William M. Carey's research while affiliated with Boston University and other places

Publications (159)

Article
Full-text available
LONG-TERM GOALS One research goal developed from conducted shallow water (SW) acoustic transmission experiments in sandy-silty areas [1] revealed a nonlinear power law frequency-dependent attenuation at lower frequencies (≤ 1 kHz) consistent with results reviewed in [2-4] and the observations by the ONR-HEP program. The Biot Theory [5] predicts tha...
Article
The discussion in the previous chapter indicates an exact treatment of this air–sea boundary interaction zone is not possible. If such a characterization were possible, one would still have the problem of environmental uncertainty associated with the measured boundary layer parameters required for comparison and evaluation. With this uncertainty, i...
Article
Experiments from several shallow-water areas are summarized. Coherent sound transmission results, particularly wavenumber spectra, are compared to range-dependent calculations that use oceanographic and geophysical characteristics from measurements and archives as bounded inputs to the propagation codes. In general excellent agreement was obtained...
Article
Full-text available
The sound speed characteristic of the high-porosity mud has been found to have sonic speeds lower than expected. Since the presence of bubbles is known to be an important factor in decreasing the sound speed, these low sound speeds are attributed to methane microbubbles that result from biological decay. A theoretical treatment of "muddy sediments,...
Article
Principal constituents of mud ocean sediments are small platelets of minerals such as smectite and kaolinite. Isomorphous substitution produces negative charges on platelets, and salt water ions rearrange to cause an effective quadrupole moment per unit area of platelet. A card‐house structure results, where an edge of one platelet is bonded to the...
Article
Full-text available
Measurements of the sound speed characteristic of the high porosity Dodge Pond mud were found to have a sonic speed less than that observed by Wood and Weston (Acustica, V14, 1964), a compressional speed 3% less than that of water. Other experiments performed on muddy sediments at frequencies greater than a kilohertz are consistent with the Dodge P...
Article
The research problem addressed by ambient noise investigators since the 1950s is the quantitative determination of the sources of sound in the sea. Investigators quickly realized the importance of intermittent sources of sound, compared with the persistent ambient background. Biological noises and nonbiological (including man-made sounds) sources w...
Article
Estimating the increase in noise due to commercial shipping is of interest because of naval operations and it's environmental consequences to marine life. Recent low-frequency noise calculations (Evans and Carey, Proc. 9 th ICTCA, Univ. Bundeswehr, De) for the mid-Philippine sea illustrate the major uncertainties due to the basin's slope...
Chapter
Underwater sound is a first-order compressible pressure oscillation, compared with the zero-order hydrodynamic motions, and propagation is governed by the wave equation. The total sound field is, by the principle of superposition, a linear combination of pressure fields due to individual sources. One or more of the sources may constitute a signal o...
Article
Ambient noise investigations constitute one of the largest sections of the Journal of the Acoustical Society of America. Urick (1984) has summarized a good many of these experimental papers and his report is valuable as it updates and extends the work of Wenz (1972. In this chapter the discussion focuses on the key aspects of ambient noise by inter...
Article
Ambient noise calculations have traditionally been of naval interest as necessary sonar performance prediction tools. Performance prediction systems had as their primary purpose the allocation of resources and the estimation of system performance in the development of tactics. Since these prediction system could be site-specific, experimental resul...
Article
Backscatter from the sea surface is governed by the roughness of the surface and subsurface micro bubble distributions. At low frequencies, due to the paucity of large bubbles, scattering results primarily from coherent and∕or collective scatter from bubbles entrained by the subsurface vorticity or carried to depth by the Langmuir circulation and t...
Article
Full-text available
Intrinsic attenuation is ideally measured for plane compressional waves in an unbounded homogeneous medium. For typical marine sediments, at frequencies below 5000 Hz, sufficient realization of this idealization cannot be achieved. Reported indirect measurements typically have source and receiver in the water column and require hypothesized theorie...
