US1845733A - Acoustic device - Google Patents

Description

ACOUSTIC DEVICE Filed M z ay 15, 1925 4 Sheets-Sheet l Feb. 16, 1932. c, WARNER 1,845,733

. ACOUSTIC DEVICE Filed May 15, 1925 4 Sheets-Sheet 2 55 his fltto'm qs I Feb. 16, 1932. W RNER 1,345,733

ACOUSTIC DEVICE Filed May 15, 1925 4 SheetsSheet 3 Feb. 16, 1932. c WARNER 7 1,845,733

ACOUSTIC DEVICE Filed May 15. 1925 4 Sheets-Sheet 4 awumtoz 67/6 /7155 /Y "WK/V57.

a hi awn/nu s UNITED STATES PATENT OFFICE CHARLES N. WARNER, O]? miw YORK, N. Y.

ACOUSTIC DEVICE Application filed Kay 15, 1925. Serial No. 30,415.

This invention relates to acoustic apparatus such as to recording devices recording and reproducing sound boxes of talking machines, to telephone receivers and transmitters and other devices in which a diaphragm or a flexing element is utilized and which is responsive to or sets up sound Waves and is a continuation in part of my copending application Serial No. 738,155, filed September 8, 1924. The invention is particularly valuable in connection with telephone receivers of the type popularly known as loud speaking telephone instruments which are widely employed in connect-ion with radio sets. -This inventionrelates particularly to an improved diaphragm for use in such instruments and also to an improved generating system in conjunction therewith.

Faulty reproduction is traceable almost wholly to acoustical, not electrical, causes,

' these being due to the inherent shortcomings of the diaphragms, cones, etc., and their associated driving mechanisms used to trans late electric impulses into sound waves. It is the limited capacity of the diaphragm to generate overtones which prohibits its use as a vibratory factor in original musical instruments, and it is this same overtonal inadequacy which renders it incapable under forced vibration to res ond' fully and perfectly to the entire complex range of incoming electrical impulses that correspond to the original overtones. By employing the most perfect vibratory system ever deviseda two point suspended and tensed elementto take up and vibrate to the electric impulses'and thus repeat the sound waves emanatin from the original instrument, and by usingin conjunction therewith a liquid seal diaphragm to act as the resonator to amplify the vibrations thus generated (the only resonator ever invented which will notefi'ect an unnatural dissipation of the overtones given off by the generator)-by using this the most perfect of all vibratory systems this device embodies principles so fundamental that without them perfect reproduction will forever remain impossible.

An object of the invention is to provide an improved'acoustic device which, when utilized for the reproduction of sound waves, will produce such sound waves with a better balancing of the diflerent parts or components, such as, for example, the different voices or instruments making up a rendition; and which will produce sound waves of purer, clearer and more natural tone and quality; and with which these qualities may be varied at will to some extent.

A further object is to provide an improved acoustic device with which' sympathetic vibrat-ions of the parts thereof will be substantially or entirely eliminated; and with which less distortion of the reproduced sound waves will be obtained and fewer sounds foreign to the desired reproduction created. A further object is to provide an improved acoustic device which may be given different characteristics to suit the different effects desired; and with which the reproduction of sound waves will be free from various extraneous noises and distortion, particularly those noises in radio loud speakers, which are commonly ascribed to so-called static.

A further object is to rovide a sound box and a diaphragm'there or which is readily adaptable for use in conjunction with talking machines, loud speakers, microphones, and the like, which is durable, non-resonant, not affected by atmospheric changes; that will improve the quality of tone emitted or transmitted or recorded and will also reproduce and transmit with increased volume lower tones than have heretofore been possible.

A further object is to provide sound-functioning apparatus in which the generating or flexing element is separate from the resonating member or diaphragm, not only to render possible the use of diaphragms of difi'erent sizes, but also and in particular to permit the embodiment of a vibratory means for performing the eriodic motion in a manner analogous to tiat performed b the string the vibratory means employe in the finest musical instruments, and which alone is susceptible of infinitely varied complex harmonic vibration.

A further object of m invention is to provide a sound box for te ephone receiving instruments in which the diaphragm, the generating and voicing element, and the armature are three separate parts.

