WO2019182213A1 - Sound absorption device - Google Patents

Abstract

A sound absorption device according to an embodiment of the present invention comprises a plurality of Helmholtz resonators arranged on a plane, wherein each of the plurality of Helmholtz resonators: comprises a neck portion, which has a predetermined thickness and through which a hole extends in the thickness direction, and a chamber portion, which is connected to the neck portion and has an inner space with which sound waves communicate through the hole; and has a resonance frequency different from that of an adjacent Helmholtz resonator.

Description

Sound absorbing device

The present invention relates to a sound absorbing device, and more particularly, to an ultra-thin sound absorbing device capable of absorbing one or more frequencies at a high sound absorption rate.

Efficiently reducing ambient noise is an important consideration in everyday life or in industrial settings. Sound absorption methods used in many industrial sites to reduce noise generated in various mechanical facilities, etc. can be divided into porous type, resonance type and plate type sound absorbing types.

Porous sound absorption method improves sound absorption rate at specific frequency and broadband frequency by adopting appropriate material with high sound absorption performance. Resonance type and plate type sound absorption method partially absorb sound absorption rate at specific frequency by modifying internal structure of sound absorbing material. It's a way to improve.

Existing sound-absorbing technologies have the obvious limitation that thin sound absorber thickness alone cannot expect high sound absorption at low frequencies, and cannot selectively expect high sound-absorbing performance for each frequency when multiple frequencies of noise occur. Therefore, there is a need for a sound absorption technique that allows a designer to select two or more frequencies and to design a sound absorbing device that takes up only a small amount of space.

One aspect of the present invention is to provide a sound absorbing device that is thin and absorbs noise of one or more frequencies at a high sound absorption rate.

Sound absorbing device according to an embodiment of the present invention, a plurality of Helmholtz resonators arranged on a plane, each of the plurality of Helmholtz resonators, the neck portion of a predetermined thickness through which the hole in the thickness direction; And a chamber part connected to the neck and provided with an inner space in which sound waves are communicated through the hole, and having a different resonance frequency from at least one of the adjacent Helmholtz resonators.

A partition wall may be provided in the inner space of at least one of the plurality of Helmholtz resonators to guide the traveling direction of the sound waves.

Each of the plurality of Helmholtz resonators may have at least one of a size of the adjacent Helmholtz resonator and the hole, a thickness of the neck portion, and a volume of the inner space.

The plurality of Helmholtz resonators may have a square pillar shape of the same size, and four Helmholtz resonators may be arranged in a lattice form to form one flaw cell, and the plurality of sound absorbing cells may be arranged in a lattice form on the plane.

The size of the holes may be differently formed between the Helmholtz resonators in which the surfaces of the four Helmholtz resonators contact each other.

The four Helmholtz resonators may be formed to have different sizes of the holes.

The four Helmholtz resonators may have the same volume as the volume of the inner space and the thickness of the neck.

The sound absorption cell may have two or more sound absorption frequencies.

The partition wall is formed with an opening through which the sound wave can pass, and in the Helmholtz resonator provided with the partition wall, a path of the sound wave traveling through the inner space by the inner surface of the chamber part and the partition wall may be defined.

The partition may be guided so that the traveling direction of the sound wave is changed at least once.

The plurality of Helmholtz resonators are eight Helmholtz resonators, some of which are different from each other in the length of the path of the sound waves, the eight Helmholtz resonators adjacent to each other to form a single sound-absorbing cell of the square column shape, The sound absorbing cells may be arranged in a lattice form on the plane.

The eight Helmholtz resonators may have the shape of a polygonal column having the same height, and the holes may have different sizes.

Two Helmholtz resonators of each of the eight Helmholtz resonators may be arranged adjacently to form four square pillars of the same size, and the four square pillar shapes may be adjacent to form the sound absorbing cell.

The eight Helmholtz resonators may have a length of at least three different paths of the sound wave.

The sound absorption cell may have four or more sound absorption frequencies.

The partition wall extends in the thickness direction, and partitions the internal space in the same area on the plane, and the path of the sound wave may be connected through the opening.

The plane may be perpendicular to the direction of incident sound waves, and the holes may be arranged to face the sound waves.

The thickness of each of the plurality of Helmholtz resonators may be smaller than the wavelength of the sound wave.

The sound waves may have different phases reflected from adjacent Helmholtz resonators and may cause destructive interference.

According to an embodiment of the present invention, by arranging a plurality of Helmholtz resonators in combination, noise can be absorbed at a high sound absorption rate.

In addition, it is possible to effectively absorb noise of a plurality of frequencies or noise of a wide frequency band.

In addition, the partition structure which extends the path of a sound wave is formed in a Helmholtz resonator, and it can exhibit a high flaw rate while making thickness very thin.

1 is a perspective view of a scratch device according to an embodiment of the present invention.

2 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the first embodiment of the present invention.

3 is a perspective view of the Helmholtz resonator constituting the sound absorbing cell of FIG.

4 is a front view of a sound absorbing cell constituting the sound absorbing device according to the first embodiment of the present invention.

5 is a graph showing the sound absorption performance of the sound absorbing device according to the first embodiment of the present invention.

6 is a front view of a sound absorbing cell constituting the sound absorbing device according to the second embodiment of the present invention.

7 and 8 are graphs showing the scratching performance of the sound absorbing device according to the second embodiment of the present invention.

9 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the third embodiment of the present invention.

10 is a perspective view illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 9.

11 is a front view of a sound absorbing cell constituting the sound absorbing device according to the third embodiment of the present invention.

12 is a graph showing sound absorption performance of the sound absorbing device according to the third embodiment of the present invention.

It is a perspective view of the sound absorption cell which comprises the sound absorption apparatus which concerns on the 4th Embodiment of this invention.

14 is a front view of a sound absorbing cell constituting the sound absorbing device according to the fourth embodiment of the present invention.

15 to 17 are perspective views illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 14.

18 is a graph showing sound absorption performance of the sound absorbing device according to the fourth embodiment of the present invention.

19 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the fifth embodiment of the present invention.

20 to 23 are perspective views illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 19.

24 is a graph showing sound absorption performance of the sound absorbing device according to the fifth embodiment of the present invention.

25 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the sixth embodiment of the present invention.

FIG. 26 is a perspective view illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 25.

FIG. 27 is a front view illustrating the Helmholtz resonator of FIG. 26.

28 is a graph showing sound absorption performance of the sound absorbing device according to the sixth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like elements throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, the present invention is not necessarily limited to the illustrated.

Throughout the specification, when a part is "connected" to another part, it includes not only "directly connected", but also "indirectly connected" between other members. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

1 is a perspective view of a scratch device according to an embodiment of the present invention.

Referring to FIG. 1, a sound absorbing device 100 according to an exemplary embodiment of the present invention includes a plurality of sound absorbing cells C arranged two-dimensionally on a plane, and has a thin panel or board. ) Form. In the sound absorbing device 100, the sound absorbing cell C may be a basic unit, and the plurality of sound absorbing cells C may be continuously arranged adjacent to each other in the x-axis and y-axis directions with reference to FIG. 1. For example, as shown in FIG. 1, when the sound wave S is incident in the z-axis direction, the plurality of sound absorption cells C may be arranged in a lattice form on an xy plane perpendicular to the incident sound wave.

However, the sound absorbing device 100 of the present invention is not limited to being composed of a plurality of sound absorbing cells C, and the sound absorbing device 100 is formed of only one sound absorbing cell C instead of the plurality of sound absorbing cells C. It may be configured.

The sound absorbing cell C may be composed of a plurality of Helmholtz resonators arranged on a plane. Helmholtz Resonator is a device that absorbs sound by resonating air at a specific frequency. It has a closed shape with a neck and is absorbed by frictional heat loss when air enters and exits through a small hole through the neck. . The Helmholtz resonator may include a neck having a predetermined thickness through which a hole is passed, and a chamber part connected to the neck to provide an inner space, and the neck part and the chamber part may be integrally formed. At this time, the hole may be disposed toward the sound source for generating sound waves, the sound waves may pass through the hole formed in the neck of the Helmholtz resonator to proceed to the interior space of the chamber. Helmholtz resonators are well known to those skilled in the art, and thus will not be described in more detail.

