Fig. 3. Complex shock wave artifacts produced during display of simple geometric forms at different scanning velocities.

(A) Time-averaged wave patterns elicited via scanning stimulation of numerically simulated tissue along small square trajectories [normalized root mean square (RMS) oscillation velocity is shown]. Here, the shape dimensions (1 cm) are comparable in size to the wavelengths excited in the medium, yielding wave patterns that are smoothed and distorted, with substantial residual energy in central and peripheral regions at all scanning speeds. (B) Larger (3-cm) squares exhibited complex artifacts arising from constructive interference. At high speeds, global (v = 8 m/s) or local (v = 9, 10 m/s) maxima of the oscillation amplitude occur near discrete points interior to the scanning path.