Magnetic materials suitable for diaphragms such as are generally used are relatively heavy; heretofore it has been necessary to make a sacrifice in lightness of diaphragm, which would produce the best acoustic efficiency, in favor of magnetic qualities. With this improved construction the armature can be made of good magnetic material and of suificient thickness to readily conduct steady and alternating fluxes from one core to the other in abipolar receiver, thereby giving the best efliciency of the oscillatory force per unit of electric energy received. The generatin or voicing element consists of a strip of exible material rigidly supported at its two ends at opposite points of the rim of the casing and connecting means of tensing; this generatin element serves two purposes: first, it holds the diaphragm or vibratory reproducing element and armature in the correct operative positions; and secondly, by its proper proportions in conjunction with a variable means of tensing thereby afiords a practical means to approximate the correct acoustical properties entirely independent of the size of the diaphragm.

Another object is the elimination of sympathetic vibrations in acoustic apparatus, and the revention thereby of extraneous noises and distortion, one of the chief causes of which is the restriction of the periphery of the diaphragm. This distortion is most noticeable when strong signals are being received.

A further object of this invention is the practical elimination of the audible reproduction of static. 1

Among the features of the invention are, first: the employment of a diaphragm of a new type-one that does not flex at anypoint within its planethe vibrations being conveyed to it by an attached auxiliary twopoint suspended and tensed generating element, preferably thin, and under a variable tension and means to ap ly said tension at either end. This means flor tensing the generating element is also utilized to properly center the diaphragm in a correct 0 erative position. The diaphragm is provi ed with a flange which sets in a well in the casing and in the devices which permit the diaphragm to be operated in a horizontal position, in which an inelastic fluid, suchas water, very thin oil, or any other substance in that state in which the particles move fieely among themselves, remain in one mass, and always take the form of the'containing vessel, is used as a sealing means for separating the front from the back sound waves because of offering practically no resistance to the diaphragms movements, this kind of substance afiording also an excellent damping agent. In such a diaphragm mounting-with the pulse has a tendency to cause the diaphragm to execute a series of vibrations. This diaphragm is, therefore, practically non-resonant, which is important, because, if it is elastic and resonant it stores up energy when forcibly flexed to either side of its medial line, and when released would vibrate in accordance with its fundamental tone thereby being detrimental to the faithful reproduction of speech and music. With this construction of diaphragm the air displacement is the same over its entire surface, with the result that the overtones are more faithfully reproduced.

In those devices to be used on phonographs where the diaphragm has to be operated when in a vertical position, vaseline and like substances having suflicient surface tension and adhesive qualities which serves to hold them in place without the necessity of a containing means, is used. v

The invention also contemplates various other features which will appear from the following description of various embodiments of the invention.

In the accompanying drawings Fig. 1 is an elevation of a radio loud speak-' er and telephone receiver constructed in accordance with the invention;

Fig. 2 is a sectional elevation through the re 'roducing unit of the same;

ig. '3 is a plan of one section of the unit, the other section being removed;

Figs. 4 to 7 are modified forms of flexing element;

1'1 8 is a sectional elevation through a soun box also constructed in accordance with the invention and of the typeparticularly adapted for use with talking machines;

Fig. 9 is a plan of the same;

Fig. 10 is a plan of a similar unit with a magnetic armature provided directly upon the tensioned flexing member;

Fig. 11 is a sectional elevation of the same;

Fi 12 is a plan of a. tensioned flexing mem er which may be employed in thedevice of Figs. 8 and 9 or 10 and 11;

Fig. 13 is a plan of another unit also constructed in accordance with the invention and in which the bridge member is magnetically actuated; and

Fig. 14 is a sectional elevation of the same.

Referring first to the embodiment of the strum ent.

The casing is mounted by the boss 2 upon a cabinet 3, which serves as a base for the in- The cabinet 3 has a sound conduit 4 which communicates with the smaller end of an upright horn 5 of any suitable construction, so that sound waves set up by the receiving mechanism within the casing 1, will be conducted to the horn 5, amplified thereby, and discharged into the room. hen the sound producing mechanism within the easing 1 is of the telephone receiver type, the,

instrument is popularly known as a loud speaking receiver.

The casing 1 is made of two sections 6 and 7, the lower section 7 being shown in Fig. 3. The tubular boss 2 extends from the end wall of the lower section 7. The two sections are normally secured together in any suitable manner, such as by screws or bolts, but may be separated to permit access to the mechanism within the same.

