薄膜底面Helmholtz腔声学超材料的隔声性能  

Sound insulation performance of Helmholtz cavity with thin film bottom

作　　者：贺子厚 赵静波[2] 姚宏[2] 陈鑫[1] He Zi-Hou;Zhao Jing-Bo;Yao Hong;Chen Xin(Graduate School,Air Force Engineering University,Xi’an 710051,China;Department of Basic,Air Force Engineering University,Xi’an 710051,China)

机构地区：[1]空军工程大学研究生院,西安710051 [2]空军工程大学基础部,西安710051

出　　处：《物理学报》2019年第21期142-153,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11504429);空军工程大学基础部预研项目(批准号:YNJC119070602)资助的课题~~

摘　　要：针对低频噪声的隔离问题,设计了一种薄膜底面Helmholtz腔声学超材料,该超材料由薄膜底面Helmholtz腔附加质量单元构成.使用有限元法,计算了超材料在20-1200 Hz频段内的传输损失曲线与各阶共振频率,并在实验中验证了数值计算的真实性.研究结果表明,超材料在20-1200 Hz频段内隔声性能良好,出现了6个隔声峰,其中100 Hz以下的2个隔声峰传输损失分别高达44.29 dB与67.43 dB,整个频段内的最高传递损失为90.18 dB.相较于单一的Helmholtz腔、薄膜声学超材料或传统材料,本超材料的隔声性能有了较大提升.结合共振频率与隔声峰处的振动模式图,进一步分析了超材料的隔声机理.计算了超材料的透射系数与反射系数,使用等效参数提取法,得到了超材料的等效模量与等效密度,在隔声峰处发现了负等效密度,同时发现其等效模量接近于零,并由能量角度进一步分析了异常等效参数的产生机理.通过等效电路法,得到了超材料的声阻抗,较精确地计算了超材料的首阶共振频率,并分析了产生误差的原因.研究了附加偏心质量单元对超材料隔声性能的影响,发现附加偏心质量单元可以抑制反对称共振模态的出现,同时大大增加了超材料的隔声峰数量,在实验中这一说法得以验证.Aiming at the isolation of low-frequency noise,an acoustic metamaterial is designed based on Helmholtzcavity and thin film structure.It consists of a Helmholtz cavity with film bottom and the mass block attachedto the cavity.By the finite element method,the transmission losses and resonance frequencies of metamaterialsin a frequency range of 20-1200 Hz are calculated and also verified experimentally.The results show that themetamaterial has great sound insulation performance in the frequency range.There are six sound insulationpeaks,of which the two sound insulation peaks below 100 Hz have the transmission losses of 44.29 dB and67.43 dB,respectively.The maximum transmission loss in the whole frequency range is 90.18 dB.Comparingwith the normal Helmholtz cavity or thin film acoustic metamaterial or traditional material,the soundinsulation performance of the metamaterial is improved greatly.By analyzing the resonance and vibration modediagram at the sound insulation peaks comprehensively,the sound insulation mechanism of the metamaterial isfurther explored.The results show that many resonance modes have no effect on transmission loss only whenthe resonance mode can be coupled with the incident wave and is not an antisymmetric mode which can affectthe transmission loss.The transmission and reflection coefficient of the metamaterial are calculated by the finiteelement method,and through the method for retrieving effective properties,the effective mass density andeffective modulus are obtained.It is found that there is a negative effective mass density at the sound insulationpeak,meanwhile the effective modulus is close to zero.The generation mechanism of abnormal equivalentparameters is analyzed from the energy view point.The acoustic impedance of the metamaterial is obtained byan equivalent circuit method,through which the first resonance frequency is calculated relatively accurately.According to the results of the previous study on sound insulation mechanism,the effect of the eccentric massunit on the sound insulat

关 键 词：Helmholtz腔 薄膜声学超材料 有限元法 隔声性能 负参数 

分 类 号：TB535.1[理学—物理]