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Bible Encyclopedias
Phonograph
1911 Encyclopedia Britannica
or (Gr. 00)1)17, sound, ypa4 €tv, to write), an instrument for imprinting the vibrations of sound on a moving surface of tinfoil or wax in such a form that the original sounds can be faithfully reproduced by suitable mechanism. Many attempts had been made by earlier experimenters to obtain tracings of the vibrations of bodies emitting sound, such as tuning-forks, membranes, and glass or metallic disks. In 1807 Thomas Young (Lectures, i. 191) described a method of recording the vibrations of a tuning-fork on the surface of a drum; his method was fully carried out by Wilhelm Wertheim in 1842 (Recherches sur l'elasticite, t er mem.). Recording the vibrations of a membrane was first accomplished by Leon Scott in 1857 by the invention of the "phonautograph," which may be regarded as the precursor of the phonograph (Comptes rendus, 53, p. 108). This instrument consisted of a thin membrane to which a delicate lever was attached. The membrane was stretched over the narrow end of an irregularly-shaped funnel or drum, while the end of the lever or marker was brought against the surface of a cylinder covered with paper on which soot had been deposited from a flame of turpentine or camphor. The cylinder was fixed on a fine screw moving horizontally when the cylinder was rotated. The marker thus described a spiral line on the blackened surface. When sounds were transmitted to the membrane and the cylinder was rotated the oscillatithm of the marker were recorded. Thus tracings of vibrations were obtained. This instrument was much improved by Karl Rudolph Kdnig, of Paris, who also made with it many valuable observations. (See Nature, Dec. 26, 1901, p. 184). The mechanism of the recording lever or marker was improved by William Henry Barlow, in 1874, in an instrument called by him the "logograph" (Trans. Roy. Soc., 1874). The next step was Kbnig's invention of manometric flames by which the oscillations of a thin membrane under sound-pressures acted on a small reservoir of gas connected with a flame, and the oscillations were viewed in a rotating rectangular mirror, according to a method devised by Charles Wheatstone: Thus flamepictures of the vibrations of sound were obtained (Pogg. Ann., 1864, cxxii. 242, 660; see also Quelques experiences d'acoustique, Paris, 1882). Clarence Blake in 1876 employed the drumhead of the human ear as a logograph, and thus obtained tracings similar to those made by artificial membranes and disks (Archiv. fiir Ophthalmol., 1876, v. i.). In the same year Sigmund Theodor Stein photographed the vibrations of tuning-forks, violin strings, &c. (Pogg. Ann., 1876, p. 142). Thus from Thomas Young downwards successful efforts had been made to record graphically on moving surfaces the vibrations of sounds, but the sounds so recorded could not be reproduced. This was accomplished by T. A. Edison in 1876, the first patent being dated January 1877.
In the first phonograph a spiral groove was cut on a brass drum fixed on a horizontal screw, so that when the drum Was rotated it moved from right to left, as in the phonautograph. The recorder consisted of a membrane of parchment or gold-beater's skin stretched over the end of a short brass cylinder about 2 in. in diameter. In the centre of the membrane there was a stout steel needle having a chisel-shaped edge, and a stiff bit of steel spring was soldered to the needle near its point, while the other end of the spring was clamped to the edge of the brass cylinder over which the membrane was stretched. The recorder was then so placed beside the large cylinder that the sharp edge of the needle ran in the middle of the spiral groove when the cylinder was rotated. The cylinder was covered with a sheet of soft tinfoil. During rotation of the cylinder, and while the membrane was not vibrating, the sharp edge of the marker indented the tinfoil into the spiral groove; and when the membrane was caused to vibrate by sounds being thrown into the short cylinder by a funnel-shaped opening, the variations of pressure corresponding to each vibration caused the marker to make indentations on the tinfoil in the bottom of the groove. These indentations corresponded to the sound-waves. To reproduce the sounds the recorder was drawn away from the cylinder, and the cylinder was rotated backwards until the recorder was brought to the point at which it started. The cylinder was then rotated forwards so that the point of the recorder ran over the elevations and depressions in the bottom of the groove. These elevations and depressions, corresponding to the variations of pressure of each sound-wave, acted backwards on the membrane through the medium of the marker. The membrane was thus caused to move in the same way as it did when it was made to vibrate by the sound-waves falling upon it, and consequently movements of the same general character but of smaller amplitude were produced, and these reproduced sound-waves. Consequently the sound first given to the phonograph was reproduced with considerable accuracy. In 1878 Fleeming Jenkin and J. A. Ewing amplified the tracings made on this instrument by the sounds of vowels, and submitted the curves so obtained to harmonic analysis. (Trans. Roy. Soc. Edin. xxviii. 745). The marks on the tinfoil were also examined by P. F. F. Gri tzner, Mayer, Graham Bell, A. M. Preece, and Lahr (see The Telephone, the Microphone, and the Phonograph, by count du Moncel, London, 1884;1884; also The Speaking Telephone and Talking Phonograph, by G. B. Prescott, New York, 1878).
