US2763333A - Sound transmission and reproduction - Google Patents

Description

Sept. 18, 1956 l H, M, SCHUMANN 2,763,333

SOUND TRANSMISSION AND REPRODUCTION Filed OCT.. 5, 1951 United States Patent O SUND TRANSMISSION AND REPRGDUCTION Hans Maassen Schumann, Philadelphia, Pa.; Josephine Mason Petts, executrix of said Hans Maassen Schumann, deceased Application ctober 3, 1951, Serial No. 249,540

14 Claims. (Cl. 181.S)

This invention relates to sound transmission and reproduction and particularly to methods and apparatus utiliring multiplex selective sympathetic resonance by what 1s termed herein a Macrophonic Unit.

The invention is based upon and incorporates a novel sound responsive material whose acoustic functioning is based on the phenomenon of individually selective sympathetic resonance to secure the complete production or reproduction of complex sounds to a degree never before attained.

Scientically, of course, the potentials of individual sympathetic vibration are well known, but in the practical field of sound, as for instance in music, this knowledge is used only partially and incompletely, and almost incidentally, and in the most rudimentary and primitive fashion. Such abortive uses may be present, for instance, in a marimba. or like instrument, carrying tubes with an air column tuned to the fundamental tone of the corresponding sounding piece of metal or wood; in drums with two parallel skins tuned to each other, and in a piano when the sustaining pedal is used. But in this latter case, even in a perfectly tuned instrument, sympathetic resonance is badly hampered by the tuning in tempered pitch of every piano. For all practical purposes, even these instruments are so far from utilizing selective sympathetic resonance to the degree necessary for respouse to every vibration in the multiplex thereof as to be unworthy of consideration as examples of utilization of the principles stated.

In the large eld of electro-acoustic sound transmission the principle of selective individual sympathetic resonance has not yet been used. For instance, in all known present day loud speaker systems, a number of tones, different in character, pitch, and volume are produced simultaneously by a sounding body of general resonance with a more o-r less flat surface, as, for instance, by a paper cone. While, of course, such paper sheet is tri-dimensional, i. e., it must have some thickness, the dimension in thickness is so minute in contrast to its other dimensions as for all practical purposes to have but two dimensions. Owing to the integrality and homogeneity of the paper cone different tone vibrations are therefore bound to interfere physically with each other to unpredictable degrees, and at least to such an extent that the produced sound is one which is possessed of a recognizable typical character of the particular sounding instrument, i. e. the typical loud speaker sound.

Any sound, simple or complex, received microacoustically at its source by a microphone remains unaltered in its conversion with electric pulsations in the electrical transmission, and should be reproduced macroacoustically, i. e. in amplified form as an exact replica of any original sound present in the conversion thereof into electrical pulsations, without any noticeable changes in character and quality happening in the amplifying unit. It is notorious of typical cone speakersvthat such macrophonic amplication is impossible and the differences berice tween the original sound and the reproduced sound are so evident, even in so-called high delity speakers, with multiple cones, etc., that anyone can determine instantly that the reproduction is of a modified character typical of such speakers.

In order to eliminate such acoustic distortions and changes in character and quality of the reproduced sounds, the physical interferences between vibrations must be eliminated. As such interferences are inherent in solid, even, uniform and homogeneous Vibrating bodies, such as in paper cones, this vibratory responsive unit must be replaced or augmented by a vibration responsive unit in which mutual interferences are substantially impossible, if acoustic distortion is to be eliminated.

lt is a primary object of this invention to provide a vibrating body of a heterogeneous three-dimensional structure containing a multiplicity of varigated vibroreactive units or items functioning in selective individual sympathetic resonance without mutual interference.

