Robert Spindel

• Professor
• Director and Professor Emeritus at University of Washington

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

For monostatic sonar using long pulsed tone signals, the problem of evaluating the spectrum of reverberation due to sound wave scattering by a rough sea surface is solved. Relatively simple computational schemes are proposed, which make it possible (i) to transform the three-dimensional spectra of surface waves to the frequency-angular characterist...

This presentation is devoted to the investigation of sound scattering by wind waves in case of propagation in shallow water (∼20 m) at distances of 100–1000 m and frequencies of 1–5 kHz. We consider several models and direct numerical calculation based on small perturbation theory that allows reconstruction of the reverberation levels when given kn...

This presentation considers the main schemes of calculating the frequency and angular characteristics of reverberation of low?frequency cw signals in shallow water caused by scattering from a rough, wind?driven surface. Experimental and calculated data are given in order to display directivity patterns and levels of the reverberation signals in bot...

This research is aimed at providing more reliable predictions of the characteristics of reverberation as a function of frequency and range, as well as propagation path and wind wave characteristics. A theoretical model is derived and is compared to experimental results which consist of simultaneous acoustic and wind wave characteristics measurement...

The SilverMedal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

The forward scattering of sound by a moving inhomogeneity can be observed when the inhomogeneity intersects a stationary path between an acoustic source and a receiving array. The scattered field is modeled as a weak perturbation of the direct signal when the inhomogeneity is near the direct path. Often the scattered field is masked by fluctuations...

Large-scale, range- and depth-averaged temperatures in the North Pacific Ocean were measured by long-range acoustic transmissions over the decade 1996-2006. Acoustic sources off central California and north of Kauai transmitted to receivers throughout the North Pacific. Even though acoustic travel times are spatially integrating, suppressing mesosc...

In this paper, we address the problem of detecting an inhomogeneity in shallow water by observing changes in the acoustic field as the inhomogeneity passes between an acoustic source and vertical line array of receivers. A signal processing scheme is developed to detect the perturbed field in the presence of the much stronger primary source signal,...

Large‐scale temperatures in the North Pacific were measured by long‐range acoustic transmissions from 1996–2006. Acoustic sources off California and Kauai transmitted to receivers distributed throughout the North Pacific from 1996–1999. Kauai transmissions continued from 2002–2006. Acoustic travel‐time data are inherently integrating. This averagin...

With several years of long‐range (several Mm) acoustic propagation data obtained during the Acoustic Thermometry of Ocean Climate (ATOC) and North Pacific Acoustic Laboratory (NPAL) projects, the seasonal cycle of oceantemperature in the North Pacific can be examined. Acoustic transmissions have been made from a source located off the northern Cali...

The NPAL98 experiment offered a unique opportunity to study horizontal coherence because of the deployment of a billboard array. The billboard consisted of five vertical line arrays with a 3600‐m horizontal aperture listening to a 75‐Hz acoustic signal 3500 km away. Original estimates of horizontal coherence were complicated by the bottom‐interacti...

A series of long-range acoustic propagation experiments have been conducted in the North Pacific Ocean during the last 15 years using various combinations of low-frequency, wide-bandwidth transmitters and horizontal and vertical line array receivers, including a 2-dimensional array with a maximum vertical aperture of 1400 m and a horizontal apertur...

We examine statistical and directional properties of the ambient noise in the 10-100 Hz frequency band from the NPAL array. Marginal probability densities are estimated as well as mean square levels, skewness and kurtoses in third octave bands. The kurotoses are markedly different from Gaussian except when only distant shipping is present. Extremal...

In 1998 –1999, a comprehensive low-frequency long-range sound propagation experiment was carried out by the North Pacific Acoustic Laboratory NPAL. In this paper, the data recorded during the experiment by a billboard acoustic array were used to compute the horizontal refraction of the arriving acoustic signals using both ray-and mode-based approac...

Predictions of transverse horizontal spatial coherence from path integral theory are compared with measurements for two ranges between 2000 and 3000 km. The measurements derive from a low-frequency (75 Hz) bottom-mounted source at depth 810 m near Kauai that transmitted m-sequence signals over several years to two bottom-mounted horizontal line arr...

The statistics of low-frequency, long-range acoustic transmissions in the North Pacific Ocean are presented. Broadband signals at center frequencies of 28, 75, and 84 Hz are analyzed at propagation ranges of 3252 to 5171 km, and transmissions were received on 700 and 1400 m long vertical receiver arrays with 35 m hydrophone spacing. In the analysis...

