JP2001306062A - Composite material for soundboard, and the soundboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material of a novel structure which has a high specific Young's modulus, low attenuation factor and strong anisotropy necessary for the soundboard of a musical instrument, is not affected by humidity and is superior as a replacement material for timber. SOLUTION: This composite material for the soundboard and this soundboard include a resin matrix (foamed polyurethane, etc.), having gaps and carbon fibers which are disposed in this resin matrix and, are oriented unidirectionally. The density thereof can be made to 0.38 to 0.52 g/cm3, the Young's modulus YL in a fiber direction to 9 to 15 GPa and the EL/GLR ratio to 5.0 to 7.0. The soundboard has respective peaks at least at 200 to 500 Hertz, 1000 to 2000 Hertz and 5,000 to 7,000 Hertz in the frequency response characteristic chart of 1/3 octave by tapping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material for an acoustic plate and an acoustic plate, and more particularly, to a high specific Young's modulus, a low attenuation factor, and a strong anisotropy required for an acoustic plate such as a musical instrument soundboard. The present invention relates to a composite material having a novel structure which is provided and is not affected by humidity and is excellent as a wood substitute, and an acoustic plate made of the composite material. INDUSTRIAL APPLICABILITY The present invention is widely used for a violin musical instrument, a guitar, a piano soundboard, and the like.

[0002]

2. Description of the Related Art Musical instruments such as violins and pianos are made of wood, and each member used is limited in tree species. In particular, the soundboard is the most important component that determines the performance of the musical instrument, such as the tone, and the soundboard material is then more strictly selected. As the soundboard material, a straight-grained board with a straight grain is used, and the required physical properties are generally a small density (ρ), a large specific Young's modulus (E _L / ρ) in the fiber direction (L), and a small attenuation rate ( a Q _L ^-1). That is, the material is light and has a strong waist. Wood is a porous and orthotropic structure that can be approximately represented by a structure in which cell walls and pores composed of highly elastic cellulose, which is long in the trunk direction, are arranged in parallel. . The relationship between physical properties and structure of wood has been studied in the past, but the above-mentioned properties of wood are derived from such a structure. On the other hand, the depletion of wood resources due to global environmental protection and deforestation has made it increasingly difficult to obtain high quality materials, and the development of alternative materials has become an urgent matter. However, since wood is a biological material, it is heterogeneous and highly variable, and its acoustic properties are greatly affected by humidity. Further, wood causes serious troubles in musical instrument products due to variation in material quality, dry cracking and wrapping, so that much labor and cost are required for material management and manufacturing processes.

[0003]

The present invention has been made in view of the above circumstances, and has excellent acoustic properties such as a high specific Young's modulus, a low damping rate, and a strong anisotropy required for musical instrument soundboard materials. It is intended to provide a composite material having a novel structure which is not affected by humidity and is excellent as a substitute for wood, and an acoustic plate made of the same.

[0004]

Means for Solving the Problems The present inventors have approximated the structure of wood having excellent acoustic characteristics such as frequency response characteristics and mechanical properties such as Young's modulus and internal friction provided by a wooden acoustic plate. As a result of various studies on wood substitutes,
The present invention has been completed. That is, the present invention can solve the above-described various problems caused by using wood, and can realize a high specific Young's modulus, a low damping rate, a strong anisotropy, and the like required for a musical instrument soundboard material. The present invention relates to a composite material for an acoustic plate having a novel structure and an acoustic plate using the same.

[0005] The composite material for an acoustic plate of the first invention is characterized by including a resin matrix having voids and carbon fibers arranged in the resin matrix and oriented in one direction. An acoustic plate according to a fifth aspect of the present invention is characterized by including a resin matrix having voids and carbon fibers disposed in the resin matrix and oriented in one direction. The shape, size, etc. of this acoustic plate are not particularly limited,
It is variously changed depending on the purpose and application. For example,
As the shape, a flat shape, a curved shape, a bent shape, a folded shape, other shapes, and the like can be used.

[0006] The "resin matrix having voids" refers to a base material made of a foamed resin. The foamed resin may be a closed-cell foam, an open-cell foam, or a foam having both of them, but usually, an open-cell foam is preferred for processing and molding. Further, the foaming ratio of the foam itself is set to an appropriate density as an acoustic plate (for example, about 0.38 to 0.52 g / cm3, preferably about 0.38 to 0.47 g / cm3).
Usually, the expansion ratio is 8 to 50 times, preferably 10 to 25 times. The material of the resin matrix is not particularly limited, and may be, for example, polyurethane, polyphenol, polypropylene, polyethylene, nylon, acrylic resin, or the like. Among them, polyurethane, particularly hard polyurethane, is preferable because it can be easily adjusted to an appropriate density of about 0.38 to 0.50 g / cm3.

