Research On The Sound Insulation Properties Of Acoustic Metamaterials With Piezoelectric Shunts

Noiseless quality is an important goal and character in the development of current equipment.Noise has a serious effect on the health of passengers and the performance of equipments.Noise suppression has become one of the key technical problems that need to be solved urgently when Chinese equipment manufacturing industry compete in the international market.Lightweight plates are the major component of equipment's cabin.The sound insulation performance of which is an important index to estimate the level of noise suppression.With the obvious characteristics such as large energy,far propagation distances,line spectrum and so on,low-frequency noise is often the most serious impact on the noise quality of equipment.Due to the mass law,the traditional sound insulation technology usually only plays an important role in the high-frequency noise reduction.In order to suppress the low frequency noise,the mass should be markedly increased.Hence,insulating low-frequency sound is always a conventional challenge.In the past decade,acoustic metamaterials,which are generally considered to be a kind of artificial composites containing micro resonant units,have been shown to exhibit properties such as unusual material properties.The concept of acoustic metamaterials provides new means for low-frequency sound insulation.Recently,some investigates show that using smart structrues and active components can enrich the design of acoustic metamaterials.In particularly,acoustic metamaterials with piezoelectric shunting resonators have obvious advantages in low-frequency sound insulation,due to the strongpoints including tunable local resonance frequency,small additional mass,and no damage to the host structure.This dissertation is aimed at solving some key theoretical and technical problems to promote the applications of piezoelectric shunting type metamaterials technology in engineering to suppress noise.The plate-shaped acoustic metamaterial and foil-shaped acoustic metamaterial are analyzed.The main contributions and innovations of this dissertation are given as follows:1.The calculation methods for sound insulation properties of acoustic metamaterials are studied.Based on the dynamic effective theory,a new method called effective medium method is proposed to calculate the sound insulation performance of plate-shaped acoustic metamaterial.The mainly advantages of this method are extremely efficient and accurate.According to the finite element theory,a multi-physics dynamic coupled finite element model of foil-shaped metamaterial is developed.The finite element method can be used to analysis complex metamaterials with all kinds of boundary conditions.Above methods provide powerful tools for theoretical analyses about plate-shaped acoustic metamaterial and foil-shaped acoustic metamaterial.2.The sound insulation properties of plate-shaped acoustic metamaterial are analyzed in-depth.It is found that in some frequency region,plate-shaped acoustic metamaterial can obtain better sound insulation performance than traditional homogeneous plates with the same mass.It is also shown that metamaterial-based plate has unusual effective stiffness.And the sound insulation peak arises as a result of infinity effective stiffness,while the sound insulation dips appear due to the coincidence between the flexural wave number of plate-shaped acoustic metamaterial and the trace wavenumber of incident sound wave.3.The sound insulation properties of foil-shaped acoustic metamaterial are analyzed in-depth.Results show that the sound insulation performance of foil-shaped acoustic metamaterial is better than that limited by mass law.The sound insulation mechanisms of foil-shaped acoustic metamaterial are revealed.It is also found that foil-shaped metamaterial has extraordinary effective mass density.The location of the sound insulation peak corresponds to the frequency at which the effective mass density is infinity,while that of sound insulation dips match well with the frequencies where effective mass density is zero.4.The manipulation and some broadening methods of sound insulation for plate-shaped acoustic metamaterial and foil-shaped acoustic metamaterial are studied.In detail,the effects of incident angle,structural properties and electric properties are investigated.It is also found that the negative capacitance circuits,multi-mode circuits and multi kinds of cells can make the sound insulation performance better.These works can provide some important basis for the application of acoustic metamaterials with piezoelectric shunts.In summary,motivated by the demands of noise suppression in equipment's cabin,this dissertation applies acoustic metamaterials with piezoelectric shunts to sound insulation in order to find a light way to isolate the low-frequency noise.The modeling methods,sound insulation performances,mechanisms,manipulations and sound insulation properties broadening methods of plate-shaped acoustic metamaterial and foil-shaped metamaterial are studied.The results of this dissertation not only provide new means and theoretical support for low-frequency sound insulation,but also have important significance to promote the application of metamaterial technology.