Research On The Spectrum Characteristics And Spatial Characteristics Of Limited Data Noise In The North Yellow Sea

The spatial characteristics of marine environmental noise are important factors affecting array gain.In order to reduce the influence of environmental noise as much as possible,the study of noise field has been the focus of underwater acoustics research.Therefore,processing the marine environmental noise signals measured in the experiment to obtain relevant statistics,and conducting research on the spectral characteristics and spatial characteristics of marine environmental noise over time will be of great significance to the study of noise fields.This thesis mainly focuses on the spectral characteristics and spatial characteristics of noise in the North Yellow Sea.The results of underwater noise related statistics are obtained by processing experimental data,and causes are analyzed and summarized.The main research contents of this thesis include the following aspects:1?The experimental process is briefly introduced and the data processing methods are studied.Through the simulation calculation of the experimental data,it is found that the calculation using the data of the time period with the smaller variance is more representative of the stationary random process.The choice of filter bandwidth will affect the processing results of experimental data.In this paper,the spatial correlation coefficient value of uniform isotropic noise with a certain bandwidth is derived.Through theoretical and simulation research,we found that the correlation coefficient of uniform isotropic noise in the 1/3 octave band in the depth direction is close to the theoretical value,at the same time,suitable parameters were selected for subsequent data processing.2?The spectral characteristics of underwater noise are analyzed,including power spectrum and coherence coefficient.The study found that as the frequency increases,the noise power spectrum decreases,and the power spectrum in the evening is higher than in other time periods.The coherence of noise is high at low frequencies,while the coherence of noise is extremely low at high frequencies.As the depth increases,the vertical coherence coefficient of the noise decreases,and in the entire depth range of the North Yellow Sea.3?The spatial characteristics of underwater noise are analyzed,including correlation coefficient,intensity and vertical directivity.At the same time,the relationship between the correlation coefficient and the coherence coefficient is derived,and the quantitative relationship between the two statistics is analyzed.The change of the correlation coefficient with the depth basically conforms to the volume noise model,and the correlation of underwater noise in the evening is lower than at other times.The overall trend of noise intensity decreases with increasing frequency.The overall vertical directivity of underwater noise is consistent,with a maximum in the direction of-70°.4?The horizontal correlation coefficients after beamforming are calculated,and the horizontal correlation coefficients at different angles are obtained.The results show that under low frequency conditions,correlation coefficients in all directions with the horizontal distance are basically consistent at low frequency.The correlation coefficient value decreases as the angle approaches the sea floor at high frequencies.This is mainly related to the reflection of the sea floor and the sound source existing on the sea floor.