Wave‐front dislocations in the soundfield of a pulsed circular piston radiator

Wave‐front dislocations are lines in space along which wave fronts end, named by analogy with dislocations in imperfect crystals. Continuous waves and quasimonochromatic pulses (of continuous waves with slowly varying envelopes) are conveniently represented by complex‐valued wavefunctions, the zeros of which correspond to wave‐front dislocations. Pulse dislocations move through the wavefield, and may interact, as the pulse propagates. As examples of realistic model wavefields, the soundfields of a rigid circular piston radiator vibrating in a fixed rigid baffle plane, driven both by a sinusoidal source producing continuous waves and by this source modulated by a Gaussian envelope, are computed exactly and displayed. The birth of dislocations in the nearfield and their propagation with the pulse into the farfield are observed and discussed, and birth and death events in the nearfield are displayed in detail. The behavior of quasimonochromatic pulses and their dislocations may be understood in terms of the carrier wavefield, both qualitatively and, via a perturbation theory, quantitatively.