It is a further object of the invention to provide a vibro-responsive unit for functioning in selective individual sympathetic resonance Without mutua-l interference by which by-noises are better responded to and transmitted. By this means clearly audible and well balanced reproduction of very high pitched overtones and formants as well as acoustically complex mechanical by-noises, which represent to a large extent the individual character of an original sound, such as music, are transmitted. For instance, line by-noises produced by the scratching of the resined how on the strings of a violin, the air noise at the onblo-w of wood instruments and organ pipes, the impact sound of a piano hammer, and breathing by-noises in singing and speech, are all inadequately reproduced by a vibrating unit of a non-heterogeneous structure producing simultaneously lower and higher pitched sounds. This loss effects a lack of naturalness in the sound of the individual instruments and consequently results in a lack of transparency in very complex musical sound combinations noticeable especially in a reproduction of an orchestral piece.

ln carrying out the invention in an illustrative embodiment, l provide as a vibrating unit, either a natural or synthetic multiplex structure containing a great variety of vibroreactive particles or minute areas disposed for simultaneous respective functioning in effecting the varied individual sympathetic resonance combining in -a complex sound transmission according to the improved method of lthis invention. The multiplex structure, if a natural product, preferably will be treated chemically, and the synthetic multiplex structure will usually, although not necessarily, incorporate the chemical treatment in its formation to the end that the particles or minute areas, which may be more or less discrete, or continuations of other areas, having free or 4attached ends, combine elasticity with adequate body 4and tension characteristics, for respectively producing a certain individual sound or vibratory resonance response according to their individual structures, as determined by the weight, diameter, length and tension thereof.

As purely illustrative examples of such structures occurring in nature, constituting raw materials possessing,y desirable multiplex structures, reference is made to certain types of natural Sponges and to the pericarpial skeletons of some gourd plants.

The synthetic structures, simulating in some stages of ytheir creation and organization the natural multiplex structures of the natural materials mentioned, or otherwise formed by extrusions, moldings, and shapings and the like, may be produced with plastics i. e. thermoplastic or thermosetting resins land the like, rubber, natural or synthetic, cellulose of many types as of wood pulp, cotton, Wool, or asbestos, glass and other suitable raw material.

In order to give an example of the suitable treatment of natural grown raw material for purposes of this invention, it will be considered from the standpoint of using a natural product such as lulfa, in its treatment and use in sound production or reproduction, for instance, at the end of an electro acoustic sound transmission. The formation and use of synthetic materials for the purpose will follow the principles of the structural entity of the lulfa as treated, so far as is possible within the limitations of the material itself, or will have its own skeletonized mult-iplex structure, `which is readily accomplished when the operations of the unit are comprehended from the illustrative luft'a to be described.

They raw lua pericarp, on the market -in at, cornpressed pieces of Liqa egypzaca or Luya cylindrca, is placed in a bath of water or in a water solution, say, with vinegar, in which it expands fully to its origin-al shape by its strong power of imbibition. After removing surplus liquid, the pericarp is cut open longitudinally and the inner vascular bundles are `separated and cut as much as needed.

In a semi-dry state of the pericarp, or parts of it, are flattened out and fastened to a fiat piece of dry, solid material, such as a thick piece of cardboard. In this res-trained position the luffa is thoroughly dried, say, under heat lamps. When completely dry, the lulfa is removed from the board and is cut and yshaped as suited for the different adaptations to be later discussed. In order -t-o improve the -elasticity of the tissues and at the same time for protection `aga-inst air moisture, the dried cut pieces are preferably, although not always essentially, sprayed with a light texture of a Very liquid emulsion or solution of natural or synthetic rubber or a plastic with similar effects. When this light coating dries it will be seen that the random lengths, thicknesses, doubly or singly attached skeletal elements are permanently fixed into a unitary but multiplex structure in which any complex sound finds some sympathetically responsive separately vibratable element or area having a natural period or frequency to respond by sympathetic resonance thereto, whether an isolated, or even complex or compounded vibration, and substantially Without mutual interference With any other isolated or complex or compounded vibration.

It will be seen that as thus created, the structural unit has extremely wide uses in acoustic devices, Whether as comprising sounding or resonance boards for instruments, or as aiding devices for standard sounding boards or the like. However, -there is such a Wide field of use for the invention in the art of speakers that it will be explained illustratively in its association with or as replacements for typical paper cone speaker assemblies. It will be recognized, however, that in its broader aspects 'the impulse for acoustic reaction in selective sympathetic resonance can be obtained in many d-ilferent ways.

In `the accompanying drawings forming part of this description:

Fig. l represents a fragmentary enlarged perspective of a multiplex structural unit possessed of individual select-ive sympathetic resonance, and especially one of the natural forms thereof, such as luffa.