A flexible strip 8 of spring material, such as spring metal, or any other suitable flexible material, is formed in any suitable manner, in this instance being of the shape shown in Fig. 4. The ends of the bridge member are connected by screws 9 to the ends of pins or rods 10 which extend through slidable bushings 11 in the lower section 7 of the casing, the projecting end of each pin or red being threaded and carrying a nut 12 which abuts against the outer face of the casing. The bushings 11 may be held against sliding movement in the casing in any suitable man ner such as by set screws 11a carried by the casing and engaging opposite sides of each sleeve. Thus by rotation of either or both of the nuts 12, a tension may be produced upon the bridge member 8 within the plane of the latter, the degree of tension of which is variable depending upon the extent of rotation of the nuts 12. The flexing bridge member 8 is provided with a central aperture 13 through which a screw, bolt, or rivet 14 may pass, the latter also passing through an armature disc 15 and a diaphragm 16,

which may be disposed respectively upon 0pposite faces of t e tensioned flexin member. W'ashers 17 may be disposed between the bridge member and the armature and diaphragm so as to space the same. Suitable electromagnetic actuating devices 18 may be mounted in the upper section 6 of the casing, with the magnet polar ends 19 projecting into proximity to the armature 15 so as to insure a. magnetic pull thereon, depending upon thedegree of permanent magnetism in the electroma netic device 18. The diaphragm is preferab y disposed upon the side of the flexing bridge member toward a flat wall of the lower casing section 7, but slightly spaced therefrom, so that there will be a thin layer of air in the space between the diaphragm and the said end wall of the lower section 7 of the casing.

The diaphragm may be made of any suitable material, and for this purpose among the metals I have found aluminum to be very satisfactory, since it has the advantage of both relative lightness and rigidity. Heretofore aluminum has been unsatisfactory for diaphragms because it did not have suflicient elasticity, and when flexed and vibrated as usual heretofore it produced very flat hollow and unsatisfactory sounds, instead of the full round resonant tones which are usually sought. In accordance with this construc tion, however, aluminum is advantageous since because of its lightness,-it will have little inertia, and because of its largely pistonlike action it is not open to the objection which has heretofore existed.

The diaphragm may also be made of paper, bakelitc, or other suitable material, and is preferably coated with a very viscous semiliquid material of great internal friction or viscosity, which renders it practically incapable of sympathetic vibration.

The end wall of the lower section 7 of the casing is provided with an annular channel or well 20, which receives a quantity of a substance 21 in that state in which the particles move freely among themselves, remain in one mass, and always take the form of the containing vessel such as very thin oil, water, and like substances having these same characteristics. The diaphra 'm is provided with an angular peripheral flange 22 which extends part way into the well or channel 20 and into this inelastic fluid substance 21. This substance 21 serves as an airtight closure for the periphery of the diaphragm,

without materially restricting the movements of the diaphragm with the brid e. This substance also acts as a very slig tly resistant seal for the flange of the diaphragm.

When an undulating current passes through the electromagnets of the device 18, a variable magnetic pull will be created upon the armature 15, and this pull will cause a concomitant vibration of the tensioned flexing member, having a frequency in character tially pure condensations and rarefactions,

and will be free of the distortions usually caused when a diaphragm is restrained at its periphery and flexed conically as heretofore. By adjusting the nuts 12, the tension in the flexing bridge member 8 may be varied to some extent, and I have found that by the variations in the tension of the same, the characteristics of the reproduction may be varied to a considerable extent.

By providing the fluid seal for the periphery of the diaphragm, the maximum loudness is obtained for the sound waves created by minor vibrations of the diaphragm, as this v fluid seal oflers very little resistance to the ment. The thin layer of air between the diaperipheral portion of the dia hragm, and therefore is conducive to its free om of movephragm and wall of the casing serves as'a cushion for the diaphragm movements which will prevent blasting when the vibration rate becomes very high. The sound waves set up by the dia hragm are conducted through the tubular oss 2, through the conduit 4 of the base 3, and thence into the horn '5 where they are amplified and discharged into the room.

In Fig. 5 a flexing member 8a is illustrated, which is provided with substantially circular center portion and tongue-like extensions on diametrically opposite sides, and which may be tensioned by the tensioning means shown in Figs. 1 and 2.

In Fig. 6 a somewhat similar flexing member 86 is illustrated, having four extensions by which it may be tensioned by the devices shown in Figs. 2 and 3.

