JP7640243B2 - Method for designing and manufacturing acoustic control panel - Google Patents

Description

The present invention relates to a method for designing and manufacturing an acoustic control panel that is installed on the ceiling, walls, etc. of a room in a facility such as a concert hall, a movie theater, a theater, a music lesson room, a broadcasting studio, or an audiovisual room in order to improve or enhance the acoustic environment in the room.

Conventionally, in facilities such as concert halls, movie theaters, theaters, music lesson rooms, broadcasting studios, audiovisual rooms, and particularly in facilities where the acoustic environment within the room is important, the sound absorption, reflection, and diffusion characteristics of the ceiling and wall surfaces have been appropriately adjusted taking into account the volume level and frequency characteristics of the sound source generated within the room, while also appropriately preventing acoustic disturbances such as reverberation, flutter echo, and booming, in order to improve or enhance the acoustic environment within the room.

For example, a method has been proposed for adjusting the acoustic environment of a room 1 to an appropriate level by appropriately selecting and arranging high-frequency sound-absorbing panels 4 that absorb high-frequency sound, mid-frequency sound-absorbing panels 5 that absorb mid-frequency sound, and sound diffusion panels 6 and 7 that reflect and diffuse sound at various angles vertically and horizontally on the walls 3 of the room 1 (see Patent Document 1).

A method has also been proposed in which a nonwoven fabric member 2 is filled into the space defined by opposing perforated board members 1, 1 to form an acoustic adjustment panel material that is adjusted to absorb or reflect sounds in a specific frequency band, and the acoustic adjustment panel material is then appropriately positioned on the wall surface W of the room to adjust the room to an appropriate acoustic environment (see Patent Document 2).

Japanese Patent Application Publication No. 06-158750 Utility Model Registration No. 3135263

In the method of Patent Document 1, the high-frequency sound-absorbing panel 4, mid-frequency sound-absorbing panel 5, and sound-diffusing panels 6 and 7 are constructed by stretching nonwoven fabric 4c and plate-like body 5b on the surface, and the sound absorption, reflection, and diffusion performance can be changed by appropriately selecting the internal structure and the materials of the nonwoven fabric 4c and plate-like body 5b, but to do so, many different types of panels must be produced, and it is difficult to subtly change these performances.

On the other hand, in the method of Patent Document 2, the sound absorption, reflection, and diffusion performance of the acoustic control panel material can be changed by appropriately selecting the material of the nonwoven fabric member 2 to be filled, the material of the perforated board material 1, and the diameter and pitch of the holes 11, etc. However, to do so, as with the method of Patent Document 1, many different types of acoustic control panel materials must be produced, and it is difficult to make subtle changes to these performances.

The present invention was made in consideration of these conventional problems, and aims to provide a method for designing and manufacturing an acoustic control panel that can appropriately and subtly change the sound absorption, reflection, and diffusion performance without having to produce a large number of different types of acoustic control panels.

In order to achieve the above object, the design method of the acoustic control panel of the present invention is a design method of an acoustic control panel constructed by drilling holes in a flat plate material, characterized in that a perforated area having a band-like arrangement of holes in a predetermined pattern is formed in the flat plate material, and a band-like non-perforated area is formed.

Furthermore, the method is characterized in that multiple types of perforated areas are formed in the perforated area, each of which is made up of holes with different diameters.

Furthermore, in each of the perforated regions, the number of perforated arrangements is appropriately set to one or more, and non-perforated regions of a predetermined width are formed at the upper and lower ends of the flat plate material and between each of the perforated regions.

When considering the manufacturing efficiency of the drilling device, it is preferable to form the corresponding holes in each perforated region at the same longitudinal pitch.

The manufacturing method of the acoustic control panel of the present invention is characterized in that, in the manufacturing method of the acoustic control panel constructed by drilling holes in a flat plate material, drills at appropriate positions attached at equal intervals in the perpendicular direction to the drilling device are removed, and the diameter of the drills at appropriate positions is changed to different ones, and while transporting the flat plate material in the horizontal and longitudinal directions, the drills are intermittently moved up and down to form perforated and non-perforated areas in an appropriate pattern in the flat plate material.

It is also preferable to manufacture an acoustic control panel of a predetermined length by making the length of the flat plate material an integer multiple of a predetermined length unit and cutting it in an orthogonal direction at an appropriate position corresponding to the integer multiple of that length unit.

