Sonar Of Dolphins Research Articles

Biomimetic Sonar Innovation Inspired from Dolphins: A Comprehensive Review

Abstract: The sonar of dolphins has evolved over millions of years and has attained outstanding performance levels. Using the exceptional performance of the dolphins’ sonar as an impetus, bio-inspired wideband acoustic sensing approaches for underwater target recognition and tracking are under development. In this study, we have sight seen what they expect to extract as a gain from such a wideband sonar. The systems wideband sensors are grounded on bottlenose dolphins’ sonar, encapsulating a frequency band from about 30 to 150 kHz and having a frequency reliant on beamwidth substantially larger than that of conventional imaging sonars. The system can be made fairly compact and apt for mounting on diverse platforms including small-scale autonomous underwater automobiles to permit the sonar to function in an analogous way to that used by dolphins. In this paper, we have highlighted the mechanism and applications of the sonar innovation in various domains along with the ongoing developments with regard to it.

Launching underwater bioacoustics in Asia by Whitlow W. L. Au

Whitlow W. L. Au combined biosonar science with engineering. His studies influenced so many students in Asia no matter what their specialities, such as physiology, morphology, and physics. The epoch-making book “The Sonar of Dolphins” is an ideal example of his interdisciplinary approach. Whit educated young researchers in various ways even he did not notice. He led discussion among scientists that motivated current and new generations to conduct underwater and terrestrial bioacoustic research in the lab, in the forest and in the ocean. Quite a few attendees were from Asia at the series of biosonar symposiums in 1991 Moscow, in 1994 Harderwijk, and in 1998 Algarve, but the symposium held in 2009 Kyoto accommodated nearly 200 international specialists and half of them were Asian. An example of his influence was the towed and fixed passive acoustic monitoring in the Yangtze River, China, which revealed a range-wide distribution of finless porpoises collaborating with an international team. These techniques were applied later in India, Thailand, Malaysia, Nepal, Taiwan, Hongkong, and many other areas including Japan for the impact assessment of offshore wind farm developments. We owe him all the outcomes of underwater biosonar studies in Asia.

Is broad angular coverage necessary for echolocation-based discrimination involving aspect-dependent targets?

Building on the foundation of Dr. Whitlow Au’s pioneer and extensive work on the sonar of dolphins, recent research has illuminated the dynamic nature of echolocation involving free-swimming toothed whales. The sophisticated orchestration of movements and biosonar outputs by toothed whales is particularly relevant in the context of developing agile autonomous sonar-guided underwater vehicles. In this study, we test the hypothesis that broad angular coverage, which provide comprehensive echo information of aspect-dependent objects, is necessary for target discrimination via echolocation. We trained a harbor porpoise to actively approach and select a sphere against a spheroid in a two-alternative forced-choice target discrimination task in a net pan. Two spheroids of different aspect ratios representing two overall difficulty levels were used with each presented at diverse orientations when paired with the sphere. We show that the porpoise can discriminate these targets without acquiring aspect-dependent spheroid echo information over broad ranges of angles. Instead, focused, rapid sampling via buzzes appears to aid discrimination in more challenging scenarios. These results suggest that echolocation-based discrimination involving aspect-dependent objects is possible based on subsets of echo signatures without more extensive angular sampling that could build toward an understanding of the target identity. [Work supported by ONR.]

Something just clicked: Whitlow Au and the sonar of dolphins

I suspect that no one, especially not Whit, imagined in 1970 that he would become the world's authority on dolphin biosonar, also known as active echolocation. Since that time Whit has amassed an astonishing list of hundreds of publications on the subject, including the seminal text on marine mammal echolocation, The Sonar of Dolphins, published in 1993. It may surprise many of the younger members of ASA to know that there was a Cold War “arms race” for knowledge about dolphin sonar and that Whit and his U.S. colleagues carried on a lively and mutually enriching correspondence with Soviet colleagues against a background of government intrigues and limitations on travel and conference attendance out of concerns about a “biosonar gap” every bit as worrisome to military leaders as the nuclear arms race (well, maybe not quite as worrisome). Since then Whit has branched out to many other fields of bioacoustics and mentored a diverse array of students at the University of Hawaii, but I will focus on the years at the Navy's marine mammal facility in Kaneohe, Hawaii, where I had the good fortune to work alongside Whit for several years.

