Acoustic diffusion panel

Abstract

To provide an acoustic diffusion panel that can achieve an acoustic diffusion effect without having to form unevenness over the entire surface.SOLUTION: An acoustic diffusion panel (panel 10) comprises: a reflective panel 12 reflecting sound; a deceleration layer 14 arranged in a direction of sound incidence in the reflective panel 12 and divided into multiple regions; and an obstacle 30 held in different densities for each region.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an acoustic diffusion panel. [Background technology]

[0002] The following Patent Document 1 discloses a two-dimensional primitive root diffuser for scattering sound. Each well forming the two-dimensional primitive root diffuser is formed by a rectangular block, and its depth is determined by calculating the primitive root sequence theory. This results in a two-dimensional primitive root diffuser in which the depth of each well is different from the depth of the other wells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-87281 Summary of the Invention [Problem to be solved by the invention]

[0004] The two-dimensional primitive root-shaped diffuser of the above-mentioned Patent Document 1 is formed by arranging rectangular blocks in a lattice pattern. In an acoustic diffusion panel using such a two-dimensional primitive root-shaped diffuser, irregular irregularities are formed on the surface over the entire surface of the panel.

[0005] However, for design reasons or the like, it may be desirable to avoid forming projections and recesses over the entire surface of the acoustic diffusion panel.

[0006] In consideration of the above, the present disclosure provides an acoustic diffusion panel that can obtain an acoustic diffusion effect without forming irregularities over the entire surface. [Means for solving the problem]

[0007] The first embodiment of the acoustic diffusion panel comprises a reflective panel that reflects sound, a deceleration layer that is arranged in the direction of incidence of the sound on the reflective panel and is divided into a plurality of regions, and obstacles that are maintained at different densities in each of the regions.

[0008] In the acoustic diffusion panel of the first embodiment, a deceleration layer is disposed in the direction of sound incidence on the reflective panel. An obstacle is held in the deceleration layer. Therefore, the sound to be diffused that is incident on the deceleration layer is decelerated by the obstacle.

[0009] The obstacles are held at different densities in each of the multiple regions. Therefore, the speed of the target sound passing through the deceleration layer differs in each region. As a result, the phase of the reflected sound becomes random for the sound incident on the reflective panel.

[0010] This makes the waveform of the sound formed by the interference between the incident sound and the reflected sound, or the interference between the reflected sounds, random. In other words, the distribution of the positions where the sound is amplified by the incident sound and the reflected sound is not concentrated in a specific place in the space. This increases the diffusion of the sound.

[0011] In the acoustic diffusion panel of the second aspect, in the acoustic diffusion panel according to the first aspect, when sound is simultaneously incident on a plurality of the regions, a difference in time required between the region where sound enters the deceleration layer, is reflected by the reflective panel, and is emitted from the deceleration layer, is τ max is expressed by the following equation (I), where λ is the wavelength of the sound to be diffused and C0 is the sound speed of the sound to be diffused.

[0012] τ max =(λ / 2) / C0 (I)

[0013] If there are two sound waves with a wavelength of λ, the maximum phase difference between these two sound waves is (λ / 2). In other words, the maximum phase difference between sound waves with a wavelength of λ is (λ / 2).

[0014] In the acoustic diffusion panel of the second embodiment, the difference in time required between the fastest region and the slowest region from when the light enters the deceleration layer to when it is reflected by the reflection panel and when it is emitted from the deceleration layer is τ max is expressed as (λ / 2) / C0. In other words, the reflected sounds in these regions have the maximum phase difference with each other.

[0015] As a result, the range of variation in the phases of the reflected sounds in the multiple regions is larger than when these reflected sounds do not have the maximum phase difference, which can improve the diffusivity of the sound.

[0016] The acoustic diffusion panel of a third aspect is the acoustic diffusion panel of the second aspect, wherein the plurality of regions are each a region obtained by dividing the width direction of the deceleration layer into (P-1) regions, with P being an arbitrary prime number, and when each remainder when dividing (P-1) powers generated by exponentiating (P-1) consecutive integers with a primitive root of the prime number P as a base by P is m, the region in which the time from when light enters the deceleration layer to when it is reflected by the reflection panel and emitted from the deceleration layer is the fastest and the required time difference τ in each of the (P-1) regions are m is expressed by the following formula (II).

[0017] τ m = τ max ×(m-1) / (P-1) (II)

[0018] In the acoustic diffusion panel of the third embodiment, the time difference between the area where the sound enters the deceleration layer, reflects off the reflection panel, and is emitted from the deceleration layer the fastest and the other areas is τ max ×(m-1) / (P-1), that is, as a linear function of m.

