Research On Vector Hydrophone And Its Application For Underwater Platform

The vector hydrophone(VH) is combined by traditional sound pressure hydrophone and particle velocity hydrophone. It can colocately and synchronously measures sound pressure and all three orthogonal components of particle velocity at the same location in acoustic field, which is possible to improve performance of traditional underwater acoustic systems and broaden signal processing space. It has many advantages such as good directivity at low frequency and strong ability to immunize isotropic noise and can provides new ideas and methods for solving practical underwater acoustic engineering problems. With VH's maturity in technology and military demands, the VH is widely applied to all fields of underwater acoustic engineering, at present, it has become one of the most active research direction of underwater acoustic techonology.Based on the development and actuality of the VH technology and its application, the design theory of the co-oscillating VH, the influences of the dynamic properties of compliantly suspension system and near-field scattering and sway of underwater platform on the direction finding performance of the VH are all comprehensive and systemically studied in both theory and experiment.First of all, based on measurement principle of the co-oscillating VH, the sound wave receiving theory of the co-oscillating VH is systemically analyzed in theory, together with the dynamic properties of the compliantly suspension system, and the VH theoretically anlysis method is established. The expressions of sound wave receiving response of both unconstrained rigid sphere and elastic sphere in an acoustic plane-wave field are derived, and the relationship between the frequency response curves of velocity hydrophone and its geometrical dimension and density. The expression of pressure receiving response of the VH is derived, and the laws of the pressure distribution on the surface of velocity hydrophone and relationships between the pressure receiving coefficient of the VH and the parameters, such as the dimensions of the receiving surface, the radius of the velocity hydrophone, the layout position and radius of sound pressure hydrophone. Besides, the analyzing model of the VH-suspension system is established, and the resonant frequency of the system and its influence on the amplitude and phase of sound wave receiving responses of the VH is studied theoretically.The influences of the near-field scattering and sound transmission of the elastic spherical shell on the results of the VH measurement are studied in theory. The expressions of sound vector field of the scattering and transmission of plane wave on spherical shell, the influences of which on the amplitude and phase of sound wave receiving response and receiving directivity diagram of the VH are calculated, are derived. The theoretically analysis show that the influence of near-field scattering of the spherical shell on the receiving sound field of the VH is obviously frequency dependent, while the influence of sound transmission of the spherical shell on the receiving sound field of the VH depends mainly on the installation position of hydrophone, and the installation excursion influences largely on the results of measurement of hydrophone.Aiming at the practical situation when the VH is applied to underwater platform, the target direction finding performance of the VH are systemically studied in several aspects as channel variances in amplitude and phase characteristics, sound scattering of the platform and its random sway in water. The direction finding accuracy error due to channel variances in amplitude and phase characteristics is analyzed theoretically. Based on the established calculation model of influences on direction finding by near-field scattering of platform, the influences on direction finding accuracy by the incident wave frequency and the incident angle and the installation position of hydrophone are analyzed. Besides, the movement model of the random sway platform is established, and the direction finding error due to the random sway of the observation platform is analyzed. The characteristic of three kind of direction finding error mentioned above are compared and analyed, and the methods of eliminating and decreasing influence on direction finding error are proposed.The experiment on influence of near-field sound scattering of elastic shell on the sound field measurement of the VH and its target direction finding performance are carried in the tank and anechoic tank. The influences on sound wave receiving responses and receiving directivity diagram of the VH and its target direction finding performance by the scattering of the elastic spherical shell, the cylindrical shell with hemi-spherical caps on the ends and short cylindrical shell with the circular plate on the ends are analyzed, respectively. The experimental results validated the results of theoretical analysis, and also lay the experimental foundation for the future practical application of the VH in underwater acoustic engineering.