Phonozoic Text Archive, Document 130


Charles Cros
Proc�d� d�enregistrement et de reproduction des ph�nom�nes per�us par l�ou�e (1877)

Comptes Rendus Hebdomaires des S�ances de l�Acad�mie des Sciences, Vol. 85 (July-December 1877), 1082-3.  Meeting of December 3, 1877.

M. Ch. Cros demande l�ouverture d�un pli cachet�, d�pos� par lui le 30 avril 1877 et portant pour titre: � Proc�d� d�enregistrement et de reproduction des ph�nom�nes per�us par l�ou�e �.

 

Ce pli, ouvert en s�ance par M. le Secr�taire perp�tuel, contient la Note suivante:

 

�En g�n�ral, mon proc�d� consiste � obtenir le trac� du va-et-vient d�une membrane vibrante et � se servir de ce trac� pour reproduire le m�me va-et-vient, avec ses relations intrins�ques de dur�es et d�intensit�s, sur la m�me membrane ou sur une autre, appropri�e � rendre les sons et bruits que r�sultent de cette s�rie de mouvements.

 

�Il s�agit donc de transformer un trac� extr�mement d�licat, tel que celui qu�on obtient avec des index l�gers fr�lant des surfaces noircies � la flamme, de transformer, dis-je, ces trac�s en reliefs ou creux r�sistants, capables de conduire un mobile qui transmettra ses mouvements � la membrane sonore.

 

�Un index l�ger est solidaire du centre de figure d�une membrane vibrante; il se termine par une pointe (fil m�tallique, barbe de plume, etc.) qui repose sur une surface noircie � la flamme.  Cette surface fait corps avec un disque anim� d�un double mouvement de rotation et de progression rectiligne.  Si la membrane est en repos, la point tracera une spirale simple; si la membrane vibre, la spirale trac�e sera ondul�e, et ses ondula- [1083] tions repr�senteront exactement tous les va-et-vient de la membrane, en leurs temps et en leurs intensit�s.

 

�On traduit, au moyen de proc�d�s photographiques actuellement bien connus, cette spirale ondul�e et trac�e en transparence, par une ligne de semblable dimension, trac�e en creux ou en relief dans une mati�re r�sistante (acier tremp�, par exemple).

 

�Cela fait, on met cette surface r�sistant dans un appareil moteur qui la fait tourner et progresser d�une vitesse et d�un mouvement pareils � ceux dont avait �t� anim�e la surface d�enregistrement.  Une pointe m�tallique, si le trac� est en creux (ou un doigt � encoche, s�il est en relief), est tenue par un ressort sur ce trac�, et, d�autre part, l�index qui supporte cette pointe est solidaire du centre de figure de la membrane propre � produire des sons.  Dans ces conditions, cette membrane sera anim�e, non plus par l�air vibrant, mais par le trac� commandant l�index � pointe, d�impulsions exactement pareilles, en dur�es et en intensit�s, � celles que la membrane d�enregistrement avait subies.

 

�Le trac� spiral repr�sente des temps successifs �gaux, par es longueurs croissantes ou d�croissantes.  Cela n�a pas d�inconv�nients si l�on n�utilise que la portion p�riph�rique du cercle tournant, les tours de spire �tant tr�s-rapproch�s; mais alors on perd la surface centrale.

 

�Dans tous les cas, le trac� en h�lice sur un cylindre est tr�s-pr�f�rable, et je m�occupe actuellement d�en trouver la r�alisation pratique.�

Mr. Ch. Cros asks for the opening of a sealed envelope, deposited by him on 30 April 1877 and bearing as a title: "Process of recording and reproduction of the phenomena perceived by hearing."

This envelope, opened during the meeting by Mr. Perpetual Secretary, contains the following Note: 

"In general, my process consists of obtaining the trace of the to-and-fro movement of a vibrating membrane and making use of this trace to reproduce the same to-and-fro movement, with its intrinsic relationships of durations and intensities, on the same membrane or on another one suited to returning the sounds and noises which result from this series of movements.

"It is thus a matter of transforming an extremely delicate trace, such as that which one obtains with light styli [index] brushing against surfaces blackened with flame; of transforming, I say, these traces into durable reliefs or depths capable of leading a moving body which will transmit its movements to the sound membrane.

"A light stylus is connected to the center of a vibrating membrane; it ends in a point (metal wire, barb of a feather, etc.) which rests on a surface blackened with flame. This surface is joined with a disc animated by a double movement of rotation and rectilinear progression. If the membrane is at rest, it will trace a simple spiral; if the membrane vibrates, the traced spiral will be undulated, and its undulations will represent exactly in their times and their intensities all the to-and-fro movement of the membrane.

"By means of photographic processes currently well-known, one translates this spiral, undulated and traced in transparency, into a line of similar dimension traced in intaglio or relief in a durable material (tempered steel, for example).

"That done, one puts this durable surface into a driving apparatus which causes it to turn and move forward at a speed and with a movement identical to those with which the recording surface had been animated. A metal point, if the trace is in intaglio (or a notched stylus, if it is in relief), is held onto this trace by a spring, and, on the other side, the stylus which supports this point is connected to the center of the membrane suitable for producing sounds. Under these conditions, this membrane will be animated, no longer by the vibrating air but by the trace controlling the stylus with the point, with impulses exactly identical in durations and intensities to those which the recording membrane had undergone.

"The spiral trace represents equal successive times by increasing or decreasing lengths. That does not have disadvantages if one uses only the peripheral portion of the turning circle, the turns of the spiral being brought much closer together; but then central surface is lost.

"In any case, the helical layout on a cylinder is much preferable, and I am currently occupying myself with finding its practical realization."

English translation by Patrick Feaster.


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