Research On Measurement Method Of Acoustic Parameters Of Transducer Under High Hydrostatic Pressure

Deep sea transducer is an indispensable device in ocean exploration.In order to accurately understand the changes of acoustic parameters of the transducer in the deep sea,domestic and foreign countries have carried out research on the calibration of the acoustic performance of the transducer under high hydrostatic pressure.However,due to the limitation of measuring equipment and methods in China,the calibration pressure range is only within 10 MPa.A small-scale calibration system under high-hydrostatic pressure is established in this paper,focusing on the change of the impedance characteristics and sensitivity of the transducer under the hydrostatic pressure of 0 ? 40 MPa.To solve the problem that acoustic parameters of the transducer cannot be measured accurately by using continuous wave in small size cavity,a transducer parameters measurement method based on pulse sine signal excitation under high hydrostatic pressure is proposed.A high pressure device with a cavity size of 250 ×500mm and a working pressure of 0 ? 40 MPa was set up as the measuring equipment,and a corresponding automatic measurement program was designed.For the measurement of the impedance characteristics of the transducer,a measurement system for atmospheric pressure and high pressure was established respectively.Sine pulse wave and continuous wave excited transducers are used to work,and the collected data is processed by three-parameter sine wave curve-fit method.The experimental results show that sinusoidal pulse method is proved to be a better choice to measure the admittance characteristics of transducers in a limited space.Compared with the results measured by impedance analyzer,the conductivity and susceptance errors are calculated to be 5.8% and 2.6%,and the combined uncertainty of amplitude and phase is calculated as 0.328 V and 0.099°.Finally,the pulse method is used to measure the resonance frequency of the transducer under the hydrostatic pressure of 0-40 MPa,which will shift with the increase of the pressure,and the diameter of the admittance circle will decrease.In order to further verify the reliability of the measurement device and method,a sensitivity measurement system for the calibration of hydrophones with a free-field reciprocity method under high hydrostatic pressure was established.The pulse method was used to measure the change of the sensitivity between 40 k Hz and 90 k Hz under hydrostatic pressure of40 MPa,and compared with the atmospheric pressure anechoic tank system.It is verified that the system has the ability to calibrate the sensitivity of the free field under high hydrostatic pressure,and the extended uncertainty of the calibration value is 0.83 d B.The results show that it is feasible to use pulse method to measure the impedance characteristics and the sensitivity of transducer in a small cavity.At the same time,it is proved that the acoustic parameters of the transducer can be calibrated under the highest hydrostatic pressure of 40 MPa.