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  • Acoustical Society of America (ASA)  (33)
  • Wahlberg, Magnus  (33)
  • 1
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2002
    In:  The Journal of the Acoustical Society of America Vol. 112, No. 6 ( 2002-12-01), p. 3046-3052
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 112, No. 6 ( 2002-12-01), p. 3046-3052
    Abstract: 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’s 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.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2002
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  • 2
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 133, No. 5 ( 2013-05-01), p. 3135-3144
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 133, No. 5 ( 2013-05-01), p. 3135-3144
    Abstract: Sperm whales produce different click types for echolocation and communication. Usual clicks and buzzes appear to be used primarily in foraging while codas are thought to function in social communication. The function of slow clicks is less clear, but they appear to be produced by males at higher latitudes, where they primarily forage solitarily, and on the breeding grounds, where they roam between groups of females. Here the behavioral context in which these vocalizations are produced and the function they may serve was investigated. Ninety-nine hours of acoustic and diving data were analyzed from sound recording tags on six male sperm whales in Northern Norway. The 755 slow clicks detected were produced by tagged animals at the surface (52%), ascending from a dive (37%), and during the bottom phase (11%), but never during the descent. Slow clicks were not associated with the production of buzzes, other echolocation clicks, or fast maneuvering that would indicate foraging. Some slow clicks were emitted in seemingly repetitive temporal patterns supporting the hypothesis that the function for slow clicks on the feeding grounds is long range communication between males, possibly relaying information about individual identity or behavioral states.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
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  • 3
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3361-3361
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3361-3361
    Abstract: Porpoise echolocation has been studied in target detection experiments using stationed animals and steel spheres as targets, but little is known about the acoustic behavior of free swimming porpoises as they echolocate for prey. Here we used archival tags (modified Dtags) recording audio (400 kHz, 16-bit stereo sampling rate) and animal movements (depth, heading, 3D pitch and roll, and acceleration) to study echolocation in trained porpoises catching fish. The prey capture experiments were conducted with and without suction cups covering the porpoises' eyes. Without the eye cups, the porpoises could use both echolocation and vision to locate and ingest their prey, but with eye cups they could use only echolocation. Our data show that time to prey capture is about 27% greater with eye cups (T-test, p & lt;0.01). They also allow us to describe and compare prey capture in the two experimental conditions, including analysis of the animals' detailed movements and echolocation behavior leading up to and following prey capture events.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
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  • 4
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3773-3773
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3773-3773
    Abstract: For the first time, the beam structure of single harbour porpoise echolocation clicks was simultaneously measured in both the vertical and horizontal plane. Echolocation clicks of a stationed animal and free-swimming animals catching fish were recorded with a “plus-shaped” array consisting of 16 hydrophones. The -3 dB beam width in the horizontal and vertical planes is in most cases similar to what has been previously measured by Au et al. (1999). However, individual clicks are sometimes broader or narrower than what has been previously reported. This may be caused by either voluntary control of the animal's beam width, or it may be a secondary effect of variations in intensity and air content within the sound production system.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
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  • 5
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2017
    In:  The Journal of the Acoustical Society of America Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3667-3667
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 141, No. 5_Supplement ( 2017-05-01), p. 3667-3667
    Abstract: Little is known about underwater hearing abilities of diving birds. To help fill this gap we measured audiograms of cormorants (Phalacrocorax carbo) using two different methods. Wild-caught cormorant fledglings were anesthetized and their auditory brainstem responses (ABR) to clicks and tone bursts were measured; first in an anechoic box in air and then in a large water-filled tank with their head and neck submerged. In addition, audiograms were obtained from two adult cormorants using the psychophysical method of constant stimuli both in air and underwater. The shape of audiograms obtained from in-air ABR-recordings was similar to that reported for birds of similar size. The highest sensitivity in air was found at about 2 kHz, while the most sensitive response was at about 1 kHz underwater. In general, the audiograms obtained from psychophysical measurements were similar to the ABR audiograms but had much higher sensitivity than the ABR audiograms. The results from both methods suggest that cormorants have rather poor in-air hearing compared to similar-sized birds. Their underwater hearing sensitivity, however, is higher than what would have been expected for purely air-adapted ears, and it is likely that cormorants use their underwater hearing abilities during foraging dives.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2017
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  • 6
