Have you ever considered fishing?

[mas]

One might think that this may indicate a need for a break from acoustics...or maybe a new hobby entirely!

From Echoes, the Newsletter of the Acoustical Society of America,

Volume 11, Number 3, Summer 2001

Global Infrasonic
Monitoring of Large Meteoroids

by Douglas O. ReVelle

Networks of
low-frequency acoustic detectors, originally

built for other
purposes, are now finding a new

and unexpected use in
detecting objects that enter

our atmosphere. The
orbit of Earth through the solar system

passes through much
solid particle debris, including pieces of

material from both
comets and asteroids. We call these arriving

particles meteoroids.
The asteroidal and cometary

sources have a wide
variety of properties, so meteoroids can

arrive from very
different orbits and belong to one of several

types of observed
materials. They can be iron, rocky stones,

very weak stones
(Carbonaceous chondrites) or there are two

brands of very weak
cometary material as well. This debris

can be either very small
or very large or have a large range of

possible sizes,
depending on the source and how long the

material has been
orbiting in space free from its source and

other factors. This
material can also have a large range of possible

entry speeds and
densities.

As Earth moves about the
Sun, it acts as a tiny dust mop

sweeping up this
material which can strongly interact with

the atmosphere at very
great heights (above 60 miles). On

occasion these larger
and brighter meteors and fireballs or

bolides (the name of the
atmospheric phenomena) travel at

high speeds to collide
with Earths surface and possibly even

produce an extensive
crater. This delivery of meteorite samples

(the ponderable pieces
that reach the Earth intact), originating

on other worlds beyond
our own, provides a means of

studying our own origins
as well.

The interaction of these
meteoroids with the atmosphere is

very strong partly due
to the very high speed at entry and partly

due to the
compressibility of the atmosphere. The entry speed

compared to the speed at
which sound waves travel, called the

Mach number, typically
can range from 50300. For comparison,

a typical Mach number of
a commercial or military

supersonic jet is less
than 3. As a direct consequence of this

high speed, an explosion
is generated along a cylindrical path

about the entry
trajectory. This deposition of energy along the

path constitutes an
explosion whose characteristic scale is

called the blast wave
radius, which delineates the size of the

region in which an
explosion has occurred. For large meteoroids

capable of penetrating
the atmosphere down to heights

where a shock wave is
formed, this scale can range from a

minimum of 10 meters (in
order to be recorded at ground level)

to many kilometers in
length. For comparison, the typical size

scale of the sound
source in ordinary thunder is about 2 or 3 m.

Sounds that emanate from
such sources in the atmosphere

can have very large
amplitudes, even great enough to break

glass windows at close
range. Frequencies of such sources

can be low enough so
that the peak energy is below the range

of audible sound waves,
which we call infrasound. As the

blast wave radius
increases we find that these frequencies become

progressively lower. For
the famous Siberian meteorite

explosion (Tunguska) of 1908, ultra-low sound frequencies

of 1/60 Hertz
(corresponding to a period of about 1 minute)

were observed at great
distances from the entry trajectory. As

these signals propagate through
the atmosphere, the ambient

temperature and winds
aloft can bend the signals away from

straight-line paths,
i.e., refraction. They can also be diffracted

and scattered as well
since this is a wave phenomenon. We

now know empirically how
to relate the period at maximum

amplitude of the sound
waves to the source energy. For the

blast wave radius values
quoted above, source energies range

from ~0.00001 kt (1/100
of a ton of TNT) to 10 Mt (megaton)

of TNT equivalent (1 kt
= 4.186×1012 Joules). For comparison,

the nuclear weapons
dropped in Japan
in WWII produced

explosions of about 15
kt.

Over the past few years
we have observed a number of

these very large bolides
over a very large energy range. From

these data we have been
able to locate the sources and calculate

the frequency of
occurrence of these large bodies at the

Earth in a year. The
observations at arrays of sensors on the

ground using low
frequency microphones, separated horizontally

by distances of a few
hundred meters to a few km

typically,
can be used to determine both the angular great circle

distance of the arrival as well as the elevation angle of the

signals. This allows us to uniquely locate these sources in three dimensional

space within the atmosphere within certain errors.

