Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Physical acoustics, underwater and ultrasonic.
Articles de revues sur le sujet « Physical acoustics, underwater and ultrasonic »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Physical acoustics, underwater and ultrasonic ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Godin, Oleg A., et Kay L. Gemba. « Graduate programs in physical, engineering, and underwater acoustics at the Naval Postgraduate School ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A122. http://dx.doi.org/10.1121/10.0015752.
Texte intégralRésumé :
The Departments of Physics and of Electrical and Computer Engineering at the Naval Postgraduate School offer graduate programs in acoustics leading to MS and PhD degrees in applied physics and engineering acoustics. Engineering acoustics degrees can be completed in either traditional or distance learning modes. The departments also offer stand-alone academic certificate programs in fundamentals of engineering acoustics, underwater acoustics, and sonar system applications, with a set of three certificates leading to a MS degree in engineering acoustics. MS and PhD programs are interdisciplinary, with courses and laboratory work drawn principally from the fields of physics and electrical engineering. Subjects covered include waves and oscillations; fundamentals of physical and structural acoustics; the generation, propagation, and reception of sound in the ocean; civilian and military applications of sonar systems; and acoustic signal processing. Topics of recent theses and dissertations include development and field testing of novel sensors for atmospheric and ocean acoustics, modeling and measurements of ambient noise and sound propagation in the ocean, sound scattering in underwater waveguides, acoustic vector sensors and vector field properties, acoustic communications, noise interferometry, time reversal in acoustics, geo-acoustic inversion, acoustic remote sensing of the ocean, and acoustics of autonomous underwater and aerial vehicles.
2
Lynch, James F., et Charles C. Church. « Introduction to the Special Issue on COVID-19 ». Journal of the Acoustical Society of America 153, no 1 (janvier 2023) : 573–75. http://dx.doi.org/10.1121/10.0017033.
Texte intégralRésumé :
The COVID-19 pandemic has been a global event affecting all aspects of human life and society, including acoustic aspects. In this Special Issue on COVID-19 and acoustics, we present 48 papers discussing the acoustical impacts of the pandemic and how we deal with it. The papers are divided into seven categories which include: physical masking and speech production, speech perception, noise, the underwater soundscape, the urban soundscape, pathogen transmissibility, and medical diagnosis.
3
Kuyama, Tamio. « New Research Fields of Ultrasonic Electronics and Underwater Acoustics ». Japanese Journal of Applied Physics 29, S1 (1 janvier 1990) : 8. http://dx.doi.org/10.7567/jjaps.29s1.8.
Texte intégral
4
Mallik, Wrik, Rajeev K. Jaiman et Jasmin Jelovica. « Predicting transmission loss in underwater acoustics using convolutional recurrent autoencoder network ». Journal of the Acoustical Society of America 152, no 3 (septembre 2022) : 1627–38. http://dx.doi.org/10.1121/10.0013894.
Texte intégralRésumé :
Underwater noise transmission in the ocean environment is a complex physical phenomenon involving not only widely varying physical parameters and dynamical scales but also uncertainties in the ocean parameters. It is challenging to construct generalized physical models that can predict transmission loss in a broad range of situations. In this regard, we propose a convolutional recurrent autoencoder network (CRAN) architecture, which is a data-driven deep learning model for learning far-field acoustic propagation. Being data-driven, the CRAN model relies only on the quality of the data and is agnostic to how the data are obtained. The CRAN model can learn a reduced-dimensional representation of physical data and can predict the far-field acoustic signal transmission loss distribution in the ocean environment. We demonstrate the ability of the CRAN model to learn far-field transmission loss distribution in a two-dimensional ocean domain with depth-dependent sources. Results show that the CRAN can learn the essential physical elements of acoustic signal transmission loss generated due to geometric spreading, refraction, and reflection from the ocean surface and bottom. Such ability of the CRAN to learn complex ocean acoustics transmission has the potential for real-time far-field underwater noise prediction for marine vessel decision-making and online control.
5
Ballard, Megan, Michael R. Haberman, Neal A. Hall, Mark F. Hamilton, Tyrone M. Porter et Preston S. Wilson. « Graduate acoustics education in the Cockrell School of Engineering at The University of Texas at Austin ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A124. http://dx.doi.org/10.1121/10.0015759.
Texte intégralRésumé :
While graduate study in acoustics takes place in several colleges and schools at The University of Texas at Austin (UT Austin), including Communication, Fine Arts, Geosciences, and Natural Sciences, this poster focuses on the acoustics program in Engineering. The core of this program resides in the Departments of Mechanical Engineering (ME) and Electrical and Computer Engineering (ECE). Acoustics faculty in each department supervise graduate students in both departments. One undergraduate and nine graduate acoustics courses are taught in ME and ECE. Instructors for these courses include staff at Applied Research Laboratories at UT Austin, where many of the graduate students have research assistantships. The undergraduate course, taught every fall, begins with basic physical acoustics and proceeds to draw examples from different areas of engineering acoustics. Three of the graduate courses are taught every year: a two course sequence on physical acoustics, and a transducers course. The remaining six graduate acoustics courses, taught in alternate years, are on nonlinear acoustics, underwater acoustics, ultrasonics, architectural acoustics, wave phenomena, and acoustic metamaterials. An acoustics seminar is held most Fridays during the long semesters, averaging over ten per semester since 1984. The ME and ECE departments both offer Ph.D. qualifying exams in acoustics.
6
Kukshtel, Natalie, Ying-Tsong Lin et Glen Gawarkiewicz. « Localization of an acoustic autonomous underwater vehicle using multi-channel back-propagation methods ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A302. http://dx.doi.org/10.1121/10.0018933.
Texte intégralRésumé :
Autonomous underwater vehicles (AUVs) are extremely useful tools for studying the acoustics of complex ocean environments due to their ability to detect environmental changes with greater spatial resolution than fixed moorings. During the New England Shelf Break Acoustics (NESBA) experiments in May 2021, an AUV system was deployed to collect acoustic data for investigating the local biological, physical, and geological oceanography. This acoustic AUV system was comprised of a modified REMUS 600 vehicle, a hull-mounted 3.5 kHz transducer, and a towed multi-channel hydrophone array. Along mission profiles where the AUV is fully submerged but too shallow for bottom-lock navigation, one challenge is accurate localization of the AUV. Localization was performed in post-processing using multi-channel back-propagation methods applied to AUV source signals received at mooring hydrophones in the NESBA network as well as ship-towed sound source signals received at the AUV-towed array. Uncertainty in the localization estimates due to spatiotemporal sound speed changes was investigated, and hydrophone mooring tilt angle was determined by minimizing the localization uncertainty. Following localization, this AUV acoustic data was used to investigate local seafloor sub-bottom properties and the acoustic effects of biological scattering layers and varying physical oceanography. [Work supported by the Office of Naval Research.]
7
Kelly, Mark, et Chengzhi Shi. « Ray tracing of long-range underwater acoustic vortex wave propagation ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A219. http://dx.doi.org/10.1121/10.0018712.
Texte intégralRésumé :
The underwater acoustic communications environment is severely band-limited, which leads to a bottleneck in data transfer. Existing methods of data transfer in underwater acoustic communications applications typically rely primarily on conventional temporal and frequency modulation techniques and achieve bit rates peaking at approximately 40 kb/s. One method of easing the bottleneck and increasing the data rate is to explore further potential degrees of freedom which may be utilized. Acoustic orbital angular momentum (OAM) is a physical quantity that characterizes the rotation in a propagating helical pressure wavefront. The unique phase patterns of OAM carrying vortex waves form an orthogonal basis which may be useful as an additional degree of freedom in acoustics communications applications; however, the long-distance propagation of these waves is largely unstudied. By employing BELLHOP’s ray tracing algorithm, the dominant features of a propagating OAM carrying vortex wave are tracked over long ranges (to and beyond 1 km) under various environmental conditions. This provides essential guidance in the design of the sending and receiving arrays of high-speed underwater communications systems, which rely on multiplexing acoustic OAMs.
