J.F. Lynch

J.F. Lynch
Woods Hole Oceanographic Institution | WHOI

PhD

About

456
Publications
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Publications

Publications (456)
Article
The Gold Medal is presented in the spring to a member of the Society, without age limitation, for contributions to acoustics. The first Gold Medal was presented in 1954 on the occasion of the Society's Twenty-Fifth Anniversary Celebration and biennially until 1981. It is now an annual award.
Article
Crossing internal wave trains are commonly observed in continental shelf shallow water. In this paper, we study the effects of crossing internal wave structures on three-dimensional acoustic ducts with both theoretical and numerical approaches. We show that, depending on the crossing angle, acoustic energy, which is trapped laterally between intern...
Article
Three-dimensional (3D) underwater sound field computations have been used for a few decades to understand sound propagation effects above sloped seabeds and in areas with strong 3D temperature and salinity variations. For an approximate simulation of effects in nature, the necessary 3D sound-speed field can be made from snapshots of temperature and...
Article
Full-text available
Gradients of heat and salt affect the propagation of sound energy in the ocean. Anticipated changes in oceanic conditions will alter thermohaline conditions globally, thus altering sound propagation. In this context, we examine changes in shallow-water propagation. Because these waters are close to the surface, they will be the earliest to change a...
Article
Full-text available
The variability of the interference pattern of a narrow-band sound signal in a shallow water waveguide in the horizontal plane in the presence of horizontal stratification, in particular due to linear internal waves, is studied. It is shown that lines of constant phase (a phase front) and lines of constant amplitude/envelope (an amplitude front) fo...
Chapter
This chapter discusses ocean acoustics in “shallow water,” which may be taken to be the continental shelf region between the beach/shore and the continental shelf break (including the latter). Bathymetrically, this is generally from 0 to 200 m water depth. Both low- and high-frequency acoustics are considered. The continental shelf has very complex...
Article
One of Ira Dyer’s seminal contributions to underwater acoustics was in the understanding of acoustic intensity fluctuations. In particular, the 5.6 dB intensity fluctuation of a large number of interfering narrowband multipaths, which is often informally referred to as “the Dyer number”, is a robust and well know effect. In shallow water, a number...
Article
In this paper, we present a short retrospective look at the evolution of acoustical, optical, and related measurements of sediment transport, bottom stress, and bottom bedforms over the past quarter century, using our programs at the Woods Hole Oceanographic Institution as a “representative sample.” Results from the High Energy Benthic Boundary Lay...
Article
The accuracy of oceansound propagationmodeling depends on properly representing the environment. The water column portion of this has phenomena and features that are time- and space-dependent, covering a huge range of scales. Nonlinear internal gravity waves (nonlinearinternal waves, NIW) in shallow areas are important features that are moving, evo...
Article
Underwater sound propagation in an oceanic waveguide can be influenced by environmental fluctuations on the boundaries at the sea surface and the sea floor and also in the ocean interior. These fluctuations can in fact cause three-dimensional acoustic propagation and scatteringeffects, especially when the horizontal/azimuthal gradients of the fluct...
Article
Full-text available
Analyses of fluctuations of low frequency signals (300 ± 30 Hz) propagating in shallow water in the presence of nonlinear internal waves (NIWs) in the Shallow Water 2006 experiment are carried out. Signals were received by a vertical line array at a distance of ∼20 km from the source. A NIW train was moving totally inside of the acoustic track, and...
Article
Shallow water (coastal) acoustics has been a topic of great interest over quarter century, both from the point of view of learning coastal oceanography and of learning coastal acoustics. Indeed, the two are difficult to separate. In this talk, the research done at the Woods Hole Oceanographic Institution (very often in collaboration with other inst...
Article
The process of publishing a paper in JASA involves many people and several process components. The authors, reviewers, Associate Editors, Publication Office personnel, and our AIPP publishers all play their parts and interact to produce any paper that is eventually published. In this talk, the various components of the publication process will be e...
Article
A dichotomy between depth penetration and resolution as a function of sonar frequency, draw resolution, and beam spread challenges fish target classification from sonar. Moving high-frequency sources to depth using autonomous underwater vehicles (AUVs) mitigates this and also co-locates transducers with other AUV-mounted short-range sensors to allo...
Article
A method for observing acoustic scattering due to reflection/refraction by a fish aggregation and absorption caused by sound propagation through a fish aggregation using autonomous underwater vehicles (AUVs) is presented in this paper, and the merits and challenges of the method are discussed. Results from an experiment conducted off Cape Hatteras,...