The acoustic control panel design method of the present invention allows the sound absorption performance of the acoustic control panel to be varied in various ways depending on the material of the flat plate, the diameter and pitch of the holes, and the pattern of the perforated and non-perforated areas.

And it is possible to produce an acoustic control panel in which the perforated and non-perforated areas have different performance characteristics and the sound absorption coefficient for sound frequencies is high over a wide frequency range.

In addition, according to the manufacturing method of the acoustic control panel of the present invention, the acoustic control panel can be manufactured in the same manner as conventional methods without requiring any special manufacturing process, and manufacturing costs are not high. Furthermore, material waste can be eliminated.

1A is a front view of one embodiment of an acoustic control panel of the present invention, and FIG. 1B is a front view of another embodiment. 1 is an explanatory diagram showing the cross-sectional structure of a flat plate material made of plywood of an acoustic control panel. FIG. 2 is a cross-sectional view showing the state in which the acoustic control panel shown in FIG. 1 is installed on a wall surface. 1 is a conceptual diagram illustrating a sound absorbing mechanism in an acoustic control panel. FIG. 1 is a conceptual diagram illustrating a sound absorbing mechanism in a Helmholtz resonator. 1 is a graph showing the relationship between sound absorption coefficient and sound frequency in an acoustic control panel. 1 is a graph showing the relationship between the center frequency of sound and the average sound absorption coefficient in a lesson room. 1 is a graph showing the relationship between sound absorption coefficient and sound frequency in a conventional acoustic control panel. FIG. 1 is a front view of a wall constructed using conventional acoustic control panels. 4 is a graph showing the relationship between sound absorption coefficient and sound frequency in the acoustic control panel of the present invention. FIG. 2 is a front view of a wall constructed using the acoustic control panel of the present invention. 1 is a front view of an embodiment of an acoustic control panel manufactured by the design method of the present invention. 13 is a table showing specifications of the acoustic control panel shown in FIG. 12 . 13 is a table showing calculated frequency characteristics of the sound absorption coefficient of the acoustic control panel shown in FIG. 12 . 13 is a table showing measurement results of frequency characteristics of sound absorption coefficient in the acoustic control panel shown in FIG. 12. 13 is a graph showing predicted and measured values of the frequency characteristics of the sound absorption coefficient of the acoustic control panel shown in FIG. 12 . 1 is a front view of an embodiment of an acoustic control panel manufactured by the manufacturing method of the present invention. 1 is an explanatory diagram showing a method for drilling holes in a conventional acoustic control panel using a drilling device. 4 is an explanatory diagram showing a method of drilling holes in the acoustic control panel of the present invention using a drilling device. FIG. 1A is a front view of one embodiment of a conventional acoustic control panel, and FIG. 1B is a front view of another embodiment.

The design and manufacturing methods for the acoustic control panel of the present invention will be described in detail below with reference to the drawings.

First, the acoustic control panel 1 designed by the design method of the present invention is, as shown in FIG. 1, a rectangular flat plate material 2 of appropriate dimensions, on which perforated areas 3 having a strip-like arrangement of holes are formed in a predetermined pattern, and also a strip-like non-perforated area 4 is formed.

The flat board material 2 may be a veneer made of natural wood such as larch, western cedar, linden, tamomasa, naramasa, or cherry, or a plywood made by laminating these as shown in FIG. 2.
Furthermore, a single plate made of synthetic resin or metal, or a plywood made by laminating these may also be used.

In this embodiment, the dimensions of the flat plate material 2 are 9 mm in thickness, 600 mm in height, and 900 mm, 1200 mm, 1500 mm, 1800 mm, 2100 mm, and 2400 mm in length.
However, this is not necessarily limited to this, and flat plate materials 2 of various dimensions can be used as necessary.

In this embodiment, the holes 5 formed in the longitudinally extending perforated array forming the perforated region 3 had apertures of 6 mm, 8 mm, and 9 mm and a longitudinal pitch of 20 mm.
However, this is not necessarily limited to this, and holes 5 of various diameters and pitches can be formed as necessary.

Furthermore, to improve fire resistance, the surface of the flat plate material 2 may be coated with a non-flammable paint, a flame-retardant paint, etc.