8
Becker, Kyle M., Robert H. Headrick et Thomas C. Weber. « “Mud acoustics” and the ocean acoustics program ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A100. http://dx.doi.org/10.1121/10.0015675.
Texte intégralRésumé :
Shallow water acoustics is one of the major thrusts of the Office of Naval Research Ocean Acoustics Program and has been an important area of interest to Navy programs since at least the work of Pekeris, Ewing, and Worzel in the 1940’s. In the 1950’s and early 1960’s, there was a flurry of activity both in the US and UK focused on propagation within and reflection from the seabed and the acoustical characteristics marine sediments. This work formed the basis of a research program carried out by the applied ocean acoustics branch of the acoustics division at the Naval Research Laboratory in the 1970’s. In April 1991, with the Cold War coming to an end, and a shift in interest from blue water to the littorals, ONR sponsored a workshop on shallow water acoustics at the Woods Hole Oceanographic Institution. This meeting, including underwater acousticians, geologists, geophysicists, and physical oceanographers, largely set the stage for the next 30 years of shallow water acoustics research supported by ONR. Prominent efforts include the ONR Geoclutter Program and the Shallow Water 2006 experiments, both focused on regions dominated by sandy bottoms. This talk describes more recent efforts in regions characterized by muddy bottoms.
9
Hsu, Jin-Chen, Herwandi Alwi, Chun-Hao Wei, Kai-Li Liao et Che-Ting Huang. « Reflections of High-Frequency Pulsed Ultrasound by Underwater Acoustic Metasurfaces Composed of Subwavelength Phase-Gradient Slits ». Crystals 13, no 5 (20 mai 2023) : 846. http://dx.doi.org/10.3390/cryst13050846.
Texte intégralRésumé :
We numerically and experimentally investigated the behavior of high-frequency underwater ultrasounds reflected by gradient acoustic metasurfaces. Metasurfaces were fabricated with a periodic array of gradient slits along the surface of a steel specimen. The finite element method was adopted for the acoustics–structure interaction problem to design the metasurfaces and simulate the reflected fields of the incident ultrasound. Our metasurfaces yielded anomalous reflection, specular reflection, apparent negative reflection, and radiation of surface-bounded modes for ultrasonic waves impinging on the metasurfaces at different incident angles. The occurrence of these reflection behaviors could be explained by the generalized Snell’s law for a gradient metasurface with periodic supercells. We showed that at some incident angles, strong anomalous reflection could be generated, which could lead to strong retroreflection at specific incident angles. Furthermore, we characterized the time evolution of the reflections using pulsed ultrasound. The simulated transient process revealed the formation of propagating reflected ultrasound fields. The experimentally measured reflected ultrasound signals verified the distinct reflection behaviors of the metasurfaces; strong anomalous reflection steering the ultrasound pulse and causing retroreflection was observed. This study paves the way for designing underwater acoustic metasurfaces for ultrasound imaging and caustic engineering applications using pulsed ultrasound in the high-frequency regime.
10
KWON, HYU-SANG, YOUNG-CHUL CHOI, JIN-HO PARK et DOO-BYUNG YOON. « AN ENHANCED REFLECTION REMOVAL TECHNIQUE AND ITS APPLICATIONS ». Modern Physics Letters B 22, no 11 (10 mai 2008) : 1153–58. http://dx.doi.org/10.1142/s0217984908015991.
Texte intégralRésumé :
Electroacoustic transducers using piezoelectric materials are popular in various applications such as underwater acoustics, ultrasound, earthquakes and elastic wave propagations. Especially, they are widely used in non-destructive testing for ultrasonic or acoustic emission transducers. In general, they generate and receive waves through media to find meaningful targets or physical characteristics of materials. However, in most uses, the media are bounded with finite dimensions, therefore there are multiple transmitting paths reflected from the boundaries. Such reflections corrupt the principal path signal to be analyzed. To overcome this problem, gating technique to gate successively transmitting and receiving signals, in other words, tone-burst signal technique, is most representatively used. This basically isolates the direct signal before the arrival of reflected signals in the time domain, and therefore it is also described as time windowing or time-selective windowing techniques without loss of generality. These techniques have inherent overlap problems invoked by long pulse duration, especially slightly damped signals or low frequency waves. An enhancement technique of shortening the pulses by digital filtering is proposed and successively applied in practical uses. It can isolate the principal path signal from reflected signals. Thereafter the signal can be perfectly recovered after removing reflections.
11
Transtrum, Mark K., Jay C. Spendlove et Tracianne B. Neilsen. « Information geometry for environmental inversions in ocean acoustics ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A176. http://dx.doi.org/10.1121/10.0018573.
Texte intégralRésumé :
Environmental inversions in ocean acoustics require the simultaneous estimation of many unknown parameters. Broad studies of multi-parameter models from diverse fields have shown that such inference problems are universally sloppy. Sloppiness is a phenomenon in which the predictions of a model are insensitive to all but a few key combinations of parameters. Sloppy model analysis is based on information geometry, an application of differential geometry to statistics. In this talk, we give an overview of information geometry for underwater acoustics models for environmental inversion, focusing on transmission loss (TL) in range-independent normal mode models. We demonstrate that these models are sloppy and how the geometry directly relates the information content of acoustic data to the relevance of environmental parameters. In particular, the model manifold quantifies what environmental information is encoded in ocean sounds and how unidentifiable parameters can be removed from the model to give a simplified, identifiable ocean acoustics model of comparable accuracy. We summarize physical insights revealed by this information geometry analysis for ocean inversion. [Work supported by Office of Naval Research]
12
Gunderson, Aaron. « 3D finite element modeling techniques and application to underwater target scattering ». Journal of the Acoustical Society of America 151, no 4 (avril 2022) : A54. http://dx.doi.org/10.1121/10.0010637.
Texte intégralRésumé :
Underwater acoustic target scattering measurements rely on high-fidelity modeling for experimental comparison and understanding. Three-dimensional (3D) finite element models are well suited for this purpose, as they can account for arbitrary or unknown target properties and configurations/orientations within complex and asymmetrical seafloor environments. High acoustic frequencies and large physical distances associated with in situ scattering measurements pose challenges to 3D modeling efforts in terms of model sizes and runtimes. Certain model considerations must be made to keep the 3D model computationally efficient, yet accurate in predictive capability. Numerically determined Green’s functions are demonstrated to permit 3D model reduction, while still preserving far-field scattering prediction capability through the Helmholtz–Kirchhoff integral. By determining Green’s functions within the model, they need not be known or estimated for complex ocean environments a priori. Nontraditional scattering formulations and a survey of boundary truncation methods also are explored and implemented for maximal accuracy within small 3D computational domains. Model results for canonical elastic targets within varying seafloor environments are shown and compared to theory and experimentation. [Work supported by the Strategic Environmental Research and Development Program and by the Office of Naval Research, Ocean Acoustics.]
13
Gunderson, Aaron M. « 3D finite element modeling techniques and application to underwater target scattering ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A217. http://dx.doi.org/10.1121/10.0018705.