The type of carbon fiber (including graphite fiber) (type of raw material, method of manufacturing, etc.) is not particularly limited, but PAN type is preferable. Usually, long fibers and long fibers of a monofilament are used as the carbon fibers, but short fibers or both of them can also be used. The blending amount of the carbon fiber is not particularly limited, but is preferably 3 to 20% by volume, more preferably 5 to 1% by volume based on the total volume of the matrix resin and the carbon fiber.
0% by volume, more preferably 6 to 8% by volume.

The carbon fibers may be oriented in one direction in the matrix. Also, in order to obtain a composite board that shows acoustic characteristics closer to wood, the rigidity of the front and back,
Since a laminate having high strength and a low density of the intermediate layer is preferable, it is more preferable that carbon fibers are oriented on the front and back surfaces of the matrix. Furthermore, in order to control the orientation of the carbon fibers, the carbon fibers that have been oriented and provided with a desired density distribution as appropriate with an emulsion resin or the like in advance are cured with a resin, a sheet is formed, and a foamed resin is laminated on the sheet. It may be a composite material. In this case, it is preferable to adopt a sandwich structure in which two sheets are used as the front and back layers and a foamed resin is sandwiched between the intermediate layers.

[0009] The above-mentioned composite material for an acoustic plate or an acoustic plate (hereinafter referred to as "the acoustic plate")
Also referred to as "composite material for acoustic plate". )), The density (ρ) is 0.38 to 0.52 g / cm ³ (preferably 0.38 to 0.50 g / cm 3, more preferably 0.3 to 0.50 g / cm ³ ).
8 to 0.47 g / cm3). If this density is too low, the amount of urethane resin injected is small,
Uniform formation of the matrix becomes difficult. On the other hand, if the density is too high, not only does the composite become heavier, but also the foaming pressure increases, making it difficult to uniformly orient the fibers. In particular, when it is less than 0.38 g / cm ³ , the strength is insufficient as a composite material, which is not preferable. 0.52g / c
When it exceeds m ³ , the composite is heavy and the tone is impaired. In particular, 0.38 to 0.50 g / cm ³ (especially 0.
In the case of 38 to 0.47 g / cm ³ ), the weight is light and the required balance of acoustic characteristics is excellent.

[0010] In the acoustic plate for a composite material or the like, the fiber direction of the Young's modulus E _L 9-15 (preferably 10-15)
It can be. The E _L are those affecting the frequency characteristics. In the composite material for an acoustic plate or the like, Young's modulus E _L is an index indicating the magnitude of shear deformation.
And the ratio of shear elastic modulus G _LR (E _L / G _LR ) to 5.0 to 5.0
7.0 (preferably 5.5 to 7, more preferably 6 to
7). Within this range, sufficient elasticity and low rigidity can be sufficiently ensured. Furthermore,
The specific Young's modulus E _L / ρ ratio is preferably 18 or more, preferably 20 or more, and more preferably 24 or more in terms of obtaining an acoustic plate that can withstand a large volume. The upper limit of this ratio is usually about 30. The internal friction Q _L ^-1 in the fiber direction affects the transient characteristics, and the smaller the sound is, the better it is. , More preferably 8 or less. The lower limit of this value is usually about 4. Indicating an anisotropy index,
E _L (Young's modulus in the fiber direction) / E _R (Young's modulus in the direction perpendicular to the fiber direction) is 9 to 20, preferably 10 to 20,
More preferably, it can be set to 11-20. From the above, the density (ρ) is 0.38 to 0.52 g / cm ³ , the Young's modulus E _L is 9 to 15, E _L / G _LR is 5.0 to 7.0, and E _L
/ [Rho ratio 18 to 30, Q _L ^-1 of 4 to 10 × 10 ^-3, and the E _L / E _R can be 9-20. Also, preferably, the density ([rho) a 0.38~0.50g / cm ³ (more preferably 0.38~0.47g / cm ^3), the E _L 1
0-15, E _L / G _LR is 5.0-7.0, E _L / ρ ratio is 2
0-30 (more preferably 22 to 30), 4 to a Q _L ^-1
10 × 10 ⁻³ and E _L / E _R can be 10 to 20 (more preferably 11 to 20).