.In Fig. 7 a circular flexing member 80 is illustrated, having three extensions by which it may be tensioned, the tensioning extensions being disposed at 120 degrees apart around the periphery of the same.

In Figs. 8 and 9 another embodiment of the invention is illustrated, the application of the invention to a talking machine sound box being particularly illustrated. In this embodiment of the invention the sound box 23 is provided with a sound wave exit passage 24 leading from a wall thereof, and also is provided with an annular well or channel 25 receiving a viscous sealing substance having a surface tension and adhesive qualities sufficient that it be retained in well 25 when the diaphragm is in an operative vertical position.

The flexing bridge member 27, similar to the member 8 of Figs. 1 to 3, is anchored at one end to the casing in any suitable manner, such as by a screw 28 and an abutment block 29.- The flexing member passes through aslot 30 ot'the casingand through a slot in the abutment member 29. The screw 28 passes through a portion of the casing, through an aperture in the end of the bridge member 27 which is within the abutment member, and is in threaded engagement with the abutment member. The abutment member engages the periphery of the casing and thus serves to anchor that end of the bridge -,member against endwise movement.

The other end of the flexing member is connected by a screw 31 and a washer 32 to I a block 33, which is slidable radially in the toan extent depending upon the extent of desired.

A diaphragm 35 is secured, at an interior point such as at the center, by a screw 36 and spacer washer 37 to a point of the flexing member between the ends of the latter, that is at a point in its span. Preferably the connection between the diaphragm and the flexing member is made at a point between the center of the span of the flexing member and one of its ends, that is, not at the center of the span of the flexing member. In stringed instruments, the string is never stroked at its exact central point and I have found that better results are obtained when the connection between the diaphragm and the flexing member is similarly made, that is, at one side of the center of the span.

The diaphragm may be of any suitable material and corresponds to diaphragm ,16 of Figs. 1' to 4. The diaphragm is spaced slightly from that'wall of the sound box having the sound wave exit opening 24, and may have an annular angular flange 38 which enters the well or channel 25 and engages with the sealing substance 26 thereof as in the preceding embodiment.

W hen the sound box is used for recording or transmitting purposes, the transmitter button or recording stylus is connected either directly or through leverage or linkage to the flexing member, preferably to the same point of connection as that to the diaphragm. In Figs. 8 and 9, however, the flexing member is arranged for actuation by a lever 39 which is mounted for rocking movement on suitable adj ustable pivots 40 of the casing. This lever either carries an armature by which it may be magnetically actuated, or a recording'stylus 41 which is vibrated when it runs in sound grooves, as well known in talking machines.

The flexing bridge member 27 is preferably enlarged and formed in the shape shown in Fig. 9 for the reason that such a shape has been found to give excellent results, but it will be understood, of course, that the flexmg member may be made of other shapes or arranged to be tensioned at different points as has been explained, for example, in connection with Figs. G and 7. The flexing member may be made of any suitable spring or.

any other flexible material, the same as the flexible bridge member 8 of Figs. 1 to 4.

Referring particularly to Figs. 10 to 12 I have illustrated a similar form of sound box, in which the diaphragm and flexing member are intended for electromagnetic actuation, the tensioning means for the bridge member being also slightly modified. In this embodiment of the invention, the sound box 42 has the sound wave exit opening 43 as in F igs. 8 and 9. The flexing member 27, corresponding to the bridge member with the same reference numeral in Figs. 8 and 9, passes through a slot. in the sound box wall, and through a slot 44 in an abutment member 45 which engages with the periphery of the sound box. 4

A locking pin 46 passes through an aperture 47 in the projecting end of the flexing member, so that when the flexing member is tensioned, it will draw the pin 46 against the abutment member 45 and the latter against the periphery of the sound box. The other end of the flexing member is connected, by a screw 47 and-washer 48, to one end of a rod 49 which projects through a bearing sleeve 50 and through an abutment block 51 engaging with' the periphery of the sound box. The sleeve 50 may be adjustably held in different positions by suitable means, such as by set screws 52 carried by the sound box and engaging with said sides of the sleeve 50. A nut 53 is threaded upon the projecting end of the rod 49, so that when rotated upon the rod 49, it will act against the abutment 51 and, through the pressure of the latter against the sound box periphery, will draw the rod 49 outwardly and tension the flexing member within its plane.

