1874 __ « On the Pneumatic Action which accompanies the Articulation of Sounds by the Human Voice, as exhibited by a Recording Instrument » — Logograph
‣ Comment : In this paper Barlow describes his ‘Logograph’ and gives several traces of complete words and sentences, including the word ‘Incomprehensibility’, and lines from the poem ‘Hohenlinden’. — For recording vocal impulses one of the most sensitive instrument is the logograph, invented by W.H. Barlow. The pressure of the air in speaking is directed against a membrane, which vibrates and carries with it a delicate marker, which traces a line on a travelling ribbon. The excursions of the tracer are great or small from the base line which represents the quiet membrane, according to the force of the impulse, and are prolonged according to the duration of the pressure, different articulate sounds varying greatly in length as well as in intensity; another great difference in them also consists in the relative abruptness of the rising and falling inflections, which makes curves of various shapes. The smoothness or ruggedness of a sound has thus its own graphic character, independent both of its actual intensity and its length. The logograph consists of a small speaking trumpet, having an ordinary mouth-piece connected to a tube, the other end of which is widened out and covered with a thin membrane of gold beater's skin of gutta percha. A spring presses slightly against the membrane, and has a light arm of aluminium, which carries the marker, consisting of a small sable brush inserted in a glass tube containing a colored liquid. An endless strip of paper is caused to travel beneath the pencil, and is marked with an irregular curved line, the elevations and depressions of which correspond to the force, duration and other characteristics of the vocal impulses. The lines thus traced exhibit remarkable uniformity when the same phrases are successively pronounced. (George Bartlett Prescott)
‣ Original excerpt : « February 23, 1874. — All articulated sounds made by the human voice are accompanied by the expulsion of air from the mouth; and in a series of articulated sounds the air is ejected in impulses which vary in quantity and pressure, and in the degree of suddenness with which they commence and terminate. It appeared to me that it would be interesting and probably useful, as tending to elucidate the process and effects of articulation, to construct an instrument which should record these pneumatic actions by diagrams, in a manner analogous to that in which the indicator-diagram of a steam-engine records the action of the engine. In considering a suitable form of recording instrument, the conditions to be met were:- first, that the pressure and quantities were very variable, some of them being extremely small; and secondly, that the impulses and changes of pressure follow each other with great rapidity. It was therefore necessary that the moving parts should be very light, and that the movement and marking should be accomplished with as little friction as possible. The instrument I have constructed consists of a small speaking-trumpet about 4 inches long, having an ordinary mouthpiece connected to a tube ½ an inch in diameter, the other end of which is widened out so as to form an aperture of 2¼ inches diameter. This aperture is covered with a membrane of goldbeater’s skin or thin gutta percha. A spring which carries the marker is made to press against the membrane with a slight initial pressure, to prevent as far as practicable the effects of jar and consequent vibratory action. A very light arm of aluminium is connected with the spring and holds the marker; and a continuous strip of paper is made to pass under the marker in the same manner as that employed in telegraphy. [...] My object, however, has not been to pursue the subject into minute detail, but to show that the articulation of the human voice is accompanied by definite pneumatic actions, and that those actions, many of which are insensible to ordinary observation, are capable of being recorded. » (Proceedings of the Royal Society of London Vol XXII, April 16, 1874)
‣ Source : Barlow W. H. (1874), “ On the Pneumatic Action which accompanies the Articulation of Sounds by the Human Voice, as exhibited by a Recording Instrument”, Proceedings of the Royal Society of London, January 1, 1873, 22:277-286.
‣ Source : Prescott, George Bartlett (1972), “Bell's electric speaking telephone: its invention, construction, application, modification, and history”, Ayer Publishing, pp. 179-180.
‣ Urls : http://members.lycos.co.uk/MikePenney/barlow.htm (last visited )
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