JPH08216114A - Manufacture of acoustic material - Google Patents

Abstract

PURPOSE: To manufacture an acoustic material which is applied for the use as an interior finish material of the acoustic site of various musical instrument or a concert hall by chemically and physically treating a low specific weight material. CONSTITUTION: A low-specific-weight veneer obtained by low-specific-weight timber is impregnated with low-molecular-weight thermosetting resin to obtain resin-impregnated veneer. Then, one resin-impregnated veneer or a plurality of resin-impregnated veneers obtained by matching fiber directions and laminating are pressed and heated to obtain a consolidated resin treated material. The treated material is used as a front layer material, the low-specific-weight veneer obtained from the low-specific-weight timer is used as a core layer material, and the veneer and the core material are laminated, then pressed and heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acoustic material suitable for use in various acoustic parts such as a piano, a guitar, a violin, and interior materials such as a concert hall.

[0002]

2. Description of the Related Art The protection of forests is an essential issue for the global environment, and there is an urgent need to establish an ideal circulation system in forest utilization. In particular, Japan consumes 60% of its wood consumption despite the fact that 70% of its land is covered with forests.
Nearly 80% depend on foreign forest resources, and improvements in such consumption patterns are also strongly demanded by other countries.

Under such circumstances, the future of the musical instrument industry in Japan, which relies on importing most of the wood resources for musical instruments, is the most alarming one. In addition, it is difficult to secure good quality musical instrument materials, such as depletion of high-quality German spruce due to acid rain, felling of Brazilian rosewood materials based on forest protection, export ban, etc. There is. In fact, the Brazilian rosewood, which has been used as the back plate of the finest guitars until now, is prohibited from export from the country of origin, is no longer available, and is also used in the soundboards of high-end guitars, pianos and violins. As for spruce trees, due to the effects of acid rain, the production of the spruce trees has declined along with the deterioration of the materials.

By the way, spruce wood such as German spruce and red spruce has acoustic characteristics different from those of other woods. This is a property that can be understood by hitting wood,
The violin maker selects good wood from the spruce genus by striking wood. Therefore, when the present inventor examined the relationship between the result determined by the violin maker and the acoustic properties of wood, the spruce wood, especially good wood, had Young's modulus divided by specific gravity in the grain direction. It was found that the value of specific dynamic Young's modulus (hereinafter sometimes simply referred to as the specific Young's modulus) is large and the value of internal friction is small. Since a material having a higher Young's modulus is less likely to be deformed, a good material is lighter (having a smaller specific gravity) but is less likely to be deformed, that is, it can withstand a force received from a string by sandwiching a piece. Further, a large specific dynamic Young's modulus indicates that the speed of sound transmitted through the wood is large, and this is also related to the fact that the wood easily shakes due to the small specific gravity. On the other hand, the internal friction is related to the ease of absorbing vibration, and the smaller the value of the wood, the smaller the vibration friction inside the wood and the less the vibration energy absorbed by the wood. A good material is easy to vibrate and hard to absorb the vibration. That is, it is excellent in the efficiency of converting the vibration given from the strings into sound. From this, it is considered that the sound quality of the musical instrument is improved if the specific Young's modulus or the internal friction can be further reduced without increasing the specific gravity of the soundboard wood. Furthermore, if a high specific gravity material (specific gravity of about 0.7 to 1.1) is obtained, it is considered to be a material for a back plate of a guitar or a violin.

As described above, in the acoustic characteristics of the string board soundboard material, the properties required of the soundboard material greatly differ depending on the musical instrument and the part to be used, and in the case of the violin, the front plate of the guitar and the piano soundboard, the German spruce and Sitka. A soundboard material having low specific gravity, high specific elasticity and low damping such as spruce is used.

