JPH0324596A - Reverberation plate for musical instrument - Google Patents

Abstract

PURPOSE:To obtain warm woody sound by adhering and fixing laminate members made of straight-grained timber veneers together by intermediate connection members which have abutting parts abutting on respective grain surfaces and fitting parts. CONSTITUTION:The straight-grained timber veneers 2a, 2b ... are joined by the intermediate connection members 6, 6 ... to constitute the reverberation plate 1 for a ground piano on the whole. Further, both width-directional end parts of the veneers 2a and 2b are staircase-shaped cut parts and both end parts 6a and 6b of an intermediate connection member 6 are fitted in the cut parts to form gaps 5 between the veneers 2a and 2b along the grain direction. Consequently, woody sound which is warmer than a natural material is realized.

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, a piano is a type of percussion instrument, and to explain its sound production mechanism with reference to Figure 8, first, the hammer a rotates in conjunction with the movement of the keys. Hit 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,
This causes the soundboard C to radiate sound. As can be seen from the above mechanism of sound production, the role of the soundboard C in the piano is extremely important, and the characteristics of the sound of the piano are mostly determined by the soundboard C.
determined by the characteristics of

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 the wood, so there is a problem that it is not possible to achieve a certain level of sound production 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 as to increase the transverse elastic modulus G and to decrease the shear loss tangent tan δ0, 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 were attached along both sides of the inner layer to increase the longitudinal elastic modulus E and reduce internal friction loss Q1. A soundboard was also developed (Japanese Patent Application Laid-Open No. 57-13669)
No. 3). 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.

Furthermore, there is a tendency for high-quality materials suitable for soundboards (particularly piano soundboards) to be in short supply, so the present invention also aims to improve the yield of expensive soundboard materials.

"Means for solving the problem" In order to solve the above problem, a laminated member made of one straight-grained board facing each other with a predetermined gap is made into a plurality of laminated members so that the grain directions are parallel to each other. and an intermediate connecting member having a contact portion that abuts each grain surface of adjacent laminated members and a fitting portion that fits into the gap of each adjacent laminated member, and connects each of the laminated members to the It is characterized by being adhesively fixed by an intermediate connecting member.

"Function" As shown in Fig. 1, as shown in Figs. 1 to 3, by providing the gap 5, the characteristic value corresponding to the transverse elastic modulus G of the soundboard 1 decreases. , the value of the ratio E/G of longitudinal and transverse elastic modulus increases. As E/G increases, the frequency characteristic of the internal friction loss Q-' increases in the high range, and as a result, the soundboard 1 acts like a high-cut filter. Moreover, since the straight-grained wood veneer 2 constituting the soundboard l is divided into small units, even if there is a defective part of the material, the veneer 2 can be effectively cut out from the part except for the defective part.

"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. Specific dynamic Young's modulus E/γ (E: dynamic Young's modulus, γ: density) and internal friction loss Q-' 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 specific dynamic Young's modulus E/γ and a small internal friction loss Q-'.

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 adjusted 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, we can determine the apparent Young's modulus E−f at each resonance point.
Sequentially find req and internal friction loss Q-'. 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 characteristic of the apparent (rng rate) determines the frequency characteristic of periodic strain in the soundboard excited by string vibration, that is, the frequency characteristic of displacement amplitude, and as a result, the frequency characteristic of energy loss due to internal friction. This is because it can be considered.

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 is explained by Goens' solution to the so-called Tymoshenko beam vibration equation, which also takes into account the shear forces (and rotational inertia) generated in the plate, under the boundary condition that both ends are free. In Goens' solution, the apparent Young's modulus E − rre at each resonance point is
It is proven that q has frequency characteristics by considering the shear force within the system. For example, in the case of a rectangular bar with an equal cross section, where f: Natural frequency of the bar, Q: Bar length, h: Thickness t
s, F(m): Constant determined by vibration order and 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 − freq are vertical,
It changes depending on the ratio of lateral elastic modulus, E/G. 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 paper "Engine nearing of piano sound quality". This is because when the E/G value becomes large, the loss in the high frequency band becomes large. In other words, it becomes a high-cut filter-like characteristic, creating a warm woody sound. This is because it is thought to be a factor.

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

(I) There is a positive correlation with the sound resonance characteristics, that is, the naturalness of the sound and the feeling of profoundness.

