Low-frequency broadband sound absorption and noise reduction structure and range hood

Abstract

The invention discloses a low-frequency broadband sound absorption and noise reduction structure and a range hood, the sound absorption and noise reduction structure comprises a porous material base plate and rigid insertion plates, the porous material base plate is provided with a target surface, a plurality of rigid insertion plates are arranged on the target surface along a first direction and embedded in the porous material base plate, and the rigid insertion plates are arranged on the target surface along the first direction; the lengths of the rigid inserting plates are gradually increased in the first direction, and the first direction is perpendicular to the structural noise radiation direction. By regulating and controlling the number, the size and the distribution position of the rigid inserting plates on the porous material base body plate, structural radiation noise and mechanical noise in a flow field environment and a flow-field-free environment are reduced, the noise reduction effect in different main noise distribution directions is enhanced, and low-frequency noise reduction in a compact space and under a small thickness is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of noise reduction, and in particular to a low-frequency, broadband sound absorption and noise reduction structure and a range hood. Background Art

[0002] Existing low-frequency broadband noise reduction solutions mostly use porous materials, micro-perforated plates and Helmholtz resonators, and their sound absorption mechanism is micro-thermal viscous loss and local resonance. Helmholtz resonators can achieve low-frequency sound absorption under thickness constraints, but the bandwidth is narrow; although micro-perforated plates can broaden the noise reduction frequency band through parameter optimization, they can only achieve noise reduction in the mid-frequency band; porous materials use the viscous heat loss and friction of air in the gaps of porous materials to attenuate the incident sound energy for noise reduction, but they mainly achieve mid- and high-frequency noise reduction.

[0003] In the noise reduction design application of range hoods, due to the compact noise reduction space and thin thickness of porous materials, the traditional sound-absorbing and noise reduction structure has limited ability to reduce medium and low frequency noise, and it is difficult to achieve low-frequency broadband noise control at a relatively thin thickness. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defect that the traditional sound absorption and noise reduction structure in the prior art is difficult to achieve low-frequency noise reduction in a compact space and with a thin thickness, and to provide a low-frequency and broadband sound absorption and noise reduction structure and a range hood.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] In a first aspect, the present invention provides a low-frequency, broadband sound absorption and noise reduction structure, comprising: a porous material base plate and a rigid plug plate, the porous material base plate having a target surface, a plurality of the rigid plug plates being arranged on the target surface along a first direction and embedded in the interior of the porous material base plate, and the lengths of the plurality of the rigid plug plates gradually increase along the first direction, and the first direction is perpendicular to the radiation direction of the structural noise.

[0007] Preferably, the lengths of the plurality of rigid plug plates are arranged in an arithmetic progression and at equal intervals along the first direction.

[0008] Preferably, the length of the rigid plugboard is calculated by the following formula:

[0009] b i =di(db N ) / N(i=1,2,…,N)

[0010] Among them, b i represents the length of the i-th rigid plug plate, N represents the number of the rigid plug plates, d represents the minimum length of the porous material substrate along the second direction, b Nrepresents the shortest length of the rigid board along the first direction, and the second direction is parallel to the structural noise radiation direction.

[0011] Preferably, the ratio of the total area occupied by the plurality of rigid plug boards in the target surface to the area of ​​the target surface is in the range of 8%-30%.

[0012] Preferably, the maximum length of the rigid plugboard on the target surface is smaller than the length of the target surface.

[0013] Preferably, the length of the rigid plug plate along the direction perpendicular to the first direction is smaller than the minimum length of the porous material base plate along the direction perpendicular to the first direction.

[0014] Preferably, the porous material base plate is wedge-shaped and is made of melamine foam.

[0015] Preferably, the porosity of the porous material substrate is 0.93, and the flow resistance is 11000-14000 Pa·s / m 2 , the tortuosity is 1.07, the thermal characteristic length is 273 μm, and the viscous characteristic length is 672 μm.

[0016] Preferably, the rigid plug board is made of resin material, and the density of the resin material is 1230 kg / m 3 .

[0017] In a second aspect, the present invention provides a range hood comprising the low-frequency, broadband sound absorption and noise reduction structure described in the first aspect, the range hood comprising an air duct and a centrifugal fan located inside the air duct, the low-frequency, broadband sound absorption and noise reduction structure being arranged on the inner surface of the air duct, and the target surface of the low-frequency, broadband sound absorption and noise reduction structure facing the centrifugal fan.

