You quoted;
> .....The explanation emerged the following morning. Mr Tandy,
> a fencing enthusiast, was modifying one of his foils and had
> left the blade clamped in a vice while he went in search of
> oil. He said "When I returned, I noticed that the free end
> of the blade was frantically vibrating up and down." Mr
> Tandy, a trained engineer, realised that the blade might
> be receiving energy from very low frequency sound waves
> filling the laboratory - so low that they could not be
> heard.
>
> Tests duly revealed the existence of a "standing wave"
> trapped in the laboratory, which reached a peak in
> intensity next to Mr Tandy's desk. "It turned out to be
> caused by a new extraction fan, which was making the air
> vibrate at about 19 cycles per second," Mr Tandy said.
> "When the fan's mounting was altered, the ghost left with
> the standing wave."
What an interesting discovery!!! Thanks Jim for posting it...the part
about the fencing sword vibrating to detect the standing wave just
really intrigues me. It ties in with the claims about Tesla and a small
mechanical vibrator that was supposed to have been attached to a huge
chain link from a boat anchor...the story said as the mechanical
oscillator coupled to the chain at resonance, that the oscillations
eventually made the chain pulse like a human heart until the metal
shattered...
Now that story is not one told by Tesla that I've ever been able to find
a quote about, but it is akin to the story told by Tesla in at least two
books about his life where he is said to have attached a similar
mechanical oscillator to a support of a building...as the metal support
began to pulse the building nearly collapsed, so the story goes.
I have an interesting mechanical device that I got from Abbeon Cal which
lets you measure mechanical vibration. It has these two wires that
slide out of it. You are supposed to put the end of the device on the
vibrating surface (motor or whatever) then slide the collar over the
wire until you get the maximum swing in the wires...the shaft the collar
moves over is graduated, so when you are happy that the amplitude is at
maximum, you can just read the cycles per second on the shafte.
I've always been puzzled about how one could built a small hand held
model that would cause massive resonance amplification.
-- Jerry Wayne Decker / jdecker@keelynet.com http://keelynet.com / "From an Art to a Science" Voice : (214) 324-8741 / FAX : (214) 324-3501 KeelyNet - PO BOX 870716 - Mesquite - Republic of Texas - 75187