Whitlow Au

University of Hawaiʻi at Mānoa | UH Manoa

No PDF available ABSTRACT Spinning is a natural and common dolphin behavior; however, its role in echolocation is unknown. We used computed tomography (CT) data of a live and a recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstrcution. The anatomical config...

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 wrappe...

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 tagge...

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...

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 b...

In 1974, Norris and Harvey measured the sound velocity profile of the melon of a just deceased bottlenose dolphin and found a low-velocity core in the melon with the velocity increasing towards the surface. This was the genesis of the “melon focusing” hypothesis in the formation of the biosonar beam. Aroyan solved the wave equation for a signal pro...

The echolocation signals emitted by odontocetes can be roughly classified into three broad categories: broadband high-frequency echolocation signals, narrowband high-frequency echolocation signals, and frequency modulated clicks. Previous measurements of broadband echolocation signals propagation in the bottlenose dolphin (Tursiops truncatus) did n...

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 as follows: (1) a 475-ms linear frequency-modulated (FM) pulse with a frequency range from 23 to 160 kHz; (2) a...

Yangtze finless porpoises (Neophocaena asiaeorientalis) are known to use the narrowband signals for echolocation. In this study, a finite-element model was configured based on computed tomography imaging technique and tissue physical properties measurement to simulate biosonar signal emission and transmission processes through animal’s head. The ro...

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...

Modern bioacoustic research with aquatic animals began in Hawaii in the 1968–1969 period when three independent programs started almost simultaneously. Two faculty members began studying various facets of hearing in fish at the University of Hawaii. Another faculty member from a different department established a laboratory in which dolphin hearing...

Pelagic animals that form deep sea scattering layers (DSLs) represent an important link in the food web between zooplankton and top predators. While estimating the composition, density and location of the DSL is important to understand mesopelagic ecosystem dynamics and to predict top predators’ distribution, DSL composition and density are often e...

Porpoises are small-toothed whales, and they can produce directional acoustic waves to detect and track prey with high resolution and a wide field of view. Their sound-source sizes are rather small in comparison with the wavelength so that beam control should be difficult according to textbook sonar theories. Here, we demonstrate that the multiphas...

Yangtze finless porpoises (Neophocaena asiaeorientalis) are known to use the narrowband signals for echolocation. In this study, a finite-element model was configured based on computed tomography imaging technique and tissue physical properties measurement to simulate biosonar signal emission and transmission processes through animal’s head. The ro...

The unique shape of a dolphin head, the different specie specific shape and the internal head structure suggest a very complex propagation mechanism for the biosonar signals to travel from the phonic lips into the water. Despite these factors, a circular planar aperture of the appropriate diameter can produce a transmission beam that resembles the...

The central slope of the Gulf of Mexico (GOM) is home to over 20 species of marine mammals. Prior to the Deep Horizon Oil Spill in 2010, sperm whales were the predominately sighted large whale in the area. This study investigated the distribution and utilization of the north-central GOM by sperm whales two years after the spill by comparing sperm w...

Dolphins and porpoises use their sophisticated biosonar systems for targets detection, within a range of a few meters to about 200 m, there is not a better sonar on the planet. In this study, the high resolution computer tomography (CT) scan data were used to create the detecting click signal propagation models of Atlantic bottlenose dolphins (Turs...

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...

Harbor porpoises (Phocoena phocoena) use narrow band echolocationsignals 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 acous...

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 numb...

An experiment was conducted to determine if a blindfolded echolocating dolphin modified its biosonar signals depending on the targets it was investigating in a target shape discrimination task. Biosonar signals were measured with a specially designed bite-plate apparatus with a dowel extending from the bite plate to support the hydrophone. The dete...

The Kona coast of the island of Hawaii hosts many species of odontocetes. These marine mammals are top predators and their foraging activity plays an important role in the ecosystem dynamics. Three passive acoustics recorders were used to study the temporal and spatial occurrence of the foraging activity of odontocetes (excluding beaked and sperm w...

On-animal suction cups with embedded hydrophones allow examination of how signals on the forehead of echolocating odontocetes relate to the internal anatomical structure and the transmission beampattern. Risso’s dolphin (Grampus griseus) is an interesting species for this investigation due to the presence of a unique vertical groove in the middle o...

Laguna de Términos, Campeche, México, is one of the largest coastal lagoons in Mexico where snapping shrimp is the main source of biological sound. We measured the environmental noise from 2004 to 2008 in stations distributed homogeneously in this lagoon during 17 sampling periods using a digital audio tape recorder sampling at 48 kHz with 16 bits...

