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Author: J. G. Hanse Publisher: ISBN: Category : Sea ice Languages : en Pages : 42
Book Description
The attenuation of an acoustic disturbance propagating in a medium which is not perfectly elastic, homogeneous and isotropic can be considered to be the result of energy dissipation due to classical processes and scattering. The contribution of each of these mechanisms is dependent upon the frequency of the sound wave. In this report several mathematical models are discussed for a transverse wave moving in a visco-elastic material and a scattering theory is developed. The theory is applied to sea ice and attenuation as a function of frequency is predicted for this material. (Author).
Author: J. G. Hanse Publisher: ISBN: Category : Sea ice Languages : en Pages : 42
Book Description
The attenuation of an acoustic disturbance propagating in a medium which is not perfectly elastic, homogeneous and isotropic can be considered to be the result of energy dissipation due to classical processes and scattering. The contribution of each of these mechanisms is dependent upon the frequency of the sound wave. In this report several mathematical models are discussed for a transverse wave moving in a visco-elastic material and a scattering theory is developed. The theory is applied to sea ice and attenuation as a function of frequency is predicted for this material. (Author).
Author: Publisher: ISBN: Category : Languages : en Pages : 88
Book Description
The principal objective of this investigation was to experimentally determine the feasibility of using acoustic pulse echo techniques to measure the thickness of sea ice. Field tests performed on both winter and annual sea ice showed that a pulse echo technique is entirely feasible if: (1) adequate coupling between the sound source and the ice surface is obtained, and (2) either the source levels are kept sufficiently high or the frequency is kept low enough that the wavelength of the sound is large compared to the size of the sound-scattering centers in the ice. Our measurements of the compressional and shear wave velocities parallel to the axis of the ice indicate that such thickness measurements can be accurate to within 1.5%. The tests indicated that the acoustic impedance mismatch at the ice water interface is sufficient to allow the use of either the compressional or the shear wave. Before the shear wave could be used, however, an efficient method would have to be found for establishing a reliable bond between the ice and the acoustic source. We did not obtain sufficient data to verify reports in the literature that seasonal variations in both the compressional and shear wave velocities approach 20%.
Author: Paul J. Vidman Publisher: ISBN: Category : Ice Languages : en Pages : 74
Book Description
The goal of this research has been to determine the fundamental acoustical properties of sea ice. Our major accomplishment was measuring the temperature dependence, depth dependence, and anistropy of the propagation velocity of ultrasonic compressional wave pulses in sea ice cores. Additional work was done to examine methods for in situ measurement of compressional and shear wave velocity and attenuation of Arctic ice. Keywords: Compressional velocity; Penetrator; Ultrasonic properties; Anistropy.
Author: Michael I. Taroudakis Publisher: Springer Science & Business Media ISBN: 1475735200 Category : Science Languages : en Pages : 221
Book Description
This volume provides recent and useful results for bottom recognition, inverse scattering in acoustic wave guides and ocean acoustic tomography, plus a discussion of some of the new algorithms, such as those related to matched-field processing, which have recently been used for inverting experimental data.
Author: George P. Vance Publisher: ISBN: Category : Sea ice Languages : en Pages : 160
Book Description
Because of the lack of success in measuring sea ice thickness with normal acoustic means, a method utilizing shear waves or 'S' waves was tried during the summer of 1971 off Point Barrow, Alaska. A 551A*Textronic oscilloscope and polaroid camera were used to record the signals received. Two Columbia High Capacity accelerometers were used for triggering the scope and obtaining the return signal. A three pound sledge-hammer impacting on a six inch diameter steel plate was used as the 'S' wave source. Results were obtained in ice thicknesses from 7.0 feet to 21.0 feet thick. An average 'S' wave speed in sea ice of 6.56 feet per millisec was used. In comparing the recorded signals with physically measured thicknesses, the average error was found to be 6.6%. (Author).
Author: James H. Getman Publisher: ISBN: Category : Sea ice Languages : en Pages : 209
Book Description
An experimental apparatus for the measurement of the thickness of sea-ice by the use of a shear wave reflection technique was designed and constructed. The apparatus was tested extensively in the Arctic during the summer of 1972. A portion of the apparatus, the horizontal impact source, produced reliable and repeatable excitation of the ice. Unfortunately, the measurement of the thickness of sea ice by the use of a shear wave reflection technique was not as simple as was anticipated, primarily due to the difficulty of properly exciting the ice and to the mode conversion of the acoustic energy by external and internal features of the ice.
Author: J. G. Hanse
Author: J. G. Hanse
Author: 
Author: 
Author: Paul J. Vidman
Author: 
Author: J. G. Hanse
Author: Michael I. Taroudakis
Author: George P. Vance
Author: James H. Getman
Author: Mustafa Akbaraly Vahanvaty