Large-scale, depth-averaged temperatures have been measured by long-range acoustic transmissions in the North Pacific Ocean for the past nine years. Acoustic sources located off central California and north of Kauai transmitted to receivers distributed throughout the North Pacific from 1996 through 1999 during the Acoustic Thermometry of Ocean Clim...

The Asian Seas International Acoustics Experiment (ASIAEX) included two major field programs, one in the South China Sea and the other in the East China Sea (ECS). This paper presents an overview of research results from ASIAEX ECS conducted between May 28 and June 9, 2001. The primary emphasis of the field program was shallow-water acoustic propag...

Over the last 15 years a series of long‐range acoustic propagation experiments has been conducted in the North Pacific Ocean using various combinations of low‐frequency, wide bandwidth transmitters and horizontal and vertical line array receivers, including a two‐dimensional array with a maximum vertical aperture of 1400 m and a horizontal aperture...

The ocean is a fluid waveguide, bounded by the air-sea surface above and the topography of the bottom below, through which sound propagates according to a scalar wave equation. At the present time, the acoustic effects of the sea surface, bottom, and volume still are incompletely known and constitute the limiting factors in our understanding of sou...

Acoustic measurements of large-scale, depth-averaged temperature continue in the North Pacific as a follow on to the Acoustic Thermometry of Ocean Climate (ATOC) project. An acoustic source located just north of Kauai transmits six times per day at four-day intervals to six receivers to the east at 1-4 Mm ranges and one receiver to the northwest at...

A pilot experiment was conducted in the Sea of Japan (also called the East Sea) in September-October 1999, to assess the possibility of using acoustic tomographic techniques for monitoring water mass structure and dynamics. Acoustic m-sequence signals at various frequencies between 250 and 634 Hz were transmitted from bottom-mounted acoustic source...

Summary form only given. Acoustic measurements of large-scale, depth-averaged temperatures are continuing in the North Pacific Ocean in a follow-on to the Acoustic Thermometry of Ocean Climate (ATOC) project. Long-range acoustic transmissions resumed in January 2002 from a low-frequency acoustic source located north of Kauai to U.S Navy receivers d...

At long range, the low order acoustic modes constitute some of the most energetic arrivals. Prior to using these signals in tomographic or matched field inversions, it is important to understand their fluctuation statistics. Long vertical line arrays installed as a part of the Acoustic Thermometry of Ocean Climate (ATOC) experiment provided a uniqu...

An experimental investigation of the horizontal refraction of acoustic signals traversing a distance of about four thousand kilometers in the ocean is given. The signals were recorded with the two-dimensional antenna array of the North Pacific Acoustic Laboratory (NPAL) over a year. The horizontal angle of refraction as a function of time was obtai...

In late January and early February 1991, an international team will conduct an experiment to test the possibility of measuring global warming in the world's oceans. The goal is to provide early indications of warming caused by the so-called greenhouse effect, the atmospheric buildup of COâ and other gases. The method is based on the principle that...

The goal of this project was to bring together a unique set of observational and modeling opportunities that existed within the partnering institutions and agencies to monitor the North Pacific Ocean with the ultimate purpose of improving weather and climate forecasts over the North American continent, The objective was to observe, describe, and un...

The "invariant parameter" called "beta" is often useful for describing the acoustic interference pattern in a waveguide. For some shallow water waveguides, the measured acoustic intensity might contain contributions from several propagating acoustic modes. For each pair of these modes, a different value for the waveguide invariant might apply. If t...

This lecture traces the history of acoustical oceanography from its beginnings during WWII (although it was not called Acoustical Oceanography at the time) to the present. We describe how during the Cold War the U.S. and Soviet Navy’s efforts to improve the performance of their torpedoes and sonars revealed unknown ocean features and processes. We...

One of the main objectives of the NPAL experiment is to investigate the horizontal refraction and coherence of the acoustic wave fronts at long range. Given time series of acoustic arrival times and angles of resolved ray arrival arrivals, a detailed look at the acoustic wave fronts is possible. First and second order statistics (density functions...

While the NPAL array was primarily deployed to examine the spatial coherence of the Hawaii source, it is also a rich data set for ambient noise studies. Shipping noise, earthquakes and biologics all have been identified in the NPAL data. Moreover, ambient noise coherence is the primary issue in maximizing the SNR output of a sonar system. The first...