[0019] Since m is a power of (P-1) consecutive integers generated by exponenting the primitive root of the prime number P, it will not be the same value. Therefore, the phase of each reflected sound in each area will not be the same. This can increase the diffusion of sound.

[0020] In a fourth aspect of the acoustic diffusion panel, in the acoustic diffusion panel according to the third aspect, when the obstacles are spheres, the number N of the obstacles per unit volume of each of the (P-1) regions is m is expressed by the following formula (III), where a is the radius of the sphere and L is the thickness of the deceleration layer.

[0021] N m ={3 / (2πa 3 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (III)

[0022] The sound speed in each region is C m , the region where the time from entering the deceleration layer to being reflected by the reflective panel and exiting the deceleration layer is the fastest (m = 1, τ m If the speed of sound in the region where =0 is C0, the time difference τ m is expressed by the following equation (i).

[0023] τ m =2L×[(1 / C m )-(1 / C0)]···(i)

[0024] Also, if there are spherical obstacles with radius a in the area, the number of obstacles per unit volume is N m Speed ​​of sound C when there are m Regarding the speed of sound C0 when there are no obstacles, the following equation (ii) holds:

[0025] (C0 / C m ) 2 =1+(2 / 3)πa 3 N (ii)

[0026] Formula (III) is derived from the above formulas (I), (II), (i) and (ii).

[0027] In this way, in the acoustic diffusion panel of the fourth embodiment, the number of obstacles per unit volume in each of the (P-1) regions is determined according to the radius a of the sphere and the thickness L of the deceleration layer. mIn other words, regardless of the radius a of the sphere and the thickness L of the deceleration layer, the phase of each reflected sound in each region can be changed to increase the diffusivity of the sound.

[0028] In a fifth aspect of the acoustic diffusion panel, in the acoustic diffusion panel according to the third aspect, when the obstacles are disks whose in-plane direction is perpendicular to the incident direction of the sound to be diffused, the number N of the obstacles per unit volume in each of the (P-1) regions is m is expressed by the following equation (IV), where r is the radius of the disk and L is the thickness of the deceleration layer.

[0029] N m ={3 / (8πr 3 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (IV)

[0030] In the region, there are N disk obstacles of radius r per unit volume. m Speed ​​of sound C when there are m Regarding the speed of sound C0 when there are no obstacles, the following equation (iii) holds:

[0031] (C0 / C m ) 2 =1+(8 / 3)πr 3 N (iii)

[0032] Formula (IV) is derived from the above formulas (I), (II), (i) and (iii).

[0033] In this way, in the acoustic diffusion panel of the fifth embodiment, the number of obstacles per unit volume in each of the (P-1) regions is determined according to the radius r of the disk and the thickness L of the deceleration layer. m In other words, regardless of the radius r of the disk and the thickness L of the deceleration layer, the phase of the reflected sound in each region can be changed to increase the diffusivity of the sound.

[0034] In a sixth aspect of the acoustic diffusion panel, in the acoustic diffusion panel according to the third aspect, when the obstacles are plates whose in-plane direction is perpendicular to the incident direction of the sound to be diffused, the number N of the obstacles per unit area as viewed from the end face of the obstacle in each of the (P-1) regions is m is expressed by the following equation (V), where d is the width of the plate and L is the thickness of the deceleration layer.

[0035] N m ={4 / (πd 2 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (V)

[0036] If there is a plate obstacle of width d in the area, the volume per unit of volume is N m Speed ​​of sound C when there are m Regarding the speed of sound C0 when there are no obstacles, the following equation (iv) holds:

[0037] (C0 / C m ) 2 =1+π(d / 2) 2 N (iv)

[0038] Formula (V) is derived from the above formulas (I), (II), (i) and (iv).

[0039] In this way, in the acoustic diffusion panel of the sixth embodiment, the number of obstacles per unit volume in each of the (P-1) regions is determined according to the width d of the plate and the thickness L of the deceleration layer. m In other words, regardless of the width d of the plate and the thickness L of the deceleration layer, the phase of the reflected sound in each region can be changed to increase the diffusivity of the sound.

[0040] An acoustic diffusion panel of a seventh aspect is the acoustic diffusion panel according to any one of the third to sixth aspects, wherein the consecutive integers are (P-1) integers starting from 10.

[0041] According to the acoustic diffusion panel of the seventh aspect, the power is generated by exponenting (P-1) consecutive integers starting from 10. Therefore, the remainder is less likely to be the value of the power itself, compared to when the power is generated by exponenting (P-1) consecutive integers starting from 1. Therefore, it is possible to prevent a sequence of areas with similar phase differences of reflected sounds from being formed.

