RESUMEN
Dolphins use their biosonar to discriminate objects with different features through the returning echoes. Cross-modal matching experiments were conducted with a resident bottlenose dolphin (Tursiops aduncus). Four types of objects composed of different materials (water-filled PVC pipes, air-filled PVC pipes, foam ball arrays, and PVC pipes wrapped in closed-cell foam) were used in the experiments, respectively. The size and position of the objects remained the same in each case. The data collected in the experiment showed that the dolphin's matching accuracy was significantly different across the cases. To gain insight into the underlying mechanism in the experiments, we used finite element methods to construct two-dimensional target detection models of an echolocating dolphin in the vertical plane, based on computed tomography scan data. The acoustic processes of the click's interaction with the objects and the surrounding media in the four cases were simulated and compared. The simulation results provide some possible explanations for why the dolphin performed differently when discriminating the objects that only differed in material composition in the previous matching experiments.
Asunto(s)
Delfines/fisiología , Ecolocación , Acústica , Algoritmos , Animales , Delfín Mular , Análisis de Datos , Masculino , Modelos TeóricosRESUMEN
Bio-logging devices are advancing the understanding of marine animal behavior, but linking sound production and behavior of individual baleen whales is still unreliable. Tag placement potentially within the near field of the sound source creates uncertainty about how tagged animal sounds will register on recorders. This study used data from a tagged singing humpback whale to evaluate this question of how sound levels present on a tag when calls are produced by a tagged animal. Root-mean-square (rms) received levels (RLs) of song units ranged from 112 to 164 dB re 1 µPa rms, with some, but not all, of the lower frequency units registering on the tag's 800 Hz accelerometer sensor. Fifty-nine percent of recorded units measured lower acoustic RLs than previously reported source levels for humpback song, but signal-to-noise ratios (SNRs) were 30-45 dB during periods of the dive with low noise. This research highlights that tag RL does not alone predict caller identity, argues for higher SNR thresholds if using SNR to inform decisions about the source of a call, and provides a baseline for future research identifying diagnostic properties of tagged animal calls in cetacean bioacoustic tag datasets.
Asunto(s)
Yubarta , Canto , Acústica , Animales , Sonido , Espectrografía del Sonido , Vocalización AnimalRESUMEN
Echolocation signals emitted by odontocetes can be roughly classified into three broad categories: broadband echolocation signals, narrowband high-frequency echolocation signals, and frequency modulated clicks. Previous measurements of broadband echolocation signal propagation in the bottlenose dolphin (Tursiops truncatus) did not find any evidence of focusing as the signals travel from the near-field to far-field. Finite element analysis (FEA) of high-resolution computed tomography scan data was used to examine signal propagation of broadband echolocation signals of dolphins and narrowband echolocation signals of porpoises. The FEA results were used to simulate the propagation of clicks from phonic lips, traveling through the forehead, and finally transmission into the water. Biosonar beam formation in the near-field and far-field, including the amplitude contours for the two species, was determined. The finite element model result for the simulated amplitude contour in the horizontal plane was consistent with prior direct measurement results for Tursiops, validating the model. Furthermore, the simulated far-field transmission beam patterns in both the vertical and horizontal planes were also qualitatively consistent with results measured from live animals. This study indicates that there is no evidence of convergence for either Tursiops or Phocoena as the sound propagates from the near-field to the far-field.
Asunto(s)
Delfín Mular , Ecolocación , Phocoena , Acústica , Animales , SonidoRESUMEN
Acoustic backscatter measurements were conducted on a stationary harbor porpoise (Phocoena phocoena) under controlled conditions. The measurements were made with the porpoise in the broadside aspect using three different types of signals: (1) a 475 µs linear frequency-modulated (FM) pulse with a frequency range from 23 to 160 kHz; (2) a simulated bottlenose dolphin (Tursiops "truncates") click with a peak frequency of 120 kHz; and (3) a simulated killer whale (Orcinus orca) click with a peak frequency of 60 kHz. The measurement with the FM pulse indicated that the mean target strength at the broadside aspect decreased from -26 to -50 dB as the frequency increased from 23 to 120 kHz in a nearly linear fashion (on a logarithm plot). Target strength variation with frequency was similar to a previous backscatter measurement on a bottlenose dolphin over a comparable frequency range (23-80 kHz). The porpoise seems to be a stealth body with low backscatter properties. The target strength of the porpoise was also about 15-16 dB lower than that of the bottlenose dolphin. The difference in lung volume of the two species when expressed in dB was also approximately 15 dB.
