Research And Implementation Of Acoustic Parametric Array Preprocessing Algorithm

Acoustic parametric array can make the sound transmit directionally. Due to thatthe audio signal is loaded in the ultrasonic wave by the use of amplitude modulationtechnique, and then the transducer emits the ultrasonic wave into the air, the originalaudio signal is demodulated by the nonlinear interaction of the air in the disseminationprocess, the ultrasonic has a strong directivity as the carrier.The audio directionalcommunication device is created according to the acoustic parameter array with theclassic berktay equation as a theoretical basis, i.e. the ultrasonic wave is the modulatedsignal of carrier, the audio signal demodulated by the nonlinear interaction of the air isproportional to the second derivative of the original modulation signal envelopesquared, which means that in order to improve the reduction quality of audio andachieve optimal harmonic distortion and amplitude output,the modulation signal mustbe preprocessed.The main contents are as follows:（1）The acoustic parametric array was introduced briefly from the view of thebackground to clear its application significance.（2）The theoretical derivation and solving of “Berktay far field solution”and KZKequation were expanded, double-sideband amplitude modulation algorithm, theroot-mean-square algorithm, and the carrier single sideband preprocessing algorithmwere analyzed theoretically;（3）The formulas of the sound pressure and sound power of the audio signalreproduced after the self-demodulation corresponding to each algorithm were derivedfrom the input signals of single-frequency and complex frequency, the types ofdistortion and the factors influencing the sound pressure of demodulated signal wereanalyzed at the same time.（4）The simulation results of different algorithms were analyzed by establishing acustom demodulation model for simulation, the frequency of the audible signal in thelow frequency range. It was drawn in the previous theoretical analysis thatintermodulation distortion frequencies generated by preprocessing algorithm were in thesame range when the complex frequency was input signal, which had a greater impacton restore audio signal impact. In order to distinguish the two cases better and obtainmore effective audio signal output, a new preprocessing method was proposed. It increase the distinctions between the two cases in order to reduce the impacts on thewhole system maked by intermodulation distortion of preprocessing method. It providessome theoretical reference value for preprocessing system of acoustic parametric arraysignal.（5） Previously most people achieve preprocessing algorithm of acousticparametric array by using DSP digital signal platform. In this paper, the FPGA waschosen as the hardware platform for the implementation taking into account itsparallelism as well as other advantages. The new algorithm proposed in this paper isstill in theory research level, the effect of its implementation needs to be further verified,so in the end more than three preprocessing algorithm using FPGA method. Therefore,the three preprocessing algorithm use the FPGA method,which implemented by the useof the Verilog language programming in the ISE software environment.