Environmental concern about the potential impact of anthropogenic sounds on aquatic life has spar... more Environmental concern about the potential impact of anthropogenic sounds on aquatic life has sparked increased interest in marine bioacoustics. Experiments with live organisms are difficult to conduct and require considerable resources. Computerize numerical modelling is economical, reduces the need to expose live animals, and increases our understanding of bioacoustic interactions. Computer models should always be validated by comparing their simulations against results gleaned from live organisms. We investigated toothed whale biosonar by developing a numerical model that simulates the vibroacoustic functions of the biosonar apparatus (Krysl et al. 2008). In order to validate this approach, we used a vibroacoustic finite element model to recreate sound production and acoustic beam formation in the bottlenose dolphin (Tursiops truncatus). The model is constructed from live and post-mortem dolphin CT scans, tissue property measurements, and custom software. The right and left dorsal bursae were assumed to be the sound sources (Cranford 1988, 1992). This model confirms several hypotheses from previous studies: (1) the shape of the skull plays a role in the formation of the sound beam; (2) the melon has a significant capacity to focus the transmitted beam; (3) focusing the sound beam apparently happens in a series of stages that include contributions from the skull, nasal diverticula, melon, and connective tissue structures. An unexpected result is that adjustments to the focus and direction of the sound beam can result from small (millimetre scale) changes in the relative position of the anterior and posterior bursa within each sound generation complex. A comparison of our results with those from live dolphin psychoacoustic experiments (Au et al. 1986) supports validation of our vibroacoustic model.
Advances in Experimental Medicine and Biology, 2016
In 1974, Norris and Harvey published an experimental study of sound transmission into the head of... more In 1974, Norris and Harvey published an experimental study of sound transmission into the head of the bottlenose dolphin. We used this rare source of data to validate our Vibroacoustic Toolkit, an array of numerical modeling simulation tools. Norris and Harvey provided measurements of received sound pressure in various locations within the dolphin's head from a sound source that was moved around the outside of the head. Our toolkit was used to predict the curves of pressure with the best-guess input data (material properties, transducer and hydrophone locations, and geometry of the animal's head). In addition, we performed a series of sensitivity analyses (SAs). SA is concerned with understanding how input changes to the model influence the outputs. SA can enhance understanding of a complex model by finding and analyzing unexpected model behavior, discriminating which inputs have a dominant effect on particular outputs, exploring how inputs combine to affect outputs, and gaining insight as to what additional information improves the model's ability to predict. Even when a computational model does not adequately reproduce the behavior of a physical system, its sensitivities may be useful for developing inferences about key features of the physical system. Our findings may become a valuable source of information for modeling the interactions between sound and anatomy.
Advances in Experimental Medicine and Biology, 2016
The head-related transfer function (HRTF) is an important descriptor of spatial sound field recep... more The head-related transfer function (HRTF) is an important descriptor of spatial sound field reception by the listener. In this study, we computed the HRTF of the common dolphin Delphinus delphis. The received sound pressure level at various locations within the acoustic fats of the internal pinna near the surface of the tympanoperiotic complex (TPC) was calculated for planar incident waves directed toward the animal. The relative amplitude of the received pressure versus the incident pressure was the representation of the HRTF from the point of view of the animal. It is of interest that (1) different locations on the surface of the TPC resulted in different HRTFs, (2) the HRTFs for the left and right ears were slightly asymmetric, and (3) the locations of the peaks of the HRTF depended on the frequency of the incident wave.
A number of mass strandings of beaked whales have in recent decades been temporally and spatially... more A number of mass strandings of beaked whales have in recent decades been temporally and spatially coincident with military activities involving the use of midrange sonar. The social behaviour of beaked whales is poorly known, it can be inferred from strandings and some evidence of at-sea sightings. It is believed that some beaked whale species have social organisation at some scale; however most strandings are of individuals, suggesting that they spend at least some part of their life alone. Thus, the occurrence of unusual mass strandings of beaked whales is of particular importance. In contrast to some earlier reports, the most deleterious effect that sonar may have on beaked whales may not be trauma to the auditory system as a direct result of ensonification. Evidence now suggests that the most serious effect is the evolution of gas bubbles in tissues, driven by behaviourally altered dive profiles (e.g. extended surface intervals) or directly from ensonification. It has been predi...
