基于Echoview声学数据后处理系统的背景噪声扣除方法

Study on background noise removal based on Echoview acoustic data post-processing system

中文关键词: 回声积分  时变增益  背景噪声消除  虚拟变量法 

英文关键词: Echo-integration  Time Varied Gain(TVG)  Background noise subtraction  Virtual variable method

中文摘要:

      基于2012年2-3月南海中部鱼类资源声学调查资料，利用Echoview系统中虚拟变量模块的功能，探讨扣除背景噪声对声学映像、单脉冲回声信号图、海里面积散射系数(NASC)和体积反向散射强度(Sv)的影响。结果显示，背景噪声对120kHz数据的干扰明显强于38kHz；随着水深逐渐增加，扣除背景噪声后，120kHz声学映像变化亦比38kHz更加明显；扣除背景噪声时，换能器表面1 m处的Sv值不断改变过程中，相同水层中不同频率数据的NASC和Sv的变化差异明显，其差异程度因具体水层而异，相同频率数据在不同水层的NASC和Sv的变化差异亦明显。分析认为，扣除背景噪声非常必要；本研究的方法能够较好地排除背景噪声，是提高资源评估准确度的有效手段。

英文摘要:

      Based on the data from fishery resource acoustic surveys in central South China Sea from February to March 2012, using Virtual Variable Module of Echoview system, the effects of subtracting background noise on echogram, Ping echogram, Nautical Area Scattering Coefficient (NASC) and Volume Backscattering Strength (Sv) were investigated. The results showed that the interference of background noise on 120 kHz transducer was much stronger than that on 38 kHz transducer. After subtracting background noise, the variation of echogram from 120 kHz transducer was much more obvious than that from 38 kHz as the depth range increases; as the Sv at 1 m to the transducer surface (Sv1m for short) changed,the variation of NASC and Sv differentiated obviously between frequencies in the same depth-layer and the extent of variation was dependent on the depth layers,and the variation of NASC and Sv from transducer of the same frequency differentiated obviously between depth layers too. The distinguishing features of variation of NASC and Sv were important bases for determining Sv1m. According to the analysis, it was absolutely essential to remove background noise in the post-processing of fishery acoustic data; background noise could be removed well by this method, which was a valid means of enhancing the accuracy of acoustic estimation.