A diaphragm 54, corresponding to the diaphragm 35 of Figs. 8 and 9, is secured by a screw 55 to the flexing member, at a point in the span of the latter between its center and points of anchorage of its ends, as in Figs. 8 and 9. The diaphragm may have an annular angular peripheral flange 56 which engages with a sealing substance 57, corresponding to the substance 26 of Fig. 8, which substance is carried in awell or channel 58, so that the periphery of the diaphragm will be unrestrained in vibration except for the slight resistance offered by the sealing substance in the channel or well.

A disc 59 of magnetic material, such as soft iron, may be secured to the flexing memberupon the opposite face thereof from the diaphragm, in any suitable manner such as by the screw 55 which anchors the diaphragm to the flexing member, and suitable spacer.

washers 60 may be interposed between the flexing member and the diaphragm and armature disc.

In Figs. 13 and 14 a somewhat similar construction is provided, in which the armature disc is avoided. and the flexing member is made of magnetic or magnetically-responsive material. such as silicon steel or other magnetic material commonly employed for the diaphragms of telephone receivers or the armatures of electromagnets. In this form of the invention, the flexing member 61 is anchored at one end upon a threaded stud 62 which is carried by a. strip 63, secured between two sections" 64 and 65 of the sound box and projecting into the interior of the box. A

' second strip 66 extends over the stud 62 and the flexing member, and along the strip 63, so as to confine the bridge member upon the stud 62. The two strips 63 and 66 are secured together and to the section 65 of the sound box by a screw 67 which passes through the two strips and has threaded engagement with the section 65 of the sound box. A nut 68 may be threaded upon the free end of the stud 62 so as to securely clam the two . strips 63 and 66 to the flexing mem er at the point of connection thereto.

' The other end of the flexing member 61 passes through a slot 69 in the sound box casing and through a slot in an abutment member 70. A locking pin 71 is passed through an aperture 72 in the projecting end of the flexing member, so as to anchor the flexing member to the abutment member. One end of the abutment member is pivoted at 73 upon one of the screws (not shown) which passes between and connects the two sections 64 and 65 of the sound box casing. A stud 74 passes through and is threaded in the other end of the abutment member 70, and at its inner end has a ball-shaped tip 75 which engages in a concave cavity 76 in the peripheral wall of the casing, so that whenever the stud 74 is rotated, it will engage with the sound box casing, and that end of the abutment member 70 will be cammed outwardly to exert longitudinal tension upon the flexing member. The stud 74 may have a head 77 by which it may be rotated in either direction.

A diaphragm 78, similar to the diaphragm 54 of Figs. 10 and 11, is secured by a screw 79 to the flexing member as in the preceding embodiments. The diaphragm 78 has a peripheral flange 80 engaging in a well 81, carrying inelastic fluid sealing substance 82. A

permanent magnet 83 of the horse shoe or ring type is secured within one section 64 of the casing, and is provided with polar ends 84 which extend into proximity to the bridge member at opposite sides of the screw 79 which connects the flexing member to the diaphragm.

The polar ends 84 have the usual electromagnets 85 mounted thereon and included in the telephone circuit, so that when an undulating current is passed through the electromagnets 85, the flexing member will be magnetically vibrated in accordance with the undulations of the current. The flexing member being of magnetic material will, of course, respond to the variable magnetic field or pull which is caused by the undulating current in the electromagnets. and the diaphragm will be correspondingly vibrated with the flexing member.

The diphragm is connected at an interior 12 the variable tension has been applied to the shorter section of the span from-the point of connection to the diaphragm, in Figs. 13 and 14, the adjustable tensioning means is connected to the longer'section of the span.

When a device constructed in accordance with the invention is used as a telephone receiver, the electromagnets of the receiver mechanism will exert a pull upon the flexing member tending to flex the same, and as the current in the electromagnets fluctuates, the pull upon the flexing member will likewise fluctuate. By reason of the tension and elasticity of the flexing member, it will always tend to move away from the electromagnets when the current therethrough decreases or is in a direction to neutralize the magnetic pull and, therefore, the flexing member will vibrate in accordance with the undulations of current in the controlling circuit.

to the flexing member, it will be given a substantially perfect piston action, which is acknowledged as the most desirable form of vibration if the most perfect acoustical result is to be obtained. The two diflerent materials used as sealing means in the two different classes of devices illustrated-one, an inelastic fluid substance such as very thin oil, water, etc.; and the other a substance such as Vaseline being retained in operative position by the surface tension and its natural adhesive qualities well known thereof; both of these substances prevent the escape or entrance of displaced air peripherally of the diaphragm at each piston movement and,

therefore, sound waves of considerable intensity will be set up during the minor vibra tions of the diaphragm, where the air dis-t placement is slight.

