To the naked eye, buildings and bridges appear fixed in place, unmoved by forces like wind and rain. But in fact, these large structures do experience imperceptibly small vibrations that, depending on their frequency, may indicate instability or structural damage. MIT researchers have developed a technique to “see” vibrations that would otherwise be invisible to the naked eye, combining high-speed video with computer vision techniques.

Motion magnification of a crane imperceptibly swaying in the wind. The source video is on the left; the motion magnified video on the right. (MIT)

The researchers employed a computer vision technique called motion magnification to break down high-speed frames into certain frequencies, essentially exaggerating tiny, subpixel motions. In lab experiments, they were able to detect tiny vibrations in a steel beam and a PVC pipe. The vibrations matched those picked up by accelerometers and laser vibrometry. Motion magnification provides a faster, cheaper, and noninvasive alternative to these monitoring techniques.