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| 2. |
- Starkhammar, Josefin, et al.
(författare)
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Editorial: 47-channel burst-mode recording hydrophone system enabling measurements of the dynamic echolocation behavior of free-swimming dolphins
- 2009
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Ingår i: Journal of the Acoustical Society of America. - : A I P Publishing LLC. - 0001-4966 .- 1520-8524. ; 126:3, s. 959-962
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Detailed echolocation behavior studies on free-swimming dolphins require a measurement system that incorporates multiple hydrophones (often andgt; 16). However, the high data flow rate of previous systems has limited their usefulness since only minute long recordings have been manageable. To address this problem, this report describes a 47-channel burst-mode recording hydrophone system that enables highly resolved full beamwidth measurements on multiple free-swimming dolphins during prolonged recording periods. The system facilitates a wide range of biosonar studies since it eliminates the need to restrict the movement of animals in order to study the fine details of their sonar beams.
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| 3. |
- Starkhammar, Josefin, et al.
(författare)
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Separating overlapping click trains originating from multiple individuals in echolocation recordings
- 2011
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Ingår i: JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA. - : Acoustical Society of America. - 0001-4966 .- 1520-8524. ; 129:1, s. 458-466
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Tidskriftsartikel (refereegranskat)abstract
- Recordings of the acoustic activity of free-swimming groups of echolocating dolphins increase the likelihood of collecting overlapping click trains, originating from multiple individuals, in the same set of data. In order to evaluate the click properties of each individual based on such recordings it is necessary to identify which clicks originate from which animal. This paper suggests a computationally efficient strategy to separate overlapping click trains originating from multiple free-swimming bottlenose dolphins, enabling echolocation analysis at an individual level on several animals. This technique is based on sequential matching of the frequency spectra of successive clicks. The clicks are grouped together as individual click trains if the correlation coefficients between clicks are higher than a pre-set threshold level. The robustness of the algorithm is tested by adding artificially generated white Gaussian noise and comparing the results with other comparable commonly used methods based on inter-click intervals, centroid frequencies, and amplitude levels. The described method is applicable to a variety of experimental and observational contexts, e. g., those regarding echolocation development of calves, the hypothesized acoustic "etiquette" among dolphins when investigating the same object, and the possible occurrence of eavesdropping in large dolphin pods.
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| 4. |
- Starkhammar, Josefin, et al.
(författare)
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The dynamics of the bottlenose dolphin sonar beam.
- 2008
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 124:4
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Tidskriftsartikel (refereegranskat)abstract
- Much research on dolphin echolocation has focused on animals that have been trained to remain stationary or to carry a device that allows the animals to move but restricts the location of the sonar beam. In such cases, a small number of hydrophones measures sonar characteristics while dolphins solve echolocation tasks. As a result, much is known about the beam axis but relatively little is known about other parts of the beam. One reason for this disparity is that it has been difficult to interpret the results from off axis measurements using a small number of hydrophones (that may or may not sample simultaneously). In this paper, we report results from a system of 47 hydrophones in a 0.75 x 0.75 m(2) matrix that allowed measurements to be made at multiple locations in the beam simultaneously, with a sample rate of 1 Msamples. The system both visualizes and records echolocation clicks in real time across the whole cross section of the beam, hence allowing the full dynamics of the sonar beam to be revealed. As a demonstration of the system's utility, we present results obtained with the system to assess the acoustic properties of clicks produced spontaneously by free-swimming dolphins.
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