Patrick W Moore

National Marine Mammal Foundation · Bioacoustics

Biosonar echo delay resolution was investigated in four bottlenose dolphins (Tursiops truncatus) using a “jittered” echo paradigm, where dolphins discriminated between electronic echoes with fixed delay and those whose delay alternated (jittered) on successive presentations. The dolphins performed an echo-change detection task and produced a condit...

A collaborative effort was undertaken to delineate underwater noise levels within holding enclosures at marine mammal facilities. Ambient noise levels were measured under normal operating conditions in the enclosures of 14 participating facilities. Facility habitats varied from ocean environments to fully enclosed pools. The means and standard erro...

Dolphin echolocation clicks measured far off-axis contain two time-separated components. Whether these components overlap and appear as a single signal on axis has received little attention. Here, the scaled reassigned spectrogram analysis was used to examine if bottlenose dolphin (Tursiops truncatus) clicks measured near- or on-axis of the echoloc...

It is not often that it can be said that an animal has a research career that spans four decades or has been a major contributor (and subject) in more than 30 papers in peer-reviewed journals (including many in The Journal of the Acoustical Society of America). However, one animal that accomplished this was a remarkable bottlenose dolphin (Tursiops...

Psychophysical methods similar to those employed with bats were used to examine jittered echo-delay resolution in bottlenose dolphins (Tursiops truncatus). Two dolphins were trained to produce echolocation clicks and report a change from electronic echoes with a fixed delay of ~ 12.6 ms (~ 9.4 m simulated range) to echoes with delays that alternate...

ABSTRACT Fine-scale echo delay resolution has been investigated using a “jittered” echo paradigm, where animals discriminate between electronic echoes with fixed delay (i.e., simulating fixed range) and echoes with delays that alternate (jitter) on successive echoes. The data consist of the animals’ discrimination performance (e.g., error rate) as...

The United States Navy Marine Mammal Program (MMP) has been in existence for over 50 years. Following its inception, the program quickly became involved in the study of marine mammal sensory systems and bioacoustics. Early studies included the pioneering work of C. Scott Johnson in obtaining the first behavioral audiogram in a dolphin and Sam Ridgw...

The echolocation beam of toothed whales has been studied ever since it was first discovered in 1960. Recent studies have focused on the frequency distributions across the cross sections of the beams. Other studies have focussed on describing the entire acoustic field around the animal. However, no one has yet described the timing of each frequency...

The work of Whitlow Au and colleagues has demonstrated that dolphin biosonar forms a highly directional, forward-facing beam. In our recent studies, we have expanded upon previous work by making biosonar beam measurements using high-resolution hydrophone arrays with up to 48 hydrophones. Bottlenose dolphins were trained to echolocate on both physic...

The echolocation beam of the bottlenose dolphin was first carefully described by Au and colleagues (1978)[“Propagation of Atlantic bottlenose dolphin echolocation signals,” J. Acoust. Soc. Am. 64, 411-422] using various hydrophone array configurations and targets located in front of the dolphin and along its longitudinal axis. Measured beams were d...

Biosonar studies have greatly benefited from the use of electronic, or “phantom,” echoes. In this paradigm, amplitude and timing information are extracted from an emitted biosonar pulse, then a delayed signal is broadcast to the animal to appear as an echo from a more distant target. Phantom echoes provide unique capabilities for studying biosonar,...

The potential for bottlenose dolphins to actively focus their biosonar transmissions was examined by measuring emitted clicks in four dolphins using horizontal, planar hydrophone arrays. Two hydrophone configurations were used: a rectangular array with hydrophones 0.2 to 2 m from the dolphins and a polar array with hydrophones 0.5 to 5 m from the d...

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 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...

Previous measurements of toothed whale echolocation transmission beam patterns have utilized few hydrophones and have therefore been limited to fine angular resolution only near the principal axis or poor resolution over larger azimuthal ranges. In this study, a circular, horizontal planar array of 35 hydrophones was used to measure a dolphin's tra...

For many years, we heard sounds associated with reward from dolphins and belugas. We named these pulsed sounds victory squeals (VS), as they remind us of a child's squeal of delight. Here we put these sounds in context with natural and learned behavior. Like bats, echolocating cetaceans produce feeding buzzes as they approach and catch prey. Unlike...

Echolocation research has carefully detailed the acoustic cues used by bats and dolphins to localize and discriminate sonar targets; however, there remains an incomplete understanding of the larger problem of auditory scene analysis, namely how echo features from the natural environment are perceptually organized in the animal’s sonar receiver. Thi...

