US2001392A - Method and apparatus for the production of music - Google Patents

Description

y B. F. MiESSNER 2,001,392

METHOD AND APPARATUS FOR THE! PRODUCTION OF MUSIC Filed Dec. 14, 1952 INVENT BENJI/Yl/V F/7 Patented May 14, 1935 METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Benjamin F. Mies sner, Millburn Township, Essex County, N. J., asslgnor to Miessner Inventions, Inc., a corporation of New Jersey Application December 14, 1932, Serial No. 647,154

10 Claims.

This invention relates to musical instruments, and more particularly to those of the piano type. Such instruments are customarily constructed with the bottom or back of the resonator substantially unobstructed and consequently providing relatively efficient radiation of sound. At the same time, and particularly in instruments of the grand piano type, a large sound radiation takes place from the opposite sideof the resonator.

In and near the plane of the resonator a large cancellation of one radiation by the other occurs at the longer sound wavelengths, or lower frequencies. This produces a serious loss of effective amplitude atthese frequencies in the regions listeners are usually located. The various and respectively dissimilar reflections which may ocour to these two radiations before their arrival at any particular point undoubtedly mitigate this loss but by no means eliminate it.

According to. the present invention the radiation of one side of the resonator-for example the bottom side of a grand piano soundboard or the back side of an upright piano soundboardis absorbed without being permitted to escape from the instrument. In eflect the radiation efficiencyi. e., sound energy output with constant vibratory energy input-of that side of the soundboard is rendered substantially zero. In this way the cancellation abovementioned is obviated. At the same time the opportunity is afflorded to regulate the volume of sound output by regulation of the efficiency of radiation from the other side of the resonator, as by means of the'adjustable closures normally provided on one side of the resonator-e. g., the hinged lid and its hinged front portion on the conventional grand piano. Finally the instrument may be additionally provided with means for translating the string vibrations either directly or indirectly into electric oscillations, means for controlling the amplitude (and if desired other characteristics) of the oscillations, and means for translating the oscillations into sound, thus providing an instrument whereby direct vibration-sound translation (i. e., by the resonator) or vibration-sound translation through the intermediary of electric oscillations/are available each in regulable degree. 7

Thus it is an object of my invention to "provide an instrument with improved low frequency radiation. It is a further object to provide means for improving the low frequency radiation of an instrument of the class described.

It is another object to provide an instrument with a resonator, the radiation from one side of board ill.

which is absorbed and from the other side of which is controllably regulated. It is a still further object to provide an instrument with a resonator, with an alternative or auxiliary translating sys-- tem, and with means controlling the relative sound c radiations from said resonator and said translating system. Other and allied objects will more fully appear from the following description and the appended claims.

In such description reference is had to the ac- 1O companying drawing, of which:--

Figure l is a partial cross-sectional view of a piano embodying my invention, Figure 1 being taken along the line i-i of Figure 2; wherein the player and still more particularly the Figure 2 is a partial plan view thereof with the II lid removed; and

Figures 3 and 4 are partial cross-sectional views alternative to Figure 1, respectively taken along lines i-i and 4-4 of Figure 2 and illustrating modifications of my invention.

Reference being had to Figure 2, there will be seen a grand piano having a rim assembly com prising a rim i, a rim cross-member 2, and a plurality of rim-beams 3 angularly disposed between cross-member 2 and rim i. Spaced above rimbeams 3 may be provided a, soundboard or resonator ill, reinforced by ribs 4 on the bottom thereof, and maintained in slightly arched form by compression between rim i and cross-member 2. Secured to the top of soundboard it may be main or treble bridge b and bass bridge 5, over which bridges the strings I may be st ung to hitch pins 8 in plate it. These parts and their disposition may thus be conventional; and they appear in cross-section in Figure 1, together with the usual hammers iii and dampers 20, which may be actu-' ated by the customary key-operated. action, not shown. In Figure 1 there will also be seen the conventional lid 31], hinged to the top of rim i by hinges such as 35, and having front hinged portion 36. a

It will be understood that upon excitation of any string or strings l by the associated hammer IS, the resulting vibration of the strings will produce a vibration of the bridges and the sound- Sound waves are thereuponradiated from both top and bottom of the latter. Customarily the sound waves radiated from the bottom are unobstructed, excepting to a slight degree by virtue of rim-beams 3. According to my invention, however, this bottom radiation is absorbed and thus prevented from emanating into the surrounding air.

