Systems on the edge of failure sound funny. Ask the mechanic listening for the death-rattle of a dying U-joint or the doctor thumping a patient’s back.

And then there’s the deadly “click” of laminated surfaces coming unglued. Civil engineers have long used acoustic tests to find places where bridge and highway decks are delaminating, getting ready to flake off and fall away from their under layers. These test methods have been relatively slow, though, relying on carefully placed hammer blows, dropping steel ball bearings, or dragging heavy chains. The testers crawl down the road thump by painstaking thump at a top speed of less than two miles per hour.

Researchers at electronics and civil engineering departments of Brigham Young University have developed an elegantly simplified method for pounding the pavement, using the percussion of water droplets to find the weak spots. [read more..]