US2820526A - Sound producing system - Google Patents

Description

Jan. 2l, 1958 E.. A. TAvAREs SOUND PRODUCING SYSTEM' 2 sheets-sheet 1 INVENTOR. EQNEST A. TAVAQES Filed July 10, 1952 BYRuLH-orvlaowg,

AGENT Jan. 21, 1958 E, A. TAVARES 2,820,526

SOUND PRODUCING SYSTEM Filed July l0, 1952 V 2 Sheets-Sheet 2 III/ ill/llll lll/ EQNEST A. TAV/M2125 "BY ma. H-dw Y L6' AGENT IN VENT 0R.

United States Patent"v O SOUND PRODUCING SYSTEM Ernest A. Tavares, North Hollywood, Calif. Application July 10, 1952, Serial No, 298,107

14 Claims. (Cl. 181-31) marily described herein as a sound reproducing system of the type just mentioned because this is one of its principal uses. In this specific arrangement it relates, in particular, to a novel, small sound reproducing system adapted to greatly extend the low frequency range of useful acoustic energy radiated therefrom and available in an adjacent listening region.

It should be noted that this patent application is a continuation-in-part of my co-pending patent application entitled Novel, Small, Extended Low Frequency Response Loudspeaker Enclosure, Serial No. 163,994, tiled, May 24, 1950, subsequently granted July 19, 1955, as U. S. Patent No. 2,713,396, and my co-pending patent application entitled An Improved Small Extended-Low- Frequency-Response Loudspeaker Enclosure, Serial No. 280,903, tiled April 7, 1952, subsequently granted August 7, 1956, as U. S. Patent No. 2,757,751 (which explicitly and/ or implicitly disclose the inventive concepts, more specifically described, illustrated and claimed herein).

Generally speaking, the present invention comprises a sound producing and/ or reproducing system including a chamber (usually a closed chamber) having emission port means connecting the interior and the exterior of said chamber and having diaphragm means effectively, resiliently mounted in closely spaced position across the emission port means to effectively provide ow restricting, variable emission slit means. Said diaphragm means being effectively connected to and adapted to be vibratively driven by oscillatory motor means whereby to modulate air ilow through the slit means.

In one preferred general form of the present invention the chamber means may comprise pressure tank means adapted to contain air under pressure greater than that of ambient air on the other side of the emission port means whereby to cause air to ow outwardly through the slit means for modulation thereby.

In one preferred general form of the present invention, the diaphragm means (and associated variable slit means) may comprise air pump means adapted to electively pump air intermittently into the interior of the chamber and may also comprise modulating means adapted to modulate air intermittently flowing out of the chamber, in a manner corresponding tothe vibration f the oscillatory motor means.

FVice In another preferred general form of the present invention, auxiliary pressurizing means for pressurizing the interior of the chamber may be provided. In one form, this may comprise auxiliary port means connecting the interior and the exterior of the chamber and an auxiliary diaphragm means resiliently mounted in closely spaced position across the auxiliary port means so as to dene resiliently variable auxiliary slit means; said auxiliary diaphragm means having a substantially greater surface area than the area of the auxiliary port means immediately adjacent thereto whereby vibratory movement of the auxiliary diaphragm means toward and away from the auxiliary port means in response to vibration of the first diaphragm means, will tend to intermittently pump air into the chamber and increase the mean air pressure therein, thus altering the effective compliance of the air within the chamber and altering the variable ,p slit means in a manner increasing the effective air mass moved.

From the above general description of the basic and several preferred forms of the present invention, it will be apparent to those skilled in the art that virtually all 0f the hereinabove mentioned prior art disadvantages are virtually entirely eliminated and overcome in and through the use of the system of the present invention.

For example, in the basic form of the present invention wherein only one diaphragm is utilized, there is absolutely no problem of the prior art type involving cancellation of front and back radiation as a result of phase difference. Even in the other general forms of the present invention wherein one (or more) auxiliary diaphragm means is employed, there is little or no low frequency cancellation of front and back radiation as a result of phase difference, as occurs in prior art systems. In one form, this may be true because the auxiliary diaphragm (or diaphragms) may radiate very little sound. In other forms, this may be true because the coupling, comprising the compliance of the air mass in the chamber and the compliant auxiliary diaphragm means, and the alteration in the mass of the effectively moved air, are such as to cause back radiation and front radiation 'to reinforce each other, instead of cancelling out, to

produce a very strong low frequency acoustic output. And this in spite of the fact that the volume of air enclosed in the chamber may be very small and would ordinarily have a compliance such as to be incapable of producing the above mentioned resultsthe difference being produced by the compliantly mounted diaphragm means (and the variable slit means associated therewith), which greatly modify the effective compliance of the small volume of air enclosed within the chamber and the effective mass of the moved air.

