustic impedance in broadband and a reference for broadband noise control.

Research on local sound field intensity control technique in metasurface based on deep neural networks

“…Li et al proposed a tandem neural network approach to reverse-engineer the phase of a metasurface unit such that the energy loss of an acoustic wave in the return direction is greater than 10 dB [ 28 ]. Long, Chen et al used genetic algorithms to respectively design metasurface structures for sound absorption [ 26 , 29 ]. Li, Lin, et al have respectively used machine learning for encoding metasurfaces to enable the modulation of the sound field by arranging these logical units into specific sequences [ 30 , 31 ].…”

Simulated and Experimental Research on Highly Efficient Sound Absorption of Low‐Frequency Broadband Acoustic Metamaterial Based on Coiled‐Up Space

“…The theoretical research was conducted on an acoustic metamaterial absorber composed of microperforated plates and impedance‐matching coil‐up cavities, which realized an average sound absorption coefficient of 0.931 in the low‐frequency band of 350–1000 Hz. [ 27 ] However, it had a structural thickness of up to 71 mm and was not further optimized. Simply combining multiple units with perfect absorption peaks together may lead to a sudden decrease in the overall sound absorption performance of the structure because of the impedance coupling effect.…”

Study on the acoustic performance of bending metasurface with ultra-thin broadband quasi-perfect sound absorption

“…Although traditional sound absorption/ insulation materials have been widely used in the engineering field, large and bulky acoustic structures are often required for low-frequency and broadband noise, which seriously limited their applications in noise control [4][5][6]. Therefore, the emergence of acoustic metamaterials with small size control large wavelengths brings new directions for low frequency broadband noise control [7][8][9][10]. In 2000, Liu [11] first proposed local resonant acoustic metamaterials and then a large number of acoustic metamaterials with negative mass density, negative bulk modulus and dual negative characteristics have studied [12][13][14][15].…”