For example, the plurality of Helmholtz resonators constituting the sound absorbing cell (C) may be arranged adjacently so that there is no space therebetween, as shown in Figure 1, the sound absorbing cell (C) in the form of a square column Can be formed.

According to an embodiment of the present invention, each of the plurality of Helmholtz resonators arranged on the plane may be arranged to have a different resonance frequency from the adjacent Helmholtz resonators.

In general, for a Helmholtz resonator, it is widely known that the resonance frequency is determined by the following equation (f is the resonance frequency, v is the speed of sound waves, A is the area of the hole, V is the volume of the inner space, and l is the length of the hole).

That is, since the Helmholtz resonator has a resonant frequency that varies depending on the size (diameter) of the hole, the length of the hole, and the volume of the internal space, each of the plurality of Helmholtz resonators includes at least one size and a neck of the adjacent Helmholtz resonator and the hole 125. At least one of the thickness (length in the z-axis direction) of 122 (see FIG. 3) and the volume of the space 126 (see FIG. 3) may be arranged differently.

In the present specification, the front and the rear define a direction closer to the sound source that generates sound waves, and the rear and rearward directions. Hereinafter, a detailed structure of the sound absorbing device 100 and various sound absorbing effects thereof will be described. Hereinafter, in the description of various embodiments, the structure of the sound absorbing cell constituting the sound absorbing device 100 will be described mainly, and the plurality of sound absorbing cells C are two-dimensionally arranged on a plane in all embodiments.

2 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the first embodiment of the present invention.

1 and 2, according to the first embodiment of the present invention, the plurality of Helmholtz resonators 120 constituting the sound absorbing cell C1 may be arranged in a lattice form on a plane. For example, the plurality of Helmholtz resonators 120 may be arranged in a lattice form on a plane perpendicular to the incident sound wave S so that the reflectance may be zero at a specific frequency of the incident sound wave S. The hole 125 of the Helmholtz resonator 120 may be arranged toward the incident sound wave S. That is, in FIG. 1, when the sound wave S is incident in the z-axis direction, the plurality of Helmholtz resonators 120 are arranged in the x-axis and y-axis directions on the xy plane perpendicular to the incident sound wave S. The hole 125 of the resonator 120 may face the z-axis direction.

According to the first embodiment of the present invention, the sizes of the holes 125 may be differently disposed between the Helmholtz resonators adjacent in at least one direction among the plurality of Helmholtz resonators 120 arranged on the plane. For example, the sizes of the holes 125 may be formed differently between Helmholtz resonators adjacent in two axes (x-axis, y-axis) perpendicular to each other on a plane (xy plane) perpendicular to the incident sound wave S. .

That is, the sound absorbing device 100 according to the embodiment of the present invention may select and absorb a specific frequency by adjusting the size of the holes 125 of the Helmholtz resonators 120 adjacent to each other, and increase one or more specific frequencies. Although the sound absorption can be defected, the detailed structure of the sound absorption cell C1 will be described below.

1 and 2, in the sound absorbing device 100 according to the first embodiment of the present invention, a plurality of sound absorbing cells C1 composed of four Helmholtz resonators 120 have a lattice shape, for example, FIG. 1. It may be configured to have a structure arranged adjacent to the x-axis and y-axis directions in the. That is, the sound absorbing device 100 is a form in which the sound absorbing cells C1 are continuously arranged on a plane, with the fault cell C1 composed of four Helmholtz resonators 120 as a basic unit.

The Helmholtz resonator 120 may have a size smaller than the wavelength of the sound wave S (subwavelength scale). For example, the length of one side of the Helmholtz resonator 120, that is, the thickness of the Helmholtz resonator 120 (H, see FIG. 2) and the length and width of the horizontal and vertical (D / 2, see FIG. 2) is a sound wave (S) It may be smaller than the wavelength of. Thereby, a high scratch effect can be exhibited in a small space. In particular, by reducing the thickness H of the Helmholtz resonator 120, it is possible to function as a meta-surface by attaching a thin-shaped panel-shaped flaw device 100 to the wall.

3 is a perspective view of the Helmholtz resonator constituting the sound absorbing cell of FIG.

Referring to FIG. 3, the Helmholtz resonator 120 has a neck portion 122 having a predetermined thickness through which the hole 125 penetrates, and a space 126 continuously connected to the rear of the neck portion 122 to communicate with the hole 125. It may include the chamber portion 124 is provided. Accordingly, sound waves incident from the outside may enter the internal space through the hole 125.

The Helmholtz resonator 120 may have a polygonal column shape, and a cross section of the Helmholtz resonator 120 in a direction parallel to the plane where the Helmholtz resonator 120 is arranged may have a polygonal shape. For example, the Helmholtz resonator 120 may have a rectangular parallelepiped shape. At this time, as shown in FIG. 3, the neck 122 and the chamber 124 may be integrally formed to form a rectangular parallelepiped. Accordingly, as shown in FIG. 2, the sound absorbing cell C1 may be formed by arranging four Helmholtz resonators in contact with each other.

However, the shape of the Helmholtz resonator 120 is not limited to the shape of a rectangular parallelepiped, but may also be in the form of an oblique column.

Referring to FIGS. 2 and 3, the structure of the Helmholtz resonator 120 having a rectangular parallelepiped shape will be described. For example, the neck 122 and the space 126 through which the hole 125 of a predetermined length (or thickness) 1 is pierced are described. The chamber unit 124 having a) may be integrally formed. The hole 125 has a circular cross section of a predetermined size, extends to connect the space 126 inside and outside the Helmholtz resonator 120 with each other, and may have a predetermined diameter 2r. The space 126 is connected to the rear end of the hole 125 so as to communicate with the hole 125, and the chamber 124 may have a predetermined thickness, so that the space 126 corresponds to the shape of the chamber 124. It may have a rectangular parallelepiped shape. For example, referring to FIG. 3, the space 126 may have a rectangular parallelepiped shape of horizontal (x-axis length), vertical (y-axis length), and depth (z-axis length), respectively, g, a, and b. . However, the shape of the space 126 is not limited to the rectangular parallelepiped, and may be formed in various shapes having a predetermined volume.

On the other hand, as another form of the Helmholtz resonator 120 is not shown in the figure, the chamber portion 124 is a rectangular parallelepiped shape, the neck portion 122 may be formed in a columnar shape, for example, a cylinder protruding on one surface of the rectangular parallelepiped. .

According to the first embodiment of the present invention, the Helmholtz resonator 120 may have a square pillar shape. Accordingly, when the sound absorbing device 100 is viewed from the front (z-axis direction), the sound absorbing cell C1 is also square, and the sound absorbing device 100 may be formed in a lattice form in which square sound absorbing cells C1 are continuously arranged. . For example, referring to FIG. 2, the cross section of the Helmholtz resonator 120 may be a square having a length D / 2, and the cross section of the flaw cell C1 may be a square having a length D of one side.

On the other hand, the sound absorbing device 100 according to the first embodiment of the present invention forms a different size of the hole 125 of the Helmholtz resonator 120 and the Helmholtz resonator 120 having a different size of the hole 125 on the x-axis or By arranging in the y-axis direction, it is possible to exhibit a high defect rate for one or more specific frequencies. Hereinafter, the arrangement of the Helmholtz resonators 120 having different sizes of the holes 125 and the relationship between the holes 125 and the defect frequencies are described. It explains in detail.