[0042] An acoustic diffusion panel of an eighth aspect is the acoustic diffusion panel according to any one of the third to sixth aspects, wherein when there are a plurality of primitive roots, the largest primitive root is taken as the base.

[0043] In the acoustic diffusion panel of the eighth aspect, the exponent is generated with a large primitive root as the base. Therefore, compared to the case where the exponent is generated with a small primitive root as the base, the modular exponent is less likely to be the value of the exponent itself. Therefore, it is possible to prevent the formation of a sequence of areas with similar phase differences of reflected sounds.

[0044] The ninth aspect of the acoustic diffusion panel is an acoustic diffusion panel described in any one of the third to sixth aspects, wherein the multiple regions are (P-1) regions equally divided in the width direction of the deceleration layer, where P is the prime number closest to the value expressed by W / (λ / 4), where W is the width of the reflective panel and λ is the wavelength of the sound to be diffused.

[0045] In the acoustic diffusion panel of the ninth aspect, when the wavelength of the sound to be diffused is λ, the speed reducing layer is divided into regions of a size close to the dimension (λ / 4) in the width direction, which makes it easier to diffuse the sound and sounds with shorter wavelengths (higher sounds). Effect of the Invention

[0046] According to the acoustic diffusion panel of the present disclosure, an acoustic diffusion effect can be obtained without forming irregularities over the entire surface. [Brief description of the drawings]

[0047] [Figure 1]FIG. 1A is a perspective view showing an overview of an acoustic diffusion panel according to an embodiment of the present disclosure, and FIG. 1B is a perspective view showing a portion of the acoustic diffusion panel. [Diagram 2] 1A and 1B are front views showing a net and a sphere arranged on a reflective layer in an acoustic diffusion panel according to an embodiment of the present disclosure, (B) is an arrow view taken along line BB in (A), and (C) is an arrow view taken along line CC in (A). [Diagram 3] FIG. 1A is a partially enlarged view showing an example of a method for holding a sphere, and FIG. 1B is a partially enlarged view showing another example of a method for holding a sphere. [Figure 4] 1 is a side view showing an overview of an acoustic diffusion panel according to an embodiment of the present disclosure. [Diagram 5] 1 is a graph showing an example of a phase difference of a sound wave applied to an acoustic diffusion panel according to an embodiment of the present disclosure. [Figure 6] 13 is a table showing an example of a method for calculating a modular exponentiation for setting a phase difference of sound to be applied to a deceleration layer in an acoustic diffusion panel according to an embodiment of the present disclosure. [Figure 7] A conceptual diagram showing the phase difference of sound applied to a deceleration layer in an acoustic diffusion panel according to an embodiment of the present disclosure. [Figure 8] 13A is a perspective view showing a sphere as an obstacle, FIG. 13B is a perspective view showing a disk as an obstacle, and FIG. 13C is a perspective view showing a plate as an obstacle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Hereinafter, an acoustic diffusion panel according to an embodiment of the present disclosure will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same components. However, unless otherwise specified in the specification, each component is not limited to one, and may be present in multiple numbers.

[0049] In addition, explanations of configurations and symbols that are duplicated in each drawing may be omitted. Note that the present disclosure is not limited to the following embodiments, and may be implemented by making appropriate modifications, such as omitting configurations, replacing them with different configurations, or combining one embodiment and various modified examples, within the scope of the purpose of the present disclosure.

[0050] In each drawing, the directions indicated by the arrows X and Y are directions along a horizontal plane and are perpendicular to each other. The direction indicated by the arrow Z is a direction along the vertical direction (up and down direction). The directions indicated by the arrows X, Y, and Z in each drawing are assumed to be mutually consistent.

[0051] <Audio diffusion panel> (Configuration Overview) 1(A) illustrates a panel 10 according to an embodiment of the present disclosure. The panel 10 is an acoustic diffusion panel including a reflective panel 12 and a deceleration layer 14. The panel 10 can be installed on the wall of a building, or on a ceiling or the like.

[0052] The reflective panel 12 can be formed using various materials such as wood, resin, metal, etc. The deceleration layer 14 is disposed in the incident direction of the sound wave T on the reflective panel 12, and is a portion that covers the reflective panel 12.

[0053] In the following description, the "direction of sound incidence on the reflective panel 12" may be referred to as "the front of the reflective panel." The "front" does not necessarily mean the horizontal direction, but refers to the downward direction when the panel 10 is used on a ceiling.

[0054] The deceleration layer 14 is divided into a plurality of regions. The method of division will be described later, but for example, in this embodiment, the layer is divided into six regions R1 to R6 along the width direction (X direction) of the reflective panel 12. Note that, although partition plates or the like that spatially separate each region may be provided at the boundaries between the regions R1 to R6, no partition plates are provided in this embodiment.