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 range...

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 loca...

Spinner dolphins (Stenella longirostris) in the near-shore waters of the Hawaiian islands forage on the mesopelagic boundary community (mbc) of organisms consisting of myctophids, mid-water shrimp, and small squids. They forage at night in a coordinated fashion swimming parallel to shore hunting for patches of prey that they can encircle and herd i...

Porpoises are well known to emit directional ultrasound beams for detecting and tracking preys; however, how they produce and manipulate directional beams are challenging. Here, we investigated physical mechanism of ultrasound beam formation and control of finless porpoise (N. a. sunameri) by using an integrated scheme of computed tomography, tissu...

Deep diving odontocetesodontocetes feed in the deep ocean on mesopelagic squid and fish. The distribution of these prey are poorly known but does affect the distribution of deep diving odontocete predators. Hence, it is important to collect data on the density and composition of potential prey to identify deep sea habitats that attract deep diving...

Active acoustics is an important tool to quantitatively assess the densities of pelagic organisms. While it is an important tool, it is hard to determine the organism composition recorded acoustically especially in oligotrophic waters where mixed organism assemblages are common. One such mixed stock in the Hawaii Islands is the Deep Scattering Laye...

Bottlenose dolphins (Tursiops aduncus) are a well-known species using broadband echolocation signals for searching prey and spatial orientation. In this study, the computed tomography (CT) scan data were obtained to set up a two-dimensional finite element model. In the vertical plane, the acoustic field on the animal’s forehead and the far field tr...

Humpback whale calves in the winter breeding grounds vocalize and the spectral characteristics of some of these vocalizations have been described, but sound levels of calf vocalizations have not been investigated. There is also a lack of general information on vocalizations from mothers. To address these issues, we deployed suction cup acoustic and...

Understanding the distribution of animals is of paramount importance for management and conservation, especially for species that are impacted by anthropogenic threats. In the case of marine mammals there has been a growing concern about the impact of human-made noise, in particular for beaked whales and other deep diving odontocetes. Foraging (mea...

Suction cup deployed acoustic tags have been used to study the echolocation behavior of a number of odontocetes, yet the relationship between the projected biosonar signals and tag recordings are not known. Acoustic data obtained from these tags consist of the number of clicks emitted, the depth at which the clicks are emitted and the inter-click i...

Previous studies in the Northwestern Hawaiian Islands (NWHI) focused on shallower communities in and near reefs and did not investigate the organisms living in deeper waters that some apex predators rely on for food, e.g., some odontocetes forage at depths greater than 400 m. To examine the relationship between deep-diving odontocete predators and...

Bottlenose dolphin echolocation clicks display a great diversity in temporal and spectral structure, with both unimodal and bimodal spectra observed (Houser et al., JASA, 1999). Wavelet scalograms applied to data collected by the Navy Marine Mammal Program and the Bioacoustic Measuring Tool (BMT) (Martin et al., JASA, 2005) show that echolocation c...

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...

The use of passive acoustic monitoring (PAM) to detect aquatic life continues to increase because PAM devices can be deployed in remote areas and can operate for months or years at a time in a programmed manner to control the recording time, the duration of each recording, and the time to “sleep” to preserve battery power. This introduction will di...

The Station ALOHA Cabled Observatory (ACO) is an ocean-bottom observatory that allows continuous real-time monitoring of ocean processes including sounds produced by baleen whales. Baleen whales can be challenging to study using traditional visual methods due to their cryptic behavior and offshore ranges. Many baleen whales produce distinctive soun...

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats. Methods. We used a two-dimensional cross...

Power spectral density of ambient noise in Beibu Gulf at sea state of zero and hydrophone self-noise The nominal self-noise level was obtained when the hydrophone was connected to the voltage pre-amplifier VP2000 and was provided courtesy of the Reson company. The gray lines were the 95% confidence interval of the ambient noise.

Beam pattern of circular piston transducer Modeling was based by using a radius of 4 cm (directivity index = 3 dB) and 6 cm (directivity index = 6 dB) piston transducer at typical Sousa whistle frequency of 6.35 kHz.

Sound propagation model

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 be...

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats. Methods. We used a two-dimensional cross...

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats. Methods. We used a two-dimensional cross...