4 is a front view of a sound absorbing cell constituting the sound absorbing device according to the first embodiment of the present invention, Figure 5 is a graph showing the sound absorption performance of the sound absorbing device according to the first embodiment of the present invention. For convenience of description, the Helmholtz resonators constituting the sound-absorbing cell (C1) in FIG. 4 is shown with reference numeral 120, four Helmholtz resonators may be referred to as the first to fourth Helmholtz resonators, respectively, as needed in the following description; , 120-1 ~ 120-4. The holes 125 are also divided by the same reference numerals, and may be referred to as needed in the following description. This division method is equally applicable to the description of other embodiments.

3 and 4, according to the first embodiment of the present invention, two types of Helmholtz resonators 120-1 and 120-2 having different sizes of holes 125 are arranged to form one sound absorbing cell ( C1) may be configured. That is, the size of the holes 125-1 and 125-2 may be the same between the Helmholtz resonators arranged in the diagonal direction when viewed from the front among the four Helmholtz resonators constituting one sound absorbing cell C1. That is, the size of the holes may be arranged differently between the Helmholtz resonators in contact with each other. In the case of the sound absorbing device 100 in which the sound absorbing cells C1 having such a structure are arranged, the sound waves S incident toward the sound absorbing device 100 are Helmholtz resonators, that is, holes having different sizes in the x-axis or y-axis direction. The phases reflected by the Helmholtz resonators can be reversed at certain frequencies. In more detail, since the phases reflected from adjacent Helmholtz resonators with different hole sizes are different from each other, destructive interference may be generated, whereby a sound absorption effect may be exerted.

For example, as shown in FIG. 4, the diameters of the holes of the first Helmholtz resonator 120-1 and the second Helmholtz resonator 120-2 which are adjacent in the x-axis or y-axis direction and have different sizes of holes are respectively In the case of 2r ₁ and 2r ₂ , a perfect sound absorption effect can be exhibited at a specific frequency when the following Equation 1 is satisfied.

[Equation 1]

r ₂ = 1.096 × r ₁ + 0.044 [mm]

Here, r ₁ is the radius of the hole 125-1 of the first Helmholtz resonator 120-1, r ₂ is the radius of the hole 125-2 of the second Helmholtz resonator 120-2.

At this time, the sound absorption frequency f _peak at which perfect sound absorption is satisfied satisfies Equation 2 below.

[Equation 2]

_{f peak = 1789 [Hz / mm} ] × r 1 - 1433 [Hz / mm] × r 2 + 131.4 [Hz]

That is, in addition to the diameter of the hole 125 of the Helmholtz resonator 120, when the shape of the Helmholtz resonator 120 is fixed, by adjusting the diameter of the hole 125 of each Helmholtz resonator 120, a perfect at a desired frequency The sound absorption effect can be exhibited.

For example, the shape excluding the diameter of the hole 125 of the Helmholtz resonator 120 is fixed to a = 19mm, b = 25mm, g = 19mm, l = 14mm, D = 41mm, H = 40mm (Fig. 2). 3, that is, when the length of the neck 122 and the volume of the space 125 are fixed except for the diameter of the hole 125 of the Helmholtz resonator 120 and the desired frequency of sound absorption is 700 Hz, substituting the above expression 1 and expression 2, and r ₁ = 2.85mm, it is r ₂ = 3.16mm. Therefore, by adjusting the sound absorbing cell (C) to r ₁ = 2.85mm, r ₂ = 3.16mm in the Helmholtz resonators arranged as shown in Figure 4, it is possible to achieve a perfect sound absorption at 700Hz.

FIG. 5 is a graph showing a reflection coefficient (R _MS ) and a sound absorption coefficient (a _MS ) of a flaw device 100 designed as described above to absorb sound waves having a frequency of 700 Hz through a numerical analysis model. It can be seen that a high sound absorption effect of more than% is exhibited.

In the case of the first embodiment described above, a perfect sound absorbing effect can be exhibited with respect to one specific frequency. However, in the case of the second embodiment described below, a high sound absorbing effect can be achieved with respect to two or more frequencies.

6 is a front view of a sound absorbing cell constituting the sound absorbing device according to the second embodiment of the present invention, and FIGS. 7 and 8 are graphs showing the flaw performance of the sound absorbing device according to the second embodiment of the present invention.

3 and 6, according to the second embodiment of the present invention, four types of Helmholtz resonators 220-1, 220-2, 220-3, and 220-4 with different sizes of the holes 225 are provided. By arranging one sound absorbing cell (C2) can be configured. That is, the four Helmholtz resonators 220-1, 220-2, 220-3, and 220-4, which constitute one sound absorbing cell C2, are holes 225-1, 225-2, 225-3, and 225, respectively. -4) may be formed differently in size. Also in the case of the sound absorbing device 100 in which the sound absorbing cells C2 of this structure are arranged, the sound waves S incident toward the sound absorbing device 100 are respectively reflected in a phase at which the phases reflected between adjacent Helmholtz resonators in the x-axis direction. They may be opposite to each other or destructive interference may occur.

In other words, in the second embodiment of the present invention, sound waves having one target frequency are adjusted by adjusting the diameters of the holes of the two types of Helmholtz resonators 220-1 and 220-2 arranged on the upper portion of the sound absorbing cell C2. It can completely absorb the sound, and by adjusting the diameter of the holes of the two other types of Helmholtz resonators 220-3, 220-4 arranged in the lower portion of the sound absorbing cell (C2) it can completely absorb sound waves having different target frequencies. That is, by adjusting the sizes of the holes of the four Helmholtz resonators 220-1, 220-2, 220-3, and 220-4, which constitute the sound absorbing cell C2, two different frequencies can be completely absorbed. have.

For example, as shown in FIG. 6, the Helmholtz resonators located above the sound absorbing cell C2 and adjacent in the x-axis direction are referred to as a first Helmholtz resonator 220-1 and a second Helmholtz resonator 220-2, respectively. When the diameters of the holes of the first Helmholtz resonator 220-1 and the second Helmholtz resonator 220-2 are 2r ₁ and 2r ₂ , respectively, the target frequencies satisfying the above-described equations 1 and 2 can be obtained. The diameter of the hole, ie r ₁ , r ₂ can be obtained.

In addition, as shown in FIG. 6, when the Helmholtz resonators 220-3 and 4th Helmholtz resonators 220-4 that are positioned below the sound absorbing cell C2 and adjacent in the x-axis direction are respectively When the diameters of the holes of the third Helmholtz resonator 220-3 and the fourth Helmholtz resonator 220-4 are 2r ₃ and 2r ₄ , respectively, for another target frequency that satisfies Equations 1 and 2 described above, The diameter of the hole, i.e. r ₃ , r ₄ can be obtained.

Subsequently, the values of r ₁ , r ₂ , r ₃ and r ₄ can be optimized. More specifically, the diameter of the hole of each Helmholtz resonator can be completely absorbed by the optimization algorithm so that the sound absorption coefficient of the sound absorption cell calculated for the two target frequencies is maximized. At this time, the initial value of the diameter of the hole can be set to the diameter of the hole of the four Helmholtz resonators obtained through the above equations (1) and (2). In addition, the objective function used in the optimization algorithm may be set to maximize the sound absorption coefficient of the sound absorption cell, or may be set to minimize the difference between the acoustic impedance of the outer medium and the effective acoustic impedance of the sound absorption cell. The sequential quadratic programming (SQP) method may be used for the optimization algorithm, but the present invention is not limited thereto, and various well-known methods may be used.

For example, the shape except for the diameter of the hole 225 of the Helmholtz resonator 220 is fixed to a = 19 mm, b = 25 mm, g = 19 mm, l = 14 mm, D = 41 mm, H = 40 mm (Fig. 2). And, in other words, when the thickness of the neck except for the diameter of the hole 225 of the Helmholtz resonator 220 and the volume of the internal space are fixed, and the two desired frequencies for sound absorption are 400 Hz and 600 Hz, Through the above-described optimization method, the diameters of the respective holes of the four Helmholtz resonators 220-1, 220-2, 220-3, and 220-4 constituting the sound absorbing cell C2 are calculated as r ₁ = 1.63 mm and r ₂ = 1.66 mm, r ₃ = 2.45 mm, r ₂ = 2.61 mm.

