JPH0324595A - Reverberation plate for musical instrument - Google Patents

Abstract

PURPOSE:To obtain warm woody sound quality by forming a hollow part in the internal layer part of the abutting surface of a straightgrained timber veneer in the grain direction, forming projection parts at one adjacent abutting part and recessed parts at the other and fitting them together. CONSTITUTION:The reverberation plate 1 is formed by joining plural straight- grained veneers 2, 2 ... together and grooves 5, 5 ... are formed at the abutting parts of the veneers 2, 2 ... in the grain direction M. Further, the rectangular projecting parts 2a are formed at the right abutting parts of the veneer. 2, the rectangular recessed parts 2b are cut in the lift abutting parts of the veneers 2, and they are fitted together to join the veneers 2, 2 ... together. Consequently, the warm woody sound quality is obtained as well as or more than the use of high-class natural material.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a musical instrument soundboard suitable for use in, for example, a piano.

``Prior Art'' As is well known, the piano is a type of percussion instrument, and its sound production mechanism can be explained with reference to Figure 1O.
In conjunction with the movement of the key, hammer a rotates and strikes string b.

As a result, the string b is excited and drives the bridge d provided on the soundboard C. The vibration of this piece d drives the soundboard C, which causes the soundboard C to radiate sound. As can be seen from the above sounding mechanism, the role of the soundboard C in the piano is extremely important, and the characteristics of the sound of the via/s are mostly determined by the characteristics of the soundboard C. There are two characteristics required for a piano sound: good response to string strikes and a moderately extended sound. Therefore, it is necessary for the soundboard C to have characteristics that satisfy the above-mentioned requirements, and spruce wood such as spruce has been considered suitable as a material having such characteristics.

By the way, if the soundboard is made of only natural materials, the specific elastic modulus E
/γ (E: Young's modulus, γ: density) is limited by the value specific to wood, so there is a problem that it is not possible to achieve a certain level of sound efficiency. Therefore, soundboards were developed that increased the efficiency of sound production and were able to properly produce sounds from low to high frequencies (for example, JP-A-60-57
No. 894, JP-A-60-57895). This soundboard is
The material of the core material of a soundboard having a laminated structure is selected so that the transverse elastic modulus G is large and the shear loss tangent tan δ6 is small, or a sheet is interposed in the laminated structure.

In addition, in order to make the tone clearer, carbon fibers arranged in the grain direction of the outer layer are attached along both sides of the inner layer to increase the longitudinal elastic modulus E and reduce internal friction loss Q-'. A soundboard was also developed with
No. 93). According to this soundboard, the damping rate due to internal friction is reduced.

``Problem to be solved by the invention'' However, the conventional soundboard described above is not sufficient to produce the good woody sound (warmth of sound without metallic sound) as a natural musical instrument, and has inferior audible characteristics. There was a problem.

This invention was made in view of the above-mentioned circumstances, and not only can the good quality of wood sound be fully exhibited, but also the sound quality can be set artificially. The aim is to provide a soundboard for musical instruments that can produce a warm woody sound.

Another object of the present invention is to improve the mechanical strength and positioning accuracy of the serrated portions of each straight-grained veneer.

"Means for Solving the Problem" In order to solve the above problem, in a musical instrument soundboard made of a plurality of straight-grained wood veneers, at least one of the contact surfaces of the plurality of straight-grained wood veneers is provided. In the inner layer of the contact surface of
forming a hollow part of a predetermined width along the grain direction, and
It is characterized in that a convex portion is formed in one abutting portion of adjacent straight-grained veneers, and a concave portion is formed in the other abutting portion, and these convex portions and concave portions fit into each other.

"Function" The characteristic value corresponding to the transverse elastic modulus G of the soundboard 1 decreases, thereby increasing the value of the ratio E/G of the longitudinal and transverse elastic modulus.

As E/G increases, the frequency characteristic of the internal friction loss Q-' increases in the high range, and as a result, a high-cut filter-like effect occurs on the soundboard l.

Further, in the serrated portion, since the concave portion and the convex portion of each straight-grained veneer fit together, mechanical strength is increased, and positioning is performed by fitting, so positioning accuracy is inevitably improved.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1) Basic principle First, the basic principle of this invention will be explained.

First, as mentioned above, what is important about the vibration characteristics of a piano soundboard on the time axis are its good response to string vibrations and its appropriate energy conservation, that is, its appropriate non-damping properties. This is because the former characteristic corresponds to the good rise of the sound, and the latter characteristic corresponds to the extension of the sound. The specific dynamic Young's modulus E/γ (E: dynamic Young's modulus, γ: density) and the internal friction loss tangent tan δ are known as physical quantities for evaluating soundboard materials from these two viewpoints. Spruce subrus, which is excellent as a soundboard material, has a large E/γ and a small Q pull.