At the same time, especially in those devices which will permitthe use when in operative position of the diaphragm in a horizontal position, the sealing means will offer practically negligible resistance to the diaphragm vibration. The sealing means will also, together with the coating of the diaphragm, prevent vibrations of the diaphragm or parts thereof which are not caused by and which do not correspond to the fluctuations of the'undulating current, or of the movements of the stylus in the case of a talking machine. The flexing member'is placed under tension from opposite points, preferably substantially diametrically opposite, and it has been found that the characteristics of reproduction or operation of the mechanism may be varied to some extent by varying the tension of the flexing member.

The flexing member, because it is tensed and combined with the diaphragm whose inherent vibrations are damped, does not respondreadily to minor vibrations which are caused by static and extraneous noises and, therefore, furnishes the most practical method of eliminating the audibility of such annoyances.

From the various examples which have been given, it will be observed that in reproducing instruments, the flexing member may be vibrated bylevers or linkage, or directly by a magnetic pull, but it will also be obvious that many of the advantages of these constructions will accrue when the diaphragm is operated by impinging sound waves, and the movements of the flexing member and diaphragm resulting therefrom utilized either to make sound records, or in the creation of an undulating current as in microphones and other transmitting telephonic instruments it is also equally apparent that the tensed bridge member shown and described may be utilized to drive any desired type of reproducing vibratory element of which various lands are well known.

- It will be obvious that various changes in the details, which have been herein described and illustrated for the purpose of explaining the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. 1

I claim 1. In an acoustic device, a support, a vibratory element connected to said support, a substantially rigid diaphragm connected to said vibratory element, and an inelastic fluid c0- acting with the free peripheral edge of the diaphragm and aflording little resistance to its movement.

2. In an acoustic device, a sound box comprising a casing with a sound wave exit, a substantially rigid diaphragm disposed'over said exit, and a receptacle in said casing provided with .an inelastic fluid for the reception of the peripheral portion of said diaphragm.

3'. In acoustical apparatus, a support, a diaphragm-held in operative position, and inelastic fluid means in said support co-operating'with the periphery of said diaphragm to dampen the movement of said diaphragm.

4. A diaphragm mounting comprising a support, a diaphragm, an inelastic fluid in said support in contact with the peripheral portion of said diaphragm.

5. An acoustic reproducing device having only one flexing member, said flexing member having a len h equal to at least'twice any of its other imensions and supported only at its two ends, and means for tensioning said flexing member inthe direction of its length.

6. An acoustic reproducing device comprising only one flexing member for performing the periodic motion, said flexing member III being made of one piece of material having a length equal to at least twice any of its other dimensions and connectedly supported only at its two ends, and means for tensioning said flexin member in the direction of its length.

7. i n acoustic reproducing device for the conversion or translating electromagnetic variations into sound or sound waves into electromagnetic variations, comprising a magnetic actuating means, a flexing member of magnetic material having a length equal to at least twice any of its other dimensions supported only at its two ends, and means for tensioning said flexing member in the direction of its length, said actuating'means act ing directly on said flexing member.

8. In an acoustic device, a support, a bridge member anchored at its ends to said support, a diaphragm connected at an interior point to said bridge member at one side of the center of the span of said bridge member, whereby when the bridge member and diaphragm vibrate together the bridge member will be flexed.

9. In an acoustic device, a support, a flexible member anchored at its ends to said support, a diaphragm connected at an interior point to said flexible member, at one side of the center of the span of said flexible member, whereby when the flexible member and diaphragm vibrate together the bridge member will be flexed, and means for tensioning sa d flexible bridge member in the direction of its length.

10. In an acoustic device, a support, a bridge member anchored at its ends to said support, a diaphragm connected at an interior point to said bridge member at one side of the center of the span of said bridge member, whereby when the bridge member and diaphragm vibrate together the bridge member will be flexed, the anchorage of at least one end of said bridge member being adjustable to place the bridge member under variable tension within its plane.