Texte intégralRésumé :
Underwater acoustic target scattering measurements rely on high fidelity modeling for experimental comparison and understanding. Three-dimensional (3D) finite element models are well suited for this purpose, as they can account for arbitrary or unknown target properties and configurations/orientations within complex and asymmetrical seafloor environments. High acoustic frequencies and large physical distances associated with in situ scattering measurements pose challenges to 3D modeling efforts in terms of model sizes and runtimes. Certain model considerations must be made to keep the 3D model computationally efficient, yet accurate in predictive capability. Numerically determined Green’s functions are demonstrated to permit 3D model reduction, while still preserving far-field scattering prediction capability through the Helmholtz-Kirchhoff integral. By determining Green’s functions within the model, they need not be known or estimated for complex ocean environments a priori. Nontraditional scattering formulations and a survey of boundary truncation methods also are explored and implemented for maximal accuracy within small 3D computational domains. Model results for canonical elastic targets within varying seafloor environments are shown and compared to theory and experimentation. [This work has been supported by the Strategic Environmental Research and Development Program, and by the Office of Naval Research, Ocean Acoustics.]
14
Guo, Zheng, Aijun Song, Mohammad Towliat, Leonard Cimini et Xiang-Gen Xia. « Lake experimentation of in-band full-duplex underwater acoustic communications ». Journal of the Acoustical Society of America 151, no 4 (avril 2022) : A235. http://dx.doi.org/10.1121/10.0011173.
Texte intégralRésumé :
In-band full-duplex (IBFD) communications is a promising technique to achieve spectral-efficient communication in the underwater environment. Characteristics of self-interference and methods to suppress the self-interference are crucial to attaining IBFD acoustic communications. In this effort, we analyze the characteristic of the self-interference for the underwater acoustic channel through experimental measurements. Self-interference reduction using physical separation and digital cancellation is investigated under different transmitter-receiver geometries. An iterative IBFD receiver combining joint channel estimation, SI cancellation, and multichannel decision feedback equalizer is developed. The feasibility of coherent IBFD underwater acoustic communications was tested in a lake environment. The self-interference suppression methods and the receiver performance were evaluated using the experimental measurements. IBFD communications was demonstrated at 80 m. With 10 dB local self-interference source level reduction, IBFD communications was extended to the 170 m range. [Work supported by the National Science Foundation.]
15
Dugnani, Roberto. « Novel Transducer for Characterization of Low-Impedance Materials ». Key Engineering Materials 558 (juin 2013) : 435–44. http://dx.doi.org/10.4028/www.scientific.net/kem.558.435.
Texte intégralRésumé :
Piezoelectric materials such as lead-zirconate-titanate (PZT), lead-metaniobate, and piezo-composites are the materials of choice for acoustic imaging in medical diagnosis as well as underwater ultrasonic microphones and underwater sonar. PZT materials have the advantage of having high electro-mechanical coupling, low internal losses and excellent environmental durability. Nonetheless, in order to improve energy transmission the high acoustic impedance of piezoelectric ceramics needs to be matched to the lower acoustic impedance of biological tissues and water. For actuators resonated in their thickness mode, energy transmission can be improved by means of intermediate layers of material of carefully selected thicknesses and acoustic properties. Sometimes a backing layer is also added to the back of the actuator to damp the acoustic back-wave. The process of making these types of transducers is generally costly due to the nature of the manufacturing process and the required level of accuracy. This paper describes an inexpensive method of manufacture low-cost, low-impedance, piezoelectric transducers. The fundamental physical principles behind this new type of sensor-actuator, as well as various examples of imaging low-impedance targets using a prototype of this newly developed sensor-actuator system will be presented.
16
Diniz, Pedro, et Rogério Calazan. « Integrating modeled environmental variability into neural network training for underwater source localization ». Journal of the Acoustical Society of America 153, no 6 (1 juin 2023) : 3201. http://dx.doi.org/10.1121/10.0019632.
Texte intégralRésumé :
Supervised machine learning (ML) is a powerful tool that has been applied to many fields of underwater acoustics, including acoustic inversion. ML algorithms depend on the existence of extensive labeled datasets, which are difficult to obtain for the task of underwater source localization. A feed-forward neural network (FNN) trained on imbalanced or biased data may end up suffering from a problem analogous to model mismatch in matched field processing (MFP), that is, producing incorrect results due to a difference between the environment sampled by the training data and the actual environment. To overcome this issue, physical and numerical propagation models can act as data augmentation tools to compensate for the lack of comprehensive acoustic data. This paper examines how modeled data can be effectively used for training FNNs. Mismatch tests compare the output from a FNN and MFP and show that the network becomes more robust to various kinds of mismatches when trained on diverse environments. A systematic analysis of how the training dataset's variability impacts a FNN's localization performance on experimental data is carried out. Results show that networks trained with synthetic data achieve better and more robust performance than regular MFP when environment variability is taken into account.
17
Badiey, Mohsen, Lin Wan et Christian D. Escobar-Amado. « Frequency dependent effects of environmental parameters on the broadband acoustic wave propagation in shallow water waveguides ». Journal of the Acoustical Society of America 154, no 4_supplement (1 octobre 2023) : A134. http://dx.doi.org/10.1121/10.0023033.
Texte intégralRésumé :
Acoustic wave intensity plays a crucial role in underwater acoustics, particularly in shallow water regions in which the signal suffers substantial energy fluctuations. The physical properties of the environment significantly impact the intensity of broadband acoustic waves in shallow water waveguides. The accuracy of the intensity is vital for the reliability of any inverse algorithm used to obtain the physical properties of the waveguide boundaries. In this paper, we explore the effects of sound speed fluctuations in the water column on broadband acoustic propagation across different frequencies. Our observations reveal that at higher frequencies the sound intensity is more sensitive to oceanographic variability. This poses challenges for geo-acoustic inversions when parameters in the water column are not well-known, particularly at higher frequencies. To validate our findings, we present simulations using normal modes and parabolic equation with examples from recent experimental observations conducted on the New England Mud Patch Area and the continental shelf region of the United States during 2017, 2021, and 2022. These experiments provide valuable insight into the intricate behavior of acoustic waves in shallow water environments at different frequency bands. [Work supported by ONR (Grant No. N00014-21-1-2760).]
18
Kukshtel, Natalie, Ying-Tsong Lin, Andone C. Lavery, Scott Loranger, Jason Chaytor et Glen Gawarkiewicz. « Sound propagation measurements using an autonomous underwater vehicle acoustic array in the New England shelf break acoustics network ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A27. http://dx.doi.org/10.1121/10.0015425.
Texte intégralRésumé :
The New England shelf break is a highly dynamic region, which experiences complex spatial and temporal water-column variations due to interactions with warm core rings originating from the gulf stream. This widely varying ocean environment leads to changes in sound speed and acoustic propagation. Acoustic payload-equipped autonomous underwater vehicles (AUVs) are advantageous for sound propagation measurements in such environments due to their ability to detect changes with greater spatial resolution compared to fixed moorings. An AUV-towed acoustic array was tested and deployed in the New England Shelf Break Acoustics (NESBA) experiment in May 2021. The acoustic AUV system was comprised of a modified REMUS 600 vehicle, a hull-mounted 3.5 kHz transducer, and a towed multi-channel linear hydrophone array. The AUV sound source was tested at the Dodge Pond Naval Facility to characterize the effect of AUV body resonance, and the resulting calibration was incorporated into the data processing. Propagation paths between the AUV, acoustic moorings, and a ship-towed sound source were studied to investigate the acoustic effects of varying physical oceanographic conditions and biological scattering layers. These measurements also enabled investigation of the local seabed conditions and sub-bottom layering structure. [Work supported by the Office of Naval Research.]
19
Tang, Yifan, et Shuyu Lin. « Systematic design and experimental realization of a radially cascaded spherical piezoelectric transducer ». Journal of the Acoustical Society of America 154, no 3 (1 septembre 2023) : 1838–49. http://dx.doi.org/10.1121/10.0021073.
