Research On Measurement Methods Of Radiated Noise In Shallow Water Environment

Underwater vehicle is a common exploration and reconnaissance equipment for underwater military confrontation.Acoustic stealth performance is one of its important evaluation indexes.Good acoustic stealth performance can improve the survivability and deterrence of underwater vehicle in battle.Accurate measurement of radiated noise of underwater vehicle can provide reliable data support for improving acoustic stealth performance.In the process of measuring the radiated noise of underwater vehicle,the ocean waveguide and the measurement method are the main factors affecting the measurement results.The radiated noise results measured by different methods under different waveguide conditions will be different,which leads to the inconsistency between the measured results and the actual radiated sound source level of underwater vehicle.Therefore,the radiation noise measurement work needs to choose a reasonable measurement method according to different measurement conditions,in order to have a more accurate identification of the radiation noise of underwater vehicles.The sea around our country is shallow,so it is of great significance to study the method of radiative noise measurement in the shallow sea environment.In this paper,the shallow sea waveguide is modeled,the underwater sound field is established by using the ray model,the different waveguide conditions are changed,and the acoustic propagation characteristics of the sound field are analyzed from the aspects of propagation loss and energy distribution.On this basis,the vertical acoustic pressure hydrophone array is adopted,and two radiation noise measurement methods including constant beam width beamforming and virtual time reversal mirror are studied to measure the radiation noise source level of underwater vehicle.Combined with simulation,the influence of seawater depth,sound source depth,receiving position,sound velocity gradient and other factors on the measurement results of the two methods in shallow sea environment was quantitatively studied,and the applicability of the two methods under different conditions was analyzed.Through the study of this paper,it is found that the two methods can achieve the measurement of underwater vehicle radiation noise,but the constant beam width beamforming method has higher requirements for the design of the array,and the array aperture is larger.The use of virtual time reversal mirror does not have high requirements for array design,but when the location of the sound source is mismatched in the measurement of radiation noise,the measurement performance will be significantly decreased.To solve this problem,an improved method is proposed in this paper.The time reversal mirror is used to combine the location of the sound source with the measurement of the radiation noise,so as to reduce the impact of the measurement results of the location mismatch of the sound source.Finally,the method is verified by experimental data.