Asunto(s)
Acústica , Phocoena/fisiología , Estimulación Acústica , Comunicación Animal , Animales , Masculino , Localización de Sonidos , Espectrografía del SonidoRESUMEN
Bottlenose dolphins project broadband echolocation signals for detecting and locating prey and predators, and for spatial orientation. There are many unknowns concerning the specifics of biosonar signal production and propagation in the head of dolphins and this manuscript represents an effort to address this topic. A two-dimensional finite element model was constructed using high resolution CT scan data. The model simulated the acoustic processes in the vertical plane of the biosonar signal emitted from the phonic lips and propagated into the water through the animal's head. The acoustic field on the animal's forehead and the farfield transmission beam pattern of the echolocating dolphin were determined. The simulation results and prior acoustic measurements were qualitatively extremely consistent. The role of the main structures on the sound propagation pathway such as the air sacs, melon, and connective tissue was investigated. Furthermore, an investigation of the driving force at the phonic lips for dolphins that emit broadband echolocation signals and porpoises that emit narrowband echolocation signals suggested that the driving force is different for the two types of biosonar. Finally, the results provide a visual understanding of the sound transmission in dolphin's biosonar.
Asunto(s)
Sacos Aéreos/diagnóstico por imagen , Sacos Aéreos/fisiología , Delfín Mular/fisiología , Ecolocación/fisiología , Análisis de Elementos Finitos , Vocalización Animal/fisiología , Animales , Espectrografía del Sonido/métodosRESUMEN
Sperm whales forage in the deep ocean, hunting for squid. An innovative approach for the study of sperm whale foraging behavior and habitat selection is reported in this letter. A DIDSON imaging sonar mounted on a profiler with a conductivity, temperature, and depth sensor was used to count and measure potential prey in the deep ocean during sperm whales' acoustical foraging encounters in Hawaii. Preliminary results show how this technique can be applied to the study of deep diving whale foraging and habitat selection. Sperm whales foraged where the density of prey decreased with depth and where the size of prey increased with depth.
Asunto(s)
Acústica , Conducta Predatoria , Cachalote , Vocalización Animal , Animales , Conducta Alimentaria/fisiología , Hawaii , Océanos y Mares , Conducta Predatoria/fisiología , Espectrografía del SonidoRESUMEN
A dual frequency identification sonar was used to estimate density and size of potential deep diving odontocetes' prey in deep sea scattering layers in Hawaii. Size distributions data showed a bimodal pattern, with a population of data above the 50 cm of length, possibly big squids, and a population of data below 50 cm, mainly micronekton. The number of animals bigger than 50 cm was correlated with the length of the peak of the frequency distribution. Data suggest that big predators, like squids that constitute prey for beaked, pilot, and sperm whales, are more likely to be found where they have better chance to find micronectonic prey.
RESUMEN
Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for detecting and locating prey and for spatial orientation. In this study, acoustic impedance values of tissues in the porpoise's head were calculated from computer tomography (CT) scan and the corresponding Hounsfield Units. A two-dimensional finite element model of the acoustic impedance was constructed based on CT scan data to simulate the acoustic propagation through the animal's head. The far field transmission beam pattern in the vertical plane and the waveforms of the receiving points around the forehead were compared with prior measurement results, the simulation results were qualitatively consistent with the measurement results. The role of the main structures in the head such as the air sacs, melon and skull in the acoustic propagation was investigated. The results showed that air sacs and skull are the major components to form the vertical beam. Additionally, both beam patterns and sound pressure of the sound waves through four positions deep inside the melon were demonstrated to show the role of the melon in the biosonar sound propagation processes in the vertical plane.
Asunto(s)
Acústica , Ecolocación , Cabeza/fisiología , Modelos Teóricos , Phocoena/fisiología , Vocalización Animal , Sacos Aéreos/anatomía & histología , Sacos Aéreos/fisiología , Animales , Simulación por Computador , Análisis de Elementos Finitos , Cabeza/anatomía & histología , Movimiento (Física) , Análisis Numérico Asistido por Computador , Phocoena/anatomía & histología , Presión , Cráneo/anatomía & histología , Cráneo/fisiología , Sonido , Espectrografía del Sonido , Factores de Tiempo , Tomografía Computarizada por Rayos XRESUMEN
Male humpback whales produce loud "songs" on the wintering grounds and some sing while escorting mother-calf pairs, exposing them to near-continuous sounds at close proximity. An Acousonde acoustic and movement recording tag deployed on a calf off Maui, Hawaii captured sounds produced by a singing male escort. Root-mean-square received levels ranged from 126 to 158 dB re 1 µPa. These levels represent rare direct measurements of sound to which a newly born humpback calf may be naturally exposed by a conspecific, and may provide a basis for informed decisions regarding anthropogenic sound levels projected near calves.
