Naval Ocean Systems Center Research Articles

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...

Remembrances of Paul O. Thompson at the Naval Ocean Systems Center

Paul Thompson spent 35 years working at the Naval Electronics Laboratory (later the Naval Ocean Systems Center) in San Diego and Hawaii. His research included psychoacoustics and animal bioacoustics. He authored 66 papers and reports, gaining the distinction of Fellow of the ASA. Paul was noted for painstaking data analysis, excellent aural memory, and outstanding skills at sound recording and processing. We present remembrances of Paul as a scientist, colleague, and friend during his years studying marine mammals for the Navy.

Bob Young and his contributions to animal bioacoustics and underwater acoustics

Quintessential component and Past President of ASA, Robert W. Young was truly a scientist par excellence for all seasons. His professional accomplishments excelled in large measure with outstanding assistance of his talented wife, Evelyn. Whether noise, psychoacoustics, architecture, propagation, music, patents, underwater sound, animal bioacoustics, or other discipline(s), his trademark was always distinguished by elegant design and very proper presentation. Whenever new or experienced co-workers needed a bit of correction or retuning, Bob Young (known to many of us as ‘‘Uncle Fussy Ears’’) was the one to seek for sage guidance. All contemporary acoustics manuscripts from the Naval Electronics Laboratory (NEL), later Naval Ocean Systems Center (NOSC), had to pass his scrutiny. The wise chose to seek early comment from Bob Young or chance the possibility of endless editorial notations or internal memos, oftimes pages long. For example, one quickly learned never to describe a whale’s sound as ‘‘loud’’ in lieu of ‘‘high sound source level.’’ With a few examples of his pioneering studies on animal and underwater acoustics we’ll revisit some of Bob Young’s early landmark contributions and hear about a rare privilege of being so close to such authority, propriety and exactitude.

Observations of Habitat Use by Polar Bears, <em>Ursus maritimus</em>, in the Alaskan Beaufort, Chukchi, and Northern Bering Seas

A total of 1112 Polar Bears (Ursus maritimus) at 482 sightings were recorded during aerial surveys in the Beaufort, Chukchi, and northern Bering Seas conducted primarily during September and October from 1979-1999. Of these bears, 784 were observed offshore at 400 sightings. The surveys were conducted by the Naval Ocean Systems Center and Minerals Management Service; they were designed to monitor the fall Bowhead Whale (Balaena mysticetus) migration. Over the 20-year period, 1,096,620 kilometers of surveys were flown. The majority of the offshore Polar Bears, 595 bears at 290 sightings, and most of the kill sites and polar bear tracks were recorded in 80-100% ice cover. The number of bears per kilometer increased substantially in >24% ice cover, with the highest number observed in 80-100% ice cover. This habitat use probably is related to the availability of seals, their primary prey. There were 328 bears (83 sightings) recorded on land, and most of them were associated with whale carcasses and bowhead whale subsistence harvest sites along the Alaskan Beaufort Sea coast.

Adaptive beamforming at very low frequencies in spatially coherent, cluttered noise environments with low signal-to-noise ratio and finite-averaging times

Realistic simulations with spatially coherent noise have been run in order to compare the performance of adaptive beamforming (ABF), inverse beamforming (IBF), and conventional beamforming (CBF) for the case of finite-averaging times, where the actual spatial coherence of the acoustic field, or covariance matrix, is not known a priori, but must be estimated. These estimation errors cause large errors in the ABF estimate of the directionality of the acoustic field, partly because ABF is a highly nonlinear algorithm. In addition, it is shown that ABF is fundamentally limited in its suppression capability at very low frequency (VLF), based on the sidelobe level of the conventional beampattern in the direction of the noise interferer [G. L. Mohnkern, "Effects of Errors and Limitations on Interference Suppression," NOSC Technical Document 1478, Naval Ocean Systems Center (1989)]. The simulations include a low-level plane wave signal of interest, a stronger noise plane wave interferer, and spatially random background noise. Both IBF and ABF performed significantly better than CBF, and IBF's performance was slightly better than ABF's performance. The performances of IBF and the ABF algorithm, the minimum variance distortionless response (MVDR) [A. H. Nuttall and D. W. Hyde, "Unified Approach to Optimum and Suboptimum Processing for Arrays," USL Report Number 992, Naval Underwater Systems Center, New London, CT (22 April 1969)] were recently compared independently [J. S. D. Solomon, A. J. Knight, and M. V. Greening, "Sonar Array Signal Processing for Sparse Linear Arrays," Defense Science and Technology Organization (DSTO) Technical Report (June 1999)] using measured data, with the result that IBF outperformed MVDR. This result is significant because MVDR requires orders of magnitude more processing power than IBF or CBF.