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2006
    In:  The Journal of the Acoustical Society of America Vol. 119, No. 5_Supplement ( 2006-05-01), p. 3372-3373
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 119, No. 5_Supplement ( 2006-05-01), p. 3372-3373
    Abstract: Directivity is an important determinant of animal sonar performance but difficult to assess for large, free-ranging species. Recent field studies of sperm whales indicate usual clicks to be quite directional [directivity index: 27 dB at a transmitting cross section to wavelength ratio (2a/wl) of 8], with indications of even narrower beams. To obtain better measures of directivity, a fiber-optically linked, linear hydrophone array with up to ten receivers, spaced 50 m apart, has been designed. The array can be deployed to depths of 1 km and incorporates a transmitting transducer. The array was deployed off Andenes, Norway, in July 2003, 2004, and 2005. On five occasions, transmissions of short broadband pulses (peaking at 14 kHz, SL 135 dB re: 1 Pa) apparently induced sperm whales at ranges of about 2 km to train their sound beams towards the transmitter and lock them there. This implies beam-steering from the whales’ auditory system, having a high auditory directionality, and detection capability of signals at 65 dB re: 1 Pa. It resulted in a high yield of on-axis recordings with maximum directivity indices of 39 dB, incompatible with plane piston radiation at 2a/wl ratio of 8.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2006
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  • 7
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 1999
    In:  The Journal of the Acoustical Society of America Vol. 105, No. 2_Supplement ( 1999-02-01), p. 1318-1318
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 105, No. 2_Supplement ( 1999-02-01), p. 1318-1318
    Abstract: Source positioning accuracy of a large-aperture (1 km) hydrophone array was investigated, using 2-D and 3-D algorithms. The array was used for positioning and SL determination of sperm whales off the coast of Northern Norway during the summers of 1997 and 1998 (see Mo/hl, this volume). Positioning accuracy is dependent on mainly four factors: (1) positioning accuracy of the hydrophones, (2) variation in sound velocity of the medium, (3) inaccuracies in the measurements of the time-of-arrival differences, and (4) choice of algorithm (errors associated with geometric over-simplification). Errors introduced by the factors (1) and (3) had small effects compared with errors introduced by the factors (2) and (4). The total estimated error varied considerably in different areas covered by the array and for different array configurations. Sound velocity showed only modest variation with depth, except for a −0.2-m/s per meter gradient in the 0–100-m depth interval caused by summer heating of the surface water. For a sound source close to the surface, this sound velocity gradient causes a shadow zone starting some hundred meters from the source. Such a shadow zone may lead to underestimates of source level estimates from 2-D algorithms. [Work supported by the Danish National Research Foundation.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1999
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  • 8
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3773-3773
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3773-3773
    Abstract: Harbour porpoises (Phocoena phocoena) emit ultrasonic (130 kHz) clicks with a stereotyped source parameters for echolocation and communication. Recently it was observed that the first days of living, a neonate harbour porpoise emitted contact calls of much a much lower frequency emphasis, around a few kHz. The echolocation clicks produced by the calf significantly differed in duration and band width during the first four months postpartum. The acoustic signals from harbour porpoise calves are ideal for automated detection and therefore as a tool in population studies of this species. Both hydrophone array systems towed from boats, and automated click detectors (such as T-PODs) may incorporate routines for automated detection of young calves. These findings may have a large potential for facilitating biologists in gathering important biological data from this otherwise very difficult-to-study species of marine mammals.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
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  • 9
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4 ( 2011-10-01), p. 2263-2274
    Abstract: The Indian Ocean and Atlantic bottlenose dolphins (Tursiops aduncus and Tursiops truncatus) are among the best studied echolocating toothed whales. However, almost all echolocation studies on bottlenose dolphins have been made with captive animals, and the echolocation signals of free-ranging animals have not been quantified. Here, biosonar source parameters from wild T. aduncus and T. truncatus were measured with linear three- and four-hydrophone arrays in four geographic locations. The two species had similar source parameters, with source levels of 177–228 dB re 1 μPa peak to peak, click durations of 8–72 μs, centroid frequencies of 33–109 kHz and rms bandwidths between 23 and 54 kHz. T. aduncus clicks had a higher frequency emphasis than T. truncatus. The transmission directionality index was up to 3 dB higher for T. aduncus (29 dB) as compared to T. truncatus (26 dB). The high directionality of T. aduncus does not appear to be only a physical consequence of a higher frequency emphasis in clicks, but may also be caused by differences in the internal properties of the sound production system.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
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  • 10
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2020
    In:  The Journal of the Acoustical Society of America Vol. 147, No. 6 ( 2020-06-01), p. 4069-4074
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 147, No. 6 ( 2020-06-01), p. 4069-4074
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2020
    detail.hit.zdb_id: 1461063-2
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