Source Range Estimation Based On Pulse Waveform Matching In Complex Ocean Environments

Source range estimation is an important issue in acoustic inverse problems.Considerable methods of estimating source range have been proposed recently,most of which are concentrated in shallow water.In contrast,researches on source range estimation in deep water and transitional zone are insufficient.Due to existing of dispersion and multipath effects in the propagation for wideband pulse signals,the depth structure of received pulse waveforms is different with the source range.Base on this,a method for source range estimation is presented by correlating the experimental and simulated pulse signals with depth structure information.In this method,depth structures of pulse signals received by a vertical line array are utilized.We firstly delay the pulse signals recorded by all the channels.Next,all delayed signals are supposed to generate a long time pulse sequence.Finally we estimate the source range by correlation matching between the pulse waveforms of received and simulated signals.This method transforms the two-dimensional(2D)pulse waveform(depth and temporal distribution)into one-dimensional(temporal distribution),which not only reserves the distribution structure of pulse signal,but also reduces the calculation amount on correlation matching process.This method is not restricted to ocean environments,which can be applied to deep water,shallow water and transitional zone.Although in a slope environment,sound propagation is effected by the bottom significantly and the received signal is relatively complex.For the sources in the environment with slope bottom and deep water,this method is effective and the mean relative error of range estimation is less than 7%.Based on the above method,the effect on the source range estimation by three-dimensional(3D)effect in a wedge-shaped environment is also studied.Using the ray model,transmission loss in the wedge waveguide is calculated firstly and the acoustic propagation affected by the existence of 3D effect is analyzed.The result shows that the horizontal refraction effect becomes more obvious with the increasing of the range,and the difference gradually increases between the 3D result and the result calculated by 2D model.By comparing the received pulse waveforms in 2D and 3D acoustic fields,multiple mode arrivals or modal shadow zones in some receiving positions is subsequently confirmed.Finally,source range estimation is studied by matching the waveforms of full wave solution as well as the separated normal modes,and the results of source range estimation affected by 3D effect are analyzed.Due to the existence of the three-dimensional effect,source range can be accurately estimated by applying the 3D model,whereas the source range estimated by 2D model greatly differs from the actual value,which is larger at most ranges.