It has been proposed that two pairs of phonic lips might be utilized by a dolphin to adaptively manipulate the frequency content and directionality of the echolocation beam in response to acquired target information. The presence of two pulses appearing off-axis of the echolocation beam and separated in time has been proposed as evidence supporting...

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...

Biosonar signals radiated along the beam axis of an Atlantic bottlenose dolphin resemble short transient oscillations. As the azimuth of the measuring hydrophones in the horizontal plane progressively increases with respect to the beam axis the signals become progressively distorted. At approximately ±45°, the signals begin to divide into two compo...

The directional properties of bottlenose dolphin clicks, burst-pulse, and whistle signals were measured using a five element array, at horizontal angles of 0°, 45°, 90°, 135°, and 180° relative to a dolphin stationed on an underwater biteplate. Clicks and burst-pulse signals were highly directional with directivity indices of ~11 dB for both signal...

The use of remote autonomous passive acoustic recorders (PAR) to determine the distribution of dolphins at a given locations has become very popular. Some investigators are using echolocation clicks to gather information on the presence of dolphins and to identify species. However, in all of these cases, the PAR probably recorded mainly off-axis cl...

Many methods for time series analysis derived from nonlinear dynamical systems theory have been developed in the last decade, and have demonstrated remarkable results in a variety of simulated, experimental, and real applications. Classification of time series based on the underlying dynamical generator is also potentially powerful, and we have pre...

To study the effects of acoustic masking from anthropogenic noise, bottlenose dolphin (Tursiops truncatus) echolocation performance was assessed in the presence of different masking noise types using Navy relevant source transmissions. Echolocation clicks produced by the dolphin were detected with a hydrophone, then digitized within a phantom echo...

Recent recordings of dolphin echolocation using a dense array of hydrophones suggest that the echolocation beam is dynamic and can at times consist of a single dominant peak, while at other times it consists of forward projected primary and secondary peaks with similar energy, partially overlapping in space and frequency bandwidth. The spatial sepa...

Auditory scene analysis (ASA) refers to an animal’s ability to organize acoustic information in order to construct an understanding of its environment. In most mammals, vision is the primary sensory system and audition plays a secondary role; however, in the echolocating dolphin the reverse is likely true. One underlying tenant of ASA is stream ana...

Echolocation signals radiated along the beam axis of an Atlantic bottlenose dolphin resemble single transient‐like oscillations. As the azimuth of the measuringhydrophones in the horizontal plane progressively increases with respect to the beam axis the signals become progressively distorted. At approximately ± 45 deg, the signals begin to divide i...

The use of remote autonomous passive acoustic recorders (PARs) to determine the distribution of dolphins at given locations has become very popular. Some investigators are using echolocation clicks to gather information on the presence of dolphins and to identify species. However, in all of these cases, the PAR probably recorded mainly off-axis cli...

Moore and others (2008) previously showed that bottlenose dolphins are capable of beam steering and controlling the vertical and horizontal widths of the echolocation beam. A follow-on study was performed using the same methods as the previous study, but with a younger animal and a higher resolution diamond-shaped hydrophone array for characterizin...

Arrays of up to six broadband suction cup hydrophones were placed on the forehead of two bottlenose dolphins to determine the location where the beam axis emerges and to examine how signals in the acoustic near-field relate to signals in the far-field. Four different array geometries were used; a linear one with hydrophones arranged along the midli...

Odontocete brain tissues associated with auditory processing are hypertrophied and modified relative to their terrestrial counterparts. The relationship between the functional demand on these tissues and metabolic substrate requirements is unknown. Using positron emission tomography (PET), relative cerebral blood flow was measured in a bottlenose d...

The study of site-specific brain activity associated with dolphin echolocation has been hampered by the difficulties inherent in administering radiolabels and performing medical imaging while a dolphin echolocates in an aquatic environment. To overcome these limitations, a system has been developed to allow a bottlenose dolphin to echolocate while...

To date most sonars use narrow band pulses and often only the echo envelope is used for object detection and classification. This paper considers the advantages afforded by bio-inspired sonar for object identification and classification through the analysis and the understanding of the broadband echo structure. Using the biomimetic dolphin based so...

The Journal of the Acoustical Society of America 126(2), 920 (2009) DOI: http://doi.org/10.1121/1.3158940

Bottlenose dolphin (Tursiops truncatus) echolocation beams are typically characterized as symmetrical -3 dB beamwidths; however, the functional width of the beam during target detection has not been explored. Angular target detection thresholds of an echolocating dolphin were examined to more fully describe the functional characteristics of the ech...