Texte intégralRésumé :
As a critical component of ultrasonic vibration systems, piezoelectric transducers play an essential role in various practical application scenarios. Recent advances in spherical transducers have been widely used in underwater sound and structural health monitoring, while the cascaded spherical piezoelectric transducer with arbitrary piezoceramic shell thickness has not been investigated. Here, we propose a radially cascaded spherical piezoelectric transducer (RCSPT) and derive its electromechanical equivalent circuit with mechanical losses, dielectric losses, and load mechanical impedances. The resulting device is composed of three concentric spherical metal shells and two radially polarized spherical piezoceramic shells. The underlying physical mechanism is the inverse piezoelectric effect, which converts electrical signals into mechanical vibrations. The effects of the spherical piezoceramic shell's thickness and location on the RCSPT are studied. We also analyze the effects of mechanical losses, dielectric losses, and load mechanical impedances on the modulus of input electric impedance of the cascaded spherical transducer. The experiments are conducted to verify the electromechanical characteristics of the resulting device, which are in good agreement with the simulated results and theoretical predictions. Our methodology will offer new possibilities for designing RCSPTs and may promote applications in various fields, such as underwater acoustic detection and structural health monitoring.
20
Lee, Junsu, Kyounghun Been et Wonkyu Moon. « An improved lumped parameter model of the single free-flooded ring transducer using Helmholtz–Kirchhoff integral solution ». Journal of the Acoustical Society of America 154, no 4_supplement (1 octobre 2023) : A228. http://dx.doi.org/10.1121/10.0023365.
Texte intégralRésumé :
The Helmholtz-Kirchhoff integral (HKI) may be considered as the boundary element method (BEM) used to calculate the acoustic pressure at any position in the 3D-radiation problem from a vibrating surface. This method provides valuable insights into the radiation characteristics of vibrating structures, which may offer significant information and tools to underwater transducer design engineers during the early stages of development. It may save considerable computational costs in the design processes for the underwater transducer such as Hull Mount Sonar. This study illustrates usefulness of the HKI-based approach by developing a simple model of the Free Flooded Ring (FFR) transducer using a piezoelectric ring model and the HKI solution on the surface acoustic pressure of the ring through their physical conditions on their connected interfaces. The FFR transducer is widely utilized as a low-frequency acoustic source in underwater environments due to its broad operating frequency bandwidth and relatively small size. The developed approach aims to construct a precise model that considers the sound-structure interactions between the piezoelectric ring and the acoustic medium around it. To validate the accuracy of the proposed method, the acoustic pressure and electrical admittance are compared with those obtained through finite element method (FEM) simulations.
21
Filippov, Vladislav, Ilya Galimov, Aleksandr Markov et Vladimir Chereshnev. « Survey methods for seaport waterworks on the example of the Balaklava Bay objects ». E3S Web of Conferences 457 (2023) : 02030. http://dx.doi.org/10.1051/e3sconf/202345702030.
Texte intégralRésumé :
The article reflects materials on modern advanced methods of surveying the existing mooring and shore protection structures of the Balaklava Bay of the Republic of Crimea. The main purpose of the survey was to determine the technical condition and the actual bearing capacity of hydraulic structures, taking into account the existing physical wear. Article discusses the issues and problems of engineering survey and information modeling of marine port hydraulic structures using the example of existing objects. The application of such modern methods of inspection of hydraulic structures as sonar areal survey, ultrasonic thickness measurement, geo-radar study, seismic acoustic study of the depth of immersion of piles, underwater survey by means of remotely operated underwater vehicles is illustrated and analysed in present article. The experience of creating digital counterparts of port hydraulic structures using modern domestic software is considered. In the course of the work performed, it was confirmed that the exceptionally completeness and versatility of field research using modern equipment, as well as mathematical modeling in software and computing complexes, taking into account actual physical wear, can contribute to obtaining real reliable information about the available reserves of bearing capacity, durability and safety of the studied structures.
22
DeCourcy, Brendan J., Ying-Tsong Lin et Jason Chaytor. « Influence of stratified sub-bottom sediment layers on acoustic simulations in the New England shelf break environment ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A27. http://dx.doi.org/10.1121/10.0015427.
Texte intégralRésumé :
During the 2021 New England Shelf Break Acoustics (NESBA) Experiment, a large number of acoustic signal transmissions along and across the continental shelf were compared with combined physical oceanographic (PO) and ocean acoustic (OA) models. This experiment aimed to examine the influence of environmental changes in the water column on acoustic propagation in the shelf break environment. Sub-bottom surveys carried out by a combination of autonomous underwater vehicles (AUVs) and ship-board instruments revealed distinctly stratified sediment layers. Accounting for the properties of sub-bottom sediment layers is an integral component of diagnosing mismatch between experimental acoustic data and simulations, as these properties can influence the attenuation and scattering of received signals. A comparison of homogeneous half-space bottom models calculated at sea in May of 2021 and improved models which incorporate the results of sub-bottom surveys is presented, and the importance of this modeling consideration is examined for the purposes of data and model comparisons. [This work was supported by the Office of Naval Research.]
23
Johnson, Jennifer J., Ying-Tsong Lin, Glen Gawarkiewicz, Brendan J. DeCourcy et Arthur E. Newhall. « Variations of acoustic ducting in the presence of gulf stream warm core rings at the New England shelfbreak ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A27. http://dx.doi.org/10.1121/10.0015424.
Texte intégralRésumé :
The physical oceanographic (PO) conditions at the New England shelfbreak have become more dynamic with increased warming and meandering of the gulf stream. Consequently, underwater sound propagation in the area has also become more variable. The most profound PO feature that breaks off from Gulf Stream instabilities is warm core rings, which have complex interactions with bathymetry and seasonal shelf water masses. Warm core rings can cause shelf water streamers to extend offshore, resulting in surface and/or subsurface acoustic ducting conditions. This study observed acoustic surface ducting and breakdown conditions induced by a shelf water streamer at the New England shelfbreak. Ducting conditions were variable when a subsequent warm core ring intruded the acoustic source and receiver network, mixing with the shelf water streamer and influencing the sound propagation during and after the acoustic duct breakdown period. The field observations were also compared with a broadband numerical model. With increasing gulf stream warm core ring formations, streamer induced surface ducts are becoming more relevant in shelf break acoustics. [Work supported by the Office of Naval Research.]
24
Malyushevskaya, Antonina P., Piotr Koszelnik, Olena Mitryasova, Anna Yushchishina, Andrii Mats, Dorota Papciak et Monika Magdalena Zdeb. « Hybrid Water Disinfection Process Using Electrical Discharges ». Processes 12, no 9 (29 août 2024) : 1846. http://dx.doi.org/10.3390/pr12091846.
Texte intégralRésumé :
An analysis of the physical and chemical phenomena accompanying electrical discharges is carried out, and the main factors influencing microorganisms’ abatement are studied. The similarity of the cavitation processes in water systems induced by underwater electric discharges and ultrasound is experimentally demonstrated. The characteristic features of electrical discharge in the cavitation mode, providing effective water disinfection with electric discharges with a significantly reduced amount of active chlorine, are identified in order of importance. The inactivation of microorganisms is intensified, firstly, by the generation of chemically active particles from the water medium itself, due to the integral action of the electro-discharge cavitation of the whole treated volume, and by local shock waves, acoustic flows, and ultraviolet radiation in the area near the cavitating bubbles. The main advantages of electric discharge cavitation over ultrasonic range are the wider range of high-frequency acoustic radiation inherent in an electric discharge, the high intensity and power of the cavitation processes, and the possibility of a significant increase in the volume of disinfected liquid. This study allows for a better understanding and prediction of the bacterial effects that occur during a high-voltage underwater electrical discharge.