A m a t l a b(r) version of CHIEF (Combined Helmholtz Integral Equation Formulation) for solving acoustic radiation and scattering problems

The CHIEF program was developed during 1965–1988 at the Naval Ocean Systems Center. It was written in FORTRAN. The program uses the surface integral formulation of the Helmholtz equation to solve for acoustic pressure and velocity over a surface subject to surface geometry, boundary conditions, and incident field pressure on the surface. CHIEF uses a file interface to specify geometry, boundary conditions, etc., and writes its solutions for surface pressures to an output file. Thus, other programs are required for surface visualization and interpretation of results. Further, much of the original CHIEF FORTRAN code is devoted to bookkeeping imposed by machine limitations. As part of a larger modeling effort, CHIEF was ported to matlab. This makes the CHIEF methodology available as part of the matlab workbench approach to programming. Bookkeeping code that is no longer needed is discarded. Visualization tools are included as part of the new CHIEF environment. matlab functions are used where appropriate, combined with C++ code for speed when performing operations that are not vectorizable by matlab. The object-oriented features of matlab CHIEF are discussed as they apply to problem definition, visualization, and clarity and conciseness of programming. [Work supported by ONR 321 as Acoustic Measurement Methodology.]

Variation model for the radiation impedance of Class IV transducers III

Previously [H. C. Robinson and E. A. McLaughlin, J. Acoust. Soc. Am. 97, 3300(A) (1995)], the modal radiation impedance for a pair of Class IV transducers was calculated using variational methods. This model determines distinct self and mutual radiation impedance contributions between pairs of surface velocity modes, including the effects of element orientation, without requiring exact solutions to the equations of motion and boundary conditions. However, in order to model the total radiation impedance of the transducers, suitable methods for combining these modal impedances must be determined, which in turn requires that some estimate of the relative importance of each modal contribution be made. One method of determining the relative strengths is singular value decomposition [G. W. Benthien, Naval Ocean Systems Center Technical Report 1329, November 1989], which effectively allows one to determine the fluid-loaded resonances of the transducer and their associated eigenvectors. The relative magnitudes of these in-water modes will determine their importance in the total impedance. The results of this combination will be incorporated in a modified equivalent circuit which includes the effects of the ‘‘banana’’ mode. Calculations using this circuit will be made to existing equivalent circuit models as well as to experimental data.

M-layer: NPS version

M-layer is a FORTRAN program for computing the over-the-horizon propagation factor of an electromagnetic (EM) wave in a stratified atmosphere when ducting is present. The M-layer program developed by the Naval Ocean Systems Center (NOSC) has been substantially revised into a Naval Postgraduate School (NPS) version. The mode locating algorithm was rewritten to take advantage of local analyticity of the mode function. The exponential complex number representation was adopted to simplify multiplication and to improve accuracy when adding two complex numbers which nearly cancel each other. A consistency condition was formulated to assure accurate evaluation of the height-gain function. As a result, this NPS version executes faster with greater stability.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Tailoring Shipboard Environmental Specifications: Part III. Random Vibration

This article, the third in a three-part series, is extracted from Technical Document (TD 2071) published by the Naval Ocean Systems Center in April, 1991. Titled "Tailoring Shipboard Environmental Specifications, A Guide for Navy Program Managers," the document presents a compilation of shipboard environmental data measured over the years. The applicability of the data to the fleet of today is discussed. Methods of tailoring systems specifications and tests for the environment existing at given locations on a variety of naval ships are also included. The first article in the series (Journal of the IES, p. 25, March/April, 1992) included the Introduction, Temperature and Humidity, and Shock sections of TD 2071. The second article in the series (Journal of the IES, p. 27, May/June, 1992) covered the first part of the TD 2071 discussion of vibration. This article finishes the discussion of vibration and includes a "tailored" vibration requirement that a program manager might include in a procurement package for new shipboard systems.