Book AbstractDolphin researchers have collected an impressive amount of data over the last twenty... more Book AbstractDolphin researchers have collected an impressive amount of data over the last twenty years, thanks to advances in technology for monitoring, recording, and analyzing dolphin behavior as well as increasing interest in exploring and modeling dolphins’ cognitive capacities. This volume offers a comprehensive reference to the latest research on dolphin communication and cognition, reporting on findings from both the laboratory and the field. The contributors review a wide range of topics, including vocalization, abstract reasoning abilities, imitation and learning, social cognition, echolocation, and ethical issues in working with cetaceans.The book begins by examining the dolphin brain and its evolution, the anatomy of its unique sound production and reception systems, and its sensory abilities. It next treats communication, reviewing the complexity of dolphins’ vocalization, and then describes research on cognition, from both experimental and developmental perspectives. F...
Advances in Experimental Medicine and Biology, 2016
Odontocete ear complexes or tympanoperiotic complexes (TPCs) were compared for asymmetry. Left an... more Odontocete ear complexes or tympanoperiotic complexes (TPCs) were compared for asymmetry. Left and right TPCs were collected from one long-beaked common dolphin (Delphinus capensis) and one Amazon River dolphin (Inia geoffrensis). Asymmetry was assessed by volumetric comparisons of left and right TPCs and by visual comparison of superimposed models of the right TPC to a reflected mirror image of the left TPC. Kolmogorov-Smirnov tests were performed to compare the resonant frequencies of the TPCs as calculated by vibrational analysis. All analyses found slight differences between TPCs from the same specimen in contrast to the directional asymmetry in the nasal region of odontocete skulls.
<p>Some display transparency has been applied to the squamosal bone so that the tympanic bu... more <p>Some display transparency has been applied to the squamosal bone so that the tympanic bulla and the dense bony ossifications or “anchors” become visible. Bony skull components that are visible in this orientation are the: occipital (yellow), parietal (white), frontal (red), maxillary (green), squamosal (magenta), tympanic bullae (green), and the “anchors” (white). The dense bony anchors fan out dorsolaterally within the squamosal bones of the skull (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116222#pone.0116222.g002" target="_blank">Fig. 2</a>). In this lateral view, the adjacent periotic bones are not visible because they are obscured by the anchors and tympanic bulla.</p
The Journal of the Acoustical Society of America, 2004
The melon of odontocetes has been hypothesized to be a focusing body that channels echolocation s... more The melon of odontocetes has been hypothesized to be a focusing body that channels echolocation signals produced within the nasal region of the animal&amp;amp;amp;amp;#39;s head into the water. The acoustic field of two echolocating harbor porpoises (Phocoena phocoena) was measured at the melon&amp;amp;amp;amp;#39;s surface with an array of four broadband hydrophones embedded in suction cups. The clicks detected by each
The Journal of the Acoustical Society of America, 2012
Bottlenose dolphins (Tursiops truncatus) wore opaque suction cups over their eyes while stationin... more Bottlenose dolphins (Tursiops truncatus) wore opaque suction cups over their eyes while stationing behind an acoustically opaque door. This put the dolphins in a known position and orientation. When the door opened, the dolphin clicked to detect targets. Trainers specified that Dolphin S emit a whistle if the target was a 7.5 cm water filled sphere, or a pulse burst if the target was a rock. S remained quiet if there was no target. Dolphin B whistled for the sphere. She remained quiet for rock and for no target. Thus, S had to choose between three different responses, whistle, pulse burst, or remain quiet. B had to choose between two different responses, whistle or remain quiet. S gave correct vocal responses averaging 114 ms after her last echolocation click (range 182 ms before and 219 ms after the last click). Average response for B was 21 ms before her last echolocation click (range 250 ms before and 95 ms after the last click in the train). More often than not, B began her whistle response before her echolocation train ended. The findings suggest separate neural pathways for generation of response vocalizations as opposed to echolocation clicks.
Summary Finite element analysis on CT-scanned cetacean heads can be used to determine the path of... more Summary Finite element analysis on CT-scanned cetacean heads can be used to determine the path of sounds through the head. These cetacean sound paths are different from those of land mammals, and, surprisingly, they also differ depending on the frequency of the sound. Using these, it was possible to model audiogram for mysticetes and compare the methods of hearing between cetacean taxa.
