阻抗管中多自由度波导抑振器的声辐射

多自由度波导抑振器通过自身的运动来抑制弹性基板中弯曲波的传播,但其自身的运动也将引起声波向周围介质辐射。为了定性研究其声辐射性能,在物理建模时,将波导抑振器视为由一个单极子共振器(类似于Helmholtz共振器)和一个偶极子共振器复合而成的结构。单极子共振器通过一根弹性细杆连接在弹性基板上。在外界振动的激励下,单极子共振器产生一个振荡的体积速度,偶极子共振器产生一个振动的偶极子弯矩。它们都将在介质中引起相应的声辐射。由于该模型具有损耗阻尼,因而可以耗散部分振动能量。同时,在单极子共振器的共振频率处,受激振动声辐射将出现峰值,而在偶极子共振器的共振频率处,由于受弯矩阻抗特性的影响,该频段的受激振动声辐射将产生一个阶跃。水声阻抗管中的试验研究证实了这一结果。

Sound Radiation of MDOF Waveguide Vibration Depressor in Impedance Tube

Although the MDOF waveguide vibration depressor can depress the flexural wave propagating in basement shell or plate,its vibration also induces sound radiation in surrounding fluid.In order to investigate the sound radiation characteristic of MDOF waveguide vibration depressor,it may be modeled as the structure combined by a monopole resonator(a Helmholtz resonator) with a dipole resonator.The monopole resonator is attached to the basement shell through a flexibility rod.Under the stimulation of vibration,the monopole resonator will generate volume velocity oscillation,while the dipole resonator will generate vibration moment,all those will result in sound radiation in surrounding media.The further study on MDOF waveguide vibration depressor indicates that,in the existence of damping friction in waveguide vibration depressor,all those movements will cause energy dissipation.In addition,a peak will appear in the radiated sound spectrum when the frequency coincides with the eigenfrequency of the monopole resonator,moreover,a step jump will occur in the eigenfrequency of dipole resonator due to the influence of moment resistance characteristic.The acoustical experiment performed by authors in the water acoustical impedance tube has testified the analyzed result based upon the related theory.