Probability density functions for hyperbolic and isodiachronic locations

Animal locations are sometimes estimated with hyperbolic techniques by estimating the difference in distances of their sounds between pairs of receivers. Each pair specifies the animal\u27s location to a hyperboloid because the speed of sound is assumed to be spatially homogeneous. Sufficient numbers of intersecting hyperboloids specify the location. A nonlinear method is developed for computing probability density functions for location. The method incorporates a priori probability density functions for the receiver locations, the speed of sound, winds, and the errors in the differences in travel time. The traditional linear approximation method overestimates bounds for probability density functions by one or two orders of magnitude compared with the more accurate nonlinear method. The nonlinear method incorporates a generalization of hyperbolic methods because the average speed of sound is allowed to vary between different receivers and the source. The resulting isodiachronic surface is the locus of points on which the difference in travel time is constant. Isodiachronic locations yield correct location errors in situations where hyperbolic methods yield incorrect results, particularly when the speed of propagation varies significantly between a source and different receivers

Vad fan är solidaritetsförklaringen?

In the recent decades, Sweden, traditionally a neutral and non-aligned country, has taken a huge leap in its change of defence- and security policy towards the European Union and its fellow Nordic countries. Sweden has even gone to the extant as to say, that Sweden will not remain passive if another member-state of the European Union is subject to an armed attack. This dissertation raises the question where this idea came from and why Sweden stand by it. By using process-tracing as a method to cast light on this somewhat new chapter in Swedish foreign policy affairs, we are offered an insight to why and where this declaration of solidarity came to be. To say the least, the reason is spelled EU. Sweden’s decision to become an active team player in the European circus along with the Lisboan treaty has once and for all shattered the Swedish neutrality as well as declaring a policy it can not uphold. In the end it seams, it is only a game of words

Toothed whale auditory brainstem responses measured with a non-invasive, on-animal tag

This work was funded by Grant No. N00014-20-1-2748 from the United States Office of Naval Research (ONR) awarded to M.W. Tag development was supported by ONR Grant Nos. N00014-16-1-2852, N00014-18-1-2062, and N00014-20-1-2709. M.J. was supported by the Aarhus University Research Foundation and the EU H2020 research and innovation program under Marie Skłodowska-Curie Grant No. 754513.Empirical measurements of odontocete hearing are limited to captive individuals, constituting a fraction of species across the suborder. Data from more species could be available if such measurements were collected from unrestrained animals in the wild. This study investigated whether electrophysiological hearing data could be recorded from a trained harbor porpoise (Phocoena phocoena) using a non-invasive, animal-attached tag. The results demonstrate that auditory brainstem responses to external and self-generated stimuli can be measured from a stationary odontocete using an animal-attached recorder. With additional development, tag-based electrophysiological platforms may facilitate the collection of hearing data from freely swimming odontocetes in the wild.Publisher PDFPeer reviewe

Vocal behaviour of the Great Cormorant Phalacrocorax carbo sinensis during the breeding season

Capsule Great Cormorants Phalacrocorax carbo sinensis use vocal communication during the breeding season, with males being particularly vocal earlier in the breeding cycle and showing individual variation in some calls, which could be used for individual recognition. Aims To identify and describe vocal behaviour of Great Cormorants, to link calls with observed behaviours and to explore if the calls had potential for individual recognition. Methods We followed 21 nesting pairs of Great Cormorants by videoing and recording their vocal behaviour throughout the breeding season. We linked calls with observed behaviours, and measured the acoustic characteristics of the calls using signal analysis tools in Matlab. Results We identified and measured acoustic characteristics of six different call types: courtship, landing, nest building, nest relief, jumping, and chick begging calls. Five of these call types were linked to distinctive breeding behaviours. Vocal signalling occurred between the male and female, and between parents and offspring. Males showed higher vocal activity than females and used a larger repertoire of calls. The courtship call was the most common call type in both sexes. These calls also differed acoustically between the sexes; male calls were longer in duration than female calls (617 ms versus 323 ms) and had wider bandwidth (763 Hz versus 473 Hz). Conclusion Great Cormorants use vocal communication for social interactions. Males were vocally more active and had a larger repertoire of calls than females, and calls differed between the sexes. Calls of males also differed individually and could, therefore, function for individual recognition in this species.Peer reviewe