Article
In this editorial, the Editor-in-Chief of the Journal of the Acoustical Society of America gives a brief overview of the present status of the Journal, emphasizing the events that have occurred over the past one and one half years. Topics addressed include: (1) The recent transition to the Editorial Manager peer review system, (2) new features that...
Article
Full-text available
We propose a method for determining the effective parameters of the upper marine sediment layer on extended tracks from the spectra of wideband signals in conditions of hydrodynamic variability. As an example, we consider the Shallow Water 2006 experiment on the Atlantic shelf of the United States, which used signals with a band of 300 ± 30 Hz rece...
Article
The goal of timely and accurate acoustics modeling in the ocean depends on accurate environmental input information.Acoustic propagationmodeling has improved to the point of possibly being ahead of ocean dynamical modeling from the standpoint that some significant ocean features having strong acoustic effects are not faithfully reproduced in many m...
Article
During the Shallow Water Acoustic Experiment 2006 (SW06) conducted on the New Jersey continental shelf in the summer of 2006, detailed measurements of the ocean environment were made along a fixed reference track that was parallel to the continental shelf. The time-varying environment induced by nonlinear internal waves (NLIWs) was recorded by an a...
Article
The Distinguished Service Citation is awarded to a present or former member of the Society in recognition of outstanding service to the Society.
Article
Shallow water acoustics has flourished over the past fifty years, but most especially over the last 25 years. After World War II, the Cold War between the USSR and the West focused the emphasis in ocean acoustics on deep, “blue water.” After the Cold War waned in 1990, the emphasis changed to “brown water” coastal acoustics studies. In this paper,...
Article
This study provides a review of the acoustic and ocean bottom sediment data collected during the Shelf Break Primer experiment conducted in 1996. The location of the experiment was in the southern New England Continental Shelf called the “New England Mud Patch.” The mud patch is a 13,000 square kilometer area covered by fine-grained sediment. Previ...
Article
This study focuses on the design of an experiment to estimate the shear wave properties of ocean bottom sediments at a location in the southern New England Continental Shelf called the “New England Mud Patch.” The mud patch is a 13,000 square kilometer area covered by fine-grained sediment. The inversion technique is based on collecting interface w...
Conference Paper
The Woods Hole Oceanographic Institution (WHOI) was founded in 1930, and throughout its history has had a strong involvement in research into the science and applications of sound in the ocean. In terms of a brief history, three eras stand out: (1) pre-WWII, (2) WWII, and (3) the postwar years. This manuscript will focus on the history of the most...
Article
The Woods Hole Oceanographic Institution (WHOI) was founded in 1930, and throughout its history has had a strong involvement in research into the science and applications of sound in the ocean. In terms of a brief history, three eras stand out: (1) pre-WWII, (2) WWII, and (3) the postwar years. Though the most colorful pictures and stories come fro...
Article
A feature model for a shallow ocean front over a bottom with constant slope [Y.-T. Lin and J. F. Lynch, J. Acoust. Soc. Am. 131, EL1-EL7 (2012)] is analyzed to determine the parameter dependence of three-dimensional normal mode solutions. The front is a curved interface between two isospeed regions in a coastal wedge. Relevant parameters are the fr...
Article
Temporal fluctuations of intensity of sound pulses (300±30 Hz) are studied in the presence of nonlinear internal waves (NIW) moving at the some angle with direction of an acoustic track providing mode coupling. In the episode of Shallow Water 2006 experiment, considered in the work, angle between wave front of NIW and source-receiver direction is a...
Article
A study of sound propagation over a submarine canyon northeast of Taiwan was made using mobile acoustic sources during a joint ocean acoustic and physical oceanographic experiment in 2009. The acoustic signal levels (equivalently, transmission losses) are reported here, and numerical models of 3-D sound propagation are employed to explain the under...
Article
The accuracy of any sonar performance prediction depends on the accuracy of its environmental and system-related inputs [e.g., transmission loss (TL), ambient noise , and target source level , among others]. However, particularly with the environment, perfect temporal and spatial knowledge of the input is simply unavailable, and as a result, perfor...
Article
Intensity fluctuations of the low frequency LFM signals (band 270–330 Hz) were observed in Shallow Water 2006 experiment in the presence of moving train consisting of about seven separate nonlinear internal waves crossing acoustic track at some angle (~ 80º). It is shown that spectrum of the sound intensity fluctuations calculated for time period o...
