James R. Brewster
Natl. Ctr. for Physical Acoust., Dept. of Phys., Univ. of Mississippi, University, MS 38677
Wave field dislocations, so named because of their morphological similarity to dislocations in crystals, are singular lines in the phase of a wave. It will be demonstrated that they can be applied to the characterization of sound fields that exhibit a complicated spatial variation. Dislocations have been identified experimentally in wave fields formed by the scattering of pulsed ultrasound from rough surfaces and from the internal microstructure of metals. The statistics of these dislocations can be correlated with the length scale of the features responsible for the scattering. Experiments were performed using pulsed ultrasound, of central frequency 20 MHz, reflected from the specimen and detected in water immersion using a coincident source--receiver. The phase of the wave is defined in terms of the position of the wave crests in the signal detected as a function of time at a fixed receiver position.