Ibsen Stuart D, Au Whitlow W L, Nachtigall Paul E, Delong Caroline M, Breese Marlee
Marine Mammal Research Program, Hawaii Institute of Marine Biology, P.O. Box 1106 Kailua, Hawaii 96734-1106, USA.
J Acoust Soc Am. 2007 Oct;122(4):2446-50. doi: 10.1121/1.2772213.
This study documents the changes in peak frequency, source level, and spectrum shape of echolocation clicks made by the same dolphin performing the same discrimination task in 1998 and in 2003/2004 with spherical solid stainless steel and brass targets. The total average peak frequency used in 1998 was 138 kHz but in 2003/2004 it had shifted down nearly 3.5 octaves to 40 kHz. The total average source level also shifted down from 206 dB in 1998 to 187 kHz in 2003/2004. The standard deviation of these parameter values within time periods was small indicating a consistent difference between time periods. The average parameter values for clicks used when exposed to brass versus steel targets were very similar indicating that target type did not greatly influence the dolphin's average echolocation behavior. The spectrum shapes of the average clicks used in 1998 and in 2003/2004 were nearly mirror images of each other with the peak energy in 2003/2004 being concentrated where the 1998 clicks had the lowest energy content and vice versa. Despite the dramatic differences in click frequency content the dolphin was able to perform the same discrimination task at nearly the same level of success.
本研究记录了同一只海豚在1998年以及2003/2004年使用球形实心不锈钢和黄铜目标执行相同辨别任务时，其回声定位咔哒声的峰值频率、声源级和频谱形状的变化。1998年使用的总平均峰值频率为138千赫，但在2003/2004年，它下降了近3.5个八度，降至40千赫。总平均声源级也从1998年的206分贝降至2003/2004年的187千赫。这些参数值在各时间段内的标准差很小，表明不同时间段之间存在一致的差异。暴露于黄铜目标与钢目标时使用的咔哒声的平均参数值非常相似，表明目标类型对海豚的平均回声定位行为影响不大。1998年和2003/2004年使用的平均咔哒声的频谱形状几乎互为镜像，2003/2004年的峰值能量集中在1998年咔哒声能量含量最低的地方，反之亦然。尽管咔哒声频率内容存在巨大差异，但海豚能够以几乎相同的成功率执行相同的辨别任务。