[0006]

On the other hand, turning to Japan's forest resources, for example, cedar wood that has undergone large-scale afforestation after the war has low strength and softness due to its low specific gravity. Many of them are still abandoned in the forest because they have poor durability and no effective use with high added value has been found. On the other hand, the production of pianos, guitars, or violins is already forced to use soundboard materials of poor quality, which could lead to serious problems involving the entire culture of musical instruments in the near future. Therefore, in order to maintain the level of culture related to musical instruments, it is desirable to develop new wood-based acoustic materials based on renewable forest resources.

On the other hand, the present inventor has the following knowledge. In other words, regarding specific dynamic Young's modulus (specific elasticity), the advantage of wood as a musical instrument material is that it has a high specific elasticity due to its cell wall structure and porous structure. The specific Young's modulus increases in the direction from the center to the outer circumference of the tree), but it is difficult to increase in the fiber direction (the direction along the grain). However, if a highly elastic material is arranged in the surface layer part and a material having a low specific gravity is arranged in the core layer part, the composite Young's modulus in the fiber direction can be increased.

Regarding the internal friction (tan δ), the chemical treatment for reducing the interaction between the wood constituents can reduce the internal friction without increasing the specific gravity so much. In the treatment using a thermosetting resin having a molecular weight of about 300, for example, a phenol resin, the internal friction is 30 to 40 in the fiber direction.
%, In the radial direction perpendicular thereto, it can be reduced by 40 to 50%. Therefore, when a material impregnated with a low molecular weight thermosetting resin is used as the surface layer material, the internal friction can be efficiently reduced.

Further, since the frequency characteristic of the radiated sound is deeply related to the timbre of the musical instrument, the high cut property (cutting of high frequency components) of the soundboard material is important. The frequency characteristic of the radiated sound can be controlled by controlling the frequency dependence of the internal friction and controlling the E / κG value at the material stage. Therefore, the formation of a laminated structure using the high-elasticity material as the surface layer material and the low specific gravity material as the core layer material is useful for increasing the E / κG value (giving high-cut property).

The present invention has been made based on the above findings in view of the above conventional problems, and an object of the present invention is to provide a low specific gravity material with chemical and physical treatments to produce acoustic parts of various musical instruments. Another object of the present invention is to provide a method of manufacturing an acoustic material that can be suitably used as an interior material for a concert hall or the like.

[0011]

In order to solve the above problems, the invention of claim 1 is a resin-impregnated veneer obtained by impregnating a low specific gravity veneer obtained from low specific gravity wood with a thermosetting resin having a low molecular weight. After that, one resin-impregnated veneer or a plurality of resin-impregnated veneers stacked with their fiber directions aligned is pressed and heated to obtain a consolidated resin-treated material, which is used as a surface layer material. It is characterized in that a low specific gravity veneer obtained from low specific gravity wood is used as a core layer material, these are compositely laminated, and then compression heating is performed.

According to the second aspect of the present invention, a low specific gravity veneer obtained from low specific gravity wood is subjected to a consolidation heat treatment in a closed state to obtain a consolidation heat treated veneer, after which one consolidation heat treated veneer or fiber direction is applied. A plurality of consolidated heat-treated veneers laminated together is used as a heat-treated compacted material, this heat-treated consolidated material is used as a surface layer material, and a low-density specific veneer obtained from low-density wood is used as a core layer material. It is characterized by tightening and heating.

The low specific gravity wood according to claim 1 or 2 is preferably cedar wood.

[0014]

