US1101906A - Method of recording and reproducing sound. - Google Patents

Description

F. W. H. CLAY.

METHOD 0E. RECORDING AND EEPBODUOING SOUND. APPLiOATION FILED c0T.2s,19om

1,101,906. Y Patented June .30, 1914,

FIG.

T mvamon ATTORNEY.

UNITED STATES PATENT orrros.

FRANCIS '.W., H'- CLAY, OF PITTSBURGH, PENNSYLVANIA.

' mnrnon or nnconnme'ann nnrnonucmc'sounn.

Specification of Letters Patent.

- Eastman, 1914.

Application filed October 25, 19cm Serial 110,339,112.

primary .object is. to smooth the irregu larities' of natural sound wave records, and

vavoid the noises incident to :the reproduction, etc.

Other objects will appear hereinafter. I have here illustrated the method as applied to instruments such as phonograp s other applications such as telephoning. I

In the accompanying drawing Figure 1 is a diagram illustrating v sound on a wax cylinder, and 2 amodification of the apparatus. Fig. ;3 illustrates the apparatus which may be used for recording on flat surfaces. :Fig. 4 illustrates a. construction of a sound actuated diaphragm and Fig. 5 illustrates another modification for dampening irregular waves.

Fig. -6 illustrates some forms of soundwaves. Fig. 7 illustrates the applicationof the invention to telephoning. x

In the study of sound waves I have dis-- covered that the probable cause 'of impure tones is the superimposition, upon the wave form, of irregular subsidiary waves. And a pure tone is distinguished from'an impure tone not. so much by the absence of the superimposed waves, as by their being regular. The tympanum of theear is probably in incessant complicated motion and the'physiological effect of a ;pure tone is largely due to submerging the irregular motions by cans ing the hearing organs to swing in regular rather than irregular order. In the sound .records at present used in phonographs,etc.,

the reproducing diaphragm never vibrates without both fundamental and overtone, and in addition undesirable and minute superposed vibrations of irregular :form. l his is due in part to the imperfections in the structure of the record, and in part to the independent and irregular vibrations of the diaphragm. It is obvious that if the diaphragm is swinging with are lar-periodicity, even if it makes an inaudi le -vibration, this will submerge or drown out the noisy". sounds, for noise difiers from musical sound only by the recording of v reason of the irregularity of vibration. It

is the object of my invention to accomplish this end either by altering the shape of the sound record,-or;by impressing minute regu-. lar vibrations on the reproducing diaphragm. Y q

Referring first to Fig. 6, a puretone might be illustrated by the form A, but owing to mechanical imperfections the actua'l form of the waves produced by phonographs is that shown at Bi. At C is illustrated a form of waveinwhich the superimposed minute -vibrationsi on the fundamental and overtone wave form are made Yregular rather than irregular. In other ;words if the cause of the noise," that is, the and gramophones,butit obviously has many I I irregular forms on the wave B, can be reduced to alregular periodicity as in C, this superposed formcan still be so small as to In other words a, wave form be inaudible. such as C would-produce on the ear the effect ,of a simple and perfectly smooth sound,.be-

cause the ear cannot respond to the small undulations C, while they could perceive the irregular vibrations B because of the irregular beats produced bythem in combination with the fundamental;

In Fig. 1 the wax cylinder 7 upon which .the sound record is anade by the motion of the'cutting tool 8, which in turn is. moved waves, must have cut on its record which will be the resultant of all the motions of the diaphragm and of the varying resistance by the diaphragm "9 actuated by the sound of the cylinder material. It is evident that v if diaphragm 9 be constantly swinging at a regular rate it will not be so susceptible to irregular motions, and it is also evident that thisregular swinging movement would not interfere with the larger movement due to the sound waves. Suppose for example the diaphragm cutting too were throughout the recording process swinging with frequency above limits of audition, somewhere about 40,000 per second" All the audible sound waves desired would have a periodicity not .greater than about 10,000 and the supplementary swingingof the diaphragm might be made as low as twenty thousand in some instances. Any convenient means can be' used ior suoerposing the supplementary vibrations and I have illustrated a magnetic coil 10 which is excited by an alternating.

current source 11 having a periodicity above the limits of audition. The diaphragm 9 of course may be of iron and thereupon it will be kept constantly s\\-'inging at this high frequency, without interfering with its response to the ordinary sound waves. Various forms of apparatus may be used for supplying the supplementary vibration; as in. l 2 the magnetic ring 12 may be eX- cited by coil [3 electrically, and operate on the edges of the recording disk 9. Mechanical means of course might equally Well be used for vibrating the disk.

