厦门和雷州湾海域中华白海豚click信号的分析与比较

The Analysis and Comparison of the clicks of Sousa chinensis in Xiamen Sea and Leizhou Bay

对福建厦门和广东雷州湾海域的中华白海豚（Sausachinensis）进行野外声信号的记录，选取2个海域中华白海豚所发射的共40个click信号串，其包含了1000个click信号，对其进行分析与对比．根据构成click信号的波形数量把click信号分为5类，分别为含1个、2个、3个、4个和5个及以上波形click信号．其中，2个海域中华白海豚的click信号均以含4个及以上波形为主，厦门海域中华白海豚click信号含4个及以上波形的占总数的84．2％；雷州湾中华白海豚该值为77．6％．2个海域含4个波形click信号在时长上存在显著差异（￡检验，t-3．39，DOF=84，P〈O．05），含5个及以上波形click信号时长同样存在显著差异（t检验，t=-10．01，DOF=682，P〈0．05）．分析比较了2个海域中华白海豚相邻click信号问的时间间隔，厦门海域中华白海豚相邻click信号间的时间间隔为7．8～349．2ms，雷州湾中华白海豚该值为3．3～124．3ms．利用中华白海豚所发射的click信号在浅海多径传播中不同路径的时延，对两海域中华白海豚的峰峰声源级进行估计，并对Au提出的海豚信号传播损失模型进行了传播损失上的修正．分析结果表明：厦门海域中华白海豚的峰峰声源级平均值为（179．4±8．7）dB，雷州湾中华白海豚该值为（204．1±5．4）dB由于雷州湾click信号录音海域的背景噪声级高于厦门录音点所在海域，初步分析这是造成雷州湾中华白海豚峰峰声源级高于厦门海域中华白海豚的主要原因之一．

Vocalizations of Indo-Pacific humpback dolphins(Sousa chinensis)were collected from the Xiamen Sea and Leizhou Bay. In this study,40click trains(including 1 000single clicks in total)were chosen and analyzed.Then the sample clicks were classified into five categories by the number of complete waveforms consisting in a single click(from 1-waveform to 5-waveform).Most of sample clicks from both sea areas are comprised of four or more complete waveforms,which accounts 84.2%of Xiamen Sea samples and 77.6% of Leizhou Bay samples.The distinction of duration of 4-waveform click between the two sea areas is significant(t-test,t= 3.39,DOF=84,p<0.05);similarly,large durational difference can also be found from 5-waveform clicks(t-test,t=-10.01,DOF =682,p<0.05).The inter-click interval of click in Xiamen Sea samples spans from 7.8ms to 349.2ms,but only ranges from 3.3 ms to 124.3ms in Leizhou Bay samples.Finally,source level of S.chinensis was calculated through a range estimated by the time delays of the signals via the surface and bottom reflection paths to the hydrophone,relative to the direct signal,the transmission loss pattern of click proposed by Willton.W.L.Au was revised at the same time.Results show that the averaged peak-to-peak source level of the S.chinensis is(179.4±8.7)dB in Xiamen Sea and(204.1±5.4)dB in Leizhou Bay,and it was concluded that higher underwater background noise level recorded in Leizhou Bay could be a key factor of source level of dolphin vocalizations in Leizhou Bay being larger than in Xiamen Sea.