Archive of the former Yahoo!Groups mailing list: MOTM

Sound travels at a speed of approximately 1130 feet per second.
Therefore the wavelength of a "sound wave" at a frequency of 1 Hz is
1130 feet.
The speed of sound does vary with some conditions such as elevation,
atmospheric pressure, humidity and temperature.
If I remember correctly an open organ pipe resonates at the
wavelength equal to the length of the pipe. I think a pipe closed
at one end resonates at a frequency of either twice the wavelength
or half the wavelength, I can't remember which off the top of my
head.
A 64' pipe would resonate at 17.65 Hz.
A 1' pipe would resonate at 1130 Hz.
You can make an organ pipe resonator by mounting tubes cut to the
proper lengths in front of a speaker. The notes corresponding to
the resonant pipes will ring producing a very nice reverb type
effect. (Something I built out fo PVC and copper pipe in the days
of my misspent youth.)
One other interesting bit of organ trivia.
Typically you would have multiple stops open at any given time.
Every note has a corresponding pipe for each stop.
So if you had a pipe organ with 25 stops for the "Swell" keyboard
you would have 1525 pipes!!!
The different timbres are produced by the shape, materials and
construction of the pipes themselves.
Each pipe is tuned by hand either using mechanical adjustment which
is sometimes a tab or a stopper. Since these pipes are not going to
be perfectly in tune with each other there is always some beating,
often at very low frequencies (less than 1 Hz.) Since these pipes
are located throughout a large area standing waves do not actually
stand but move as the beating occurs. This gives the sound a great
deal of movement and makes the sound appear to come from all
directions.
The Leslie speaker is an attempt to reproduce this movement.
I've often thought about what it would take to reproduce this effect
using signal processors. You can reproduce the effect to a degree
using pitch shifters set to very slight shifts and multiple
speakers, but without sending different notes through different
shifter the effect is not the same.
This is also the reason that it is very difficult to record pipe
organ (or an orchestra for that matter.) The movement of the
standing waves cannot be reproduced.
Paul Haneberg (Pipe Organ Fanatic as well as Synth Fanatic)