FIG. 7 is a graph of calculating the reflection coefficient (R _MS ) and the absorption coefficient (a _MS ) through a numerical analysis model of a flaw device 100 designed to absorb sound waves of two frequencies, 400 Hz and 600 Hz. It can be seen that the high sound absorption effect of more than 95% is exhibited at each of the two desired frequencies 400Hz and 600Hz.

As another example, the sound absorption may be efficiently performed at two or more frequencies or a wide frequency band according to the sound absorption frequency. For example, when the two desired frequencies for sound absorption are 400Hz and 500Hz, the diameter of the hole of each Helmholtz resonator is obtained by the above optimization method, and r ₁ = 1.62mm, r ₂ = 1.64mm, r ₃ = 1.86mm, r ₂ = 2.11 mm.

FIG. 8 is a graph of calculating the reflection coefficient (R _MS ) and the absorption coefficient (a _MS ) through a numerical analysis model of a flaw device 100 designed to absorb sound waves of two frequencies, 400 Hz and 500 Hz. It can be seen that a high sound absorption effect of more than 95% is exhibited at 400Hz and 500Hz respectively.

In addition, it can be seen that the high sound absorption effect of more than 95% at 452Hz. This creates an interaction between two Helmholtz resonators designed to have a sound absorption frequency of 400 Hz and two Helmholtz resonators designed to have a sound absorption frequency of 500 Hz, resulting in a new sound absorption frequency (452 Hz) between the two sound absorption frequencies.

Therefore, the size of the holes of the four Helmholtz resonators 220-1, 220-2, 220-3, and 220-4 constituting the intake cell C2 can be adjusted differently so as to be effective in two or more frequencies or a wide frequency band. The sound absorbing device 100 of the present invention can be designed to absorb sound.

On the other hand, in the above embodiments, when the thickness of the neck and the volume of the internal space is constant between a plurality of Helmholtz resonators adjacent to each other, by controlling the size of the hole differently, it is possible to absorb noise having one or more frequencies at a high sound absorption rate The sound absorbing device has been described in detail. However, the present invention is not limited thereto, and a sound absorbing device having the same effect by adjusting at least one of the size of the hole, the thickness of the neck, and the volume of the inner space, which are factors influencing the resonance frequency of the Helmholtz resonator, is provided. Can be implemented.

For example, by varying the size of the hole and the thickness of the neck and adjusting the volume of the inner space differently between a plurality of Helmholtz resonators adjacent to each other, or by making the size of the hole and the volume of the inner space constant and the thickness of the neck different By adjusting, the sound absorption apparatus 100 which exhibits the same effect can be comprised.

In addition, in order to implement a sound absorbing device according to the present invention, after the two factors of the size of the hole, the thickness of the neck and the volume of the internal space between the plurality of Helmholtz resonators adjacent to each other, it is also possible to adjust the other one differently All three factors may be adjusted differently, the size of the hole, the thickness of the neck and the volume of the internal space. The foregoing is equally applicable to other embodiments described below.

In the sound absorbing device 100 according to another embodiment of the present invention, at least one inner space of the plurality of Helmholtz resonators constituting the sound absorbing cell C may be provided with a partition wall for guiding a traveling direction of sound waves entering the inner space. have. Accordingly, it is possible to extend the path of the sound waves, so that the thickness of the sound absorbing device can be implemented to be thin. Hereinafter, another embodiment in which the partition is provided will be described. In the following description, features that are common to the first and second embodiments described above will be omitted and description will be given focusing on differences.

9 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the third embodiment of the present invention, FIG. 10 is a perspective view showing a Helmholtz resonator constituting the sound absorbing cell of FIG. 9, and FIG. It is a front view of the sound absorption cell which comprises the sound absorption apparatus which concerns on 3rd Example. For convenience of understanding, in FIG. 10, the path of sound waves traveling through the inner space of the Helmholtz resonator is shown by a thick solid arrow, and the partition wall is darkly shown. This illustrated method was similarly applied to the drawings of the other embodiments.

1 and 9, the sound absorbing device 100 according to the third embodiment of the present invention has a sound absorbing cell C3 based on a sound absorbing cell C3 including four Helmholtz resonators 320. It is a form arrange | positioned continuously on this xy plane. For example, the square column-shaped sound absorbing cell C3 may be configured with four Helmholtz resonators 320 having a square pillar shape.

9 to 11, when the structure of the Helmholtz resonator 320 having a square pillar shape constituting the sound absorbing cell C3 is exemplarily described, the inner space may have a square pillar shape and may be horizontal (x-axis direction). Length), length (y-axis length), and thickness (z-axis length) may be 2a, 2a, and b, respectively. However, the shape of the inner space is not limited to the square pillar, and may be formed in various shapes having a predetermined volume.

Referring to FIG. 10, the Helmholtz resonator 320 constituting the sound absorbing cell C3 is continuously connected to the neck 122 having a predetermined thickness through which the hole 325 penetrates and the rear of the neck 122. It includes a chamber portion 324 is provided with an internal space in communication with the outside through the sound source. Accordingly, sound waves incident from the outside may enter the internal space through the hole 325.

As described above, at least one of the plurality of Helmholtz resonators 320 may include a partition wall in an inner space. Referring to FIG. 10, in the sound absorbing device according to the third embodiment, a partition wall 327 may be provided in an inner space of each of the four Helmholtz resonators 320 constituting the sound absorbing cell C3.

The partition wall 327 partitions the inner space of the Helmholtz resonator 320 and may exert an effect of extending the path of sound waves traveling in the inner space. According to the exemplary embodiment of the present invention, the traveling direction of the sound wave may be guided at least once by the partition wall 327.

Referring to FIG. 10, the partition wall 327 partitions the inner space of the Helmholtz resonator 320 in the same volume, and may partition the inner space in the same area based on the xy plane, and an opening through which sound waves can pass. 329 may be formed.

For example, when the Helmholtz resonator 320 has a square pillar shape, the inner space may also have a square pillar shape. In this case, the partition wall 327 is formed in a cross shape in which two planes intersect to form an inner space of the same volume. It can be divided into four square columnar spaces. In this case, an opening portion 329 may be formed at an end side of the partition wall 327. Accordingly, the path of the sound wave may be bent and changed several times by the partition wall 327 and the opening part 329. . As a result, as shown in FIG. 10, the sound waves pass through the four spaces divided by the partition wall 327 sequentially through the opening portion 329, so that the path of the sound waves is lower than that without the partition wall 327. Can be extended.

That is, in the Helmholtz resonator 320 provided with the partition wall 327, the path of the sound waves traveling through the inner space by the inner surface of the chamber part 324 and the partition wall 327 is defined, and the structure and the opening of the partition wall 327 are defined. By properly designing the position of the section 329, the path of the sound wave can be extended.

At this time, the thermal viscous effect is increased by the partition wall 327, so that the low sound absorption frequency can be absorbed at a high flaw rate.

In the above equation, when the inner space of the Helmholtz resonator 320 is partitioned by the partition wall 327, the thickness of the thermal viscous boundary layer for the movement of air in the inner space is not negligible compared to the size of the inner space. Since the thermal viscosity dissipation effect on the sound propagation in the space inside the Helmholtz resonator 320 is dominant. As a result, the effective sound velocity (v in the above formula) traveling through the inner space is reduced, resulting in a smaller resonance frequency. Accordingly, it is possible to obtain a high sound absorption effect while having a lower sound absorption frequency than an unpartitioned Helmholtz resonator with the same volume. That is, by making the effective sound velocity small by the partition 327 and lengthening the path | route of a sound wave, the high sound absorption effect can be acquired, having a low sound absorption frequency.