The tinfoil phonograph, however, was an imperfect instrument, both as regards the medium on which the imprints were taken (tinfoil) and the general mechanism of the instrument. Many improvements were attempted. From 1877 to 1888 Edison was engaged in working out the details of the wax-cylinder phonograph. In 1885 A. G. Bell and S. Tainter patented the "grapophone," and in 1887, Emile Berliner, a German domiciled in America, patented the "gramophone," wherein the cylinder was coated with lampblack, and the friction between it and the stylus was made uniform for all vibrations. Incidentally it may be mentioned that Charles Cross deposited in 1877 a sealed packet with the Academic des Sciences, Paris, containing a suggestion for reproducing sound from a Scott phonautograph record. The improvements made by Edison consisted chiefly (I) in substituting for tinfoil cylinders or disks made of a waxy substance on which permanent records are taken; (2) in substituting a thin glass plate for the parchment membrane; (3) in improving the mechanical action of the marker; and (4) in driving the drum carrying the wax cylinder at a uniform and rapid speed by an electric motor placed below the instrument.
In the first place, permanent records can be taken on the wax, which is composed of stearin and paraffin. This material is brittle, but it readily takes the imprints made by the marker, which is now a tiny bit of sapphire. The marker, when used for recording, is shod with a chisel-shaped edge of sapphire; but the sapphire is rounded when the marker is used for reproducing the sound. The marker also, instead of being a stiff needle coming from the centre of the membrane or glass plate, is now a lever, weighted so as to keep it in contact with the surface of the wax. A single vibration of a pure tone consists of an increase of pressure followed by a diminution of pressure. When the disk of glass is submitted to an increase of pressure the action of the lever is such that, while the wax cylinder is rotating, the point of the marker is angled downwards, and this cuts deeply into the wax; and when there is diminution of pressure the point is angled upwards, so as to act less deeply. In reproducing the sound, the blunt end of the marker runs over all the elevations and depressions in the bottom of the groove cut on the wax cylinder. There is thus increased pressure transmitted upwards to the glass disk when the point runs over an elevation, and less pressure when the point runs over a depre.»ion on the wax cylinder. The glass disk is thus, as it were, pulled inwards and thrust outwards with each vibration, but these pulls ,! Il p p gat: p N FIG. Ia. - Exterior of Edison Phonograph.
and thrusts follow each other so rapidly that the ear takes no cognizance of the difference of phase of the vibrations of the glass plate in imprinting and in reproducing. The variations of pressure are communicated to the glass plate, and these, by the medium of the air, are transmitted to the drum-head of the ear, and the sound is reproduced with remarkable fidelity. It is necessary for accurate reproduction that the point of the marker be in the centre of the groove. In the older phonographs this required accurate adjustment by a fine screw, but in newer forms a certain amount of lateral oscillation is allowed to the marker, by which it slips automatically into the groove. Two other improvements have been effected in the construction of the instrument. A powerful triple-spring motor has been substituted for the electric motor, and the circumference of the wax cylinder has been increased from 68 in. to 15 in., whilst the disk is 12 in. in diameter. The cylinders make about two revolutions per second, so that with the smaller cylinder the point of the marker runs over nearly 14 in. in one second, while with the larger it runs over about 30 in. The marks corresponding to the individual vibrations of tones of high pitch are therefore less likely to be crowded together with the larger cylinder, and these higher tones in particular are more accurately reproduced. In a form of instrument called the 200-thread machine motion of the drum bearing the cylinder was taken off a screw the thread of which was 50 to the inch, and by a system of gearing the grooves on the cylinder were 200 to the inch, or 2 4, of an inch apart. It was somewhat difficult to keep the marker in the grooves when they were so close together; and the movement is now taken directly off a screw the thread of which is loo to the inch, so that the grooves on the cylinder are iozof an inch apart. Thus with the large cylinder a spiral groove of over 300 yds. may be described by the recorder, and with a speed of about two revolutions per second this distance is covered by the marker in about six minutes. By diminishing the speed of revolution, which can be easily done, the time may be considerably lengthened.
In the plate machine the disk is fixed to a table which is rotated at a fixed speed of about 76 revolutions a minute. The speed of the lateral movement of the table is alsc unifcrm, and by a regular progression brings the wax blank under the sound-box to the sapphire cutting point, which detaches a fine unbroken thread of wax as it cuts into the surface of the blank to a depth of 32to 4thousandths of an inch, beginning at about half an inch from the circumference and continuing the spiral groove to within a couple of inches of the centre, according to the length of the music to be recorded. The essential difference between the disk and cylinder machine is that in the former the waves are recorded by horizontal motion over the disk, while in the latter the waves are recorded as indentations.
The following is the modus operandi of making a reccrd. The person making the record sings or plays in front of a horn or funnel used for the purpose of focusing the sound-waves upon the diaphragm. The artist and the funnel are on one side of a screen and the recording apparatus in charge of an operator on the other. The arrangement of the various instruments in the recording room at proper relative distances from the horn is of the utmost importance in order to preserve the balance of tone. At about 4 ft. from the horn are grouped the violins and the wood wind (flutes, oboes and clarinets); behind the brass wind (horns, trumpets, trombones and tubers), and right at the back the violoncellos and double basses and the kettle-drums and other instruments of percussion which may be required. On the other side of the screen is the sound-box and the recording cylinder or disk.