[0018] The positive progressive effect of the present invention is to provide a low-frequency, broadband sound absorption and noise reduction structure and a range hood, which reduces the structural radiation noise and mechanical noise in flow field environments and non-flow field environments by adjusting the number, size and distribution position of the rigid plug-in plates on the porous material base plate, enhances the noise reduction effect in different main noise distribution directions, and achieves low-frequency noise reduction in a compact space and with a relatively thin thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a first structural schematic diagram of the low-frequency, broadband sound absorption and noise reduction structure of Example 1 of the present invention.

[0020] Figure 2 This is a second structural schematic diagram of the low-frequency, broadband sound absorption and noise reduction structure of Example 1 of the present invention.

[0021] Figure 3aIt is a schematic diagram of the sound absorption superstructure in the theoretical modeling of the low-frequency, broadband sound absorption and noise reduction structure of Example 1 of the present invention.

[0022] Figure 3b This is an equivalent medium diagram of the sound-absorbing superstructure in the theoretical modeling of the low-frequency, broadband sound-absorbing and noise-reducing structure of Example 1 of the present invention.

[0023] Figure 4a This is a theoretical calculation diagram of the real part of the normalized density of the sound absorption superstructure of the low-frequency, broadband sound absorption and noise reduction structure of Example 1 of the present invention.

[0024] Figure 4b This is a theoretical calculation diagram of the normalized density imaginary part of the sound absorption superstructure of the low-frequency, broadband sound absorption and noise reduction structure of Example 1 of the present invention.

[0025] Figure 4c This is a theoretical calculation diagram of the real part of the normalized bulk modulus of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0026] Figure 4d This is a theoretical calculation diagram of the imaginary part of the normalized bulk modulus of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0027] Figure 5a This is a theoretical calculation diagram of the real part of the equivalent sound velocity of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0028] Figure 5b This is a theoretical calculation diagram of the imaginary part of the equivalent sound velocity of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0029] Figure 5c This is a theoretical calculation diagram of the real part of the equivalent characteristic impedance of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0030] Figure 5d This is a theoretical calculation diagram of the imaginary part of the equivalent characteristic impedance of the sound absorbing superstructure of the low-frequency, broadband sound absorbing and noise reduction structure of Example 1 of the present invention.

[0031] Figure 6 Theoretical calculation diagram of the sound absorption coefficient comparison between the porous material and the sound absorption superstructure of the same thickness of the low-frequency broadband sound absorption and noise reduction structure of Example 1 of the present invention

[0032] Figure 7 This is a schematic diagram of the structure of a range hood according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0034] Example 1

[0035] like Figure 1-Figure 2 As shown, this embodiment provides a low-frequency broadband sound absorption and noise reduction structure, which includes: a porous material base plate 10 and a rigid plug plate 20, the porous material base plate 10 has a target surface, and a plurality of rigid plug plates 20 are arranged along a first direction ( Figure 1 The plurality of rigid plug plates 20 are arranged on the target surface and embedded in the porous base material plate 10, and the lengths of the plurality of rigid plug plates 20 gradually increase along a first direction, which is perpendicular to the radiation direction of the structure-borne noise.

[0036] In this embodiment, the low-frequency broadband sound absorption and noise reduction structure is applied to the flow of the range hood, and five rigid plug plates 20-1, 20-2, 20-3, 20-4 and 20-5 with the same thickness but different lengths are embedded in the target surface of the porous material base plate 10, and the lengths of several rigid plug plates 20 are along Figure 1 Since the rigid plug plate 20 is embedded in the porous material substrate 10 along the plane direction, as long as the target surface of the porous material substrate 10 is large enough, a set number of rigid plug plates 20 of different lengths are distributed on the target surface to achieve low-frequency noise reduction in a compact space and thin thickness.

[0037] It should be noted that the lower surface of the rigid plug plate 20 is completely embedded in the porous material substrate 10, and the upper surface thereof is kept flush with the target surface of the porous material substrate 10 to ensure the stability of the flow field.

[0038] In one embodiment, the lengths of the plurality of rigid plug boards 20 are arranged in an arithmetic progression and at equal intervals along the first direction.

