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HOW TO MAKE A
PHONOGRAPH
By W A L T E R LEE
N case any person of a mechanical
turn of mind wishes to try his hand
at building a talking machine, I will
explain what I used and how I used
it. But before I do so, it may be
well to explain, in a general way, the
principle of phonography, so that the
experimenter will know just what he is
doing and why he is doing it that way.
When a pig squeals, the vibrations of
the cords in his throat, or wherever his
squeal apparatus is located, cause the
surrounding air to vibrate. The vibrations
move away
from that center,
in all directions,
like the ripples in
a placid pool of
water when a pebble
is thrown into
it. They are called
sound waves. They
come in contact
with the drums of
our ears, which, in
their turn, begin to
vibrate, and this
vibration of the
ear drums is what
we call a noise. We
hear the pig
squeal, but his
squeal was perfect
silence until it
reached our ear
drums. If there were no ears, there
would be no sound, but the sound waves
would be present, ready to be converted
into sounds, just the same.
A recording phonograph is a machine
with an ear drum. The ear drum is a
glass disc, or diaphragm, which vibrates
as an ear drum, when sound waves come
in contact with it. The record makers
cause the sound vibrations, by singing,
or playing, or talking, in the immediate
vicinity of the machine, and the waves
then vibrate the diaphragm, which has a
sharp needle so attached to it that it will
make certain movements in exact correspondence
with the diaphragm. The
machine is so built, that a plate or plane
of wax is revolved with its surface in
contact with the needle, and thus, when
the diaphragm vibrates, the needle
moves, and traces a wavy line in the
wax. This wavy line represents the
sound waves that
vibrated the diaphragm.
Now, if
the wax is hardened,
and the angle
of the needle is
changed so it will
go over the same
path again without
digging into it, the
wavy line will
cause the needle to
move, and the
needle will cause
the diaphragm to
vibrate, and that
will set up a correspondingvibration
in the air.
The sound waves
The Homemade "De Luxe Model" thus created, reach
our ear drums,
which in turn vibrate, and we hear the
same sounds that were originally thrown
into the recording phonograph.
My home-made machine consists of
the following articles, which I picked up
around the house and basement. One
soap box. one movement from a discarded
eight day clock, one tin megaphone,
two feet of three-quarter-inch
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