Cylinder records are duplicated by taking a plaster cast, electroplating, and then using it as a matrix. The disk record admits of similar treatment. After dusting with graphite it is electroplated to about '9 mm. thick. This forms the permanent or master record, from which the working negatives are made by taking wax impresses of it and obtaining copper electros in turn from them. The matrix is then nickel-plated and polished and is ready for use in pressing out the commercial records by means of an hydraulic press, the material used being a tough and elastic substance containing shellac and other compounds such as wood charcoal, barium sulphate, earthy colouring matters and cotton flock.
There is still a defect to be overcome in the gramophone, and that is the hissing of the needle produced by friction both during recording and intensified in reproduction. In one device for remedying this the stylus acts like a stylographic pen, depositing on a polished surface a fine stream of some liquid which solidifies and hardens very rapidly, forming a sinuous ridge instead of a groove in a wax blank. A negative is taken of the record and the matrix is made from it in the usual way.
FIG. 1 b. - Mechanism of Edison Phonograph.
The auxeto-gramophone or auxetophone, patented by Short in 1898 and improved by the Hon. C. A. Parsons, is similar in scope to the gramophone but attains its results in a different manner. In the Parsons-Short sound-box there is no diaphragm, but a I f 1 ?11?1?!?p? a ,!ilillt111?11I?(?? { Illl i ?f l?I q j I l lll ? 1'111111111111 ' ll lll il 1111111 I Illillilul ? ??Ili l ll h' i column of compressed air is controlled by a delicately adjusted grid-valve consisting of a metal comb rigidly connected to the stylus bar, so that as the needle moves the metal comb moves with it, following the lines of vibration fixed on the record and opening or closing the slots in the valve seat. The column of compressed air to which the valve gives access thus receives series of minute pulsations identical with those which originally produced the sounds recorded. In connexion with the sound-box is the apparatus for supplying compressed air, consisting of a sixth-horse power electric motor driving the compressor, an oil filter, a reservoir and a dust collector to keep the air absolutely free from foreign substances likely to interfere with the action of the valve.
The practical possibilities of the gramophone are being realized in many countries. Matrices of the records of wellknown artists have been deposited at the British Museum and at the Grand Opera in Paris. Austria established a public phonogram record office in 1903, in which are collected folksongs and records of all kinds for enriching the department of ethnography. The same idea is being carried out in Germany FIG. 2.
by private societies and by royal museums. In Hungary records of the various dialects have been secured. The possibilities of the gramophone as a teacher are far-reaching, not only in the domain of music but in learning languages, &c.
To understand how the phonograph records and reproduces musical tones, it is necessary to remember (1) that pitch or frequency depends on the number of vibrations executed by the vibrating body in a given period of time, or on the duration of each vibration; (2) that intensity or loudness depends on the amplitude of the movement of the vibrating body; and (3) that quality, timbre or clang, first, depends on the form of the individual vibrations, or rather on the power the ear possesses of appreciating a simple pendular vibration producing a pure tone, or of decomposing more or less completely a compound vibration into the simple pendular vibrations of which it is composed. If we apply this to the record of the phonograph, we find that, given a constant and sufficiently rapid velocity of the record, a note or tone of a certain pitch will be heard when the marker runs over a number of elevations and depressions corresponding to the frequency of that note. Thus if the note was produced by 200 vibrations per second, and suppose that it lasted in the music for of a second, 20 marks, each made in 2160 of a second, would be imprinted on the wax. Consequently, in reproduction, the marker would run over the 20 marks in of a second, and a tone of that frequency would be reproduced.
The loudness would correspond to the depth of each individual mark on the cylinder or the width on the disk. The greater the depth of a series of successive marks produced by a loud tone, the greater, in reproduction, would be the amplitude of the excursions of the glass disk and the louder would be the tone reproduced. Lastly, the form of the marks corresponding to individual vibrations would determine the quality of the tone or note reproduced, by which we can distinguish the tone of one instrument from another, or the sensation produced by a tone of pure and simple quality, like that from a well-bowed tuning-fork or an open organ pipe, and that given by a trumpet or an orchestra, in which the sounds of many instruments are blended together. When the phonograph records the sound of an orchestra it does not record the tones of each instrument, but it imprints the form of impression corresponding to the very complex sound-wave formed by all the instruments combined. This particular form, infinitely varied, will reproduce backwards, as has been explained, by acting on the glass plate, the particular .9 10 11 12 form of sound-wave corresponding to the sound of the orchestra. Numerous instruments blend their tones to make one wave-form, and when one instrument predominates, or if a human voice is singing to the accompaniment of the orchestra, another form of sound-wave, or rather a complex series of sound waves, is imprinted. When reproduced, the wave-forms again exist in the air as very complex variations of pressure; these act on the drum-head of the human ear, there is transmission to the brain, and there an analysis of the complex sensation takes place, and we distinguish the trombone from the oboe, or the human voice from the violin obbligato.