[0039] In one embodiment, the length of the rigid board 20 is calculated by the following formula:

[0040] b i =di(db N ) / N(i=1,2,…,N)

[0041] Among them, b i represents the length of the i-th rigid plug, N represents the number of rigid plugs, and d represents the length of the porous material substrate along the second direction ( Figure 2 The minimum length of the arrow direction shown, b N It represents the shortest length of the rigid board along the first direction, and the second direction is parallel to the radiation direction of the structure-borne noise.

[0042] In one embodiment, the ratio of the total area occupied by the plurality of rigid plugboards 20 in the target surface to the area of ​​the target surface is in the range of 8%-30%.

[0043] In one embodiment, if Figure 2 As shown, the maximum length of the rigid plugboard 20 on the target surface is smaller than the length of the target surface.

[0044] In one embodiment, the length of the rigid plug plate 20 along the direction perpendicular to the first direction is less than the minimum length of the porous material base plate 10 along the direction perpendicular to the first direction.

[0045] In this embodiment, Figure 2 As shown, the lengths b1-bn of the plurality of rigid plugboards 20 are arranged in an arithmetic progression gradient and are distributed at equal intervals along the first direction. In addition, the maximum length bn of the rigid plugboard 20 on the target surface is less than the length L of the target surface. The ratio of the total area (S1+S2+S3...+Sn) occupied by the plurality of rigid plugboards 20 in the target surface to the area S of the target surface is in the range of 8%-30%, and the length t of the rigid plugboard 20 along the direction perpendicular to the first direction is less than the minimum length d of the porous material substrate 10 along the direction perpendicular to the first direction.

[0046] In one embodiment, the porous material base plate 10 is wedge-shaped and is made of melamine foam.

[0047] In one embodiment, the porosity of the porous material substrate 10 is 0.93, and the flow resistance is 11000-14000 Pa·s / m 2 , the tortuosity is 1.07, the thermal characteristic length is 273μm, and the viscous characteristic length is 672μm.

[0048] In this embodiment, a polyurethane porous material with an elastic frame in a black porous sound-absorbing material can be used as the basic material of the porous material base plate 10, without the need for side plates and top plates. The structural design is simple, and low-frequency broadband noise reduction can be achieved by only adjusting the number, size and distribution position of the rigid plug-in plate 20.

[0049] In the process of noise reduction in the flow channel of the range hood, there is both structural radiation noise (noise radiated from the inlet of the centrifugal fan) and flow noise (noise generated by the flow of fluid in the box), and the two contribute differently to the total noise. In order to improve the noise reduction effect of the low-frequency broadband sound absorption and noise reduction structure on the noise generated by the flow of fluid in the flow channel of the range hood, by adjusting the upper and lower thicknesses of the black sound-absorbing cotton to be unequal, a preset inclination is formed, and the porous material base plate 10 is set to a wedge shape. By optimizing different wedge angles (for example, 75 degrees to 87 degrees), the airflow in the flow field of the structure space to be reduced (for example, the flow channel of the range hood) is guided to enter, so that the formation of vortices in the flow field is minimized when the airflow passes through the structure space to be reduced, thereby strengthening the reduction of flow noise.

[0050] In one embodiment, the rigid plug board 20 is made of resin material, and the density of the resin material is 1230 kg / m 3 .

[0051] In this embodiment, in order to facilitate processing and installation, the material of the rigid plug board 20 with a gradient length distribution is 3D printing material (resin). The resin density is 1230kg / m 3 , the speed of sound is 2700m / s, and the tensile modulus is 2600Mpa.

[0052] The following is an explanation of the noise reduction effect through theoretical modeling method:

[0053] like Figure 3a As shown, 6 layers of rigid spacers are embedded in the porous matrix, that is, N = 6, height H = 30 cm, width d = 3 cm, thickness of the embedded rigid body t = 2 mm; the length b of the top rigid body N =b6=1.8cm; ΔH=H / N=5mm. Starting from the bottom layer, the length of each layer embedded in the rigid body satisfies the following formula, from which we can obtain: b6=1.8cm; b5=2.0cm; b4=2.2cm; b3=2.4cm; b2=2.6cm; b1=2.8cm.