According to the invention of claim 1, a low-specific-gravity veneer obtained from a low-specific-gravity wood is impregnated with a low-molecular-weight thermosetting resin to obtain a resin-impregnated veneer. Board,
Alternatively, a plurality of resin-impregnated veneers stacked with their fiber directions aligned are pressed and heated to obtain a consolidated resin-treated material, and this consolidated resin-treated material is used as the surface layer material, and a low specific gravity veneer obtained from low specific gravity wood is used as the core. As a layer material, these are compositely laminated and then pressed and heated, and in the invention of claim 2, a low specific gravity veneer obtained from a low specific gravity wood is subjected to a consolidation heat treatment in a closed state to perform a consolidation heat treatment veneer. After this, one consolidation heat treated veneer,
Alternatively, a plurality of consolidation heat-treated veneers laminated with the fiber directions aligned is used as a consolidation heat treatment material, the consolidation heat treatment material is used as a surface layer material, and a low specific gravity veneer obtained from low specific gravity wood is used as a core layer material, and these are composite laminated. Then, compression heating is performed, and in each case, a composite of a low specific gravity veneer (core layer material) and a consolidated resin treated material (surface layer material) made from unused wood such as cedar wood By laminating or composite laminating of low specific gravity veneer and consolidated heat-treated material (surface layer material), it becomes possible to obtain a good material having a low specific gravity comparable to that of German spruce of the highest grade and a high specific dynamic Young's modulus. Therefore, Japan's forest resources can be effectively used, and by changing the pressure heating condition,
The specific gravity of the obtained material can be easily changed, and
Various acoustic characteristics can be provided by changing the type of thermosetting resin to be impregnated or by changing the conditions of consolidation heat treatment in a closed state, and acoustics that can be used for the acoustic parts of various musical instruments. The material can be easily manufactured.

The present invention will be described below from the viewpoint of material design.
A method of manufacturing a musical instrument soundboard material by a low molecular weight phenol resin impregnation consolidation treatment using an unused low specific gravity wood as a raw material,
A method of manufacturing a musical instrument soundboard material by a consolidation heat treatment in a closed system will be separately described. The low-specific-gravity wood used in the present invention is not particularly limited in its type as long as its specific gravity is 0.38 or less, but from the viewpoint of effectively utilizing the forest resources of unused wood, Low specific gravity wood is preferred. The low specific gravity wood is 15 years old or more, preferably 20 years old or more. If you are under 15th grade, the acoustic characteristics will be inferior,
Further, a low specific gravity veneer having a small log diameter and a large surface area cannot be obtained.

First, a method of manufacturing a musical instrument soundboard material by a low molecular weight phenol resin impregnation consolidation treatment will be described. A rotary veneer (low specific gravity veneer) is manufactured from low specific gravity wood by using, for example, a rotary lace. The thickness is about 1 to 3 mm. Next, this rotary veneer is immersed in a resin solution tank to impregnate it with a thermosetting resin. A phenol resin can be used as the thermosetting resin. As the thermosetting resin, a thermosetting resin such as a melamine resin can be used as long as it has an average molecular weight of about 200 to 800. The average molecular weight is
Those below 200 are hard to obtain and have an average molecular weight of 8
This is because if it exceeds about 00 and becomes about 1000, it cannot penetrate into the cell wall of the rotary veneer, the improvement of the acoustic characteristics cannot be seen, and the effect of impregnating the resin is reduced. The concentration of the thermosetting resin is preferably 5 to 10 wt% in order to reduce the weight increase due to the treatment.

The veneer impregnated with the thermosetting resin is air-dried, naturally dried or the like to reduce the water content of the veneer to 10 to 20 wt% to produce a resin-impregnated veneer. Next, one resin-impregnated veneer or a plurality of resin-impregnated veneers stacked with their fiber directions aligned is pressed and heated under certain conditions to produce a consolidated resin-treated material having a predetermined thickness. In this case, the layers are laminated so that the back cracks are on the inside.

Thereafter, the compacted resin treated material is used as a surface layer material, and a low specific gravity veneer obtained from a cedar material having a specific gravity of about 0.35 to 0.38 is used as a core layer material, and these are compositely laminated. At this time, several core layer materials and surface layer materials are piled up so as to have an arbitrary thickness, and they are adhered with an adhesive, followed by pressure heating. Here, the specific gravity of the core layer material is preferably 0.15 to 0.
38, the specific gravity of the laminated material is 0.5 or less, preferably 0.4 to
It is 0.48. In addition, it is important to select the surface layer material in consideration of availability, cost, and increase in the total weight. Further, by stacking the core layer material and the surface layer material so that the fiber directions are aligned, the acoustic characteristics are further improved. As the adhesive for bonding the compacted resin treated material and the low specific gravity veneer, an isocyanate resin adhesive or other thermosetting resin adhesive (phenol resin, urea resin, epoxy resin, resorcinol resin, etc.) is used. It is possible.