As part of an ongoing study, bottlenose dolphin (Tursiops truncatus) echolocation beam steering was assessed as a dolphin performed a target detection task (4- and 7.62-cm spheres) while echolocating with its head held in a fixed orientation and monitored via underwater camera. Targets were placed approximately 4.0 m in front of the dolphin [zero d...

The use of medical imaging techniques in marine mammalogy has traditionally consisted of anatomical investigations within postmortem specimens. Within the last decade, Ridgway pioneered the use of in vivo scanning techniques to study physiological processes in the bottlenose dolphin. His work utilizing PET and SPECT imagings to study processes that...

An array of five broadband suction cup hydrophones were placed on the melon of two bottlenose dolphins to determine where on the melon the echolocation beam emerges and to examine how signals in the acoustic near-field relate to signals in the far-field at 1 m. Four different array geometries were used: a linear one with hydrophones arranged along...

This paper uses advanced time-frequency signal analysis techniques to generate new models for bio-inspired sonar signals. The inspiration comes from the analysis of bottlenose dolphin clicks. These pulses are very short duration, between 50 and 80 micros, but for certain examples we can delineate a double down-chirp structure using fractional Fouri...

The primary goal of this project is to develop the technology and methods required to make quantitative, repeatable, and interpretable measurements of pinniped hearing sensitivity using averaged evoked potentials recorded from the surface of the head. This effort will advance understanding of marine mammal auditory physiology and provide tools nece...

The development of a unique dolphin biomimetic sonar produced data that were used to study signal processing methods for object identification. Echoes from four metallic objects proud on the bottom, and a substrate-only condition, were generated by bottlenose dolphins trained to ensonify the targets in very shallow water. Using the two-element ('bi...

This article reviews Echolocation in Bat and Dolphins by Jeanette A. Thomas, Cynthia F. Moss, Marianne Vater

Dolphins within the Navy Marine Mammal Program use echolocation to effectively locate underwater mines. They currently outperform manmade systems at similar tasks, particularly in cluttered environments and on buried targets. In hopes of improving manmade mine-hunting sonar systems, two instrumentation packages were developed to monitor free-swimmi...

A biosonar measurement tool (BMT) was created to investigate dolphin echolocation search strategies by recording echolocation clicks, returning echoes, and three-dimensional angular motion, velocity, and depth of free-swimming dolphins performing open-water target detections. Trial start and stop times, locations determined from a differential glob...

Recent studies and ongoing research have shown that echolocating dolphins can change the structure of their emitted echolocation signals during active echo‐investigation of targets. The presumption has been that the animal adjusts various parameters (source level, peak frequency, etc.) of the emitted signal to maximize the information return in the...

Auditory evoked potentials (AEPs) offer an alternative to behavioral methods of determining auditory sensitivity in marine mammals. The technique can be performed without the need for animal training, substantially expediting the process, and has the potential for application to stranded and rehabilitating marine mammals, thus providing an opportun...

A necessary condition for acoustic imaging (e.g., synthetic aperture sonar processing) is the capability to sum echo samples from the same point in the environment over different signal-echo pairs. To decide whether a dolphin has this capability, a limited number N of electronically simulated echoes with constant delay were transmitted back to an e...

Two free-swimming dolphins (Tt722 and Tt673) were trained to carry the Biosonar Measurement Tool (BMT) during open water, proud target searches in order to explore echolocation behavior without the constraints of traditional experimental designs. The BMT recorded the angular motion, depth, and velocity of the dolphin as well as echolocation clicks...

Bottlenose dolphins (Tursiops truncatus) use short, wideband pulses for echolocation. Individual waveforms have high-range resolution capability but are relatively insensitive to range rate. Signal-to-noise ratio (SNR) is not greatly improved by pulse compression because each waveform has small time-bandwidth product. The dolphin, however, often us...

Bottlenose dolphins (Tursiops truncatus) detect and discriminate underwater objects by interrogating the environment with their native echolocation capabilities. Study of dolphins' ability to detect complex (multihighlight) signals in noise suggest echolocation object detection using an approximate 265-micros energy integration time window sensitiv...

Mine-hunting dolphins in the Navy's Marine Mammal Systems (MMS) are likely to initially encounter targets on the edge of the maximum response axis (MRA) of the echolocation beam. Understanding how Fleet dolphins perform their search-and-report tasks will provide valuable information toward the enhancement of Navy mine countermeasure (MCM) signal pr...

