Download or read book Inference of the Ocean Sound Speed Profile Using Ambient Vertical Beam Noise written by Robert Thomas Taylor (Ph. D.) and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation introduces a novel passive acoustic method for estimating the water column sound speed using the directionality of the ambient noise field measured with a vertical line array. In the absence of anthropogenic and biological sources, wind/wave sea surface interaction is the dominant source of mid-frequency noise insonifying the undersea environment. The resulting vertical noise field is anisotropic, with the directionality of the noise environment dependent on the paths of noise from the surface to the receiver. Changes in receiver depth, and associated sound speed, affect the level of ambient vertical noise at shallow elevation angles, providing the sensitivity necessary to acoustically estimate the in situ sound speed profile. Application of a clustering algorithm to an historical set of measured sound speed profiles allows for the characterization of common regional profiles. The scale and resulting undersampled nature of the ocean environment prompts the development of a novel interpolation scheme that retains acoustically important sound speed features in the region between available measurements. Motivated by the vertical stratification and motion of the water column, the interpolation scheme determines an appropriate vertical shift in depth to align sound speed features, enabling persistent features in the interpolated range between measurements. The developed method for inferring the sound speed profile combines sparse measurements of the vertical noise environment with an historical set of measured sound speed profiles and the vertical shifting method to provide an estimate of the in situ sound speed profile, with modeled results having error on the order of common active acoustic inversion methods. Finally, the method is applied to a low-frequency vertical line array data set, with results suggesting the array aperture was insufficient, and that further experimentation is needed
Download or read book Ambient Noise in the Sea written by Robert J. Urick and published by . This book was released on 1984 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean Ambient Noise written by William M. Carey and published by Springer Science & Business Media. This book was released on 2011-03-23 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph develops the theory of noise mechanisms and measurements, and describes general noise characteristics and computational methods. The vast ambient noise literature is concisely summarized using theory combined with key representative results. The air sea boundary interaction zone is described in terms of nondimensional variables requisite for future experiments. Noise field coherency, rare directional measurements, and unique basin scale computations and methods are presented. The use of satellite measurements in these basin scale models is demonstrated. A series of appendices provides in-depth mathematical treatments which will be of interest to graduate students and active researchers.
Download or read book Sea Surface Sound written by B.R. Kerman and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 629 pages. Available in PDF, EPUB and Kindle. Book excerpt: In its relentless pursuit of further knowledge, science tends to compartmentalize. Over the years the pursuit of What might be called geophysical acoustics of the sea-surface has languished. This has occured even through there are well-developed and active research programs in underwater acoustics, ocean hydrodynamics, cloud and precipitation physics, and ice mechanics - to name a few - as well as a history of engineering expertise built on these scientific fields. It remained to create a convergence, a dialogue across disciplines, of mutual benefit. The central theme of the Lerici workshop, perhaps overly simplified, was 'What are the mechanisms causing ambient noise at the upper surface of the ocean?' What could hydrodynamicists contribute to a better understanding of breaking wave dynamics, bubble production, ocean wave dynamics, or near-surface turbulence for the benefit of the underwater acoustics community? What further insights could fluid dynamicists gain by including acoustic measurements in their repertoire of instrumentation? While every attendee will have his or her percep tions of details, it was universally agreed that a valuable step had been taken to bring together two mature disciplines and that significant co-operative studies would undoubtedly follow. The scope of the workshop was enlarged beyond its original intent to also include the question of ice-noise generation. The success of this decision can be seen in high quality of the presentations. the contribution of its disciples in the other workshop discussions and the heightened awareness and interest of we other novices.
Download or read book A Modal WKB Inversion Method for Determining Sound Speed Profiles in the Ocean and Ocean Bottom written by Kevin D. Casey and published by . This book was released on 1988 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two approaches to determining the ocean sound profile using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode dependent assumed values of the WKB phase integral as input data and use the WKB phase integral as a starting point for relating the index of refraction to depth. Inversion method one is restricted to monotonic or symmetric sound speed profiles and requires a measurement of the sound speed at one depth to convert the index of refraction profile to a sound speed profile. Inversion method two assumes that the sound speed at the surface and the minimum sound speed in the profile are known and is applicable to monotonic profiles and to general single duct sound speed profiles. For asymmetric profiles, inversion method two gives the depth difference between two points of equal sound speed in the portion of the profile having two turning points, and in the remainder of the profile it gives sound speed versus depth directly. A numerical implementation of the methods is demonstrated using idealized ocean sound speed profiles numerical experiments used to test the performance of the inversions using noisy data. The two methods are used to determine the sediment sound speed profiles in two shallow water waveguide models, and inversion method one is used to find the sediment sound speed profile using data from an experiment performed in the Gulf of Mexico. Theses. (edc).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Depth Profiling Ambient Noise in the Deep Ocean written by David Readshaw Barclay and published by . This book was released on 2011 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Deep Sound is an un-tethered, free-falling acoustic platform designed to profile the ambient noise field in the ocean from the surface to a pre-programmed depth, at which point a ballast weight is dropped and the instrument returns to the surface under its own buoyancy. Three iterations of the instrument, Mk I, II and III, have been designed, built and tested, the first two rated to descend to 9 km and the third to a full ocean depth of 11 km. During a deployment of the instrument, vertically and horizontally spaced hydrophones continuously record the ambient noise pressure time series over a large bandwidth (5 Hz - 40 kHz), returning the power spectral density, vertical and horizontal coherence as a function of depth. Deep Sound Mk I and Mk II have been deployed down to 9 km depth in the Mariana Trench and Mk I has descended three times to 5 km, 5.5 km and 6 km in the Philippine Sea. The data reported here examines the depth-dependence of the power spectrum, vertical coherence and directionality of rain and wind noise in the Philippine Sea. Acoustic estimates of rainfall rates and wind speeds are made from the surface to 5.5 km and 6 km respectively and compared to surface meteorological measurements. The depth-dependence of the accuracy of these estimates is relatively small and found to improve with depth. A coherence fitting procedure is employed to return ambient noise directionality and provide information on the spatial variability of an overhead rainstorm. With moderate 7-10 m/s winds, downward propagating noise from directly overhead dominates the noise field directionality from the surface to 6 km. Using the wind generated surface noise and the depth dependence of the spectral slope over the band 1 - 10 kHz, the frequency dependence of the absorption due to sea water is estimated and used to infer a mean water column value of pH.