Single-click beam patterns suggest dynamic changes to the field of view of echolocating Atlantic Spotted Dolphins (Stenella frontalis) in the wild

The study was funded by frame grants from the Danish Natural Science Foundation to P.T.M. and M.W., and by the National Oceanographic Partnership Programme via a research agreement between La Laguna University (N.A.d.S.) and the Woods Hole Oceanographic Institution (M.J.). F.H.J. was supported by the Danish Council for Independent Research | Natural Sciences, and is currently funded by a postdoctoral fellowship from the Carlsberg FoundationEcholocating animals exercise an extensive control over the spectral and temporal properties of their biosonar signals to facilitate perception of their actively generated auditory scene when homing in on prey. The intensity and directionality of the biosonar beam defines the field of view of echolocating animals by affecting the acoustic detection range and angular coverage. However, the spatial relationship between an echolocating predator and its prey changes rapidly, resulting in different biosonar requirements throughout prey pursuit and capture. Here, we measured single-click beam patterns using a parametric fit procedure to test whether free-ranging Atlantic spotted dolphins (Stenella frontalis) modify their biosonar beam width. We recorded echolocation clicks using a linear array of receivers and estimated the beam width of individual clicks using a parametric spectral fit, cross-validated with well-established composite beam pattern estimates. The dolphins apparently increased the biosonar beam width, to a large degree without changing the signal frequency, when they approached the recording array. This is comparable to bats that also expand their field of view during prey capture, but achieve this by decreasing biosonar frequency. This behaviour may serve to decrease the risk that rapid escape movements of prey take them outside the biosonar beam of the predator. It is likely that shared sensory requirements have resulted in bats and toothed whales expanding their acoustic field of view at close range to increase the likelihood of successfully acquiring prey using echolocation, representing a case of convergent evolution of echolocation behaviour between these two taxa.PostprintPeer reviewe

The common murre (Uria aalge), an auk seabird, reacts to underwater sound

Author Posting. © Acoustical Society of America, 2020. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 147(6), (2020): 4069, doi:10.1121/10.0001400.Marine mammals have fine-tuned hearing abilities, which makes them vulnerable to human-induced sounds from shipping, sonars, pile drivers, and air guns. Many species of marine birds, such as penguins, auks, and cormorants, find their food underwater where light is often limited, suggesting sound detection may play a vital role. Yet, for most marine birds, it is unknown whether they are using, and can thereby be affected by, underwater sound. The authors conducted a series of playback experiments to test whether Alcid seabirds responded to and were disrupted by, underwater sound. Underwater broadband sound bursts and mid-frequency naval 53 C sonar signals were presented to two common murres (Uria aalge) in a quiet pool. The received sound pressure levels varied from 110 to 137 dB re 1 μPa. Both murres showed consistent reactions to sounds of all intensities, as compared to no reactions during control trials. For one of the birds, there was a clearly graded response, so that more responses were found at higher received levels. The authors' findings indicate that common murres may be affected by, and therefore potentially also vulnerable to, underwater noise. The effect of man-made noise on murres, and possibly other marine birds, requires more thorough consideration.This project was funded by the U. S. Navy's Living Marine Resources Program (BAA N39433015R7203) and Woods Hole Oceanographic Institution. Birds were loaned from Copenhagen Zoo. Work was conducted under permission from the WHOI Institutional Animal Care and Use Committee, and animal permit to University of Southern Denmark No. 2300-50120-00003-09 from the Danish Ministry of Food and Agriculture. Statistical analysis was assisted by Simeon Smeele (MPI Konstanz, Germany) and Owen Jones (University of Southern Denmark).2020-12-2