Characteristic Analysis Of Noise Acoustic Field Of Fiber-Optic Vector Hydrophone

Ambient noise in the ocean, which is part of the total noise in the ocean measured by directivity hydrophones, is the interference background in underwater acoustic channel, and restricts all the SONAR systems. With the development of vector hydrophone, ambient noise in the ocean has been measured by piezoelectricity vector hydrophone, and some new vector characteristic of ambient noise in the ocean has been found. Fiber-optic vector hydrophone is a new type vector hydrophone. Comparing with piezoelectricity vector hydrophone, it has higher sensitivity, less transport loss, and more convenience for network connecting. Ambient noise in the ocean has been measured by fiber-optic vector hydrophone, and the characteristics of noise acoustic field have been analyzed theoretically and experimentallyTheoretically, the investigation status of ambient noise in the ocean in scalar hydrophone technology has been briefly reviewed. C/S modeling and CANARY modeling based on ray methods were discussed in detail. The investigation status of ambient noise in the ocean in vector hydrophone technology was summed to two vector modeling, i.e. vector C/S modeling and vector CANARY modeling. Contrasted the characteristic between scalar modeling and vector modeling, from the directivity function of vector hydrophone, the scalar modeling was extended to vector modeling by means of adding the given directivity function gene, a general way of extending scalar modeling of ambient noise in the ocean to vector modeling was found.Experimentally, firstly, the directivity of fiber-optic vector hydrophone was tested by the means of vibration platform test, standing wave sound field test and lake test, the result indicated that the method of standing wave sound field test had a better effect; secondly, the acceleration sensitivity and pressure sensitivity was analyzed, combined with the data of three outfield experiments, the experiment of DOA estimation was carried out using single fiber-optic vector hydrophone by CBF and MVDR beam form; finally, ambient noise in the ocean was analyzed in spectrum field which was measured by the fiber-optic vector hydrophone. The main conclusions were as follows:(1) The auto-spectra of pressure and particle velocity was calculated, the result showed that the ambient noise spectrum measured by fiber-optic vector hydrophone was lower 4-6dB than that measured by scalar hydrophone, the result consisted with the theoretic result at 4.8dB in case of isotropic noise field.(2) The cross-spectra of pressure and particle velocity was calculated, the analysis on the nature of ambient noise field was made in the cross-spectrum magnitude of pressure and particle velocity, coherence function of any point, and the phase spectrum. The result indicated, at the frequency range of 100~1000Hz, the ambient noise field of South China Sea is mostly isotropic noise field and anisotropic noise field constituted of a little part. Additionally, there was little correlation between pressure and particle velocity of vy, vz, vy also had little correlation with vz.(3) The phase difference between pressure and particle velocity of vy, vz, vy and vz over the range of -500~500 .(4) The temporal and spatial correlation coefficient matrix of pressure and particle velocity was calculated, at d=0,Ï„=0, the result consisted with the theoretic result in case of isotropic noise field.