Characterizing the trophic roles of deep-diving odontocete species and how they vary in space and time is challenged by our ability to observe foraging behavior. Though sampling methods are limited, foraging activity of deep-diving odontocetes can be monitored by recording their biosonar emissions. Daily occurrence of echolocation clicks was monito...

New data have significantly increased our understanding of sound propagation within the heads of dolphins. Results of Au et al. (2016) reinforce the notion that source intensity is the primary factor controlling the peak and center frequencies of biosonar clicks which in turn affects the duration and the bandwidth of clicks. Finite element simulati...

This title brings to light the discoveries and insights into the lives of many marine species made possible over the last decade by passive acoustic recorders (PAR). Pop-ups, ARF, HARP, EAR, Bprobe, C-POD Atag, and Dtag are the acronyms of some of the many PARs that have changed our understanding of how marine animals live and strive in the ocean....

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 frequen...

The backscatter properties of jumbo or Humboldt squid (Dosidicus gigas) were examined in-situ by projecting simulated sperm whale (Physter macrocephalus) clicks to tethered squids. The incident signal was a broadband click with a peaked frequency of approximately 17 kHz. Echoes were collect for three different aspect angles; (broadside, anterior,...

Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for locating prey and spatial orientation. In this study, acoustic impedance values of tissues in the porpoise’s head were calculated from the Hounsfield Units (HU). A two-dimensional finite element model was set up base on the computed tomography (CT) scan data to simulate t...

The characteristics of echolocation signals used by ah arbour porpoise ( Phocoena phocoena )d uring a target detection experiment are described. Aw ater- filled steel sphere (either 5.08 or 7.62 cm in diam- eter) was placed at distances of 12, 14, 16, 18 and 20 mf rom ah arbour porpoise stationed in an underwater hoop. Detection was determined by a...

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...

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...

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. A bite-plate device that the dolphins carried supported a hydrophone that extended directly in front...

Finless porpoise (Neophocaena asiaeorientalis) is known to use the narrow band signals for echolocation living in the Yangtze River and in the adjoining Poyang and Dongting Lakes in China. In this study, the sound velocity and density of different tissues (including melon, muscle, bony structure, connective tissues, blubber, and mandibular fat) in...

There is increasing concern over the potential ecological effects from high levels of oceanographic anthropogenic noise on marine mammals. Current US NOAA regulations on received noise levels as well as the Draft Guidance for Assessing the Effect of Anthropogenic Sound on Marine Mammals are based on limited studies conducted on few species. For the...

Ecological acoustic recorders (EARs) have been deployed at several locations in Hawaii and in other western Pacific locations to study the foraging behavior of deep-diving odontocetes. EARs have been deployed at depths greater than 400 m at five locations around the island of Kauai, one at Ni’ihau, two around the island of Okinawa, and four in the...

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 predi...

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....

Even though they live in quite different habitats, many bats, a few birds, and a number of marine mammals, including dolphins, rely on biosonar for navigation and foraging for food. Despite the fact that bats are aerial echolocators, whereas dolphins use underwater sonar, both groups depend on their sonar signals to detect, discriminate, locate, tr...

To understand the distribution of deep diving odontocetes, it is important to investigate the relationship between foraging whales and their prey. Tagged sperm whales have been documented to dive as deep as 1202 m. Short-finned pilot whales in Hawaii dive deeper during the day down to 600-800 m and shallower dives at night, driven possibly by the m...

Estimating the density of organism living in deep sea scatting layers is of key importance for understanding the biomass in the mesopelagic layers. Scientific echosounders are routinely used for this task; however, new imaging sonar technologies pose the opportunity for estimating density of organism, as well as identification at smaller scales. Du...

The melon of dolphins is considered by many as the structure responsible for the focusing of the biosonar beam. However, finite element numerical simulation of the head of the Chinese river dolphin (Lipotes vexillifer) indicates that the biosonar beam is formed by reflections off the airsacs and bony structures in the skull. The finite element appr...

Measuring on-axis biosonar signals from a free swimming dolphin performing a sonar task is extremely difficult without having a special device that the animals carry. A bite-plate device which had a hydrophone directly in front of the dolphin at a fixed location along the beam axis of the biosonar beam was constructed as a part of the Navy Marine M...

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 beake...

The mammalian order cetacea consist of dolphins and whales, animals that are found in all the oceans and seas of the world. A few species even inhabit fresh water lakes and rivers. A list of 80 species of cetaceans in a convenient table is presented by Ridgway [20.1]. These mammals vary considerably in size, from the largest living mammal, the larg...