For example at a range of 3350 km, a bolide of about 0.2

kt was readily recorded infrasonically even as long ago as 1965.

Also, from such data we can estimate that the frequency of

occurrence of rocky type meteoroids for a energy of 15 kt is

about
once per year over the globe. At the energy of Tunguska

(10 Mt), it is about once every 120 years and this event last

occurred about 93 years ago. Corresponding to an energy of

0.1 kt for example, we find a value and associated uncertainty

of about 30 ± 9 large bolides/year and this value continues to

increase as the source energy decreases and vice versa.

[mungkiman]

It's interesting that the Inuit fashioned their metal tools from iron meteorites.

[Speedball]

Why yes, I have considered fishing and it is one of those hobbies I gave up then discovered Audio. I still have my fishing poles and very large tacklebox just full of lures that someone will consider a gold mine one day.

[merkin]

I heard you can either fish or golf. I went to the dark side and I golf. There is not enough time in life for both.

Well you can do both but not well. I have a feather lite ugly stick and a box full of lures just drying out. There is always a thrill when the pole gives you those quick tugs and wondering what is going to show when you real it in.

[thebes]

If a meteorite is about to hit earth we, The Klipsch Defense League will be mobilized. Massive arrays of Khorns, Belles and Cornwalls organized under the direction of Generalissimo Thebes will be aimed at the approaching object. Powered by only 3 watts of very clean amplifier power the resulting sound wave will vaporize said meteor.

After receiving the accolades of a greatful planet, Generalissimo Thebes will go:

[mikebse2a3]

If a meteorite is about to hit earth we, The Klipsch Defense League will be mobilized. Massive arrays of Khorns, Belles and Cornwalls organized under the direction of Generalissimo Thebes will be aimed at the approaching object. Powered by only 3 watts of very clean amplifier power the resulting sound wave will vaporize said meteor.

--------------------------------------------------------------------

Hey General Thebes!

Don't forget the latest weapons at your disposal!

The KPT-KHJ-LF (code name JUBILEE) with the K402/K69A

I believe Coytee will be able to blast most comets (heck he's probably just waiting for the chance)[6] but just in case he's not listening just give me the code no. and I'll crank mine up for you!!!

mike tn[]

[thebes]

The Generalissimo is well aware of the available weapons platforms produced by Klipsch Armorments Ltd.

The Jubs, of course, are being held in reserve in case those pesky Martians come back for another try at us.

Stand at the ready my good man, your day will come.

[bodcaw boy]

everyday.....

have a blessed day,

roy delgado

[bodcaw boy]

Why yes, I have considered fishing and it is one of those hobbies I gave up then discovered Audio. I still have my fishing poles and very large tacklebox just full of lures that someone will consider a gold mine one day.

i have on more than one occasion, consider giving up audio for fishing. designing lures in 3D and then trying out the lure, research of course, sounds very tempting......

have a blessed day,

roy delgado

[bodcaw boy]

It's interesting that the Inuit fashioned their metal tools from iron meteorites.

yeah.......the cheaters........

have a blessed day,

roy delgado

[T2K]

.

[mas]

T2K, if I may ask (and since your profile indicates that you are in the south!), where did you take those nice stripe?

That looks like a nice haul out of Tim's Ford Lake near Tullahoma, TN.

And Roy, you have been so kind to provide many answers regarding the horns, are you as amenable to sharing just where you are finding those nice bass that you have been posting?

And here's a question that I would sure appreciate an answer if anyone is aware of one!