Further, in the above-mentioned composite material for an acoustic plate, etc., in the frequency response characteristic diagram of the ３ octave band by tapping, at least 200 to 500 Hz, 10
Each peak (i.e., at least three peaks) may be at 00-2000 Hertz and 5000-7000 Hertz. For example, 300-500 Hertz, 1500-1700 Hertz and 5000-7000
Hertz can have each peak (ie, at least three peaks). In addition, 250-500
One peak at Hertz, 2 at 1000-3000 Hertz
And one peak at 5000-7000 Hertz (i.e., at least four peaks).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described below in Test Example 1.
This will be specifically described with reference to FIGS. (1) Production of Test Acoustic Plate According to Test Examples 1 to 5 First, the following fibers and the following urethane raw materials for a rigid urethane foam were mixed with (a) a fiber to be used, as shown in Table 1. By changing the type, (b) the volume fraction (VF) of the fibers in the matrix, and (c) the expansion ratio (that is, the density: ρ) of the urethane raw material for the rigid urethane foam to be used, as shown in Table 1, And sound plates for test having different acoustic characteristics. 1 to 5 (Test Examples 1 to 5) were produced.

The basic manufacturing process is as follows.
First, the bundled long carbon fiber bundle (sizing carbon fiber, abbreviated as “CF” in Table 1) is loosened. This carbon fiber represents a monofilament. And 3
A 0 cm square plate mold (cavity depth: 3 mm) is prepared. The carbon fibers are stuck on one surface of the upper and lower molds so as to be arranged in substantially one direction. The amount of carbon fiber to be compounded is
The amount is such that the volume ratio shown in Table 1 is obtained. Test Example 5
Was used similarly after loosening the glass fiber bundle. The following urethane raw material for rigid urethane foam is uniformly poured into the center of the lower mold. Then, the upper mold is immediately placed. A gap is provided at each of the four corners of the upper mold and the lower mold so that gas can be vented. 40 ° C,
By leaving it for 60 minutes, it is foamed and cured to form a hard foamed polyurethane containing fibers. Removed from the mold and placed on a test acoustic plate (105 × 105 × 3 mm,
To 5).

Raw materials used in each test example (see Table 1) (a) "CF-1" (used in test examples 1 to 3, apparent density: 1.81 g / cm3); Sizing carbon fiber, manufactured by Mitsubishi Rayon Co., Ltd., trade name: "TR50S
12L "(b)" CF-2 "; (Used in Test Example 4, apparent density;
1.95 g / cm3); long carbon fiber (sizing carbon fiber, manufactured by Mitsubishi Rayon Co., Ltd .; (c) "GF"; (used in Test Example 5, apparent density; 2.
38 g / cm3); long glass fiber (E glass), manufactured by Asahi Glass Co., Ltd. (d) "FP-1 to 5"; liquids A and B shown below are used. Each different expansion ratio was prepared by the following method. (I) [Solution A]; polyol: 100 parts by weight (hereinafter, simply referred to as "part"), foam stabilizer: 2 parts, catalyst: 1.5 parts,
Blowing agent (water): 1-2 parts, [B liquid]; Crude MDI,
index; 115), [solution A / solution B] = 100/13.
5 (Note that this mixed solution has a viscosity that flows when left to stand. The reaction is slow due to low activity for ensuring workability.) Propylene oxide is reacted with sucrose and triethanolamine as the polyol. A polyether polyol having a hydroxyl value of 300, a silicone foam stabilizer (trade name “SH-193” manufactured by Toray Silicone Co., Ltd.) as the foam stabilizer, and N, N-dimethylcyclohexylamine as a catalyst were used.

(Ii) Adjustment of Expansion Ratio Adjustment of expansion ratio, ie, density, in each of the following test examples was performed as follows. In Test Example 1, 20.9 parts by weight of carbon fiber was placed in a mold, and 59.5 parts by weight of the total amount of liquids A and B was injected, and then the mold was quickly closed. In Test Example 2,
In Test Example 1, the injection amounts A and B were increased to 55.1 parts by weight in total. In Test Example 3, the amount of carbon fibers was increased to 21.6 parts by weight under the conditions of Test Example 2 described above. In Test Example 4, Test Example 2
, The total injection amount of the liquids A and B was further increased to 81.8 parts by weight. In Test Example 5, 20.8 parts by weight of glass fiber was placed in a mold, and 32.3 parts by weight of the total amount of liquids A and B was injected, and then the mold was quickly closed.

