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Acoustic testing to determine quality of dead and damaged timber

Finding a use for damaged timber after a wind event is key to recovering revenue and preparing the site for forest management. Declining timber quality - often determined by time or visual indicators - limits how much timber can be salvaged. Acoustics may provide better, field-based measurements to help managers find the right wood for the right markets.

Director’s Choice
Two sensors are attached to the sides of a fallen tree
A Fakopp acoustic device on a fallen tree at the Jones Center in Georgia. USDA Forest Service photo by Dana Mitchell.

A hurricane or other significant wind event produces significant timber damage, often as much as the typical annual harvest for the area affected. Afterward, the race is on to salvage as much timber as possible before moisture loss or decay reduces wood quality for common products like lumber, plywood, and pulp – and novel products like pellets and nanocellulose. Harvesters and mill supervisors use time since event or visual cues like checking, bark loss, or blue stain to determine if wood meets product specifications. Alternatively, acoustic devices measure the time of flight of a hammer strike impact to a receiver. Comparing the time of flight for storm-damaged wood to a reference piece might indicate wood quality or the presence of cracks or decay in the wood. Changes in the time of flight over time might indicate moisture loss or changes in wood properties. In field experiments, acoustic measurements were able to distinguish logs of different quality and identify loss of quality to decay.

Lumber manufacturing from storm damaged logs can also result in poor quality lumber with cracks and splits. Acoustic technology appears to be able locate internal fractures not obvious to visual inspection. Diverting damaged logs to the most appropriate markets is another way to improve returns from salvaged timber utilization.

Principal Investigator
Mathew Smidt, Research Forester/Engineer
RWU
4703 - Forest Operations
Publication
Field assessment of downed timber strength deterioration rate and wood quality using acoustic technologies
External Partners
Thomas Gallagher, Auburn University
Soledad Peresin, Auburn University
Brian Via, Auburn University
Dana Mitchell, US Department of Energy (formerly Southern Research Station)