|
Theoretically that is correct but the Man in a
previous email said he was able to hear the rock concert audio 20 Kilometres
away and that was scattered audio.
He was able to hear the total audio spectrum and
depending on the individual hearing spectrum could be 0 - 15 Kcs.
Perhaps the distance was even greater. You are
saying Megawatts audio would fizzle out a couple of Kilometres away, which is
not true. I have heard public address system several miles away also I remember
the old sirens years ago when they were used for emergency alerts, these could
be heard tens of miles away maybe 20 - 30 miles and were not
Megawatts.
g3kev
----- Original Message -----
Sent: Wednesday, September 01, 2010 5:40
PM
Subject: Re: LF: VLF THOUGHT
Mal,
You seem to be intent on ignoring the basic
physics.
An 8.97Kcs audio tone is attenuated at 130dB/km.
You are proposing concentrating the sound in one direction, analogous to
a directive antenna, still with say 10kW and an 'antenna' (actually speaker
directivity) gain of say 30dB you would start out with effectively 10MW,
but with 130dB/km you would be down to 1 microwatt at a distance of 1km
!!!
Ten MEGAWATTS becomes 1 MICROWATT after 1km at 8.97 kHz!!!
Case closed!
On Wed, Sep 1, 2010 at 12:13 PM, mal hamilton <[email protected]>
wrote:
With all the energy concentrated into a single
tone on 8.97 Kcs it could well travel a considerable distance
with a few Kilowatts of audio beamed in an arranged direction,
especially along a valley.
I am surprised that the high voltage 50 Hz
electricity overhead distribution network is not heard over great
distances by ear.
g3kev
----- Original Message -----
Sent: Wednesday, September 01, 2010
3:31 PM
Subject: Re: LF: VLF THOUGHT
Rik,
Krakatoa exploded with the equivalent force of 200
Megatons of TNT, bigger than the largest Hydrogen bomb and 13,000 times
the size of the nuclear explosion that destroyed Hiroshima.
That said, I believe that what was hear at a distance
was still the low frequency rumble, 100Hz is attenuated at only 0.3dB/km
while 10kHz is attenuated over 150dB/km.
Best to stick with EM waves as opposed to sound.
- 73 Warren K2ORS
WD2XGJ
WD2XSH/23
WE2XEB/2
WE2XGR/1
On Wed, Sep 1, 2010 at 3:58 AM, Rik Strobbe <[email protected]> wrote:
All,
here
some real "DX":The explosion of the Krakatoa (1883) was heard in Perth
(Australia), 3100 km away, and on the island of Rodrigues, 5000 km
away.
73, Rik
ON7YD
________________________________________
Van: [email protected] [[email protected]] namens Klaus von
der Heide [[email protected]]
Verzonden: woensdag 1
september 2010 9:43
Aan: [email protected]
Onderwerp: Re: LF: VLF
THOUGHT
Hello All,
two years ago someone disturbed my
breakfast by a deeply
hammering disco sound. So I took my car to
search for
the source. Surprisingly, the sound decreased to
nearly
zero when I drove some kilometers in that direction
where
the sound seem to come from. The Odyssey took 45
minutes.
But finally I found the open-air disco 20 km from my
home
in a lonely wood.
Indeed, the sound took nearly 60
seconds from there to my
home. That's more than a thunder usually
reaches.
More than thousand square-kilometers where
contaminated,
including 23 protected nature resevats.
Yes we
can, but Mankind should not do everything what it
can.
73!
Klaus,
DJ5HG
- -- 73 Warren K2ORS
WD2XGJ
WD2XSH/23
WE2XEB/2
WE2XGR/1
|