In the basic form of the present invention, wherein a single vibratively driven diaphragm is employed in closely spaced position across (usually inside of) emission port means so as to define resiliently variable slit means, the diaphragm comprises an air pump means adapted to intermittently pump air into the chamber, thus increasing the pressure therein and altering the compliance of the air therein and altering the loading on the vibrating diaphragm and effectively altering the mass of air moved thereby in a manner such as to achieve high etliciency, low frequency generation of acoustic output.

The arrangement is such as to tend to eliminate harmonies, overtones and resonance of the chamber and vibrating elements.

The system of the present invention can be very small and yet have low frequency output characteristics as good as or better than a bass reiiex cabinet, which is a great deal larger. This is because the most critical factor in connection with a bass reex cabinet is the volume of air second, or-evenlo'wer in certain-cases. n dublicatedf by the customary priorS-artusystemsnn cabinets lowfrequeney range, andisr capable oftproducing yvirtuallypure fundamental tones Eas low -as thirtycycles per of anything like `a comparable-size.

y"Also, the present inventionlcan use `an oscillatory. motor ofany'desired type. If desired, itcancomprise an electromagnetic motori of :over-y .muchI ygreater efficiency.; andtef fective. power output than. standard .loudspeakerrrnotors vThisisIpo'ssible because f oflothern features of .the lsystem,

Lwhereas 1 it is .not possible :in :customary .loudspeaker f motorsV employed' to actuateithe .usua1:light,.v conical: loudspeaker diaphragm.

Also, `it should be noteduthatthe .usual limitingfactors -finconnection with sound'reproducing systems are-largely inoperative inconectionwithfat leastcertain forms of the present invention because sound is produced by modulating `air owing outwardly through :the variable 'slit emission lmeans, which isrentirelyflditferent:'from-:theymethodemployed -instandard loudspeakeruand/or Floudspeaker enclosure systems. A"Furthermore, thef-.slit source: of: sound .provides-a very effective. means for `disseminatingthe sound intola listening region 'defined byaflarge lsolidangle,

inamanner vastlysuperior tofy the best. thatycan` be attained in prior art systems.

It should alsobenoted that2thesy-stem ofthe present l invention lis not limited touse* as afsoundreproducer; but

.canbe employedI aswa primarygenerator of sound, which willvproduce acoustic output corresponding- ,tothe vibrav.tions lof the oscillatory motor means.

With the above! points. in mind,.;it is an object of the .present invention to provide anovelfsound` producing t (and/orsound reproducing) systemwluch can be made very small and which is capable of effectively radiating into a listening region substantial acoustic energy (usually, though not necessarily, in the low'frequency range) lm ya art sound reproducing systems.

Another object of the present invention is to provide a novel sound producing (and/or-sound reproducing) Sysu tem adapted to produce sound by modulatingyair flowing f through controllably variable .slit emission meansfwhereby to vproduce useful .acoustic output .power-.- ina vvery l eflicient manner.

.Other and allied-objects ywill be ,apparent `tothose yskilled in the art-after a carefulL perusal, examination and study of. thefaccompanying illustrations, the,v present speciflcation, and the appendedv claims.

To facilitate understanding, vreference will. be. made to the hereinbelow described, drawings, in which:

t Fig. 1- is assmall `perspective View yof .one/illustrative embodiment of the present invention.

Fig. 2 is a somewhatv larger vertical sectional View .taken -in the direction of` thearrows II--lIin Fig/3.

Fig. 3 isa lvertical sectional viewtaken inthe direction of the arrows III--IIIf vin Fig.. 2.

teriror .and exterior ioftsaid,V chamber. l Also,..ge,neraly speaking, diaphragm means is` electivelyrresiliently mounted in closely spaced Iposition across thetemissionl port means to eiectively .provide flow restricting. controllably `variable emission lslit means, and vis. effectively t connected This cannot be t manner as good las or better thanverylmuchlarger prior end rotture, voiceoilfcar to oscillatory motor means in driven relationship with respect thereto whereby .tobe vibratedthereby.