Next, a method of manufacturing a musical instrument soundboard material by consolidation heat treatment in a closed system will be described. First, a 2 mm-thick low specific gravity veneer obtained from cedar wood or the like is pressed and heated under constant conditions to produce a consolidated heat-treated veneer. Then, one consolidation heat-treated veneer or a plurality of consolidation heat-treated veneers laminated in the fiber direction is used as a consolidation heat-treated material, and this consolidation heat-treated material is used as a surface layer material, and the specific gravity is about 0.35 to 0.38. A low specific gravity veneer obtained from cedar wood is used as a core layer material, and these are stacked with an adhesive, and heated under pressure under constant conditions. Here, when laminating the surface layer material and the core layer material, several consolidation heat treatment single plates are stacked so that the composite material of the surface layer material and the core layer material has an arbitrary thickness. Further, by stacking the core layer material and the surface layer material so that the fiber directions are aligned, the acoustic characteristics are further improved. An isocyanate resin adhesive or another thermosetting resin adhesive (phenolic resin, urea resin, epoxy resin, resorcinol resin, etc.) can be used as the adhesive for bonding the heat-treated compaction material and the low specific gravity veneer. Is.

Next, the present invention will be specifically described based on examples. (Example 1) A low specific gravity veneer having a thickness of 2 mm and a specific gravity of 0.32 was obtained from a 20th grade cedar wood by rotary lace. Then, this low specific gravity veneer was immersed in a 5% concentration low molecular weight phenolic resin solution (average molecular weight 300) for 1 week, air-dried for 1 week, and heated at 70 ° C. for 12 hours to obtain a resin-impregnated veneer. . Furthermore, one resin-impregnated veneer is heated to 170 ° C,
Pressing and heating is performed at a pressing pressure of 50 kgf / cm ² and a hot pressing time of 15 minutes. The thickness is regulated by the distance bar. Then
After unloading the pressure, it was heated in a dryer at 170 ° C. for 1 hour to produce a low molecular weight phenol resin consolidation treatment material having a thickness of 0.99 mm.

After that, the low molecular weight phenol resin impregnated and consolidated material was used as a surface layer material, and a cedar siding plate having a thickness of 6.01 mm was used as a core layer material, and the surface layer material and the core layer material were aligned in the fiber direction and isocyanate bonded. Stack through the agent, then
The laminated material having a thickness of 7.96 mm was manufactured by pressing and heating at a pressing pressure of 5 kgf / cm ² , a hot plate temperature of 170 ° C., and a hot pressing time of 15 minutes.

The acoustic properties of this laminated material were measured by the both end free flexural vibration method described later. Measurement atmosphere is 20
C, 65% R.C. H. The sample material had a width of 40 mm and a length of 250 mm, and each of the samples was once completely dried and then conditioned under the atmosphere for 2 weeks or more and then subjected to the measurement. The results are shown in Table 1.

[0023]

[Table 1]

(Example 2) Two resin-impregnated veneers were produced in the same manner as in Example 1, and these two resin-impregnated veneers were laminated in the same fiber direction, and the same as in Example 1. A low-molecular-weight phenol resin-impregnated consolidation-treated material having a thickness of 1.15 mm was manufactured under pressure heating conditions. This low molecular weight phenolic resin-impregnated and consolidated material is used as a surface layer material, and a cedar slat plate having a thickness of 5.97 mm is used as a core layer material, and the surface layer material and the core layer material are stacked with isocyanate adhesives aligned in the fiber direction. Then, a laminated material having a thickness of 8.19 mm was manufactured under the same pressing and heating conditions as in Example 1. The acoustic properties of this laminated material were measured under the same conditions as in Example 1. Table 2 shows the results.