25
Eastland, Grant. « Ocean acidification : Future effects to ocean environments and biologic response ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A62. http://dx.doi.org/10.1121/10.0018165.
Texte intégralRésumé :
Ocean acidification has become one of many consequences of our modern civilization that potentially could cause major changes to Earth’s undersea environments. There are several physical and chemical effects from acidification, one of which affects the undersea acoustic environment. There are various empirical models for acoustic absorption, but an empirical model by Francois and Garrison has a pH dependent contribution. As the ocean becomes more acidic, the pH decreases from its current value and the model predicts a reduction in the amount of acoustic absorption. The result of this absorption reduction changes the overall transmission loss of sound propagation and makes the underwater environment a “louder” place. The consequences of which would be minor complications to ocean exploration but will have a greater impact upon the undersea fauna. As the environment becomes louder, those animals that use acoustics to echolocate food, will find it more difficult to do so and others may find the environment to not be amenable to their survival. These changes are occurring on a time scale on the order of decades, so environmental acoustic monitoring of ambient conditions and large-scale migration can be utilized as an indicator of the changes to the water space.
26
Abraham, Douglas. « A survey of Lisa Zurk's contributions to physics-based signal processing in underwater acoustics ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A241—A242. http://dx.doi.org/10.1121/10.0016142.
Texte intégralRésumé :
The incorporation and exploitation of the physics of underwater acoustic propagation (including reflection and scattering) in signal and information processing can improve the performance of detection, classification, localization and tracking (DCLT) in sonar systems. This presentation will survey several areas of Prof. Lisa Zurk's research from this perspective of physics-based signal processing. Contributions are found in the areas of (i) assessing the impact of propagation through a non-stationary underwater environment on the performance of signal processing algorithms, (ii) adapting signal processing algorithms to be more robust to these environmental effects, and (iii) the exploitation of specific characteristics of the propagation channel in novel approaches to solving the above inferential objectives. Of these areas, identifying consistently observable propagation phenomena that can be exploited to improve DCLT performance is the most essential and yet the most difficult because it requires balancing just enough accuracy in the physical model with a simple enough representation to develop robust signal and information processing algorithms. Impressively, Prof. Zurk was quite successful in this crucial area of physics-based signal processing.
27
LI, W., G. R. LIU et X. M. ZHANG. « SIZE IDENTIFICATION OF UNDERWATER OBJECTS FROM BACKSCATTERING SIGNALS OF ARBITRARY LOOKING ANGLES ». Journal of Computational Acoustics 12, no 03 (septembre 2004) : 301–17. http://dx.doi.org/10.1142/s0218396x04002298.
Texte intégralRésumé :
The inverse problem of determining the size, shape and orientation of a submerged object using the scattered field data is studied. Based on the physical optics approximate, the profile function of the object is found directly proportional to its ramp response that is the second integral of the impulse response. Through analyzing the feature of the ramp response in different computed frequency ranges, it is found that the low-frequency data are essential to the shape of the underwater object while the high-frequency data are very important to the size of the object. Therefore, when employing the high-frequency data to compute the ramp response, the edge of the object can only be highlighted in the illuminated region at certain aspect. Based on this finding, a new method is developed to estimate the size of underwater objects. The present method uses different frequency ranges to determine different parameters of the underwater objects so as to achieve the best accuracy. A number of examples are presented to demonstrate the effectiveness of the present method in using the ramp response technique to identify the size of both rigid and elastic bodies.
28
Shi, Chengzhi. « Acoustic angular momenta and their applications ». Journal of the Acoustical Society of America 151, no 4 (avril 2022) : A91. http://dx.doi.org/10.1121/10.0010757.
Texte intégralRésumé :
Acoustic angular momentum is a physical quantity characterizing the rotation of pressure and local particle velocity fields. The acoustic angular momentum was first observed in vortex waves and was found to have many interesting physics including pseudospin based topological effects, spin-momentum locking, and trapping potential for contactless particle manipulations. In this presentation, we will introduce the categorization of acoustic angular momentum into spin and orbital angular momenta. While airborne sound is a longitudinal wave that was long thought to be spinless, we observed the acoustic spin in some special cases. The spin-momentum locking and spin induced torque for particle manipulation were experimentally demonstrated. In addition, the application of acoustic orbital angular momentum in high-speed communication will be discussed. These novel physical acoustic properties have many more applications ranging from underwater exploration to biomedical engineering.
29
Duda, Timothy F., Arthur E. Newhall, Ying-Tsong Lin, James Lynch, Glen Gawarkiewicz, Weifeng G. Zhang, Karl R. Helfrich, Pierre F. Lermusiaux, Keith von der Heydt et John Kemp. « Twenty-first century outer continental shelf and shelfbreak acoustics research : Methods, tools, and progress ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A44. http://dx.doi.org/10.1121/10.0015484.
Texte intégralRésumé :
New findings in outer-shelf and shelfbreak acoustics have been enabled by experimental and computational advances over the last 25 years. The details of sound field variability caused by highly dynamic conditions often found in this regime have become measurable through advances in data collection technology. Furthermore, these details can now be computationally modeled more realistically. The coupling of more plentiful data and higher fidelity modeling has uncovered many new behaviors. It has also allowed us to quantify the effects on sound level and phase structure (coherence) of many outer-shelf physical features, as well as the temporal aspects of these variations. Key tools have been vessel dynamic positioning, underwater position finding, small mobile platforms, high-capacity multichannel receive arrays, data-assimilating regional ocean dynamical models, nonlinear wave modeling, and three-dimensional acoustic propagation modeling. Examples from the published work of the authors, and the work of others, of how these advances have fostered new knowledge of specific processes will be presented, as well as present-day challenges inspired by recent findings.
30
Olson, Allen H., et Stephen P. Sutton. « The physical mechanisms leading to electrical breakdown in underwater arc sound sources ». Journal of the Acoustical Society of America 94, no 4 (octobre 1993) : 2226–31. http://dx.doi.org/10.1121/1.407493.
Texte intégral
31
Kha, Jamie, Mahmoud Karimi et Laurent Maxit. « Acoustic radiation from a baffled finite shell in an underwater waveguide ». Journal of the Acoustical Society of America 154, no 4_supplement (1 octobre 2023) : A55. http://dx.doi.org/10.1121/10.0022776.
Texte intégralRésumé :
Analytical modelling of vibroacoustic systems can help us to understand the physical phenomena involved in more complex problems, and it provides a benchmark solution and reference upon which more complex systems can be built. In the present work, the system of interest consists of a finite elastic cylindrical shell inserted in infinitely rigid cylindrical baffles and immersed in an underwater acoustic waveguide. The latter consists of a finite fluid layer bounded by an upper free surface and a lower rigid floor. In such a fluid domain, the acoustic waves radiated from the excited shell will exhibit reflections off the boundaries. This phenomenon is modelled by the image-source theory and embedded in the fluid loading term, which intervenes in the shell equations. Investigations into the influence on the finiteness of the elastic shell, types of supports (i.e., simply supported, clamped, free, and combinations of these), and depth of the waveguide on the shell’s acoustic radiation are presented.
32
Transtrum, Mark K., Jay C. Spendlove et Tracianne B. Neilsen. « Parameter reduction for environmental inversions in ocean acoustics ». Journal of the Acoustical Society of America 154, no 4_supplement (1 octobre 2023) : A41. http://dx.doi.org/10.1121/10.0022734.
