Download or read book In Situ Sediment Attenuation and Sound Velocity Ratio Measured in Shallow Water at the Quinault Range written by R. L. Allman and published by . This book was released on 1984 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Attenuation in Ocean Sediments Found in Shallow Water Regions written by Karl Crawford Focke and published by . This book was released on 1983 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: The acoustic attenuation in ocean sediments is a major loss mechanism for low frequency acoustic propagation in shallow water regions. Analysis of measured propagation in these regions has generally included estimates of the attenuation in the sediment, without consideration of the variations in attenuation as a function of depth. It will be shown that these variations can have a significant impact on the standard estimates. A new procedure is then developed which provides estimates of the attenuation as a function of depth. This procedure is used to obtain attenuation depth profiles in three shallow water regions. These estimated profiles present characteristics observed in laboratory and in situ measurements
Download or read book In Situ Determinations of the Velocities of Compressional and Shear Waves in Marine Sediments from a Research Submersible written by and published by . This book was released on 1969 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ measurements were made of the velocity and attenuation of compressional waves and of velocities of Stoneley waves (from which shear-wave velocities were computed) at six stations in the sea floor off San Diego, California. Water depths ranged from 20 to 1130 meters, and sediment types ranged from medium sand to clayey silt. Sediment densities, porosities, and grain sizes were measured in samples taken at each station. The unique data obtained allowed tentative evaluations of models and equations, and computation of constants, for elastic and viscoelastic saturated, porous media. (Author).
Download or read book Laboratory Measurements of Sound Speed and Attenuation of Water saturated Granular Sediments written by Theodore F. Argo and published by . This book was released on 2012 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt: The propagation of acoustic waves through water-saturated granular sediments has been widely studied, yet existing propagation models can not adequately predict the speed and attenuation of sound across the range of frequencies of interest in underwater acoustics, especially in loosely packed sediments that have been recently disturbed by storms or wave action. Advances in modeling are currently dependent on experimental validation of various components of existing models. To begin to address these deficiencies, three well-controlled laboratory experiments were performed in gravity-settled glass beads and reconstituted sand sediments. Sound speed and attenuation measurements in the 0.5 kHz to 10 kHz range are scarce in the literature, so a resonator method was used to investigate a reconstituted sand sediment in this range. The literature contains laboratory and in situ measurements of sound speed and attenuation at higher frequencies, but existing models can not predict both the speed of sound and attenuation simultaneously in some sediments. A time-of-flight technique was used to determine the speed of sound and attenuation in monodisperse water-saturated glass beads, binary glass bead mixtures, and reconstituted sediment samples in the frequency range 200 kHz to 900 kHz to investigate the effect of sediment inhomogeneity. The effect of porosity, independent of changes in other sediment physical properties, has not been demonstrated in the experimental literature. Therefore, a fluidized bed technique was used to independently vary the porosity of monodisperse glass bead samples from 0.37 to 0.43 and a Fourier phase technique was used to determine the speed and attenuation of sound. Collecting these results together, measured sound speeds showed positive dispersion below 50 kHz while negative dispersion was observed above 200 kHz for some samples. Attenuation measurements showed an approximately f0̇5 dependence in the low frequency regime and an approximately f3̇5 dependence for large-grained samples in the high frequency regime. The laboratory experiments presented in this work demonstrate that both sound speed and attenuation in idealized loosely packed water-saturated sediments can not be simultaneously predicted by existing models within the uncertainties of the model input parameters, but the independent effect of porosity on sound speed can be predicted.
Download or read book Arbeitsgruppe Gro m rkte im deutschen St dtetag Landeshauptstadt M nchen Internationale Gro markttagung M nchen 1955 written by and published by . This book was released on 1955 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Equipment for in Situ Measurement of Sediment Sound Velocity and Attenuation written by Richard L. Allman and published by . This book was released on 1974 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental system has been developed that makes possible the in situ collection of acoustic data in marine sediments, with greater convenience and accuracy than has been obtainable by laboratory analysis of bottom core samples. The feasibility of the system, operating in conjunction with the NUC Cable-Controlled Underwater Research Vehicle (CURV II), has been demonstrated. System capabilities are discussed.
Download or read book Measurements of Acoustic Backscatter of the Deep Sea Floor Using a Deeply Towed Vehicle written by M. Weydert and published by . This book was released on 1985 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1983 in area of Copper-Nickel rich manganese nodules at 14 deg 40 min N, 126 deg 25 min W (site 'E) was intensively studied with the Deep-Tow of the Scripps Institution of Oceanography, and 16 box cores were collected. Deep-Tow studies of the Thirtymile-Bank off the California Coast and the deep sea at the foot of the Patton Escarpment followed. The nodule coverage at site 'E varies from 0% to 80%. The nodule sizes vary between 1 and 13 cm. The nodule size distributions are best modeled by a Gaussian distribution. The three main nodule axes are related to each other at 1:0.8:0.5. The average density of individual nodules is 2.0 + or - 0.04 g/cu cm and the volumes increase on the average with the 2.8 power of the third root of the product of the three radii. Changes of the thickness of the upper acoustic unit of the sediment column correlate with changes in nodule coverage and concentration. The acoustic backscatter has been measured for frequencies of 4.5, 9, 15, 28, 60, 112 and 163 kHz and grazing angles from normal incidence to 5 degrees. The backscatter increases as the square of the frequency for sediments.
