Research On Nonlinear Sound Field Detection Technology Of Focused Ultrasound

In recent years,there was an obviously improvement of the focused ultrasound technology in the ultrasound sector and the medical community,the study of the concentrated sound field has become a hot spot.Focused sound field produce high-intensity sound field,and the non-linear effects could not be ignored,thus it is difficult to measure the parameters of the sound field,the numerical methods is a common way to evaluate the performance of focused sound field.Therefore,since the non-liner problem,the assessment focus on the non-liner features of the focused sound field,and build a detection platform.The project detect accuracy the harmonic components and distribution of the focused sound field.The blew is the working:(1)Introduced the background and the propose of the project,summarize the status of non-linear acoustics and the existing methods of underwater sound field measurement.(2)Introduced the basic theories of linear acoustics and nonlinear acoustics,The KZK equation is deduced by the Westervelt equation through introducing the paraxial approximation,and simulation of the non-linear radiation field of circular focusing transducer.(3)Providing a new harmonic detection method based on Empirical Mode Decomposition(EMD).Otherwise,through this method to reduce noise of high frequency for non-liner sound field signal.(4)Build a non-liner sound field measurement system,design the software modules of the sound field measurement system,which including sound field measurement program and stepping motor control program.Meanwhile,in this chapter,it provides the functions of the system motion control,data acquisition,signal analysis,sound field visualization,the automatic measurement of production is realized by mixed programming of LabVIEW and MATLAB.(5)Experimental study of circular focusing transducer,certify the accuracy of using EMD to determine the non-liner sound field signal.In this chapter,it analyze the far field sound pressure distribution of the focused nonlinear sound field by the near-field measurement surface,evaluate the prediction error.(6)Conclusion and future outlook.