Silent stringed musical instrument having body with viscoelastic layer for damping vibrations

Abstract: A silent stringed musical instrument includes a wooden body (1), a neck (2) projecting from one end of the wooden body, peg screws (4a-4d) attached to the neck, a tail piece (3) attached to the body, strings (5a-5d) stretched between the peg screws and the tail piece, a bridge (6) attached to the body in such a manner as to be held in contact with the strings and an electric system (7) for producing an electric signal from the vibrations of each string; when a player bows the silent stringed musical instrument for playing a tune, the electric system converts the vibrations of each string to the electric signal so as to produce electric sound; however, the body hardly vibrates, because viscoelastic layers (1f-1j) are inserted between wooden plates.

Description: FIELD OF THE INVENTION This invention relates to a silent stringed musical instrument and, more particularly, to a silent stringed musical instrument for producing electric/electronic sounds instead of acoustic sounds. DESCRIPTION OF THE RELATED ART A typical example of an electric stringed instrument is an electric guitar. The electric guitar has a solid body, and a neck projects from the solid body. Electromagnetic pickups are attached on the solid body, and strings are stretched over the electromagnetic pickups. When a player plucks the string, the string vibrates, and the electromagnetic pickup converts the vibrations to an electric signal. The electric signal is filtered and amplified, and an electric sound is produced from a speaker. Another electric stringed musical instrument is known as an electric bowed stringed instrument. The electric bowed stringed instrument has a configuration like an acoustic stringed instrument such as a violin, and electromagnetic pickups are also provided on the body. A player bows and plucks the electric stringed musical instrument, and the electromagnetic pickup converts the vibrations of the string to an electric signal. The electric signal is also filtered and amplified, and a speaker system produces an electric sound from the speaker. When a player connects a headphone to the amplifier, he hears the performance without disturbance to the neighbor. An electronic stringed musical instrument is similar in configuration to the electric stringed musical instrument, and the electromagnetic pickup converts the vibrations of the string to an electric signal. A signal processor extracts musical information from the electric signal, and produces musical data codes representative of, for example, pitch of a sound. The music data codes are supplied to a tone generator, and the tone generator produces an audio signal from the music data codes. In this instance, the player selects a timbre, and the tone generator imparts an envelope corresponding to the selected timbre to the audio signal. The audio signal is supplied to a sound system, and the player may hear the electronic sounds through a headphone. The electric/electronic stringed musical instrument allows the player to control the loudness of the sounds, and the electric/electronic sounds less disturb the neighbor. It is desirable for the player to minimize the acoustic sounds directly produced from the strings. While the player is bowing or plucking the strings, the strings vibrate, and the electric/electronic stringed musical instrument unavoidably produces the acoustic sounds. In this situation, the body has a strong influence on the loudness. If the electric/ electronic stringed musical instrument has a solid body, i.e., a body without a resonant chamber, the solid body hardly resonates with the acoustic sound, and is desirable from the aspect. However, the solid body is heavy, and does not allow a player to continue a performance for long time. Moreover, the solid body is quite different in touch from an acoustic bowed stringed instrument, and the player, who is familiar with an acoustic bowed stringed instrument, feels the solid body queer. The sound chamber of an acoustic stringed instrument such as a violin is a wooden mosaic work, and the wooden mosaic sound chamber is light and gives unique touch to the player. For this reason, it is desirable to'use the wooden mosaic sound changer in the electric/electronic stringed instrument. However, the wooden mosaic sound chamber well resonates with the vibrations of strings, and radiates loud sounds. In order to damp the resonant sound, a damping steel plate is inserted into the wooden mosaic sound chamber of a prior art electric/electronic stringed instrument. The damping steel plate is sandwiched between wooden plates. However, the damping steel plate makes the wooden mosaic sound chamber heavy, and the player feels a long performance difficult. Moreover, the damping steel plate increases the production cost of the electric/electronic stringed instrument. Other methods of making composite sound boards are found in U.S. Patent Nos. 4 353 862 and 5 333 527. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a silent stringed instrument, which is light, economical and well damps the acoustic sounds. To accomplish the object, the present invention proposes to insert a viscoelastic layer into wooden plates. In accordance with one aspect of the present invention, there is provided a silent stringed musical instrument comprising a body structure including a body of a laminated structure having a plurality of wooden plates and at least one viscoelastic layer adhered to said plurality of wooden plates and at least one string stretched over said body, having at least one end supported by said body and caused to vibrate so as to play a tune by a player. The silent stringed instrument may further comprise an electric circuit for producing an electric signal from the vibrations of the at least one string. BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of electric/electronic stringed musical instrument will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which: Fig. 1 is a plan view showing an electric violin according to the present invention; Fig. 2 is a bottom view showing the electric violin; Fig. 3 is a plan view showing a laminated structure of a body of the electric violin; Fig. 4 is a plan view showing a laminated structure of a body of another electric violin according to the present invention; Fig. 5 is a side view showing the structure of an electronic violin according to the present invention; and Fig. 6 is a side view showing a laminated structure of a body of the electronic violin. DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring to figures 1 and 2 of the drawings, a silent electric violin embodying the present invention comprises a body 1, a neck 2 and a tail piece 3. The neck 2 projects from the body 1, and has a box portion 2a at the leading end thereof. Peg screws 4a, 4b, 4c and 4d are rotatably supported by the box portion 2a, and the leading end portions of the peg screws 4a to 4d project into the inner space of the box portion 2a. The tail piece 3 is fixed to the body 1, and is spaced from the box portion 2a and, accordingly, the peg screws 4a to 4d. The silent electric violin further comprises strings 5a,5b, 5c and 5d and a bridge 6. The bridge 6 is attached to the body 2, and the strings 5a to 5d are stretched between the tail piece 3 and the peg screws 4a to 4d. The peg screws 4a to 4d wind up the strings 5a to 5d, respectively, so as to impart tension to the strings 5a to 5d. Vibrations of each string 5a/5b/5c/5d are propagated to the bridge 6, and a suitable means such as a piezoelectric element converts the vibrations of the bridge 6 to an electric signal S1. The electric signal S1 is supplied to a filter/amplifier 7, and, thereafter, to a sound system 8. The sound system 8 produces electric sounds from the electric signal S1. The sound system 8 may include a headphone. The body 1 is not expected to resonate with the vibrations of the strings 5a to 5d, and is equivalent to a half of the sound chamber of an acoustic violin. For this reason, the silent electric violin further comprises a chin pad 9 attached to the body 1. The chin pad 9 sidewardly projects from the body 1, and a player rests his chin on the pad 9 during the performance. The body 1 has a laminated structure as shown in figure 3. The body 1 includes a base wooden plate 1a, intermediate wooden plates 1b/1c on both sides of the base wooden plate 1a, outer wooden plates 1d/1e on outer sides of the intermediate wooden plates 1b/1c and viscoelastic layers 1f/1g/1h/1j. The viscoelastic layers 1f to 1j are adhesive, and are inserted between the base wooden plate 1a and the intermediate wooden plates 1b/1c and between the intermediate wooden plates 1b/1c and the outer wooden plates 1d/1e. For this reason, the intermediate wooden plates 1b/1c are bonded to the side surfaces of the base wooden plate 1a, and the outer wooden plates 1d/1e are bonded to the side surfaces of the intermediate wooden plates 1b/1c, respectively. The viscoelastic layer 1f/1g/1h/1j is formed of viscoelastic compound. The viscoelastic compound is spread over a released sheet, and is adhered to a side surface of the wooden plate. The released sheet is separated from the viscoelastic compound layer, and the viscoelastic compound layer is left on the side surface of the wooden plate. Otherwise, a pressure sensitive double coated sheet is used for the laminated structure. The viscoelastic compound is spread over both surfaces of a base sheet. One of the viscoelastic compound layers is adhered to one of the wooden plates, and another wood plate is adhered to the other viscoelastic compound layer without separation of the base sheet. The viscoelastic compound is acrylic compound or gum, and the base sheet is selected from the group consisting of cloth, non-woven fabric, paper, synthetic resin sheet and rubber sheet. The acrylic compound is desirable in view of durability. The pressure sensitive double coated sheet is manufactured by Sumitomo-3M Corporation Ltd. As "F9469PC". Acrylic compound is used in F9469PC, and does not lose the resiliency for long time. The viscoelastic compound is large in viscous resistance, and has viscosity like fluid and resiliency like a spring. When a violinist bows the silent electric violin, the strings 5a to 5d vibrate, and the vibrations are propagated through the bridge 6 to the body 1. The vibrations of the bridge 6 are picked up, and the electric signal S1 is supplied through the filter/amplifier 7 to the sound system 8. The vibrations are spread over the body 1, and