Article
Full-text available
Platelets in high porosity ocean sediments carry negative charge due to isomorphous substitution. When immersed in an ion dense environment such as sea water, positive charges congregate near each surface. The high porosity combined with the charge configurations suggests a cardhouse structure where platelets repel face to face and attract face to...
Article
Full-text available
Relatively simple approximations for transmission loss in shallow water based on ray theory were presented by Marsh and Schulkin (1962), Weston (1971), Smith (1974), and Rogers (1981). Formulas for averaged transmission loss versus range in stratified shallow water waveguides over sandy-silty sediments are derived entirely from mode theory. Results...
Article
Unmanned (autonomous) underwater vehicles offer a unique, cost-effective platform for performing ocean acoustic measurements and surveys because multiple systems can be deployed from a single research vessel. Various data surveys can be performed including on-the-bottom geo-acoustic surveys over large areas, sub-sea-surface turbulence and microbubb...
Article
Noise produced by the oscillation of microbubble distributions and impacts (raindrops and splash) in the air-sea boundary zone results in doublet radiation patterns and noise fields with definitive temporal and spatial characteristics. Turbulence generated noise is quadrupole, and nonlinear wave-wave interactions are infrasonic. Plausible mechanism...
Article
Full-text available
A model of mud as a lyophobic colloid [Verwey and Overbeek (1948)] leads to a card-house structure of platelets, typically kaolinite or smectite particles. Because of isomorphous substitution, each platelet carries a distributed negative charge. The structure is immersed in water which, especially so for sea water, carries positive and negative ion...
Article
Questions important to the sonic detection of buried ordinance are whether the sound dispersion and attenuation of muddy bottoms can be predicted and verified. Wood and Weston [Acustica (1964)] measured compressional speeds in harbor mud 3% less than that of water with attenuation considerably less than those of sandy/silty sediments. A recent theo...
Article
Numerous shallow water acoustic transmission experiments over sandy‐silty bottoms demonstrate that the frequency dependence of intrinsic sediment attenuation at frequencies less than 1 kHz is nonlinear. Computational analyses including modeled geoacoustic profiles have shown that good agreement with experimental data can be obtained for frequencies...
Article
How does scattering in sound channels (deep and shallow waters) limit coherent array processing or what is the limitation of resolution in terms of the mutual coherence function and its temporal and spatialcoherence lengths? The resolution of an array is limited by the mutual coherence function; but estimation in a partially coherent noise backgrou...
Article
Full-text available
Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
Article
An autonomous array system is uniquely suited to perform near bottom (≈1 m) measurements of horizontal wave number spectra that estimate water and interface wave numbers. Synthetic coherent processing provides the required gain to observe the interface wave peak 40–50 dB below the peaks of water modes. Comparable measurements were performed with an...
Article
Full-text available
The depth dependent shear wave speed in marine sediments is much less than both the compressional and water column sound speeds. The neglect of shear in geoacoustic inversions is usually justifiable, but at frequencies less than 300 Hz, the loss of acoustic energy from the water column because of nonreturning radiation of shear waves into the botto...
Article
Shallow water transmission loss measurements yield intrinsic attenuation estimates for acoustic waves in the underlying sediment, with results that are consistent with attenuation being proportional to frequency raised to a power n, with n between 1.6 and 1.87. Plausible theory suggests that n should be identically 2. The discrepancy can be explain...
Article
Sandy/silty marine sediments are water saturated and consist of diverse tiny rock pebbles. The weight of higher pebbles holds lower pebbles in contact. For low-frequency acoustic disturbances, the no-slip condition and viscosity cause the local water displacement near solid surfaces to be nearly the same as that of the neighboring pebbles. Water fa...
Article
Muddy sediments found in rivers, deltas, and harbors are classified as slow bottoms and pose a problem for the detection of buried ordnance. The questions for mud discussed here are as follows: First, can the frequency dependence dispersion characteristic be predicted and verified by measurements in areas where buried object detection is required?...
