Ron Vogel, sloth volunteer and resident physics expert, has the theory that the remarkable uniformity of the clay that the sloth bones are resting in provides a unique opportunity to use ultrasound technology to search underground.  If so it would save us a lot of time and money digging blindly for bones, and allow us to extend our search area significantly.   Preliminary results are back from the clay samples he collected at the site last month and the results are promising.

  According to Ron, “The results are. . . the same as I found in the tests on site. That is, the acoustic loss is about 5 to 10 times that of the human body. That seems like a lot but it is actually a lot less than anyone else has reported for soil. Based on these measurements, I’m working on a device we can use on site.”   He doesn’t know if he can get it done in time to do us any good but plans to try.

Ground-penetrating radar, which uses radio wave frequencies,  is generally used for remote underground sensing,  but it won’t work at the site under our conditions–the wet clay absorbs too much of the signal.  Ultrasound works similarly, but uses sound waves instead, and doesn’t suffer from the attentuation loss-problem under wet conditions. The technology runs into problems however with sorting out the meaning of the many different signal returns that result from trying it in  mixed materials.  For that reason ultrasound is  limited to looking inside relatively uniform materials– like concrete roadways and bridges (for corrosion), or steel railroad tracks (for signs of fatigue or cracks) and of course people (for babies).  More, as Ron moves ahead. . . .   Dave