Article
An adaptive back-propagation localization method utilizing the dispersion relation of the acoustic modes of low-frequency sound signals is reviewed in this talk. This method employs an adaptive array processing technique (the maximum a posteriori mode filter) to extract the acoustic modes of sound signals, and it is capable of separating signals fr...
Article
Acoustic propagation and scattering in marine canyons is an inherently 3-D problem, both for the environmental input (bottom topography and geology, biology, and physical oceanography) and the acoustic field. In this talk, we broadly examine what our knowledge is of these environmental fields, and what their salient effects should be upon acoustics...
Article
In 2006, a multidisciplinary experiment was conducted in the Mid-Atlantic continental shelf off the New Jersey coast. During a 2 day period in mid-September 2006, more than 200, unconfirmed but identifiable, sei whale (Balaenoptera borealis) calls were collected on a moored, combined horizontal and vertical line hydrophone array. Sei whale movement...
Technical Report
Full-text available
In 2012 one 2D and three 3D seismic surveys were simultaneously conducted in Baffin Bay, West Greenland. The surveys were monitored using 21 acoustic dataloggers deployed in and around the seismic sites and CTD data were collected throughout the seismic season. These environmental data together with bathymetry measurements collected by the seismic...
Patent
Full-text available
Methods and systems for detecting a plume of a first fluid in a second fluid using an acoustic wave are provided, where the first fluid has a different acoustic index of refraction than the second fluid. A horizontal array having a plurality of receiving elements receives an acoustic signal propagated through the second fluid and at least one refra...
Conference Paper
Full-text available
Regional ocean models have long been integrated with acoustic propagation and scattering models, including work in the 1990s by Robinson and Lee. However, the dynamics in these models has been not inclusive enough to represent submesoscale features that are now known to be very important acoustically. The features include internal waves, thermohali...
Article
A fully three-dimensional coupled mode approach is used in this paper to describe the physics of low frequency acoustic signals propagating through a train of internal waves at an arbitrary azimuth. A three layer model of the shallow water waveguide is employed for studying the properties of normal modes and their coupled interaction due to the pre...
Conference Paper
Sonar reconnaissance of fishes for stock assessment and research has been an effective and minimally invasive method of gathering abundance and distribution data on scales of 10s to 100s of km since the 1950s. Yet, classification of fishes remains one of the greatest challenges of active sonar surveys. Many variables affect sonar reflection, includ...
Conference Paper
During May 2012, we conducted hydrographic surveys in conjunction with studies of acoustic scattering from fish schools north of Cape Hatteras. The waters of the continental shelf were greater than 4° Degrees C. warmer than prior observations during typical spring-time conditions in May 1996. In addition, the temperature gradients which normally ex...
Article
The use of simplified "feature models" (geometric idealizations of specific, isolated ocean features) for coastal oceanographic features can allow one to calculate acoustically useful quantities approximately and even generate analytic forms for them. Feature models for coastal fronts, eddies, internal tides, linear and nonlinear internal waves, an...
Article
We will report on the results from an experiment off Cape Hatteras, North Carolina, to look at scattering and reverberation from fish schools in the 500–1500 Hz band. The experiment, which was performed during the period May 12–29, 2012, was a joint acoustics, biology, and physical oceanography effort, with distinct, but coordinated, goals in each...
Article
During the Shallow Water Acoustic Experiment 2006 (SW06), detailed measurements of the time-varying ocean environment were made while simultaneously acoustic signals were transmitted between various source and receiver pairs. The time-varying environment induced by internal waves (IW) was recorded by an array of moored thermistor chains, as well as...
Article
The Shallow Water 2006 (SW06) experiment was a large-scale acoustic experiment conducted on the New Jersey continental shelf in the summer of 2006 with substantial investment from the Office of Naval Research. The main goal of this experiment was to find a detailed understanding of the waveguide during the propagation of broadband acoustic signals...
Article
The use of simplified "feature models" (geometric idealizations of specific, isolated ocean features) for coastal oceanographic features can allow one to calculate acoustically useful quantities approximately and even generate analytic forms for them. Feature models for coastal fronts, eddies, internal tides, linear and nonlinear internal waves, an...
Article
It is now well known that coastal nonlinear internal waves, a common ocean feature, have large effects on the propagation of sound in the coastal ocean. Modeling such waves for input to acoustic models using regional ocean numerical models is difficult due to the fine spatial and temporal resolution needed. A multi-university program called Integra...