A conventional acoustic control panel 101 is, for example, an acoustic control panel 101A formed by uniformly forming large-diameter holes 105A with an aperture of 9 mm at a pitch of 25 mm over substantially the entire surface area of a rectangular flat plate material 102 as shown in FIG. 20(A), or an acoustic control panel 101B formed by uniformly forming small-diameter holes 105B with an aperture of 6 mm at a pitch of 25 mm as shown in FIG. 20(B).
That is, the conventional acoustic control panel 101 has holes 105 uniformly formed at a predetermined diameter and at a predetermined pitch over substantially the entire surface area of the flat plate material 102 .

On the other hand, as shown in FIG. 1, the acoustic control panel 1 of the present invention is formed by dividing and forming a band-shaped perforated area 3A, 3B, 3C formed from a plurality of perforated arrangements on the surface of a rectangular flat plate material 2, in which large, medium and small holes 5A, 5B, 5C with a diameter of 9 mm, a diameter of 8 mm and a diameter of 6 mm are drilled at a longitudinal pitch of 20 mm, and a band-shaped non-perforated area 4 is formed without forming any holes.

In other words, the acoustic control panel 1 of the present invention is an acoustic control panel constructed by drilling holes in a flat plate material, characterized in that the flat plate material 2 has a perforated area 3 with a band-like arrangement of holes in a predetermined pattern, and a band-like non-perforated area 4 formed therein.

The perforated region 3 is composed of multiple types of perforated arrangements with different diameters of the holes 5, and is particularly characterized in that the holes 5 in each of the multiple types of perforated arrangements are formed at the same pitch in the longitudinal direction.

Specifically, the acoustic control panel 1A of one embodiment of the present invention uses a flat board 2 made of laminated plywood made of Japanese linden wood 2A and Japanese cedar wood 2B and 2C, as shown in Figure 2, with a thickness of 9 mm, a height of 600 mm, and a length of 1500 mm.

As shown in FIG. 1(A), the surface of the rectangular flat plate material 2 is formed with a predetermined pattern of perforated areas 3A1, 3A2 in which large-diameter 9 mm holes 5A are formed in a band shape with a longitudinal pitch of 20 mm, perforated areas 3B1, 3B2 in which medium-diameter 8 mm holes 5B are formed in a band shape with a longitudinal pitch of 20 mm, perforated areas 3C1, 3C2 in which small-diameter 6 mm holes 5C are formed in a band shape with a longitudinal pitch of 20 mm, and non-perforated areas 4A, 4B, 4C, 4D, 4E formed in a band shape.

As shown in Figure 2, the acoustic control panel 1B of another embodiment of the present invention is also made of plywood made of laminated linden wood 2A and cedar wood 2B, 2C, just like the acoustic control panel 1A, and uses a flat plate material 2 that is 9 mm thick, 600 mm high, and 1500 mm long.

As shown in FIG. 1(B), the surface of the rectangular flat plate material 2 is formed with a predetermined pattern of perforated areas 3A1, 3A2 in which large-diameter 9 mm holes 5A are formed in a band shape with a longitudinal pitch of 20 mm, perforated areas 3B1, 3B2, 3B3 in which medium-diameter 8 mm holes 5B are formed in a band shape with a longitudinal pitch of 20 mm, perforated areas 3C1, 3C2 in which small-diameter 6 mm holes 5C are formed in a band shape with a longitudinal pitch of 20 mm, and non-perforated areas 4A, 4B, 4C, 4D, 4E formed in a band shape.

Next, the design method for the acoustic control panel of the present invention will be described in detail below with reference to the drawings.

An acoustic control panel 101, in which holes 105 of a specified diameter are formed at a specified pitch on the surface of a flat plate material 102, can be understood as a resonator-type sound-absorbing material, and can be likened to an array of Helmholtz resonators (pots) 106, with an opening diameter d, a narrow neck length l, a cavity depth L, and a volume V, as shown in Figure 4.

As shown in Figure 5, when sound energy is applied to the opening of this Helmholtz resonator (pot) 106, the air in the narrow neck moves vertically as a single mass, causing the air in the hollow part to vibrate vertically like a spring, and the sound absorption effect is achieved through friction loss.

The resonant frequency fo of this Helmholtz resonator (pot) 106 can be expressed as the following formula 1 using the diameter d of the opening, the length l of the narrow neck, the depth L of the cavity, and the volume V.

ここで、ｃは音速、δは管端補正値である。

Here, c is the sound speed and δ is the tube end correction value.

