To the naked eye, buildings and bridges appear fixed in place, unmoved by forces like wind and rain.<\/p>\n
But in fact, these large structures do experience imperceptibly small vibrations that, depending on their frequency, may indicate instability or structural damage.<\/p>\n
MIT researchers have now developed a technique to \u201csee\u201d vibrations that would otherwise be invisible to the naked eye, combining high-speed video with computer vision techniques.<\/p>\n
Normally, high-speed video wouldn\u2019t pick up such subtle vibrations from a building.<\/p>\n
To do this, the researchers employed a computer vision technique called \u201cmotion magnification\u201d to break down high-speed frames into certain frequencies, essentially exaggerating tiny, subpixel motions.<\/p>\n
In laboratory experiments, the researchers were able to detect tiny vibrations in a steel beam and a PVC pipe.<\/p>\n
The vibrations measured by the technique matched those picked up by accelerometers and laser vibrometry \u2014 precise but expensive techniques commonly used in infrastructure monitoring.<\/p>\n
Oral Buyukozturk, a professor of civil and environmental engineering at MIT, says motion magnification provides a faster, cheaper, and noninvasive alternative to existing monitoring techniques.<\/p>\n
\u201cThis could be a noncontact sensor technology that can be used for economic and speedy applications,\u201d Buyukozturk says.<\/p>\n
\u201cDepending on your objective, perhaps you could use the camera on your cellphone for screening, and if you detect something, you could concentrate on it with a high-power camera. There are levels of inspection, and you don\u2019t always have to start with the highest-quality camera.\u201d<\/p>\n
Buyukozturk has co-authored a paper, along with lead author and graduate student Justin Chen, which appears in the Journal of Sound and Vibration. <\/em><\/p>\n The paper\u2019s other co-authors are graduate student Neal Wadhwa and postdoc Young-Jin Cha, along with professors of computer science and engineering Fredo Durand and William Freeman.<\/p>\n