US1845987A - Apparatus for recordation and reproduction of sound - Google Patents

Description

Feb. 16, 1932. w, RICHMOND 1,845,987

APPARATUS FOR REGORDA'IION AND REPRODUCTION OF SOUND Filed Dec. 6, 1930 2 Sheets-Sheet 1 INVENTOR ATTORNEY Feb. 16, 1932. w, RlCHMOND 1,845,987

APPARATUS FOR RECORDATION AND REPRODUCTION OF SOUND Filed Dec. 6, 1930 2 Sheets-5heet 2 INVEN OR ATTORNEY Patented Feb. 16, 1932 UNITED STATES WALTER RICHMOND, OF CLEVELAND, OHIO APPARATUS FOR BECOR'DATION AND REPRODUCTION 01 SOUND original application filed larch 12, 1920, Serial No. 385,320. Divided and this application Med December 6, 1930. Serial No. 500,860. r

This invention relates to apparatus for translatingsound and is in the nature of a divisional application of my co-pending application Serial No. 365,320, filed March 12, 1920, on an apparatus for translating sound.

This invention relates to apparatus for translating sound. Heretofore in the translation of sound waves considerable ditliculties have been experienced in recording and reproducing sound'waves clearly.

These various diliiculties, their causes and eiiects, and the manner in which I have overcome them and made possible true and clear recordation and reproduction of sound of controlled volume will become apparent from the followings ecitication.

One object o my invention is to eliminate undesirable vibrations of various parts of the recording or reproducing apparatus, and

to record and reproduce the original-sound waves clearl and to reduce distortion or interference 0 other waves.

Another object of-myinVention is to reproduce the original sound waves and at the same time eliminate all other sound waves which from various causes inherent in many present reproducers find their way into the amplifying devices of commercial talking machines and mingle with the original sound waves to an objectionable extent.

Another object of my invention is to translate one class of waves into equivalent waves of another class and to retranslate from this class into the original class of wave in a man ner such that the final wave sufiers no serious deterioration from its several translations.

Another object of my invention is the sub stantial translation of sound waves into their equivalent mechanical or electrical waves or the reverse, the translation of mechanical or electrical waves substantially into their equivalent sound waves without a noticeable addition or introduction of waves.

Another object of my invention is to produce a diaphragm so delicately poised that it will respond tovery slight variations in tone or magnitude of vibration and which is at the same time so constructed and actuated interfering that it can swing through a greater amplitude than the greatest amplitude of vibration to which it will be subjected in use, thus enabling the reproduction of sound waves of reater volume than the original waves tree rom noticeable distortion in tone or clearness.

Another object of my invention is a diaphragm which will not lag appreciably behind the impressed vibration but will reach the limit of its greatest vibration substantially in unison with the impressed vibration and which will return to its normal position as re idly as the cycle of the particular tone whic is being impressed.

Another'object of my invention is a diaphragm, difi'erent portions of which haveydifferent periods of vibration or difierent key notes.

Another object of my invention is a diaphragm which, as a whole, has no key note.

Another object of my invention is to obtain clear enunciation in the reproduction of sound waves. V

Another object of my invention is to improve the reproduction of the human voice and other tones and to reduce the harsh, metallic, mechanical sounds such as are produced by man commonly used translating devices.

Anot or object of my invention is to record and reproduce sound waves so that they have substantially the same volume as the original sound waves without seriously impairing the quality of tone or enunciation as dis- -tinguished from various expediencies which have been in use, such as the fibre needle which roduces fairly good tones but of such low vo ume as to be undesirable.

Other novel features of my invention are described and claimed in the co-pending application above referred to and in my copending application, Ser. No. 500,661, filed December 8, 1930, relating to a method and apparatus for recordation and reproduction of sound.

In the drawings:

Fig. 1 is a side elevation of a form of reproducer embodying the principles of my invention, part thereof being shown with the casing removed. for purposes of clearness.

Fig. 2 is a bottom plan view of the reproducer illustrated in Fig. 1.

Fig. 3 is a somewhat diagrammatic illustration of one of the arrangements of magnets and electric circuits which may be used in my invention.

Fig. 4 is a reducedview of the right half of the reproducer, as illustrated in Fig. 2, and is taken on a plane indicated by the line CC of Fig. 2.

Fig. 5 1s a reduced view of the left half of the reproducer as illustrated in Fig. 1, and is taken on a plane indicated by the line BB of Fig. 1.