In this Helmholtz resonator (pot) 106, the sound absorption coefficient corresponding to the sound frequency exhibits a curve that shows a maximum value at the resonance frequency fo, as shown in Figure 6.

In a space used for musical performance, such as a music lesson room, the material of the acoustic control panel must be selected and the range of use must be determined so that the average sound absorption coefficient of the wall and ceiling surfaces has as flat a frequency characteristic as possible, as shown in Figure 7.

In the conventional acoustic control panel 101, as shown in FIG. 8, holes 105 are uniformly formed with a predetermined diameter and a predetermined pitch over almost the entire surface area of the rectangular flat plate material 102, so that each of the acoustic control panels 101C, 101D, and 101E absorbs only sounds in a specific narrow frequency range.

Therefore, in order to adjust the frequency characteristics, as shown in FIG. 9, multiple types of acoustic control panels 101C, 101D, and 101E, each having holes 105C, 105D, and 105E with different diameters and pitches, must be used and combined in appropriate positions to form a wall surface, ceiling surface, etc.

On the other hand, in the acoustic control panel 1 of the present invention, as shown in FIG. 10, a plurality of perforated areas 3A, 3B, 3C are formed on the surface of a rectangular flat plate material 2, with large, medium, and small diameter holes 5A, 5B, 5C formed in a strip shape at a predetermined pitch, so that a single type of acoustic control panel 1 can absorb sounds in a wide frequency range.

Furthermore, in order to better adjust the frequency characteristics, as shown in FIG. 11, two types of acoustic control panels 1C and 1D can be used, combined in appropriate positions, and arranged upside down to form wall surfaces, ceiling surfaces, etc., thereby forming an indoor space with extremely good frequency characteristics.

In other words, the design method for the acoustic control panel of the present invention involves forming a perforated area 3 with a band-like arrangement of holes in a predetermined pattern on a rectangular flat plate material 2 of appropriate dimensions, as shown in Figure 1, and forming a band-like non-perforated area 4.

In the longitudinally extending perforated array that forms the perforated region 3, the perforations 5 are formed as perforations 5A, 5B, 5C having a plurality of different diameters.
Therefore, in one type of acoustic control panel 1, a plurality of types of perforated regions 3A, 3B, 3C consisting of holes 5A, 5B, 5C having different diameters are formed.

Furthermore, in each of the perforated regions 3A, 3B, 3C, the number of perforated arrangements is appropriately set to one or more, and non-perforated regions 4A, 4B, ... of a predetermined width are formed at the upper and lower ends of the rectangular flat plate material 2 and between each of the perforated regions 3A, 3B, 3C.

Furthermore, from the viewpoints of frequency characteristics, manufacturing, and design, it is preferable to design each of the perforated regions 3A, 3B, and 3C so that the longitudinal pitch of the corresponding holes 5A, 5B, and 5C is the same.

As shown in FIG. 3, the acoustic control panel 1 of the present invention is installed on a wall surface 11 of a music lesson room or the like via a support member 12, and a space 13 is defined between the wall surface 11 and the acoustic control panel 1, and a sound-absorbing member 14 is placed on the back surface of the acoustic control panel 1 for use.

As a result, sound in a specific frequency band is reflected and diffused on the surface of the acoustic control panel 1, and sound in a specific frequency band passes through the hole 5 and is absorbed by the space 13 and the sound-absorbing material 14.

As shown in Figures 1(A) and (B), the acoustic control panel 1 of the present invention is formed on the surface of a rectangular flat plate material 2 in a predetermined pattern with multiple perforated areas 3A, 3B, 3C, in which large, medium, and small diameter holes 5A, 5B, 5C are formed in strips at a predetermined pitch along the length, and multiple non-perforated areas 4 also formed in strips. Therefore, the sound absorption and reflection performance can be varied in various ways depending on the material of the flat plate material 2, the diameter and pitch of the holes 5, and the pattern of the perforated areas 3 and non-perforated areas 4.

In one acoustic control panel 1, the perforated areas 3A, 3B, 3C and the non-perforated areas 4A, 4B, ... each have different performance, and as shown in Figure 10, the sound absorption coefficient for sound frequency also shows balanced characteristics over a wide frequency range.