Asunto(s)
Yubarta , Acústica , Animales , Hawaii , Canto , Espectrografía del Sonido , Vocalización AnimalRESUMEN
Beaked and sperm whales are top predators living in the waters off the Kona coast of Hawai'i. Temporal and spatial analyses of the foraging activity of these two species were studied with passive acoustics techniques. Three passive acoustics recorders moored to the ocean floor were used to monitor the foraging activity of these whales in three locations along the Kona coast of the island of Hawaii. Data were analyzed using automatic detector/classification systems: M3R (Marine Mammal Monitoring on Navy Ranges), and custom-designed Matlab programs. The temporal variation in foraging activity was species-specific: beaked whales foraged more at night in the north, and more during the day-time off Kailua-Kona. No day-time/night-time preference was found in the southern end of the sampling range. Sperm whales foraged mainly at night in the north, but no day-time/night-time preference was observed off Kailua-Kona and in the south. A Generalized Linear Model was then applied to assess whether location and chlorophyll concentration affected the foraging activity of each species. Chlorophyll concentration and location influenced the foraging activity of both these species of deep-diving odontocetes.
RESUMEN
The biosonar signals of two free-swimming Atlantic bottlenose dolphins performing a complex sonar search for a bottom target in San Diego Bay were compared with the biosonar signals of a dolphin performing a target discrimination task in a net pen in the same bay. A bite-plate device carried by the free-swimming dolphins supported a hydrophone that extended directly in front of the dolphin. A biosonar measuring tool attached to the bite plate measured the outgoing biosonar signals while the dolphins conducted sonar searches. Each of the free-swimming dolphins used different biosonar search strategy in solving the problem and the dolphins' biosonar signals reflect the difference in strategy. The dolphin in the pen stationed in a hoop while echolocating on a target 6 m away and reported if the indentation on a spherical target was directed toward it. The signals were parameterized by determining the peak-to-peak source levels, source energy flux density, peak frequency, center frequency, root-mean-square (rms) bandwidth, rms duration, and the Q of the signals. Some parameters were similar for the free-swimming and stationary dolphins while some were significantly different, suggesting biosonar signals used by free-swimming animals may be different than signals used by dolphins in a pen.
Asunto(s)
Delfín Mular/fisiología , Delfín Mular/psicología , Ecolocación , Natación , Vocalización Animal , Acústica/instrumentación , Animales , Discriminación en Psicología , Masculino , Procesamiento de Señales Asistido por Computador , Espectrografía del Sonido , TransductoresRESUMEN
The relative role of the various structures in the head of the baiji (Lipotes vexillifer) is examined. A finite element approach was applied to numerically simulate the acoustic propagation through a dolphin's head to examine the relative role of the skull, air sacs, and melon in the formation of the biosonar beam in the vertical plane. The beam pattern obtained with the whole head in place is compared with the beam pattern when the air sac is removed and the other structures (skull and melon) are in place, with only the skull removed, and finally with only the melon removed. The beam pattern with the air sacs and skull intact and the melon removed closely resembled the beam pattern for the complete head, suggesting that the melon has a minor role in the formation of the beam. The beam pattern for the other two cases had very little resemblance to the beam pattern for the whole head. The air sacs seem to have a role of directing propagation of the signal toward the front and the skull prevents the sound propagating below the rostrum. The beam patterns along with a correlation analysis showed that the melon had only a slight influence on the shape and direction of the beam. The resultant beam exiting the head of the dolphin is the result of complex reflection processes within the head of the animal.
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Delfines/anatomía & histología , Delfines/fisiología , Ecolocación , Cabeza/anatomía & histología , Cabeza/fisiología , Vocalización Animal , Sacos Aéreos/anatomía & histología , Sacos Aéreos/fisiología , Animales , Simulación por Computador , Análisis de Elementos Finitos , Modelos Anatómicos , Análisis Numérico Asistido por Computador , Cráneo/anatomía & histología , Cráneo/fisiologíaRESUMEN
The radiated noise from a high-speed water-jet-propelled catamaran was measured for catamaran speeds of 12, 24, and 37 kn. The radiated noise increased with catamaran speed, although the shape of the noise spectrum was similar for all speeds and measuring hydrophone depth. The spectra peaked at ~200 Hz and dropped off continuously at higher frequencies. The radiated noise was 10-20 dB lower than noise from propeller-driven ships at comparable speeds. The combination of low radiated noise and high speed could be a factor in the detection and avoidance of water-jet-propelled ships by baleen whales.
