This paper discusses a particular mechanism for energy loss in granular media, involving sticking and sliding between grains at areas of contact. Earlier publications have developed expressions for attenuation in regular packings of spheres, attributing all the loss to sliding friction. The present work extends the model by incorporating static friction and thereby derives an expression for attenuation which is in better agreement with measured values. The attenuation coefficient for both shear and compressional waves is found to be: 1. Independent of vibration amplitude at low amplitudes; 2. Directly proportional to frequency; 3. Dependent on the difference between static and sliding coefficients of friction; and 4. Dependent on the packing of the granules.
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Seismic Wave Propagation: Collected Works of J. E. White
This first chapter sets the stage for the later technical development of Dr. Whit’s career in applied seismics. Experiments, f’wst at the Acoustics Laboratory of the Massachusetts Institute of Technology and later at Mobil Oil and Marathon Oil, provided insight into the general problems of impedance measurements, transduction, filtering, and attenuation. These papers also serve as a bridge to show geophysicists how theft own experiments in seismology naturally interface with (indeed, arose out of) the larger world of sound measurements in air and water. These experiments demonstrate the power of geometrically constrained experiments to allow verification of approximate (and in some cases, exact) theories of sound.