Tailoring Shipboard Environmental Specifications: Part II. Single-Frequency Vibration

This article, the second in a three-part series, is extracted from Technical Document (TD 2071) published by the Naval Ocean Systems Center in April, 1991. Titled "Tailoring Shipboard Environmental Specifications, A Guide for Navy Program Managers," the document presents a compilation of shipboard environmental data measured over the years. The applicability of the data to the fleet of today is discussed. Methods of tailoring systems specifications and tests for the environment existing at given locations on a variety of Naval ships are also included. The first article in this series (Journal of the IES, p. 25. March, April, 1992) included the Introduction, Temperature and Humidity, and Shock sections of TD 2071. This article covers the first part of the TD 2071 discussion of vibration. The third article will finish the discussion of vibration and present a "tailored" vibration requirement that a program manager might include in a procurement package for new shipboard systems.

Observations of seismo-electromagnetic earthquake precursor radiation signatures along Southern Californian fault zones: Evidence of long-distance precursor ultra-low frequency signals observed before a moderate Southern California earthquake episode

Although questioned for a long time, there is accumulating growing evidence for the existence of detectable seismo-electromagnetic phenomena worldwide. California is geologically as well as seismically a unique region for studying these phenomena in depth; and, in particular, the southern California geologic province with a multitude of offshore and inland fault zones with San Diego in its center. At the Naval Ocean Systems Center Low Frequency Noise Laboratory, San Diego CA., we monitor 0.1–10 Hz ultra-low frequency (ULF) and 10–40 Hz extremely low-frequency (ELF) signals using mu-metal loaded multitum search coil sensors, as well as 10–100 kHz very low-frequency signals using large 1 m diameter loop antennas. We have observed precursor seismo-electromagnetic emissions of several earthquake events. In this paper, we report on observations of broadband ULF signals before and during the Upland quake of April 17, 1990 (Ms = 4.6), centered 200 km N of San Diego. The signals were detected with the vertically oriented search coil sensor and not with the horizontally oriented sensors, which suggests a disturbed ionosphere as the most likely source of these signals. The large prequake ULF activity, the rapid decay of ULF activity after the quake, and the absence of any geomagnetic storms indicate a good correlation of the ULF activity with the Upland quake. Although the exact mechanisms for coupling geologic activity to the ionosphere is not known, we cite a number of hypotheses concerning these mechanisms. Based on this succinct overview, an interpretation of our radio observations of seismic activity is presented and extended to earthquake precursor or predictor studies. We are in the process of expanding this research with the building of more monitoring stations and the improvement of our measurement, data collection, formatting, and data processing capabilities.

Broadband modeling and source localization of a PRN projector tow

A broadband ray model is used to simulate data from a deep water experiment (TAGEX 87) in which a pseudo random noise (PRN) source is towed past a 24‐element, bottom‐moored array. The source spectrum contains a series of evenly spaced lines from 60–100 Hz. Simulated shade plots of received spectrum level versus frequency and time exhibit excellent agreement with the data. A broadband matched field algorithm is used to localize the source in range as a function of time. The algorithm consists of matching the recorded cross spectrum R1R2* between two phones with simulated cross spectra S1S2* at a series of ranges. The correlations between recorded and simulated cross spectra are added coherently as a function of frequency to obtain the localization matrix entry: Lij = Σf[RliR2i*] [SljS2j*]*. Successful localizations of the PRN source are obtained at ranges from 0–30 km. [Work supported by Naval Ocean Systems Center, Code 733, under contract N00039‐88‐C‐0043‐1‐43.]