Beaked whales, sperm whales, pilot whales, and Risso's dolphins perform deep dives to feed on prey in the deep sea. They use echolocation to detect prey, and echolocation can be monitor as a proxy of their foraging activities. Ecological acoustic recorders were deployed to monitor in time the echolocation signals of pilot whales, Risso's dolphins,...

For many years, the navy has used directional frequency analysis and recording (DIFAR) sonobouys to record and track ships. DIFAR sonobouys compute acoustic particle velocity for two bimodal perpendicular hydrophone elements, which, with a magnetic compass, gives a directional bearing to the sound recorded on a third omnidirectional hydrophone. Use...

Passive acoustic monitoring using seafloor-mounted recorders allows cetacean occurrence to be examined over time and space. Four ecological acoustic recorders (EARs) were moored around the Hawaiian island of Niihau in summer/fall (July-November) 2011, and winter/spring (January-May) 2012. Delphinid whistle "detections" (a proxy for schools) were id...

The ALOHA Cabled Observatory, ACO, located 100 km north of the island of Oahu, Hawaii, includes an acoustic recording package. The hydrophone is at a depth of 4.7 km and is connected to land via an underwater fiber optic cable. Recordings are continuous and made year-round. One year of data, 17 February 2007 to 18 February 2008, were analyzed to de...

The biosonar target detection in noise capability of the Atlantic bottlenose dolphin (Tursiops truncatus) has been studied as early as 1981 by Au and Penner. At that time, they presented results of the performance of two dolphins as a function of the signal energy to the density of the noise intensity (as in human psycho-acoustics) and not the sign...

Spectrograms generated with the pseudo Wigner-Ville distribution (PWVD) provide much higher simultaneous time-frequency (TF) resolution compared with the traditional method using the short time Fourier transform (STFT). The WV-type spectrogram allows bioacousticians to study the fine TF structures of the sound, such as the instantaneous frequency,...

The Mariana Swiftlet (Aerodramus bartschi) is a federally listed endangered species of is native to Guam and the Marianas Islands. There is also a small, introduced population of Marianas Swiftlets on the island of Oahu, Hawaii. The nesting cave in Oahu is a small tunnel built for agricultural irrigation. Marianas swiftlets live in caves, which the...

Dolphins that emit whistle signals (except for sperm whales) project short broadband biosonar clicks containing about 5 to 7 cycles with exponential decaying envelope and Q (center frequency over bandwidth) between 2 and 3. The broadband nature of the biosonar clicks allow for good temporal resolution of echo highlights which in turn allows for the...

Remote autonomous ecological acoustic recorders (EARs) were deployed in deep waters at five locations around the island of Kauai and one in waters off Ni'ihau in the main Hawaiian island chain. The EARs were moored to the bottom at depths between 400 and 800 m. The data acquisition sampling rate was 80 kHz and acoustic signals were recorded for 30...

Object constancy, the ability to recognize objects despite changes in orientation, has not been well studied in the auditory modality. Dolphins use echolocation for object recognition, and objects ensonified by dolphins produce echoes that can vary significantly as a function of orientation. In four experiments, human listeners had to classify echo...

Dolphins that emit whistle signals (except for sperm whales) project short broad- band biosonar clicks containing about 5 to 7 cycles with exponential decaying envelope and Q (center frequency over bandwidth) between 2 and 3. The broadband nature of the biosonar clicks allow for good temporal resolution of echo highlights, which in turn allows for...

Sensitivity of echolocating dolphins to phase changes within echoes may be a vital piece of information when constructing echolocation models. Previous experiments have yielded ambiguous results leaving it unclear what cues might have been used by passively listening dolphins to discriminate between different phase altered signals. This study used...

A time-frequency contour extraction and classification algorithm was created to analyze humpback whale vocalizations. The algorithm automatically extracted contours of whale vocalization units by searching for gray-level discontinuities in the spectrogram images. The unit-to-unit similarity was quantified by cross-correlating the contour lines. A l...

Marine animals use sound for communication, navigation, predator avoidance, and prey detection. Thus the rise in acoustic energy associated with increasing human activity in the ocean has potential to impact the lives of marine animals. Thirty years ago marine bioacoustics primarily focused on evaluating effects of human-generated sound on hearing...

Despite the importance of young animals to the proliferation of a species, logistic hurdles often prevent the study of individuals' behavior and habitat requirements. This is particularly an issue in the case of cetaceans, which spend a large proportion of their time at depth. We conducted a study to describe the dive behavior of young humpback wha...