According to the third embodiment of the present invention, the four Helmholtz resonators 320 constituting the sound absorbing cell (C3) are all provided with a partition of the same structure, the length of the path of the sound waves may be all the same. In FIG. 10, the first Helmholtz resonators 320-1 (see FIG. 11) are illustrated, but the second to fourth Helmholtz resonators 320-2 to 320-4 may also have a partition having the same structure. That is, according to the third embodiment, it is possible to extend the path of the sound waves through the partition wall 327, while exhibiting the same sound absorption effect as compared with the sound absorption cell C3 composed of a Helmholtz resonator without the partition wall 327 The thickness of the sound absorbing cell C3 can be made thinner.

For example, the partition wall 327-2 of the second Helmholtz resonator 320-2 has a structure symmetrical to the partition wall 327-1 of the first Helmholtz resonator 320-1 and the xz plane, and also has a first structure. , The partitions 327-1 and 327-2 of the two Helmholtz resonators 320-1 and 320-2 are structures symmetrical to the partition walls of the third and fourth Helmholtz resonators 320-3 and 320-4 and the yz plane. Can be. In addition, the position of the hole 325 may be arranged in the same symmetrical structure.

In general, the smaller the target sound absorption frequency, that is, the longer the wavelength of the sound wave, the thicker the Helmholtz resonator 320 should be in order to have a high sound absorption rate. It has a thickness and high sound absorption at broadband frequencies.

On the other hand, by arranging at least one of the size of the hole 325, the thickness of the neck portion 322, and the volume of the inner space between the adjacent Helmholtz resonators differently, it is possible to adjust so that the phase of the reflected sound wave is reversed.

For example, referring to FIG. 11, the four Helmholtz resonators 320-1, 320-2, 320-3, and 320-4 that make up the sound absorbing cell C3 are holes 325-1 and 325-2, respectively. , 325-3 and 325-4) may have different sizes, and the volume of the inner space and the thickness of the neck may be the same. That is, by adjusting the sizes of the holes of the four Helmholtz resonators 320-1, 320-2, 320-3, and 320-4 constituting the sound absorbing cell C3, a plurality of specific frequencies can be absorbed at a high sound absorption rate. .

More specifically, in the case of designing the sound absorbing device 100 according to the third embodiment of the present invention, for the purpose of sound absorption at the dual frequency, the first and second Helmholtz resonators 320-1 and 320-adjacent to each other in FIG. 11. The size of the holes 325-1 and 325-2 of 2), that is, the values of r ₁ and r ₂ are adjusted to completely absorb sound waves having one target frequency, and the third and fourth Helmholtz adjacent to each other. The size of the holes 325-3 and 325-4 of the resonators 320-3 and 320-4, that is, r ₃ and r ₄ may be adjusted to completely absorb sound waves having another target frequency. have. To this end, the values of r ₁ , r _2, r ₃ , and r ₄ can be adjusted through an optimization algorithm such that the difference between the impedance in the sound absorbing device 100 calculated for the two target frequencies and the impedance of the outside air is minimized. . This is as described in the foregoing embodiment.

12 is a graph showing sound absorption performance of the sound absorbing device according to the third embodiment of the present invention. 12 illustrates the sound absorbing performance after designing the sound absorbing device 100 using the above-described method. More specifically, in Figs. 9 to 11, a = 16 mm, b = 44 mm, l = 5 mm, D = 71 mm, H = 50 mm are fixed, and the target frequency is 300 Hz, 400 Hz, optimization The sound absorbing device 100 according to the third embodiment was designed by deriving r ₁ = 2.20 mm, r ₂ = 2.27 mm, r ₃ = 3.81 mm, and r ₄ = 4.20 mm through an algorithm, and the sound absorption performance of the theory Values, numerical results, and experimental values are shown respectively. Here, the experimental values represent the results of the specimens produced by 3D printing through impedance tube experiments.

12, it can be seen that the sound absorbing device 100 according to the third embodiment of the present invention exhibits a high sound absorbing effect at a plurality of frequencies. The sound absorbing coefficient (a _MS) at two frequencies of 300 Hz and 400 Hz is shown. ) Is 0.95 or more, it can be seen that the sound absorption of 95% or more. In addition, on the basis of 281 Hz, which is the lowest frequency having a sound absorption rate of 80% or more, the thickness of the sound absorbing device is 1 / 24.4 times the incident wavelength.

Hereinafter, a sound absorbing device according to a fourth embodiment capable of absorbing a wideband frequency as compared with the third embodiment described above will be described.

13 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the fourth embodiment of the present invention, and FIG. 14 is a front view of the sound absorbing cell constituting the sound absorbing device according to the fourth embodiment of the present invention. 15 to 17 are perspective views illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 14.

13 and 14, the sound absorbing device according to the fourth embodiment of the present invention includes a sound absorbing cell C4 composed of eight Helmholtz resonators 420, and the sound absorbing cell C4 is continuous on a plane. It is arranged as. For example, a square column-shaped sound absorbing cell C4 may be configured of eight Helmholtz resonators 420 having a polygonal pillar shape having the same height and having various bottom surfaces.

13 to 17, the sound absorbing cell C4 may include four pairs of Helmholtz resonators 420, and are arranged adjacent to each other such that there is no space therebetween to form a square sound absorbing cell C4. can do. In this case, the four pairs of Helmholtz resonators 420 constituting the sound absorbing cell C4 may be formed in different sizes of the holes 425. More precisely, the size of the holes 425 may be formed differently between the paired Helmholtz resonators 420, and the size of the holes 425 may be adjusted so that the phases of the reflected sound waves are reversed. Thereby, a high sound absorption effect can be exhibited with respect to a some frequency.

Further, according to the fourth embodiment of the present invention, among the four pairs of Helmholtz resonators 420 constituting the sound absorbing cell C4, the path length of the sound wave in the inner space is the same. Can be formed. Alternatively, the structure of the partition wall 429 provided in the inner space may be the same between the pair of Helmholtz resonators 420. For example, between paired Helmholtz resonators, it may have a structure of a hole and a location of a hole symmetrical in the xz plane.

According to the fourth embodiment of the present invention, the third and fourth Helmholtz resonators 420-3 and 420-4 which are different from the paired first and second Helmholtz resonators 420-1 and 420-2 are sound waves. The lengths of the paths may be different from each other, and thus, sound absorption for the wideband frequency may be realized. As mentioned earlier, the smaller the target sound absorption frequency (or the longer the wavelength of sound waves), the thicker the Helmholtz resonator 420 should be in order to have a high sound absorption rate. The same effect as the thickness of 420 becomes thick can be exhibited.

15 and 16, the first and second Helmholtz resonators 420-1 and 420-2 have a hexagonal column having a 'L' shape at the bottom thereof, and a path of sound waves may be extended by the partition wall. In addition, the third and fourth Helmholtz resonators 420-3 and 420-4 have a rectangular columnar shape that can be in contact with the concave side surfaces of the first and second Helmholtz resonators 420-1 and 420-2, There may be no bulkhead. Referring to FIG. 15, the first Helmholtz resonator 420-1 is provided with a partition 427-1 in an internal space, and the partition 427-1 partitions an internal space of the first Helmholtz resonator 420-1. Two planes perpendicular to each other may be coupled to each other, and the openings 429-1 may be formed at ends of opposite directions.

In the fourth embodiment of this structure, in the case of the first Helmholtz resonator 420-1 shown in FIG. 15, the length of the sound wave in the thickness direction (z-axis direction) is the third Helmholtz without the partition shown in FIG. Compared to the resonator 420-3 can be extended more than three times. Accordingly, the first and second Helmholtz resonators 420-1 and 420-2 can exhibit a high sound absorption effect at a low frequency, and the third and fourth Helmholtz resonators 420-3 and 420-4 have a high frequency. High sound absorption effect can be achieved.

Accordingly, according to the fourth embodiment, by including a Helmholtz resonator having different lengths of sound wave paths in one sound absorbing cell C4, a high sound absorbing effect can be obtained even when the target sound absorption frequency is large. . In other words, it can exhibit a high sound absorption effect at a wide band frequency.