6 is a side elevation of the body member of the reproducer illustrated in Figs. 1

and 2 illustrating the mounting of the stylus bar thereon and the rubber spacing ring and diaizphragm.

ig. 7 is a detail lan view of one form of torsion spring suita le for use in my invention.

Fig. 8 is a side elevation of the clamping ring of the reproducer illustrated showing another means for mounting the torsion spring.

able r use in my reproduoer.

Figs. 10, 11- and 12 are cross-sectional views illustrating forms of diaphragms which may be used in connection with my invention.

Fig. 13 is across-sectional view of a diaphragm similar tothat illustrated in Fig. 9 and is taken on a plane through the center" thereof.

Fig. 14 is a cross-sectional view of a preferred form of throat for use in my reproducer and is taken on a plane indicated by the line A-A of Fig. 5.

Referring to the drawings, Fig. 1 illustrates one embodiment of my invention in a reproducer having a body member 1 or principal art to which other parts are attached. This body portion ma be of either metal or wood and is prefera ly in the form of .a disk having a central opening in which is mounted the sound tube 2 for the transmission of sound waves to any amplifying device to which the reproducer may be attached. As illustrated in Figs. 1 and 2, a. diaphragm 3 is mounted on the body 1 by a clamping ring 4, the diaphragm being spaced from the body 1 by a rubber ring 5. This assemblage may be made conveniently by clampin the ring 4 against the body 1 by means of screws such as 6 and 7. In the form illustrated, the sound tube 2 passes through the body 1 and terminates in the plane of the face of the body 1 adjacent to the diaphragm. For purposes of clearness, the sound tube 2 is not shown in Fig. 2.

The ring 5 is preferably removable and ma be made of rubber or other suitable material. This ring is placed between the diaof an inch thickness may be used.

be formed integral with the body 1 and of a predetermined thickness so as to definitely x the distance between the face of the diaphragm 3 and the adjacent face of the body 1 or the opening in the sound tube 2. The

clamping ring 4 may be recessed, as better shown by the dotted line 8 in Fig. 8 to accommodate both the diaphragm and the'rubber ring 5. The clamping ring 4 is slotted, to form a assage for the stylus bar 13 when the stylus liar is mounted in one of the ways later to be described. I

Screwed, or otherwise rigidly fastened to the body 1 is a supporting plate 9 to which the ends of a torsion spring 10 are secured.

. Intermediate the points of connection of the spring to the plate, the plate is recessed, as

illustrated, the s ring bridging the recess.

However, if esired, instead of using the plate 9 suitably spaced lugs 11 may be cast or fastened on to the clamping ring 4 as illustrated in Fig. 8. Fig. 9 is a plan view of a diaphragm suit- The torsion spring, the purposes of which will now be described, may comprise a thin piece of metal. For example steel of 20/1000 In the present types of sound re roducers and recorders in which the stylus or is actuated by a record, the stylus bar is usually mounted on pivots and has no tendency to return to its normal position after it has been 1'3 actuated. Therefore it will lag appreciably behind the vibrations impressed upon it and return to its normal position only as a result of its being moved by the record or the diaphragm. When the diaphragm is so ham- 1 pered it will not produce a true tone or faithful reproduction but a distorted wave. To eliminate this undesirable actionI actuate my stylus bar with a torsion sprin The end portions only of the torsion spring engage the plate 9 or the lugs 11, these end portions being provided with screw holes for fastening the torsion spring onto the plate 9. The stylus bar is rigidly secured to the spring,

preferably at the center thereof, and extends 11,5v

to the center of the diaphragm. A suitable means of connecting the stylus bar to the spring is by means of a lug 12 rigidly secured to the stylus bar. This lug may pro ect laterally and be provided with a bore to receive 1 a stylus and a thumb screw to retain the stylus therein. As one example, a torsion spring of less width than its ends or supporting portions maybe used, the spring having a small central enlargement so that the stylus bar or lug supporting the same may be conveniently fastened thereto by screws. This type of spring is illustrated in Fig. 7. A stylus bar so mounted can vibrate by twisting the narrow portions of the torsion spring. For instance, in the case of reproduction of sound from lateral cut records the sound grooves of the record are lateral oi the path of move ment and the record transmits a lateral move ment through the stylus to the stylus bar by twisting the stylus bar about the longitudinal torsional axis of the torsion spring. The width of the s ring in the direction of mo tion of the sty us is suilicientl great to prevent any lateral movement of the spring itself at the point of the support of the stylus bar, so that the spring allows only a torsional or twisting movement similar to the movement which the stylus bar would have if it were mounted on pivots. At the same time, the stylus bar is returned to its normal position b the torsion spring no matter in what direction it has been moved or twisted by the action of the record on the stylus. ThlS return is rapid, the vibrating period or cycle of the stylus bar and spring assembly being in direct proportion to the breadth and thickness and inversely proportional to the length of the torsion spring. I make the torsion spring relatively short and thick, using for instance, steel 20/1000 of an inch in thickness. Such a 5 ring has such a high natural frequenc of vibration that it does not have any ten ency to blur or distort the sound waves transmitted through the stylus bar to the center of the diaphragm. Further, it raises the pitch of the stylus bar 13 and actuates it while keeping the pitch ofthe stylus bar higher than that of the human register. Therefore the stylus bar has no tendency to swing in unison with, or to impress its own period of vibration on the vibrations received from the record.