Article
Full-text available
The paper presents an analysis of energy fluctuations of high-frequency (2–4.5 kHz) sound signals propagating in a shallow water in the presence of nonlinear (soliton-like) internal waves (2006 Shallow Water experiment, US Atlantic shelf). Signals were received by three single hydrophones in different directions at distances of ∼4, ∼12, and ∼5 km f...
Conference Paper
Full-text available
During naval operations, sonar performance estimates often need to be computed in-situ with limited environmental information. This calls for the use of fast acoustic propagation models. Many naval operations are carried out in challenging and dynamic environments. This makes acoustic propagation and sonar performance behavior particularly complex...
Article
Full-text available
We report here on the preliminary results from an experiment off Cape Hatteras, North Carolina, to look at acoustic scattering and reverberation from fish schools in the 500-1500 Hz band. The experiment, which was performed during the period May 12-29, 2012, was a joint acoustics, biology and physical oceanography effort, with distinct, but coordin...
Article
Internal waves and bathymetric variation create time- and space-dependent alterations in the ocean acoustic waveguide, and cause subsequent coupling of acoustic energy between propagating normal modes. In this paper, the criterion for adiabatic invariance is extended to the case of an internal solitary wave (ISW) encountering a sloping bathymetry (...
Article
The acoustic ducting effect by curved nonlinear gravity waves in shallow water is studied through idealized models in this paper. The internal wave ducts are three-dimensional, bounded vertically by the sea surface and bottom, and horizontally by aligned wavefronts. Both normal mode and parabolic equation methods are taken to analyze the ducted sou...
Chapter
In Chap. 1, we briefly discussed the future of shallow water acoustics as part of motivation for this book. In this chapter, we will attempt to go into some more detail on the various topics that we touched there and in other portions of the book. We will do this in a broad topical way, treating oceanography, bottom acoustics, acoustic propagation...
Chapter
In this chapter, we consider the applications of sound signals with frequencies less than 500 Hz. The use of such low frequencies is primarily motivated by the strong attenuation of acoustic waves in shallow water due to the interaction with the bottom. For example, for a negative gradient sound speed profile, the transmission loss of acoustic sign...
Chapter
One of the most important problems in ocean acoustics is the study (measurement, forecasting) of noise, that is, of the sound fields formed by various wideband, distributed sources. These sources include wind-generated waves (surface disturbance noises), various human constructions which generate industrial and mechanical noises (ships, drilling pl...
Article
The 2001 Asian Sea International Experiment (ASIAEX2001) is a large-scale survey performed in the South China Sea. During May 2001 several minutes of M-sequence phase modulation signals were transmitted by a 400-Hz source repeatedly at intervals of half an hour, and received by an array 31 km away to conduct tomography of internal waves. The signal...
Article
In the past half-century numerous scientific research programs have been conducted which have advanced our understanding of shallow water acoustics far beyond the original and pioneering work by Ewing, Worzel, and Pekeris (1948). In particular, during the last three decades several major initiatives have focused on both observation and modeling of...
Article
The internal wave is one of the primary causes for ocean variations in shallow water. The temporal-spatial stability of the sound channel may degrade in the presence of the internal wave. The statistical characteristics of the acoustic field, excited by a 400-Hz source in the ASIAEX 2001 South China Sea (SCS) experiment, are presented. The receivin...
Article
It is known that the waveguide depth variability causes horizontal refraction and coupling of acoustic normal modes. Presence of large bottom sediment waves and sea swell are examples of strongly anisotropic waveguides that result in range dependence of the acoustic scintillation index. In the directions parallel to the wave crests, three-dimension...
Article
Environmental data collected near the continental shelf and the shelfbreak in the Southern East China Sea around Taiwan are utilized to study sound propagation effects of tropical cyclones (typhoons). These data were from the Conductivity-Temperature-Depth (CTD) profiling casts conducted during the Quantifying, Predicting, Exploiting (QPE) Uncertai...
Article
Three-dimensional propagation effects of low frequency sound from 100 to 400 Hz caused by seafloor topography and range-dependent bottom structure over a 20 km range along the New Jersey shelf are investigated using a hybrid modeling approach. Normal modes are used in the vertical dimension, and a parabolic-equation approximate model is applied to...
Article
An internal solitary wave (ISW) encountering the shelf break, making the waveguide is compressed, can cause different joint coupling effect for acoustic modes. In this paper, the extended criterion for adiabatic invariance is developed by parameterizing the joint mode coupling effect of an ISW encountering the shelf break and is used for sensitivit...
Article
Experimental observations and theoretical studies show that nonlinear internal waves occur widely in shallow water and cause acoustic propagation effects including ducting and mode coupling. Horizontal ducting results when acoustic modes travel between internal wave fronts that form waveguide boundaries. For small grazing angles between a mode traj...