13, 14, and 17, the fifth to eighth Helmholtz resonators 420-5 to 420-8 may have a rectangular pillar shape of the same size, and may have the same path of sound waves. Alternatively, a partition of the same structure may be provided in the interior space. For example, referring to FIG. 17, a partition 427-5 is provided in an inner space of the fifth Helmholtz resonator 420-5, and is located far from the hole 425-5 at an end of the partition 427-5. Openings 429-5 may be formed at the ends of the direction. Accordingly, the sound wave passing through the hole 425-5 progresses in the z-axis direction, and the traveling direction is changed through the opening portion 429-5 to proceed in the -z-axis direction, so that the path length of the sound wave is extended. Can be.

At this time, the fifth to eighth Helmholtz resonators 420-5 to 420-8 have shorter sound paths than the first and second Helmholtz resonators 420-1 and 420-2, but the third and fourth Helmholtz resonators Compared to the resonators 420-3 and 420-4, it may have a longer path of sound waves. That is, the plurality of Helmholtz resonators 420 constituting the sound absorption cell C4 may have paths of at least three different sound waves, and may have at least four sound absorption frequencies (see FIG. 18 to be described below). Accordingly, according to the fourth embodiment, it can be implemented to enable a high sound absorption rate for the frequency of the broadband.

In the case of designing the sound absorbing device 100 according to the fourth embodiment of the present invention, for the purpose of sound absorption of multiple frequencies or broadband frequencies, the first and second Helmholtz resonators 420-1, which are adjacent to each other in FIGS. 13 and 14, 420-2) is designed to completely absorb sound waves having a first target frequency by adjusting the sizes of the holes 425-1 and 425-2, that is, the values of r ₁ and r ₂ . The size of the holes 425-3 and 425-4 of the Helmholtz resonators 420-3 and 420-4, that is, r ₃ and r _4, can be adjusted to completely absorb sound waves having the second target frequency. Can be. In addition, the size of the holes 425-5 and 425-6 of the fifth and sixth Helmholtz resonators 420-5 and 420-6, that is, the values of r ₅ and r ₆ , are adjusted to have a third target frequency. Designed to completely absorb sound waves, and by adjusting the size of the holes (425-7, 425-8) of the seventh and eighth Helmholtz resonators (420-7, 420-8) adjacent to each other, that is, r ₇ , r ₈ It can be designed to completely absorb sound waves having a fourth target frequency. In the same manner as described in the above embodiment, r ₁ , r ₂ , through optimization algorithms such that the difference between the impedance in the sound absorbing device 100 and the impedance of the outside air is minimized. r ₃ , r ₄ , r ₅ , r ₆ , You can adjust the r ₇ and r ₈ values.

18 is a graph showing sound absorption performance of the sound absorbing device according to the fourth embodiment of the present invention.

18 illustrates the sound absorption performance after designing the sound absorbing device 100 according to the fourth embodiment by using the above-described method. More specifically, in Figs. 13 to 17, a = 16 mm, b = 44 mm, l = 5 mm, D = 71 mm, H = 50 mm are fixed, and the target frequencies are 300 Hz, 400 Hz, 500 Hz, With 600 Hz, the optimization algorithm allows r ₁ = 1.77 mm, r ₂ = 1.78 mm, r ₃ = 2.010 mm, r ₄ = 2.014 mm, r ₅ = 2.56 mm, r ₆ = 2.66 mm, r ₇ = 1.91 mm , r ₈ = 1.92 mm was derived and the sound absorbing device 100 according to the fourth embodiment was designed, and the sound absorbing performance thereof was shown as a theoretical value and a numerical analysis result, respectively.

Referring to FIG. 18, it can be seen that the sound absorbing device 100 according to the fourth embodiment of the present invention exhibits high sound absorption at four frequencies, and includes four frequencies of 300 Hz, 400 Hz, 500 Hz, and 600 Hz. Since the sound absorption coefficient (a _MS ) is 0.95 or more, it can be seen that the sound absorption rate of 95% or more can be exhibited. In addition, it can be confirmed that the sound absorbing device 100 according to the fourth embodiment of the present invention is effective for a wideband frequency. A frequency bandwidth capable of exhibiting a sound absorption rate of 50% or more is 36 Hz and 300 Hz target frequencies based on a 300 Hz target frequency. The reference is 44 Hz and 500 Hz. The target frequency is 55 Hz and 600 Hz. The target frequency is 52 Hz. In addition, on the basis of 293 Hz, the lowest frequency having a sound absorption rate of 80% or more, the thickness of the sound absorbing device is 1 / 23.4 times the incident wavelength. Therefore, while implementing a sound absorbing device having a thin thickness similar to the third embodiment, it is possible to implement a sound absorbing device 100 exhibiting a high sound absorption rate for more frequencies and broadband frequencies than the third embodiment.

Hereinafter, the sound absorbing apparatus according to the fifth embodiment which more reliably exhibits a high sound absorption rate with respect to the broadband frequency compared with the above-described fourth embodiment will be described.

19 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the fifth embodiment of the present invention, and FIGS. 20 to 23 are perspective views illustrating a Helmholtz resonator constituting the sound absorbing cell of FIG. 19.

19 and 20, the sound absorbing device according to the fifth embodiment of the present invention includes a sound absorbing cell C5 composed of eight Helmholtz resonators 520, and the sound absorbing cell C5 includes eight Helmholtz resonators. Two Helmholtz resonators of 520 are arranged adjacent to each other to form four square pillars of the same size, and the four square pillars are arranged adjacent to form a square-shaped sound absorption cell C5. have.

19 to 23, the sound absorbing cell C5 may include four pairs of Helmholtz resonators 520, and are arranged adjacent to each other so that there is no space therebetween to form a square sound absorbing cell C5. can do. In this case, the four pairs of Helmholtz resonators 520 constituting the sound absorbing cell C5 may have different volumes of internal space. More precisely, a pair of Helmholtz resonators may have the same internal space, but different pairs of Helmholtz resonators may have different internal volumes. Thereby, a high sound absorption effect can be exhibited with respect to a some frequency.

In addition, according to the fifth embodiment of the present invention, among the four pairs of Helmholtz resonators 520 constituting the sound absorbing cell C5, the path length of the sound wave in the inner space may be the same. have. Alternatively, the structure of the partition wall 527 provided in the inner space may be the same between the pair of Helmholtz resonators. For example, between paired Helmholtz resonators, it may have a structure of a hole and a location of a hole symmetrical in the xz plane.

On the other hand, according to the fifth embodiment of the present invention, unlike the third and fourth embodiments described above, the neck portion of the Helmholtz resonator 520 in which the internal space is not formed is more than only a part of the front of the Helmholtz resonator 520. Specifically, only the hole 525 is formed in a portion, and the remaining portion may be formed in the inner space without extending the neck portion. For example, in FIG. 20, the length of the z-axis direction of the inner space directly connected to the hole 525-1 is b, but the z-axis direction of the inner space of the upper position (y-axis direction) of the hole 525-1. The length of becomes b + l. Through this, the volume of the neck can be minimized to increase the internal space, and the path of the sound wave can be made longer.

According to the fifth embodiment of the present invention, paired first and second Helmholtz resonators 520-1 and 520-2, third and fourth Helmholtz resonators 520-3 and 520-4, and fifth and sixth Helmholtz The resonators 520-5 and 520-6 and the seventh and eighth Helmholtz resonators 520-7 and 520-8 may have different path lengths of sound waves, and thus, sound absorption for broadband frequencies may be realized. have. That is, by appropriately arranging a plurality of Helmholtz resonators with different paths of sound waves, high sound absorption can be exhibited for multiple frequencies and wideband frequencies.

19, 20, and 21, the first Helmholtz resonator 520-1 has an irregular shape in which a part of a square pillar is divided, and a path of sound waves may be extended by a partition wall. In addition, the third Helmholtz resonator 520-3 may be in contact with the concave side surface of the first Helmholtz resonator 520-1, and the first Helmholtz resonator 520-1 and the third Helmholtz resonator 520- 3) may be arranged adjacent to each other to form a square pillar.

