Research On Sound Velocity Measurement Method Based On Echoenvelope Model

Marine measurement system plays a great role in the national metrology system.At present,acoustic measurement technology occupies a key position in marine metrology research.Accurately obtain seawater velocity is the core of acoustic measurement technology.The sound velocity of sea water is greatly influenced by the environment,which can be used to study the sound velocity measurement algorithm.This paper mainly studies the algorithm for obtaining sound velocity under pure water and atmospheric pressure.In this paper,the time-difference method is used to measure the sound speed.When the distance is known,the key to the measurement of sound speed is the accurate measurement of ultrasonic propagation time.On this basis,the propagation time measurement method based on the ultrasonic echo envelope model is adopted.(1)By analyzing the mathematical model of the ultrasonic receiving signal,the ultrasonic digital description method of the echo envelope model is designed: First,the improved wavelet threshold method is used to denoise the echo signal.According to the characteristics of the echo signal,the selection of the basis function and threshold selection rule of wavelet threshold are studied,and the improved threshold processing function is proposed.On this basis,the Hilbert transform principle is used to obtain the actual ultrasonic echo envelope(2)The improved particle swarm optimization algorithm is used to solve the ultrasonic propagation time when the least square objective function of signal envelope parameters reaches the minimum value.The particle model of the ultrasonic echo envelope signal and the least square objective function for evaluating the particle are constructed.In order to avoid such problems as parameter setting,"precocity" and unstable problems existing in the standard particle swarm optimization algorithm,the dynamic adjustment strategy of inertia weight is introduced and the strategy of increasing particle diversity is improved.The improved particle swarm optimization algorithm enhances the global searching ability and the local searching ability of the algorithm,so as to improve the convergence speed and accuracy of the algorithm,and provide an effective solution for accurately estimating the ultrasonic propagation time.(3)Sound velocity measurement experiment system based on echo envelope model is designed.Precision electric displacement platform to achieve the precise measurement of the ultrasonic propagation distance in the experiment,The standard platinum resistance thermometer and the precise temperature measurement bridge to achieve accurate detection of the temperature in the flume.The experimental platform is built,and the sound speed measurement experiment based on the echo envelope model is carried out.The collected data are analyzed and processed,and the conclusion that the echo envelope model is used to measure the sound speed is verified.A large number of experimental data are obtained to analyze it.In constant temperature pure water,the standard deviation of sound velocity is 0.0831,which is better than the cross-correlation method and the standard particle swarm optimization algorithm.