Texte intégralRésumé :
Environmental inversions in ocean acoustics require the simultaneous estimation of many unknown parameters. Unfortunately, many environmental parameters are unidentifiable from available measurements. Recent work in statistical physics has developed tools for analyzing such models using information geometry. The Manifold Boundary Approximation (MBAM) systematically prunes unidentifiable parameters to produce an identifiable model that can be analyzed with traditional statistical methods. In this talk, we report on progress applying MBAM to underwater acoustics models forenvironmental inversion, focusing on transmission loss (TL) in range-independentnormal mode models. The key technical advance is the calculation of geodesics (a generalization of straight lines to curved surfaces) on a geometric representation of the model known as the model manifold. Geodesics inform which environmental parameters are constrained by ocean sounds and guide the removal of unidentifiable parameters. The result is a simplified, identifiable model of comparable accuracy. We summarize physical insights revealed by MBAM applied to ocean inversion. [Work supported by Office of Naval Research.]
33
Hou, Jiacheng, Zhongquan Charlie Zheng et John S. Allen. « Time-domain simulation of acoustic wave scattering and internal propagation from a gas bubble of various shapes ». Journal of the Acoustical Society of America 153, no 3 (mars 2023) : 1468–79. http://dx.doi.org/10.1121/10.0017386.
Texte intégralRésumé :
Acoustic scattering and resonances of gas bubbles are computed using a time-domain simulation based on numerical solutions of the conservation laws. The time histories of scattered pressure and fluid velocity, outside and inside the bubble, are obtained simultaneously from an immersed-boundary method allowing for the investigation of exterior and interior fields for non-spherical geometries. The acoustic resonances of the bubble are investigated for various bubble sizes, shapes, and inner gas parameters and compared in limiting cases to the partial wave scattering solutions for spherical bubbles. The dynamics of the gas motion and its associated contribution to resonance response has received little attention in previous analytical and numerical formulations. In this study, the acoustic propagation and motion inside the interior gas is investigated with respect to the monopole resonance with the combined time-domain simulation and immersed-boundary method. For the non-spherical prolate and oblate shapes, the scattering and resonance behaviors are compared with the approximate analytical results based on the shape factor method. The simulation method can be extended to less-understood shapes relevant to underwater and physical acoustics, such as “pancake-shaped” or “cigar-shaped” bubbles, as well as to spatial and time-dependent forcing.
34
Kadhafi, Muammar. « Subsea Pipeline Corrosion : A Review of Detection Methods, Mechanisms and Prevention Strategies ». Collaborate Engineering Daily Book Series 1, no 2 (28 décembre 2023) : 101–5. http://dx.doi.org/10.62012/collaborate.v1i2.52.
Texte intégralRésumé :
Subsea pipelines are one of the important components in the oil and gas industry, which function to transport fluids from wells to surface facilities. However, subsea pipelines are susceptible to corrosion due to interaction with the aggressive marine environment, which can cause structural damage, leaks, and even failure of the pipeline. Therefore, effective and efficient underwater pipe corrosion detection methods, mechanisms, and prevention strategies are needed. This article aims to provide an overview of various detection methods, mechanisms, and prevention strategies for undersea pipeline corrosion that have been developed by researchers. Subsea pipeline corrosion detection methods can be divided into two categories, namely internal methods and external methods. Internal methods involve measuring physical parameters inside the pipe, such as pressure, flow, temperature, and fluid composition. External methods involve the use of non-destructive inspection technologies, such as ultrasonic, radiographic, electromagnetic, and acoustic.
35
Dahl, Peter H., A. Keith Jenkins, Brandon Casper, Sarah E. Kotecki, Victoria Bowman, Christiana Boerger, David R. Dall'Osto, Matthew A. Babina et Arthur N. Popper. « Physical effects of sound exposure from underwater explosions on Pacific sardines (Sardinops sagax) ». Journal of the Acoustical Society of America 147, no 4 (avril 2020) : 2383–95. http://dx.doi.org/10.1121/10.0001064.
Texte intégral
36
Marston, Philip L. « Selected research in physical, structural, and underwater acoustics at WSU associated with Logan Hargrove’s ONR scientific program ». Journal of the Acoustical Society of America 150, no 4 (octobre 2021) : A139. http://dx.doi.org/10.1121/10.0007901.
Texte intégral
37
Wang, Xiaoyu, et Shuyu Lin. « Analysis on the Radial Vibration of Longitudinally Polarized Radial Composite Tubular Transducer ». Sensors 20, no 17 (25 août 2020) : 4785. http://dx.doi.org/10.3390/s20174785.
Texte intégralRésumé :
The radial vibration of a radial composite tubular transducer with a large radiation range and power capacity is studied. The transducer is composed of a longitudinally polarized piezoelectric ceramic tube and a coaxial outer metal tube. Assuming that the longitudinal length is much larger than the radius, the electromechanical equivalent circuits of the radial vibration of a piezoelectric ceramic long tube and a metal long tube are derived and obtained for the first time following the plane strain theory. As per the condition of the continuous forces and displacements of two contact surfaces, the electromechanical equivalent circuit of the tubular transducer is obtained. The radial resonance/anti-resonance frequency equation and the expression of the effective electromechanical coupling coefficient are obtained. Then, the effects of the radial geometry dimension of the transducer on the vibration characteristics are analyzed. The theoretical resonance frequencies, anti-resonance frequencies, and the effective electromechanical coupling coefficients at the fundamental mode and the second mode are in good agreement with the finite element analysis (FEA) results. The study shows that when the overall size of the transducer is unchanged, as the proportion of piezoelectric ceramic increases, the radial resonance/anti-resonance frequency and the effective electromechanical coupling coefficient of the transducer at the fundamental mode and the second mode have certain characteristics. The radial composite tubular transducer is expected to be used in high-power ultrasonic wastewater treatment, ultrasonic degradation, and underwater acoustics, as well as other high-power ultrasonic fields.
38
Godin, Oleg A. « Wind, sea swell, and excitation of atmospheric waveguides by underwater earthquakes ». Journal of the Acoustical Society of America 151, no 4 (avril 2022) : A159—A160. http://dx.doi.org/10.1121/10.0010970.
Texte intégralRésumé :
Powerful underwater sources, such as volcano eruptions and large explosions, can generate infrasonic waves, which remain detectable at distant receivers on shore. Evers et al. [Geophys. Res. Lett. 41, 1644–1650 (2014)] described observations of acoustic signals in air from the 2004 Macquarie Ridge submarine earthquake, by the infrasonic array IS05AU of the International Monitoring System. Infrasound propagated in the tropospheric and stratospheric waveguides and was received 1325 km from the epicenter. Specific physical mechanisms of the excitation of guided infrasonic waves by underwater sources are not fully understood. Here, we emphasize the potential role of local meteorological conditions. Scattering of ballistic waves from the earthquake epicenter by wind waves and sea swell on the ocean surface is a potent mechanism of excitation of normal modes in hydroacoustic waveguides (T-waves) [Godin, J. Acoust. Soc. Am. 150, 3999–4017 (2021)]. We investigate the hypothesis that the scattering of ballistic waves at the ocean surface also explains the earthquake excitation of acoustic normal modes in the tropospheric and stratospheric waveguides. Relative significance of the surface scattering and the previously proposed evanescent coupling mechanism is studied as a function of the wind speed, wave frequency, and the source depth.
39
THOMSON, DAVID J., et M. ELIZABETH MAYFIELD. « AN EXACT RADIATION CONDITION FOR USE WITH THE A POSTERIORI PE METHOD ». Journal of Computational Acoustics 02, no 02 (juin 1994) : 113–32. http://dx.doi.org/10.1142/s0218396x94000099.
