The Picus© Sonic Tomograph is an instrument for the detection of dysfunction, decay and cavities in standing trees.
Nails are driven through the bark, in a horizontal plane around the circumference of a tree and attached to sensors. The sensors measure time taken for sound waves to reach from one sensor to each of the other sensors.
A portable computer receives this information and displays a cross section of the trunk showing the variations in speed of the sound waves in different colours. The longer the wave takes to travel between sensors the more decayed or damaged the wood or more of an obstruction is present along that path.
A brown or buff colour indicates good quality wood with insignificant strength loss. Purple, Blue and white colours indicate progressively greater decay or dysfunction, leading to hollows at the white end of the spectrum. The green colours indicate wood of intermediate characteristics. Here there is likely to be some incipient decay, or the beginning of alterations to wood characteristics.Article written by Steve Cox on June 23, 2012