Nosal Eva-Marie, Frazer L Neil
School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USA.
J Acoust Soc Am. 2007 Oct;122(4):1969-78. doi: 10.1121/1.2775423.
In an earlier paper [Nosal and Frazer Appl. Acoust. 61, 1187-1201 (2006)], a sperm whale was tracked in three-dimensions using direct and surface-reflected time differences (DRTD) of clicks recorded on five bottom-mounted hydrophones, a passive method that is robust to timing errors between hydrophones. This paper refines the DRTD method and combines it with a time of (direct) arrival method to improve the accuracy of the track. The position and origin time of each click having been estimated, pitch and yaw are then obtained by assuming the main axis of the whale is tangent to the track. Roll is then found by applying the bent horn model of sperm whale phonation, in which each click is composed of two pulses, p0 and p1, that exit the whale at different points. With instantaneous pitch, roll, and yaw estimated from time differences, amplitudes are then used to estimate the beam patterns of the p0 and p1 pulses. The resulting beam patterns independently confirm those obtained by Zimmer et al. [J. Acoust. Soc. Am. 117, 1473-1485 (2005); 118, 3337-3345 (2005)] with a very different experimental setup. A method for estimating relative click levels is presented and used to find that click levels decrease toward the end of a click series, prior to the "creak" associated with prey capture.
在一篇较早的论文中[Nosal和Frazer，《应用声学》61卷，第1187 - 1201页(2006年)]，使用安装在海底的五个水听器记录的滴答声的直接和表面反射时间差(DRTD)对一头抹香鲸进行了三维跟踪，这是一种对水听器之间的定时误差具有鲁棒性的被动方法。本文对DRTD方法进行了改进，并将其与(直接)到达时间方法相结合，以提高跟踪的准确性。在估计出每次滴答声的位置和起始时间后，通过假设鲸鱼的主轴与轨迹相切来获得俯仰角和偏航角。然后通过应用抹香鲸发声的弯角模型来找到横滚角，在该模型中，每次滴答声由两个脉冲p0和p1组成，它们在鲸鱼的不同点处发出。利用从时间差估计出的瞬时俯仰角、横滚角和偏航角，然后使用振幅来估计p0和p1脉冲的波束方向图。所得的波束方向图独立地证实了Zimmer等人[《美国声学学会杂志》117卷，第1473 - 1485页(2005年);118卷，第3337 - 3345页(2005年)]在非常不同的实验设置下所获得的结果。本文提出了一种估计相对滴答声级别的方法，并用于发现滴答声级在与捕食相关的“嘎吱声”之前朝着滴答声系列的末尾降低。