19, 22, and 23, the fifth Helmholtz resonator 520-5 is an irregular shape in which part of the square pillar is divided, and is different from the first Helmholtz resonator 520-1. The structure may be formed differently from the first Helmholtz resonator 520-1. In addition, the seventh Helmholtz resonator 520-7 may be in contact with the concave side of the fifth Helmholtz resonator 520-5, and the fifth Helmholtz resonator 520-5 and the seventh Helmholtz resonator 520- 7) may be arranged adjacent to each other to form a square pillar.

That is, according to the fifth embodiment, two Helmholtz resonators of the eight Helmholtz resonators constituting the sound absorption cell C5 are arranged adjacent to each other to form four square pillar shapes of the same size, and the four square pillar shapes. May be arranged adjacent to each other to form the sound absorption cell.

More specifically, in the above-described fourth embodiment, the Helmholtz resonators 420 constituting the sound absorbing cell C4 have the same thickness (the length in the z-axis direction), and two Helmholtz resonators adjacent to each other have the square pillar in the x-axis. And in the form of the incision only in the y-axis direction, in the fifth embodiment, two Helmholtz resonators adjacent to each other among the Helmholtz resonators 520 constituting the sound-absorbing cell (C5) as well as the x-axis and y-axis direction It is also cut in the z-axis direction. In the fifth embodiment of this structure, the shape of the Helmholtz resonator constituting the sound absorbing cell can be more variously compared with the above-described fourth embodiment, so that the design freedom is high, and thus the length of the path of the sound wave is more precisely. I can adjust it.

Accordingly, according to the fifth embodiment, by including various Helmholtz resonators having different lengths of sound wave paths in one sound absorbing cell C5, the difference between target sound absorption frequencies can be reduced, thereby wideband frequency. High sound-absorption effect can be clearly seen at. That is, the plurality of Helmholtz resonators 520 constituting the sound absorbing cell C5 may have four different sound wave paths and may have four sound absorption frequencies.

In the case of designing the sound absorbing device 100 according to the fifth embodiment of the present invention, it is optimized to minimize the difference between the impedance of the sound absorbing device 100 and the impedance of the outside air in the same manner as described in the previous embodiment. Through the algorithm r ₁ , r ₂ , r ₃ , r ₄ , r ₅ , r ₆ , You can adjust the r ₇ and r ₈ values.

24 is a graph showing sound absorption performance of the sound absorbing apparatus according to the fifth embodiment of the present invention.

FIG. 24 illustrates a sound absorbing performance after designing the sound absorbing device 100 according to the fifth embodiment shown in FIGS. 19 to 23. More specifically, in Figs. 19 to 23, a = 16 mm, b = 46 mm, l = 5 mm, D = 71 mm, H = 52 mm are fixed, and the target frequencies are 370 Hz, 420 Hz, 475 Hz, With 530 Hz, r ₁ = 2.23 mm, r ₂ = 2.23 mm, r ₃ = 2.45 mm, r ₄ = 2.58 mm, r ₅ = 2.22 mm, r ₆ = 2.27 mm, r ₇ = 2.36 mm through an optimization algorithm , r ₈ = 2.37 mm was derived to design the sound absorbing device 100 according to the fifth embodiment. Sound absorption performance is shown as theoretical value, numerical analysis result, and experimental value, respectively. Here, the experimental values represent the results of the specimens produced by 3D printing through impedance tube experiments.

Referring to FIG. 24, it can be seen that the sound absorbing device 100 according to the fifth embodiment of the present invention exhibits a high sound absorption effect at four frequencies, and includes four frequencies of 375 Hz, 425 Hz, 472 Hz, and 536 Hz. Since the sound absorption coefficient (a _MS ) is 0.95 or more, it can be seen that the sound absorption rate of 95% or more can be exhibited. In addition, it can be seen that the sound absorbing device 100 according to the fifth embodiment of the present invention is very effective for a wideband frequency. The frequency bandwidth capable of exhibiting a sound absorption rate of 50% or more is 344 Hz to 533 Hz, which is a total of 209 Hz. . In addition, on the basis of 357 Hz, which is the lowest frequency having a sound absorption rate of 80% or more, the thickness of the sound absorbing device relative to the incident wavelength is 1 / 18.5 times. Therefore, although the thickness is slightly thicker than that of the fourth embodiment, it is possible to implement the sound absorbing device 100 which exhibits a high sound absorption rate for a much wider frequency band.

Hereinafter, a sound absorbing device according to a sixth embodiment that can be implemented in a thin thickness than the above-described embodiment will be described.

FIG. 25 is a perspective view of a sound absorbing cell constituting the sound absorbing device according to the sixth embodiment of the present invention. FIG. 26 is a perspective view showing a Helmholtz resonator constituting the sound absorbing cell of FIG. 25, and FIG. 27 is a perspective view of FIG. Front view showing a Helmholtz resonator.

25 to 27, the sound absorbing device according to the sixth embodiment of the present invention includes a sound absorbing cell C6 including four Helmholtz resonators 620, and based on the fault cell C6 as a basic unit. The sound absorbing cells C6 are continuously arranged on a plane. For example, the square column-shaped sound absorbing cell C6 may be configured with four Helmholtz resonators 620 having the same size as the square column having a smaller height than the size of the bottom surface.

25 to 27, the sound absorbing cell C6 may include four Helmholtz resonators 620, and are arranged adjacent to each other so that there is no space therebetween to form a square sound absorbing cell C6. Can be. At this time, the four Helmholtz resonators 620 constituting the sound absorbing cell (C6) may be formed in all different sizes of the holes 625. More precisely, the size of the hole 625 can be adjusted so that the phase of the sound waves reflected between two adjacent Helmholtz resonators 620 or two paired Helmholtz resonators is reversed. Thereby, a high sound absorption effect can be exhibited with respect to a some frequency.

In addition, according to the sixth embodiment of the present invention, the four Helmholtz resonators 620 constituting the sound absorbing cell C6 may have the same length of the path of sound waves in the internal space. Alternatively, the four helmholtz resonators 620 constituting the sound absorbing cell C6 may have the same structure of the partition wall 629 provided in the internal space.

For example, each of the four Helmholtz resonators 620 may be formed with a partition 629 so that the path of the sound waves traveling in the inner space is rounded. Through this, it is possible to implement a sound absorbing device of very thin thickness. As mentioned above, the length of the path of the sound wave can be extended while increasing the thermal viscous effect through the partition structure. Referring to FIGS. 26 and 27, the z-axis of the Helmholtz resonator 620 is increased while increasing the area. The thickness of the direction may be reduced, and the partition 629 may be configured to have a path of sound waves on the xy plane. Through this, it is possible to minimize the thickness of the sound absorbing device while maximizing the effect of extending the path of sound waves.

More specifically, referring to FIGS. 26 and 27, the first Helmholtz resonator 620-1 has a square pillar shape having a height smaller than that of the bottom surface, and the path of the sound wave is extended by the partition wall 627-1. Can be. For example, based on the xy plane of FIG. 27, the partition wall 627-1 may be formed to partition the inner space of the first Helmholtz resonator 620-1 to the same area or to partition the inner space into a lattice shape. Can be. At this time, the partition wall 627 so that the sound wave incident to the hole 625-1 proceeds in a path of turning in a direction away from the hole 625-1 with respect to the hole 625-1 with respect to the xy plane. A plurality of openings 629-1 may be formed at −1).

26 and 27, the partition wall 627-1 is in the form of a flat plate extending in the thickness direction (z-axis direction), and as shown in FIG. 27, in the x-axis and y-axis directions with respect to the xy plane. Alternately, it may be in a form of bending multiple times. That is, the opening 629-1 may be disposed in the partition wall 627-1 so as to induce a path in which sound waves turn round. Accordingly, the sound waves incident on the hole 625-1 may not travel in the z-axis direction, which is the thickness direction, but may travel in a path that is alternately bent several times in the x- and y-axis directions.