For a nice change from the ultra- and medium light setups, I sure wish I could find a nice heavy action with a fast tip 6.5-7' SPINNING rod (but not a surf rod! I already have access to rebar) that would cover the same range that is so common with the bait casting rigs. Between moving from bass to stripe and dealing with lakes where between the wind and the depth, setups such as Carolina rigs start out with 1- 1.25 oz weights (ouch!) just to get the lure out of the boat into the wind (and to not have it blown back into the boat!) and down to the required depths within our lifetime - results in a MH rod that is already loaded and sprung before a fish gets near it!

Falcon used to make one in the early-mid 90's, but now it seems all the folks I know doing this in TN/AL and Texas are paying to have one made as they can't find one (and I just cannot justify spending $3-400 for one! I need that money for one pair of my ultra-exotic audio interconnects! ;-). I know they are a dime a dozen for bait casting, but the days of spinning 'only being appropriate for lightweight rigs' is long gone. Gee, I make life complicated! ;-)

[PhilMays]

Only every day!

[RFP]

Well, not every day, but as often as I can... Here's a nice little native cutt, taken on a Mike Clark bamboo rod last year on Yellowstone's Slough Creek third meadow... There were lots more where he came from... and, by the way, as far as I know they are still there (!)... I put 'em all back

[T2K]

Those stripe were caught in north central Alabama at Lewis Smith Lake mas. The stripe are stocked by G&F and there are plenty of them swimming around the depths. The lake is large and deep (google Lewis Smith), 300 feet deep in many places. The record spotted bass was caught there many years ago, and there have been a few reports of smallmouth caught over the years. The lake can be hard to fish because of the size/depth/clarity.

The two in the picture were two of many we caught in the 12 pound range that particular day. I caught a 23 pounder another trip and we lost several more that either broke off or got hung up in standing timber. I haven't kept up with the stripe there in a few years but they run over 40 pounds there now. I used flipping sticks with Ambassaduer baitcasters, 6500C's. Regular bassin' gear will suffice with 12-14 pound test line and light drag as these jokers pretty much go where they want to.

I've used hair jigs to shad/balloons to topwater. Knowing where to find them is the secret, as is usual when fishing.

I guess you've checked out Bass Pro Shops catalog for a rod, huh?

Keith

[mungkiman]

Pacific Ocean, Oregon Coast.

[Champagne taste beer budget]

And here's a question that I would sure appreciate an answer if anyone is aware of one!

For a nice change from the ultra- and medium light setups, I sure wish I could find a nice heavy action with a fast tip 6.5-7' SPINNING rod (but not a surf rod! I already have access to rebar) that would cover the same range that is so common with the bait casting rigs. Between moving from bass to stripe and dealing with lakes where between the wind and the depth, setups such as Carolina rigs start out with 1- 1.25 oz weights (ouch!) just to get the lure out of the boat into the wind (and to not have it blown back into the boat!) and down to the required depths within our lifetime - results in a MH rod that is already loaded and sprung before a fish gets near it!

Falcon used to make one in the early-mid 90's, but now it seems all the folks I know doing this in TN/AL and Texas are paying to have one made as they can't find one (and I just cannot justify spending $3-400 for one! I need that money for one pair of my ultra-exotic audio interconnects! ;-). I know they are a dime a dozen for bait casting, but the days of spinning 'only being appropriate for lightweight rigs' is long gone. Gee, I make life complicated! ;-)

I consider fishing pretty much every day, in fact spent a good part of this past weekend sorting plastics and stripping line off reels. Not looking forward to buying new line, but a necessary evil. A 1500' spool of 80lb Power Pro is $145 at Bass Pro. [:S]

Are you familiar with St Croix rods? I'd think their PS70XHF would fit the bill. I have a bunch of their rods and like them, they also have a very good warranty.

Look around their website, they have different levels of rods at different price points, sure to be something you like, or else check around for a good rodbuilder that can help you with blank selection. I'd think you could get a dang nice rod made for 2-250 if you didn't go crazy on the wrap job.

http://www.stcroixrods.com/rods/default2.asp?rodname=36&section=spin

Good Luck and Tight Lines.