Low-frequency ventilated absorbers based on symmetrical space-coiling structure
To eliminate or reduce low frequency noise,a low frequency ventilated metamaterial acoustic ab-sorber is designed.The absorber is composed of symmetrical space-coiling structure and has the characteristics of deep subwavelength,high ventilation rate and high sound absorption at low frequency.Through theoretical analysis,finite element simulation and experiment,the physical mechanism of sound absorption of symmetrical folded channel structure is revealed.Firstly,the ventilation and absorption performance of a single absorber is theoretically analyzed and verified by numerical simulation.At the resonance frequency of 423 Hz,the sound absorption coefficient is greater than 0.9 and the ventilation rate is as high as 40％.Furthermore,metamaterial absorbers with different resonant frequencies are combined to extend the relative absorption bandwidth.The combined absorber composed of four absorber units can achieve efficient absorption over the frequency range of 314-366 Hz(absorption coefficients are greater than 0.8)and ventilation rate up to 35％,while the thickness of the structure is only 1/10 of the wavelength at 314 Hz.The low frequency ventilation absorber has the characteristics of simple structure and easy manufacturing,and has a potential application prospect in the field of low frequency ventilation noise reduction.
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