In addition, the relationship of the sound absorption coefficient to the sound frequency is completely different depending on the acoustic control panels 1A and 1B, which have different patterns. Therefore, by taking these characteristics into consideration and appropriately arranging multiple acoustic control panels 1, as shown in Figure 7, it is possible to optimize the acoustic environment in a room such as a music lesson room to an unprecedented degree.

By adopting the design method for the acoustic control panel of the present invention, an acoustic control panel 11 was actually designed and manufactured with the configuration shown in FIG. 12 and the specifications shown in FIG. 13.

When the sound absorption coefficient of each of the perforated regions 3A, 3B, 3C, and 3D and the non-perforated region 4 of this acoustic control panel 11 was calculated, the predicted sound absorption coefficient of the acoustic control panel 11 was as shown in FIG. 14.

Here, it was assumed that a single flat plate had multiple bands of conventional perforated and non-perforated plates arranged in its longitudinal direction, and the sound absorption coefficient was calculated.
In addition, for the perforated regions 3A, 3B, and 3C, the sound absorption coefficient was calculated assuming that the volume of the back air space is doubled since they are adjacent to the band of non-perforated plate.

When the opening ratio of the entire plate becomes small, it is believed that in addition to the performance of a perforated plate, the sound absorption performance due to the plate vibration of a non-perforated plate will also be exhibited, and this effect will also be taken into account when calculating the sound absorption rate.

The predicted sound absorption coefficient of the acoustic control panel 11 can be calculated based on the sound absorption coefficients of each perforated and non-perforated area using the following formula 2.

The sound absorption coefficient of this acoustic control panel 11 was measured in a laboratory in accordance with ISO 354, and the results are shown in Figure 15.

When the predicted sound absorption coefficient of the acoustic control panel 11 shown in Figure 14 and the measured sound absorption coefficient shown in Figure 15 were plotted on a graph, the result was as shown in Figure 16, which showed that the predicted and measured values were highly consistent.

Next, the manufacturing method of the acoustic control panel of the present invention will be described in detail below with reference to the drawings.

When manufacturing a conventional acoustic control panel 101, for example, as shown in FIG. 18, while conveying a flat plate material 102 in the horizontal and longitudinal directions, drills 22, 22, ... attached at equal intervals in the perpendicular direction to a drilling device 21 are intermittently moved up and down to form holes uniformly over almost the entire surface area of the flat plate material 102.

On the other hand, when manufacturing the acoustic control panel 1 of the present invention, as shown in FIG. 19, the drills 22, 22, ... attached at equal intervals in the perpendicular direction to the drilling device 21 are removed from the appropriate positions of the drills 22, and the diameter of the drills 22 at the appropriate positions is changed to a different one.

In this way, an acoustic control panel 1 can be manufactured in the same manner as in the conventional method, by intermittently moving the drills 22, 22, ... up and down to form perforated areas 3 and non-perforated areas 4 in an appropriate pattern on the flat plate material 2 as shown in Figure 17.

In other words, the manufacturing method for the acoustic control panel of the present invention involves removing the drills 22 at appropriate positions from the drills 22, 22, ... attached at equal intervals in the perpendicular direction to the drilling device 21, changing the diameter of the drills 22 at appropriate positions to different ones, and intermittently moving the drills 22, 22, ... up and down while transporting the flat plate material 2 horizontally and longitudinally, to form perforated areas 3 and non-perforated areas 4 in an appropriate pattern in the flat plate material 2.
Furthermore, by appropriately changing the time for which the drills 22, 22, . . . are intermittently moved up and down, the longitudinal pitch of the holes in one flat plate material 2 can also be changed.

Furthermore, from the viewpoint of using materials without waste, it is preferable to manufacture an acoustic control panel 1 of a predetermined length by setting the length La of the flat plate material 2 to an integer multiple of a predetermined length unit L1 and cutting it in the orthogonal direction at an appropriate position corresponding to an integer multiple of that length unit L1.

As described above, according to the manufacturing method of the acoustic control panel of the present invention, the acoustic control panel 1 of the present invention can be manufactured in the same manner as in the conventional method using a conventional drilling device 21 without requiring any special manufacturing process, and the manufacturing costs are not high.

In addition, the length La of the flat plate material 2 is an integer multiple of a predetermined length unit L1, and it is cut in the orthogonal direction at an appropriate position that corresponds to an integer multiple of that length unit L1, so that an acoustic control panel 1 of a predetermined length can be manufactured using material without waste.