Bioacoustics research in Asia, promoted by Whitlow W. L. Au

The sonar of dolphins (1993) written by Whitlow W. L. Au accelerated underwater bioacoustics research, especially in Asian odontocetes. Before this book, very limited ultrasonic recording of odontocetes and bioacoustics research of marine mammals have been done in Asia. The Yangtze freshwater cetaceans provided opportunities for Asian researchers to study biosonar behavior, passive acoustic monitoring methods, and auditory physiology of odontocetes. The above works were accomplished with the Whitlow Au's preceding studies as basic references. The passive acoustic monitoring method developed from the Yangtze finless porpoises has been applied internationally in recent years. With encouragement and supports from Whitlow Au, biosonar research, auditory sensitivity measurement, and long term acoustic monitoring have been extensively conducted on Chinese white dolphins and oceanic finless porpoises, which are the key species in coastal environmental assessment, especially for the windmill farm construction are...

The engineer in field biologist’s clothing: Whitlow Au’s academic years

In 1993, the same year that The Sonar of Dolphins was published, Whitlow Au transitioned from the U.S. Navy’s Naval Ocean Systems Center to the Hawaii Institute of Marine Biology. Thus began a second professional act, so to speak, of field-based research and mentoring the next generation of marine bioacousticians. An electrical engineer doing field biology may not seem like the natural order of things at first, but the combination of Whitlow’s engineering and acoustic prowess coupled with the enthusiasm and energy of bright young biologists resulted in a powerful research team. Thanks to Whitlow’s ingenuity and commitment to advancing the state of the art, Hawaii’s coastlines and marine habitats around the world were explored like never before. A lack of funding or the availability of appropriate instrumentation were never an obstacle, but rather became opportunities for creativity and invention. Whitlow and his students’ research on dolphins, their prey, snapping shrimp, humpback whales, and other taxa l...

Dolphin-inspired sonar system and its performance

The sonar of dolphins has developed over millions of years of evolution and has achieved excellent performance levels. Using the excellent performance of the dolphins sonar as an inspiration, bio-inspired wideband acoustic sensing methods for underwater target detection and tracking are being developed. In this study the authors explore what they expect to gain from such a wideband sonar. The systems wideband sensors are based on bottlenose dolphins sonar, covering a frequency band from around 30 to 150 kHz and having a frequency dependent beamwidth considerably larger than that of conventional imaging sonars. The system can be made relatively compact and is suitable for mounting on a variety of platforms including small-scale autonomous underwater vehicles to allow the sonar to operate in a similar way to that used by dolphins. In contrast to high-resolution image processing techniques, detection and classification in the wideband system are based on pattern recognition methods applied to the echo spectra. The authors highlight the properties of the transducers needed for such a system indicating how these properties may be exploited to give improved sonar performance. The results obtained from such a system are presented to illustrate the effectiveness of this approach.

Acoustic basis for fish prey discrimination by echolocating dolphins and porpoises

The biosonar system of dolphins and porpoises has been studied for about 5 decades and much has been learned [Au, W. W. L. (1993). The Sonar of Dolphins (Springer, New York)]. Most experiments have involved human-made targets; little is known about odontocetes' echolocation of prey. To address this issue, acoustic backscatter from Atlantic cod (Gadus morhua), gray mullet (Chelon labrosus), pollack, (Pollachius pollachius), and sea bass (Dicentrarchus labrax) was measured using simulated biosonar signals of the Atlantic bottlenose dolphin and harbor porpoise. The fish specimens were rotated so that the effects of the fish orientation on the echoes could be determined. Echoes had the highest amplitude and simplest structure when the incident angle was perpendicular to the longitudinal axis of the fish. The complexity of the echoes increased as the aspect angle of the fish moved away from the normal aspect. The echoes in both the time and frequency domains were easily distinguishable among the four species of fish and were generally consistent within species. A cochlear model consisting of a bank of band-passed filters was also used to analyze the echoes. The overall results suggest that there are sufficient acoustic cues available to discriminate between the four species of fish based on the echoes received, independent of aspect angle.