[0055] In the following description, the regions R1 to R6 may be collectively referred to as region R unless there is a particular need to distinguish between them.

[0056] (Configuration of the domain in the deceleration layer) Although not shown in Fig. 1(A), a net 20 serving as a retaining member can be disposed in each region R of the deceleration layer 14, as shown in Fig. 1(B). The net 20 is, for example, a fabric formed by arranging polyvinylidene chloride fibers in a mesh pattern, which allows sound waves to easily pass through and is used in speakers, etc.

[0057] 2(A)-(B), spheres 30 serving as obstacles are fixed to the net 20. The spheres 30 can be made of various materials such as wood, resin, and metal, but it is preferable to select a material that is light in weight and unlikely to deteriorate over time.

[0058] One example of a method for fixing the sphere 30 to the net 20 is to attach a halved sphere 30 to both sides of the net 20 with an adhesive. Another example of a method for fixing the sphere 30 to the net 20 is to form a hole in the net 20, fit the sphere 30 in it, and attach the outer edge of the hole to the sphere 30 with an adhesive.

[0059] 3(A), the net 20 can be stacked in front of the reflective panel 12 using a support rod 22 and a fixing member 24. The support rod 22 is a fully threaded bolt disposed penetrating the net 20, and the fixing member 24 is a nut into which the support rod 22 is screwed.

[0060] By clamping the net 20 with the fixing members 24, the net 20 is positioned and held in front of the reflective panel 12. Similarly, the spheres 30 are positioned and held in front of the reflective panel 12.

[0061] As shown in Fig. 3(B), if the sphere 30 can be held in front of the reflective panel 12, the net 20 is not necessarily required. In the example shown in this figure, a support rod 22 passes through the inside of the sphere 30, and the sphere 30 is positioned and held on the support rod 22 by a fixing member 24.

[0062] 4, spheres 30 are held at different densities in each of the regions R1 to R6 in the deceleration layer 14. As will be described in detail later, by arranging the spheres 30 as obstacles in each of the regions R1 to R6, the speed of sound waves is reduced from when they enter the deceleration layer 14, when they are reflected by the reflective panel 12, and when they are emitted from the deceleration layer 14.

[0063] Furthermore, by arranging the spheres 30 at different densities in each of the regions R1 to R6, the speed of the sound waves that enter the deceleration layer 14, are reflected by the reflective panel 12, and are then emitted from the deceleration layer 14 varies.

[0064] <Relationship between density and speed of sound> The difference in sound speed depending on the presence or absence of an obstacle will be explained. In the example shown in Fig. 8(A), a sphere 30 is placed in region R as an obstacle. If the sound speed when a sound wave T passes through region R is C, the sound speed when the sphere 30 is not present is C0, the radius of the sphere 30 is a, and the number of spheres 30 per unit volume of region R is N, then the following formula (A) is established. (Reference: WE Kock, FK Harvey, J. Acoust. Soc. Am., 21(5), 471-481, 1949. / The same applies to formulas (B) and (C). In this specification, the sound speed in air is C0 = 340 m / s.

[0065] (C0 / C) 2 =1+(2 / 3)×πa 3 N (A)

[0066] As obstacles to be placed in the region R, other than spheres, for example, disks 32 shown in FIG. 8(B) and plates 34 shown in FIG. 8(C) can also be used.

[0067] 8(B), a disk 32 is placed in region R as an obstacle. If the sound speed when the sound wave T passes through region R is C, the sound speed when the disk 32 is not present is C0, the radius of the disk 32 is r, and the number of disks 32 per unit volume of region R is N, then the following formula (B) holds. Note that the disks 32 are placed so that their in-plane directions (X direction and Y direction) are perpendicular to the incident direction of the sound wave T (Z direction).

[0068] (C0 / C) 2 =1+(8 / 3)×πr 3 N (B)

[0069] 8(C), a plate 34 is disposed in region R as an obstacle. If the sound speed when sound wave T passes through region R is C, the sound speed when plate 34 is not present is C0, the width of plate 34 as viewed from a direction (X direction) perpendicular to the incident direction of the sound wave (Z direction) is d, and the number of plates 34 per unit area as viewed from region R in the X direction is N, then the following formula (C) is established. Note that plate 34 is disposed across the X direction in region R. Furthermore, width d of plate 34 is the width in the direction intersecting with sound wave T as viewed from the end face of plate 34 (Y direction).

[0070] (C0 / C) 2 =1+π×(d / 2) 2 N (C)

[0071] <Sphere Density> The spheres 30 held in each of the regions R1 to R6 all have the same radius, but the maximum dimension of the diameter of these spheres 30 is smaller than the wavelength of the sound to be diffused. The density of the spheres 30 in each of the regions R1 to R6 can be any density, but it is preferable to have the following configuration.