Data have been collected from two dolphins engaged in free-swimming, bottom-object searches in conjuction with the deployment of both the BMT and IMS systems. Preliminary results demonstrate distinctive search strategies between the animals. The instrumentation described herein has been designed to provide quantitative data for free-swimming dolphi...

The bottlenose dolphin has evolved a unique system of biosonar, or echolocation, that allows it to exploit a visually limited littoral niche. The effectiveness of dolphin echolocation at finding and identifying submerged objects is unsurpassed by man-made hardware systems built for similar tasks. It has become a model system from which to draw hard...

Bottlenose dolphins (Tursiops truncatus) have an acute ability to use target echoes to judge attributes such as size, shape, and material composition. Most target recognition studies have focused on features associated with individual echoes as opposed to information conveyed across echo sequences (feature envelope of the multi-echo train). One fea...

this report was performed for the Office of Naval Research (ONR) by the Biosciences Division of the Space and Naval Warfare Systems Center, San Diego (SSC San Diego) and by Science Applications International Corporation (SAIC) under contract N001498WX20086. ACKNOWLEDGMENTS The authors wish to thank Ms. Nancy Harned, Dr. John Tague, and Mr. David Ar...

This report details the optimization of a bandpass ear model to the auditory sensitivity of the dolphin through the implementation of EP. SCALED AMPLITUDE MODELS The design of several ear model architectures was attempted. Ear models were produced with either 1) scaled amplitude responses and a fixed range of center frequency distributions, or 2) w...

This report describes the creation of a bandpass ear model for the humpback whale (Megaptera novaeangliae), a medium-size baleen whale with worldwide distribution. Anatomical indices of hearing derived from inner ear histology were used to generate a frequency-position function. Sensitivity-position information is lacking for any mysticete. Thus, t...

In humans, hearing is lost with age, trauma, and disease. It is likely marine mammals sustain similar damage, but currently we have little direct data on their incidence of hearing loss. Marine mammals represent an interesting hearing paradox. Because their ears are fundamentally the same as human ears, we expect they have similar loss mechanisms,...

For this report, jawphones were used to behaviorally measure the relative hearing thresholds at four frequencies (10, 30, 60, and 90 kHz) on more than 40 sites of a dolphin's head, from the tip of the rostrum to the base of the pectoral fins. Measurements were converted into iso-sensitivity curves projected onto a two-dimensional, heuristic represe...

Devices known as jawphones have previously been used to measure interaural time and intensity discrimination in dolphins. This study introduces their use for measuring hearing sensitivity in dolphins. Auditory thresholds were measured behaviorally against natural background noise for two bottlenose dolphins (Tursiops truncatus); a 14-year-old femal...

Binaural hearing is an advantage of having two ears. Human benefits are evident in a 3‐dB threshold difference, the ability to localize sound sources in space, and the ability to isolate primary sounds from corresponding echoes. The binaural capabilities of dolphins are relatively unexplored. Studies show that their localization of pure tones under...

Devices known as jawphones have previously been used to measure interaural time and intensity discrimination in dolphins. This study introduces their use for measuringhearing sensitivity in dolphins. Auditory thresholds were measured behaviorally against natural background noise for two bottlenose dolphins (Tursiops truncatus); a 14-year-old female...

Object classifiers that attempt to mimic dolphin echolocation require an auditory weighting function representative of dolphin peripheral auditory processing. An evolutionary program (EvPg) was used to fit the frequency-dependent output of a bank of bandpass filters to the auditory sensitivity of the bottlenose dolphin, Tursiops truncatus. Pseudo-G...

Dolphin echolocation has evolved over millions of years under selection pressures imposed by a selective niche. The complexity and effectiveness of dolphin echolocation for detection and classification of objects within that niche has useful application to U. S. Naval objectives. In these environments, Navy dolphins are likely to first encounter ta...

The hypothesis that echolocating dolphins best receive acoustic signals over the pan bones of the lower jaw is widely accepted. Studies in echolocation and hearing have assumed that those areas serve as the dolphin’s peripheral hearing system. The research that established that model, however, does not exclude other potential sound reception sites...

Dolphins demonstrate a broad range of hearing (>120 kHz), a remarkable frequency-dependent auditory sensitivity, and a fine degree of frequency discrimination across the range of hearing. Evolutionary programming has been successfully used to model the relative auditory sensitivity of the dolphin, but similar models of frequency discrimination have...

During diving, marine mammals must balance the conservation of limited oxygen reserves with the metabolic costs of swimming exercise. As a result, energetically efficient modes of locomotion provide an advantage during periods of submergence and will presumably increase in importance as the animals perform progressively longer dives. To determine t...