In the speciiic example Villustrated in Figs. 1, 2, 3, and 4, the chamber is deiined by a plurality of walls, including a front wall 1, a back wall 2, two side walls, 3 and 4, and a top and bottom wall, 5 and 6, all joined together in spaced relationship to form a small chamber, indicated generally at 7.

The front Wall 1 of the chamber 7 is provided with emission port `means-(in .thespecic--example illustrated, centrally locatedandA of circulan..Qntwardlyftlared shape) indicated at 8.

In the specifici example illustrated, the ztlow Vrestricting means comprises variableemissionslitmeans, indicated generally at 9 `defined by the positioning of a diaphragm 1t), which is illustrated as being circular and resiliently mounted by a plurality of circumferentially spaced fastening means 11, fastened at their outer ends to a plurality of circumferentially spaced Springmeans :112, which `are fastened. totheapertiphery lof ttheannulus 13 of thedivaphragm .110, at points spaced .around they :peripherythereof. lThex. .other:endsnofnthei` fastening `posts 11 are. .tixedly z-mountedtwithzrespectsto4 the annular.l rim portion .14 vof l arhousingcarryingfthel.oscillatory Amotor means, indicated ...generally .tat:.,15. .rltshouldizbefnoted that :the: fastening `ipoststll,.andtzthe1rimtportion `-14. of the housing '15.: are fastened'wtoeY ther-inside fofafthe .frontfwall 31 in. a-concentric positionfwith respect. tonthe'emission: portl means 8. `Any other desired type :off fastening.` meansmay bezemployed vto. resiliently :mount `the.A diaphragm. means 10 :with respect lto the.` front .-.wall:.1oftherchamber `7. It should .alsoazbe i noted-that 'the diaphragmzlis; mounted :by the; resilient means 12-. soethat the annular .outer portion 13 of 4,the diaphragm f1.0: is: positioned in vi-rtually parallel, closely spaced relationshipfzwi-th respect tov the. insidesolthe` vfront .Wall 1 immediatelyaround .they .emissionfport 8 therethrough, in a manner such that the a1111ular-portionf13 `ofthevdiaphragmglolles, closely adjacent to a correspondingl annularportionp the frontafwall-rl off `.the bemand -deines.the resiliently vvariable` emission slit meansy 9.

vln ,the specific example illustrated, the oscillatory-.motor meansrlS-.inludesfa permanentvmagnet central .portion .-16 y.and abmovable, fhollow, tubular `voice-coil-carrying member 1 317.,positioned` thereon for lateral sliding: movement-,with respect. thereto. .Thefvoicefcoil-carrying member `1f` carries` =a voice` `coil 181=thereon and ismountedfby aresilient spider:1,9 ,j inthe` customary manner. The :left ying tube 1 7` is provided `witha ycirculan..diss member-:20 (which may Lohmar-.net .be centrally apertured as indicated at 21) which carriesfat lcircumferential.spaced` points larouud the periphery. thereof yspacers .22 effectively connecting .the disc .2,0.to the annular portion 13. of4 the diaphragm, 10,- whereby vibra tory movement yof the yoice-coil-carrying member 17vyill effectively vibratesaid .annular portion 13 `of-therii- .aphragm 1,0 toward-.and away from .the corresponding portion of `thefinside of .therfr'ont wall 1.

The. arrangementis such that lateral vibratoryoscill-ation .of the diaphragmlt), .tends tomovethe annulagportion 13 of thediaphragm 1,0 .towardand away,from. the adjacent annular. portion ofthe vfront wall 1 in.y amanner such .as totend to alterthe variable ,slit 4emission means 9 (and to thus altertheeifectiveair massmoved), and to intermittently pump air intolthe chamber 7 through the slitmeans 9,between,thefronnsurface of the annular ring 13 and `,the inside surface vofthe adjacent annular portion of the frontwalll, and suchlhat vibrators/oscillatory movementA of .the. annular ring` 13,v toward the extreme left, as viewed in.Fig..,2, t.ends .tofavlmostvtor-.in some casesv completely) .mqmentarilyfsealthe port land lrlinimize torfpartially werent) `titer-@SQare .-.Qf @intiem within the .chamber 7ltoamhientatmosphere. Thisftends Ato produce. apressure increaselwthinllthe chamber?,

which will ,intermittently leakbackwardly through 5;.tl1e variable slit emission means 9` and .bennodnlateggby yibta,

tory movement of the diaphragm ring 13 so as vto produce sound in an extremely efiicient manner, generally akin to that employed in a vibrating reed type of sound producer, or the like and to effectivelyl radiate the same into a large solid angle by reason of the slit source of sound.

