| After the storage of Three Gorges reservoir,the navigation conditions in the upper reaches of Yangtze River from Fuling to Fengdu have been improved year by year,the ship passage has been increasing,and the ships have become significantly larger,and the impact of ship noise on the ecological environment has become more and more prominent,causing a certain degree of impact on the watershed ecosystem and sensitive areas of water ecological environment.Therefore,based on the field measurements and numerical simulations,this paper mainly analyzes the underwater radiated noise characteristics of different ships based on the analysis of the underwater radiated noise characteristics of different ship types and tonnage,and the influence of ship speed and tonnage on the sound pressure and energy share,so as to have a general understanding of the underwater noise of typical common ships in the upper reaches of Yangtze River.The results of the study are shown as follows.(1)In this paper,we firstly determine the ship type of the main passing ships in the Fuling-Fengdu section of the upper Yangtze River channel based on the analysis of ship passage;then we build a monitoring system that can be used for ship underwater noise measurement based on the basic theory of underwater acoustic wave propagation and the basic theory of ship underwater noise measurement,combined with the actual topographic conditions of the basin and the basic structural parameters of each measured ship,and design a good field of experimental equipment.Finally,the actual measured underwater noise signals are pre-processed by means of sound signal processing,such as Fourier transform and wavelet transform,in order to ensure the accuracy of the experimental results and better prepare for the analysis of different ship underwater noise source characteristics later on.(2)Through on-site monitoring and actual data analysis,we can get that the radiation difference of bulk carrier,river passenger ship and container ship is not big,the sound pressure level of ship radiation noise is basically between 150～185d B,and when the ship driving speed increases from 6km/h to 13km/h,the sound source signal amplitude and sound pressure value of ship radiation noise increases,the ship radiation noise energy is mainly concentrated in low frequency and 2～4th order high frequency band.The radiation noise characteristics of speedboats are obviously different from those of other three types of ships,the speedboat travels too fast,generally the maximum speed can reach 50km/h～60km/h,so its radiation noise sound pressure level is also larger,the sound pressure level of the speedboat measured in this paper is between 160～205d B,and there are also radiation noise source signal amplitude and sound pressure value increase with the ship travel speed The ship radiation noise energy is mainly concentrated in the low frequency and the 1st～3rd order high frequency band.(3)By monitoring and analyzing the radiation noise of bulk carriers of different tonnage,we get that when their driving speed is the same,the radiation noise of ships increases with the increase of ship tonnage,that is,the radiation noise of ships is positively related to the ship tonnage;analyzing the noise data under different ship driving speed,we find that when the ship driving speed is low(6km/h～8km/h),the increase of sound pressure level is more obvious;when the ship driving speed is high(10km/h～13km/h),the increase of sound pressure level is relatively less obvious.At high speed(10km/h～13km/h),the increase of sound pressure level is not so obvious.And with the increase of ship speed,the difference between the sound pressure level of low tonnage ship radiation noise is gradually reduced.The radiation noise energy of the ship is mainly concentrated in the low frequency and the 2nd～4th order high frequency band.(4)Based on the numerical simulation results,it can be seen that the results of different source frequencies on the ship radiation noise sound field simulation is larger,when the source frequency increases,the ship radiation noise sound field distribution increases,the sound field propagation loss increases;the biggest difference between the sound field attenuation law of a single ship noise source and multiple ship noise sources is that due to the coupling superposition effect between individual sound waves,the physical amount of vibration at each point in the overlapping area of the wave is equal to the vector sum of the physical amount caused by each column of waves at that point,so there are strengthening and weakening areas in the sound field. |