Texte intégralRésumé :
In the applications of the parabolic equation (PE) to underwater sound propagation, the radiation condition as z → ∞ is usually approximated numerically by appending an absorbing layer below the physical ocean bottom and imposing a simple pressure-release boundary condition at the base of the layer. A similar artifice is needed to prevent unphysical reflections from the top of the air layer in the applications of the PE to atmospheric sound propagation. In this paper, we replace this approximate boundary treatment for the standard PE with an exact, nonlocal boundary condition that can be applied along the sea-bottom or upper-atmosphere interface. Moreover, we make use of an exact relationship between the solution ψ of the standard PE and the solution p of the Helmholtz equation to postprocess the ψ field obtained using this nonlocal boundary condition into the p field. The effectiveness of this radiation condition and the a posteriori PE scheme is demonstrated for several examples that typify underwater and outdoor sound propagation in layered media.
40
Kelly, Mark, Brian O'Donnell, Karim G. Sabra et Marsal Bruna. « Machine learning for point-to-point transmission loss estimates in ocean acoustic waveguides ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A295. http://dx.doi.org/10.1121/10.0016329.
Texte intégralRésumé :
Underwater acoustic system performance depends on several complex and dynamic environmental parameters, and simulating such performance is vital to the success of development and implementation of these systems. Because of the complexity of the environment and governing physical equations, realistic simulations can become computationally prohibitive. This is especially true of for large environments with many active systems being assessed. By utilizing convolutional neural networks (CNNs) trained on data generated by well-established physics based models (such as BELLHOP’s ray tracing algorithm), network predictions can be used lieu of physics-based models to significantly reduce the computational burden in the loop for system performance simulations. In this paper, the usefulness and limitations of using CNNs to estimate transmission loss (TL), which is a key element in determining system performance, is explored. Using BELLHOP’s ray tracing algorithm as a baseline, CNN’s were able to produce TL results with significantly lower errors than those estimates made using other estimation methods such as spherical spreading and K-nearest neighbors. This indicates that the computational costs of large underwater acoustic simulations may be shifted from inside the simulation to network training, thus allowing for more efficient traditional and Monte Carlo style simulations.
41
Sonnemann, Tim, Jan Dettmer, Charles W. Holland et Stan Dosso. « High-resolution transdimensional geoacoustic inversion using autonomous underwater vehicle data ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A146. http://dx.doi.org/10.1121/10.0015845.
Texte intégralRésumé :
We invert reflection coefficient measurements of muddy sediment layers along a 12-km seabed transect on the Malta Plateau in the Mediterranean Sea using 1711 source transmissions recorded on a 32-element linear hydrophone array with both source and array towed by an autonomous underwater vehicle. Trans-dimensional Bayesian inference using reversible jump Markov chain Monte Carlo sampling is applied to obtain posterior probability densities of the number of homogeneous sediment layers, their depths, and their geoacoustic parameters. The forward sediment acoustics model is based on the grain-shearing model which obeys physical causality and provides correlation between important geoacoustic properties. Each dataset was treated as one-dimensional seabed structure inversion carried out on high performance clusters, and inversion results for multiple data sets were combined to yield a two-dimensional subsurface profile including full uncertainty analysis. Comparisons of inversion results to piston and gravity core estimates show agreement in both geoacoustic parameter values and depths of discontinuities. In the range-dependent model constructed from inverting the entire data set, dipping and terminating layers are observed along the track with high vertical resolution on the order of 10 cm.
42
Higgins, Alex, et Martin Siderius. « Acoustic scattering from dynamic rough ocean surfaces using finite-difference time-domain modeling techniques ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A252—A253. http://dx.doi.org/10.1121/10.0016183.
Texte intégralRésumé :
Established models for underwater acoustic propagation and scattering typically assume the sea-surface to be either perfectly smooth or rough but static in time. When the sea-surface is rough and moving, received signals show anomalies such as additional transmission losses (due to scattering) and Doppler effects (due to surface motion). Understanding the mechanisms behind these anomalies leads to better sonar system designs without having to perform expensive at-sea experiments. The Finite-Difference Time-Domain (FDTD) method is ideal to predict these physical phenomena. This work presents a FDTD method implemented to model the impact of both sea-surface roughness and motion on underwater acoustic propagation. The FDTD method allows an arbitrary function to define the rough sea-surface and its time evolution. The surface characteristics are modeled using a Pierson-Moskowitz (PM) frequency spectrum. The PM surface model is simple to implement and fully defined by wind speed and direction. Time-domain results from FDTD simulations of static rough sea-surfaces are compared to an established Helmholtz integral equation (HIE) method to establish the validity of the approach. Broadband signals are used as the source waveform. Results demonstrate the anomalous transmission loss and Doppler in received signals. [Work supported by the Office of Naval Research.]
43
Wilford, Dylan C., Jennifer L. Miksis-Olds et S. Bruce Martin. « Multidimensional comparison of underwater soundscapes using the soundscape code ». Journal of the Acoustical Society of America 154, no 5 (1 novembre 2023) : 3438–53. http://dx.doi.org/10.1121/10.0022514.
Texte intégralRésumé :
The soundscape of a given habitat is a product of its physical environment, human activity, and presence of soniferous marine life, which can be used to understand ecosystem processes, habitat quality, and biodiversity. Shallow coral habitats are hotspots of biodiversity and marine life. Deep-sea coral environments, in comparison, are generally poorly understood. Four soundscapes along the U.S. Outer Continental Shelf (OCS) and one soundscape from the Great Barrier Reef were quantified to explore how differences in habitat, depth, and substrate manifest acoustically. Comparisons were made between (1) deep, cold-water and shallow, warm-water coral reefs and (2) deep-sea coral and sandy bottom habitats. Application of the soundscape code to recordings in each location seeded cluster analyses of soundscape metrics and an assessment of daily trends to quantitatively compare the soundscapes. The shallow, tropical reef soundscape differed from the deep-sea soundscapes in amplitude and impulsiveness. Differences in soundscape properties among the deep-sea soundscapes suggested cold-water coral sites produce different soundscapes than the deep sites without live hard bottom. This initial assessment of deep-sea soundscapes along the U.S. OCS provides baseline acoustic properties in a region likely to experience changes due to climate and human use.
44
SHEU, TONY W. H., S. C. CHEN, C. F. CHEN, T. P. CHIANG et DING LEE. « A SPACE MARCHING SCHEME FOR UNDERWATER ACOUSTIC WAVE PROPAGATION IN FLUID-ELASTIC MEDIA ». Journal of Computational Acoustics 07, no 03 (septembre 1999) : 185–206. http://dx.doi.org/10.1142/s0218396x99000138.
Texte intégralRésumé :
We present in this paper partial differential equations which govern three-dimensional acoustic wave propagation in fluid-elastic media. Working equations are parabolized so as to allow the analysis to be conducted in a plane-by-plane fashion. This simplification, while permitting only outgoing wave propagation, facilitates the analysis and cuts down on computing time and disk storage. To couple working equations in fluid and elastic layers, we impose physically relevant conditions on the interface. On the horizontal interface we demand continuity of the normal displacement and normal stress. In addition, physical reasoning requires that shear stresses vanish on the interface for the present analysis, which is formulated under the inviscid flow assumption. We approximate spatial derivatives with respect to θ and z using the second-order accurate centered scheme. The resulting ordinary differential equation is solved using the implicit scheme to render also second-order prediction accuracy in r. With a numerical scheme, it is highly desirable to be able to check its prediction against suitable test problems, preferably ones for which an exact solution is available. In this three-dimensional study, test problems were chosen to demonstrate the applicability of the code to the individual fluid and elastic layer. We have also verified that the code is applicable to analysis of wave propagation in water and elastic layers, across which there is an interface.