11. In an acoustic device, a support, a bridge member connected to said support, a diaphragm connected to said bridge member, and an inelastic fluid for coacting with the free peripheral edges of the diaphragm.

12. In an acoustic device, a support, a bridge member connected at opposite ends to said support and under-tension within its plane, a diaphragm connected to said bridge member, and a substance in that state in which the particles move freely among themselves, remain in one mass, and always takes the form of the containing means, for coacting with the free peripheral edges of the diaphragm.

13. In an acoustic device, a support, a bridge member carried by the support, a diaphragm connected at an interior point to said bridge member at a point in the span of the same, and a substance in that state in point to said bridge member at a point in the span of the same, means for actuating the tensed flexing member and through it the diaphragm, and an inelastic fluid carried by the support and engaging with the free periphery of the diaphragm, so as to offer little resistance to the piston-like movements of the diaphragm.

15. In an acoustic device, a support, a flexible bridge member connected under tension within its plane to said support, a vibratory reproducing element connected to said bridge member for vibration therewith, and means for vibrating said bridge member.

16. In an acoustic device, a support, a bridge member connected under tension within its plane to said support, a diaphragm connected to said bridge member for vibration therewith, means for vibrating said bridge member, and a substance having appreciable fluidity carried by the support and engaging with the free periphery of the diaphragm.

17. In an acoustic device, a support, a bridge member, means for anchoring the ends of the bridge member to the support under tension, said anchoring means permitting the placing of variable and desired tensions upon said bridge member, a free edge vibratory reproducing element connected to said bridge member, and means for vibrating the bridge member.

18. In an acoustic device, a casing having a sound wave opening in a wall thereof, a spring bridge member carried by the casing, a diaphragm connected at an interior point to the bridge member at a point in the span of the same and extending substantially parallel to and slightly spaced from said wall, said casing having a channel carrying a substance having an appreciable fluidity, wit-h which substance the'free periphery of the diaphragm engages.

19. In an acoustic device, a casing having a sound wave opening in a wall thereof, a spring bridge member carried by the casing under tension within its plane, a diaphragm connected at an interior point to the bridge member at a point in the span of the same, and extending substantially parallel to and slightly spaced from said wall, said casing having a channel carrying a substance having an appreciable fluidity with which substance thefree periphery of the diaphragm engages.

20. In an acoustic device, a casing having a sound wave opening in a wall thereof, a spring bridge member, means for anchoring the ends of the bridge member to the casing,

and adjustable to place the bridge member under "ariable tension within its plane, a diaphragm connectedat anv interior point to the bridge member at a point in the span of the latter, and extending substantially parallel to'and slightly spaced from said well,

which substance the free said casing having a channel carrying a substance having an appreciable fluidity, with phragm engages.

21. In an acoustic devlce, a support having a channel therein, an inelastic fluid in said channel, a substantially rigid diaphragm, means for mounting said diaphragm from its interior on said support, said diaphragm hav ing a free peripheral portion entering said channel and engaged by said substance.

22. An acoustic device, comprising a casing having a wall provided with a sound wave opening therethrough, said wall having a channel, a diaphragm having a peripheral angular flange entering said channel, a substance having appreciable fluidity disposed in said channel and engaging with the flange of the diaphragm, and means connected to an interior point of the diaphragm for support means comprising a spring bridge memberto the span portion of which the interior 7 point of the diaphragm is connected.

24. An acoustic device, comprising a casing having a wall rovided with a sound wave opening theret rough, said wall having a channel. a diaphragm having a peripheral angular flange entering said channel, a

substance having appreciable fluidity disposed in said channel and engaging with the flange of the diaphragm, means connected to an interior point of the diaphragm for supporting the latter for vibration toward and from said wall, said supporting means comprising a spring bridge member to the span of, which an interior portion of the diaphragm is connected, and means bywhich said bridge member may be vibrated.

25. An acoustic device, comprising a casing having a wall provided with a sound wave opening therethrough, said wall having a channel, a diaphragm having a peripheral angular flange entering said channel, a substance having appreciable fluidity disposed in said channel and engaging with the flange of the diaphragm. means connected to an periphery of the dia interior point of the diaphragm for supporting the latter for vibration toward and from said wall, said supporting means comprising a spring bridge member to the span of which an interior portion of the diaphragm iscon- ,nected, and means for placing said bridge member under tension within its plane.