Another point at which sound waves are distorted in many talking machines is at the center of the diaphragm where there is a combination of a slow moving diaphragm and a slowv moving stylus bar which must be overcome 1 the power transmitted from the rec- 0rd. he torsion spring described is of suflicient strength to actuate the diaphragm also. Thus the key note of the entire assemblage as well as each part is raised above the audible ran e. This gives the stylus bar and the as sem lage a period oi vibration or key note, which is out of the audible range of vibration and consequently the combined diaphragm, stylus bar and spring do not synchronize with impressed vibrations and have no tendency to swing in unison with them or to impress their own period of vibration on them. @bvioua ly, the same is true of the torsion spring itself. Therefore, vibrations which are carried up the stylus bar to the diaphragm are substan tially free from chatter, and any tendency of the stylus bar or the torsion spring to vibrate in unison with impressed vibrations and transfer the resultant vibrations to the diaphragm so as to blur the sound reproduction or recordation is eliminated. Such vibra-- tions as are impressed u on it to cause it to vibrate in unison therewith will be only such sounds as will not affect the human car, as they will be above the audible range. Since the stylus bar and diaphragm thus are actuated and are raised in pitch by a torsion spring of such a high period that they will not appreciably distort the impressed vibrations, I can employ a magnetically sensitive diaphragm that is, a diaphragm which is composed of or includes soft metal and which diaphragm has practically no period of vibration of its own.

In some cases, however, I prefer to use a diaphragm of spring tempered steel or other spring tempered material, preferably in the form of a disk mounted as a diaphragm in the diaphragm ring of the re roducer, In such cases, due to the fact that t e diaphragm has a spring action and will return to its normal position almost as rapidly as it is moved by the vibrationsiofthe stylus bar, the stylus bar may be mounted on pivots in the usual fashion and without a torsion spring.

For instance, the spring tempered dia' phragm in Fig. 13 has its own tendency to return to normal osition and to return the stylus bar and. hol the stylus bar at a higher pitch than the ordinary diaphra would do and consequently, the stylus or may be mounted on pivots, as stated.

As set forth in the objects of my invention, it is necessary to have a diaphragm so delicately poised that it will respond to very slight variations in tone or magnitude of vibration and at the same time of such resil iency that it is capable of swinging through greater amplitude than the greatest amplitude of vibration that will be; impressed upon it when in use. Wl enls eak of a resilient the diaphragm, I mean one w llCll will reach the limit of its greatest vibration substantially in unison with the impressed vibration and which will return to its normal position as rapidly as the cycle of the particular tone no which is being impressed. In other words,

the diaphragm must not lag appreciably behind the impressed vibrations or there will be what is known as distortion. This distor-' tion, in reality resultants of the diaphragm Us tone caused by its lagging behind the im pressed vibration is overcome by the torsion sprin as described, and my magneto and electric circuit, later to be described, and a diaphragm having no keynote as a whole, but

sent a soft fibrous surface, blotting paper servin as a fairly good illustration 0 such soft fi rous surface. For exam la, a hard fiber diaphragm, one face of which is covered with blotting paper, may be used. In the case of reproduction of the human voice, for example, such a soft fibrous working surface on a diaphragm will give to the sound waves leaving the diaphragm a more natural human tone. Also it will give an improved tone to the sound wave of whatever instrument is be in? reproduced. urther, I have found that if a diaphragm is divided into two or more diaphragms" or portions b the use of a smaller diaphragm or by rings ormed or riveted, or otherwise secured in place on the diaphragm, each of the portions will have a period of vibration of its own and the diaphragm will be in effect, a compound diaphragm having no keynote as a whole.