Test Example 6 (No. 6) shown in Tables 1 and 2
For comparison, Sitka spruce for soundboard (Sp) was used for comparison (see FIGS. 2 and 4 to 6), and the same shape was used as a test sample. This Sitka spruce (Sp) was used for a sound board such as a violin or a piano. FIG. 2 shows maple wood (M
ap) results are also shown. In Table 1, "VF" indicates the volume fraction, the subscript "L" indicates the fiber direction, "R" indicates the direction orthogonal to the fiber, and "t" indicates the value calculated by the compound rule.
The physical properties of rigid urethane foam (FP) are shown in Fig. 1.
(Test Examples 1 to 2, 5) and FIG. 3 (Test Examples 3 to 4). Further, Ef shown in the “Note” column of Table 1,
Em is a value in the case of ideal orientation for obtaining a measured value, and is obtained by calculation.

(2) Performance evaluation of Test Examples 1 to 6
And Young's modulus), use the fiber bundle as it is.
To improve the physical properties (density and Young's modulus) of the matrix material
About 3 (thickness) x 20 (width) x 150 (length) m
The frequency characteristics and physical properties of the composite material (Y
Modulus, shear modulus, deflection internal friction (Q _L ^-1), Within shear
Partial friction (Q_t ^-1) Is 3 (thickness) x 150
Cut out into a square plate (width) x 150 (length) mm,
The performance was evaluated by the following test. Table 1 shows these results.
2 and FIGS. 1 to 6).

[0018]

[Table 1]

[0019]

[Table 2]

The performance evaluation items are shown in Tables 1 and 2. That is, (1) fiber density (ρ) and Young's modulus (E), (2) density (ρ) and Young's modulus (E) of various matrix materials having different foaming rates, and (3) frequency characteristics of composite material , Young's modulus (E), shear modulus (G), the deflection internal friction (Q _L ^-1), a shear internal friction (Q _t ^-1). In addition, the subscript "L" is a fiber direction, "R" is a direction orthogonal to the fiber,
“T” indicates a value calculated by the compound rule. “Ρ” of the fiber was measured by Archimedes' method, and “E” was measured by using Leo Vibron (manufactured by Orientec). "Frequency characteristics" means that four corners are set horizontally on a nylon thread so that the periphery of the sample plate is free, and a small iron piece attached to the lower surface of the center is a sine wave with a frequency of 0.1 to 10 kHz by an electromagnetic transducer. , And the amplitude of the response vibration at each frequency was measured by detecting with a microphone placed 2 mm above the center. The “dynamic Young's modulus E” and the “shear modulus G” of the sample plate were obtained by calculating the resonance frequency f ₀ (Hz) from the resonance curve obtained by the free deflection at both ends and the return forced vibration method, and the following equation. .

[0021]

(Equation 1)

Here, “ρ” is the density, and “l” is the sample plate L
The length in the direction, “w” is the length in the sample plate R direction, “t” is the thickness of the sample plate, and “m” is a constant that depends on the vibration mode and is 4.730 in the free fundamental vibration at both ends. The internal friction Q ^-1 was calculated from the following equation in which the half width Δf was obtained from the resonance curve.

[0023]

(Equation 2)

(3) Effect of Embodiment First, the relationship between ρ and E (and G) is shown in FIGS.
As shown in these figures, a linear relationship was obtained between the two with a high correlation. A composite material was designed using this and the measurement results of fiber properties. The difference between the measured value and the calculated values in Table 1, _{i.e., △ E L / E LT,} △ ratio E _R / E _RT is, in Test Examples 1, 3 and 5, as large as about 50-90%, It is considered that the fibers were not sufficiently dispersed. On the other hand, Test Examples 2 and 4
Since the ratio is relatively small, about 25-36%, it is considered that the test article is not satisfactory but has relatively good fiber dispersion. Furthermore, E _f in the case of the ideal orientation for obtaining a measured value, the E _m value in the case of Test Examples 1, 2 and 5,
It was calculated and shown in the Note column of Table 1. These indicate that the unidirectional orientation and uniform dispersion of the fibers are not sufficiently successful.