When optimizing the acoustic environment in a room such as a music lesson room, a conventional acoustic control panel 101 only provides simple sound absorption and reflection performance in a single acoustic control panel 101, so as shown in Figure 9, multiple types of acoustic control panels 101C, 101D, and 101E had to be used.

On the other hand, according to the acoustic control panel 1 of the present invention, the performance of each of the perforated and non-perforated areas 3 and 4 in a single acoustic control panel 1 is different, and complex sound absorption and reflection performance can be achieved. In addition, the sound absorption coefficient for sound frequency also exhibits good values over a wide frequency range, so that, as shown in FIG. 11, even if only a small number of types of acoustic control panels 1C and 1D are used, the acoustic environment can be optimized and subtle acoustic adjustments can also be made.

In addition, according to the acoustic control panel 1 of the present invention, as shown in FIG. 11, by using one acoustic control panel 1 upside down, and even when each acoustic control panel 1 is installed upside down, different sound absorption and reflection performances can be achieved. Taking this into consideration, it is possible to perform extremely multifaceted and delicate acoustic adjustments.

Furthermore, as can be easily understood by comparing Figures 9 and 11, when an acoustic control panel is installed on a wall, the conventional acoustic control panel 101 has an extremely large number of holes, which are formed over the entire surface, giving the appearance an extremely cluttered appearance.

On the other hand, in the acoustic control panel 1 of the present invention, the holes are formed in certain areas and not over the entire surface, giving the appearance an extremely simple impression and improving the design of the wall surface and room.

In addition, by using multiple acoustic control panels 1 of different lengths and connecting adjacent acoustic control panels 1 at a predetermined angle, the sound absorption and reflection states can be adjusted appropriately, further optimizing the acoustic environment.

Furthermore, when fine-tuning the acoustic adjustment is required, the acoustic adjustment panel 1A, 1B having the perforation pattern shown in FIG. 1(A) or (B) may be replaced with an acoustic adjustment panel 1C having a different perforation pattern.

As described above, by installing the acoustic control panel 1 of the present invention on the ceiling, walls, etc. of a room, it is possible to realize an interior structure that can optimize the acoustic environment of the room in an unprecedented way.

In the above embodiment, two types of acoustic control panels 1A and 1B have been described, each having a perforated area 3 and a non-perforated area 4 formed with a predetermined perforation pattern. However, it is of course possible to configure an acoustic control panel 1 having a perforated area 3 and a non-perforated area 4 formed with any other suitable perforation pattern.

Furthermore, the material and dimensions of the flat plate material 2 of the acoustic control panel 1, the diameter and pitch of the holes 5, etc. are not limited to those in the above embodiment, and a more suitable acoustic control panel 1 can be produced by appropriately selecting them.

Furthermore, in the above embodiment, the acoustic control panel 1 is installed on the wall surface of the music lesson room. However, the acoustic control panel 1 may be installed not only on the wall surface, but also on the ceiling surface, pillar surface, and the like.
Furthermore, as mentioned above, it goes without saying that the present invention can be applied not only to music lesson rooms, but also to facilities such as concert halls, movie theaters, theaters, music lesson rooms, broadcasting studios, audiovisual rooms, and other facilities where it is necessary to improve or enhance the indoor acoustic environment.

1 Acoustic adjustment panel 1A, 1B Acoustic adjustment panel 2 Flat plate material 3 Perforated area 3A, 3B, 3C Perforated area 4 Non-porous area 4A, 4B, 4C, 4D, 4E Non-porous area 5 Hole 5A, 5B, 5C Hole

Claims (2)

In a method for manufacturing an acoustic control panel constructed by drilling holes in a flat plate material,
A method for manufacturing an acoustic control panel, comprising the steps of: detaching drills at appropriate positions attached at equal intervals in a direction perpendicular to a drilling device; changing the diameter of the drills at appropriate positions to different ones; transporting the flat plate material horizontally and lengthwise while intermittently moving the drills up and down to form perforated and non-perforated areas in an appropriate pattern in the flat plate material. The method for manufacturing an acoustic control panel as described in claim 1, characterized in that the length of the flat plate material is an integer multiple of a predetermined length unit, and an acoustic control panel of a predetermined length is manufactured by cutting it in an orthogonal direction at an appropriate position corresponding to the integer multiple of that length unit.

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