Research On Acoustic Band Gap Control Based On One Dimensional Phononic Crystal

As a common energy carrier,sound wave is widely used in various detection fields,such as sonar detection of underwater objects,ultrasonic detection of structural damage and medical ultrasound imaging of human tissue.In different detection environments,the influence of complex background noise and vibration of the system will lead to the low signal-to-noise ratio of the received signal.In this paper,the band gap characteristics of phononic crystals are used to realize selective transmission of sound waves,so as to achieve the purpose of reducing noise and improving the signal-to-noise ratio.However,the performance of band gap regulation of traditional phononic crystals depends on the geometric parameters of the structure,which makes the regulation of sound waves limited to the structure itself,which leads to the limitation of the regulation ability of the forbidden band.In this paper,we design and study the tunable phononic crystals structure for underwater and solid detection environments to meet the wide-frequency regulation requirements of sound waves in different environments.One dimensional solid-fluid phononic crystals will be able to adjust the underwater acoustic band gap in real time by using the characteristics that the width of fluid layer can be adjusted by the change of the space between solid layers.The real-time adjustment of the band gap of bending wave in beam structure is realized by introducing piezoelectric elements into the substrate,combining phononic crystals and piezoelectric shunt technology.In the case of the matrix structure unchanged,only the parameters of the inductance and resistance elements need to be changed to realize any change of the band gap in the structure.The two methods can make the structure reusable,the band gap control is simple and feasible and real-time adjustable.According to different requirements of detection environment,this paper studies the regulation of band gap of one-dimensional phononic crystals by combining theory,simulation and experiment.The main contents and results are as follows:1.Sound transmission theory of one-dimensional phononic crystals.Based on the transfer matrix method,the transmission and band structure theory of sound wave propagation in one-dimensional solid-fluid phononic crystals are studied.Combined with the electromechanical coupling effect,the transmission characteristics of acoustic wave in one-dimensional piezoelectric shunt phononic crystals beam with external shunt circuit are analyzed.2.The sound transmission characteristics of one-dimensional gradient solid-fluid phononic crystals.In view of the application demand of real-time regulation of underwater acoustic transmission,the band gap characteristics of one-dimensional solid-fluid phononic crystals are studied.Compared with the periodic solid-fluid phononic crystals,the structure has a controllable widening band gap,which can capture rainbow and energy localization for underwater acoustic wave with wide frequency incidence.It provides a new design idea for underwater acoustic devices,such as acoustic filter,acoustic sensor and frequency divider.3.Band gap characteristics of one-dimensional piezoelectric phononic crystals beam.The theoretical model of one-dimensional piezoelectric phononic crystals beam is established by using the transfer matrix method.The acoustic transmission characteristics of the beam are numerically simulated by the finite element method,and further verified by experiments.The results show that the results obtained by the three methods are basically consistent.4.The study on the band gap characteristics and its regulation of one-dimensional piezoelectric split phononic crystals beam.On the basis of one-dimensional piezoelectric beam,RL shunt circuit and negative capacitance circuit are introduced to form one-dimensional piezoelectric split beam.Compared with the periodic distribution of RL shunt circuit,it is pointed out that in addition to the original Bragg scattering band gap,there are also a wide range of local resonance band gaps with the gradient and random distribution of the circuit.This provides a new method for the low frequency and wide band bending wave regulation.For the periodic negative capacitance piezoelectric shunt phononic crystal beam,combined with the point defect characteristics in the aperiodic phononic crystals,the energy localization of different bending waves can be realized and the signal-to-noise ratio of the output signal can be improved.The research work of this paper aims at different detection environments,and realizes the wide band gap adjustment of phononic crystals,which provides theoretical support for the vibration reduction and noise reduction of the detection equipment,the filtering of the received signal and the improvement of the signal-to-noise ratio of the received signal.