[0072] The density of the spheres 30 in each of the regions R1 to R6 is set so that the phase of the reflected sound from the panel 10 is randomized, and the waveform of the sound formed by the interference between the incident sound and the reflected sound and the interference between the reflected sounds is randomized. This prevents the distribution of the positions where the sound is amplified by the incident sound and the reflected sound from concentrating in a specific place in the space, and improves the diffusion of the sound.

[0073] In order to randomize the phase of the reflected sound from the panel 10, it is preferable that there be large variation in the phase of the reflected sound when the sound to be diffused that is incident on the regions R1 to R6 is reflected.

[0074] (maximum phase difference) Here, the waveforms of two sound waves T1 and T2 with the same wavelength are shown in Fig. 5. The sound waves T1 and T2 are sound waves with a wavelength λ, and their phases are shifted from each other by half the wavelength (λ / 2).

[0075] In this embodiment, T1 is the sound wave that takes the "fastest" time from entering the deceleration layer 14 to being reflected by the reflective panel 12 and being emitted from the deceleration layer 14. T2 is the sound wave that takes the "slowest" time from entering the deceleration layer 14 to being reflected by the reflective panel 12 and being emitted from the deceleration layer 14.

[0076] That is, when sound to be diffused with a wavelength λ is simultaneously incident on the regions R1 to R6 of the panel 10, a phase difference of half the wavelength (λ / 2) is generated in the emitted sounds (sound waves T1 and T2) between the fastest and slowest emitted regions. Also, a phase difference of "less" than half the wavelength (λ / 2) is generated (sound waves T1 and T3 to T6) between the fastest emitted region and the other regions.

[0077] In other words, when the sound speed of the sound to be diffused is C0, the time difference τ required from when the sound enters the deceleration layer 14 until it is emitted from the deceleration layer 14 between the fastest and slowest emission regions is max is set to the "time difference" shown in the following formula (1). Note that formula (1) corresponds to formula (I) in this disclosure.

[0078] τ max =(λ / 2) / C0 (1)

[0079] (Phase difference in each region) As described above, in this embodiment, the deceleration layer 14 is divided into six regions R1 to R6 along the width direction (X direction). These regions are (P-1) regions obtained by equally dividing the width direction of the deceleration layer 14, where P is an arbitrary prime number.

[0080] That is, the regions R1 to R6 in this embodiment are formed by equally dividing the width direction of the deceleration layer 14 into 6 regions (7-1=6) by selecting 7 as the prime number P. The reason for selecting 7 as the prime number P will be described later.

[0081] Here, as shown in Figure 6, we define the primitive root of a prime number P as the "base r p Let (P-1) consecutive integers be the "exponent" n, and let m be the remainder when each of the (P-1) powers generated by dividing each of them by P.

[0082] If 7 is selected as the prime number P, the primitive roots of 7 are 3 and 5, and there are multiple primitive roots of 7. However, it is preferable to select the largest primitive root, i.e., 5, and use it as the "base" of the power r p Let us assume that.

[0083] In addition, the (P-1) consecutive integers are set as the "power exponent" n of the power factor. It is preferable to select integers equal to or greater than 10 as the consecutive integers. As an example, 10, 11, 12, 13, 14, and 15 are set as the "power exponent" n of the power factor.

[0084] This gives us (P-1) or 6 powers r p n As, 5 10 , 5 11 , 5 12 , 5 13 , 5 14 , 5 15 These powers r p nIf each “remainder” when dividing by P=6 is m, then the “remainders” m are 2, 3, 1, 5, 4, and 6, in the order of the “exponent” n.

[0085] In this embodiment, the region where the time from when the light enters the deceleration layer 14 to when it is reflected by the reflective panel 12 and when it is emitted from the deceleration layer 14 is the fastest and the required time difference τ m Let be the following equation (2-1).

[0086] τ m = τ max ×(m-1) / (P-1) (2-1)

[0087] The above formula (2-1) can be transformed into the following formula (2) using formula (1): Formulas (2-1) and (2) correspond to formula (II) of the present disclosure.

[0088] τ m =(λ / 2)×(m-1) / {C0(P-1)}···(2)

[0089] Here, as shown in FIG. 7, the remainder m=2, 3, 1, 5, 4, 6 is applied to the regions R1, R2, R3, R4, R5, and R6 arranged in order, and the required time difference τ m That is, the time difference in region R1 is τ2, the time difference in region R2 is τ3, the time difference in region R3 is τ1, the time difference in region R4 is τ5, the time difference in region R5 is τ4, and the time difference in region R6 is τ6.