The absorption may be advantageously accomplished by providing a relatively stiff, but preferthe rim-beams 3 and extending over the entire area bounded by the rim I and cross-member 2. The member may conveniently be attached to the bottom of the rim-beams. Supported by this member, and preferably filling the space between the rim-beams and at least thinly covering them, may be provided acoustically absorptive material, such as felt. It is desirable that this material be graded in softness, the softest material being nearest the soundboard and'somewhat less soft material adjacent the outer member I I. Thus in Figure 1 a portion of the rim-beam 3 is broken away, showing a lower layer I2 of medium-hard felt, covered by a further layer 13 of soft felt, which may extend over the tops of the rimbeams.

It may be noted that the layer I3 should not only avoid contact with soundboard ID or ribs 4,

but is preferablyspaced'eway from the latter to provide an air chamber. If this be not provided or be made too small, excessive damping of the vibration of the soundboard may result; and on this account the customary spacing between rimbeams 3 and the soundboard l may be somewhat increased to advantage. It is convenient to provide means for retaining the layer l3 in its spacing from the soundboard. Such means may comprise a light copper wire screen 40 stretched between rim l and cross-member 2.

The only eifective sound radiation from the soundboard i0 is now from the top-illustrated side. This radiation is customarily under a considerable range of control by the closing and the opening to different degrees of the lid 31; and when this is closed, by the closing and opening of the usual separately hinged front portion 36 thereof. It is to be noted, however, that the degree of this control is now considerably increased, since the normally uncontrolled radiation from the bottom-illustrated side is now absorbed. I

The degree of radiation reduction with lid 31 and its front portion 36 closed may be further increased by providing a felt or other absorptive seal 42 between lid and rim, and by providing absorptive material vertically disposed between the front edge of the soundboard and the lid, of course with an appropriate gap for the strings. Such absorptive material is shown below the strings as 44, and thereabove as 45. The latter may be secured to a flange 46 carried by and at right angles to the hinged front lid portion 36. The material 45 is thus precluded from interfering withthe radiation when the front lid portion is opened.

Various refinements carrying still further the radiation reduction under the closed lid conditions may comprise the provision of absorptive material on the entire bottom of lid 31; the provision of such material in back of the fall-board of the instrument above the keys; and the as sembly of the ribs 4 and the parts thereby carried to a modified form of plate, which in turn is vibrationally insulated from the rim, as shown in U. S. Patent 1,912,293 issued to me May 30, 1933. This last construction has the advantage of reducing vibration of the rim and parts thereto rigidly secured by conduction from the soundboard and plate, which vibration is to some extent radiated as sound by the rim, etc.

A mechanico-electro-acoustic translating system, the sound radiation from which may be em? ployed under the closed lid condition as an alternate to the normal radiation, and as an auxiliary thereto under open lid conditions, is illustrated 2,001,392 ably vibrationally dead, member H underneath in Figure 1. A strip 23 is shown having a conductive top edge 24 in spaced relation to each of the treble strings; and it will be understood that a similar strip may be provided for the bass strings. This strip is the element of the translating system sensitive to the string vibrations and it may if desired be rigidly mounted; I prefer however, to mount it to the soundboard l0, having found this mounting especially adapted for the production of good tonal characteristics. The mounting may be accomplished by inverted T-shaped pieces 48, the upright of the T being slotted to receive the strip and the horizontal portion of the T being fastened to the soundboard. The slot may be of such a width that it will frictionally engage the strip 23. After adjustment of the latter in the slot to a position generally as close to the strings as possible without risk of contact therewith under conditions of maximum vibration of the latter, the strip may be glued or otherwise fastened to its supporting pieces.

The conductive edge 24 may be connected to the grid of a thermionic vacuum tube 25, whose cathode may be energized in any well-known manner, whose anode current may be supplied as from a tap 26 on battery or other high voltage source 21, and whose grid may be connected through high resistance 29 to a point rendered slightly more negative than the cathode by virtue of anode current fiow through condensively by-passed resistance 28. In the anode circuit of tube 25 are connected in cascade potentiometer or output control 34, amplifier 30, pedal-operated potentiometer or volume-control 3|, further amplifier 32 and loudspeaker or other electroacoustic translating device 33. I It is desirable to provide electrostatic shielding 39 around the tube 25 and immediately associated apparatus, and to provide a continuation thereof at least partially about the strings and translating system. Such continuation may take the form of one or more coats 38 of conductive paint applied to interior surfaces of the piano rim, lid, etc.