[0025]

[Table 2]

Here, as in the second embodiment, the specific gravity is 0.3.
, A material having a specific dynamic Young's modulus of about 20 GPa for the core layer,
When a material having a specific gravity of 1.0 and a specific dynamic Young's modulus of 20 GPa is used for the surface layer, the thickness ratio of the surface layer material to the core layer material (the surface layer material is the upper layer and the lower layer. The ratio is
When the thickness ratio of the upper layer or the lower layer material to the core layer is about 0.2, the relative dynamic Young's modulus of the laminated material becomes the maximum value of 30 GPa. However, in this case, the specific gravity of the laminated material is about 0.5. Here, as the piano soundboard material or the guitar surface board material, etc., as in the first embodiment,
The thickness ratio is about 0.1, and the specific gravity of the laminated material is 0.4 to 0.
When it is set to about 45, the specific dynamic Young's modulus decreases to 28 GPa, but the specific gravity and the specific dynamic Young's modulus almost equal to those of the actual German spruce wood are obtained, which is useful when considering the acoustic conversion efficiency. . (Example 3) Three resin-impregnated veneers were produced in the same manner as in Example 1, and these three resin-impregnated veneers were laminated with their fiber directions aligned, and the same compression heating as in Example 1 was performed. Thickness of 2.3
An 8 mm low molecular weight phenolic resin-impregnated consolidation material was obtained. This low molecular weight phenolic resin-impregnated and consolidated material is used as a surface layer material, and a 6.03 mm-thick cedar siding plate is used as a core layer material, and the surface layer material and the core layer material are stacked with an isocyanate adhesive in the same fiber direction. Then, a laminated material having a thickness of 10.25 mm was manufactured under the same pressing and heating conditions as in Example 1. The acoustic properties of this laminated material were measured under the same conditions as in Example 1. The results are shown in Table 3.

[0027]

[Table 3]

(Example 4) A veneer having a thickness of 2 mm was subjected to consolidation heat treatment under the conditions of a pressure of 7.1 kgf / cm ² , a heating plate temperature of 180 ° C and a heating time of 15 minutes in a closed state.
Then, after releasing the hermetically closed state, the plate was further heated by pressing for 30 minutes to produce a single 0.86 mm thick consolidated heat-treated plate (consolidated heat-treated material). After that, this consolidated heat-treated veneer was used as a surface layer material, and a cedar-grained board having a thickness of 5.92 mm was used as a core layer material, and the surface layer material and the core layer material were stacked in the fiber direction in alignment with an isocyanate adhesive. , Clamping pressure 5kg
The laminated material having a thickness of 7.49 mm was manufactured by pressing and heating at f / cm ² , a hot plate temperature of 170 ° C., and a hot pressing time of 15 minutes. The acoustic properties of this laminated material were measured under the same conditions as in Example 1.
The results are shown in Table 4.

[0029]

[Table 4]

(Embodiment 5) Two consolidation heat-treated veneers were produced in the same manner as in Example 4, and the two consolidation heat-treated veneers were laminated with their fiber directions aligned to each other. A compacted heat-treated material having a thickness of 1.71 mm was obtained under the pressure heating condition. Next, this consolidated heat-treated material was used as the surface layer material, and the thickness was 5.77 mm.
Using the cedar slab of No. 2 as the core layer material, the surface layer material and the core layer material are stacked with isocyanate adhesives aligned in the fiber direction, and then the thickness is set under the same pressing and heating conditions as in Example 4.
A 03 mm laminated material was produced. The acoustic properties of this laminated material were measured under the same conditions as in Example 1. The results are shown in Table 5.