Fig. 2 represents a diagrammatic section through a speaker organization in which vascular bundles of the illustrative treated and coated lufta, or its synthetic equivalent, are fixed rmly to the front side of a paper cone speaker, generally conforming to the contour of the cone and converging toward an apertured center concentric with the focal axis of the cone. The direction of propagated sound is indicated by the arrow.

Fig. 3 represents a similar section through another speaker organization in which a diaphragm of treated lula, or its synthetic equivalent in a series of vascular bundles is provided, generally flattened on one side and fixed over the metal frame of the loudspeaker. This diaphragm is contacted in its center acoustically by a luffa bundle cut for the purpose and contacting directly with the moving coil unit mounted on or actuating the apex of the paper cone, and functioning as a sound bridge for transmitting vibrations directly into the lula diaphragm for the same purpose and with function related to the sounding post of a violin. The direction of propagated sound is indicated by the arrow.

Fig. 4 represents a similar section through a flat diaphragm of thin, airproof and elastic material, illustratively rubberized, thin nylon, carrying over its entire surface a number of treated vascular bundles of lutfa or its equivalent, cemented to lthe flexible diaphragm as with latex, `and disposed as a vibra-tory unit in airtight reation to the metal frame of the speaker, and with a supplemental or auxiliary preferably parabolic reflector disposed in juxtposition to the vibratory unit for rellecting the sound for transmission in the direction indicated by the arrows.

Fig. 5 represents a diagrammatic elevation of the organization of Fig. 4, incorporating a sound shade closed by a diaphragm with the entrapped air heated by a heat lamp, to improve the acoustical quality.

Fig. 6 represents digramma-tically a switching circuit combining a speaker according to this invention in alternation to or in supplementation of a conventional cone speaker, controllable through a `rheosta't for modulating or cutting out the cone output.

Fig. 7 represents a fragmentary section through ia sounding board carrying a plurality of bundles of the heterogeneous vibrating material, such as lul-fa.

Referring to the fragment shown in Fig. l, the luffa pericarp comprises vascular bundles comprising pluralities of main branches 10, and submain branches 11, generally parallel to the primary main branches, and myriad cross connections 12 extending between the main branches. These cross connections and various main branches meet in nodes of varying sizes, the branches and cross connections are of almost infinite ranges in thickness, length, tensions, and other characteristics, and are in more or less random directions of relative extent and angularities and when severed to form cut bundles, this random character of the various components enhances the range of acoustically responsive individual components, in the organization ofthe heterogeneous vibratory unit.

In utilizing such a heterogeneous organization, in one speaker organization as indicated in Fig. 2, the speaker organization initially comprises a paper cone i4, attached to and vibrated by the magnetic coil organization 15, in any conventional hook-up therewith, so that electrical impulses, carrying all of the various vibrations of the source, effective on the electrical unit 15, transmit them to cone 14. As noted, owing to the homogeneous texture of cone 14, mutual interferences occur, damping and distorting certain vibrations, when the cone is used alone. However, a mass of the vascular bundles of treated lulTa 16, or the like heterogeneous mass, are xed firmly to the front side of the paper cone, and provided preferably with a central aperture 17, concentric with the coil unit 15. In use the vibration of the loudspeaker cone 14 is purposely suppressed and is replaced by the vibrations in the luffa bundles. This is done for the purpose of stressing acoustically the individualization in a compound sound by a multitude of individual sympathetic reactions in the vibrating unit.

In the form of invention shown in Fig. 3. the paper cone 20 is provided, mounted on annular frame 26 and actuated as usual by the magnetic coil 22 connected to its apex. A hollow cylinder 23 is provided substantially concentric with which a luffa-made sound bridge element 24 and is mounted in contact with the vibrating element of magnetic coil 22. Vascular bundles of luffa are mounted as a luia diaphragm 21 on frame member 26 in contact in the center With the bridge component o1 element 24. When the magnet coil 22 is energized with sound energy components, the full sound of the paper cone is unhampered. This is rstly due to the complete porosity of the diaphragm 21, and secondly due to the extreme lightness in weight of the luEa-made sound bridge 24. At the same time, by the individual sympathetic resonance of an added multitude of structurally diierent vibrating particles 25, the improved identity with the original sound becomes clearly discernible.

in the form of the device shown in Fig. 4, the paper cone 3d is mounted with a magnetic coil organization 3i at its apex on frame 34 of the loudspeaker. An elastic diaphragm 32, as of rubberized or latex-coated nylon, is stretched on frame 34 of the speaker unit, and carries on one face a luffa diaphragm 33 mounting a plurality of vascular bundles of luia 3S. A parabolic sound reiiector 36 is provided in iixed, but adjustable, relation to the frame member 34 of the speaker organization. Reector 36 may be nonparabolic, if desired.