Echolocation signals of the smallest odontocetes

Echolocation signals of the smallest odontocetes, Cephalorhynchus commersonii, Cephalorhynchus hectori (genus Cephalorhynchus), Phocoenoides dalli, Phocoena phocoena, and Neophocoena phocoena (family phocoenidae) are compared with those of larger dolphins. Available data seem to indicate that two distinct classes of signals exist. Echolocation signals of Tursiops truncatus, Pseudorca crassidens, and Delphinapterus leucas studied at the Naval Ocean Systems Center have peak frequencies between 100‐120 kHz, with high amplitudes (210–225 dB re:1 μPa), short durations (50–70 μs), and wide bandwidths (30–40 kHz). The smallest odontocetes tend to emit signals having peak frequencies between 120 and 140 kHz, with low amplitudes (< 170 dB re: 1 μPa), long durations (170–430 μs) and narrow bandwidths (7–11 kHz). Double pulses are also emitted regularly by the smaller odontocetes and very infrequently by the larger dolphins. The signals used by the smaller animals may reflect an adaptation resulting from constraints associated with their small size and may also reflect differences in the generation mechanism. Some of the properties of high‐frequency, narrow‐bandwidth biosonar signals used by the smaller odontocetes will be discussed, along with comparative advantages and disadvantages of these signals.

ON DISEASE TRANSMISSION BETWEEN CETACEANS AND HUMANS

Marine Mammal ScienceVolume 7, Issue 2 p. 191-194 ON DISEASE TRANSMISSION BETWEEN CETACEANS AND HUMANS J. R. Geraci, J. R. Geraci Department of Pathology, Ontario Veterinary College, Guelph, Ontario, Canada N 1G 2W 1Search for more papers by this authorS. H. Ridgway, S. H. Ridgway Naval Ocean Systems Center, San Diego, California 92152.Search for more papers by this author J. R. Geraci, J. R. Geraci Department of Pathology, Ontario Veterinary College, Guelph, Ontario, Canada N 1G 2W 1Search for more papers by this authorS. H. Ridgway, S. H. Ridgway Naval Ocean Systems Center, San Diego, California 92152.Search for more papers by this author First published: April 1991 https://doi.org/10.1111/j.1748-7692.1991.tb00565.xCitations: 18AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume7, Issue2April 1991Pages 191-194 RelatedInformation

Graphing capabilities for CHIEF (combined Helmholtz integral equation formulation)

The computer program CHIEF [G. W. Benthien, D. Barach, and D. Gillette, “CHIEF Users Manual,” Naval Ocean Systems Center Report 920 (Sept. 1988)] is designed to obtain approximate solutions to exterior steady‐state acoustic radiation problems for surfaces of arbitrary shapes vibrating with a prescribed normal velocity. Being unable to view the shapes defined by CHIEF can lead to many difficult debugging problems as well as incorrect solutions. DISPLAY3D provides points as though the data were locations on a three‐dimensional surface on a solid and a description of how these points are connected. DISPLAY3D has several options that make it a versatile package. The code permits the user to change the orientation from which the data are viewed. DISPLAY3D also provides the option of viewing the direction of the normal velocity vector as defined by CHIEF. These options, as well as others, will be explained in detail. [Work supported by ONT.]

Horizontal variability of the marine boundary layer structure upwind of San Nicolas Island during program FIRE, 1987

The Naval Ocean Systems Center airborne platform was utilized during research project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) to investigate the low level horizontal variability ofthe marine boundary layer structure. Flights were made near San Nicolas Island to determine how well island-based measurements represent upwind open ocean conditions. The meteorological profiles revealed differences between the open ocean conditions and those taken near the island. The observed differences were not uniquely tied to a specific island effect since the upwind fluctuations bounded the island measurements. A higher concentration of surface-based aerosols existed around the island, and if the resulting extinction parameter were used to model open ocean ship-to-ship electro-optical propagation conditions, errors would result. This is not so for vertical ship-to-satellite propagation since the total integrated vertical optical depths as measured at the island are not significantly affected by the shallow surface-based aerosol layer. Sea surface and cloud top temperatures taken near the island are not always representative of those observed upwind.

