Au W W, Moore P W, Pawloski D A
Naval Ocean Systems Center, Kailua, Hawaii 96734.
J Acoust Soc Am. 1988 Feb;83(2):662-8. doi: 10.1121/1.396161.
Dolphins echolocate with short broadband acoustic signals that have good time resolution properties. Received echoes are often complex, with many resolvable highlights or components caused by reflection of the incident signal from external and internal boundaries of a target and from different propagational modes within a target. A series of experiments was performed to investigate how dolphins perceive complex echoes. Echoes were produced by a microprocessor-controlled electronic target simulator that captured each emitted click and retransmitted the signal back to the animal after an appropriate time delay. The use of this "phantom" target allowed for precise control of the number of highlights, the time separation between highlights, and the relative amplitudes of highlights in the simulated echoes. An echolocating dolphin was trained to perform a target detection task in the presence of masking noise using these phantom echoes. The properties of simulated echoes were systematically varied, and corresponding shifts in the dolphin's detection threshold were observed, allowing for inferences of how the dolphin perceived echoes. The dolphin performed like an energy detector with an integration time of approximately 264 microseconds.
海豚利用具有良好时间分辨率特性的短宽带声学信号进行回声定位。接收到的回声通常很复杂，有许多可分辨的亮点或成分，这些是由入射信号从目标的外部和内部边界以及目标内不同传播模式反射产生的。进行了一系列实验来研究海豚如何感知复杂回声。回声由微处理器控制的电子目标模拟器产生，该模拟器捕获每次发出的咔哒声，并在适当的时间延迟后将信号重新传输给动物。使用这种“虚拟”目标可以精确控制模拟回声中亮点的数量、亮点之间的时间间隔以及亮点的相对幅度。训练一只进行回声定位的海豚在存在掩蔽噪声的情况下使用这些虚拟回声执行目标检测任务。系统地改变模拟回声的特性，并观察到海豚检测阈值的相应变化，从而可以推断出海豚如何感知回声。这只海豚的表现类似于一个积分时间约为264微秒的能量探测器。
