对称折叠通道结构的低频通风吸声体

Low-frequency ventilated absorbers based on symmetrical space-coiling structure

为了消除或减少低频噪声,该文提出了一种低频通风超材料吸声体。该吸声体由对称的折叠通道结构组成,具有深度亚波长、高通风空间占比和低频高效吸声的特性。通过传递矩阵方法、有限元模拟和四传声器实验法,揭示了对称折叠通道结构通风吸声的物理机制。首先在理论上分析单个吸声体的通风吸声性能并进行了仿真模拟,在共振频率423 Hz附近,吸声系数大于0.9,通风空间占比高达40%。其次,吸声单体的共振频率可通过改变折叠通道的长度来灵活调控,组合多个不同共振频率的吸声单体可以拓宽吸声体的有效吸声带宽。由4个吸声单体组合的通风吸声体可实现314~366 Hz频率范围内的高效声吸收(吸声系数大于0.8),且通风空间占比达到35%,而结构厚度仅为314 Hz时波长的1/10。该低频通风吸声体具有结构简单、结构强度高和容易制造等特点,在低频通风降噪领域有着潜在的应用前景。

To eliminate or reduce low frequency noise,a low frequency ventilated metamaterial acoustic absorber 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.