Magnetorheologically Coupled Active Acoustic Metamaterials Based On Magnetorheological Membrane And Their Low-Frequency Sound Insulation Properties

Low-frequency noise has the characteristics of longer wavelength and less attenuation.Controlling the propagation of low-frequency noise has always been one of research hotspots and difficulties in the field of acoustics.Acoustic metamaterial is a periodic composite material with negative equivalent characteristics in the low frequency range.Its structural size is two to three orders of magnitude lower than the low frequency wavelength,so it has broad application prospects in the field of low frequency noise control.In this paper,an active acoustic metamaterial structure based on magnetorheological thin membranes is studied.An electromagnetic field radial loading device is designed and prepared to adjust its acoustic properties,and is analyzed by theoretical analysis,software simulation,and experimental measurement.The acoustic properties under radial magnetic fields were studied.The main research content is as follows:1.An active acoustic metamaterial structure based on magnetorheological thin membrane was designed.It was composed of aluminum ring frame and magneto-rheological thin membrane with additional mass.It is based on local resonance mechanism and magnetorheological theory.The theoretical calculation model of active acoustical metamaterials was established,and the geometrical model of the active acoustical metamaterial was further established.Through the finite element simulation of the model,the regulation law of the acoustic field performance of active acoustical metamaterials by radial magnetic fields was analyzed.It shows that the radial magnetic field excitation can actively control the sound insulation properties of metamaterials and increase the sound insulation bandwidth of acoustic metamaterials.2.The influence of geometrical parameters change on the acoustic insulation properties of active acoustical metamaterials was studied.The change rule of the acoustic insulation material under active acoustical metamaterials under the same radial magnetic field is analyzed.Firstly,the change law of the first peak value of the sound insulation curve corresponds to the frequency value;second,the first sound insulation peak value of the sound insulation curve corresponds to the size of the sound insulation.The law of change.The results show that the advantage of the four mass arrangement structure is that the radial magnetic field can adjust the sound insulationbandwidth,and the advantage of the single mass block structure is that it has a higher sound insulation peak;the increase in the additional mass can make the sound insulation peak frequency Move toward low frequencies without reducing the adjustable sound insulation bandwidth.3.The effects of material parameters and changes in membrane pre-stress on the acoustic performance of active acoustical metamaterials were studied.The variation law of the sound insulation curve in the low frequency range was studied,and the influence of material parameters and membrane prestress on the sound insulation of the metamaterial was analyzed.The results show that increasing the volume fraction of ferromagnetic particles in magneto-rheological materials can effectively improve the controllability of acoustic metamaterials and increase the sound insulation bandwidth;reducing the prestress can make the peak frequency of sound insulation shift to a low frequency and will not decrease.Adjust the sound insulation bandwidth.4.An experimental platform was set up to test and study the acoustic properties of active acoustic metamaterials.Radial electromagnetic field loading devices and active acoustical metamaterial specimens were designed and prepared.The impedance tube measurement system was used and the four-sensor measurement method was used to stimulate different magnetic fields.The acoustic insulation of the active acoustic metamaterial structure is measured.Comparing experimental data with software simulation data,the results show that under the action of radial electromagnetic field,the active acoustic metamaterial designed in this paper can achieve active adjustment of acoustic performance.