For example, referring to FIG. 27, the partition wall 627-1 extends in the x-axis and y-axis directions to partition the internal space in a lattice form based on the xy plane, wherein the opening portion 629- 1) may be formed in a form in which the intermediate wall 627-1 extending in the x- and y-axis directions is emptied so as not to be continuously connected.

Referring to FIGS. 26 and 27, the path of the sound wave may rotate around the xy plane in a counterclockwise or clockwise direction. As a result, the path of the sound waves traveling through the inner space of the first Helmholtz resonator 620-1 may be maximized, and thus the thickness of the first Helmholtz resonator 620-1 may be designed to be very thin. Furthermore, in the case of the sixth embodiment, the more partitioned the partition 627-1 partitions the internal space, the greater the thermal viscosity effect and the longer the path of the sound waves, and thus, the higher the sound absorption rate at the same target frequency. When the sound absorption is to be carried out, the thickness of the sound absorbing device 100 may be implemented to be thinner.

26 and 27 illustrate only the first Helmholtz resonators 620-1 of the four Helmholtz resonators 620 constituting the sound absorption cell C6 according to the sixth embodiment, but the second to fourth Helmholtz resonators 620- 2 to 620-4), a partition wall having the same structure as that of the first Helmholtz resonator 620-1 may be provided. For example, a pair of Helmholtz resonators may have a structure of a partition and a position of a hole symmetrical on the x-axis. That is, the partition 627-2 of the second Helmholtz resonator 620-2 has a structure that is symmetrical to the partition 627-1 of the first Helmholtz resonator 620-1 and the x-axis, and the first and the second The partitions 627-1 and 627-2 of the Helmholtz resonators 620-1 and 620-2 may have a structure symmetrical to the partition walls and the y-axis of the third and fourth Helmholtz resonators 620-3 and 620-4. .

In the case of designing the sound absorbing device 100 according to the sixth embodiment of the present invention, for the purpose of sound absorption at the dual frequency, the holes of the first and second Helmholtz resonators 620-1 and 620-2 adjacent to each other in FIG. The third and fourth Helmholtz resonators 620- are designed to completely absorb sound waves having a single target frequency by adjusting the magnitudes of 625-1 and 625-2, that is, r ₁ and r ₂ . The size of the holes 625-3 and 625-4, ie, r ₃ and r ₄ , of ₃ and 620-4 may be adjusted to completely absorb sound waves having another target frequency. To this end, the values of r ₁ , r _2, r ₃ , and r ₄ can be adjusted through an optimization algorithm such that the difference between the impedance in the sound absorbing device 100 calculated for the two target frequencies and the impedance of the outside air is minimized. Is the same as in the above-described embodiment.

28 is a graph showing sound absorption performance of the sound absorbing device according to the sixth embodiment of the present invention. 28 illustrates the sound absorption performance after designing the sound absorbing device 100 using the method described above. More specifically, in Fig. 26, a = 17.75 mm, b = 17.75 mm, l = 5 mm, D = 149 mm, H = 23.75 mm, and the target frequency 200 Hz, 250 Hz, through an optimization algorithm The sound absorbing device 100 according to the sixth embodiment was designed by deriving r ₁ = 2.21 mm, r ₂ = 2.24 mm, r ₃ = 3.68 mm, r ₄ = 3.77 mm, and the sound absorption performance of the theoretical value, and The numerical results are shown respectively.

Referring to Figure 28, the sound-absorbing device 100 in accordance with a sixth embodiment of the present invention may determine that exert a high sound absorption effect at a plurality of frequencies, 200 Hz, 250 Hz two kinds of sound absorption coefficient at a frequency (a _MS ) Is 0.95 or more, it can be seen that the sound absorption of 95% or more. In addition, the thickness of the sound absorbing device 100 can be greatly reduced, and the sound absorbing device 100 has a thickness of 1 / 73.7 times compared to the incident wavelength on the basis of 196 Hz, which is the lowest frequency having a sound absorption rate of 80% or more. Accordingly, similar to the third embodiment, it can be seen that the sound absorption device 100 having a very high sound absorption rate for the dual frequency can be implemented compared to the third embodiment.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

Description of the sign

100 sound absorbing device

120, 220, 320, 420, 520, 620 Helmholtz resonators

125, 225, 325, 425, 525, 625 holes

C, C1, C2, C3, C4, C5, C6 Sound Absorption Cells

S sound wave

Claims (19)

1. A plurality of Helmholtz resonators arranged on a plane,

   Each of the plurality of Helmholtz resonators,

   A neck having a predetermined thickness through which a hole passes in the thickness direction; And a chamber part connected to the neck and provided with an inner space in which sound waves are communicated through the hole, wherein the chamber part has a different resonance frequency from at least one of the adjacent Helmholtz resonators.
2. The method of claim 1,

   Sound absorbing device is provided with a partition wall for guiding the traveling direction of the sound wave in the inner space of at least one of the plurality of Helmholtz resonators.
3. The method of claim 1,

   Each of the plurality of Helmholtz resonators is a sound absorbing device, wherein at least one of the size of the adjacent Helmholtz resonator and the hole, the thickness of the neck, and the volume of the inner space are different.
4. The method of claim 1,

   The Helmholtz resonators are in the form of square pillars of the same size,

   Four Helmholtz resonators are arranged in a grid to form one flaw cell,

   A flaw device, in which a plurality of said sound absorbing cells are arranged in a lattice form on said plane.
5. The method of claim 4, wherein

   Sound absorbing device of the four Helmholtz resonators are formed with different sizes of the hole between the Helmholtz resonators in contact with each other.
6. The method of claim 5,

   The four Helmholtz resonators are each formed of a different size of the hole, sound absorbing device.
7. The method of claim 5,

   And the four Helmholtz resonators have the same volume as that of the inner space and the thickness of the neck.
8. The method of claim 4, wherein

   The sound absorbing cell has a sound absorbing frequency of two or more.
9. The method of claim 2,

   The partition is formed with an opening through which the sound wave can pass,

   In the Helmholtz resonator provided with the said partition, the path | route of the said sound wave which advances the said inner space by the inner surface of the said chamber part, and the said partition is defined.
10. The method of claim 2,

    The sound absorption device is guided so that the traveling direction of the sound wave is changed at least once by the partition wall.
11. The method of claim 9,

    The plurality of Helmholtz resonators are eight Helmholtz resonators, some of which are different from each other and the length of the path of the sound waves,

    The eight Helmholtz resonators are adjacent to each other to form a single sound-absorbing cell in the form of a square column,

    A flaw device, in which a plurality of said sound absorbing cells are arranged in a lattice form on said plane.
12. The method of claim 11,

    The eight Helmholtz resonators

    Sound absorption device of the same height polygonal column shape, the size of the hole is formed different.
13. The method of claim 11,

    And two Helmholtz resonators of each of the eight Helmholtz resonators arranged adjacent to form four square pillars of the same size, and the four square pillar shapes arranged adjacent to form the sound absorbing cell.
14. The method of claim 11,

    And the eight Helmholtz resonators have a length of at least three different paths of the sound wave.
15. The method of claim 14,

    The sound absorbing device has a sound absorption frequency of four or more.
16. The method of claim 9,

    The partition wall extends in the thickness direction and partitions the internal space on the plane in the same area,

    A sound absorbing device, the path of the sound wave is connected through the opening.
17. The method of claim 1,

    The plane is perpendicular to the direction of the incident sound wave,

    Wherein the hole is arranged to face the sound wave.
18. The method of claim 1,

    And a thickness of each of the plurality of Helmholtz resonators is smaller than the wavelength of the sound wave.
19. The method of claim 1,

    The sound wave is a sound absorbing device, the phases reflected from the Helmholtz resonators adjacent to each other to cause a destructive interference.

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