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Asymmetry and dynamics of a narrow sonar beam in an echolocating harbor porpoise
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10.1121/1.3683254
/content/asa/journal/jasa/131/3/10.1121/1.3683254
http://aip.metastore.ingenta.com/content/asa/journal/jasa/131/3/10.1121/1.3683254

Figures

Image of FIG. 1.
FIG. 1.

Recording set-up. (a) Animal’s perspective. Degrees are relative to the central hydrophone and when the animal is stationed 2 m in front of the array. Central hydrophone is indicated with an unfilled circle and peripheral hydrophones with filled circles. (b) Side view. Animal was positioned at a depth of 0.8 m and pointing downwards, the central hydrophone was at a depth of 1.2 m.

Image of FIG. 2.
FIG. 2.

(a) Averages of 464 harbor porpoise clicks recorded at five different angles (0°, 3°, 5°, 10°, and 15°) relative on axis. Sampling frequency was 500 kHz and signals were interpolated with a factor of 10. (b) Mean normalized spectra of 464 signals from Fig. 2(a). FFT size 600, Hanning window, sampling frequency 500 kHz.

Image of FIG. 3.
FIG. 3.

Received harbor porpoise echolocation signals on each hydrophone of the array, as seen from the animal’s perspective at 2 m range.

Image of FIG. 4.
FIG. 4.

(a) Horizontal beam pattern for 464 on-axis clicks of a harbor porpoise. (b) Interpolated and shifted horizontal beam pattern for all on-axis clicks. (c) Averaged horizontal beam pattern. Error bars show mean and 1 standard deviation of the measurements for each receiver. Black solid line is the averaged interpolated beam pattern. One standard deviation of all interpolated beams is depicted by the black dashed line. (d) Averaged horizontal beam pattern corrected for scanning movements. Dashed lines show 1 standard deviation. By correcting for the scanning, the standard deviation is reduced.

Image of FIG. 5.
FIG. 5.

(a) Vertical beam pattern for 464 on-axis clicks of a harbor porpoise. (b) Interpolated and shifted vertical beam pattern for all on-axis clicks. (c) Averaged vertical beam pattern. Error bars show mean and one standard deviation of the measurements for each receiver. Black solid line is the averaged interpolated beam pattern. The 1 standard deviation of all interpolated beams is depicted by the black dashed line. (d) Averaged vertical beam pattern corrected for scanning movements. Dashed lines show standard deviation. By correcting for the scanning, the standard deviation is reduced.

Image of FIG. 6.
FIG. 6.

(Color online) (a) Interpolated horizontal beam pattern for 464 harbor porpoise clicks (click # on y axis). Fat black line shows direction of interpolated maximum, thin black lines −3 dB and -6 dB BW. White horizontal lines represent beginning of new on-axis click train. The animal’s beam is on average 0.5° directed to the right. (b) Beam patterns shifted so that direction of maximal intensity is at 0°, i.e., accounting for the scanning movements of the animal. (c) Interpolated vertical beam pattern for each click (click # on y axis). Fat black line shows direction of interpolated maximum, thin black lines −3 dB and −6 dB BW. White horizontal lines represent beginning of new on-axis click train. Again the beam is often more off-axis before and after it is considered to be on-axis. (d) Beam patterns shifted so that direction of maximal intensity is at 0°, i.e., accounting for the scanning movements of the animal.

Image of FIG. 7.
FIG. 7.

The measured harbor porpoise transmission beam pattern compared to a modeled beam pattern using a porpoise click emitted by an oval piston with an aperture of 6.5 cm in the (a) horizontal and 8.3 cm in the (b) vertical plane.

Tables

Generic image for table
TABLE I.

Summary of toothed whale transmission beam pattern measurements.

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/content/asa/journal/jasa/131/3/10.1121/1.3683254
2012-03-15
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Asymmetry and dynamics of a narrow sonar beam in an echolocating harbor porpoise
http://aip.metastore.ingenta.com/content/asa/journal/jasa/131/3/10.1121/1.3683254
10.1121/1.3683254
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