Research On Transmission Sound Field Control Based On Acoustic Metasurface

Ultrasound technology is widely used in various fields of social life,such as medical diagnosis and treatment,industrial testing,marine science,military,etc.The sound field control technology that generates a special sound field distribution according to needs is the core of various ultrasound applications.Acoustic metamaterials designed by artificial structures are currently hotspots in the field of sound field regulation and control,and have unique advantages over traditional classical acoustic materials in terms of regulation of sound field distribution.Acoustic metasurface technology can achieve flexible control of ultrasonic waves,and has great prospects in many application fields that require special ultrasonic field distribution.In this thesis,based on the two methods of time inversion and iterative angular spectrum algorithm,a transmissive acoustic metasurface with the ability to adjust the full phase range of the acoustic wave is designed.The specific content includes:(1)Based on the basic ideas of ultrasonic phased array design ideas and time inversion methods,10×10 total acoustic elements with 100 array elements are designed.The delay time on the acoustic metasurface is obtained through finite element simulation,and it is converted into cell thickness data of the acoustic metasurface for modeling.After the inversion of the sound field simulation,the reconstruction of the "S"shaped sound field is achieved at 8 mm from the initial position of the acoustic metasurface.(2)Using an iterative angular spectrum algorithm(IASA),a 20×20 transmission element with a total of 400 elements is designed.The 3 mm plane is defined as the reconstruction plane for regulating the sound field.Through theoretical calculation,the phase distribution data at the acoustic metasurface is obtained after the iterative angular spectrum algorithm iteratively converges.The phase distribution of the acoustic metasurface is converted into the thickness data of the material,and the finite element simulation and theoretical calculation are performed to obtain a reconstructed sound field consistent with the theoretical calculation.(3)Based on the iterative angular spectrum algorithm,a total of 5776 units of 76×76 are designed,and two types of transmissive acoustic metasurfaces with different transmission reconstruction sound fields are designed.Acoustic metasurfaces and acoustic transducers that meet the experimental requirements are fabricated.A reconstructed sound field is obtained at a distance of 25 mm from the acoustic metasurface.By measuring the size of the ideally reconstructed sound field image obtained by theoretical calculation and the size of the image measured by actual experiments,the experimental results of the two transmission reconstructed sound fields have a high consistency with the theoretical calculation.It shows the feasibility of designing transmissive acoustic metasurface based on iterative angular spectrum algorithm.In this thesis,through theoretical calculation,finite element simulation and experimental verification,the sound field control design of the transmission acoustic metasurface is completed.Compared with the traditional ultrasonic phased array,the acoustic metasurface and its design method proposed in this paper have higher degrees of freedom and resolution,and the calculation amount is smaller and the cost is less.