are propagated from the base wooden plate 1a through the intermediate wooden plates 1b/1c to the outer wooden plates 1d/1e. The base wooden plate 1a, the intermediate wooden plates 1b/1c and the outer wooden plates 1d/1e respectively vibrate. The viscoelastic compound layers 1f to 1j are slowly deformed without constraint. However, the viscoelastic compound layers 1f to 1j are constraint in the laminated structure. For this reason, the viscoelastic compound layers 1f to 1j forcibly repeat the deformation due to the vibrations. Then, internal friction takes place in the viscoelastic layers 1f to 1j, and the vibrations are converted to thermal energy. In other words, the viscoelastic layers if to 1j have large vibration damping characteristics, and the body 1 radiates little noise. The viscoelastic compound layers are light and economical. For this reason, the viscoelastic layers 1f to 1j does not increase the production cost of the silent electric violin, and allows a player to play a tune on the silent electric violin for long time. In this instance, the body 1, the neck 2, the peg screws 4a to 4d and the tail piece 3 as a whole constitute a body structure. The vibration-to-electric signal converter such as, for example, piezoelectric elements and the filter/amplifier circuit form in combination an electric system. As will be understood from the foregoing description, the viscoelastic layers effectively damp the vibrations propagated to the body of the electric violin, and the body mostly formed of wood is light and economical. The player hears the electric sounds through the sound system, and enjoys a performance without disturbance to the neighbor. Thus, the electric violin according to the present invention is a silent stringed musical instrument. Second Embodiment Figure 4 illustrates the laminated structure of a body 10 forming a part of another silent electric violin embodying the present invention. The other parts and strings of the silent electric violin are similar to those of the first embodiment, and no further description is incorporated hereinbelow. Cellular layers are inserted into the laminated structure of the body 10. In detail, the laminated structure also includes a base wooden plate 10a, intermediate wooden plates 10b/10c on both sides of the base wooden plate 10a and outer wooden plates 10d/10e on the outer sides of the intermediate wooden plates 10b/10c as similar to the laminated structure of the first embodiment. The laminated structure further includes cellular layers 10f/10g/10h/10j provided between the wooden plates 10d/10b, 10b/10a, 10a/10c and 10c/10e, respectively, and viscoelastic layers 10k/10m/10n/10o/10p/10q/10r/10s between the cellular layers 10f to 10j and the wooden plates 10k to 10s. In this instance, the viscoelastic layers 10k to 10s are formed from the pressure sensitive double coated sheet, and bond the cellular layers 10f to 10j to the wooden plates 10a to 10e. In the assembling work, the viscoelastic layers 10k to 10s are adhered to both sides of the cellular layers 10f to 10j, and, thereafter, the other surfaces of the viscoelastic layers 10k to 10s are adhered to the wooden plates 10a to 10e. Although acrylic foam, urethane foam and rubber foam are available for the cellular layers 10f to 10j, the acrylic foam is preferable in view of the strength and the durability. The expansion ratio of the cellular layer ranges from 1.3 to 1.5, and the density falls within 0.65 g/cm 3 to 0.72 g/cm 3 . The laminated structure of the cellular layer and the viscoelastic layers is manufactured by Sumitomo-3M Corporation Ltd., and the product code is "Y-4914". The laminated structure "Y4914" has a cellular layer of acrylic resin form and viscoelastic layers of acrylic compound adhered to both side surfaces of the cellular layer, and the total thickness is 0.25 millimeter. The viscoelastic layers behaves as similar to those of the first embodiment. The cellular layers 10f to 10j have large resiliency, and prevent the wooden plates from peeling. Moreover, the cellular layers 10f to 10j enhances the vibration damping characteristics, and the acoustic sound is further reduced. Third Embodiment Figure 5 illustrates an electronic stringed musical instrument embodying the present invention. The electronic string musical instrument largely comprises a body 20, a neck 21 projecting from the body 20, peg screws 22 screwed into a box portion 21a of the neck 21, a tail piece 23 attached to the body 20, strings 24 stretched between the peg screws 22 and the tail piece 23, a bridge 25 fixed to the body and a chin pad 26. The neck 21, the peg screws 22, the tail piece 23, the strings 24, the bridge 25 and the chin pad 26 are similar to those of the first embodiment, and no description is incorporated hereinbelow. The body 20 also has a laminated structure as shown in figure 6. Upper/lower wooden plates 20a/20b are laminated on a base wooden plate 20c, and pressure sensitive double coated layers 20d/20e adhere the upper/lower wooden plates 20a/20b to the upper/lower surfaces of the base wooden plate 20c. In this instance, F9469PC or Y-4914 is used for the pressure sensitive double coated layers 20d/20e. The pressure sensitive double coated layers 20d/20e or viscoelastic layers behave as similar to those of the first