Signal processing techniques for acoustic measurement of sperm whale body lengths.
Signal processing techniques for acoustic measurement of sperm whale body lengths.
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用于声学测量抹香鲸身体长度的信号处理技术。
DOI：
10.1121/1.416984
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
J. Goold
中科院分区：
文献类型：
--
作者：
J. Goold
波形互相关和倒频谱分析被用来证明可能的技术，以测量脉冲间隔内抹香鲸声纳点击。抹香鲸发出的滴答声的结构是一系列衰减的宽带脉冲，它们之间的时间间隔是鲸蜡油中声速和鲸头内鲸蜡囊长度的函数。对点击信号进行带通滤波，并对滤波后的信号进行波形互相关，以获得相关函数中的最大值。这种最大值出现在经滤波的咔嗒声波形内的连续脉冲在复制波形时移脉冲间间隔的整数倍之后对准时。作为一种替代方法，倒频谱分析被用于对单个点击的频谱，发现其中包含与脉冲间间隔的倒数相对应的周期的波纹。可变的信号质量导致的结论是，没有一种方法是可靠的点测量IPI从个人点击。然而，通过任一方法计算IPI，在6分钟的序列中进行数百次点击，并使用移动平均值平滑结果，可以获得真实的平均值，并观察到脉冲间隔随潜水时间的趋势。脉冲间隔一般被发现随着潜水时间的减少，按照已知的声速特性的鲸蜡油在压力增加。通过对每个咔哒声序列进行倒谱分析获得的脉冲间间隔的平均值用于估计相应动物的体长。
Waveform cross correlation and cepstrum analysis were used to demonstrate possible techniques to measure pulse intervals within sperm whale sonar clicks. The structure of sperm whale clicks takes the form of a series of decaying broadband pulses separated by a time interval that is a function of sound velocity in spermaceti oil and the length of the spermaceti sac within the whales' head. Click signals were bandpass filtered and waveform cross correlation used on the filtered signals to obtain maxima in the correlation function. Such maxima occur when successive pulses within the filtered click waveforms align after time shifting of the replica waveform by integer multiples of the interpulse interval. As an alternative approach, cepstrum analysis was used on the spectra of individual clicks, which were found to contain ripples with periods corresponding to the reciprocal of the interpulse interval. Variable signal quality lead to the conclusion that neither method was reliable for spot measurements of IPIs from individual clicks. However, calculating IPIs by either method for several hundred clicks in 6-min sequences, and smoothing the results with moving averages, allowed realistic mean values to be obtained and interpulse interval trends to be observed with dive time. Interpulse intervals were generally found to decrease with dive time, in accordance with known sound velocity characteristics of spermaceti oil under increasing pressure. Mean values of interpulse intervals obtained by cepstrum analysis for each click sequence were used to estimate body lengths of the respective animals.