An echolocation visualization and interface system for dolphin research

The present study describes the development and testing of a tool for dolphin research. This tool was able to visualize the dolphin echolocation signals as well as function as an acoustically operated "touch screen." The system consisted of a matrix of hydrophones attached to a semitransparent screen, which was lowered in front of an underwater acrylic panel in a dolphin pool. When a dolphin aimed its sonar beam at the screen, the hydrophones measured the received sound pressure levels. These hydrophone signals were then transferred to a computer where they were translated into a video image that corresponds to the dynamic sound pressure variations in the sonar beam and the location of the beam axis. There was a continuous projection of the image back onto the hydrophone matrix screen, giving the dolphin an immediate visual feedback to its sonar output. The system offers a whole new experimental methodology in dolphin research and since it is software-based, many different kinds of scientific questions can be addressed. The results were promising and motivate further development of the system and studies of sonar and cognitive abilities of dolphins.

The impact of observer dynamics on sonar perception

The minimum information necessary for a moving observer to track objects depends on body dynamics, sensor design, sensor configuration, and environmental perturbations. This paper will present governing equations relating sonar measurements to 6 DOF dynamics, and eight nondimensional parameters describing the transitions between various regimes. Using nondimensional analysis, it will be shown that to minimize second-order effects, an observer should increase its ping rate as it approaches a target. Bats have been observed to increase their ping rate as they approach a target [Altringham, Bats: Biology and Behavior (1996)]. Alternatively, an observer might use a target’s angular rate to predict second-order range effects. This requires the angular rate to become observable prior to second-order range effects becoming observable. This yields a design constraint relating velocity, ping rate, and aperture, but not wavelength. Based on this constraint, it appears some marine mammals could track objects in the second-order regime [Au, The Sonar of Dolphins (1993)]. [Work supported by ONR.]

The Larynx–Melon–Vestibular Lips (LMVL) model of the dolphin sonar. II. The melon beam former

The LMVL model of the dolphin sonar is based on the following system components: (1) the Larynx, controlled by the palatopharyngeal sphincter and operating as a ‘‘sawtooth’’ relaxation oscillator, is the source of the echolocation pulses (the so-called ‘‘clicks’’), and its acoustic output is coupled to the melon through the impedance matching nasal ducts; (2) the Melon, because of its low sound velocity, acts as a ‘‘slow waveguide’’ to form the observed forward-looking beam patterns; and (3) the residual air in the nasopharyngeal cavity acts as an air-pressure reservoir to energize relaxation oscillations of the Vestibular Lips, resulting in the lip-modulated tonal phonations (the so-called ‘‘whistles’’) that radiate through the corresponding vestibular sac. The larynx sawtooth generator has been treated previously [J. W. Fitzgerald, Part I Oceans ’94, Vol. I, pp. 271–276 (Sept. 1994)]. The measured sound velocity in the melon decreases with temperature from v≂1.39×105 cm/s @10<th>°C to v≂1.28×105 cm/s @40<th>°C. Melonlike acoustic slow waveguides, with intermediate sound velocities, yielded average pulse beamwidths of θ1≂11.5° (−3 dB) and θ2≂20.0° (−10 dB). This compares to accepted average values from measurements on live dolphins of θ1≂10.0° (−3 dB) and θ2≂21.8° (−10 dB) [W. Au, The Sonar of Dolphins (Springer-Verlag, New York, 1993), p. 105]. These preliminary measurements of melonlike acoustic slow waveguides, and the dissertation of Part I of this series, support the LMVL model of the dolphin sonar.