It will be appreciated that between each string 1 and the conductive surface 24 a small electrostatic capacity exists, and that these capacities in parallel with each other form a total capacity between strings and conductive surface. This capacity is charged from battery or source 21 through resistance 29, and this charge cannot change rapidly because of the high value of the latter resistance. If new any string I be vibrated in a vertical plane, as by striking by its hammer l9, the capacity between it and the conductive surface 24 will be varied oscillatorily in accordance with the frequency and waveform of the point of the string opposite the conductive surface. The total capacity between the strings and the surface will be likewise varied, though in reduced degree; and by virtue of the relatively constant charge in this capacity the voltage across it will likewise vary. The oscillatory variations in this voltage will be seen to be applied to the grid of tube 25; by this tube and succeeding amplifier 30 they are amplified; they may be controlled in respect of amplitude and further amplified if desired by controls 3| and 34 and by further amplifier 32, respectively; and finally they may be translated into sound and radiated as such by loudspeaker 33. Thus a mechanico-electro-acoustic chain of translation is provided which may be employed to produce a sound radiation of amplitude fully regulated by controls 3| and 34, and of general characteristics which may be subjected to wide further control.

It will be understood, of course, that I do not intend to limit the mechanico-electricportion of the alternative orv auxiliary translating system contemplated by my invention to the electrostatic type hereinabove described. Thus mechanicoelectric translating devices of the electromagnetic, piezo-electric, magnetostriction and other types may equally well be employed. These may be energized either directly from the strings, as in the case of the electrostatic system illustrated, or by a member vibrated by the strings in commone. g., the soundboard l0. Thus I have also shown in Figure 1 a mechanico-electric translating device comprising a polarized electromagnet 10 and an armature H secured to the soundboard lil immediately thereabove. The electromagnet 1B is immediately sensitive to the vibrations of the armature H, and is preferably maintained in a stationary position and for example may be mounted to a rim-beam 3.. A desirable position for the translating device is at a point directly under the treble bridge 5. The output of this device may be led to a center-tapped potentiometer it, the output terminals of which may comprise respectively the center-tap and the movable contact thereof. These output terminals may be connected in series with one of the input leads to amplifier W; for example across a shorting switch it. If this switch is open the output of the translating device it, regulated in amplitude and phase by the adjustment of the movable contact of potentiometer i2, is added to the oscillations supplied to amplifier 39 from tube 25, or it is substituted therefor if the control 3 is adjusted to eliminate the transmission of oscillations from tube 225.

It will also be understood that the alternative or auxiliary translating means contemplated by my invention may include those wherein the vibration-oscillation translation step is taken through an intermediate process-e. g., through an acoustic process. Thus in Figure l I further show an embodiment of my invention wherein a small portion of the bottom-side sound radiation from the soundboard iii is withheld from the absorption process and is translated into electric oscillations. A microphone or other acousticelectric translating device till is disposed in the chamber between the soundboard and the absorptive material iii. This may be mounted on rubber block til or in other vibrationally insu-'- lative manner. A centergtapped potentiometer it may be connected across this device 8%, like the potentiometer l2 across the device Ill, and its output terminals connected in series with those of the latter. By adjustment of the contacts of the potentiometers l2 and of the control 3% any one of the three auxiliary or alternative translating systems may be operated, or more than one in a variety of relative phase and amplitude relationships. While it have illustrated a single microphone and a single electromagnet, I may employ a plurality of either or both disposed at various positionsunder the soundboard l0, and interconnected in series, parallel, or seriesparallel. If desired individual potentiometers or other output controls such as the potentiometers 12 of Figure 1 may be provided across the individual microphones Thus I have shown in Figure 3 a plurality of microphones 80 with an individual center-tapped potentiometer l2 shunted across each microphone, and in Figure 4 a plurality .of mechanico-electric translating devices comprising electromagnets l and/ or electromagnets. I

and associated armatures I I, with like potentiometers shunted across each electromagnet. The output terminals of the several potentiometers may be connected together and across switch 13 of Figure 1.

The general advantage derived from the control of phase as well as-amplitude of the outputs of individual translating devices or systems depends on the difference in waveform of the oscillations produced by each, and comprises the ability to produce a more varied range of com-.

bined oscillation harmonic structures. Such difference in harmonic structure between the outputs of different microphones 80, for example, results from their placement opposite difierent portions of the soundboard; and the same is true for the plurality of the elctromagnets 10, which have been illustrated in Figure 4 at various positions under the bridge 5.