A comprehensive, long‐range sound propagation experiment was carried out with the use of the billboard acoustic array of the North Pacific Acoustic Laboratory (NPAL) in 1999. The antenna consisting of five vertical line arrays was deployed near a California coast and received broadband acoustic signals transmitted from Hawaii over a distance of abo...

Receptions of long‐range acoustic transmissions by deep hydrophone arrays in the Pacific and Atlantic often have ‘‘ray‐like’’ arrivals that occur in the shadow zone of the predicted time front. These ‘‘ray‐like’’ arrivals can frequently be identified with the cusps of the predicted time front, but the receivers are up to 750 m below the depth of th...

The low‐order modes constitute some of the most energetic arrivals at long ranges. Understanding fluctuations of these mode arrivals is crucial to their use as observables in matched field processing and tomography. Both simulated and experimental data indicate that at megameter ranges, the low modes have complex arrival patterns due to internal‐wa...

Low‐frequency (75‐Hz) acoustic signals were repeatedly transmitted over a 1 year period and sampled vertically (with up to a 1400‐m aperture) and horizontally (with a 3600‐m cross‐range aperture) by a distant bill‐board array (3900‐km range) as described by the NPAL Group. The data are complicated by the fact that the sound interacts with the botto...

As part of the North Pacific Acoustic Laboratory project, ambient sound data from 1994 to the present has been collected. Long‐term averages of these data from a receiver on the continental slope west of Point Sur, CA, are compared to earlier measurements made at the same site over 1963–1965 by Wenz [Wenz, J. Underwater Acoust. 19 (1969)]. The leve...

Acoustic transmissions on basin scale ranges are being used to determine depth‐dependent temperature variability. With travel time being the primary observable, stationary sources and nearly stationary receivers are experimental requirements. This has led to the use of bottom‐mounted sources and receivers to reduce travel time variability. The NPAL...

The North Pacific Acoustic Laboratory program augmented the existing ATOC acoustic network with a sparse, two‐dimensional receiving array installed west of Sur Ridge, California, from July 1998 through June 1999, to receive transmissions from the 75‐Hz ATOC source north of Kauai. The NPAL array consisted of four 20‐element vertical arrays, each wit...

The North Pacific Acoustic Laboratory program augmented the existing ATOC acoustic network with a sparse, two‐dimensional receiving array installed west of Sur Ridge, CA, close to an existing U.S. Navy SOSUS array, during July 1998 to receive transmissions from the 75‐Hz ATOC source north of Kauai. The NPAL array consisted of four 20‐element vertic...

The panel was chartered to review and assess efforts to optimize manning on surface ships. This included the review of previous studies of the subject, current programs within the U.S. and foreign navies, and relevant technology efforts. The panel was also asked to identify technology opportunities and to recommend changes in procedures and policy...

Broadband acoustic signals were transmitted during November 1994 from a 75-Hz source suspended near the depth of the sound-channel axis to a 700-m long vertical receiving array approximately 3250 km distant in the eastern North Pacific Ocean. The early part of the arrival pattern consists of raylike wave fronts that are resolvable, identifiable, an...

During the Acoustic Engineering Test (AET) of the Acoustic Thermometry of Ocean Climate (ATOC) program, acoustic signals were transmitted from a broadband source with 75-Hz center frequency to a 700-m-long vertical array of 20 hydrophones at a distance of 3252 km receptions occurred over a period of-six days. Each received pulse showed early identi...

Acoustic signals transmitted from the ATOC source on Pioneer Seamount off the coast of California have been received at various sites around the Pacific Basin since January 1996. We describe data obtained using bottom-mounted receivers, including US Navy Sound Surveillance System arrays, at ranges up to 5 Mm from the Pioneer Seamount source. Stable...

Measurements of basin-scale acoustic transmissions made during the last four years by the Acoustic Thermometry of Ocean Climate (ATOC) program have allowed for the study of acoustic fluctuations of low-frequency pulse propagation at ranges of 1000 to 5000 km. Analysis of data from the ATOC Acoustic Engineering Test conducted in November 1994 has re...

The quality of ocean acoustic travel‐time measurements depends on the coherence as well as the bandwidth of the signal. Ocean internal‐wave fields are thought to be responsible for the loss of coherence in low‐frequency acoustic signals. If the coherence bandwidth is less than the signal bandwidth, it is possible to consider sub‐bands of the signal...