[0054] b i =di(db N ) / N(i=1,2,…,N)

[0055] like Figure 3b As shown, the gradient structure adopts the equivalent medium theory, and its equivalent process is as follows Figure 3b As shown, the equivalent density of the composite structure is obtained: ρ is the density of the porous material equivalent to the JCA model, φ i represents the ratio of the length of the embedding to the unit cell lattice constant, that is, φ i =b i ' / d,b i '=(b i +b i-1 ) / 2, the following expression is obtained:

[0056] φ1=2.9 / 3; φ2=2.7 / 3; φ3=2.5 / 3; φ4=2.3 / 3; φ5=2.1 / 3; φ6=1.9 / 3,

[0057] The equivalent bulk modulus of the sound absorbing superstructure is expressed as:

[0058]

[0059] Where K represents the equivalent bulk modulus of the porous material, φ i Consistent with the above definition, η2=(1-t / ΔH)=0.6, which represents the volume ratio of the porous medium along the y direction, k represents the wave number of the porous medium, and k=ω / c=2πf / c, c represents the equivalent sound velocity of the porous medium, and It is obtained that ρ represents the equivalent density of the porous medium, and K represents the equivalent modulus of the porous medium.

[0060] b' i =(b i +b i-1 ) / 2, b'1 = 2.9 cm, b'2 = 2.7 cm, b'3 = 2.5 cm, b'4 = 2.3 cm, b'5 = 2.1 cm, b'6 = 1.9 cm, d = 3 cm,

[0061] like Figures 4a-4d As shown, it is a theoretical calculation diagram of the real and imaginary parts of the equivalent density and equivalent bulk modulus of the sound absorbing superstructure calculated according to the above formula.

[0062] The equivalent sound velocity of the sound-absorbing superstructure is expressed as:

[0063]

[0064] In the formula, represents the equivalent sound velocity of porous materials, and the definitions of other variables remain the same as above.

[0065] The normalized equivalent characteristic impedance of each layer of the sound-absorbing superstructure is expressed as:

[0066]

[0067] The equivalent characteristic impedance of the sound-absorbing superstructure composed of an embedded plug-in plate and a porous matrix is ​​expressed as:

[0068]

[0069] The sound absorption coefficient is expressed as:

[0070]

[0071] z0=ρ0c0;

[0072] α=1-|R| 2

[0073] like Figure 5a-5d As shown, it is a theoretical calculation diagram of the equivalent sound velocity, the real part and the imaginary part of the equivalent characteristic impedance of the sound absorbing superstructure calculated according to the above formula.

[0074] Figure 5aIt can be determined that after the rigid plug is embedded in the porous matrix, the equivalent sound velocity of each layer of the structure is lower than that of the pure porous material, and the larger the volume ratio of the embedded rigid plug, the slower the equivalent sound velocity. When the sound wave passes through a structure of the same thickness, the smaller the equivalent sound velocity, the longer the propagation time of the sound wave in the structure. For the porous matrix, the sound energy loss per unit time is the same. The longer the equivalent propagation time, the greater the sound loss, that is, the better the noise reduction effect, which is the basic principle of slow wave to achieve enhanced noise reduction effect.

[0075] At the same time, it can be found from the sound absorption coefficient that after the structural equivalent characteristic impedance is normalized with the air characteristic impedance, when the real part approaches 1 and the imaginary part approaches 0, the sound absorption coefficient shifts in the direction of enhancement.

[0076] Figure 5c It can be determined that within the frequency band above 500 Hz, the real part of the normalized acoustic impedance approaches 1 and the imaginary part approaches 0, which can significantly improve the mid- and high-frequency broadband sound absorption.

[0077] Based on the above design method, the JCA model and slow wave equivalent model were used to calculate the sound absorption coefficients of the pure porous sound absorbing material and the composite sound absorbing superstructure with porous embedded inserts of the same thickness (3 cm). Figure 6 As shown, by embedding a rigid insert in the porous material, the sound absorption performance of the porous material at a thinner thickness can be significantly improved.

[0078] Figure 6 Starting from 367Hz, the sound absorption coefficient of the sound-absorbing superstructure is higher than that of the pure porous material. In the research frequency band of 367Hz-4000Hz, the average sound absorption coefficient of the sound-absorbing superstructure is 0.7423, while the sound absorption coefficient of the pure porous material is only 0.3486. The average sound absorption coefficient is increased by 0.3937, achieving a significant noise reduction effect in the medium and high frequency bands. At the same time, obvious sound absorption peaks appear at 1436Hz and 2344Hz.