[0031]

[Table 5]

(Embodiment 6) Three cedar grain plates having a thickness of about 2.0 mm are stacked and adhered in the upper and lower three layers so that the fiber directions are orthogonal to each other.
A sheet of plywood was produced. Using this plywood as the core layer material, Example 4
Using the 0.99 mm thick consolidated heat-treated material produced by the same method as the surface layer material, the core layer material and the surface layer material were stacked with isocyanate adhesives aligned in the fiber direction, and then the same as in Example 4. A laminated material having a thickness of 7.96 mm was manufactured under pressure heating conditions. The acoustic properties of this laminated material were measured under the same conditions as in Example 1. The results are shown in Table 6. In this embodiment,
Since the core layer material is composed of three cedar slabs and the three cedar slat plates are laminated so that the fiber directions are orthogonal to each other, it is resistant to cracking and dimensional stability is further improved. understood.

[0033]

[Table 6]

(Comparative Example) Three 3.0 mm thick cedar rotary veneers were laminated with their fiber directions orthogonal to each other to obtain a 9.0 mm thick plywood. The acoustic properties of this plywood were measured under the same conditions as in Example 1. The results are shown in Table 7. In this comparative example, the low molecular weight phenolic resin impregnated consolidation treatment method and the consolidation heat treatment method in a closed system as shown in the examples of the present invention are not adopted, and the relative dynamic Young's modulus of the laminated material is It was found to be as low as 14.0 GPa. The specific dynamic Young's modulus and internal friction in the direction perpendicular to the fiber direction of the core layer material could not be measured.

[0035]

[Table 7]

On the other hand, when the acoustic characteristics of the German spruce for violin were measured, the specific gravity was 0.34 to 0.47, and the specific dynamic Young's modulus (× 10 GPa) was 2 in the fiber direction (the direction along the grain). .26 to 2.94, tangential direction (direction orthogonal to wood grain) is 0.14 to 0.22, and fiber direction is 6.10 to 7.6 with respect to internal friction (× 10 ⁻³ ).
2 and the measurement result that the tangential direction was 17 to 19 was obtained.

Further, when the E / κG value showing the high cut property of the conventional instrument soundboard material was measured, it was “25” for the conventional soundboard, “18” for the cedar wood, and “20” for the laminated material of the comparative example. It was found that the value was "25" in German spruce, whereas it was increased to "28" in the musical instrument soundboard material manufactured in this example. As described above, in the embodiments of the present invention, the musical instrument soundboard material made of cedar wood is not so good in acoustic properties as German spruce which is finally used in high-grade guitar, piano and violin soundboards. It can be seen that the cedar material can be suitably used as an acoustic material by subjecting the cedar material to chemical treatment and physical treatment.

The specific Young's modulus and the internal friction were determined by the flexural vibration method at both ends as shown below. That is, the instrument soundboard material obtained in the example of the present invention was cut into a sample having a width of 40 mm and a length of 250 mm. After the sample was completely dried, it was kept at 20 ° C. and 65% R.C. for 2 weeks or more.
H. Measurement is performed after adjusting the humidity in the atmosphere. As this sample, a rod-shaped test piece that does not easily generate torsional vibration is used, and the sample is supported as accurately as possible by a silk thread or a cotton thread at a vibration node position corresponding to each mode. The signal from the oscillator is amplified by the power amplifier and input to the electromagnet. The sample is electromagnetically excited through a thin iron piece attached to the sample. The vibration response of the sample is detected at one end of the sample using a non-contact displacement meter so as not to disturb the vibration of the sample. While changing the frequency of the oscillator, the frequency at which the maximum amplitude (peak level) is obtained is searched for, and this is used as the resonance frequency.

