Ibsen Stuart D, Au Whitlow W L, Nachtigall Paul E, DeLong Caroline M, Breese Marlee
Marine Mammal Research Program, Hawaii Institute of Marine Biology, PO Box 1106, Kailua, Hawaii 96734-1106, USA.
J Acoust Soc Am. 2010 Jun;127(6):3821-9. doi: 10.1121/1.3419905.
Echolocation clicks were recorded from an Atlantic bottlenose dolphin Tursiops truncatus trained to discriminate frequency filtered phantom targets in 1998 and in 2004. These clicks showed consistency within their spectra intensity profiles but only in a certain band of frequencies. In 2004 almost all the clicks were consistent within the 0-42 kHz band regardless of the presented target or the click source level. This region corresponded with previous data showing that in 2004 the dolphin perceived frequencies only from within the 29-42 kHz band during echolocation. Above 42 kHz the consistency was lost. In 1998 the consistent region was found only in the 90-100 kHz band showing a shift had occurred with time. This suggests the dolphin's echolocation strategy for these discrimination tasks centered on the use of clicks with the same controlled standard frequency content in a certain frequency band to investigate different targets. This consistent region shifted over time to maintain maximum signal to noise ratio of the echoes given certain changing limitations to the echolocation system. The shift in consistency over time indicates these consistent regions were not simply artifacts of click production but rather an active control of frequency content.
1998年和2004年，从一头经过训练能够辨别频率滤波后的虚拟目标的大西洋宽吻海豚（Tursiops truncatus）身上记录到了回声定位信号。这些信号在其频谱强度分布上显示出一致性，但仅在特定的频率范围内。2004年，几乎所有信号在0至42千赫频段内都是一致的，无论呈现的目标或信号源水平如何。该区域与先前的数据相符，表明2004年这头海豚在回声定位时仅能感知29至42千赫频段内的频率。在42千赫以上，一致性消失。1998年，一致区域仅在90至100千赫频段内被发现，表明随着时间推移发生了偏移。这表明这头海豚在这些辨别任务中的回声定位策略集中在使用具有相同受控标准频率内容的信号，在特定频段内来探测不同目标。随着时间推移，这个一致区域发生偏移，以在回声定位系统存在某些变化限制的情况下保持回声的最大信噪比。一致性随时间的偏移表明这些一致区域并非仅仅是信号产生的假象，而是对频率内容的主动控制。
