Research On Acoustic Directional Technology Based On Acoustic Parametric Array

Voice pollution not only makes people upset and sleep badly,but also causes heart disease.The acoustic directional system based on the acoustic parametric array can make the sound wave have directionality just like the laser,modulate the sound signal which needs to be transmitted with the ultrasonic carrier signal,and the modulated signal can self extract the low-frequency audible sound signal with high directivity in the air medium,so as to provide a relatively independent and quiet environment for people.Based on the theory of acoustic parametric array,this paper analyzes the key technologies of the acoustic directional system,such as the difference frequency sound field model,preprocessing algorithm,transducer design and prototype software and hardware design,and demonstrates the performance parameters of the system by using the built test platform,which has certain theoretical reference value and practical significance for the further application of the acoustic directional system.Firstly,the hardware and software platform of audio directional system is designed.In the aspect of hardware,the circuit schematic diagram and PCB design of signal processing module,transducer array module and sound intensity detection module are completed.Different from most audio directional systems using FPGA and DSP,stm32f405 microcontroller is selected as the signal processing module on the premise of satisfying the system use.Stm32f405 has the advantages of low cost,low power consumption and convenient function expansion.In addition,based on the interface development software QT,the sound intensity detection system of audio directional system is designed to provide a friendly human-computer interface.It provides the software and hardware foundation for the realization of audio directional system.Secondly,according to Helmholtz’s nonlinear acoustic theory,the parametric acoustic array theory is derived,and the theoretical model of the difference frequency sound field is established,and the influencing factors of the directivity of the difference frequency sound field are obtained through computer simulation.The difference between the difference frequency method and the conventional method is analyzed.It is concluded that the directivity of the sound field can be improved and the side lobe can be effectively suppressed by using the difference frequency method,Increasing the frequency of difference frequency and reducing the frequency of fundamental wave can effectively improve the directivity of difference frequency sound field.Then according to the theory of acoustic parametric array self demodulation,three signal preprocessing algorithms,DSB,sqrt and SSB,are studied from the two cases of single frequency input and wide frequency input,and the signal preprocessing algorithm suitable for this system is summarized.It provides a theoretical basis and model for the self demodulated audible sound with high power and low distortion.Then,aiming at the directivity of the transmitting array of the audio frequency directional system,based on the uniform array,this paper proposes the optimization model of the ultrasonic sparse array based on the improved genetic algorithm,constructs the two factor fitness function of the main beam width and the side beam gain,and deduces the directivity function of the transducer array.It is found that the optimized ultrasonic array can use fewer array elements than the uniform array,which can effectively control the cost of the whole system and provide the basis for the design of high directivity transducer array.Finally,a prototype of the audio directional system based on the acoustic parametric array is built,and the performance of the system,such as the directional sound transmission performance and the sound pressure intensity,is tested by using the experimental platform.It is concluded that the audio directional system designed in this paper can produce directional sound,and has relatively good sound field directivity.