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Navíos , Sonido , Agua , Hawaii , Espectrografía del SonidoRESUMEN
Automatic classification of fin, sei, and blue whale frequency modulated downsweeps has been a challenging task for bioacousticians. These calls overlap in frequency range and have similar time durations. The traditional spectrogram methodology, the Short Time Fourier Transform, tends to be ineffective because of the large temporal ambiguities needed to achieve the necessary frequency resolution to study the fine time-frequency (TF) structures. Spectrograms generated with the Pseudo Wigner-Ville Distribution (PWVD) provide much higher simultaneous TF resolution compared with the traditional method. The PWVD allows bioacousticians to study the fine TF structures of the sound, such as the instantaneous frequency, instantaneous bandwidth, contour slope, etc. These features set the foundation of identifying sounds that are usually considered difficult to discriminate using the traditional method. Wigner-Ville distribution of the baleen whale downsweeps showed distinguishable characteristics; for example, the TF contour of fin and sei whales exhibited concave and convex shapes, which have never been reported in the literature. A Support Vector Machine classifier was trained and tested based on the parameters extracted from the PWVD.
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Acústica , Balaenoptera/fisiología , Monitoreo del Ambiente/métodos , Procesamiento de Señales Asistido por Computador , Vocalización Animal , Algoritmos , Animales , Balaenoptera/clasificación , Ballena de Aleta/clasificación , Ballena de Aleta/fisiología , Análisis de Fourier , Movimiento (Física) , Reconocimiento de Normas Patrones Automatizadas , Sonido , Espectrografía del Sonido , Especificidad de la Especie , Máquina de Vectores de Soporte , Factores de Tiempo , Vocalización Animal/clasificaciónRESUMEN
The temporal occurrence of deep diving cetaceans in the Josephine Seamount High Seas Marine Protected Area (JSHSMPA), south-west Portugal, was monitored using a passive acoustic recorder. The recorder was deployed on 13 May 2010 at a depth of 814 m during the North Atlantic Treaty Organization Centre for Maritime Research and Experimentation cruise "Sirena10" and recovered on 6 June 2010. The recorder was programmed to record 40 s of data every 2 min. Acoustic data analysis, for the detection and classification of echolocation clicks, was performed using automatic detector/classification systems: M3R (Marine Mammal Monitoring on Navy Ranges), a custom matlab program, and an operator-supervised custom matlab program to assess the classification performance of the detector/classification systems. M3R CS-SVM algorithm contains templates to detect beaked whales, sperm whales, blackfish (pilot and false killer whales), and Risso's dolphins. The detections of each group of odontocetes was monitored as a function of time. Blackfish and Risso's dolphins were detected every day, while beaked whales and sperm whales were detected almost every day. The hourly distribution of detections reveals that blackfish and Risso's dolphins were more active at night, while beaked whales and sperm whales were more active during daylight hours.
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Acústica , Cetáceos/clasificación , Cetáceos/fisiología , Ecolocación/clasificación , Monitoreo del Ambiente/métodos , Vocalización Animal/clasificación , Algoritmos , Animales , Océano Atlántico , Ritmo Circadiano , Movimiento (Física) , Procesamiento de Señales Asistido por Computador , Sonido , Espectrografía del Sonido , Especificidad de la Especie , Factores de TiempoRESUMEN
The reconstruction of the acoustic properties of a neonate finless porpoise's head was performed using X-ray computed tomography (CT). The head of the deceased neonate porpoise was also segmented across the body axis and cut into slices. The averaged sound velocity and density were measured, and the Hounsfield units (HU) of the corresponding slices were obtained from computed tomography scanning. A regression analysis was employed to show the linear relationships between the Hounsfield unit and both sound velocity and density of samples. Furthermore, the CT imaging data were used to compare the HU value, sound velocity, density and acoustic characteristic impedance of the main tissues in the porpoise's head. The results showed that the linear relationships between HU and both sound velocity and density were qualitatively consistent with previous studies on Indo-pacific humpback dolphins and Cuvier's beaked whales. However, there was no significant increase of the sound velocity and acoustic impedance from the inner core to the outer layer in this neonate finless porpoise's melon.
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Acústica , Cabeza/diagnóstico por imagen , Marsopas , Tomografía Computarizada por Rayos X , Animales , Animales Recién Nacidos , Imagenología TridimensionalRESUMEN
Killer whales project short broadband biosonar clicks. The broadband nature of the clicks provides good temporal resolution of echo highlights and allows for the discriminations of salmon prey. The echoes contain many highlights as the signals reflect off different surfaces and parts of the fish body and swim bladder. The temporal characteristics of echoes from salmon are highly aspect dependent and six temporal parameters were used in a support vector machine to discriminate between species. Results suggest that killer whales can classify salmon based on their echoes and provide some insight as to which features might enable the classification.
