US1680694A - Sound-reproducing method and apparatus - Google Patents

Description

Aug. 14, 1928.

G. RAMSEY SOUND REPRO DUCING METHOD AND APPARATUS Filed April 21, 1924 Amplifier 2 Sheets-Sheet 2 E INVENTOR i Patented Aug. 14, 1928.

UNITED STATES i enema amuse V new roan.

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Application lilcd April er, 1924. Serial No. $027,863-

This invention relates to translating methtranslated. Also these prior art devices reods and apparatus, and particularly to methquire a fairly large number of parts, includods and apparatus for translating electrical ing one or more electromagnets having a undulations or impulses into corresponding large number of turns. 5 sound undulations or impulses. ln accordance with the foregoing and The general objects of the invention are other objects of the present invention these to provide a method of and to provide an difliculties of the prior art may be overcome apparatus for translating electrical undulaby modulating a superaudible frequency curtions directly into sound undulations. rent With the undulations to be translated 10 Another object of the invention is to proand passing this modulated current across a vide a translating device free of moving spark gap positioned in an air pocket which parts. may be in communication with the small end Other and important objects of the invenof a suitable horn or the like. Due to the tion are to provide a method of and to provariations in the dynamic action of the spark 15 vide an apparatus for subjecting air to the and the variations in the instantaneous rate action of electrical undulations to produce of heating of the air in the pocket, the colsound Waves corresponding to the electrical umn of air inclosed in the horn is set into undulations. corresponding vibration. If the carrier cur- Other objects of the invention are to prorent is unmodulated the only vibration pro- 20 vide a method of and to provide an appaduced is of superafidible frequency, and ratus for translating electrical undulations hence no sound is produced, i. e., the column into corresponding sound undulations by of air in the horn is vibrated at a frequency varying the intensity of an electrical diswhich is superaudible. However, when the charge in air in accordance with the electricarrier current is modulated with the audible 25 cal undulations. frequency undulations which are to be trans- Among the more specific objects of the lated into sound waves, the intensity of the invention are to provide a method of and spark is varied in accordance with these un to provide an apparatus for translating audulations and hence corresponding vibration dible frequency electrical undulations into of the air column enclosed by the horn is w corresponding sound undulations by moduproduced. ln other Words, the superaudible lating a superaudible frequency electric curfrequency vibration of the air column in the rent in accordance with the undulations to be horn is modulated at audible frequency thus translated, passing the modulated current producing a sound which corresponds to the across a spark gap, and subjecting the atmodulation.

35 mosphere to the efiect oi the variations in In order to keep the pocketed air at suitintensity of the superaudible frequency elecable temperature under continued operation trio spark. of the apparatus the wall surrounding the ln the prior art electrical undulations or air pocket may be made of a good heat conimpulses have generally been translated into ducting material, blackened and provided sound waves through the instrumentality of with suitable fins to increase radiation of mechanical moving arts such as a diaheat. The electrodes which form the spark phragln or the like w ich acts upon the atgap may be adjustable to vary the length mosphere and is electromagneticall vibratofthe spark, and preferably both electrodes ed in response to the electrical und ations to are adjustable so that the length of the spark 45 be translated. Withsuch devices it has been may be varied without shifting the position dificult to obtain accurate or undistorted of the center of the spark with respect to the translation on account of the inertia of the Walls of the air pocket. diaphragm and the fact that in most cases Figure .1 of the drawings shows a radio the diaphragm has a natural period or pereceiving circuit embodying the invention. 50 riods of vibration, all of which render it Figure 2 is a time diagram showing an ildificult if not impossible to make a dialustrative current wave delivered'by the dephragm move accuratel in accordance with tector of the circuit shown in Figure 1. 105 the variations in the electric current to be Figure 3 is a time diagram illustrating the carrier current of the sending or oscillating unit of the circuit shown in igure 1.

Figure 4 is a time diagram illustrating the current delivered to the translating device by the circuit shown in Figure 1.

Figure 5 is an alternative radio receivin circuit embodying the invention. a

Figure 6 is a fragmentary sectional view showmg the translating device.

Figure 7 is an elevational view showing the mounting of a horn embodying a translating device in accordance with the present invention.

It is realized that the present invention may be practiced in forms other than those herein illustrated and described, and hence it is desired that the present disclosure be considered as illustrative and not in the limiting sense.

- circuit 1 is arranged-to be excited by radio waves and to correspondingly energize an amplifying and detecting unit 2, which may be of any suitable and well known type. An oscillator or other-suitable continuous wave sending unit 3, which produces a carrier such as shown in Fig. 3, is connected in any suitable manner to be modulated by the current delivered by the amplifier-detector unit 2. As is well understood in the art the detector current has a wave form such as shown in Figure 2 and modulates the carrier of the sending unit 3, causing that unit to deliver a current of the form shown in Figure 4. The voltage at which the current is delivered by the sending unit 3 may he stepped up by means of a suitabletransformer 4, after which it is discharged across spark gap 5 positioned in air pocket 6. As shown by Figure 4 the amplitude of this current varies in accordance with the audible frequency undulations delivered by the amplifier detector unit, and hence the rate at which energy is liberated by the spark within the air pocket varies accordingly. The energy liberated at the spark gap is largely in the form of heat, resulting in expansion and contracting of the pocketed air in accordance with the form of the current shown in Figure 2. This action is probably aided by the variations in the dynamic action of the spark. The air pocket being in communication with the outer air, a sound is produced which'corresponds to the electrical undulations of Figure 2.

