LF: Re: VLF THOUGHT

["James Moritz" <james.moritz@btopenworld.com>]

Dear Mal, LF Group,



G3KEV wrote:
...Theoretically that is correct ...

And also wrote:
...Miracles are possible but impossibilities take a little longer.
Some serious THOUGHT needs to go into this subject.
Too many theory merchants about and no field experience...

Umm yes. Very nicely put Mal ... I think ;-)


I can sometimes hear the outdoor music events at Knebworth, about 20km from 
my QTH, where they are probably using similar amplifiers and speakers to the 
ones you were talking about. But all you can hear is a sort of low rythmic 
rumble, certainly anything in the kilohertz range is totally inaudible at 
this distance.
Sound location of aircraft through their engine noise was developed fairly 
intensively in the 1930s, but was abandoned because radar techniques proved 
much more practical - I seem to remember the maximum range for aircraft 
detection using sound was only about 30km under perfect conditions, 
requiring a very low background acoustic noise level. There has been a long 
military history of sound location since the first world war, for locating 
artillery positions, etc. But this is again using low frequency sound, and 
over relatively short distances. For detection of long-distance sounds, you 
may like to try Googling "Project Mogul", if you don't mind wading through 
all the UFO-related stuff...
Cheers, Jim Moritz
73 de M0BMU