Brain Food: Sound Wave Technology Measures Tree Quality For Market Value

May 5, 2016

If a tree falls in the forest and no one's there to hear, does it make a sound? It definitely makes sound waves, according to wood scientist Dave Auty of Northern Arizona University. Auty uses "acoustic evaluation technology", or sound wave probes, to determine the stiffness and quality of a tree before it's harvested. It's a technique new to northern Arizona forests.

NAU wood scientist Dave Auty uses "acoustic evaluation technology", or sound waves, to determine density of trees before they're harvested
Credit KNAU/Bonnie Stevens

Auty says the idea is to send a pulse of sound through the tree to measure the time of flight of the acoustic wave. Simply put, the faster the sound, the stronger the wood. 

"For instance, the rolling velocity of this tree is 2.7 kilometers per second", Auty says. "That's quite low. so this tells me this tree isn't very stiff. It will not produce lumber that's really suitable for high-end structural uses."

This information helps those in the lumber industry determine the value of a stand and whether it will be turned into particle board, wood ships or higher-end building materials. Auty says acoustic technology can add value by making the process more efficient.

"These acoustic tools," he says, "give us the ability to make some intelligent decisions about what we're going to do with a stand of trees when we cut it."

Auty believes sound wave technology will be an important tool as forest restoration projects increase and more wood fiber is removed from forests. 

Brain Food is produced by KNAU, Arizona Public Radio.