Design Of Low Frequency Acoustic Directional System Based On Acoustic Parameter Array

Because the low frequency acoustic directional system has the characteristics of low depth of frequency diving,high pointing performance,and can control the low frequency acoustic wave propagation in narrow channel space with the help of small volume equipment,it has a wide application prospect in directional infrasonic wave generation,underwater communication,rehabilitation and other aspects.The modulated acoustic wave emitted by the acoustic parameter array can be demodulated by the nonlinear action and has a good directional property.At present,there are many assumptions in the theoretical derivation of acoustic parametric array.The self-demodulation process is simply explained as nonlinear disturbance and rapid attenuation of high-frequency carrier,which lacks detailed analysis.There is blindness in the design of low-frequency acoustic directional system based on acoustic parametric array.In addition,the directivity of acoustic parameter array is mainly determined by geometric relation,and the effects of electroacoustic coupling and transmission medium on acoustic radiation characteristics are not considered.To solve these problems,the acoustic selfdemodulation and array directivity research are carried out in this paper,and a directional low frequency acoustic verification system based on acoustic parameter array is designed.First of all,are analyzed in this paper,the acoustic parametric array model,nonlinear model is derived based on analysis of the high frequency has nonlinear wave modulation demodulation principle,the simulation analysis of the four kinds of modulation mode since the demodulation effect,was proposed based on the nonlinear acoustic signal detection model since the demodulation process of analogy analysis method,using nonlinear acoustic analogy signal detection model since the demodulation process,The simulation results show that the product detection model has a high similarity with the self-demodulation process law of nonlinear acoustic waves.Square root(SQR)modulation and full carrier(SSB)modulation have the best correlation with the self-demodulation results.SQR modulation helps to improve demodulation efficiency(Kd)and full carrier SSB modulation helps to reduce reduced harmonic distortion(THD)values.The analogy method presented in this paper provides a technical support for the simulation design of low frequency acoustic directional system based on nonlinear sound.Secondly,in view of the array directivity of acoustic field in the study of influencing factors to consider the problem of insufficient,this article USES electric-more than physical field coupling method,typical of different shapes of arrays,and by their different shapes of array and array intensity on the radiation acoustic field directivity,main lobe beam width and to the gate,sidelobe suppression ability and so on has carried on the simulation research,The simulation results show that the hexagonal array has better directivity than the quadrilateral array under the same effective radiation area,and the hexagonal array composed of circular array elements has the best directivity.Dense array structure can improve the directivity of sound field.Finally,based on the above simulation research,a directional low frequency acoustic wave verification system is built,including a low frequency acoustic wave generation system composed of a hexagonal parametric array and a low frequency acoustic wave verification system composed of signal receiving,signal acquisition,analysis and processing modules.Variational Mode Decomposition(VMD)method was used to analyze the modal structure of the generated low frequency acoustic wave.Using the effective mode function(IMF)whose main frequency is the modulation frequency,the effects of nonlinear acoustic self-demodulation and array directivity on the self-demodulation efficiency,total harmonic distortion and directivity are analyzed.The experimental results show that the nonlinear acoustic selfdemodulation and array directivity are consistent with the theoretical results.This study can provide reference for the design of modulation algorithm in acoustic parametric array,the design of electro-acoustic transducer array and the generation of ultra-low frequency acoustic waves such as infrasound.