Digital Dynamic Laser Speckle Photography (DDSP) has been applied to the visualization and measurement of an acoustic standing wave in water. The acoustic standing wave has been generated in a glass tube filled with salt water submerged in a rectangular tank with the same salt water matched in refractive index with the glass of the internal tube. Propagation of the sound wave through the water causes fluctuations in the refractive index which produce minute deflections of the collimated laser beam passing through the measurement volume. This results in a diffraction pattern modulated by the dynamic speckles at the far side of the measurement volume which is recorded using a high resolution digital CCD camera.
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