The Loh Down On Science

Ultrasonic Eye

How to see inside a sealed metal container, without Superman.

It's a scientific trick worthy of Superman! This is Sandra Tsing Loh with The Loh Down on Science.

Say you have a sealed metal container – maybe an oil drum, or a tankful of toxic chemicals. You want to see what's going on inside. Without drilling holes, for obvious reasons.

But X-rays won't pass through metal. Neither will radio waves. What to do?

Henry Scarton, at Rensselaer Polytechnic Institute in New York, has the answer: an ultrasonic reflector that can change its own acoustical properties at will, switching between clear echoes and muffled ones.

So. Take your metal container. Insert a digital sensor. Attach Scarton's reflector. Seal.

Now fire up a one-megahertz audio transmitter.

Beeeep. Ultrasound goes in. The sensor outputs its data – as a stream of ones and zeros. The reflector converts that to a sequence of echoes: loud-soft-loud-soft. Outside, a receiver hears those echoes and decodes them back into the original sensor data.

Okay. It may not be as flashy as Superman. But you can always drape a red cape over it. Details.


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