The Acoustic Thermometry of Ocean Climate (ATOC) sound sources are located 8 miles north of Kauai, Hawaii and 50 miles west of Half Moon Bay, California. The sources are connected to shore‐based electronics by undersea coaxial cables. Recent modifications in the shore‐based electronics have permitted the ATOC transducers to serve as hydrophones as...

Two sets of acoustic measurements made by the Applied Physics Laboratory, University of Washington, as part of the August 1996 joint U.S.-China Yellow Sea Experiment are analyzed. One set consists of broadband propagation measurements for which explosive TNT sources were used. These data were reduced to estimates of calibrated transmission loss, wh...

The ultimate limits to the coherence of long-range acoustic transmissions are imposed by ocean processes, including internal waves, mesoscale variability, interior ocean boundaries (fronts), and bathymetric scattering. An understanding of the effects of these processes on acoustic signals is crucial to the use of acoustic remote sensing methods for...

The Yellow Sea represents a natural laboratory for the study of shallow water acoustic propagation as influenced by a strong summer thermocline, energetic internal wave fields, and a seabed considered relatively range independent. In this paper results of transmission loss measurements obtained in the Yellow Sea, during the joint China?U.S. Yellow...

Comparisons of gyre-scale acoustic and direct thermal measurements of heat content in the Pacific Ocean, satellite altimeter measurements of sea surface height, and results from a general circulation model show that only about half of the seasonal and year-to-year changes in sea level are attributable to thermal expansion. Interpreting climate chan...

Approximately 15 months of data are now available from the 75?Hz ATOC transmissions from the Pioneer Seamount off Half Moon Bay, CA to horizontal arrays at 11 U.S. Navy horizontal arrays in the northeast Pacific, two vertical arrays, one near Hawaii and the other near Kiritimati (Christmas) Island. The data demonstrate that ocean basin temperatures...

Simultaneous observations of internal wave activity and acoustic wave propagation in 70‐m water in the Yellow Sea were made in the late summer of 1996. The primary objective of this experiment was to validate the predicated modal coupling and fluctuations induced by shallow‐water internal waves. The Yellow Sea provides an ideal environment for such...

transmitted to receivers distributed throughout the northeast and north central Pacific. The acoustic travel times are inherently spatially integrating, which suppresses mesoscale variability and provides a precise measure of ray-averaged temperature. Daily average travel times at 4-day intervals provide excellent temporal resolution of the large-s...

Acoustic‐ray travel‐time measurements at 75 Hz are being used in the ATOC tomography experiment to infer important oceanographic variables such as heat content, currents, etc. The accuracy with which these measurements can be made is limited by the small‐scale structure of the ocean (such as internal waves). Examined in detail, rayfronts show varia...

Simultaneous observations of internal wave activity and acoustic wave propagation in 70 m water in the Yellow Sea were made in the late summer of 1996. The objective of the experiment was to validate the predicated modal coupling and resulting fluctuations and alterations in propagation loss induced by shallow?water internal waves. Propagation over...

For the ATOC program two dense vertical?line arrays (VLA) centered on the sound?channel axis and located off of the islands of Hawaii and Christmas, and several bottom?mounted horizontal arrays located around the North Pacific have recorded basin?scale acoustic transmissions emminating from a bottom mounted source located on Pioneer Seamount since...

ATOC signals transmitted from the Pioneer Seamount acoustic source have been received on hydrophone arrays located throughout the North Pacific Basin since the beginning of 1996. Propagation times can be used to infer average temperature (or heat content) variability because the speed of sound changes with temperature. The time series of resolved?r...

The ATOC acoustic feasibility network became functional in December 1995 following the installation of an acoustic source on Pioneer Seamount approximately 50 nm off the coast of Northern California. The current effort is part of the Marine Mammal Research Program Pilot Study. This paper describes the acoustic network of sources and receivers, incl...

Oceanacoustic tomography has become a highly developed tool for observing the ocean’s interior. It has been used in the Atlantic, Pacific, and Indian Oceans, the Mediterranean, Greenland, and Norwegian Seas, and in a number of smaller bodies of water including Puget Sound. There are active oceantomography research programs in the U.S., France, Germ...

Moored thermistor, hydrographic, and tomographic measurements have been combined using least-squareisn verse methods to study the evolution of the 40 km and larger three-dimensionatel mperature field in the Greenland Sea during winter 1988-89. In February, the sub-surface temperature maximum at around 2 00-m depth disappears over a large area. Uppe...