Article
A review of measured transmission over sandy bottoms has found the attenuation alpha(f)=alpha(f(o))(ff(o))(n), 1.6</=n</=1.87 for 50 Hz<f<1 kHz where the reference frequency f(o) is nominally 1 kHz. Since plausible theory suggests that n should be equal to 2, why are observed n values different? Calculations incorporating scattering, layering, and...
Article
Full-text available
A major component of harbor mud is the clay mineral kaolinite, Al(2)Si(2)O(5)(OH)(4). Isomorphous substitution, Al atoms occasionally replacing Si atoms, causes a net positive charge of roughly one electronic charge per 400 Si atoms. Kaolinite platelets have diameters and thicknesses of the order of 1 mum and 20 nm. The platelet's positive charge i...
Conference Paper
The Annual Energy Outlook 2008 prepared by Energy Information Administration of the United States Department of Energy projects the continued use of fossil fuels (liquids, coal and natural gas) with little emphasis on ldquoOceanic Energy Conversionrdquo and marginal importance to ldquoOff-shore Wind Energy conversion.rdquo However the potential ene...
Article
The use of autonomous undersea vehicle towed arrays offer an inexpensive way to carry out oceanographic measurements. Due to the small size and limited power of such vehicles, the physical aperture of the array is necessarily limited and the tow speed is low. However, there is an advantage in that short arrays at low speeds can have no flow noise....
Article
Full-text available
An array was developed to demonstrate, and quantify the performance characteristics of an autonomous-vehicle towed-array system. This technology provides for a cost effective tool for the measurement of coherent signal propagation, depth dependent and directional noise fields and to establish quantitative limits on array performance. The tangential...
Article
Full-text available
Gravity holds the sediment's particles in loose contact; the strength varies with depth. The distribution in shapes, sizes, and orientations is presumed independent of depth. Each particle is subject to several contact forces, and also to a buoyancy force exerted by the surrounding water. An externally imposed shear stress results in distortions in...
Article
The modal attenuation coefficients (MACs) can be determined using a recent simplification of Biot theory [A.D. Pierce et al., J. Acoust. Soc. Am. 114, 2345 (2003)]. Numerical calculations use sandy bottom sediments and isospeed, linear, and piecewise linear water profiles, which are simplifications that preserve key features of those obtained in ex...
Article
The Annual Energy Outlook 2008 [1] prepared by Energy Information Administration of the United States Department of Energy projects the continued use of fossil fuels (liquids, coal and natural gas) with little emphasis on “Oceanic Energy Conversion” and marginal importance to “Offshore Wind Energy conversion.” However the potential energy available...
Article
Inverse techniques based on data for long‐range propagation in shallow water have recently inferred that the attenuation in certain marine sediments varies at low frequency as the 1.8 power. Idealized models predict the exponent to be exactly 2.0. The inverse inferences usually assume the bottom is a fluid, and this is ordinarily a good approximati...
Article
Full-text available
Sound speed profiles in shallow water waveguides are small deviations from isospeed and often decrease monotonically with depth. Approximation formulas for the propagating modes are found using a modified form of the classical WKBJ method. The ocean bottom is taken as homogeneous. The approach is accurate for modes with phase speeds greater than, a...
Article
Experiments have been conducted near the site of AMCOR Borehole 6010 on the New Jersey Shelf to evaluate propagation predictability in sandy shallow-water environments. The influence of a nonlinear frequency dependence of the sediment volume attenuation in the uppermost sediment layer at this location is examined. Previously it was determined that...
Conference Paper
Full-text available
A review of experimental evidence shows that the low frequency attenuation of compressional acoustic waves in sandy marine sediments obeys a simple power law consistent with a frequency dependent attenuation proportional to f<sup>n</sup> , n =1.0. This observation is in general agreement with Biot's model (1956) for frequencies less than 1 kHz. Rec...
