Research On The Detection Of Weak Acoustic Signal Based On Phononic Crystals With Line-defect Structure

The detection of weak acoustic signal is closely related to modern production and life.It has important practical application value in new cross-cutting fields,such as mechanical production,environmental testing,military reconnaissance,biotechnology,early diagnosis of diseases,and health monitoring.The phononic crystals with line-defect structure have unique band gap characteristics and excellent transmission characteristics,and it can effectively achieve the enhancement of the weak acoustic signal.The unique acoustic performance of phononic crystals with line-defect structure provides a new way for the detection of the weak acoustic signal.Based on the band gap theory of phononic crystals and finite element theory,we designed a phononic crystals composed of slit acrylic tube embedded in an air background matrix,and constructed the line-defect structure by changing the slit direction of the acrylic tube.Phononic crystals with line-defect structure have special acoustic properties.We propose a weak acoustic signal detection method based on phononic crystals with line defect structure.The feasibility of detecting weak acoustic signal based on phononic crystals with line-defect structure is verified by finite element simulation and experiment.The main research work of this thesis is as follows:(1)Design and analysis of phononic crystals with line-defect structureWe designed a phononic crystals composed of slit acrylic tube embedded in an air background matrix,and constructed the line-defect structure by changing the slit direction of the acrylic tube.The band structure and transmission characteristics of the phononic crystals with line-defect structure are calculated.The maximum enhancement factor of the acoustic signal enhanced by the phononic crystal with line-defect structure is calculated.The influence of structural parameters on the acoustic signal enhancement performance of phononic crystal s with line-defect structure is discussed.(2)Simulation of weak acoustic signal detection based on phononic crystals with line-defect structureThe method for the detection of weak acoustic signal based on phononic crystals with line-defect structure is proposed,and a simulation model is established in COMSOL.Based on the phononic crystals with line-defect structure,the detection of weak harmonic signal and periodic impulse signal are simulated and calculated.The simulation results show that the phononic crystals with line-defect structure can successfully detect the weak harmonic signal and periodic impulse signal,which proves the feasibility of detecting weak acoustic signals based on phononic crystals with the line-defect structure.(3)Experiment verification of weak acoustic signal detection based on phononic crystals with line-defect structureThe weak acoustic signal detection method is experimentally verified based on the phononic crystals with line-defect structure.An acoustic testing experiment platform is established,and the sample of phononic crystals with line-defect structure is produced.By set different signal-to-noise ratios,weak harmonic signal and periodic impulse signal is detected,separately.The experimental results show that the phononic crystals with line-defect structure successfully detected weak harmonic signal and periodic impulse signal under heavy noise background.The experimental results verify the effectiveness of the method for detecting weak acoustic signal based on phononic crystals with line-defect structure.The phononic crystals with line-defect structure designed in this thesis have good acoustic enhancement performance,which can effectively reduce noise and achieve the enhancement of the weak acoustic signal.The simulation and experimental results show that,by using phononic crystals with line-defect structure,weak harmonic signals and periodic impact signals under heavy noise background can be detected successfully.Therefore,this research provides a new idea for solving the problem of weak acoustic signal detection,and it provides a reference for the design of new-type filters,sound energy absorbers and other high-performance acoustic devices.And it further expands the scope of application of phononic crystals.