Research On Measurement Of Radiated Noise Of Submarines

The sound level of low-noise submarines is close to the environmental noise of the ocean. In the desired distance of measurement, the sound level of the arrived signal will be lower than the level of the environmental noise at the measurement point because of the transmission loss. In order to solve the problem of measuring the radiated noise of low-noise submarines, the experimental base of the naval has constructed two measurement systems aiming at low noise, one is the vertical line array, the other is the sound vector sensor. According to the background here, the abnormality of the transmission loss due to the sound field environment and the solid source effect of submarines can not be ignored.The sound transmission is obviously influenced by the surface and the bottom of the sea in the shallow water. The thesis studies the abnormality of transmission loss of the near-field in the shallow water , which does not obey the transmission loss law of spherical waves. So a sound field adjustment when measuring the radiated noise of the low-noise submarines is necessary.The submarine is a complex solid source. The thesis discusses the basis of the sound radiation due to vibration and the mechanics of the three main sources of the submarine. Then calculation methods are given and the spatial distribution characteristics of the radiated sources of submarines are acquired. The two systems of vertical line array based on sound pressure measurement and sound vector sensor based on united measurement of sound pressure and particle velocity are introduced and so do the relevant assistant methods.In order to get the far-field characteristics of radiated noise of submarines by near-field measurement and then calculate the source level, a distributed sound source model in the near-field of submarines is put forward and the distribution of the near-field and the far-field are calculated. A transformation from near-field to far-field is carried through according to the Helmholtz integration equation. The two systems of low-noise measurement should have comparable equivalence. The...