Article
A method for obtaining two-term asymptotic modal approximations is described. Propagating modes are treated for range-independent shallow waveguides with downward refracting sound speed profiles. The approximation formulas are convenient for displaying the variations resulting from changes in environmental and acoustic parameters. Estimates for the...
Conference Paper
An autonomous vehicle towed array, Avta, system has been developed and demonstrated in several at sea experiments that show a small autonomous vehicle is capable of towing the array in a steady and stable configuration sufficient for coherent-synthetic-aperture processing. Calculated transmission loss compared well with measured transmission loss u...
Article
Several published and presented papers by Ingenito [1973], Zhou and Zhang [2005], and others have discussed the attenuation of sound in marine sediments at low frequencies, and another is shortly to appear [Holmes, Carey, Dediu, and Siegmann, JASA Express Letters, 2007], the latter reporting a nonlinear frequency dependence as ω n , where n=1.8±0.2...
Article
Full-text available
The intrinsic sediment attenuation in adiabatic waveguides affects transmission loss through the modal attenuation coefficients (MACs). For sand‐silt bottoms, the non‐linear frequency dependence of attenuation in the upper sediment layer significantly affects the frequency variation of the MACs. This variation is shown to depend strongly on the wat...
Article
Experiments were conducted near the site of AMCOR Borehole 6010 on the New Jersey Shelf to characterize propagation predictability. The importance of a non‐linear power‐law frequency dependence of the sediment volume attenuation in the uppermost sediment layer is demonstrated. One metric of transmission loss variation with range is an effective att...
Article
Full-text available
It was previously shown [Pierce et al. (2006)] that the Burridge‐Keller formulation [J. Acoust. Soc. Am. (1981)] rigorously justifies the low‐frequency version [(1956a)] of Biot’s equations. Implementation involves two microscale problems: (1) incompressible viscousflow driven in a highly irregular space with rigid walls by a uniformly and external...
Conference Paper
Model-based signal processing techniques for a short towed array are experimentally demonstrated for both broad band and narrow-band signals. It is shown that accurate bearing and horizontal wavenumber estimations, for frequencies ranging from 220 Hz to 1228 Hz, can be made for acoustic apertures as short as 0.5 wavelength. The data were the result...
Article
Bearing estimation using an acoustically short towed array can be enhanced by the incorporation of a realistic signal model. By casting the problem as a joint estimation of bearing and source frequency, the bearing estimation performance, as measured by the variance of the bearing estimate, can exceed that of the conventional array processor. Exper...
Article
Shallow water experiments have been conducted in Nantucket Sound with an autonomous underwater vehicle towed hydrophone array system in an area proximate to that of a previous experiment [Frisk and Lynch, J. Acoust. Soc. Am. 86, 1928-1939 (1989)]. Transmission loss was measured, for frequencies between 220 and 1228 Hz in an ocean waveguide, under c...
Article
Full-text available
The original low‐frequency Biot model factors into three characteristic modes, one being the acoustics mode, having only three significant aggregate parameters: apparent density and bulk modulus, and a numerical coefficient relating attenuation to ω2. This prediction, although from a heuristic multiparametered model, finds an independent basis in a...
Article
The American National Standards on Acoustics are applied to common sound sources used in both acoustics research and in naval sonar systems operation. Metrics are quantified for both continuous and transient sources of sound. The standard definitions are reviewed with theoretical sound source models and applied to examples of energy sources of soun...
Article
Sound transmission results are reported for frequencies of 220, 415, 635, 823, 1031, and 1228 Hz in an iso‐velocity waveguide 13 m deep with known bottom properties. The experiments were conducted in Nantucket Sound in proximity to the Lynch‐Frisk (1982) experiment in an area surveyed prior to the experiments. A fixed source and an autonomous under...