45
LEIGHTON, T. G. « FROM SEAS TO SURGERIES, FROM BABBLING BROOKS TO BABY SCANS : THE ACOUSTICS OF GAS BUBBLES IN LIQUIDS ». International Journal of Modern Physics B 18, no 25 (20 octobre 2004) : 3267–314. http://dx.doi.org/10.1142/s0217979204026494.
Texte intégralRésumé :
Gas bubbles are the most potent naturally-occurring entities that influence the acoustic environment in liquids. Upon entrainment under breaking waves, waterfalls, or rainfall over water, each bubble undergoes small amplitude decaying pulsations with a natural frequency that varies approximately inversely with the bubble radius, giving rise to the "plink" of a dripping tap or the roar of a cataract. When they occur in their millions per cubic metre in the top few metres of the ocean, bubbles can dominate the underwater sound field. Similarly, when driven by an incident sound field, bubbles exhibit a strong pulsation resonance. Acoustic scatter by bubbles can confound sonar in the shallow waters which typify many modern maritime military operations. If they are driven by sound fields of sufficient amplitude, the bubble pulsations can become highly nonlinear. These nonlinearities might be exploited to enhance sonar, or to monitor the bubble population. Such oceanic monitoring is important, for example, because of the significant contribution made by bubbles to the greenhouse gas budget. In industry, bubble monitoring is required for sparging, electrochemical processes, the production of paints, pharamaceuticals and foodstuffs. At yet higher amplitudes of pulsation, gas compression within the collapsing bubble can generate temperatures of several thousand Kelvin whilst, in the liquid, shock waves and shear can produce erosion and bioeffects. Not only can these effects be exploited in industrial cleaning and manufacturing, and research into novel chemical processes, but we need to understand (and if possible control) their occurrence when biomedical ultrasound is passed through the body. This is because the potential of such bubble-related physical and chemical processes to damage tissue will be desireable in some circumstances (e.g. ultrasonic kidney stone therapy), and undesireable in others (e.g. foetal scanning). This paper describes this range of behaviour. Further information on these topics, including sound and video files, can be found at .
46
McCarthy, Ryan A., Ananya Sen Gupta et Madison Kemerling. « Estimation and interpretation of multipath channel activity using braiding techniques ». Journal of the Acoustical Society of America 151, no 4 (avril 2022) : A267. http://dx.doi.org/10.1121/10.0011295.
Texte intégralRésumé :
Robust underwater acoustic channel estimation is critical towards improving communications efforts and enhancing awareness of changing environments. To explore these channels in-depth, machine learning algorithms are developed through feature geometric representations, referred to as “braiding,” to interpret multipath ray bundles within shallow water acoustic channels in two ways. The first application of this work predicts the number of reflections an acoustic signal may undergo through the environment by applying known physical parameters and braid features. The second application explores the importance of a braid feature within the acoustic channel for estimation purposes by using braid path information. Three unique machine learning techniques are trained to predict the applications using a diverse set of shallow water acoustic channels generated through the BELLHOP model. Machine learning models developed for the applications demonstrate high testing accuracies with an accuracy of 86.70% in the first application and an accuracy of 99.94% in the second application. As a further demonstration, braid feature representations and model predictions are used for channel estimation and determining the number of reflections using SPACE08 field data.
47
Sutin, Alexander, et Hady Salloum. « Physical models and improvement of bubble curtain for the suppression of underwater noise from a pile drive ». Journal of the Acoustical Society of America 134, no 5 (novembre 2013) : 4061. http://dx.doi.org/10.1121/1.4830821.
Texte intégral
48
Arikan, Toros, Amir Weiss, Hari Vishnu, Grant B. Deane, Andrew C. Singer et Greg Wornell. « An architecture for passive joint localization and environment learning in shallow-water underwater acoustic settings ». Journal of the Acoustical Society of America 153, no 3_supplement (1 mars 2023) : A375. http://dx.doi.org/10.1121/10.0019227.
Texte intégralRésumé :
Passive localization and tracking of a mobile emitter, and joint learning of its reverberant 3D environment, is a challenging task in various application domains. In underwater acoustic monitoring with a receiver array, for example, a submarine may need to be tracked in a setting with natural and man-made obstacles, such as seamounts or piers. If such obstacles occlude the line of sight from this vessel to the receivers, then the non-line of sight reflected arrivals from the reverberant environment must be leveraged for localization. Hence, we need to precisely map these reflective features in order to deliver robust performance. We propose a multi-stage global optimization and tracking architecture to approach this problem. Each stage of this architecture establishes domain knowledge such as synchronization and occluder mapping, which are inputs for the following stages of more refined algorithms. This approach is generalizable to different physical scales, and improves on methods that do not exploit emitter motion. We further introduce a robust neural network-based reflector estimation method that outperforms its alternatives in realistic application settings. The performance of this holistic approach is analyzed and its reliability is demonstrated both in simulation and in a real-life reverberant watertank, which models shallow-water acoustic environments.
49
Jenkins, A. Keith, Peter H. Dahl, Sarah E. Kotecki, Victoria Bowman, Brandon Casper, Christiana Boerger et Arthur N. Popper. « Physical effects of sound exposure from underwater explosions on Pacific mackerel (Scomber japonicus) : Effects on non-auditory tissues ». Journal of the Acoustical Society of America 151, no 6 (juin 2022) : 3947–56. http://dx.doi.org/10.1121/10.0011587.
Texte intégralRésumé :
Underwater explosions from activities such as construction, demolition, and military activities can damage non-auditory tissues in fishes. To better understand these effects, Pacific mackerel ( Scomber japonicus) were placed in mid-depth cages with water depth of approximately 19.5 m and exposed at distances of 21 to 807 m to a single mid-depth detonation of C4 explosive (6.2 kg net explosive weight). Following exposure, potential correlations between blast acoustics and observed physical effects were examined. Primary effects were damage to the swim bladder and kidney that exceeded control levels at ≤333 m from the explosion [peak sound pressure level 226 dB re 1 μPa, sound exposure level (SEL) 196 dB re 1 μPa2 s, pressure impulse 98 Pa s]. A proportion of fish were dead upon retrieval at 26–40 min post exposure in 6 of 12 cages located ≤157 m from the explosion. All fish that died within this period suffered severe injuries, especially swim bladder and kidney rupture. Logistic regression models demonstrated that fish size or mass was not important in determining susceptibility to injury and that peak pressure and SEL were better predictors of injury than was pressure impulse.
50
Jiang, Yanyu, Boris Katsnelson et Oleg A. Godin. « Observations of Noise due to Nonlinear Internal Waves in the ASIAEX Experiment in the South China Sea ». Journal of the Acoustical Society of America 152, no 4 (octobre 2022) : A212. http://dx.doi.org/10.1121/10.0016044.
Texte intégralRésumé :
Large, transient increases in underwater noise intensity (noise bursts) were repeatedly observed during the ASIAEX experiment on a 48-hydrophone array consisting of vertical and horizontal line arrays. The arrays were located in the South China Sea in the area known for exceptionally strong nonlinear internal waves (NIWs). The ASIAEX experiment was intended to study sound propagation in the presence of NIWs and featured extensive, concurrent acoustic and oceanographic observations. The NIWs propagating past the acoustic array site were characterized using water temperature measurements with a nearby thermistor chain. Remarkable correlation is found between noise intensity increases on the vertical array hydrophones and the NIW presence. Intensity of the noise bursts strongly depends on the hydrophone depth. The low acoustic frequencies below 30–40 Hz are primarily responsible for the noise enhancement during the NIW passage. Analysis of the spectral properties and the depth dependence of the noise intensity suggests the flow noise due to NIW-induced currents as the physical mechanism of the noise bursts in the South China Sea. [Work was supported, part, by ISF award 946/20.]