(II) There is a positive correlation with the depth characteristics of the sound, that is, the depth and the number of low-pitched parts.

(III) Noise radiation characteristics, that is, there is a negative correlation between E/G and the intensity 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-' 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, straight grain wood veneers 2a, 2a...
. . are joined via intermediate connecting members 6, 6, . . . and collectively constitute a soundboard l for a grand piano. Here, the A-A line cross section and B-B in the same figure
' cross-sections are shown in FIGS. 2 and 3, respectively. As can be seen from these figures, the veneers 2b, 2b, . . . are provided opposite the veneers 2a, 2a, . Single board 2a1
Both ends in the width direction of the intermediate connecting member 6 have stepped arrow sections as shown in FIG.
, 6b are adapted to fit into this notch. FIG. 4 (opening) shows the state after fitting, and as shown, a gap 5 of a predetermined distance is created between the veneer 2a and the veneer 2b. . As shown in FIG. 3, this gap 5 is formed between the veneers 2a and 2b along the grain direction. In addition, the upper end surface of the intermediate connecting member 6 and the single plate 2a
The positions of the upper end surfaces are aligned, and the lower end surfaces of the intermediate connecting member 6 and the lower end surfaces of the veneer 2b are aligned. Therefore, the upper and lower surfaces of the soundboard l are formed flat.

Further, the long piece 3 and the short piece 4 shown in FIG.
The strings are provided along the grain direction M at the center and upper right of the strings, and each supports a plurality of strings.

The sounding rod 10 shown in FIGS. 2 and 3 has single plates 2, 2...
... is attached perpendicularly to the wood grain direction, to compensate for vibration propagation in the direction perpendicular to the wood grain direction and to reinforce the entire soundboard 1.

As mentioned above, when the gap 5 is provided between the veneers 2a and 2b, the strength against shear deformation in the area of the gap 5 decreases, and the characteristic value corresponding to the transverse elastic modulus G of the entire soundboard l becomes small. Become. 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 distance, width, etc. of the gap 5 are set.

For example, as shown in FIG. 6, the distance from the left end of the veneers 2a, 2b to the right end of the right veneers 2a, 2b is W, and the gap
If the width of is W, then the property equivalent to the transverse elastic modulus of the material is (
W−w)/W times.

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 loss amount on the Takagi side is large, and a kind of noise-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.

Note that it is most effective to provide the gap 5 at a neutral position of the soundboard l.

"Effects of the Invention" As explained above, according to the present invention, a plurality of laminated members made of straight-grained wood veneers arranged oppositely with a predetermined gap are arranged so that the grain directions thereof are parallel to each other. At the same time, an intermediate connecting member having a contact portion that abuts each plate surface of adjacent laminated members and a fitting portion that fits into the gap of each adjacent laminated member is provided, and each of the laminated members is connected to the intermediate connecting member. Since it is fixed with adhesive using a connecting member, it is possible to fully demonstrate the good sound quality of wood, and the sound quality can be set artificially, and it also achieves a warmer wood sound than when using natural materials. can do.

Additionally, since the straight-grained wood veneer that makes up the soundboard is divided into small units, yields can be 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 sectional view taken along the line A-A in Figure 1, and Figure 3 is a cross-sectional view taken along the line A-A in Figure 1.
A sectional view taken along the line I3-B in the figure, FIG. 4 (a) is an exploded view for explaining the combined state of the veneer and the intermediate connecting member
FIG. 4(b) is an enlarged cross-sectional view showing the combined state of the veneer and the intermediate connecting member, FIG. 5 is a view taken along arrow C in FIG. 1, and FIG. 6 shows the gap width in the same embodiment. cross section,
FIG. 7 is a characteristic diagram showing the frequency characteristics of internal friction loss in the same embodiment, and FIG. 8 is a schematic diagram showing the keying mechanism of the grand piano. 1...soundboard, 2...single board, 3...piece, 5...gap.

Claims (1)

[Scope of Claims] A plurality of laminated members made of straight-grained wood veneers are arranged facing each other with a predetermined gap, and the grain directions of the laminated members are parallel to each other. It is characterized by comprising an intermediate connecting member having a contact portion that contacts a surface and a fitting portion that fits into the gap between each adjacent laminated member, and each of the laminated members is adhesively fixed by the intermediate connecting member. Soundboard for musical instruments.