26. An acoustic device, comprising a casing ing the". bridge member under variable tension within its plane.

27. 1 An acoustic device, comprising a casing having a wall provided with a sound wave 0 ening therethrough, said wall having a -c annel, a diaphragm having, adjacent its periphery,

an angu ar flange entering said channel,asubstancehavingappreciablefluidity disposed insaidchannel and engaging with the flange of the diaphragm, and means including a bridge member connected to an in-' terior portion of the diaphragm for supporting the latter for vibration toward and from said wall, the connection between the diaphragm and bridge member being at a section in the span at one side of the central point of the span.

28. In acoustic apparatus, a sound box com- I prising a casing with a sound wave exit, a free edge vibratory reproducing element disposed over said exit, and a spring bridge member secured to said element and to the periphery of the said casing.

29. In acoustic apparatus, a sound box comprising a casing with a soundwave exit, a

free edge vibratory reproducing element disposed over said exit, a spring bridge member secured to said element and to the periphery of the said casing, and means adapted to tension the said spring bridge member.

30. In acoustic aparatus, a sound box comprising a casing with a sound Wave exit, a diaphragm disposed over said exit and having a flange on its outer rim, a receptacle in the said, casing for the said flange, and a spring bridge member secured to the said diaphragm and to the said casing.

31. In acoustic apparatus, a sound box comprising a casing with a sound wave exit, a diaphragm disposed over said exit and having a flange on its outer rim, a receptacle in the said casing 'for the said flange, a spring bridge member secured to the said diaphragm and to the said casing, and means adapted to tension the said spring bridge member.

32. In acoustic apparatus, a sound box comprising a casing with a sound wave exit, a diaphragm disposed over said exit and having a flange on its outer rim, a receptacle in the said casing provided with slightly resistant airtight closure means for the rece tion of the said flange,=a s ring brid e mem r secured to the said diap ragm an to the said casing,

and means adapted to tension the said spring bridge member. p

33. In acoustic apparatus, a sound box comprising a casing with a sound wave exit, a diaphragm disposed over said exit and having a flange on lts outer rim, a receptacle in the said casin for the said flange, a liquid like substance in the said receptacle, a spring bridge member secured to the said diaphra and to the said casing, and means to tenslon the said spring bridge member.

' 34. In acoustic apparatus, a soundbox comprising a casing with a sound wave exit, a diaphragmdisposed over said exit and having a flange on its outer rim, a receptacle in the said casing for the said flange, a jelly like substance in the said receptacle, a spring bridge member secured to the said diaphra and to the said casing, and means to tension the said spring bridge member.

35. In acoustic apparatus, a sound box comprising a casing w1th a soundwave exit, a

prising a casing with a sound wave exit, a iaphragm disposed over said exit and having a flan e, a spring element secured to the said diap ragm and the said casing, means adapted to tension the said spring element, whereby the said diaphralgm is free to vibrate but is rendered practical y incapable of flex-- 40. In acousticapparatus, a sound box comprising a casing'wlth a sound waveexit, a diaphragm disposed over said exit and hav- 39.- In acoustic apparatus, a sound box coma mg a flange on its outer rim, a receptacle in x the said casing for the said flange, a sprin element secured to the said diaphragm an the said casing, and means-adapted to tension the said spring element whereby the said diaphragm is free to vibrate but is rendered practlcally inca able of flexing.

In witness w ereof, I hereunto subscribe my signature.

CHARLES N. WARNER.

diaphragm disposed over the said exit, and I a reed secured to the said diaphragm and to the said casing.

36. In acoustic apparatus, a-sound box comprising a casing with a sound wave exit, a

diaphragm di osed over said exit and havmg a rectangu ar flange, a receptacle in the sald casing containing an inelastic fluid and adapted for the reception of the sald flange, and a reed secured to the said diaphragm and to the said casing.

is free to vibrate but is rendered v diaphra practically incapable of flexing.

38. In acoustic apparatus, a sound box comprising a casing with a sound wave exit, a

diaphragm disposed over said exit and having a ange, a receptacle in the said casing provided with a fluid airtight closure means for the reception of the said flange, a spring se-' cured-to the said diaphra and to the said casing, anld mians t1azdap to tension the said spring w ere y e said dia hra to vibrhte but is rendered pradticafi? ble of-flexing. v a

is free incapa-

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