Environmental concern about the potential impact of anthropogenic sounds on aquatic life has spar... more Environmental concern about the potential impact of anthropogenic sounds on aquatic life has sparked increased interest in marine bioacoustics. Experiments with live organisms are difficult to conduct and require considerable resources. Computerize numerical modelling is economical, reduces the need to expose live animals, and increases our understanding of bioacoustic interactions. Computer models should always be validated by comparing their simulations against results gleaned from live organisms. We investigated toothed whale biosonar by developing a numerical model that simulates the vibroacoustic functions of the biosonar apparatus (Krysl et al. 2008). In order to validate this approach, we used a vibroacoustic finite element model to recreate sound production and acoustic beam formation in the bottlenose dolphin (Tursiops truncatus). The model is constructed from live and post-mortem dolphin CT scans, tissue property measurements, and custom software. The right and left dorsal bursae were assumed to be the sound sources (Cranford 1988, 1992). This model confirms several hypotheses from previous studies: (1) the shape of the skull plays a role in the formation of the sound beam; (2) the melon has a significant capacity to focus the transmitted beam; (3) focusing the sound beam apparently happens in a series of stages that include contributions from the skull, nasal diverticula, melon, and connective tissue structures. An unexpected result is that adjustments to the focus and direction of the sound beam can result from small (millimetre scale) changes in the relative position of the anterior and posterior bursa within each sound generation complex. A comparison of our results with those from live dolphin psychoacoustic experiments (Au et al. 1986) supports validation of our vibroacoustic model.
Advances in Experimental Medicine and Biology, 2016
In 1974, Norris and Harvey published an experimental study of sound transmission into the head of... more In 1974, Norris and Harvey published an experimental study of sound transmission into the head of the bottlenose dolphin. We used this rare source of data to validate our Vibroacoustic Toolkit, an array of numerical modeling simulation tools. Norris and Harvey provided measurements of received sound pressure in various locations within the dolphin&amp;amp;amp;amp;#39;s head from a sound source that was moved around the outside of the head. Our toolkit was used to predict the curves of pressure with the best-guess input data (material properties, transducer and hydrophone locations, and geometry of the animal&amp;amp;amp;amp;#39;s head). In addition, we performed a series of sensitivity analyses (SAs). SA is concerned with understanding how input changes to the model influence the outputs. SA can enhance understanding of a complex model by finding and analyzing unexpected model behavior, discriminating which inputs have a dominant effect on particular outputs, exploring how inputs combine to affect outputs, and gaining insight as to what additional information improves the model&amp;amp;amp;amp;#39;s ability to predict. Even when a computational model does not adequately reproduce the behavior of a physical system, its sensitivities may be useful for developing inferences about key features of the physical system. Our findings may become a valuable source of information for modeling the interactions between sound and anatomy.
Advances in Experimental Medicine and Biology, 2016
The head-related transfer function (HRTF) is an important descriptor of spatial sound field recep... more The head-related transfer function (HRTF) is an important descriptor of spatial sound field reception by the listener. In this study, we computed the HRTF of the common dolphin Delphinus delphis. The received sound pressure level at various locations within the acoustic fats of the internal pinna near the surface of the tympanoperiotic complex (TPC) was calculated for planar incident waves directed toward the animal. The relative amplitude of the received pressure versus the incident pressure was the representation of the HRTF from the point of view of the animal. It is of interest that (1) different locations on the surface of the TPC resulted in different HRTFs, (2) the HRTFs for the left and right ears were slightly asymmetric, and (3) the locations of the peaks of the HRTF depended on the frequency of the incident wave.
A number of mass strandings of beaked whales have in recent decades been temporally and spatially... more A number of mass strandings of beaked whales have in recent decades been temporally and spatially coincident with military activities involving the use of midrange sonar. The social behaviour of beaked whales is poorly known, it can be inferred from strandings and some evidence of at-sea sightings. It is believed that some beaked whale species have social organisation at some scale; however most strandings are of individuals, suggesting that they spend at least some part of their life alone. Thus, the occurrence of unusual mass strandings of beaked whales is of particular importance. In contrast to some earlier reports, the most deleterious effect that sonar may have on beaked whales may not be trauma to the auditory system as a direct result of ensonification. Evidence now suggests that the most serious effect is the evolution of gas bubbles in tissues, driven by behaviourally altered dive profiles (e.g. extended surface intervals) or directly from ensonification. It has been predi...
