 |
| Fig. 323 – The Young’s machine,
capable to reproduce the sound vibrations in a chart. |
Since the beginning, mankind wanted to record and playback
the natural sounds. Shelled hands were used to amplify battle
cry by the ancient tribes. In the middle ages several musical
instruments were already known. Therefore it was not possible
to record the sound waves.
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| Fig. 324 - The phonautograph invented
by Martinville. |
In the XVIII century through the birth of new studies several
branches of the natural and physical sciences were improved
deeply. Thus, for instances: Acoustics with Gay-Lussac studies;
Arago calculating the velocity of sound in the air; Savart
determining musical pitch by mean of a toothed wheel and,
Helmholtz bringing into practice the harmonics’ law.
Certainly, those scientific improvements were the basis for
the delineation of the principles to be used either for recording
as well as the reproduction of the natural sound.
Thomas Young was the first to reproduce the sound vibration
through a chart. Fig 323
In 1817, Leon Scott de Martinville invented “the phonautograph”,
basically consisted of a trumpt that collected the air vibration
actuatying as a resonant chamber. Fig. 324
 |
| Fig. 325 - Edison and his invention
the phonograph. |
At the smaller end of trumpt there was a thin membrane, which
convert the alternate air pressures into mechanical movements;
later this kind of device was named as diaphagram.
In April 1877, Charles Cros introduced to the French Science
Academy a project for a sound-reproducing machine.
Therefore, Thomas Alva Edison invented the practical conception
for a machine capable to record and reproduce the natural sounds
accidentally in 1870. In the reality, Edison was in the course
of a series of extended experiments to improve the telegraphic
transmissions, which firstly encode a message by mean of holes
made in a strip of paper, from which at any subsequent time
might be automatically sent.
Basically this machine consisted a disc in which was wrapped
a piece of paper.
The message was recorded by indentation made by mean of a needle
during the rotation of the disc. In manipulating the strip of
paper Edison found that that when the indented paper was turned
with great swiftness, it gave of a humming sound resembling
that of the human talk heard indistinctly.
 |
| Fig 325A - The original Edison’s
phonograph project. |
This led him to think if it were possible to use the oscillation
of the needle to record the human speech.
As yet the Edison’s machine to record the human speech
was crude, but is characterized by wonderful mechanical precision.
The machine that Edison designed consisted basically of a metall
cylinder, which was mounted on a screw; so that turning a handle
would make it both revolve and move from left to right.
Over the cylinder provided with final spiral grooves impressed
in its surface. On each end of the machine were assembled
two diafragm-and needle units in such away one to be used
for recording, and the other for reproduction of the sounds.
A piece of tin foil was wrapped around the cylinder, and thereon
the recording needle, following the spiral grooves, would
indent a pattern of the sound vibration directed into the
mouth piece. On replaying, the reproduction needle was to
convert these indentions on the tin foil back into sound.
Since February 29 1877, when a patent was granted, this machine
as known as phonograph, has arisen enormous curiosity and
just one year a after his launching circa 600 units was already
built and in this way carving out the way for the phonograph
industry. Fig. 325
 |
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| Fig. 325B - An early office’s
recorder made in 1920 by the American company Dictaphone
Corporation using the same principle of the Edison’s
phonograph. |
Fig. 325C - A detailed overview of the
office’s recorder. |
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