At 01:01 AM 12/9/2006, you wrote:
>Hello!
>I want to record the sound of Red Palm weevil. The larvae infest the trunk=
>of date palm. They feed inside the trunk and produce a feeble sound that
>can not be heard from outside.
>There is some costly equipment to record it. www.laartech.biz
>I would like to know if there is some other way to record these feeble
>signals.
>
>Hope to receive some reply from the members.
>
>Thanks.
>
>Dr. Abdul Rauf
>Entomologist
Dear Dr. Rauf:
An old phonograph cartridge is the weapon of choice in recording tiny
vibrations in trees. I used them to do just that in the 1960's and I hope
you can find them inexpensively still. The cartridge needs to be mounted on=
a small metal weight and the two then suspended by some foam from actually=
touching the tree. The sound is conveyed from the dense inner tree wood to=
the cartridge by a BRASS screw of suitable thickness and length (the
velocity of sound in brass almost exactly matches that in many hard woods,=
and so produces no loss from a shift in elastic impedance).
I mount the 3 inch by 6 inch sheet of copper on the tree with a rubber
inner tube sandwiched between, as a sound deadener and three screws through=
both into the tree.
On the copper piece, I glue some foam, then glue the cartridge and metal
mount onto the foam, so it is supported by, but cannot receive much
vibration from, the tree or copper sheet.
Under the place where the needle would be, there is a pre-drilled 1/2 inch=
hole in the copper (but not the inner tube), and the brass screw I
mentioned, going well beyond what bark there is (or leaf petiole bases in
the case of a palm) into the hard inner woody material. It is essential
that the head of the cartridge rests securely on the top of the brass
screw-- you will have to experiment with foam and glue and rubberbands,
perhaps, to ensure a good sound contact.
I mounted over the copper base a heavy copper box 5 3/4 x 2 3/4 inches,
which I made from some 3 inch copper plumbing pipe, sawed in half
lengthwise, put over the copper base and the cartridge. The box is held
over the copper base and to the tree by several strips of inner tube
passing left to right over it, with each end of the strip screwed to the
tree on the sides.
Any vibrations made by an insect --- or a person walking over the root
system even-- are carried by the wood to the brass screw, out through the
rubber inner tube and the 1/2 hole in the copper case, directly to the
needle, and produce loud signal from the cartridge.
Regarding the signal. I found that the output from piezoelectric cartridges=
is very high impedance -- all volts, no amps -- so you cannot just run a
line from the tree indoors, plug it into a recorder and hear anything but
static and hum. I made a two-transistor emitter follower preamp with a
voltage gain of one but it reduces the impedance to a few hundred ohms,
just what you need to run a line for many feet with no noise problems. You=
still do not need batteries or twin conductor line, as the power source and=
load resistor are in office, with a few milleamps flowing out and back to
drive the preamp.
I called the study I made: "Xylophonics" -- sound from wood -- it was so
sensitive, on a 70 ft high Red Oak tree, Quercus rubra, that a 12 gram
Black-Capped Chickadee (a small bird) landing on the top-most branch
sounded like an ironing board dropping on a wood floor : THUNK!! Squirrels=
running up the tree sounded equally loud. You could clearly hear people
walking on the ground thirty feet from the oak trunk. Rain on the tree was=
very loud, as was wind clatter of branches. I didn't, however, hear any Red=
Palm Weevils, or Buprestids or Cerambycids, which is what I was hoping for.=
I expect that wind among the huge palm leaves may be a problem for you.
The box turned out to be quite weather-proof, and lasted many months
through a New England winter. We were listening to about 10 flying
squirrels running about on the tree one night, when suddenly there was a
terrific "thunk" and the squirrel noise immediately increased greatly and
then suddenly stopped. A barred owl had evidently just missed one squirrel,=
hitting the tree about 30 ft up, and the squirrels spiralled around the
tree upward and out the uppermost branches then launched into space,
gliding to the safety of the other nearby forest trees.
-- best regards, Marty Michener
MIST Software Assoc. Inc., P. O. Box 269, Hollis, NH 03049
http://www.enjoybirds.com/
PS If you have any digital photos of Phoenix dactylifera you might be
willing to let me use as illustrations in my nearly-done book on plants, I=
would appreciate your emailing them to me, along with the photo credit you=
would like to appear below the photo. The book covers common plants of New=
England - or plant parts we often eat or use, so dates are clearly fair
game, as are bananas, sugar-cane and coconuts and many spices.
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