Research On Field Calibration Method Of Sensitivity Of Hydroacoustic Line Array

Hydroacoustic line arrays have an indispensable role in the acquisition of marine information and other aspects.During the development and use of line arrays,their sensitivity and other electroacoustic parameters need to be measured and calibrated,so the in-situ measurement and calibration of underwater fixed line arrays is a problem worthy of in-depth study.In order to effectively measure and calibrate the sensitivity of a fixed line array element in a submarine muddy environment.First,this paper proposes a sensitivity calibration method in a tube based on the correction of reciprocal constants.Second,based on the theoretical study,the software is used to simulate the sound field parameter equations in the tube for the sediment field environment to obtain the values of the reciprocal constants in the sediment tube at different frequencies.Last,experiments are built to verify the results of the theory and simulation to obtain the sensitivity before and after the correction.The experiments show that the corrected reciprocity constants are much closer to the sensitivity values measured by the freefield comparison method than the uncorrected sensitivity values after substitution.In the frequency range of 0.5-4 k Hz,the maximum undulation of the corrected reciprocal transducer sensitivity curve is 1.41 d B with an error of less than 2 d B,which meets the acoustic metrology requirements in this specific measurement environment and verifies the accuracy and validity of the method.The effect of different boundary conditions on the calibration accuracy and the effect of varying in-tube parameters such as transducer spacing on the calibration of sensitivity values are analysed.Based on the theory and validation of the calibration method,a line array field calibration system is developed,including acoustic emission,signal acquisition and software control components.The software controls the hardware system to switch and match the 48 elements of the line array as well as automatic and manual measurements.The array elements in the array can be grouped arbitrarily,automatically switch measurements and display the results in real time,etc.The purpose of using the system for the field calibration of long line arrays underwater is achieved.The sensitivity of the array elements under each frequency band in the experiment is obtained by combining measurements and compensation values,In this case,the linear array hydrophone measured a sensitivity of less than 1 d B at the 1 k Hz operating frequency point compared to the manual measurement,verifying the accuracy of the system and method.Finally,the experimental measurements are analysed and an uncertainty evaluation is carried out.