United States Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific, Code 71510, 53560 Hull Street, San Diego, California 92152, USA.
J Acoust Soc Am. 2013 Mar;133(3):1796-810. doi: 10.1121/1.4788997.
When echolocating, dolphins typically emit a single broadband "click," then wait to receive the echo before emitting another click. However, previous studies have shown that during long-range echolocation tasks, they may instead emit a burst, or "packet," of several clicks, then wait for the packet of echoes to return before emitting another packet of clicks. The reasons for the use of packets are unknown. In this study, packet use was examined by having trained bottlenose dolphins perform long-range echolocation tasks. The tasks featured "phantom" echoes produced by capturing the dolphin's outgoing echolocation clicks, convolving the clicks with an impulse response to create an echo waveform, and then broadcasting the delayed, scaled echo to the dolphin. Dolphins were trained to report the presence of phantom echoes or a change in phantom echoes. Target range varied from 25 to 800 m. At ranges below 75 m, the dolphins rarely used packets. As the range increased beyond 75 m, two of the three dolphins increasingly produced packets, while the third dolphin instead utilized very high click repetition rates. The use of click packets appeared to be governed more by echo delay (target range) than echo amplitude.
当回声定位时，海豚通常会发出单个宽带“咔哒”声，然后等待接收回声，再发出另一个咔哒声。然而，之前的研究表明，在远程回声定位任务中，它们可能会发出一连串的“数据包”，即几个咔哒声，然后等待数据包的回声返回，再发出另一个咔哒声数据包。使用数据包的原因尚不清楚。在这项研究中，通过让受过训练的宽吻海豚执行远程回声定位任务来检查数据包的使用情况。这些任务的特点是“幻影”回声，这是通过捕获海豚发出的回声咔哒声，用脉冲响应卷积咔哒声来创建一个回声波形，然后将延迟、缩放的回声广播给海豚来实现的。海豚被训练来报告幻影回声的存在或幻影回声的变化。目标范围从 25 米到 800 米不等。在低于 75 米的范围内，海豚很少使用数据包。随着距离超过 75 米，三只海豚中的两只越来越多地发出数据包，而第三只海豚则利用非常高的点击重复率。数据包的使用似乎更多地受到回声延迟（目标范围）的控制，而不是回声幅度。