As described above, although the degree of dispersion of the fibers differs depending on each test example, the following can be said from the results of Tables 1 and 2. That is, in Test Example 5 (also referred to as No. 5), glass fiber was used, ρ was similarly sufficiently small, and the anisotropy (E _L / E _R ) was smaller than Sp as a comparative product. S
about the same as the p but, E _L is as small as 3.25, moreover EL / ρ also 7.83 and small, not out enough acoustic performance. Test Example 1, compared with Sp as a comparative product, [rho and degree of anisotropy is sufficiently good, but only slightly smaller EL / ρ, E _L is as small as 7.74, sufficient in this respect No sound performance.

[0026] Test Example 3, compared with Sp as a comparative product, [rho and although different Katado is good enough, E _L is as small as 6.28, so even EL / [rho small as 14.3,
In this respect, sufficient acoustic performance has not been obtained. But,
Q _L ^-1 affecting the transient characteristics is 5.01 × 10 ^−3, which is smaller than that of Sp (9.99 × 10 ⁻³ ), indicating excellent performance. Further, since E _L / G _LR is equal to Sp, the level drop in the high frequency range is almost the same in the frequency characteristics. This is because, when E _L / G _LR is large, the influence of the shear deformation in the vibration of the higher-order mode is greatly affected, and the level drop in the high frequency range becomes large. FIGS. 4 and 6 show the results of frequency response characteristics of 1/3 octave hand by tapping for Test Example 3 and Sp. This Map is used for the back plate of the violin, and is required to have properties opposite to those of the front plate. The frequency characteristic of Sp in FIG.
The characteristic feature is that the widths of the first and second peaks indicating the resonance frequency in each of the fundamental modes in the R direction and the L direction are wide, and the power level drops greatly in a wide range from around 1 kHz. In the composite material of Test Example 3, Sp
Although both peaks are lower and largely shifted to lower frequencies as a whole, the widths of the peaks are almost the same. The level decrease in the high frequency range is slightly smaller than Sp. And
The composites of Test Example 3 were 300 to 400 Hz and 600
At 0 Hz, it shifts slightly lower than Sp to 100
Although there are two peaks at 0 to 2000 Hz, they show almost the same peak as Sp, show a similar peak spectrum as a whole, and show high potential as a substitute for wood for soundboard.

[0027] Test Example 4, compared with the Sp as a comparative product, ρ is 0.499 (Sp: 0.447) and is a large, other performance, ie, E _L is almost equal, different Orientation (16.9, Sp = 10.8) is better,
EL / ρ is also substantially equivalent to 22.3 (Sp: 26.
1). Further, Q _L ^-1 is 6.49 × 10 ^−3, which is smaller than that of Sp (9.99 × 10 ⁻³ ), indicating excellent performance. Also, E _L / G _LR is smaller than Sp,
The level drop at high frequencies is smaller. Also,
FIGS. 5 and 6 show the results of frequency response characteristics of 1/3 octave hand by tapping for Test Example 4 and Sp. According to this result, the composite material of Test Example 4 was 300 to
It shifts slightly below Sp at 400 Hz and 6000 Hz, and 2 at 1000-2000 Hz.
Although there were several peaks, it showed a peak almost similar to Sp, showing a similar peak spectrum as a whole, indicating a high possibility as a substitute for wood for soundboard. From the above,
This test example product shows almost the same performance as the Sp material that shows excellent performance, and there is also a performance that is even better,
As a whole, it can be sufficiently used as a substitute for the Sp material.

[0028] Test Example 2, compared with Sp as comparative product, [rho is 0.434 (Sp: 0.447), E L is 1
1.5 (Sp: 11.6), anisotropy of 18.6 (Sp
= 10.8), EL / ρ is 26.5 (Sp: 26.1)
And are almost the same, but rather show more favorable performance. FIG. 2 shows the frequency response characteristics of a 1/3 octave hand by tapping for Test Example 2, Sp and Map. According to these results, the composite material of Test Example 2 exhibited characteristics in which Sp was shifted to a higher range at substantially the same level, indicating a high possibility as a substitute for soundboard wood. Further, in Test Examples 1, 3, and 4, if the dispersion of the fibers is made more uniform, Test Example 2, ie, S
It is considered that there is a possibility that a performance equal to or higher than p may be obtained.