Next, in order to consider the sound quality of a piano, it is necessary to consider the frequency characteristics of the soundboard material.

This frequency characteristic is investigated as follows. First, a plate-shaped sample of a certain shape is vibrated under the condition that both ends are free, and the resonance frequencies of the excited flexural vibrations and the damping characteristics there are measured. From this measurement result and the solution of the Euler-Bernoulli beam vibration equation that takes into account only the elasticity of the plate, the apparent Young's modulus at each resonance point E=f
Sequentially find req and internal friction loss Q-1. In this way, the apparent frequency characteristics of each acoustic material can be investigated. Comparing the frequency characteristics thus determined with the perceptual timbre tendency of the acoustic material, it was found that there was a certain correlation between them. This is because the frequency characteristics of the apparent Young's modulus determine the frequency characteristics of the periodic strain in the soundboard excited by string vibration, that is, the displacement amplitude, and as a result, the frequency characteristics of energy loss due to internal friction. This is because it is conceivable. By the way, Young's modulus is originally a physical property specific to a material and should not have frequency dependence, but according to the above measurement results and analysis, the apparent Young's modulus has a predetermined frequency characteristic.

This can be explained by Goens' solution to the so-called Timoshienko beam vibration equation, which takes into account the shear forces (and rotational inertia) generated in the plate, under boundary conditions with both ends free. In Goens' solution, the apparent Young's modulus E − freq at each resonance point is proven to have frequency characteristics by considering the shear forces in the system. For example, in the case of a rectangular bar with an equal cross section, f is the natural frequency of the bar, Q is the bar length, and h is the thickness ta.
F(i): vibration order, constant determined by boundary conditions, s: constant determined by cross-sectional shape.

It is shown by the formula: As can be seen from equation (1), the frequency characteristics of the apparent Young's modulus E - rrec4 change depending on E/G, which is the ratio of the longitudinal and lateral elastic coefficients. In other words, the value of E/G determines the frequency characteristics of the internal friction loss Q-', which determines the filter characteristics of the soundboard, which determines the tone.

Subruce wood, which is known as a material that produces a warm woody sound, has a vertical and horizontal elastic modulus ratio of E/
The G value is particularly high compared to other industrial materials. In addition, previous research has revealed that what is generally called high-grade materials has extremely high E/G values (for example, Journal of the Japan Society of Mechanical Engineers, Vol. 91, No. 83).
No. 6, the paper "Engine Nearing of Piano Sound Quality".This is because when E/G becomes a large value, the loss in the high frequency band becomes large. This is because it is thought to be a factor that creates tone.

Furthermore, it was found that the value of E/G has a strong correlation with the following characteristics of piano sound.

(1) There is a positive correlation with the sound resonance characteristics, that is, the naturalness of the sound and the difference in pressure.

(II) There is a positive correlation with the depth characteristics of the sound, that is, the depth and the amount of low components.

(1) There is a negative correlation between the noise characteristics of acoustic radiation, that is, E/G and the amount of noise contained in the radiated sound.

These relationships are shown in the table below.

Table 1 Based on the above considerations, in this invention, the E/
The basic principle is to artificially increase the G and thereby create a warm woody sound.

On the other hand, the aforementioned Japanese Patent Application Laid-Open No. 60-57894, 60-57
In No. 895, since the transverse elastic modulus G was increased, the value of E/G became small, and a woody sound could not be obtained. In addition, in JP-A No. 57-136693, since the internal friction loss Q~1 in the high range is made small, the high frequency component is acoustically radiated and becomes a noise component, making it impossible to obtain a warm wooden sound quality. Ta.

(2) Structure and operation of the embodiment FIG. 1 is a plan view showing the structure of the first embodiment of the present invention. In the figure, a soundboard 1 includes a plurality of straight-grained wood veneers 2
, 2... are formed by combing them together. The soundboard l in this embodiment is a soundboard for a grand piano. Further, a long bridge 3 is provided at the center of the soundboard 1 along the grain direction M, and a short bridge 4 is provided at the upper right corner of the soundboard 1 in the drawing. The parts indicated by broken lines in the figure are veneers 2, 2...
The grooves 5, 5, . . . are provided along the grain direction M at the abutting portions of the . Here, FIG. 2 shows a cross section taken along the line AA in the figure. As shown in this figure, the abutting portion at the right end of the veneer 2 has a convex portion 2 that protrudes in a rectangular shape.
a, and the left end contact portion of the veneer 2 is a rectangular cutout recess 2b. Then, these are fitted together, and the individual units 2, 2, . . . are interlocked. Here, FIG. 4 is a view in the direction of arrow C shown in FIG. 1, and FIG. 5 is an enlarged view of the joint portion, and these figures show the above-mentioned fitted state in more detail. Further, a cross section taken along the line B-B' in FIG. 1 is shown in FIG. 3. As shown in FIGS. 3 and 2, the groove 5 has a predetermined depth from the bottom of the recess 2b of the veneer 2, and is provided along the grain direction of the veneer 2. In addition, the sound rod 10 shown in these figures is attached to the veneers 2, 2, etc. perpendicularly to the wood grain direction, and compensates for the propagation of vibration in the direction perpendicular to the wood grain direction, as well as suppresses the sound. This serves to reinforce the entire board 1.

