Matched field processing is a parameter estimation technique for localizing the range, depth, and bearing of point source from signal propagating in an acoustic waveguide. The observed at array presence additive, spatially correlated noise that also propagates same ocean environment as signal. In weak signal-to-noise situation this requires maximum exploitation physics both structure which then must be coupled to optimum methods processing. We study by modeling waveguide horizontally...

A new solution technique for wave propagation in horizontally stratified viscoelastic media is presented. The model provides a full the field generated by single source as well that vertical array. It allows spatial distribution of acoustic to be evaluated at least one order magnitude faster than with existing models based on Thomson–Haskell technique. computational efficiency numerical code demonstrated providing exact solutions reflectivity pattern associated narrow ultrasonic beams...

This paper describes an on-going research effort to achieve real-time cooperative localization of multiple autonomous underwater vehicles. We describe a series experiments that utilize surface craft (ASC), equiped with undersea acoustic modems, GPS, and 802.11b wireless Ethernet communications, acquire data develop software for distributed vehicle networks. Our demonstrate the capability Woods Hole modems provide accurate round-trip one-way range measurements, as well transfer, fully mobile...

This paper presents an acoustic localization system for small and low-cost autonomous underwater vehicles (AUVs). Accurate robust AUVs would lower the barrier toward multi-AUV research in river ocean environments. However, these introduce size, power, cost constraints that prevent use of conventional AUV sensors positioning systems, adding great difficulty to problem localization. Our uses a single transmitter placed at reference point is acoustically passive on AUV, reducing power use,...

This paper presents preliminary results of a recent study whose overall objectives are to determine the mechanisms contributing significantly subcritical acoustic penetration into ocean sediments, and quantify for use in sonar performance prediction detection buried objects. In situ measurements were performed on sandy bottom geoacoustical geomorphological properties also measured. A parametric array mounted tower moving rail was used insonify hydrophones located above below sediment...

The use of low-frequency sonars (2–15 kHz) is explored to better exploit scattering features buried targets that can contribute their detection and classification. Compared conventional mine countermeasure sonars, sound penetrates into the sediment at these frequencies, excitation structural waves in enhanced. main contributions target echo are specular reflection, geometric diffraction effects, response, with latter being particularly important for man-made elastic objects possessing...

A previously developed boundary perturbation method [W. A. Kuperman, J. Acoust. Soc. Am. 58, 365–370 (1975)] is extended to treat scattering at a randomly rough interface which separates viscoelastic media. This then combined with full wave treatment of sound propagating in stratified ocean described by system fluid and elastic layers [H. Schmidt F. B. Jensen, 77, 813–825 (1985)]. The net result combining the solution technique define set effective potentials which, when inserted algorithm,...

Buried objects have been largely undetectable by traditional high-frequency sonars due to their insignificant bottom penetration. Further, even a high grazing angle sonar approach is vastly limited the coverage rate dictated finite water depth, making detection and classification of buried using low frequency, subcritical an interesting alternative. On other hand, such concept would require clues different from high-resolution imaging shadows maintain false alarm rates. A potential...

For the last two decades, an extensive transition in automotive X-in-the-loop activities from isolated electronic control units to real-time related, geographically distributed validation tasks has occurred. Benefits are strengthening frontloading, enabling concurrent engineering and reducing prototypes testing efforts. As a downside, comprehensive system understanding adequate simulation models must be provided. New technological trends like software-over-the-air-updates denote continuous...

A new wave theory model providing consistent modeling of seabed insonification, three-dimensional target scattering, and rough reverberation has been used to investigate the spatial temporal characteristics multistatic scattering from rippled, shallow water seabeds. It is shown that highly polarized—close monochromatic—spectral ripple fields are associated with a environment which sensitive both frequency insonification aspect relative ripples. The study suggests significant gains in...

The magnitude of low-frequency (10−100 Hz) propagation loss in the central Arctic is known to be larger than predicted by most free surface scattering theories. This high introduced primarily at ice canopy, with which acoustic path interfers regularly due presence a strongly upward refracting duct. While distinct feature theories such as boss or elastic keel models predict higher losses, these results are typically too frequency dependent agree data over entire band interest. Perturbation...