Article
The upper medium is sea water, and the bottom medium is a marine sediment whose physical description is consistent with the theory advanced by Frenkel in 1944 and with the model proposed by Biot in 1961 for a porous medium at low frequencies. Within the sediment, three generic types (modes) of wavelike disturbances are possible. These three modes a...
Article
The standard definitions found in the American National Standards on Acoustics are applied to common sound sources used in both underwater acoustics research and naval sonar system operation. Recommended metrics are quantified for both continuous and transient sources of sound. Standard definitions are reviewed with theoretical sound source models....
Article
Zhou and Zhang [J. Acoust. Soc. Am. (2005) (2006)] have reviewed diverse data for propagation in sandy sediments. Attenuation for frequencies below 1 kHz corresponds roughly to α=0.34(f/f o )2 dB/m with the reference frequency being 1 kHz. The best‐fit exponent is slightly less than 2. Their review of results for frequencies above 10 kHz suggests a...
Article
Lateral waves are the cw counterpart of head waves, the latter being sometimes used for geoacoustic inversion [Godin et al., 1999; Berger and Buckingham, 2000; Choi and Dahl, 2004]. They should be detectable at horizontal ranges r that satisfy the criterion H 2/(5λ)>r>4h 1 h 2/λ, where the various symbols refer to the water depth, height above bott...
Article
Results from an autonomous underwater vehicle (AUV) towed hydrophone array experiment are presented as a demonstration of a new in situ measurement technique. In this technique, a source is deployed from a small vessel and the AUV navigates along a pre-programmed path towing the hydrophone array. The added degrees of freedom associated with an arra...
Article
A question discussed over the last three decades is: ``how does scattering in the deep and shallow-water-sound channels limit coherent array processing?'' In particular, for the horizontal array, what is the limitation of resolution in terms of the mutual coherence function and its coherence length? For frequencies (400 Hz) the measurement of the m...
Conference Paper
An experiment was conducted to measure the sound speed in a water-saturated granular sediment within a range of frequencies where dispersion is predicted by a number of existing models. Between 2-4 kHz, the sound speed was inferred from measurements of the resonance frequencies of a right-circular-cylindrical container filled with the material. Fro...
Article
Beam-noise spectrum levels were measured with high-resolution horizontal arrays of 22 to 100 wavelengths long at frequencies between 50 and 320 Hz in the Mediterranean Sea. Results indicate that the low-frequency noise field has two major components one of which is due to the dynamic and temporally variable distant shipping. Beam noise level differ...
Article
In the ocean, natural and artificial processes generate clouds of bubbles that scatter and attenuate sound. Measurements have shown that at the individual bubble resonance frequency, sound propagation in this medium is highly attenuated and dispersive. The existing theory to explain this behavior is deemed adequate away from resonance. However, due...
Article
An autonomous underwater vehicle(AUV) with a towed hydrophone array (THA) can provide the capability of mobile‐single‐ship operation for both short‐range single path and long range synthetic aperture experiments. A low noise towed array for an AUV (REMUS) has been developed to demonstrate the feasibility and utility of such measurements. Previous m...
Article
The range‐averaged transmission loss increase in shallow water propagation depends critically on the intrinsic attenuation of the upper sediment. The attenuation coefficients of low‐frequency (<1 kHz) propagating modes determine the frequency dependence. Ingenito [J. Acoust. Soc. Am. 53, 858–863 (1973)] showed with measurements and theory that whil...
Article
Full-text available
Biot's model leads to an attenuation coefficient at low frequencies that is proportional to omega2, and such is consistent with physical models of viscous attenuation of fluid flows through narrow constrictions driven by pressure differences between larger fluid pockets within the granular configuration. Much data suggests, however, that the attenu...
Article
Shallow?water (SW) coastal areas with depths between 40 and 200 m with bottom sediment layers (<25?m) formed by deposition and sea level variations are known to have frequency?dependent sound transmission and reverberation characteristics especially under the adverse conditions of downward refraction. Coastal ocean?dynamics complicates these enviro...
