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Curly Birch

February 26, 2007

Ultrasound could help tell expensive wood from cheap.


The physics of forestry. I’m Bob Hirshon and this is Science Update.

Curly birch is a rare natural mutation of the silver birch tree, and is valued for its wavy grain. It costs ten times as much as its non-curly counterpart, which is used for pulp. Now, scientists in Finland, where silver birch is grown, have found a way to accurately tell the difference between the two when they’re young. That could help foresters decide which trees to cull and which to keep. Physicist Ari Salmi of the University of Helsinki says the technique uses high-frequency sound waves called ultrasound.

ARI SALMI (University of Helsinki, Finland):
We launched ultrasonic waves into the wood and studied the time of flight through the sample. And from this time of flight we determine if it’s curly or not.

He says the sound waves go faster through the harder curly birch. Their preliminary results show the method is 93 percent accurate.

I’m Bob Hirshon, for AAAS, the science society.