The sending unit 3 may be operated to generate a carrier current of any suitable superaudible frequency, and a frequency may be selected which permits the design of a high efficiency circuit, and the use of an iron core transformer at 4, if desired. If desired the secondary of transformer 4 may be tuned by closing switches 7 and 8, thus connecting it across variable condenser 9.

The apparatus is preferably operated so that the carrier of the unit3 is only partially modulated as shown in Figure 4, this insuring that the potential delivered to the spark gap will always be sufiicient to maintain the spark.

In the form of apparatus shown in Figure 5 an oscillatory circuit 10 is arranged to be excited by radio waves and to correspondingly energize an amplifier 11 of suitable type. The voltage at which the output of the amplifier is delivered may he stepped up by means of a suitable trans former 12, after which the current is passed between the electrodes of spark gap 13. If desired, switches 14 and 15 may be closed to permit the secondary of transformer 12 to be tuned by condenser 16. The heating and dynamic actions within the air pocket are independent of the direction in which the current flows between the electrodes of the spark gap 13, and hence no detector need be associated with the amplifier 11.

Referring to Figure 6, an air pocket denoted in general by 20 is formed by a spherical Wall 21 having integral heat radiating fins 22. The wall 21 and fins 22 may be made of suitable heat conducting material such as copper and may be blackened to increase the rate of radiation. Electrodes 23 and 24 are slidably mounted in insulating bushings 25 and 26 respectively, thereby forming an adjustable spark gap within the air pocket 20. In order to insure proper cooling of the electrodes, the bush- - ings 25 and 26 may be made of material which is a good heat conductor as well as an insulator. A horn 27 in communication with the. air pocket as shown, may be integral with the walls 21 and may be of any shape desirable from the standpoint of acoustical efficiency.

Referring to Figure 7, the horn 27 is supported by a base 28 which incloses the air pocket, but is provided with suitable apertures 29 to avoid interference with the radiation of heat from the air pocket. Suitable means such as binding posts 30 and 31 are provided for makin the necessary electrical connection to the e ectrodes of the spark gap.

From the foregoing description it is seen that a method and apparatus have been provided by which electrical undulations may be directly translated into corresponding sound waves, that diaphragms or other moving parts have been-completely eliminated, and that a translating device of exceedingly simple construction has been produced. It is also apparent that a method and apparatus have been provided whereby a. modulated superaudible frequency current may be translated into correspondmg sound waves without the necessity of rectification of the current before translation. -The invention has been disclosed as applied to radio receiving apparatus, but it will be apparent that it may be applied in many other connections where it is desired to translate electrical undulations into corresponding sound Waves.

Taving thus described my invention, what it claim is z-- l. The method of reproducing sound which comprises producing an electrical sparlr by a superaudible frequency current and modulating the spark current with an audible frequency current.

2. The method of reproducing sound which comprises forming'a series of sparks at superaudible frequency in air with a current modulated in accordance with the sound to be reproduced.

3. The method of producing sound which comprises subjecting pocketed air to the action of a continuous series of electrical sparhs modulated with an audible frequency current.

an The method of reproducing sod i which comprises subjecting poclreted air to the action of a continuous series oi electrical sparlrs and modulating the sparlr current with current corresponding to the sound to be reproduced,

5. The method or producing sound which comprises subjecting oclreted air to the action out a superaudi is frequency spark and modulating the spark current with an audible frequency current.=

d. The method of reproducing sound which comprises subjecting ocheted air to the action oi a superaudible equency sparlr and modulating-the spark current with current corresponding to the sound to be reproduced,

it The method of reproducing sound which comprises subjecting pocketed air to the action of a spark and modulating the spark in accordance with the sound tohe reproduced 8. The method of reproducing sound which comprises producing a spark with superaudible frequency current and modulating the superaudible frequency current with an electrical pulsation of an audible so rate.

9. The method of reproducing sound which comprises producing a spark with superaudible llrequency current andmodulatiug said current with detec radio signals,

ill. it sound reproducing system comprising a sparlr gap electrical means connected to said sparl: gap to produce a superaudible frequency spark, and means to modulate said spark an audible frequency current,

Jill. A sound reproducing system comprising a spark gap, a closure at least partially enclosing said sparlr gap, means connected said gap to produce superaudible lirequency sparlr, and means to modulate said sparlr with an audible frequency current.

1%.. ll. sound reproducing system oompris ing a sparh gap, electrical means connected dill ill

to said gap to produce a superaudible l'requency sparlr, and means to modulate said sparh with a Varying current corresponding to a somid to be reproduced iii. A sound reproducing system comprisinp; a spark gap, and electrical means con nected to said spark gap to produce a superaudible frequency sport: modulated at an audible rate. r

M. A sound reproducing system comprising means to establish a col ol air means to vibrate said col of air at a lli. 7 od SOlllld. whic comprises electrically producing directly in a r a superaudible frequency air vibration, and modulating the vibration at audible uenc freq y GEURGE SEY.

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