embodiment, and effectively damp the vibrations propagated from the strings 24 to the body 20. When the viscoelastic layers 20d/20e are close to the upper and lower surfaces 20f/20g of the laminated structure, the viscoelastic layers 20d/20e are effective against high-frequency vibrations. On the other hand, the viscoelastic layers 20d/20e are close to the center line 20h, the viscoelastic layers 20d/20e are effective against low-frequency vibrations. The cellular layers may be inserted as similar to the second embodiment. Turning back to figure 5 of the drawings, the silent stringed musical instrument further comprises a signal processing unit 27, a tone generator 28 and a sound system 29. An analog signal S10 is supplied from the vibration pickup means such as, for example, piezoelectric elements to the signal processing unit 27. The signal processing unit 27 extracts pieces of music data information from the analog signal S10, and produces digital music signals S11 representative of electronic sounds to be produced. The digital music signals S11 are supplied to the tone generator 28, and the tone generator 28 imparts an envelop to a periodical signal on the basis of the digital music signals for producing an audio signal S12. The audio signal S12 is supplied to the sound system 29, and produces electronic sounds. A player may hear the electronic sounds through a headphone. The vibration pickup means, the signal processing unit 27 and the tone generator 28 as a whole constitute an electric system. Modifications Although the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention as defined by the claims. For example, the pressure sensitive double coated sheet may have a cellular layer serving as the base sheet. The body according to the present invention may be used in a stringed instrument having strings plucked by a player such as, for example, an electric guitar. The body according to the present invention is applicable to any silent stringed musical instrument such as, for example, viola and cello. A body may be a compromise between the first/second embodiment and the third embodiment. Namely, the wooden pieces are arranged in rows and columns, and the viscoelastic layers are inserted between the wooden pieces like a lattice. The wooden plates may be previously coated with thin synthetic resin film such as polyurethane primer film. The synthetic resin film enhances the adhesion between the wooden plates and the viscoelastic layers. In the above embodiments, the viscoelastic layers are provided in all the boundaries between the wooden plates. However, the viscoelastic layers may be selectively inserted into the boundaries. If a player do not care the touch of the body, the wooden layers may be selectively replaced with a synthetic resin layer.

Claims: A silent stringed musical instrument comprising a body structure (1/2/3/4a-4d/6/9; 10; 20/21/22/23/25/26) including a body (1; 10; 20), and at least one string (5a-5d; 24) stretched over said body, having at least one end supported by said body and caused to vibrate so as to play a tune by a player, characterized in that said body has a plurality of wooden plates (1a-1e; 10a-10e; 20a-20c) and at least one viscoelastic layer (1f-1j; 10k-10s; 20d/20e) for damping adhered to said plurality of wooden plates so as to integrate said plurality of wooden plates in a laminated structure. The silent stringed instrument as set forth in claim 1, further comprising an electric system (7; 27/28) for producing an electric signal from the vibrations of said at least one string. The silent stringed instrument as set forth in claim 2, further comprising a sound system (8; 29) responsive to said electric signal for producing a sound. The silent stringed instrument as set forth in claim I, in which said plurality of wooden plates (1a-1e; 10a-10e) are arranged in a transverse direction perpendicular to a direction in which at least one string extends. The silent stringed instrument as set forth in claim 1, in which said plurality of wooden plates (20a-20e) are laminated in a direction of thickness of said body. The silent stringed instrument as set forth in claim 1, in which said viscoelastic layer (1f-1j; 10k-10s; 20d/20e) is formed of viscoelastic material selected from the group consisting of acrylic compound and gum compound. The silent stringed instrument as set forth in claim 1, in which said viscoelastic layer (1f-1j; 10k-10s; 20d/20e) is formed from a pressure sensitive double coated sheet, and said pressure sensitive double coated sheet has a base layer and viscoelastic layers spread over both surfaces of said base layer. The silent stringed instrument as set forth in claim 1, in which said at least one viscoelastic layer is divided into two viscoelastic sub-layers (10k/10m, 10n/10o, 10p/10q, 10r/10s), and said laminated structure further has a cellular layer (10f-10j) inserted between said two viscoelastic sub-layers. The silent stringed instrument as set forth in claim 8, in which said cellular layer (10f-10j) is formed of the material selected from the group consisting of acrylic compound, urethane compound and rubber compound.

Inventors: YAMADA TOSHIYA, YAMADA, TOSHIYA
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1997
Main classification: G10H3
IPC codes: G10H3, G10H1, G10D1