[0090] In addition, in region R3, m=1, and according to formula (2), τ3=0. That is, the sphere 30 is not provided in region R3, and the sound passing through region R3 does not slow down. According to this method, the phases of the reflected sounds in each of regions R1 to R6 do not match, and there is no regularity in the arrangement of the remainder m between adjacent regions, so the phases of the reflected sounds reflected by the panel 10 become random.

[0091] (Setting the placement of obstacles in each area) The thickness of the deceleration layer 14 is L (the thickness along the incident direction of the sound to be diffused), and the speed of the sound to be diffused in each of the regions R1 to R6 is C m Assuming that m=1 to 6, the region where the time it takes for light to enter the deceleration layer 14, be reflected by the reflective panel 12, and be emitted from the deceleration layer 14 is the shortest, and the required time difference τ m (m=1 to 6) can also be expressed by the following equation (3).

[0092] τ m =2L×{(1 / C m )-(1 / C0)}···(3)

[0093] From the above equations (2) and (3), the following equation (4) is derived.

[0094] (C o / C m )={(m-1)λ / (4(P-1)L)}+1···(4)

[0095] Furthermore, the following formula (5) is derived from the above formulas (A) and (4). That is, when the obstacles arranged in the region R are spheres 30, the number N of spheres 30 per unit volume of each of the (P-1) regions R is m is expressed by the following formula (5), where a is the radius of the sphere and L is the thickness of the deceleration layer 14. Note that formula (5) corresponds to formula (III) in the present disclosure.

[0096] N m ={3 / (2πa 3 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (5)

[0097] According to the above formula (5), when a prime number P is selected and the deceleration layer 14 having a thickness L is divided into (P-1) regions, the number N of spheres 30 per unit volume in each region is m (In other words, density) is calculated using the remainder m. By setting the arrangement of the spheres 30 to be arranged in each region R based on this number, it is possible to increase the diffusivity of the target sound to be diffused having a wavelength λ.

[0098] In addition, when the disks 32 shown in FIG. 8(B) are used as obstacles, the number N of disks 32 per unit volume can be calculated using the following formula (6) derived from the above formulas (B) and (4). m It should be noted that formula (6) corresponds to formula (IV) in the present disclosure.

[0099] N m ={3 / (8πr 3 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (6)

[0100] In addition, when the plate 34 shown in FIG. 8C is used as the obstacle, the number N of the plates 34 per unit area as viewed from the X direction is calculated using the following formula (7) derived from the above formulas (C) and (4). m It should be noted that formula (7) corresponds to formula (V) in this disclosure.

[0101] N m ={4 / (πd 2 )}×[[{(m-1)λ / (4(P-1)L)}+1] 2 -1] (7)

[0102] <Selection of prime numbers> As described above, the regions R1 to R6 are (P-1) regions obtained by equally dividing the width direction of the deceleration layer 14, where P is an arbitrary prime number.

[0103] The method of selecting the prime number P is not particularly limited, but as an example, as shown in FIG. 1(A), when the width of the reflective panel is W and the wavelength of the sound to be diffused is λ, it is preferable to select a prime number that is closest to the value represented by W / (λ / 4). In other words, it is preferable to select a prime number that makes the widthwise dimension W1 of each region R closest to (λ / 4). This makes it easier to diffuse the sound to be diffused, which has a wavelength of λ, and sounds with shorter wavelengths than that sound (higher sounds). (See, for example, Journal of the Acoustical Society of Japan, Vol. 42, No. 11, pp. 884--893, 1986.)

[0104] In addition, if there is no limit to the width W of the panel 10, the width W of the panel 10 may be determined by selecting an arbitrary prime number P and arranging (P-1) regions whose width direction dimension W1 is (λ / 4).

[0105] 1A, the deceleration layer 14 is divided into a plurality of regions R along the X direction, but the embodiment of the present disclosure is not limited to this. For example, the deceleration layer 14 may be divided into a plurality of regions along the Y direction, or into a plurality of regions along both the X direction and the Y direction. That is, the deceleration layer 14 may be partitioned into strip-shaped regions such as regions R1 to R6, or into rectangular grid-shaped regions.

[0106] <Example> Assuming that the target sound to be diffused is a sound wave with a frequency of 1500 Hz (λ = 227 mm), select 7 as the prime number P, and the primitive root r p Consider the case where 5 is selected as the width and (P-1)=6 regions R each having a width of (λ / 4)=57 mm are formed.

[0107] Furthermore, if the thickness L of the deceleration layer 14 is 340 mm and the height is 450 mm, and spheres 30 of radius a = 25 mm are placed in each of regions R1 to R6, based on the above formula (5), 15 spheres 30 will be placed in region R1, 30 in region R2, 0 in region R3, 62 in region R4, 46 in region R5, and 79 in region R6.