Article
Bubbles, spray, splash, and clouds are formed by breaking waves and have been shown to be responsible for the production of sound. In the low-frequency-region, i.e., 20-500 Hz, the oscillation of the cloud as a whole is thought to be responsible for the radiation of sound. This paper treats the radiation of individual bubbles by first reviewing the...
Article
Acoustic waves propagating through bubbly liquid experience dispersion and attenuation when the excitation frequency is near the resonance frequency region of the bubble distribution. Due to high attenuation in this regime, traditional standing wave and time-of-flight measurement techniques fail and existing theories remain unverified above void fr...
Article
A water-filled impedance tube capable of improved measurement accuracy and precision is reported. The measurement instrument employs a variation of the standardized two-sensor transfer function technique. Performance improvements were achieved through minimization of elastic waveguide effects and through the use of sound-hard wall-mounted acoustic...
Article
The removal of samples or the insertion of measuring devices into the ocean bottom can alter the acoustic behavior of these sedimentary materials. A less invasive method for the acoustic characterization of marine sediments in the 1 to 10 kHz frequency range has been investigated. A water-filled impedance tube has been used to measure the complex r...
Article
A previous study [J. Acoust. Soc. Am. 112 (2002)] treated the detection of a weak target in an adverse shallow-water environment with ambient noise and ``known'' interfering ships by applying a model-based adaptive (recursive) technique. The shallow-water environment and noise sources were represented by a normal-mode model directly incorporated in...
Article
At frequencies of several kilohertz and below, the measurement of sound propagation in marine sediments is difficult due to the larger wavelengths. Laboratory experiments can be limited by the size of the facility required for propagation studies but are amenable to material property measurements. Impedance tube techniques can be used to measure th...
Article
For various underwater acoustic applications such as beamforming and matched field processing, it is important to understand the spatial characteristics of shallow water acoustic fields. Oceanic and geoacoustic variabilities introduce random fluctuations into the fields, for which an important metric is the spatial coherence that is the correlation...
Article
The experiment, The Acoustic Characterization Test III, was conducted in the oceanographically complex Strait of Korea to accurately measure the sound transmission under known environmental conditions. Geoacoustic profiles derived from geophysical measurements, measured bathymetry, and sound-speed profiles were the basis for range dependent parabol...
Article
The in situ study of oceanic bubble acoustics is a challenging endeavor. One must impose a variety of a priori assumptions and constraints in order to extract information that unambiguously sheds light on the underlying physical mechanisms that govern the transmission and scattering of sound in oceanic bubble assemblages. Conversely, laboratory stu...
Article
In the ocean, natural and artificial processes generate clouds of bubbles which scatter and attenuate sound, and the structure of these clouds (i.e., the space-dependent bubble size distribution and void fraction) evolves over time. Measurements have shown that at the individual bubble resonance frequency (IBRF), sound propagation in this medium is...
Article
Ambient Noise (AN) research during World War II was facilitated by the availability of calibrated instruments and motivated by the necessity to understand AN levels in coastal waters. The state‐of‐the‐art was reviewed by Knudsen in 1948 and later by Pryce and Urick in 1954. After the war, AN research waned until the classic paper by Wenz (1962) mar...
Article
In previous experiments, acoustic scattering from a bubbly liquid‐filled latex tube was investigated in the 5–20 kHz frequency range. The mean bubble resonance frequency was 113 kHz, and a Wood limit effective medium theory was found to quantitatively describe the scattering throughout the measurement range, using a void fraction as the model’s onl...
Article
The experiment called the Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea. It was designed to provide accurate measurements of sound transmission and array signal gain under known environmental conditions. Bottom sampling and sub-bottom surveys coupled with archival geophysical information provided...