When magnet coil 31 is actuated, the cone 30 vibrates an air column existing between diaphragm 32 and front of cone 3i?, and the sound borne by this air column is almost entirely replaced by the much clearer and more complex sound reproduction by the vascular bundles 35 on the diaphragm 33, reacting acoustically to the vibrations of the closed-in air column. At the same time, the sound coming from the rear of the cone remains unhampered. ln `order to exploit the full extent of the acoustical quality of this combination, the loud speaker unit described is placed in front of the preferably parabolic sound reector 36, adjacent the group of luifa bundles on the diaphragm. Preferably, the external surfaces of the luifa bundles arc shaped to conform to the rounded surface form of the reflector.

In order to raise the temperature of the air surrounding the macrophone set-up of Fig. 4, advantageous for any development of sound, a sound shade 37 can be added to the edge of the preferably parabolic sound reflector, closed by a diaphragm 38 of thin elastic material, as, for instance, rubberized, thin nylon. This diaphragm allows a higher temperature inside the sound shade, produced by a suitably placed, small heat lamp 40, without interfering with the outcoming sound, as shown schematically in Fig. S. The thin, rubberized nylon diaphragm is impervious and prevents the escape of the heated air, while permitting free passage of sound waves. The parabolic reflector aids in effectively focussing the heat energy toward the center of the speaker, with enhanced etliciency of the macrophonic unit. Obviously, the lamp may be within the enclosure and at any desired point therein.

in Fig. 6 a speaker, as shown in any of Figs. 2, 3, or 4, indicated generally at 41, has its magnetic coil coupled to a source of electrical energy containing converted sound energy. A conventional loudspeaker 42 is provided in reasonably close association therewith, and this is coupled in parallel relation to the electrical energy source through a rheostat 43. By judicious use of rheostat 43 a mixture of sounds is created from the respective speakers, which in combination give excellent sound effects, capable of modulation as desired. Use of the rheostat or potentiometer d3 is controlled in accordance with the amount of space or room in which the sound is reproduced, as the standard cone speaker only provides a background of room effect.

in each case, preferably, the vascular bundle for a vibrating group is chosen from luffa pericarps, or the simulations thereof, natural or synthetic, differing in size, in order to improve the structural variety of vibrating items in the combined group.

it is usually preferred that the electric volume be raised somewhat over that necessary with ordinary paper cones, in proportion to the enlarged amount of vibrating material.

it wiil be appreciated that the selection of a given form of unit of the three types shown in Figs. 2, 3, and 4 and 5 respectively, alone or in a combination as shown in Fig. 6,

6 depends upon the purpose of the sound apparatus and the amount and kind of space into which the reproduced sound is to be projected, which purpose and space considerations differ widely over a large iield of sound reproduction.

The invention effects remarkable improvements at the end of an electro-acoustic sound transmission for the reproduction of music, speech, or other sounds, as described. It is repeated, however, that it has wider applications than in these speaker installations, and that th auction of units of the invention reacting in multiplex selective resonance in sympathetic vibration offers to the builder of musical instruments a very delicate sound amplification, for instance, in connection with the functioning of the body of a violin or the thin sounding board or" delicate keyboard instruments like the harpsichord or clavichord. A detail of such sounding board or body is shown in Fig. 7, in which a relatively thin sounding board 5t) to which bundles of luifa pericarp 51 are attached, is shown.

When music is transmitted by a sounding unit of heterogeneous structure as recited herein, the sounds, diiferent in pitch and volume and reproduced by items, areas, or particles vibrating in selective sympathetic resonance occur in ditferent places all over the unit. Thus a wandering about of the sound vibrations can be clearly followed by the sense of feeling, for instance, by touching the surface of the sounding unit with the full palm of a hand. Thus, as an interesting sidelight on the invention, a deaf person is enabled by the invention to enjoy music by touch, in a fashion similar, though more direct and more complex, to that by which a blind man can enjoy a story printed in Braille.

lt is pointed out again that although natural luifa has been recited as preferred form of heterogeneous vibration-responsive material for the purpose ot securing individual selective sympathetic resonance, it is illustrative of a larger group of materials, which are available and are contemplated for use herein.