Laboratory measurements of optical beams in young sea ice

The optical properties of young sea ice (&lt;20 cm thick) have been measured in the Naval Ocean Systems Center Ice Optics Lab. Measurements of the upwelling irradiance from the ice surface as a function of distance from the center of the beam spot (r in cm) were performed. The irradiance distributions were transformed to find the modulation transfer function (MTF) and beam spread function (BSF) as a function of ice thickness. The BSF could be approximated by BSF(r, z) = exp(−kBz) exp(−r2/2 〈r2〉), with kB = 0.404 cm−1 and 〈r2〉½ = 0.105 z1.41 cm, where z is ice thickness (in cm). Angular radiance above the ice surface, resulting from a laser beam entering the ice from below, was measured as a function of ice thickness for a specific growth condition. The angular field followed a function of L(θ, z) = L(0, z)cosn(θ), with n = 8.1 z0.71, while the peak value followed a Beer’s law decay of the form L(0, z) = L(0, 0)exp(−0.514z).

The Quantification of Interoperability

ABSTRACTJCS Pub 1 defines interoperability as “The ability of systems, units or forces to provide services to and accept services from other systems, units or forces and to use the services so exchanged to enable them to operate effectively together.” With JCS Pub 1 as a foundation, interoperability of systems, units or forces can be factored into a set of components that can quantify interoperability. These components are: media, languages, standards, requirements, environment, procedures, and human factors. The concept described in this paper uses these components as an analysis tool to enable specific detailed analyses of the interoperability of BFC3 systems, units, or forces for the purpose of uncovering and resolving interoperability issues and problems in the U.S. Navy, Joint, and Allied arenas. Also, as a management tool, the components can help determine potential interoperability characteristics of future U.S. Navy BFC3 systems for compliance with battle force systems architectures.The approach selected for the quantification of interoperability was the development of a set of measures of performance (MOPs) and measures of effectiveness (MOEs). The MOPs/MOEs were integrated with a candidate set of components, which were used to partition the totality of interoperability into measurable entities.The methodology described employs basic truth table theory in conjunction with logic equations to evaluate the interoperability components in terms of MOPs that were aggregated to MOEs. It is believed that this concept, although elementary and based on fundamental principles, represents an operationally significant approach rather than a theoretical approach to the quantification of interoperability.The vehicle used as a means to measure the MOPs and MOEs was the Research Evaluation and Systems Analysis (RESA) computer modeling and simulation capability at the Naval Ocean Systems Center (NOSC), San Diego, Calif. Data for the measurements were collected during a Tactical Information Management Exercise (TIMEX) in August 1987. The data consisted of printouts from computer data bases plus data collected by human observers.It is hypothesized that subsequent repeated exercises will yield a sufficient number of meaningful measurements. These measurements may lead to the development of frequency distribution curves representing the degree to which each interoperability component was achieved. These curves will in turn be used to derive some probability function [P(I)] that empirically describes the degree of interoperability that could be achieved. The benefit of this approach is that complex interoperability problems can be partitioned into a smaller subset of problems that can be more easily managed and/or resolved. Also it provides the potential means to obtain a probabilistic measure of how often, operationally, a desired level of interoperability could be achieved.

Surfacing Behavior and Ventilation in Free-Ranging Dolphins

Journal Article Surfacing Behavior and Ventilation in Free-Ranging Dolphins Get access Clifford A. Hui Clifford A. Hui Code 521, Naval Ocean Systems Center, San Diego, CA 92152 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 70, Issue 4, 27 November 1989, Pages 833–835, https://doi.org/10.2307/1381722 Published: 27 November 1989 Article history Received: 23 June 1988 Accepted: 01 February 1989 Published: 27 November 1989

A role model for electromagnetic systems design

The authors discuss the antenna test range at the US Naval Ocean Systems Center, which provides solutions to some formidable electromagnetics problems on ships. They describe the measurement approach; the pattern range, a 160 ft diameter ground plane constructed of prestressed concrete covered with a very thin coating of lead; the impedance range, which has a subterranean instrument room that houses the measurement equipment and personnel during the test; and the time-domain measurement range. The authors then examine computer modelling of antennas and analysis of the EMC (electromagnetic compatibility) problem. The modelling approach as presented is not limited to ships; it can work for power lines, buildings, and even mountains.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>