Acoustic Emission Control And Acoustic Field Characteristics Of Underwater Acoustic Parametric Array

Parametric array is an acoustic emission device that generates low-frequency differential wave under the nonlinear action of transmitting two high-frequency sound waves.It has the advantages of pointed edge,no side lobe,high spatial resolution,strong penetrability,and long propagation distance,etc.However,it has not been used in underwater acoustic countermeasure at present,one of the reasons is that the secondary wave shape generated by parametric array cannot be controlled.In addition,the conversion rate of parametric array is low and the accumulative distance is long.According to the above problem,based on the theory of Westervelt,Bertay far field solution is derived,KZK equation,and based on this theory basis,set the transmitting signal waveform,choosing the right makes the signal modulation algorithm in nonlinear generated two columns under the action of the demodulation independently controllable low frequency signal,and by changing the parameters of launch in time domain and frequency domain to control the difference frequency signal.In this paper,the specific influence of frequency downshifting ratio on the directivity of parametric array is analyzed and the original wave frequency and difference frequency of transmitting signal are set on this basis.In this paper,the output power of parametric array is improved by building rectangular array,and the effect of array spacing on performance is discussed.In this paper,the acoustic propagation characteristics of water containing bubbles are analyzed,and the influence of bubble resonance on the directivity and effective array length of the parametric array is discussed,and the primary and differential frequency of the parametric array is set as a limiting factor.On the basis of theory and simulation analysis,the independent controllability of the low-frequency signal of the parametric array is verified through experiments,and the control of the low-frequency signal by the transmission parameters is verified.First,verify the phase controllability in the time domain,then verify the low-frequency signal amplitude controllability in the frequency domain,and finally verify the spatial characteristics of the parametric array in the space domain to provide index parameters for the transmitted signal parameters.