Having thus described my invention, l claim:

l. A resonating unit of heterogeneous structure containing a manifold quantity of individual vibro-responsive components, each component having its own specific combination of length, weight, thickness and tension characteristics and being sympathetically resonant to a particular frequency of vibration in the audible range, said components being of such great number and of such variegated resonance response by reason of relative differences in such combinations of characteristics that there is a resonating component in the unit for substantially every vibration in the audible range, whereby substantially all of the vibrations of a complex of sounds in the audible range incident on said unit are resonated and propogated substantially without mutual interference, and means for transmitting complex sounds to said unit.

2. A sound producing organization comprising a heterogeneous structure formed of an integral member containing a multiplicity of vibro-reactive components, having random combinations of length, Weight, diameter and tension characteristics susceptible to individual and selective varied sympathetic resonance, and means for impressing a complex sound on said structure whereby without mutual interference in said structure the individual vibrations in the complex are resonated in said structure.

3. An organization as recited in claim l in which said means comprises a sounding board.

4. An organization as recited in claim l, in which said means comprise the magnetic output of an electroacoustic sound transmission.

5. An organization as recited in claim l, in which said means comprises a cone speaker.

6. An organization as recited in claim 2 in which the structure comprises pericarps of luifa for producing si- 7 multaneously a variety of sounds dilerent in pitch and character by individual sympathetic reaction.

7. An organization as recited in claim in which the structure comprises dried pericarps of luia for producing simultaneously a variety of sounds different in pitch and character by individual sympathetic reaction, and a thin layer of latex-like coating on the pericarp, of such thinness as to inappreciably aiect the elasticity of the lutfa material While insulating the components against moisture penetration.

8. An organization as recited in claim 5 in Ywhich the structure is at the end of an electro-acoustic system for sound transmission and comprises vascular bundles of luta.

9. An organization as recited in claim 2 in which the structure comprises vascular bundles of lua and a separate vibrating part of homogeneous structure.

10. An organization as recited in claim 1, in which the structure comprises vascular bundles of lula formed as a diaphragm.

11. An'organization as recited in claim 1 in which the structure comprises vascular bundles of lutia formed as a diaphragm, a magnetic vibratory element, and a lutfa bridge contacting the vibratory element and said diaphragm to transmit vibrations to said diaphragm.

12. An organization as recited in claim 2, in which the organization comprises a exible and elastic diaphragm formed of woven fabric coated with latex, vascular bundles of luffa mounted on said diaphragm, and means for vibrating said diaphragm with a complex of vibrations to which the lulfa responds in selective sympathetic vibration.

13. An organization as recited in claim 2 in which the structure comprises a tlexible and elastic diaphragm,

vascular bundles of lutfa mounted on said diaphragm, means defining with said diaphragm an air column for vibrating said diaphragm, and means for energizing the air column with vibrations.

14. A resonating unit of heterogeneous structure comprised of a plurality of generally longitudinally extending irregularly spaced main branches, and a myriad of connections of which some are connected to and extend between pairs of main branches and some are connected to and extend from one main branch, each connection having its own combination of length, Weight, thickness and tension characteristics and being sympathetically rcs Onant to a particular vibration in the audible range, said connections being of such great number and of such variegated respective combinations of such characteristics and ot' respective sympathetic resonance response that there is a resonating connection in the unit for substantiallyl every vibration in the audible range, whereby substantially all of the vibrations in a complex of sounds in the audible range incident on said unit are rcsonated.

References Cited in the le of this patent UNITED STATES PATENTS Re. 16,367 Valentine June 22, 1926 1,812,389 Wente lune 30, 1931 1,851,208 Nicolson Mar. 29, 1932 2,013,695 Nicolson Sept. 10, 1935 2,670,053 Doms Feb. 23, 1954 FOREIGN PATENTS 279,180 Italy Nov. 5, 1930 746,599 France .Tune 1, 1933 494,696 Great Britain Oct. 31, i938 510,707 Great Britain Aug. 4, 1939

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