A low-frequency acoustic source suspended from R/P FLIP approximately 340 nautical miles WSW of San Diego transmitted to receivers 90 to 10 000 km distant during the Acoustic Engineering Test of the Acoustic Thermometry of Ocean Climate (ATOC) Program. The source was sus-pended for 7 days during November 1994 near the depth of the sound channel axi...

A nonperturbative inversion was performed of acoustic tomographymeasurements made in the northeastern Pacific Ocean in July 1989, in which acoustic transmissions from a 250‐Hz broadband source located near the sound‐channel axis were recorded at a long vertical array of hydrophones 1000 km away. In contrast with a conventional inversion, this nonpe...

Broadband acoustic signals were transmitted from a moored 250-Hz source to a 3-km-long vertical line array of hydrophones 1000 km distant in the eastern North Pacific Ocean during July 1989. The sound-speed field along the great circle path connecting the source and receiver was measured directly by nearly 300 expendable bathythermograph (XBT), con...

The ATOC demonstration experiment involves the installation of two fixed acoustic sources, one near Hawaii and the other near Pt. Sur, California, the instrumentation of several Navy receiver systems in the North Pacific, and the deployment of autonomous and cabled‐to‐short vertical arrays. Extension of the experiment to other oceans may require th...

Moving Ship Tomography is a method of obtaining high-resolution, nearly synoptic three-dimensional maps of the ocean temperature field over large areas. Acoustic travel times along a multitude of paths crossing at many different angles are measured and then the sound speed (temperature) field is reconstructed in a manner analogous to a medical comp...

The Greenland Sea Ocean Acoustic Tomography Experiment was conducted during 1988-89, as one component of the international Greenland Sea Project, to study deep water formation and the response of the gyre to variations in wind stress and ice cover. Six acoustic transceivers moored in an array 200-km across transmitted to one another at four hour in...

Broadband acoustic signals transmitted from a moored 250-Hz source to a 3-km-long vertical line array of hydrophones 1000 km distant in the north central Pacific Ocean were used to determine the amount of information available from tomographic techniques used in the vertical plane connecting a source-receiver pair. A range-independent, pure acousti...

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A 1000-km acoustical transmission experiment has been carried out in the North Pacific, with Pulses broadcast between a moored broadband source (250-Hz center frequency) and a moored sparse vertical line of receivers. Two data records are reported: a period of 9 days at a pulse rate of one per hour, and a 21 -h period on the seventh day at six per...

Moving ship tomography measures acoustic travel times between transmitters moored above the ocean floor and hydrophones on a cable tethered to a ship. The authors consider a Kalman filter that determines the location of a subarray of the hydrophones near the end of the cable. A long-baseline tracking system, consisting of floating buoys and the shi...

In late January and early February, 1991, 57‐Hz acoustic signals were transmitted underwater from Heard Island in the southern Indian Ocean to receiving sites worldwide. The experiment was designed to test the feasibility of using underwater acoustic signals to measure warming of the world’s oceans. The idea is based on the fact that the speed of s...

The concept of time-of-flight acoustic tomography to measure the ocean mesoscale (order 100 kilometers) was formulated just over ten years ago. Since then, there has been an evolving (and expanding) research program involving at least a half a dozen institutions and many more scientists and engineers to test and evaluate the utilituy of the idea an...

The techniques and instruments used in acoustic tomography of the oceans are surveyed, and results are summarized. Sections are devoted to theoretical studies and numerical simulations (mesoscale mapping, vertical-slice tomography, flow imaging, and nonlinear bias), series of tomographic experiments, analyses to identify global changes, and outstan...

Acoustic travel times in the ocean are sensitive both to the mean sound speed field and to high-wavenumber ocean features with wavelengths corresponding to ray loop “wavelengths” and their harmonics (70 km and smaller). The quasi-sinusoidal rays can be thought of as taking a partial Fourier transform of the sound speed field (Cornuelle and Howe, 19...

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Oceanographers have borrowed a technique from physicians for studying deep-sea currents and temperatures. The method is tomography. Instead of X rays, researchers use sound to create three-dimensional images of the waters that cover 70 percent of the earth's surface and strongly influence its climate. The paper describes how sound travels in the se...

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In this paper, data from a Gulf Stream tomographic experiment carried out in October 1984 are analyzed. The experiment used acoustic sources and receivers bottom mounted beneath the stream to measure Gulf Stream dynamics. However, due to an unfortunate electronic malfunction of the source, only 2 days of acoustically measured travel time data are a...