A three-dimensional fast field program (FFP) model based on the global matrix method will be presented. Compared to traditional propagator methods, allows for a more efficient, and, furthermore, numerically stable computation. The expansion does not restrict sources center axis, but an arbitrary source geometry—as opposed earlier two-dimensional versions. As consequence, solution includes simultaneously both vertically and horizontally polarized shear waves. mathematical description given...

The waveguide nature of a shallow water environment bounded below by viscoelastic medium permits noise to couple into seismic waves. Geophone and hydrophone measurements have shown that threshold frequency about 10 Hz in 100 m water, there is large increase the measured levels, with peak at approximately 0.25 Hz. A previously developed wave theory distributed has been combined full solution technique for stratified elastic media used numerical modeling analysis this phenomenon. It...

Climate induced changes in the Arctic Ocean have severely impacted underwater acoustic communication and navigation; understanding noise characteristics is critical to improving performance of these operations. Ambient from Beaufort Sea recorded experiments more than 20 years apart (SIMI94 ICEX16) are compared determine differences that may be attributed region's rapidly changing environment. Spectral comparison shows within 20-350 Hz ∼30 dB louder 1994 2016; however, this likely due higher...

This paper presents a scalable acoustic navigation approach for the unified command, control and coordination of multiple autonomous underwater vehicles (AUVs). Existing multi-AUV operations typically achieve manually, by programming individual on surface via radio communications, which becomes impractical with large vehicle numbers; or they require bi-directional inter-vehicle communications to limited when submerged, scalability due physical properties channel. Our utilizes single,...

The spatial statistics of the acoustic field in shallow water are strongly affected by interfacial roughness and volume fluctuations column or seabed. These features scatter energy, reducing coherence field. This paper introduces a consistent, mode-based modeling framework for ocean scattering. First, rough surface scattering theory Kuperman Schmidt is reformulated terms normal modes, resulting computation times which reduced several orders magnitude. Next, perturbation describing from sound...

Complete wave-theory solutions have been obtained numerically for both the reflected and transmitted fields associated with a narrow Gaussian beam incident on water–sediment interface near critical grazing angle. Interesting reflectivity phenomena are observed, such as subcritical penetration into sediment, nonspecular reflection, lateral displacement along of beams. These results in qualitative agreement experimental observations using parametrically (nonlinearly) generated It is...

In the Spring of 1994, dynamical and mechanical behavior Artic ice cover was studied from an camp deployed in Beaufort Sea, 2-300 nm north Prudoe Bay. The periodic measurement under-ice topography is a key component experiment, authors make use autonomous underwater vehicle (AUV) technology to provide cost effective alternative nuclear submarines. As proof concept, AUV Odyssey used obtain ice-topographic data areas located up 10 km base camp. Accurate reliable navigation crucial successful...

Although the theoretical formulation in terms of spherical harmonics for seismoacoustic propagation spherically stratified, fluid/elastic media has been known many decades, its numerical implementation is nontrivial. Thus, limited machine precision incapable directly representing dynamic range throughout stratification. The solution expansion coefficients therefore inherently unstable. However, this problem equivalent to stability issue facing depth-separated wave equation plane-stratified...

The Arctic Ocean is undergoing dramatic changes, the most apparent being rapidly reducing extent and thickness of summer ice cover. As has been well established over prior decades, environmental acoustics ice-covered dominated by two major effects: highly inhomogeneous cover, monotonically upward refracting sound speed profile, combination which forces all paths to be exposed strong scattering loss associated coherence. In some portions Ocean, however, a persistent inflow shallow 'tongue'...

Synthetic Aperture Sonar (SAS) is a technique to improve the spatial resolution from moving set of receivers by extending array in time, increasing effective length and aperture. This limited accuracy receiver position estimates, necessitating highly accurate, typically expensive aided-inertial navigation systems for submerged platforms. We leverage simultaneous localization mapping fuse acoustic navigational measurements obtain accurate pose estimates even without benefit absolute...