Muller Mark W, Au Whitlow W L, Nachtigall Paul E, Allen John S, Breese Marlee
Marine Mammal Research Program, Hawaii Institute of Marine Biology, 46-007 Lilipuna Road, Kaneohe, Hawaii 96744-3617, USA.
J Acoust Soc Am. 2007 Oct;122(4):2255-62. doi: 10.1121/1.2769973.
A dolphin's ability to discriminate targets may depend greatly on the relative amplitudes and the time separations of echo highlights within the received signal. Previous experiments with dolphins varied the physical parameters of targets, but did not fully investigate how changes in these parameters correspond with the scattered acoustic wave forms and the dolphin's subsequent response. This experiment utilizes a phantom echo system to test a dolphin's detection response to relative amplitude differences of secondary and trailing echo highlights and the time separation differences of all the echo highlights both within and outside the animal's integration window. By electronically manipulating the amplitude and temporal separation of the echo highlights, the underlying acoustic classification cues are more efficiently investigated. The animal successfully discriminated between a standard echo signal and one with the secondary highlight amplitude lowered by 7 dB from the standard. Furthermore, the animal successfully discriminated between a standard echo signal and one with the trailing highlight amplitude lowered by 3 dB from the standard and also a standard echo signal and one with a time separation of 150 mus between the secondary and trailing highlights.
海豚辨别目标的能力可能在很大程度上取决于接收信号中回声亮点的相对幅度和时间间隔。先前对海豚进行的实验改变了目标的物理参数，但并未充分研究这些参数的变化如何与散射声波形式以及海豚随后的反应相对应。本实验利用模拟回声系统来测试海豚对二次回声亮点和尾随回声亮点的相对幅度差异以及动物整合窗口内外所有回声亮点的时间间隔差异的检测反应。通过电子方式操纵回声亮点的幅度和时间间隔，可以更有效地研究潜在的声学分类线索。该动物成功地区分了标准回声信号和二次亮点幅度比标准降低7分贝的回声信号。此外，该动物成功地区分了标准回声信号和尾随亮点幅度比标准降低3分贝的回声信号，以及标准回声信号和二次亮点与尾随亮点之间时间间隔为150微秒的回声信号。