[0108] Furthermore, if the thickness L of the deceleration layer 14 is 170 mm and the height is 450 mm, and disks 32 having a radius r = 25 mm and a thickness of 2 mm, for example, are placed in each of regions R1 to R6, based on the above equation (6), 12 spheres 30 will be placed in region R1, 24 in region R2, 0 in region R3, 51 in region R4, 38 in region R5, and 66 in region R6.

[0109] <Action and Effects> In the panel 10 according to the embodiment of the present disclosure, as shown in Fig. 1(A), a deceleration layer 14 is disposed in the direction of sound incidence on the reflective panel 12. As shown in Fig. 3(A), a sphere 30 is held as an obstacle whose maximum dimension is smaller than the wavelength λ of the sound to be diffused. Therefore, the sound to be diffused that is incident on the deceleration layer 14 is decelerated by the sphere 30.

[0110] As shown in Fig. 4, the spheres 30 are held at different densities in each of the multiple regions R. Therefore, as shown in Fig. 7, the speed of the sound to be diffused passing through the deceleration layer 14 differs in each region R. As a result, the phase of the reflected sound becomes random with respect to the sound incident on the panel 10.

[0111] This makes the waveform of the sound formed by the interference between the incident sound and the reflected sound, or the interference between the reflected sounds, random. In other words, the distribution of the positions where the sound is amplified by the incident sound and the reflected sound is not concentrated in a specific place in the space. This increases the diffusion of the sound.

[0112] In addition, in the panel 10, the time difference τ required between the region R3 where the time from when the light enters the deceleration layer 14 to when it is reflected by the reflective panel 12 and when it is emitted from the deceleration layer 14 is the fastest and the region R6 where the time is the slowest max is expressed as (λ / 2) / C0. In other words, the phase difference between the reflected sounds in these regions R3 and R6 is (λ / 2).

[0113] When there are two sound waves with a wavelength of λ, the maximum phase difference between these two sound waves is (λ / 2), i.e., the phase difference between the reflected sounds in the regions R3 and R6 is the maximum phase difference.

[0114] As a result, the range of variation in the phases of the reflected sounds in the multiple regions is larger than when these reflected sounds do not have the maximum phase difference, which can improve the diffusivity of the sound.

[0115] In addition, in this panel 10, the time difference between the region R3, which is the region where the time it takes for the sound to enter the deceleration layer 14, reflect off the reflective panel 12, and be emitted from the deceleration layer 14, and the other regions R1, R2, R4, R5, and R6, is τ max ×(m-1) / (P-1), that is, as a linear function of m.

[0116] Since m is a power of (P-1) consecutive integers generated by exponenting the primitive root of the prime number P, it will not be the same value. Therefore, the phase of each reflected sound in each region R will not be the same. This can increase the diffusion of sound.

[0117] In addition, in this panel 10, as derived by the formula (5), the number N of spheres 30 per unit volume in each of the (P-1) regions R is determined according to the radius a of the spheres 30 as obstacles and the thickness L of the deceleration layer 14. m In other words, regardless of the radius a of the sphere and the thickness L of the deceleration layer 14, the phase of each reflected sound in each region R can be changed to increase the diffusivity of the sound.

[0118] Similarly, in this panel 10, as derived by equation (6), the number N of disks 32 per unit volume in each of the (P-1) regions R is determined according to the radius r of the disk 32 as an obstacle and the thickness L of the deceleration layer 14. m In other words, regardless of the radius r of the disk 32 and the thickness L of the deceleration layer 14, the phase of each reflected sound in each region R can be changed to increase the diffusivity of the sound.

[0119] Similarly, in this panel 10, as derived by equation (7), the number N of plates 34 per unit volume in each of the (P-1) regions is determined according to the width d of the plate 34 as an obstacle and the thickness L of the deceleration layer 14. m In other words, regardless of the width d of the plate and the thickness L of the deceleration layer 14, the phase of the reflected sound in each region R can be changed to increase the diffusivity of the sound.

[0120] Furthermore, in this panel 10, the power is generated using (P-1) consecutive integers starting from 10 as the exponent. Therefore, compared to a case where the power is generated using (P-1) consecutive integers starting from 1 as the exponent, the remainder is less likely to be the value of the power itself. This makes it possible to suppress the formation of a sequence of areas with similar phase differences in reflected sounds.

[0121] In addition, in this panel 10, the exponent is generated with the larger primitive root 5 as the base of the prime number 7. Therefore, compared to the case where the exponent is generated with a smaller primitive root as the base, the modular exponentiation is less likely to be the value of the exponent itself. Therefore, it is possible to suppress the formation of a sequence of areas with similar phase differences of reflected sounds.