In Fig. 3 is a form of apparatus for re cording on a fiat surface and here the diaphragm may be operated on by tuning fork l4 kept vibrating by means of an electrical interrupter 15. The recording point 17 will thus be in constant motion at a rate of say 5,000- per second, and this swinging will drown out the tendency to move under the influence of irregular sound waves. By

reason of the momentum also, the recording point obviously will not be in responsive condition for making irregular movements. In both of the forms of apparatus it will be observed also that the varying resistance to cutting, in the material of the cylinder or plate, will be rendered unvarying by reason of the energy of the supplementary vibration, and this will leave the instrument freer to respond to the actual sound waves being recorded. Conversely, in reproducing the sound waves, the stylus and diaphragm will manifestly be kept in the state of extremely rapid and regular vibration of too high frequency to beheard, and this motion will by reason of the momentum prevent any response to irregular noises. The same object of submerging irregular vibrations may be accomplished by covering the diaphragm with a large number of small elements having a definite period of vibration, which will serve to dampen all motions of the diaphragm, except those in harmony with themselves, and thus purify the tone. Thus in Fig. 4; a series of wires A, B, C, D, E, F, each of a length and weight to respond to a simple note, are attached to the diaphragm which is used either for recording or reproducing,

For recording various other methods of dampening irregular vibrations -.may .of course be used and. I have illustrated in Fig. 5 one in which a series of independent diaphragms 18 are placed side by side and communicating their motion. by elastic links 19, so that the recording stylus 8 will be influenced by the cumulative effect of the various diaphragms,it being understood that the space between diaphragms is open and the sound waves are directed in at the point S. Thus the irregular vibrations of the several diaphragms will mutually suppress each other, since the whole set cannot affect the stylus except by acting in unison. Another use of the dampening devices is when will cause sound beats which will increase the amplitude of the desired sounds, and by this means such devices as amplifying horns may be done away with, it being understood that a particular sound wave may be rendered louder not only by increasing the amplitude of motion but by sharpening the apex of the wave. If therefore in the recording device the subsidiary vibrations are made to be a multipleto each of the natural musical tones there will be a regular beat at the crest of each musical tone wave between the fundamental and subsidiary impressed waves. This will amplify the sound and reproduction. Obviously this method of suppressing irregular vibrations may be applied to other instruments such as tele phones. For example if a telephone re ceiver diaphragm be kept in constant vibration at a rate above the limit of audition, this will dampen or cancel all irregular vibi itions without interfering w'th the slower swing of the vocal sounds, and the same method may be used also in the transmitter. Various other uses of this method will occur to those familiar with the art and need not be here set forth in detail.

' I believe I am the first to discover that noise may be suppressed by substituting for the noise wave an inaudible regular wave.

However, the impressed supplementary wave may of course be made audible with some good effects. The fundamental idea of the invention may be illustrated mechanically by saying that it is the object of the supplementary regular waves to comb out the irregularities from the regular sound waves. While I am also the original inventor of means for impressing upon a sound recording instrument a supplementary regular vibration of inaudible frequency, the apparatus herein disclosed is not claimed herein, but

111 my co-pending application No. 724,744

filed Oc 9, 1912.

Having thus described my invention and illustrated its use what I claim as new and desire to secure by Letters Patent is the following 1. The method of recording sound Waves which comprises impressing upon the ordinary motions of the recording instrument, a supplementary regular series of high frequency vibrations.

2. The method which consists in suppressing noises by forcing a vibrating member to regular vibration of higher frequency than the sound waves independently of the source of the sound wave frequency.

3. The method of recording sound which consists in vibrating a recording instrument by the agency of sound waves and impressing on it a regular vibration of higher frequency than that of audible sound.

4. A sound record having in addition to they are tuned to different frequencies, they 1 the undulations of the recorded sounds, a

independent of and higher than the sound wave frequencies.

In testimony whereof I have hereunder signzed myname this Qth day of October, 190

FRANCIS W. H. CLAY.

Witnesses:

C. M. CLARKE, FRED STAUB.

Images