Folks:
Thanks for all the interest in wood-borne and ground-born sounds. My real=
purpose is to stimulate investigations in many areas of our curiosity, even=
as you all do for me every day.
But, I regret the tone of my brief note of yesterday. Still, it has been
my long experience on the internet that outrageous statements often flush
out facts much more quickly then polite queries do - a summary of five
years of answering BirdChat questions and then never getting any answer
whatever to those questions that I pose. I still apologize. Even making
the comparison between this group and BirdChat is, perhaps, invidious! My=
thanks especially to Rich for looking into the whole ideas and
implications, and to Jim for the referral to Rex Cocroft's work.
My interest in the 60's of sounds within trees was far more biological. If=
burrowing insects, such as the larger Buprestid and Cerambycid adults can
tunnel a cylindrical straight hole through healthy hardwood for 30 cm,
there MUST be some noises associated with this. I have heard and recorded
ID? beetles making loud noises audible from 20 ft from freshly cut White
Pine logs as they drop their powdery sawdust alongside the logs. The
families of Bostrichidae, Lyctidae and Anobiidae (death-watch) beetles are=
even more famous for gnawing audibly, or doing something that alerts
air-borne sound detectors like us.
It seemed to me that if we humans could hear their gnawing, some animal
predators (woodpeckers, for starters) might hear or sense the vibrations
as a location aid. So I was really listening for tunneling sounds, and
never heard even one. What I really wanted was to record some intermittant=
gnawing, then have a Downy Woodpecker land on the tree, and work its way up=
one side, and have the gnawing sounds stop for a while. That was my fantasy=
.
In the course of a year, I heard and recorded many other sounds I had not
even suspected: tiny birds landing fifty feet from the sensor; dogs walking=
across an exposed root thirty feet from the trunk; flying squirrels racing=
about on the bark, at a deafening level. This racing one night was suddenly=
interrupted by a Barred Owl hitting the bark with great force (a miss!),
followed by the squirrels (there were two on the tree at that point)
spiralling upward to swoop across the valley to another tree. Pretty
dramatic stuff, a lot at night. For ten years, every time I talked to a
bioacoustics friend (Roger, Katey Payne, Chris Clarke, etc.) I tried to get=
them interested in taking on this simple project, or at least to sic a
clueless grad student on it. No takers. Everyone wanted me to do it, and=
I didn't.
RE Thorn-bugs love songs - I am not sure where the leg-pulling begins and
ends, here, WRT Rex and his one-of-a-kind rumbling ten foot bugs. So I'll=
leave it alone for a while. (Sorry, Lang, for misspelling your
name!). Love calling was one aspect that I didn't expect to be lucky
enough to stumble onto.
I have wondered for three decades whether the silence from gnawing heard
day and night was:
1. because I didn't have the sensors on the right trees - maybe only the
ones I listened to were gnaw-free.
2. because the gnawing beetles do so very, very quietly; perhaps the
evolution of sound makers and their sound-chasing predators has evolved to=
a point of mostly silence; or maybe they are so well protected in the
wooden tunnels they could (evolutionarily) care less; or
3. because (you name it).
My wife and I did put a chart recorder on one tree at a neighbor's place,
one with a flying squirrel feeder on it, and found out
a lot about nocturnal feeder-related Glaucomys behavior.
I will tell you one low-tech fact that emerged. The sound velocity in
solid northern hardwoods, such as oak, hickory, ash and maple varies with
direction: radially, longitudinally and tangentially, and that the velocity=
in brass is right within that range. This means (historical music
instrument and furniture fans) that brass screws holding thin wood together=
will not make reflections or refraction nodes, of themselves. No sudden
impedance shifts. Very interesting. Now a joint itself, another question,=
as is the velocity in horse-hide glue (?). Instrument makers have
long-known one fact that my xylophonics confirmed: for the lossless
movement of vibrations, wood is nearly as coherent a material as you might=
find.
my very best,
Marty Michener
MIST Software Associates
75 Hannah Drive, Hollis, NH 03049
coming soon : EnjoyBirds bird identification software.
________________________________________________________________________
________________________________________________________________________
|