Numerical Simulation And Experimental Research On The Approach Of Sound Focus In The Air Using Wave-guide Acoustic Lens

Acoustic lens is one of the structures which refract and focus sound waves by redistributing medium property or introduce phase shift.The principle and design method of the obstacle and waveguide type lens are presented in this thesis. Numerical model which reveals the propagation of high intensity sound waves in the lens was developed based on the finite element method and the ideal linear or nonlinear acoustic equations. The validity of the model is demonstrated by the comparison between the theoretical and numerical results. With the support of this tool, characteristics of the focus sound field are studied and the influence of structure and source parameters is analyzed. The application of the lens to focus sound in the air is proved to be feasible.The 3D wave-guide lens was designed and manufactured. The working frequency band and focus sound field were analyzed. The lens was coupled with a loudspeaker array with the frequency around 1kHz. Test data in the horizontal, vertical and parallel planes were obtained based on the linear array scan method.Research has shown that the focus gain increases with the deflection angle except for the too large value. The lens is feasible in beam width reduction when the deflection angle is small and the focal length is large. When the diameter of the lens is fixed, the focus gain increases with the sound frequency. Experimental results show that the gain value of 3-5dB could be obtain for the loudspeaker array in 1kHz and most of the sound energy is concentrated near the axis.All of the simulation and test results have proved that the wave-guide acoustic lens has succeeded in the focus effect.