I shall now discuss a number of dianames? use of such a diaphragm, I have been able to distinguish two voices singing in harmony.

To use this ty of diaphragm effectively in my magneto e ectric reproducer it is only necessary thatthe ring 14 be magnetically sensitive. The material which I use for the diaphragm in such case may either be magnetic or non-magnetic, in fact any material commonly used for diaphragms is satisfactory. i

These rin s will be operated on by the magnets and electric members of m reproducer and will give substantially t e same results as though I had used a completely magnetic or magnetically sensitive diaphragm. p y

This tvpe .of diaphragm may be covered on one side by a soft fibrous material as above mentioned; This fibrous'surface imparts to the tone produced by the diaphra m, especially in the case of reproduction o the human voice a more natural tone which I have not phragms embodying the principles abovebeen able to produce with a diaphragm ha enumerated.

The diaphragm illustrated in Figs. 9 and 10 has been divided into two or more diaphragms or areas by use of a ring or annulus 14 secured in place on the diaphragm by rivets 15 or otherwise. This ring, or rings, if more than one is used, may be of the same material as the diaphragm or of a stiffer material. A diaphragm with rings so mounted will have portionseach havin a different period of vibration. From 0 servation it appears that the outer diaphragm or portion 16 will have a low period of vibration, the ring section or annulus 14 will have a higher period of vibration and the inner diaphragm or central circular portion 17 will have a still higher period of vibration. Each area responds to different periods of vibration and each area will res ond more readily to its own key note. For this reason the diaphragm as illustrated has no key note to which it will respond as a Whole.

I have found that a diaphragm divided into three diaphragms or portions as illustrated in Fig. 9 gives ver desirable results in the separation of soun s of different frequencies of vibration. As a concrete example, the co-mingling vibrations resulting from the voice waves of a quartet traveling upl the stylus bar to the center of such a diap.ragm appear to be separated and each voice brought out clear and distinct and separate from the other voices, the outer diaphragm being responsive to the voices in the lower register, and the middle diaphragm being responsive to the voices in the middle register and the inner diaphragm being responsive to the voices in the higher register.

Thus desired and distinct separation of different voice tones and different toned instruments or of a plurality of sounds having different wave lengths is obtained. By the ing a smooth or glazed working surface.

Fig. 10 is a cross-sectional view of this diaphragm with rings riveted in place on opposite sides. These rings divide the diahragm into three diaphragms or portions or the purposes enumerated above. The diaphragm itself may be made of any substance commonly used for diaphragms or may be either magnetic or non-magnetic, as stated.

In Fig. 11 is illustrated a diaphra m, composed of two or more substances. or instance, the diaphragm may be composed of a material either magnetic or non-magnetic and a soft fibrous material 18 orof a hard fibrous material with a soft fibrous material or of mica and a soft fibrous material, the object being to secure a resilient diaphragm with a soft and roughened fibrous surface which produces clearer tones than the harsher-or metallic side of the diaphragm.

Fig. 12 illustrates a diaphragm divided into three diaphragms or portions, each having its own key note and in addition has the advantages of a diaphra composed of two or more substances as i lustrated in Fig. 11. As stated the outer portion appears to vibrate more in unison with the lower tones, the super-imposed rings 19 in unison with tones of the middle register and the small inner portion responding more readily to tones of the upper register, for example, the soprano. The soft fibrous covering produces etter and more natural tones in all registers and thus renders the diaphragm especially effective for ireproducingi1 the 'human voice clearly. In such a diap ragm the desired and distinct separation of the voice tones of different pitches is obtained and slurring and blurring are eliminated, or are so reduced as to be unnoticeable. This soft fibrous surface is designated at.20.

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earnest u ,dlruirther type oil diaphragm is illustrated in l ig. l3. 'lhis diaphragm is a compound diaphragm composed of spring tempered steel or other sprin tempered disk 21 divided into three partshy a ring or rings 22 soldered or otherwise fastened in place on the diaphragm tor the purposes described. The whole diaphragm is covered with a thin layer oi soztt fibrous material 23.