It should also be noted that the pressure increase in the chamber 7 tends to effectively alter the variable slit emission means 9, thus effectively altering the mass of moved air in a manner tending to lower the resonant frequency of the chamber.

It should also be noted that the air pressure increase (and/or density and/or compliance change) and/or the compliance of the resilient diaphragm and/or the spring coupling thereof to the front wall of the chamber 7 are such as to alter the effective compliance against which the diaphragm 10 works. This, plus the effective alteration of the air mass moved, effectively lower the resonant frequency of the system and greatly increase the useful acoustic output in a selected low frequency range.

In the specific example illustrated in Figs. l, 2, 3, and 4, the diaphragm 10 is also provided with a central discshaped portion 23, effectively connected to the outer annular ring 13 by annular corrugations 24, which are intended to compliantly couple the outer annular ring 13 to the central disc portion 23. The central disc portion 23 may be provided with suitable weight means 25, which may be fastened by any desired type of fastening means, such as indicated at 26, to the disc 23, and which may be removable for replacement by a greater or lesser weight for modification and adjustment of the low frequency response characteristic of the system. The central disc prtion 23 and the outer annular ring 13 are connected by the flexible corrugations 24 for the purpose of reducing the resonant frequency of the diaphragm k10 and the weight carried thereby, since the effective low frequency limit which can be radiated into listening regions is effectively controlled (to a certain extent in some forms of the invention) by the reasonant frequency of the diaphragm as well as the oscillatory motor means. The corrugations 24 also act to isolate, to a desired degree, the actions of the outer ring 13 and the inner disc 23.

It should be noted that either the annular ring 13 or the adjacent annular portion of the front wall may be provided with suitable resilient means in order to prevent any spurious and extraneous noise from being produced, in the event that vibratory movement of the annular ring 13 toward the left causes it to actually make engagement with the adjacent annular portion of the front wall 1.

rihe spring means 12 may be positionally adjustable so that the spacing between the annular ring 13 and the adjacent annular portion of the front wall 1 can be adjusted at will, so that, at maximum excursion of the annular ring 13 contact of the ring 13 and the wall 1 does not quite take place.

ln another general form of the present invention, I contemplate arranging the spacing between the annular ring 13 and the adjacent annular portion of the front wall 1 so that outward movement of the ring 13 effectively closes the port 8 during the earlier portion of the outward stroke and tends to produce a more effective air pumping action into the chamber 7. In this form of the invention, it is desirable that the annular ring 13 and the closely adjacent portion of the rear surface of the front wall 1 be resiliently cooperable when they abut. This may be provided by making either of the abutting portions resilient, or the equivalent.

It should be noted that the use of the terms front and back or-rear, as used in connection with the above descripiton, are not to be taken in a limiting sense. The system can be positionally reversed or otherwise repositioned. i

The modified form of the present invention, shown in Figs. and 6, is generally similar to the first form of the present invention in many respects except that the front diaphragm is modified somewhat so as to act entirely as a modulator of outfiowing air, and except that an additional port, resiliently mounted diaphragm and variable slit means are provided to act as an auxiliary pressurizing means to increase air pressure within the chamber. In this version of the invention, similar parts will be indicated by similar reference numerals, primed however.

In this modification, the front diaphragm 10 no longer has corrugations, such as the corrugations 24 in the first form of the present invention, or a central disc portion, such as the disc portion 23 in the tirst form of the present invention, or a central weight, such as the weight 25 in the first form of the present invention. The hole 21 is also eliminated, and the annular ring 13 is driven by means of the oscillatory motor means 15 so as to merely modulate air fiowing outwardly through the variable emission slit means 9 so as to produce sound by said modulatory action in a very efficient manner adapted to radiate into a listening region defined by a very large solid angle. As illustrated, the spacer means 22 comprises a sealed ring instead of spaced posts.