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During the 1984 Marginal Ice Zone Experiment (MIZEX '84), a 224-Hz center frequency acoustic tomography sound source was deployed off Spitsbergen, Norway, in 1200 m of water. Over the course of 10 days it transmitted hourly signals that were recorded by receivers at two locations, one moving with the ice pack and the other stationary. The main purp...

The travel times of acoustic pulses transmitted in opposite directions over a 300-km distance in mid-ocean have been used to measure the fields of sound speed and absolute water velocity with mesoscale resolution. The experiment, which took place west of Bermuda during August and September 1983, consisted of transceivers on two moorings that sent a...

Ocean acoustictomography is a method for remotely sensing deterministic and stochastic variations in the oceansound speed field. The fundamental tomographic measurement is sound speed, and therefore tomography directly provides acoustic propagationmodels with this essential, first‐order, environmental information. In one form or another the various...

Ocean acoustic tomography is a technique for observing the dynamic behavior of ocean processes by measuring the changes in travel time of acoustic signals transmitted over a number of ocean paths. The travel time varies in proportion to the magnitude of the average sound speed and current along each path. The latter quantities are estimated using m...

By simultaneously transmitting acoustic pulses in opposite directions between two points in midocean, one can separate the effects of ocean currents on acoustic propagation from the effects of sound-speed structure. Reciprocal acoustic transmissions can therefore be used to measure ocean currents. Acoustic transceivers have been designed and built...

In order to assess the possibility of performing ocean acoustictomography in the marginal ice zone (MIZ), a 224?Hz center frequency, phase?encoded acoustic source was deployed in the Greenland Sea as part of MIZEX 84. The source was moored in the near?surface sound channel at a depth of 175 m. It transmitted hourly signals designed to test acoustic...

A field test of ocean acoustic tomography was conducted in 1981 for a two month period in a 300 km square at 26°N, 70°W in the North Atlantic (just south of the MODE region). Nine acoustic deep-sea moorings with sea floor transponders for automated position keeping and with provisions for precise time keeping were set and recovered. From the measur...

This paper addresses acoustic signal processing issues that have arisen in designing systems to measure the sound speed and current fields of the ocean using time-of-flight acoustic tomography. The systems are based on a scheme first proposed by W. Munk and C. Wunsch in 1979, who suggested that dynamic ocean processes could be observed by measuring...

This is the final report of Contract N00014-77-C-0196 between the Woods Hole Oceanographic Institution and the Office of Naval Research for the contract period 1 January 1977 to 28 February 1983. This contract supported a broad program of research and development in underwater acoustics related to present and future Navy systems and requirements. T...

Phase-coded signals with 60 rms resolution were transmitted twice weekly for several months from acoustic sources at ∼2000 m depth in the Sargasso Sea to three bottom-mounted receives designed as West, East, and North stations at ranges approximately between 1000 and 2000 km. The transmission paths to West and East stations were entirely in the Sar...

The ocean is a fluid waveguide through which sound propagates according to the scalar wave equation $${{\text{D}}^2}{\text{p = }}{{\text{c}}^{\text{2}}}{\nabla ^2}{\text{p}}$$ (1) In this form p is the acoustic pressure perturbation, c is the speed of sound, and the operator $${\text{D}} \equiv \frac{\partial }{{\partial {\text{t}}}} + \underset{\r...

A test ocean acoustic tomography experiment was conducted in the southern North Atlantic during 1981. Travel time variations of pulse-like signals transmitted between moored acoustic sources and receivers separated by hundreds of kilometers were used to image the intervening sound speed field. Intelligent sources, receivers, mooring positioning mon...

Over the past decade oceanographers have become increasingly aware of an intense and compact ocean 'mesoscale' eddy structure (the ocean weather) that is superimposed on a generally sluggish large-scale circulation (the ocean climate). Traditional ship-based observing systems are not adequate for monitoring the ocean at mesoscale resolution. A 1981...

Preliminary results from a 1981 test ocean acoustic tomography experiment are presented. The system, deployed in the southern North Atlantic, consisted of four moorings with acoustic sources and five moorings with acoustic receivers in an approximately 300 km square array centered at 26 °N, 70 °W. Travel time variations of pulse-like signals transm...

A phase‐coded signal with 64‐ms resolution was transmitted at 10‐min intervals for a 19‐day period over two ∠300‐km ranges. The acoustic source was moored at 2000‐m depth northwest of Bermuda. One receiver was moored at 2000‐m depth to the northeast of the source and the other receiver was bottom mounted at ∠1000‐m depth near Bermuda. The large (∠0...