The specific Young's modulus (E / γ) is obtained from the resonance frequency ( _fr ) and the sample shape by the following first equation. f _r = m _n ² h (E / γ) ^1/2 / (4 × 3 ^1/2 πL ² ) ... (1) m _n : a constant determined by the mode order (n), m ₁ is 4.7
3, m ₂ is 7.8 53, and when n> 2, (2n + 1) π / 2 L: sample length (cm) h: sample thickness (cm) Subsequently, excitation is stopped at the resonance point and the attenuation waveform is spectrum. The peak level value is obtained by performing Fourier transform on the waveform storage memory of the analyzer and using the spectrum analysis function.
The decay waveform is moved at regular intervals, and the changes in the peak level value accompanying it are read. A regression line equation is obtained for the relationship between the elapsed time and the peak level value, and the time T (sec) required for the peak level value to decrease by 6.02
Calculate (time when the vibration amplitude becomes half). Half time T
Then, the logarithmic attenuation rate (λ) is calculated from the resonance frequency ( _fr ) using the following second equation.

[0040] λ = 0.6932 / (T × f r) ...... (2) internal friction logarithmic decay rate (λ) was deleted in π (tanδ)
Ask for. In addition, the dimensional stability is as follows. H. Under the atmosphere of 2
It was evaluated by measuring the swelling ratio in the direction orthogonal to the fiber direction of the sample after conditioning the humidity for a week or more.

[0041]

As described above, in the method for producing an acoustic material according to the invention of claim 1, a low specific gravity veneer obtained from low specific gravity wood is impregnated with a low molecular weight thermosetting resin to form a resin impregnated veneer. After that, one resin-impregnated veneer or a plurality of resin-impregnated veneers stacked with their fiber directions aligned is pressed and heated to obtain a consolidated resin-treated material, which is used as a surface layer material. A low-specific-gravity veneer obtained from low-specific-gravity wood is used as a core layer material, and these are compositely laminated and then pressed and heated. The method for producing an acoustic material according to the invention of claim 2 is a low-specific-gravity wood. The low specific gravity veneer thus obtained is subjected to a consolidation heat treatment in a sealed state to obtain a consolidation heat treatment veneer, and then one consolidation heat treatment veneer or a plurality of consolidation heat treatment veneers laminated with fiber directions aligned As a material, this compaction heat treated material is used as a surface layer material A low specific gravity veneer obtained from wood is used as a core layer material, these are compositely laminated, and then compression heating is performed. Thus, in the present invention, a consolidated resin treatment material using low specific gravity wood as a raw material And a low specific gravity wood in a composite layer, or a composite heat-treated material and a low specific gravity wood in which a low specific gravity wood is used as a raw material, for example, from an unused low specific gravity wood such as cedar wood to the highest grade. It is possible to obtain a good material having a high specific dynamic Young's modulus and a small internal friction comparable to that of German spruce. Therefore, the forest resources of Japan can be effectively used, and the specific gravity of the obtained material can be easily changed by changing the pressure heating condition, and by changing the type of thermosetting resin to be impregnated, Alternatively, since various acoustic characteristics can be provided by changing the conditions of the consolidation heat treatment in a closed state, it is possible to easily manufacture an acoustic material that can be used for the acoustic parts of various musical instruments.

Claims (3)

[Claims] 1. A resin-impregnated veneer is obtained by impregnating a low-specific-gravity veneer obtained from low-specific-gravity wood with a low-molecular-weight thermosetting resin.
After that, one resin-impregnated single plate or a plurality of resin-impregnated single plates stacked with their fiber directions aligned is pressed and heated to obtain a consolidated resin-treated material. A method for producing an acoustic material, characterized in that a low specific gravity veneer obtained from wood is used as a core layer material, and these are laminated in a composite manner and then compressed and heated. 2. A low specific gravity veneer obtained from low specific gravity wood is heat treated in a sealed state to obtain a consolidated heat treated veneer.
A single compaction heat-treated veneer or a plurality of compaction heat-treated veneers laminated in the fiber direction is used as a consolidation heat-treated material, and the consolidation heat-treated material is used as a surface layer material, and a low specific gravity veneer obtained from low specific gravity wood is used as a core layer A method for producing an acoustic material, which comprises compounding these as a material, and then compressing and heating. 3. The method for producing an acoustic material according to claim 1, wherein the low specific gravity wood is a cedar wood.