In this modification, the back wall 2' of the chamber 7 is provided with auxiliary port means (in the specific example illustrated, centrally located and of circular, outwardly-flared shape) indicated at 27. In the specific example illustrated, variable slit means, indicated generally at 28, is defined by the positioning of an auxiliary diaphragm 29, which is illustrated as being circular and resiliently mounted by an inner mounting ring 30 fastened by fastening means 31 to the annulus 32; said mounting ring 30 being also fastened to spring means 33 spaced around the periphery thereof, the other ends of which are fastened to an outer mounting ring 34, which is fastended with respect to the inside of the back wall 2 by fastening means, such as the screw means 35. Any other desired type of fastening means may be employed to resiliently mount the diaphragm means 29 with respect to the back wall 2 of the chamber 7. It should be noted that the auxiliary diaphragm 29 is mounted by the resilient means 33 so that an outer annular portion 32 of the diaphragm 29 is positioned in virtually parallel closely spaced relationship with respect to the inside of the back wall 2 around the port 27 therethrough in a manner such that the annular portion 32 of the diaphragm 29 lies closely adjacent to a corresponding portion of the back wall 2 of the box.

The arrangement is such that lateral vibratory oscillation of the diaphragm 29, which occurs as a result of back acoustic radiation from the front diaphragm annular ring 13', in a selected low frequency range, tends to move the annular portion 32 of the rear diaphragm 29 toward and away from the adjacent annular portion of the back wall 2, in a manner which tends to alter the variable air slit 28 (and to thus alter the effective air mass moved) and to pump air into the chamber 7' through the slit means 28, and such that vibratory oscillatory movement of the annular ring 32 toward the extreme right, as viewed in Fig. 5, tends to almost (or in some cases, completely) seal the port 27 and minimize (or prevent) the escape of air from within the enclosure 7 to ambient atmosphere. This tends to produce a pressure increase within the chamber 7 whenever the oscillatory motor means 15 is vibrating in a selected low frequency range. This pressure increase eectively converts the chamber 7 into a pressure tank and causes air to flow outwardly through the front variable slit means 9 and to be modulated by the Vibration of the front diaphragm ring portion 13', as it passes through said slit means.

In certain forms of the present invention, the rear diaphragm 29 may also be adapted to radiate sound, which will be in an additive relationship with respect to sound radiated from the front of the system.

It should be noted that the pressure increase in the chamber 7 tends to effectively alter the variable slit means 28 (while at the same time altering the variable 7 sltmeans 9.?) thueeleetively altering the mass. of moved air .of a marmer tending tolower the resonant frequency .ofthe-chamber.

The, air. pressure .increase (and/or density and/or compliancechtlnge) and/.orithe complianceof the resilient diaphragm 29 and/or the spring coupling thereof to thebacl; wall 2 of the chamber 7', is such as to alter theetfective compliance against which the front. ring 13 works in rearward oscillatory movement in a selected low frequency rangee Thiseifectively lowers the. resonamffrequeney ofthe system and'sreatly increases the usetulacoustie output in a selected low frequency range.

In. the Specific example illustrated in Figs.` 5 and 6.,.the diaphragm Z9fis alsoprovided w-ithsacentral discishaued portion 36, effectively connected-.to the outer annular ring 32 by annularrcorrugations 3,1,.which are. intended tocompliant-ly couple.: the outer annular ring portion 32 to the-'central disc portion136.

In thespecific exampledllustratedin Eigs. 5 and 6, the central disc portion36 is.provided;withfsuitable` weight means 38, which may. be fastened by any desired type. of fastening-means, suchtas indicated at 39, to the disc.36, and/which t may be removable'. for replacement by a greater or lesser weight-for modification of. the response characteristics of the system. The central disc portion 36; and the outer annular ring. 32:` are connected. by the flexiblecorrugations.37 for theypurpose of reducing the resonant frequency'of1-the diaphragm-29 (and the weight carried thereby), since-theeifective lowl frequency limit which can-be radiated.v into-a klisteningfreg-ion (in at least certain `forms ofthe invention) `can-tbe :efeotively'altered by cont-rolling the resonant frequenciesof either or both ofthediaphragms (as well as certain other variables). Thecorrugations 37 also act to'eifeetivcly isolate thecentral disc portion 36 and the outer'annular portion 32- (to anydesired degree).

