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Source levels of echolocating free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) were calculated using a range estimated by measuring the time delays of the signals via the surface and bottom reflection paths to the hydrophone, relative to the direct signal. Peak-to-peak source levels for finless porpoise were from 163.7 to 185.6 dB re: 1 microPa. The source levels are highly range, dependent and varied approximately as a function of the one-way transmission loss for signals traveling from the animals to the hydrophone.
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Li et al. (2006) studied this question.
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