Download or read book Sound Propagation in the Sea written by Robert J. Urick and published by . This book was released on 1979 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Modeshape Inversion Using Deep Water Ambient Noise Measurements written by Khalid A. AlMuhanna and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean acoustic tomography is a powerful method that uses sound to study ocean properties such as temperature, which is directly related to sound speed in water. This thesis focuses on using ambient noise to infer the normal modes of the ocean waveguide. The modes are a set of orthogonal functions that are solutions to the depth dependent wave equation, which depends on sound speed and thus on the temperature. Assuming that noise signals received by a vertical array consist of a sum of uncorrelated modes, the modeshapes can be determined from an eigenvector decomposition of the measured cross-spectral density matrix. Several authors have applied this technique to estimate the modes of shallow water waveguides, but there have been few opportunities to apply this technique in deep water waveguides. In this thesis the modeshapes of a deep water environment in the North Pacific are estimated using ambient noise data measured during the SPICE04 experiment. Although noise measurements were not the primary focus of SPICE04, the experiment provided a large data set for this analysis. In addition to acoustic measurements, the experiment also included extensive sampling of the environmental parameters. This thesis summarizes some of the noise statistics measured during 2004-2005. The measured modeshapes derived from the data are compared with the true modes derived from the measured environmental data.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1989 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelling the Vertical Coherence of the Shallow Water Ambient Noise Field written by and published by . This book was released on 1997 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a shallow water noise model used to simulate the vertical coherence of an acoustic noise field due to sea surface noise. The coherence between two vertically separated sensors is calculated from the Fourier transform of the received noise intensity as a function of vertical arrival angle. The vertical noise directionality is derived from a uniform distribution of sources at the ocean surface, an energy flux propagation model, and a plane-wave bottom reflection coefficient for a multi-layered elastic seabed. The propagation model allows for an arbitrary sound speed profile in the water column and includes attenuation by sea water. This model demonstrates the influence of noise source directivity, seabed parameters, and the sound speed profile on the vertical coherence of the noise field. Data/model comparisons are made with data collected on Western Bank, a shallow water area south of Nova Scotia, where the geo- acoustics of the seabed is well known.
Download or read book Springer Handbook of Acoustics written by Thomas Rossing and published by Springer Science & Business Media. This book was released on 2007-06-21 with total page 1179 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.
Download or read book A Survey of Models for the Prediction of Ambient Ocean Noise written by and published by . This book was released on 1996 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: The state of the art of model development for application to computer studies of undersea search systems utilizing acoustics is surveyed in this document. Due to the demands for surveillance of submarines operating in ocean basins, the development of noise models for application in deep oceans is fairly advanced and somewhat generic. This is due to the deep sound channel, discovered during World War II, which when present allows for long-range sound propagation with little or no interaction with the bottom. Exceptions to this channel, also well understood, are found in both the high latitudes where the sound is upward refracting and in tropical ocean areas with downward refracting sound transmission. The controlling parameter is the sound speed as a function of depth within the ocean, the sound speed profile. When independent of range, this profile may be converted to a noise-versus-depth profile with well-validated consequences for deep-ocean ambient noise. When considering ocean areas of shallow water, the littoral regions, the idea of a genenic ocean channel advisedly is abandoned. The locally unique nature of both the noise production mechanisms and of the channel carrying the sound, obviates the generic treatment. Nevertheless, idealizations of this case exist and promote the understanding if not the exact predictability of the statistics of shallow water ambient noise. Some examples of these models are given in this document.
Download or read book Underwater Acoustic Modeling written by P.C. Etter and published by CRC Press. This book was released on 1995-11-30 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: Underwater Acoustic Modeling provides the only comprehensive source on how to translate our physical understanding of sound in the sea into mathematical formulas solvable by computers.
Download or read book The Journal of the Acoustical Society of America written by Acoustical Society of America and published by . This book was released on 2006 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inverting for Geoacoustic Seabed Parameters Using Ambient Noise written by Nicholas Michael Carbone and published by . This book was released on 1996 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Hydrographic Journal written by and published by . This book was released on 2006 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