As described above, according to the above-mentioned composite material, ρ is 0.1.
385-0.469 g / cm ³ , E _L 10.1-14.
9Mpa, Q _L ^-1 can be made reliably with excellent performance required of 5.4~7.2 × 10 ^-3. In addition, because it is made of resin instead of wooden Sp material, which is a very good soundboard for musical instruments, it is not affected by moisture,
In addition, stable quality products can be easily and reliably manufactured. Furthermore, it is fully conceivable to obtain a composite material with even better acoustic effects by contemplating even more uniform dispersion of the fibers.

[0030]

The composite material for an acoustic plate and the acoustic plate of the present invention are:
It has high specific Young's modulus, low damping rate, strong anisotropy and strong anisotropy required for acoustic boards such as musical instrument soundboards, and is not affected by humidity. It is very good. In addition, when the composite material of the present invention is used for a string instrument front plate, a piano soundboard, and the like, material management, a manufacturing process can be greatly simplified, and material quality can be increased in accuracy. INDUSTRIAL APPLICABILITY The present invention is widely used for a violin musical instrument, a guitar, a piano soundboard, and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the density (ρ) and the Young's modulus (E) of a composite material according to Test Examples 1 and 2.

FIG. 2 is a spectrum showing a frequency response characteristic result of a 1/3 octave hand by tapping in Test Example 2, Map and Sp.

FIG. 3 shows the density (ρ) of the composite material according to Test Examples 3 and 4.
6 is a graph showing the relationship between the shear modulus (G) or the Young's modulus (E).

FIG. 4 is a spectrum showing frequency response characteristics results in Test Example 3 and Sp.

FIG. 5 is a spectrum showing frequency response characteristics results in Test Example 4 and Sp.

FIG. 6 is a spectrum showing a result of frequency response characteristics of a 1/3 octave hand by tapping in Test Examples 3, 4 and Sp.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 101/00 G10D 3/02 G10D 3/02 B29C 67/14 PW (72) Inventor Akiaki Ono Naka, Kakamigahara-shi, Gifu Prefecture 1-143 Kotogaokacho F-term (reference) 4F072 AA04 AA07 AA08 AB10 AB18 AB22 AD04 AD09 AD13 AD43 AD44 AD56 AK05 AK20 AL01 4F205 AA42 AD02 AD16 AG20 AH81 HA10 HA22 HA33 HA37 HB01 HC02 HC17 4J002 AA001 BB031 CB121 BB121 BB121 001 FA046 FA091 FD016 GC00 5D002 CC02 DD08 DD09

Claims (8)

[Claims] 1. A composite material for an acoustic plate, comprising: a resin matrix having voids; and carbon fibers disposed in the resin matrix and oriented in one direction. Wherein a density of 0.38~0.52g / cm ^3, the fiber direction of the Young's modulus E _L is 9～15GPa, the ratio of the Young's modulus E _L and shear modulus G _LR (E _L / G _LR )
2. The composite material for an acoustic plate according to claim 1, wherein a value of the composite material is 5.0 to 7.0. Wherein E _L / [rho ratios 18-30, the fiber direction of the internal friction Q _L ^-1 is 4 to 10 × 10 ^-3, the E _L / E _R (direction of the Young's modulus perpendicular to the fiber direction) The composite material for an acoustic plate according to any one of claims 9 to 20. 4. In a frequency response characteristic diagram of a オ ク タ octave band by tapping, at least 200 to 5
00 Hertz, 1000-2000 Hertz and 5000-
The composite material for an acoustic plate according to any one of claims 1 to 3, comprising a peak at 7000 Hz. 5. An acoustic plate comprising: a resin matrix having voids; and carbon fibers disposed in the resin matrix and oriented in one direction. Wherein a density of 0.38~0.52g / cm ^3, the fiber direction of the Young's modulus E _L is 9～15GPa, the ratio of the Young's modulus E _L and shear modulus G _LR (E _L / G _LR )
6. The acoustic plate according to claim 5, wherein is 5.0 to 7.0. 7. An E _L / ρ ratio of 18 to 30, an internal friction Q _L ^{-1 in the} fiber direction of 4 to 10 × 10 ^-3 , and an E _L / E _R (Young's modulus in a direction perpendicular to the fiber direction). The acoustic plate according to claim 6, wherein 8. In a frequency response characteristic diagram of a 1/3 octave band by tapping, at least 200 to 5
00 Hertz, 1000-2000 Hertz and 5000-
The acoustic plate according to any one of claims 5 to 7, comprising each peak at 7000 Hertz.