While I have disclosed my invention in terms of particular embodiments thereof, it will be understood such disclosure is intended to be exemplary rather than comprehensive, and that the scope of my invention is intended to be ex pressed by the following claims.

I claimz- 1 l. The combination with a musical instrument including a plurality of tuned vibrators and a resonator coupled thereto and adapted to radiate sound in accordance with their vibrations, of means for producing electric oscillations in accordance with said vibrations; an electroacoustic system for amplifying said oscillations and translating the same into sound, said system including and terminating in a diaphragm directly coupled to air external of said instrument; and a plurality of selectively adjustable control means associated with said instrument and electroacoustic system, whereby a variety of qualitatively different sounds may be produced at will, said control means comprising means included in said electro-acoustic system for varying the amplitude of said oscillations, and means home by said instrument for varying the emciency or radiation from said resonator.

2. The combination with a musical instrument including a plurality of tuned vibrators and a resonator coupled thereto and adapted to radiate sound in accordance with their vibrations, of means for producing electric oscillations in accordance with said vibrations; an electro-acoustic system for amplifying said oscillations and translating the sameintosound, said system including and terminating in a diaphragm directly coupled to air external of said instrument; and a plurality of selectively adjustable control means associated with said instrument and electro-acoustic system, whereby a variety of qualitatively difierent sounds may be produced at will, said control means comprising means included in said electro-acoustic' system for varying qualitative characteristics of said oscillations, means included in said 'electro-acoustic system for varying the amplitude of said oscillations, and means connected with said instrument for varying the emciency of radiation from of tone quality control which comprises translating said vibrations directly into a series of sound waves whereby to produce sound of a first quality, also translating said vibrations into electric oscillations and thence into a series of sound waves whereby to produce sound ot'a distinct quality, radiating both said series of sound waves, and separately and selectively controlling the efficiency of said radiation of the sound waves of said first series and the efficiency of said vibration-oscillation-sound translation.

4. In the production of musical tones from the vibrations of a tuned vibrator, the method of tone quality control which comprises translating said vibrations directly into a series of sound waves, also translating said vibrations into electric oscillations, modifying qualitative characteristics of said oscillations, translating said modified oscillations into a series of sound waves, radiating both said series of sound waves, and separately and selectively controlling the efficiency of said radiation of the sound waves of said first series and the efficiency of said vibration-oscillation-sound translation.

5. In the production of sound from the vibrations of a plurality of vibrators coupled to a common resonator different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the method of quality control of said sound which comprises producing a plurality of series of electric oscillations respectively in accordance with the vibrations of a plurality of different portions of said resonator, controlling the relative amplitudes of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

6. In the production of sound from the vibrations of a plurality of vibrators coupled to a common resonator different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the method of quality control of said sound which comprises producing a plurality of series of electric oscillations respectively in accordance with the vibrations of a plurality of different portions of said resonator, controlling the relative phases of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

7. In the production of sound from the vibrations of a plurality of vibrators coupled to a common resonator different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the

method of quality control of said sound which comprises producing a plurality of series of electric oscillations respectively in accordance with the vibrations of a plurality of different portions of said resonator, controlling the relative amplitudes and phases of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

8. In the production of sound from the vibrations of a plurality of vibrators coupled by a common vibratile system different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the method of quality control of said sound which comprises translating the vibrations of a plurality of different portions of said vibratile system into a corresponding plurality .of s:ries of electric oscillations, controlling the relative amplitudes of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

9. In the production of sound from the vibrations of a plurality of vibrators coupled by a common vibratile system different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the method of quality control of said sound which comprises translating the vibrations of a plurality of different portions of said vibratile system into a corresponding plurality of series of electric oscillations, controlling the relative phases of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

10. In the production of sound from the vibrations of a plurality of vibrators coupled by a common vibratile system different portions of which are vibrated with respectively different harmonic structures by any given vibrator vibration, the method of quality control of said sound which comprises translating the vibrations of a plurality of different portions of said vibratile system into a corresponding plurality of series of electric oscillations, controlling the relative amplitudes and phases of the oscillations of the several said series, and simultaneously translating all said controlled oscillations into sound.

BENJAMIN F. MIESSNER.

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