Analytic formulas for acoustic interference patterns in shallow water are derived by ray method. Which can be used to guide acoustic measurements with limited horizontal distances. Some necessary approximations are ta...Analytic formulas for acoustic interference patterns in shallow water are derived by ray method. Which can be used to guide acoustic measurements with limited horizontal distances. Some necessary approximations are taken for a concise expression. The analytic for- mulas represent the quantitative relationships between the interference-pattern and the signal frequency, bandwidth, depth of source and horizontal distance. Monofrequent signals, com- plicated signals and frequency-modulated signals are all studied. Several inferences are also deduced from the formulas. Both numerical simulations and experiment data are presented to prove that these formulas and their inferences can describe the critical characters of the acoustic interference pattern in the waveguide with a satisfying precision.展开更多
Using the modal dispersion equation with the phase-integral approaches, and con-sidering an eddy (or water mass) as a sound channel disturbance, the effects of the undisturbed channel, cold-core eddy and warm-core edd...Using the modal dispersion equation with the phase-integral approaches, and con-sidering an eddy (or water mass) as a sound channel disturbance, the effects of the undisturbed channel, cold-core eddy and warm-core eddy on the acoustic propagation characteristics are dis-cussed. According to the solutions of the dispersion equation, the relation between the modal Parameters (phase velocity, group velocity and interference distance) and the eddy intensity is obtained. When the plane wave (with an incident angle a) travels toward the center of a warm-core eddy (disturbed intensity BM ) 'double channel phenomenon' will take place in case of sin2 α < BM < 2(1 - cosα), and then the modal phase velocity and interference distance will have anomalous changes which are completely different from the case of the cold-core eddy.展开更多
Acoustic interference of atmosphere has been an attractive research area because of its potential effect on environment,water resources,ecology,agriculture,and other areas.However,it is also a controversial topic beca...Acoustic interference of atmosphere has been an attractive research area because of its potential effect on environment,water resources,ecology,agriculture,and other areas.However,it is also a controversial topic because of the difficulty of quantitative assessment and high operating costs.In this study,a novel acoustic interference technology is proposed that uses strong lowfrequency sound waves.There is no chemical pollution or dependence on airborne vehicles,and it can be remotely controlled at low cost.A complete equipment system for acoustic atmospheric interference technology is established,based on which a series of experimental studies on cloud and precipitation response under acoustic action are performed,mainly including the radar echo intensity,cloud microphysical characteristics and the spatial distribution of ground rainfall intensity.The trigger and periodic effect of the acoustic waves on the cloud are proposed to be the key responses of acoustic atmospheric interference.This study is important to further research on atmosphere interference technology based on low frequency strong sound waves.展开更多
文摘Analytic formulas for acoustic interference patterns in shallow water are derived by ray method. Which can be used to guide acoustic measurements with limited horizontal distances. Some necessary approximations are taken for a concise expression. The analytic for- mulas represent the quantitative relationships between the interference-pattern and the signal frequency, bandwidth, depth of source and horizontal distance. Monofrequent signals, com- plicated signals and frequency-modulated signals are all studied. Several inferences are also deduced from the formulas. Both numerical simulations and experiment data are presented to prove that these formulas and their inferences can describe the critical characters of the acoustic interference pattern in the waveguide with a satisfying precision.
文摘Using the modal dispersion equation with the phase-integral approaches, and con-sidering an eddy (or water mass) as a sound channel disturbance, the effects of the undisturbed channel, cold-core eddy and warm-core eddy on the acoustic propagation characteristics are dis-cussed. According to the solutions of the dispersion equation, the relation between the modal Parameters (phase velocity, group velocity and interference distance) and the eddy intensity is obtained. When the plane wave (with an incident angle a) travels toward the center of a warm-core eddy (disturbed intensity BM ) 'double channel phenomenon' will take place in case of sin2 α < BM < 2(1 - cosα), and then the modal phase velocity and interference distance will have anomalous changes which are completely different from the case of the cold-core eddy.
基金supported by the National Key R&D Program of China(Grant No.2017YFC0403600)the National Natural Science Foundation of China(Grant Nos.91847302 and 51879137)+1 种基金the Special Finance of Qinghai Provincethe State Key Laboratory of Hydro-science and Engineering(Grant No.2017-KY-04)。
文摘Acoustic interference of atmosphere has been an attractive research area because of its potential effect on environment,water resources,ecology,agriculture,and other areas.However,it is also a controversial topic because of the difficulty of quantitative assessment and high operating costs.In this study,a novel acoustic interference technology is proposed that uses strong lowfrequency sound waves.There is no chemical pollution or dependence on airborne vehicles,and it can be remotely controlled at low cost.A complete equipment system for acoustic atmospheric interference technology is established,based on which a series of experimental studies on cloud and precipitation response under acoustic action are performed,mainly including the radar echo intensity,cloud microphysical characteristics and the spatial distribution of ground rainfall intensity.The trigger and periodic effect of the acoustic waves on the cloud are proposed to be the key responses of acoustic atmospheric interference.This study is important to further research on atmosphere interference technology based on low frequency strong sound waves.