Article
Acoustic scattering from a bubbly cylinder has been studied experimentally to determine the utility of effective medium scattering theory for a well defined shape. A bubble filled latex tube was submerged horizontally in a large tank, and its backscatter strength was measured for frequencies ranging from 5–20 kHz. Results show that the effective me...
Article
This paper summarizes our efforts to compare calculations in several shallow water areas using range dependent models with results from coherent sound transmission experiments. The approach is to use detailed environmental and geophysical measurements to determine acceptable ranges of input parameters for the range dependent calculations, and then...
Article
Complete understanding of sea?surface scattering, shallow water volume scattering, and bottom interaction requires the understanding of frequency?dependent acoustic propagation in bubbly media. Because of the high attenuation encountered at and near the range of resonance frequencies associated with bubble size distribution, experimental measuremen...
Article
This presentation deals with acoustic scattering from bubble clouds. In the most general manifestation, the cloud has arbitrary shape and extent and consists of a population of bubbles with arbitrary size distribution; the ensuing scattering problem is considerable. In the asymptotic limit of an acoustically compact cloud consisting of acoustically...
Article
The use of a towed array from a small autonomous underwater vehicle, AUV, such as the WHOI-Remus vehicle is discussed as a valuable ocean acoustics measurement tool for of 3-D characterization of shallow water regions. The feasibility of towing a 10-m-long, small-diameter fluid-filled hydrophone array behind Remus was investigated with a laboratory...
Article
Manipulation of Biot's equations using low-frequency and long-wavelength approximations yields wave equation with a dissipation term that predicts plane wave attenuation coefficients proportional to the square of the frequency. Examination of Biot's original derivation verifies that the wave speed in this equation is what results from Wood's theory...
Article
Determination of the frequency behavior of modal attenuation coefficients is essential for estimation of propagation influences of poro-elastic sediments. A recent simplification of the Biot model [Pierce et al., J. Acoust. Soc. Am. 114, 2345 (2003)] provides an approach for this determination. For plane compressional waves in a homogeneous medium,...
Article
Recent societal concerns have focused attention on the use of sound as a probe to investigate the oceans and its use in naval sonar applications. The concern is the impact the use of sound may have on marine mammals and fishes. The focus has changed the fields of acoustical oceanography (AO) and underwater acoustics (UW) because of the requirement...
Article
A complete model describing broadband sea surface scattering at high wind speeds has not been developed. One difficulty is accounting for scattering from near?surface bubble clouds. This problem has been addressed in the literature for low frequencies. To first order, an acoustically compact bubble cloud can be modeled as a compressible sphere, whe...
Article
The Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea to provide accurate measurements of sound transmission and coherence (array signal gain) under known environmental conditions. Bottom sampling and sub‐bottom surveys, coupled with archival geophysical information, provided the basis for geoacoustic...
Article
An acoustic experiment was performed on the New Jersey Continental Shelf in a well surveyed area with known bottom and sub?bottom properties. The measurement system was a calibrated vertical array 14?18 km from a known geological feature. Calibrated airgun shots (AG) and special small omni?directional explosives shots (SO) were used to generate imp...
Conference Paper
The presence of bubbles has been shown to change the compressibility and complex sound speed in a liquid. In the ocean, acoustically compact bubbly mixtures manifest themselves as highly compressible regions that effectively scatter low?frequency sound. To study low?frequency sound scattering, multifrequency backscattering experiments have been per...
Article
Allan Pierce, Editor‐in‐Chief, has recently written concise overviews of the Journal’s history, publication criteria, and issues. To stimulate discussion, this paper follows his lead and addresses several resolvable issues that could improve the quality of published articles. Concerning the peer review and the reviewer, when should reviewers recuse...
Article
Traditional processing has treated space and time as independent random variables with assumed ergodicity; however, dynamic?noise fields are produced by moving sources. In these cases, can velocity and range information be used to increase gain, cancel noise, and improve resolution? High?resolution arrays have measured the dynamic ambient noise fie...