Asunto(s)
Percepción Auditiva , Ecolocación , Conducta Predatoria , Salmón/fisiología , Percepción del Tiempo , Orca/psicología , Sacos Aéreos/fisiología , Algoritmos , Animales , Simulación por Computador , Señales (Psicología) , Conducta Alimentaria , Preferencias Alimentarias , Movimiento (Física) , Reconocimiento de Normas Patrones Automatizadas , Patrones de Reconocimiento Fisiológico , Salmón/clasificación , Dispersión de Radiación , Procesamiento de Señales Asistido por Computador , Sonido , Espectrografía del Sonido , Máquina de Vectores de Soporte , Factores de Tiempo , Orca/fisiologíaRESUMEN
The target detection capability of bottlenose dolphins in the presence of artificial masking noise was first studied by Au and Penner [J. Acoust. Soc. Am. 70, 687-693 (1981)] in which the dolphins' target detection threshold was determined as a function of the ratio of the echo energy flux density and the estimated received noise spectral density. Such a metric was commonly used in human psychoacoustics despite the fact that the echo energy flux density is not compatible with noise spectral density which is averaged intensity per Hz. Since the earlier detection in noise studies, two important parameters, the dolphin integration time applicable to broadband clicks and the dolphin's auditory filter shape, were determined. The inclusion of these two parameters allows for the estimation of the received energy flux density of the masking noise so that the dolphin target detection can now be determined as a function of the ratio of the received energy of the echo over the received noise energy. Using an integration time of 264 µs and an auditory bandwidth of 16.7 kHz, the ratio of the echo energy to noise energy at the target detection threshold is approximately 1 dB.
Asunto(s)
Percepción Auditiva , Delfín Mular/psicología , Ecolocación , Ruido/efectos adversos , Enmascaramiento Perceptual , Detección de Señal Psicológica , Estimulación Acústica , Acústica , Animales , Umbral Auditivo , Delfín Mular/fisiología , Movimiento (Física) , Presión , Procesamiento de Señales Asistido por Computador , Sonido , Espectrografía del Sonido , Factores de TiempoRESUMEN
The baiji (Lipotes vexillifer) of the Yangtze River possesses a sophisticated biosonar system. In this study, a finite element approach was used to numerically investigate the propagation of acoustic waves through the head of the Yangtze River dolphin, which possesses an inhomogeneous and complex structure. The acoustic intensity distribution predicted from models with and without the melon and/or skull showed that the emitted sound beam was narrow and formed a highly directed acoustic beam, and the skull and melon significantly enhanced the directional characteristics of the emitted sound. Finally, for a short duration impulsive source, the emitted sound pressure distributions were also simulated at different propagation times. The results provide useful information for better understanding the operation of the biosonar system in this rare and perhaps extinct animal.
Asunto(s)
Simulación por Computador , Delfines/fisiología , Ecolocación , Modelos Biológicos , Ultrasonido/métodos , Vocalización Animal , Sacos Aéreos/anatomía & histología , Sacos Aéreos/fisiología , Animales , Delfines/anatomía & histología , Delfines/clasificación , Análisis de Elementos Finitos , Movimiento (Física) , Análisis Numérico Asistido por Computador , Presión , Cráneo/anatomía & histología , Cráneo/fisiología , Sonido , Espectrografía del Sonido , Factores de TiempoRESUMEN
Ecological acoustic recorders (EARs) were moored off the bottom in relatively deep depths (609-710 m) at five locations around the island of Kauai. Initially, the EARs had an analog-to-digital sample rate of 64 kHz with 30-s recordings every 5 min. After the second deployment the sampling rate was increased to 80 kHz in order to better record beaked whale biosonar signals. The results of the 80 kHz recording are discussed in this manuscript and are the results of three deployments over a year's period (January 2010 to January 2011). Five categories of the biosonar signal detection of deep diving odontocetes were created, short-finned pilot whales, sperm whales, beaked whales, Risso's dolphins, and unknown dolphins. During any given day, at least one species of these deep diving odontocetes were detected. On many days, several species were detected. The biosonar signals of short-finned pilot whales were detected the most often with approximately 30% of all the signals, followed by beaked and sperm whales approximately 22% and 21% of all clicks, respectively. The seasonal patterns were not very strong except in the SW location with distinct peak in detection during the months of April-June 2010 period.