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Bragg-Diffraction Imaging And It's Application For Non Destructive Testing

Though nature abounds with sonic detecting systems, men have been slow to recognize the potential use of acoustic energy as a means of visualization, that is, for "seeing" with sound. In the 18th Century a rather inventive Italian scientist named Spallanzani carried out a study of the remarkable ability possessed by bats for avoiding obstacles in the dark. (Ref. 1) He and his co-workers finally concluded that bats must have some unknown "sixth sense". One hundred years later the Frenchman Langevin proposed a sonic-echo system as a possible means of locating objects submerged in the sea, German U-boats in particular. Shortly after, Hartridge recognized and suggested a possible similarity between Langevin's system and the system used by bats (Ref. 2,3).