Download or read book In Situ Measurement of Sediment Sound Speed During Coring written by Donald J. Shirley and published by . This book was released on 1973 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A system was developed for attachment to sediment corers to obtain an in situ sound speed profile during a coring operation. The system uses two electroacoustic transducers mounted in the cutting head of the corer and associated electronic circuitry to measure the travel time of an acoustic pulse traversing the diameter of the sediment core. Laboratory and field tests which demonstrate the capabilities of the measurement technique are reported. Sound speed profiles were obtained in the Gulf of Mexico using a piston corer and in coastal waters using a special shallow water coring rig. Limited examination of the feasibility of measuring acoustic attenuation and volume scattering is also reported
Download or read book Acoustic Imaging of Shallow Water Sediments written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment volume inhomogeneity on the centimeter scale has a major impact on the design and application of high-frequency sonars, especially when operated in shallow water. An acoustic imaging system was developed to measure, image and model such inhomogeneities using acoustic tomography. The in-situ sediment acoustic imaging system consists of an array of needle-like probes that may be pressed into the sediment. Each probe is a line array of transducers. The current system consists of three identical probes attached to a sturdy frame. Each probe. contains 20 transducers, spaced 5 cm apart. Two probes are oriented vertically and pressed into the sediment about one meter apart. The third probe is oriented horizontally, just above the sea floor between the vertical probes. The transducers have a resonant frequency of 100 kHz and a bandwidth of approximately 40 kHz. The objective is to estimate travel time and transmit-to-receive amplitude on all possible raypaths. Two data sets were processed. Spreading of sound speed due to diffraction was observed, and attenuation coefficients (in mud) varied from 10 dB/m to 65 dB/m. The effects of gas bubbles and multiple scattering will require modeling. The advantages of the probe system are apparent: It can measure sound speed and attenuation coefficients and provide information to the marine geology and biology communities.
Download or read book SIO Reference written by and published by . This book was released on 1985 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sediment Sound Speed Measurements IN SITU from Bathyscaph Trieste written by E. L. Hamilton and published by . This book was released on 1963 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Use of the bathyscaph TRIESTE has permitted the first deep-water in situ measurements of the speed of sound in sea-floor sediments (other than seismic). Measurements were made at 3 stations off San Diego during August-October 1962, in water depths from 338 to 1235 meters, using specially designed probes which measured sound travel time over a 1 meter path 18 inches below the water-sediment interface at frequencies of 25 kc/sec.; probe accuracy was about + or - 0.5 m/sec. Three additional stations were made with the probes in sand bottoms by scuba diving in shallow water.
Download or read book Attenuation of Low Frequency Sound in the Sea written by and published by . This book was released on 1980 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Properties of Sediments written by Loyd Hampton and published by . This book was released on 1967 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustical Properties of Sediments written by and published by . This book was released on 1982 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work consisted of (1) final development of the ARL:UT profilometer recorder and transducer to enable the in situ measurement of compressional wave, shear wave, acoustic impedance, and static shear strength of ocean bottom sediments during geophysical coring, and (2) laboratory acoustical measurements on artificial sediments to test predictions of the Hovem model when the pore fluid viscosity is varied. The new profilometer recorder and transducer are described in detail as well as the microcomputer band playback system. Data obtained from the laboratory measurements are displayed.
Download or read book Measurement of Velocity and Attenuation Coefficient of Acoustic Waves in Marsh Water and Sediment written by Robert J. Minvielle and published by . This book was released on 2001 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean Seismo Acoustics written by T. Akal and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 898 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seafloor investigation has long been a feature of not only seismology but also of acoustics. Indeed it was acoustics that produced depth sounders, giving us the first capability of producing both global and local maps of the seafloor. Subsequently, better instrumentation and techniques led to a clearer, more quantitative picture of the seabed itself, which stimulated new hypotheses such as seafloor spreading through the availability of more reliable data on sediment thickness over ocean basins and other bottom features. Geologists and geophysicists have used both acoustic and seismic methods to study the seabed by considering the propagation of signals arising from both natural seismic events and man-made impulsive sources. Although significant advances have been made in instrumentation, such as long towed geophysical arrays, ai r guns and ocean bot tom seismometers, the pic ture of the seafloor is still far from complete. Underwater acoustics concerns itself today with the phenomena of propagation and noise at frequencies and ranges that require an understanding of acoustic interaction at both of its boundaries, the sea surface and seafloor, over depths ranging from tens to thousands of meters. Much of the earlier higher frequency (>1 kHz) work included the characterization of the seafloor in regimes of reflection coefficients which were empirically derived from surveys. The results of these studies met with only limited success, confined as they were to those areas where survey data existed and lacking a physical understanding of the processes of reflection and scattering.
Download or read book Sound Velocity Elasticity and Related Properties of Marine Sediments North Pacific written by Edwin Lee Hamilton and published by . This book was released on 1969 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
