POSSIBILITIES OF INCREASING THE DISTANCES AT WHICH GEOACOUSTIC METHODS ARE USEFUL IN FINDING NONHOMOGENEITIES IN ROCKS IN THE PRESENCE OF INTENSE NOISE,
Abstract
The possible methods of extending the distances at which acoustic methods are useful in determining the shape and location of inhomogeneities in rocks such as ore deposits are discussed. The main obstacle in increasing the distance at which acoustic methods are effective is the presence of noise. Measurements made in a mine in Krivoy Rog show that the industrial noise generated in the mine has a range of frequencies of 12-5 kc. The authors extract the useful signal from noise by storing the signal on a cathode-ray tube. The second type of noise is surface waves propagating along the mine faces surfaces. When highly sensitive electrodynamic receivers are used, the intense surface waves generate long-period free oscillations in the movable part of the receiver. In order not to decrease the sensitivity, the system is damped only during the initial period when the surface waves are registered and before the arrival of reflected waves. It is pointed out that the method of inverse probability is effective in determining the acoustic shadow in the presence of noise. Even the simplest approximation of the shape of the shadow makes it possible to determine the shadow's boundaries using just a few trial values for its width, and thus to obtain the shape of the ore deposit. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 09, 1968
- Accession Number
- AD0680991
Entities
People
- V. N. Mikhailovskii
- V. N. Pervushin
Organizations
- National Air and Space Intelligence Center