[0122] According to the above formulas (5) to (7), some of the regions will have no obstacles, but the present disclosure is not limited to this. For example, if the density of obstacles in each region is different, obstacles may be placed in all regions. In other words, the method of determining the number of obstacles in each region does not necessarily have to be based on formulas (5) to (7).

[0123] In addition, in this embodiment, when sound to be diffused with wavelength λ is simultaneously incident on regions R1 to R6 of panel 10, a phase difference of half a wavelength (λ / 2) is generated between the region with the fastest and slowest emission, but the embodiments of the present disclosure are not limited to this.

[0124] For example, it is sufficient that a phase difference of at least half a wavelength (λ / 2) and less than one wavelength (λ) is generated between the fastest and slowest emission regions. According to this aspect, the above formula (1) can be transformed into the following formula (1-1). In the present disclosure, the required time difference τ max can be freely set.

[0125] (λ / 2) / C0≦τ max <λ / C0···(1-1) [Explanation of symbols]

[0126] 10 Panels (acoustic diffusion panels) 12 Reflective Panel 14 Reduction layer 30 Sphere (Obstacle) 32 Discus (Obstacle) 34 Board (Obstacle) R area R1 area R2 area R3 area R4 area R5 area R6 area

Claims

1. A reflective panel that reflects sound, A deceleration layer is arranged in the sound incidence direction of the reflective panel and is divided into a plurality of regions; Obstacles held at different densities in each of the regions; An acoustic diffusion panel equipped with

2. When sound is simultaneously incident on a plurality of the regions, The time difference τ required in the fastest region and the slowest region from when the light enters the deceleration layer to when it is reflected by the reflective panel and when it is emitted from the deceleration layer max teeth, The wavelength of the diffused sound is λ, and the sound speed of the diffused sound is C. ０ As shown in the following formula (I): The acoustic diffusion panel of claim 1 . t max =(λ / 2) / C ０ ・・・(I)

3. The plurality of regions are each a region obtained by dividing the width direction of the deceleration layer into (P-1) regions, where P is an arbitrary prime number, Let m be the remainder when each of the (P-1) powers generated by using the primitive root of the prime number P as the base and exponents of (P-1) consecutive integers is divided by P. The region where the time from when the light enters the deceleration layer to when it is reflected by the reflective panel and when it is emitted from the deceleration layer is the shortest, and the required time difference τ in each of the (P-1) regions ｍ The acoustic diffusion panel of claim 2, wherein: t ｍ =t max ×(m-1) / (P-1)・・・(II)

4. When the obstacles are spheres, the number N of the obstacles per unit volume of each of the (P-1) regions is ｍ teeth, 4. The acoustic diffusion panel of claim 3, wherein a is a radius of the sphere and L is a thickness of the deceleration layer, and the deceleration layer is expressed by the following formula (III). N ｍ ={3 / (2a) ３ )}×[[{(m-1)( / / (4(>-1)L)}+1] ２ -1] ... (III)

5. When the obstacle is a disk whose in-plane direction is perpendicular to the incident direction of the sound to be diffused, the number N of the obstacles per unit volume of each of the (P-1) regions is ｍ teeth, 4. The acoustic diffusion panel of claim 3, wherein the radius of the disk is r and the thickness of the deceleration layer is L, and the acoustic diffusion panel is represented by the following formula (IV):

8. ｍ 4πr(8πr ３ )}×[{(m-1)λ / (4(-1))}+1) ２ -1) ... (IV)

6. When the obstacle is a plate whose in-plane direction is perpendicular to the incident direction of the sound to be diffused, the number N of the obstacles per unit area as viewed from the end face of the obstacle in each of the (P-1) regions is ｍ teeth, 4. The acoustic diffusion panel of claim 3, wherein the width of the plate is d and the thickness of the deceleration layer is L, and the width is expressed by the following formula (V): N ｍ ={4 / (π% ２ )}×[[{(m-1)( / / (4(>-1)L)}+1] ２ -1] ... (V)

7. The acoustic diffusion panel of any one of claims 3 to 6, wherein the consecutive integers are (P-1) integers starting from 10.

8. The acoustic diffusion panel according to any one of claims 3 to 6, wherein when there are a plurality of primitive roots, the largest primitive root is used as the base.

9. The plurality of regions include: When the width of the reflective panel is W and the wavelength of the sound to be diffused is λ, Let P be the prime number closest to the value represented by W / (λ / 4), The deceleration layer is divided into (P-1) equal regions in the width direction. The acoustic diffusion panel according to any one of claims 3 to 6.

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