Article
Environmental sensors moored on the New Jersey continental shelf tracked constant density surfaces (isopycnals) for 35 days in the summer of 2006. Sound-speed fluctuations from internal-wave vertical isopycnal displacements and from temperature/salinity variability along isopycnals (spiciness) are analyzed using frequency spectra and vertical covar...
Article
To understand the issues associated with the presence (or lack) of azimuthal isotropy and horizontal (along isobath) invariance of low-frequency (center frequencies of 600 Hz and 900 Hz) acoustic propagation in a shelfbreak environment, a series of experiments were conducted under the Autonomous Wide-Aperture Cluster for Surveillance component of t...
Article
Sound at 85 to 450 Hz propagating in approximately 80-m depth water from fixed sources to a joint horizontal/vertical line array (HLA/VLA) is analyzed. The data are from a continental shelf area east of Delaware Bay (USA) populated with tidally generated long- and short-wavelength internal waves. Sound paths are 19 km in the along-shore (along inte...
Article
A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter,...
Article
During a 2 day period in mid-September 2006, more than 200, unconfirmed but identifiable, sei whale (Balaenoptera borealis) calls were collected as incidental data during a multidisciplinary oceanography and acoustics experiment on the shelf off New Jersey. Using a combined vertical and horizontal acoustic receiving array, sei whale movements were...
Article
The horizontal ducting of sound by an oceanic temperature front over a sloping bottom is studied with an idealized wedge model consisting of a lateral interface across the slope. The water outside the frontal interface has higher temperature, hence faster sound speed, and it will produce inshore reflection/refraction of the sound. Combining the off...
Book
Shallow water acoustics (SWA), the study of how low and medium frequency sound propagates and scatters on the continental shelves of the worlds oceans, has both technical interest and a large number of practical applications. Technically, shallow water poses an interesting medium for the study of acoustic scattering, inverse theory, and propagation...
Chapter
To many ocean acousticians, shallow water is “water a few acoustic wavelengths in depth, where the normal mode description of the sound field is efficient.” To some of our physical oceanographer friends, shallow water is taken as the portion of the sea that extends from the shore to the continental shelf break. A rather jaundiced geologist once des...
Chapter
As we have often pointed out, when considering the propagation of sound in a shallow water waveguide, it is of primary importance to take into account interaction of the sound with the bottom. The hardest quantity to quantify in this interaction is absorption in the bottom, which leads to a fall in the signal intensity with distance. Formally, this...
Chapter
From the viewpoint of low- and mid-frequency shallow water acoustics, the ocean shelf is a waveguide, limited by a pressure release boundary above (the ocean’s surface) and an absorbing boundary below (the ocean bottom/seabed). In describing the sound field radiated from a source (whether point or distributed), both the waveguide’s interior and bou...
Chapter
The spatial processing of acoustic signals measured in field experiments and the creation of special acoustic signals to be radiated for specific purposes on the sea shelf are just two examples out of many of signal processing for shallow water acoustics. In doing such processing, it is important first of all to determine the commonly used characte...
Chapter
An extremely important part of shallow water acoustics is the study of long-range, low-frequency reverberation. In particular, one is studying acoustic wave backscattering by medium inhomogeneities, which are generally separated by a distance of a few to several tens of kilometers from a sound source and receiver. Interest in this area of study is...
Chapter
Up to this point now we have considered sound propagation in shallow water as being through a deterministic, inhomogeneous medium. It is well known that these inhomogeneities can have a considerable effect on the propagation of sound. Moreover, we know from oceanography that these random inhomogeneities are primarily concentrated in the top kilomet...
Chapter
In considering the propagation of sound through fluid or elastic media (or light through optical media, or heat through materials, etc.), it is usual to first address the so-called “forward problem.” Specifically, one calculates the sound (light, heat) field assuming knowledge of both the medium properties and of the physics governing the radiation...
Chapter
In this chapter, we will consider some simple models of the shallow water waveguide. Such models allow us to obtain and understand the main features of SW sound propagation quickly. Such simple models can also be perturbed to take into account more realistic properties of the environment, thus giving them far more power than one might think at firs...
Article
Internal waves, bottom sand waves, and ocean surface waves are known to have an impact on low-frequency 3-D acoustic propagation in shallow water. It has been observed both experimentally and numerically that in presence of internal waves in shallow water, acoustic energy propagates further and with less geometrical spreading in a preferred directi...