The action of this diaphragm is similar to the one illustrated in Figs. 9 and 12 with the exception that it is resilient within itself and has its own tendency to return to its normal position consequently it may be used in a reproducer the stylus bar of which is mounted on pivots as previously described andthus dispense with the use of a spring or resilient mounting for the stylus bar. In the drawings the thickness of the diaphragm and ot the rings or annuli have been exaggerated tor clearness of illustration.

ltteiterring now to the ma netic elements of my invention, one action permanent magnets on the diaphragm is to eliminate diaphragm noises. Any diaphragm susceptible to magnetic action will, when vibrating from entraneous causes, in a magnetic field, become what is usually known as dead heat, that is, it will lose its tendency to vibrate in its own hey note and will tend to come instrmtly to rest in unison with the cessation ct vibrations imparted to it by a stylus bar, or otherwise. .An action of the electric winding is to reduce the power required to the diaphragm in motion against the resistance oi the magnets without detracting :l'rom the ability of the permanent magnets to render the diaphragm dead heat. Thus the diaphragm may be started and vibrated more flreely lrom its normal osition oirest and consequently increasing t e amplitude ot vibration ot the diaphragm and amplifying the emitted sound without causing distortion or interiering tones is rendered possible.

ll will now describe one arrangement oli magnets and windings which i have found ellective.

ll/lonnted on and torming part nit the lace cit the body it are permanent magnets 2d and *ll'hese permanent magnets ertend through the body it to its lace, as illustrated, pole laces or the magnets lorming part oil the lace oi the body it i. a, lie in the plane the lace oi the body It adjacent to the dia phragm as shown in Fig, it. lo the repro ducer or recorder illustrated. in these permanent magnets are held rigidly in place on the body it by a non-magnetic metal box Eli which is screwed, or otherwise iastened, to the bod i. This box $2.65 also holds the outer end oil t' e sound tube 52 rigidly in place" The per manent magnets Q4 and are firmly clamped against two sides oi the benefit by the races at and Qt, the screws passing throng the center oi these pieces as shown at 29 in Figs.

1 and 2 and between the two prongs oi the permanent magnets and into the bot; lid. Electric windings 30 and 31 are provided on the poles of the permanent magnets 24 and 25. One of the windings which I have used is diagrammatically shown in Fig. 3, The windings comprising eight coils in all when magnets are used on both sides of the dinphragm, may be connected in series, series multiple or multiple or each coil may be short circuited, depending on the quality of: the tone and their particular action on the variious types of diaphragms that may be use If all the windings on one set of magnets on one side of the diaphragm are connected in a closed circuit with each other, a very heavy o iposinp; flux could be obtained ich would e eilective when the diaphrrt swings toward such magnets. 'llhis would very abruptly arrest vibration a diaphragm when it passed a given poi it ill its path of movement. On the other hand, the coils at one side of the diaphragm may be connected with the coils at the other side in such manner that the flux toward which the diaphragm moves induces a current in. the windings which is transferred to the other side of the diaphragm and may either assist movement of the diaphragm or may oppose movement, depending upon which termini of the opposite coils are connected. Uther noticeable eil'ects can be obtained by dill'er .ent combinations of these windings, especial ly when coils on opposite sides oi the diaphragm are connected together. A. few trials will demonstrate the particular windings and connections desirable for the diaphragm that is being used. With a non-metallic diaphragm carrying a metal annulus, I obtained thebest results by connecting the coils on one side in series multiple with the coils on the opposite side,

"the opposite magnetic assembly composed oi permanent magnets 32 and 33, the spacing bloclr 3d and the clamping members 85 and do together with the electric windings on the poles oithe permanent magnets 32 and are held with the pole faces of the magnets in spaced relation to the diaphragm b the supports 37 and 38 shown in Fig. 2. hose supports 3? and Bil are soldered or otherwise iastened to the clamping members and fit as shown in l2 and are rigidly secured to the body member 1 by the screws fill and it). it portion oil the support 3'? is shown in It with its two fastening screws. rt tion only is shown, the remainder being cut away to show the magnetic members more clearly. ll have'already described the verb ous connections tor the electric windings on permanent magnets. As described, perma: nent magnets are used on 0 onto sides oil roe liltl my magnetic diaphragm whlc may be cone when it is vibrating in a magnetic field, will in effect be a short circuited electric conductor around the lines of force and in effect become magnetized and act and react with the electric windings on the poles of the permanent magnets. I have secured some good results using aluminum, copper and brass diifaphragms for this induced electromagnetic e ect.

The pole faces of the permanent magnets on opposite sides of the diaphragm are of opposed polarity. The electnc and magnetic members of this invention are in no sense of the word electromagnetic and require no battery or outside power for their operation. Electromagnets could be used but would require more complicated windings and would be expensive to operate.