[0079] In the present embodiment, a low-frequency, broadband sound absorption and noise reduction structure is provided. By adjusting the number, size and distribution position of the rigid plug plates on the porous material base plate, the structural radiation noise and mechanical noise in the flow field environment and the non-flow field environment are reduced, the noise reduction effect in different main noise distribution directions is enhanced, and low-frequency noise reduction is achieved in a compact space and with a thin thickness.

[0080] Example 2

[0081] This embodiment provides a range hood, such as Figure 7 As shown, it includes a low-frequency broadband sound absorption and noise reduction structure as in Example 1, the range hood includes an air duct 30 and a centrifugal fan 40 located inside the air duct 30, the low-frequency broadband sound absorption and noise reduction structure is arranged on the inner surface of the air duct 30, and the target surface of the low-frequency broadband sound absorption and noise reduction structure faces the centrifugal fan 40.

[0082] The noise reduction space of the range hood is limited. There is structural radiation noise (noise radiated from the inlet of the centrifugal fan 40, Figure 7 There is also flow noise (the noise generated by the flow of fluid in the range hood housing, Figure 7 The vertical arrow in the middle indicates the direction of the noise, and the contribution of the two to the total noise is different. Under the thickness constraint of traditional porous materials, the sound absorption coefficient of the medium and high frequencies deteriorates, and the low-frequency noise reduction ability is limited. This embodiment uses a low-frequency broadband sound absorption and noise reduction structure formed by embedding a rigid plug plate in a thinner porous material matrix to solve the problem of poor sound absorption performance of the noise reduction structure space in the medium and high frequency bands under thickness constraints, and strengthens the noise reduction effect in the medium and high frequency bands above 500Hz while the noise reduction structure space remains unchanged.

[0083] In the present embodiment, a range hood is provided, and a low-frequency, broadband sound absorption and noise reduction structure of the range hood is utilized to achieve low-frequency noise reduction in a compact space and with a relatively thin thickness in an air inlet passage of the range hood.

[0084] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A low-frequency, broadband sound absorption and noise reduction structure, characterized in that: include: A porous material substrate and a rigid plug plate, wherein the porous material substrate has a target surface, a plurality of the rigid plug plates are arranged on the target surface along a first direction and embedded in the porous material substrate, and the lengths of the plurality of the rigid plug plates gradually increase along the first direction, and the first direction is perpendicular to the structural noise radiation direction.

2. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The lengths of the plurality of rigid plug plates are arranged in an arithmetic progression and at equal intervals along the first direction.

3. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The length of the rigid plugboard is calculated by the following formula: b i =d-i(d-b N ) / N(i=1,2,…,N) Among them, b i represents the length of the i-th rigid plug plate, N represents the number of the rigid plug plates, d represents the minimum length of the porous material substrate along the second direction, b N represents the shortest length of the rigid board along the first direction, and the second direction is parallel to the structural noise radiation direction.

4. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The ratio of the total area occupied by the plurality of rigid plug boards in the target surface to the area of ​​the target surface is in the range of 8%-30%.

5. The low-frequency, broadband sound absorption and noise reduction structure according to claim 3, characterized in that: The maximum length of the rigid plugboard on the target surface is smaller than the length of the target surface.

6. The low-frequency, broadband sound absorption and noise reduction structure according to claim 3, characterized in that: The length of the rigid plug plate along the direction perpendicular to the first direction is smaller than the minimum length of the porous material base plate along the direction perpendicular to the first direction.

7. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The porous material substrate is wedge-shaped and is made of melamine foam.

8. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The porosity of the porous material substrate is 0.93, and the flow resistance is 11000-14000 Pa·s / m 2 , the tortuosity is 1.07, The thermal characteristic length is 273 μm, The viscous characteristic length is 672 μm.

9. The low-frequency, broadband sound absorption and noise reduction structure according to claim 1, characterized in that: The rigid plug board is made of resin material, and the density of the resin material is 1230 kg / m 3 .

10. A range hood, characterized in that: It comprises a low-frequency, broadband sound absorption and noise reduction structure as described in any one of claims 1 to 9, the range hood comprises an air duct and a centrifugal fan located inside the air duct, the low-frequency, broadband sound absorption and noise reduction structure is arranged on the inner surface of the air duct, and the target surface of the low-frequency, broadband sound absorption and noise reduction structure faces the centrifugal fan.

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