Dear Julian,
I am one of the people, giving the PICUS demonstration in California.
Some more information on the faulty reading there:
If a wave - in our case sound wave - travels though a material it is
influenced by the material. The travel speed of the wave depends on the
material. The wave travels faster in sound wood than in decayed wood and
so on.
If the wave travels from one material to another it (overcoming borders)
it looses a part of its amplitude. This loss of amplitude (or power)
seems (!) to slow down the speed.
On the tree in California the sound was generated in the bark (not onto
the latest grows ring). Therefore, it had to overcome two borders:
entering the wood first, travelling through the wood, leaving the wood
and entering the bark on the other side.
This loss of amplitude caused the system to assume that the speed of
sound in the outer area of the trunk is higher than in the inner area.
The PICUS sonic Tomograph detects and shows differences in the ability
of the wood to transmit sound waves. Therefore, the inner area was show
in blue/red colours, the outer in brown. We actually measured more or
less the thickness of the bark. (A good result from this point of view
... )
Usually you feel quit exactly when the nail reaches the solid wood - so
don't worry about this to much. A mistake like this happens only once to
you.
I learned the following: never knock on unknown species in public.
Especially not - if the tree is on the other side of the world.
Get some information about the species first. Ask local tree experts and
so on.
If you have further question, please do not hesitate to ask! Mail to the
newsgroup or directly to lothar.goecke@xxxxxxxxxxxxxxxxx.de
With kind regards
Lothar Göcke
argus electronic gmbh
Joachim-Jungius-Str. 9
18059 Rostock
Germany
Tel.: +49 / 381 - 40 59 815
Fax : +49 / 381 - 40 59 322
lothar.goecke@xxxxxxxxxxxxxxxxx.de
www.argus-electronic.de
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