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First published online June 29, 2006
Journal of Experimental Biology 209, 2726-2733 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02306
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Acoustic radiation from the head of echolocating harbor porpoises (Phocoena phocoena)

Whitlow W. L. Au1,*, Ronald A. Kastelein2, Kelly J. Benoit-Bird3, Ted W. Cranford4 and Megan F. McKenna4

1 Marine Mammal Research Program, Hawaii Institute of Marine Biology, P.O. Box 1106, Kailua, HI 96734, USA
2 Sea Mammal Research Co., Harderwijk, The Netherlands
3 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503, USA
4 Biology Department, San Diego State University, San Diego CA 92182, USA


Figure 1
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  		Fig. 1. Three suction cup hydrophone configurations used to measure the sound field at the surface of the porpoise head. (A) The line configuration, (B) the T1 and (C) T2 configurations. The Label R in each panel denotes the reference hydrophone, which was placed at the same position on the animal for all three array configurations (see lower panels). Each hydrophone was also designated by a number.

 

Figure 2
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  		Fig. 2. Representative echolocation signal waveforms measured by each of the hydrophones in the line (top) and T1 (bottom) geometries.

 

Figure 3
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  		Fig. 3. Peak-to-peak sound pressure level (mean ± s.d.) measured by the four suctioncup hydrophones for (A) Daan and (B) Jordy. 300 values were used to compute the mean and s.d. The CT scan showing a parasagittal slice of a harbor porpoise was scaled to the head size of Daan and Jordy. The phonic lips are shown as the two red dots towards the back of the CT scan. The speed of sound within the melon is color scaled, with red being the lowest velocity and yellow, the highest. The positions of the hydrophones are represented by the blue dots on the surface of the animal's head.

 

Figure 4
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  		Fig. 4. The results from the combined T1 and T2 configurations for both porpoises. (A) The approximate positions of the sensor are overlayed on the CT scans with the color of the sensor corresponding to the acoustic results (B) for each animal. Other details as in Fig. 3.

 

Figure 5
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  		Fig. 5. (A-C) Examples of changes in the relative amplitudes of the signals in the line array configuration over three consecutive clicks.

 

Figure 6
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  		Fig. 6. (A-C) Examples of changes in the relative amplitude of the signals in the T1 array configuration over three consecutive clicks.

 

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© The Company of Biologists Ltd 2006