The dolphin echolocation system

The sonar of dolphins may be the most sophisticated of all sonar systems, biological or man-made, in shallow waters and for short ranges. The Atlantic bottlenose dolphin emit short-duration (50–70 μs), high-frequency (120–140 kHz), broadband (40–50 kHz) echolocation signals with peak-to-peak amplitudes up to 228 dB re: 1 μPa. The type of signals used by dolphins play a significant role in their sonar discrimination capabilities. They have been observed detecting, classifying, and retrieving prey that is buried in sandy bottom up to a depth of about 0.3 m. In addition, controlled echolocation experiments have shown that dolphins can discriminate wall thickness, material composition, shape, and size of targets. The echolocation system of dolphins will be discussed in three parts. The first part will consider the properties of the receiving system (auditory capabilities). The second part will deal with the characteristics of echolocation signals, and the third part will consider several sonar capabilities.

Potential impacts of low-frequency anthropogenic noise on the hearing of subarctic beluga whales in the Saint Lawrence estuary

A small population of about 500 beluga whales, Delphinapterus leucas, resides in the Saint Lawrence estuary, isolated from other populations of its species. This population has been extensively studied over the last 12 years in terms of its seasonal distribution, size, age, group structure, pathology, and group behavior. It is now considered to be threatened by human activities including elevated noise levels due to a wide range of anthropogenic sources including merchant shipping and whale watching activities. A whale recovery plan is in development that will include hearing conservation. Ambient noise measurements mwere made at the three major sites of habitation of these whales to gain an understanding of the daily fluctuations in noise levels and to establish a baseline characterization of the acoustic environment at each site. The noise levels were related statistically by site, time of day, and human activity and compared to beluga hearing sensitivity curves [W. Au, The Sonar of Dolphins (1993)] and indicate the probability that hearing damage will occur for animals occupying two of the three sites. Specifically, 200 Hz, 500 Hz, and 1 kHz and 40 kHz were scrutinized. [Work supported by World Wildlife Fund Canada, Humane Society Canada, and Parks Canada.]

Understanding humpback whale sonar: A physicist’s view

Just as beamforming matched filter sonar (BMF) provides a simple model for the sonar of bats and dolphins, so do recently developed matched-field processing sonars (MFP) provide simple models for the sonar of humpbacks and other mysticetes. This talk reviews the principles of MFP sonar and the behaviors essential to its use. As BMF is optimal for locating small, nearby, rapidly moving targets (potential prey), so is MFP sonar optimal for locating large, distant, slow-moving targets (potential mates). While BMF uses mainly the direct echo from a target, MFP sonar uses the complete reflected wavetrain, matching the latter with the convolution of the source and a set of empirical Green’s functions. MFP sonar requires lower frequencies, more power, and longer listening times than BMF sonar, which is why humpback sound sequences consist of long patterns of regularly spaced sweeps rather than the click trains of odontocetes. Observations of dolphins show their expertise at BMF; similarly, the careful acoustic and visual observations of humpbacks by Payne, Tyack, Herman, Frankel and others show the expertise of humpbacks at MFP sonar. Their observations suggest that when a singer continues to sing after being joined by a nonsinger, the joiner is likely an immature male learning to echolocate; also, the rapid convergence of humpback whale song is a trait selected to impede the use of singer echoes by nonsinging males.

The Sonar of Dolphins. Whitlow W. L.

Previous articleNext article No AccessNew Biological BooksThe Sonar of Dolphins. Whitlow W. L.Ronald J. SchustermanRonald J. Schusterman Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 69, Number 2Jun., 1994 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/418595 Copyright 1994 The University of ChicagoPDF download Crossref reports no articles citing this article.

Books Review

Book reviews in this article: The Sonar of Dolphins. Whitlow W. L. Au. Mammal Species of the World: a Taxonomic and Geographic Refference. Second Edition. Edited by Don E. Wilson and DeeAnn M. Reeder.

The Sonar of Dolphins

First Page

The sonar of dolphins

The sonar of dolphins