As mentioned above, when the grooves 5 are provided on the joint surface of the veneer 2, the grooves 5
The strength against shear deformation decreases in the part of the soundboard 1.
The characteristic value corresponding to the overall transverse elastic modulus G becomes smaller. Therefore, the value of E/G increases, and the characteristics shown in Table 1 above are obtained. In this case, the extent to which the E/G can be increased can be arbitrarily set depending on how the depth, width, etc. of the groove 5 are set.

Here, the frequency characteristics of the internal friction loss Q in this example are shown in FIG. The illustrated curve Qa is the frequency characteristic in the example. Further, the curve Qb is the frequency characteristic of a normal soundboard material (natural material such as Stainless Steel). As can be seen from this figure, in the characteristics of this example, the amount of loss on the Takagi side is large, and a kind of high-cut filter-like characteristic is obtained. Therefore, a warm woody sound can be obtained.

In this case, since the Young's modulus and density of the soundboard 1 do not change, the specific dynamic Young's modulus E/γ and the acoustic conversion efficiency E/γ3
Young's modulus, etc., and other density-dependent acoustic properties are hardly impaired.

Furthermore, since the convex portion 2a and the concave portion 2b are fitted together, the strength of the joint portion is increased and the positioning accuracy is improved.

Note that it is most effective for the groove 5 to be located on the neutral axis of the soundboard 1.

(3) Modification ■ In the embodiment, the groove 5 was provided only on one side of the joint between the veneers 2, 2, but the groove 5 may be provided on both sides as shown in FIG. In this case, as shown in Figure 8,
If the width of the veneer 2 is W, and the depths of the grooves on one side and the other side at the joint are wl and w2, then the value of the characteristic corresponding to the modulus of transverse elasticity G can be approximately multiplied by lw- (wl + W2))/W. It is possible to change it. In this way, the transverse elastic modulus I
You can freely hunt the characteristic value corresponding to G.

(2) As shown in FIG. 9, the convex portion 2a of the veneer 2 may be formed into a triangular shape, and the concave portion 2b may similarly be formed into a triangular shape to fit therewith. Moreover, the shape of the recessed part 2a and the convex part 2b is not limited to the above-mentioned shape, but can be any other shape.

"Effects of the Invention" As explained above, according to the present invention, in a soundboard for a musical instrument formed by gluing together a plurality of straight-grained wood veneers, at least one of the contact surfaces of the plurality of straight-grained wood veneers is provided. A hollow part of a predetermined width is formed in the inner layer part of the abutting surface of the board along the grain direction, and a convex part is formed in one abutting part of the adjacent straight-grained veneer, and a convex part is in the other abutting part. By forming concave portions and fitting the convex portions into the concave portions, it is possible to fully demonstrate the good sound quality of the wood, and the sound quality can be artificially set. It is possible to achieve a woody sound that is even warmer than when using wood.

Furthermore, since each straight-grained veneer is joined together by fitting the concave portion and the convex portion, there is an advantage that the mechanical strength and positioning accuracy in the straight-grained portion are improved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention, and FIG.
The figure is a cross-sectional view taken along line A-A in Figure 1, Figure 3 is a cross-sectional view taken along line B-B in Figure 1, Figure 4 is a view taken along arrow C in Figure 1, and Figure 5 is the same view. FIG. 6 is a characteristic diagram showing the frequency characteristics of internal friction loss in the example; FIG. 7 is a cross-sectional view showing the configuration of a modified example of the example; Fig. 8 is a sectional view showing the relationship between the width of the veneer and the depth of the groove in the same modification, Fig. 9 is a sectional view showing the structure of another modification of the same embodiment, and Fig. 1O is a grand piano. FIG. 1...Soundboard, 2...Single board, 2a...
...Convex portion, 2b...Concave portion, 5...Groove.

Claims (1)

[Scope of Claims] A soundboard for a musical instrument formed by gluing together a plurality of straight-grained wood veneers, wherein an inner layer of at least one of the abutment surfaces of each of the plurality of straight-grained wood veneers has the wood grain. A hollow part of a predetermined width is formed along the direction, and a convex part is formed in one abutting part of the adjacent straight-grained veneer and a concave part is formed in the other abutting part, and these convex parts and concave parts are formed. A soundboard for a musical instrument, characterized in that the two are fitted together.