New Technique "Sees" Tiny Vibrations in Bridges and Buildings

To the naked eye, buildings and bridges appear fixed in place, unmoved by forces like wind and rain. But these large structures do experience imperceptibly small vibrations that, depending on their frequency, may indicate instability or structural damage. MIT researchers have now developed a technique to 'see' vibrations that would otherwise be invisible to the naked eye, combining high-speed video with computer vision techniques. Normally, high-speed video wouldn't pick up such subtle vibrations from a building. To do this, 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 laboratory experiments, the researchers were able to detect tiny vibrations in a steel beam and a PVC pipe. The vibrations measured by the technique matched those picked up by accelerometers and laser vibrometry - precise but expensive techniques commonly used in infrastructure monitoring.