I have discovered that an action of magnetoelectric force on a diaphragm tends to render the diaphragm devoid of its natural period of vibration, as mentioned above, thus allowing the vibrations which come up the stylus bar to be translated into clear, concise tones without wave interference from the diaphragm. There are a large number of arrangements of connections between the coils of opposed magnets and between the coils of each set of magnets, each of these 11X- ing connections giving a difi'erent result. s additional examples, all or part of the windings of the magnets on one side of the diaphragm may be connected in series, series parallel or multiple with those of the other side or with each other, or short circuited. For these reasons, my reproducer could be put on the market to accomplish definite and different results.

It will be understood that I can make this invention in a more compact form by using the ring magnets, with soft iron pole pieces projecting toward the diaphragm at the proper oints and carrying the electric windings. ther obvious methods of making the reproducer in a compact form may be used without departing from the spirit of the invention.

For use with diaphragms which do not secure perfect separation and enunciation, I have provided a throat and orifice. The throat 41 is shown in Fig. 14 in section. The orifice 42 is shown only in Fig. 5 and is located within the sound tube 2. The throat is preferably made of cork although it will give desirable results if made of metal. I have discovered that the peculiar shape of the throat and orifice as shown at 42 Fig. 14 tends to produce clearer tones in almost any of the present types of talking machines. In the case of the human voice, for example, a greater clarity in enunciation is discernible when the orifice is used.

The outer end of the sound tube 2 is a slip-on connection for fastening the reproducer to the tone arm of a talking machine.

There are numerous elbows now on the market which if interposed between the outer end of the sound tube and the tone arm of a talking machine would enable the reproducer to be turned into position to play any of the disc records now on the market.

While I have described an embodiment of my invention particularly adapted to present day phonographs it should be noted that it includes, in its broadest aspects a number of 76 fundamental devices any one of which if used in connection with commonly used reproducers will make a decided improvement in their emitted sound waves, and I do not intend to limit my invention to the particular 80 forms, combinations and uses described.

By the use ofthese generic features the translation of sound waves substantially into their equivalent mechanical or electrical waves or the reverse, the translation of mechanical or electrical waves into their equivalent sound waves, is accomplished without noticeable addition or introduction of interfering waves, or more broadly the translation of one class of waves into waves of another class and the retranslations from this class into the original class of wave is accomplished without the final wave having suffered any noticeable deterioration from its several translations.

Various changes in the details of construction and arrangement of parts may be made without departing from the spirit of my invention or the scope of the appended claims.

Having thus described my invention, I claim:

1. In a sound translating device, a dia: phragm, 9. st lus bar adapted to be actuated by a needle or vibrating said diaphragm, a torsion spring connected to said stylus bar, 10 said torsion sprin having a period of vibration above the au ible ran e of sound.

2. A sound translating evice including a vibratable sound producing diaphragm, and means for vibrating said diaphragm at audihle frequency of vibration, and means for simultaneously impressing on said diaphragm a period of vibration above the audile range.

3. A sound translating device comprising a vibratable element, means for vibrating said element at audible frequencies of vibration, and means for impressing on said ele ment a period of vibration above the audible range during vibration of said element at audible frequencies, said means including a stiff spring operably connected to said element and having a period of vibration above the audible range. I

4. A sound translating device including a vibratable element, means to vibrate said element at audible frequencies, and means for impresing a period of vibration on the vibratable element above the audible range 430 during vibration of said element at audible frequencies.

5. A sound translating device including a magnetically sensitive vibratable element, means for vibrating said element at audible frequencies, and magnetic means for impressing on said element a period of vibration above the audible range during vibration of said element at audible frequencies.

6. A sound diaphragm having as a Whole a natural period of vibration below the audible range, said diaphragm having portions operating Within the audible range, and means to impress a superaudible period of vibration on said diaphragm.

7. A sound diaphragm having as a whole a natural period of vibration below the midi ble range, said diaphragm having portions operating within the audible range, and means to impress a superaudible period of vibration on said diaphragm, said means including a torsion spring.

8. A sound diaphragm having as a whole a natural period of vibration below the audible range, said diaphragm having portions operating within the audible range, and means to impress a superaudible period of vibration on said diaphragm, said means including a resilient member.

9. A sound dia hragm having as a whole a natural period oi vibration below the audible range, said diaphragm having portions operating Within the audible range, and means to impress a superaudible period of vibration on said diaphragm, said means inoludin a stiff spring.

10. n a sound translating device, a torsional member for impressing superaudible frequencies on a vibratable element, said torsional member being limited to torsional movement.

In testimony whereof, I hereunto afiix my signature.

WALTER RICHMOND.

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