Research On The Characteristic Of Vector-Sensor Reverberation

Reverberation is all back-scatter acoustic signal for the random fluctuant surface and bottom, the disaccord of seawater during acoustic wave transmiting. Sound reverberation is a source of information on acoustic and oceanological properties of underwater waveguide and has been the subject of a great many theoretical and experimental investigations. Reverberation which occurs after emission signal, is primary interference for the active sonar, consumedly limits the operation distance and parameter estimate of the active sonar. It is necessary that the characters of reverberation are studied to improve the operation performance.While up to now, all researches on reverberation exceptionally measured the sound pressure. The vector sensor which alters oneness of the source information may measure the sound pressure p(t) and the orthogonal components of the particle velocity, v_x(t) ,v_y(t), v_z(t), data simultaneously at a given point in the acoustic field. Therefore, it has more information and may more comprehensively describe the sound scattering than the onefold sound pressure p(t).Based on theories of the sound scattering and the vector acoustic, the vector-sensor reverberation is researched in this thesis. Firstly, based on the cell scattering model and the point scattering model, the vector-sensor reverberation is researched and simulated. it shows that the vector sensor may restrain reverberation. Secondly, the low-frequency data of vector sensor reverberation in shallow sea are analyzed from the frequency, the probability, the time-space correlation of the sound pressure and the particle velocity, inter-pulse and copy correlation, it shows that the surface sound scattering is a main contributor to reverberation in shallow sea, the reverberation is distinctly anisotropic and has obvious certainty components, the sound pressure and the three orthogonal components of the particle velocity has weak correlation, and the correlation between the sound pressure p(t) and component of the particle velocity v_x(t) or v_y(t) appears to be much less than the correlation between p(t) and v_z(t). Thirdly, based on experimentation data and simulation model, Itakura distance and the time-frequency property (such as instantaneous frequency, the Wigner-Ville spectrum) are computed and researched, it shows that reverberation process is a local stable stochastic process, the WV spectrum of v_x(t) or v_y(t) is more distinct than v_z(t). Lastly, vector characteristics (such as the sound energy flux density), the coherence, directionality properties and the anti-reverberation capability of the single vector sensor and the vector line arrays are studied and analyzed. It shows that the vector sensor may more roundly and better obtain the spatial characteristics than the conventional hydrophone, and be propitious to research the mechanism of reverberation and the scattering characteristics, the vector sensor may suppress the reverberation contamination by 6-8 dB, the four element line arrays of pressure-gradient hydrophones have more about 8 dB suppression capability than the conventional hydrophone line array.