An acoustic wave train display form. A display mode of the acoustic wave train in the X-Z plane in which the intensity of the photographic beam is modulated with the amplitude of the wave form to produce a variable photographic density pattern as a function of time. All positive half-cycles appear as dark streaks, and all negative cycles which have been cut off appear as light streaks. See acoustic log and variable density. Compare amplitude-time or X-Y plane. See illustration at wave train display.