Book AbstractDolphin researchers have collected an impressive amount of data over the last twenty... more Book AbstractDolphin researchers have collected an impressive amount of data over the last twenty years, thanks to advances in technology for monitoring, recording, and analyzing dolphin behavior as well as increasing interest in exploring and modeling dolphins’ cognitive capacities. This volume offers a comprehensive reference to the latest research on dolphin communication and cognition, reporting on findings from both the laboratory and the field. The contributors review a wide range of topics, including vocalization, abstract reasoning abilities, imitation and learning, social cognition, echolocation, and ethical issues in working with cetaceans.The book begins by examining the dolphin brain and its evolution, the anatomy of its unique sound production and reception systems, and its sensory abilities. It next treats communication, reviewing the complexity of dolphins’ vocalization, and then describes research on cognition, from both experimental and developmental perspectives. F...
Advances in Experimental Medicine and Biology, 2016
Odontocete ear complexes or tympanoperiotic complexes (TPCs) were compared for asymmetry. Left an... more Odontocete ear complexes or tympanoperiotic complexes (TPCs) were compared for asymmetry. Left and right TPCs were collected from one long-beaked common dolphin (Delphinus capensis) and one Amazon River dolphin (Inia geoffrensis). Asymmetry was assessed by volumetric comparisons of left and right TPCs and by visual comparison of superimposed models of the right TPC to a reflected mirror image of the left TPC. Kolmogorov-Smirnov tests were performed to compare the resonant frequencies of the TPCs as calculated by vibrational analysis. All analyses found slight differences between TPCs from the same specimen in contrast to the directional asymmetry in the nasal region of odontocete skulls.
<p>Some display transparency has been applied to the squamosal bone so that the tympanic bu... more <p>Some display transparency has been applied to the squamosal bone so that the tympanic bulla and the dense bony ossifications or “anchors” become visible. Bony skull components that are visible in this orientation are the: occipital (yellow), parietal (white), frontal (red), maxillary (green), squamosal (magenta), tympanic bullae (green), and the “anchors” (white). The dense bony anchors fan out dorsolaterally within the squamosal bones of the skull (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116222#pone.0116222.g002" target="_blank">Fig. 2</a>). In this lateral view, the adjacent periotic bones are not visible because they are obscured by the anchors and tympanic bulla.</p
The Journal of the Acoustical Society of America, 2004
The melon of odontocetes has been hypothesized to be a focusing body that channels echolocation s... more The melon of odontocetes has been hypothesized to be a focusing body that channels echolocation signals produced within the nasal region of the animal&amp;amp;amp;amp;#39;s head into the water. The acoustic field of two echolocating harbor porpoises (Phocoena phocoena) was measured at the melon&amp;amp;amp;amp;#39;s surface with an array of four broadband hydrophones embedded in suction cups. The clicks detected by each
The Journal of the Acoustical Society of America, 2012
Bottlenose dolphins (Tursiops truncatus) wore opaque suction cups over their eyes while stationin... more Bottlenose dolphins (Tursiops truncatus) wore opaque suction cups over their eyes while stationing behind an acoustically opaque door. This put the dolphins in a known position and orientation. When the door opened, the dolphin clicked to detect targets. Trainers specified that Dolphin S emit a whistle if the target was a 7.5 cm water filled sphere, or a pulse burst if the target was a rock. S remained quiet if there was no target. Dolphin B whistled for the sphere. She remained quiet for rock and for no target. Thus, S had to choose between three different responses, whistle, pulse burst, or remain quiet. B had to choose between two different responses, whistle or remain quiet. S gave correct vocal responses averaging 114 ms after her last echolocation click (range 182 ms before and 219 ms after the last click). Average response for B was 21 ms before her last echolocation click (range 250 ms before and 95 ms after the last click in the train). More often than not, B began her whistle response before her echolocation train ended. The findings suggest separate neural pathways for generation of response vocalizations as opposed to echolocation clicks.
Summary Finite element analysis on CT-scanned cetacean heads can be used to determine the path of... more Summary Finite element analysis on CT-scanned cetacean heads can be used to determine the path of sounds through the head. These cetacean sound paths are different from those of land mammals, and, surprisingly, they also differ depending on the frequency of the sound. Using these, it was possible to model audiogram for mysticetes and compare the methods of hearing between cetacean taxa.
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