Experimental observation of acousto-optic moiré phenomena is reported. The experiment employs optical phase gratings generated by high-frequency (0.5–2 MHz) acoustic tonebursts propagating in a transparent water tank. Two or more superposed gratings are observed by means of an optical, stroboscopic, scanning schlieren imaging system. Still and motion picture photographs of acoustic tonebursts and of moiré patterns associated with superposed tonebursts are presented and analyzed. Additive and subtractive moiré patterns are distinguished. It is shown that the subtractive moiré patterns propagate at speeds higher than that of the individual acoustic tonebursts, while the additive moiré patterns do not propagate. A moiré method of quantitative schlieren phase measurement of complicated acoustic fields is introduced, and an application to the visualization and analysis of scattering by underwater targets is indicated.