Research On Measurement Of Ship Underwater Radiated Noise

In recent years,the influence of ship underwater radiated noise(SURN)on marine organisms receives more and more attention.The measurement of SURN is an important segment.In this paper,The measurement of SURN is studied,and the experiments have been performed to measure the SURN of a scientific research ship.First,the basic equation of the measurement of SURN has been introduced.Meanwhile,the similarities and differences between the measurement requirements,the measurement system deployment,the maneuvering method of the ship under test,the measurement uncertainty in the now-promulgated standards for underwater radiation noise of civil ships has been compared.The ISO standard has been taken as a reference to measure SURN of a scientific research ship under various working conditions.The similarities and differences between "monopole source level" and "dipole source level" are analyzed.According to the influence of sea surface interference in the measurement of SURN,the time average,the calculation of broadband spectrum level,depth average,and low frequency correction are proposed to eliminate the effects of sea-surface interference,the effectiveness of which has been verified by models.This paper study the influence of rough sea surface and sea bottom on underwater noise of ships by simulation.It is found that rough sea surface has limited influence on the measurement of SURN at low wind speeds;while high wind speed has little effect on low frequencies,but there is a 3d B error at high frequencies;The influence of seabed on the measurement of SURN is related to the seabed sediments,and mainly affects the low frequency SURN measurement.In general,the seabed has little impact on the ship's radiated noise measurement.Finally,a data processing method is proposed to eliminate the effects of sea surface interference.The sound pressure spectrum levels received by the hydrophone at different depths at the same speed were calculated and compared with the simulation results.The SURN at different side is calculated,which may be affected by ocean currents.The sound pressure levels in the one-third octave band at different ship speeds are calculated and compared with the radiated noise standards published by the DET NORSKE VERITAS.The dependence of the ship speed on the total sound pressure level of the broadband is calculated and compared with the classical ROSS model.The total broadband sound pressure level is slightly slower than the classic ROSS model.