The Reasearch Of Measurement Methods About Ship Radiated Noise Based On Cylindrical Array

The accurate measurement and analysis of ship radiated noise is not only a necessary condition for the effective identification of underwater targets,but it's also an important guarantee to improve the technology of ship vibration attenuation and noise reduction.With the development of noise reduction technology,the traditional single hydrophone method can not meet the requirements of high precision measurement of weak noise,and it will be much value to utilize three-dimensional array for detecting underwater signals.Underwater target noise measurement methods based on cylindrical array is studied in this paper,which is on the basis of predecessors' research findings.It includes performance research and simulation of multiple types of beamforming algorithms,comparison of noise measurement effect between single hydrophone and the array as well as the conclusion verification with lake test signal data.In this paper,the development status of underwater noise measuring technique is summarized firstly.It concentrates on the performance of wideband time-delay beamforming and MVDR beamforming algorithms,along with the effect of target noise measurement which these two algorithms are applied in.According to the simulation results,more advantages of array gain can be acquired with middle or high frequency signal incidence.Besides,its index of beamwidth and sidelobe can be stable at these situations.In the case of applying diagonal loading technique to MVDR algorithm,we mainly study the appropriate value of loading capacity.As for sound source intensity estimation,the fluctuation of target sound source level solved by the beamforming output signal is much less than single element result,and this superiority will become more obvious along with the increased signal frequency.However,this advantage will be weakened when the noise is measured at a long distance,which is to say,the cylindrical array discussed in the paper is more suitable for close range noise measurement.In addition,a hardware design approach of time mark aided underwater ranging is presented,and it can achieve good operating results in the field test conditions.Through the performance test,the underwater timekeeping module can stably output the timestamp data that is less than 1us deviation,which plays a key role in the accurate determination of underwater signal transmitting distance and target sound source level.In order to verify the correctness of measurement methods,the lake test is conducted and experimental data is analysed in detail.Among them,the relationship between sound source level and distance that is concluded from analysis of individual components in multi-tune signals can concide with the simulation results very well.This inspects validity and feasibility of the array signal processing methods.