In certain forms of the present invention, the central -disc portion 36l of the diaphragm 29 may act as a very efficient acoustic radiator for radiating lowfrequency energy outwardly through the port 27 (and this in addition to the modulatory actionof the outer annular por tion).`

It should be ,noted` that either the annular4 portion 32 or the adjacent annular portion of the back wall 2l may be suitably maderesilient in order to prevent any spurious and extraneous noise from beingiproduced, in the event that vibratory movement of the annular ring 32, toward the right `as viewed ,in Fig. 5, causesit to` actually make engagement withv the adjacent annular portion ofthe back wall' 2.

The Vspring means 33 may be positionally adjustable so that the spacing between the annular ring 32 and the ad* jacent annular portion of the back wall 2 can be adjusted' at will, so that, at maximum excursion ofthe annular ring 32, contact of said ring and the wall 2' does not quite take` place.

In another general form of thev present invention, l contemplate arranging the spacing between the annular ring 32 and the, adjacent annular portion of the back Wall 2' so that outward movement of the ring 32 effectively closes the port 27 during the .earlier portion ofthe outward` stroke and thus produces a more effective air pumping action into the chamber 7'. This form of the invention requires they use of resilient means positioned between the annular ring 32 and the rear wall 2' or requires that said wall 'or said ring be of resilient construction at the contacting surface.

It shouldbe noted that the use of the terms front and back or rear, as used in connection with the above description ,arev not to be` taken inl a limiting sense.

It should alsobe notedthat the present invention is not limited tothe arrangement shown in Figs. l through 4, inclusive,w or the arrangement shown in Figs. 5 and 6. Anysourceof air under pressure may be employed. This 8 mghtinelude a pressurevessel containing air under pressure, or any.suitablepressurizing means..adapted to .pressnrize theiinterior` ofthechamber and to allowv outflow throughthe variable' emission slit` meanspast the; vibrating diaphragm for modulation thereby.

Numerousv modifications, and variationsof the present invention willtoccur tothose skilled inthe art after a careful study hereof. All such properly within the spirit and scope. of thepresent invention are intended to be included and comprehended as fully as if specically described, illustrated,v and.` claimed4 herein.

For example, the shape and configuration of the chamber4 is not limitedto theforms illustrated herein, but may assume, a `great variety of forms and may be of integral or non-integral construction,y and may be made of any desired materials.

Either or both ofthediaphragm means and/or port means and/.or variable.. slit means need not be positioned in any particular wall or walls of the system, but can be positioned in a. great variety of relationships. The structure, arrangement and composition of either or both of the diaphragm means, and/or port means and/or slit means. and! or means for mounting the diaphragm means can be modified substantially from that described and illustratediherein..

The oscillatory motor means can be modified substantially, and may comprise any arrangement capable of driving a diaphragm-means.

Either or both of ther diaphragm sans need not be positionedon al certain specified side of a wall but may be located `in. any'selected position Withrespect thereto. Either or bothl of the, diaphragm means may be compliantly coupled withrespecteto the chamber or may be inherently compliant, or may. berelat-ively stiff and be providedwith compliant coupling-means so as to have piston-like.. action. Either or.. bothy ofV the. diaphragms may have. several relatively` stiff portionsgconnected by flexible portions. therebetweemif desired, or they may` be provided withweight means (which may be. adjustable,` if desired)y in. order to alter theeffective resonant frequencies thereof. Either or both., may be arranged so as to not effectively close the associated port but to merely oscillate or vibrate in spaced relationship with respect thereto. If desired, either or both of the diaphragms may be arranged to have two (or more) portions connected by relatively flexible portions in a manner such that the resonant frequency of one. of. said portions is different from the resonant frequency of the other of said portions, to facilitate the operation of the system. In certain cases, the compliant. diaphragm means may not be positioned; between the interior of the chamber and ambientatmosphere but may be effectively positioned within, the chamber in. a mann-er whereby to produce. the hereinbefore. mentioned.. advantageous features.

The embodiments ofthe present invention specifically described,.illustrated and claimed herein are exemplary only, and are vnotintended tolimit the scope of the present invention, which is `to. be interpreted in the light of the prior art` and the.. appendedv claims only, with due considerationl forl thev doctrine of. equivalents.

