The Loh Down On Science

Bridge Sonics

Are bridges singin' in the rain?

This is Sandra Tsing Loh with the Loh Down on Science.

Talking not of Gene Kelly, but engineering professor Brian Mazzeo, of Brigham Young University.

See, bridge-repair engineers have long used a technique called “impact echo” to spot internal damage. They drag chains or ball bearings across a bridge, creating sound waves. Worn areas produce a duller sound.

But that method is expensive and can mean bridge closure for tests.

So one day, on a whim, Mazzeo dripped water onto a bridge slab. Turns out: Same acoustic effect!

To test the idea, Mazzeo and team pumped water onto a bridge. A microphone recorded the sound waves. Next they passed the recordings through software to spot patterns. Turns out water detects internal flaws as small as two centimeters. That’s the same accuracy as chain dragging, with less impact to the bridge!

Mazzeo said the concept might also work on aircraft, or anything subject to internal damage.

Meaning all other more invasive ways of testing are now water under the bridge. As opposed to over.

The Loh Down on Science is produced by LDOS Media Lab, with 89.3 KPCC Pasadena, California. And made possible by the generous support of the Gordon and Betty Moore Foundation.

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