Research Of Themeasurement Method Of Seawater Sound Speed With Cross-correlation Function

The sound velocity of seawater is an important parameter to reflect the characteristics of seawater medium.Accurate sound velocity measurement can timely and effectively provide accurate sound velocity data for sounding instrument,range finder,sonar instrument and other underwater acoustic equipment to correct the measurement error,which is of great significance for ocean research,ocean monitoring and even national defense work.In this paper,the sound velocity measurement algorithm in water is studied to realize the accurate measurement of sound velocity in water.The paper starts from the following aspects:(1)This paper summarizes the characteristics of temperature distribution,temperature and salinity and pressure on sound velocity,and introduces the principle and characteristics of indirect measurement method of sound velocity and direct measurement method.This paper focuses on the principle and characteristics of jet velocity measurement of time difference method and the research of existing measurement technology.(2)Aiming at the strong correlation between the ultrasonic emission signal and the received signal and the weak correlation with the random noise,the ultrasonic propagation time is obtained by the cross correlation method.The ultrasonic wave propagation distance is measured by the double beam laser interferometer to realize the direct measurement of the sound velocity.(3)In order to improve the accuracy of time measurement,the ultrasonic signal is subjected to the wavelet threshold denoising technique.The cross-correlation method is used to obtain the parabola interpolation after the ultrasonic propagation time,and the ultrasonic propagation time is improved the measurement accuracy.(4)The experimental system was established by using constant temperature water tank,high precision platinum resistance thermometer and precision temperature measurement bridge,high resolution data acquisition system.The experiment was carried out in seawater and pure water respectively.The measurement of environmental data,the propagation distance of ultrasonic wave and the uncertainty of propagation time are evaluated,and the feasibility of the method based on mutual correlation method is verified.