I claim:V

LA.. sound producingV system, comprising: a closed chamber; `emission port means; connecting the interior andV the` exterior ofv said chamber; oscillatory-motordriven substantially planar diaphragm means eiectively resiliently mounted in closed spaced substantially parallel position across the emission port means and effectively defining annular substantially paralleledged ow restricting, variable emission slit means communicating the interior of said chamber with said emission port means, said' diaphragm means being cooperable to be directly vibrated byoscillatoryl motor means whereby to modulate air ow through the slit means.

2; A system of the character defined in claim 1 wherein the diaphragm means' comprises pump means and has a substantially greater substantially planar surface area than the area of the emission port means immediately adjacent and substantially parallel thereto, whereby vibratory movement of the diaphragm means toward and away from the emission port means, will tend to intermittently pump air into the chamber and increase the mean air pressure therein, thus intermittently causing air outflow through the annular variable slit emission means, and altering the effective compliance of the air within the chamber and altering the variable slit emission means in a manner increasing the effective air mass moved.

3. A sound producing system, comprising: a closed chamber; emission port means connecting the interior and the exterior of said chamber; oscillatory-motor-driven substantially planar diaphragm means effectively resiliently mounted in closely spaced substantially parallel position across the emission port means and effectively defining annular substantially parallel-edged flow restricting variable emission slit means communicating the in terior of said chamber with said emission port means, said diaphragm means being cooperable to be effectively vibrated by oscillatory motor means whereby to modulate air ow through the slit means; said closed chamber comprising pressure tank means cooperable to contain air under pressure greater than that of ambient air on the other side of the emission port means whereby to cause air to ow outwardly through the slit means.

4. A system of the character defined in claim 2 including weight means carried by the diaphragm means for causing said diaphragm means to have the proper resonant frequency.

5. A system of the character defined in claim 4, where in the diaphragm means includes a central disc-shaped portion and an outer annulus resiliently joined together.

6. A system of the character defined in claim 5, where in the outer annulus is resiliently mounted with respect to the interior of the emission port means and wherein the central disc-shaped portion of the diaphragm means carries the weight means for adjusting the resonant frequency.

7. A system of the character defined in claim 6, Wherein the diaphragm means and the variable slit emission means comprise air pump means adapted to effectively pump air intermittently into the interior of the chamber and also comprise modulating means adapted to modulate air intermittently owing out of the chamber in a manner corresponding to the vibration of the diaphragm means.

8. A system of the character dened in claim 3 including pressurizing means for pressurizing the interior of the chamber.

9. A system of the character defined in claim 8, wherein the pressurizing means comprises an auxiliary port means connecting the interior and the exterior of the chamber and an auxiliary diaphragm pump means resiliently mounted in closely spaced position across the auxiliary port means.

10. A system of the character defined in claim 9, wherein the auxiliary diaphragm pump means is so spaced with respect to the auxiliary port means as to detine resiliently variable auxiliary slit means.

11. A system of the character defined in claim 10, wherein the auxiliary diaphragm pump means has a substantially greater surface area than the area of the auxiliary port means immediately adjacent thereto whereby vibratory movement of the auxiliary diaphragm means toward and away from the auxiliary port means in response to vibration of the first diaphragm means, will tend to intermittently pump air into the chamber and increase the mean air pressure therein, thus altering the effective compliance of the air within the chamber and altering the variable slit means in a manner increasing the effective air mass moved.

l2. A system of the character defined in claim l1, including weight means carried by the auxiliary diaphragm means for causing said diaphragm means to have the proper resonant frequency.

13. A system of the character defined in claim 12,

wherein the auxiliary diaphragm means includes a central disc-shaped portion and an outer annulus resiliently joined together.

14. A system of the character defined in claim 13, wherein the outer annulus is resiliently mounted with respect to the interior of the auxiliary port means and wherein the central disc-shaped portion of the auxiliary diaphragm means carries the weight means for adjusting the resonant frequency.

References Cited in the le of this patent UNITED STATES PATENTS 1,967,223 Bostwick July 24, 1934 1,997,790 Heidrich Apr. 16, 1935 2,121,008 Bilhuber June 21, 1938 2,295,483 Knowles Sept. 8, 1942 2,713,396 Tavares July 19, 1955

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