Noise reduction device and range hood containing it

Abstract

This invention discloses a noise reduction device and a range hood including the same, used for noise reduction in a fan system. The device includes: a noise concentrator disposed within the fan system, which includes a volute. The noise concentrator is correspondingly disposed with the volute, forming an air intake zone between them. The noise concentrator is positioned along the height of the fan system and has a reflective surface facing the air intake zone, concentrating noise from the volute through the reflective surface; and a noise reduction unit disposed within the air intake zone and away from the air inlet of the fan system, used to absorb noise from the reflective surface. This device concentrates noise from different directions, allowing the noise reduction unit to be positioned at a specific location, making efficient use of the space within the air intake zone to improve noise reduction while ensuring the fan system's operating efficiency is not affected.

Description

Technical Field

[0001] This invention relates to the field of fan system technology, and in particular to a noise reduction device and a range hood containing the same. Background Technology

[0002] The noise energy distribution inside a range hood is uneven, and the internal sound field energy is relatively dispersed, making it impossible to concentrate the sound absorption in one place. This often requires wrapping a large area of ​​sound-absorbing cotton. This results in a large sound-absorbing area, higher costs, and some sound-absorbing cotton positions can affect the outflow space, creating significant resistance to the fluid in the range hood and increasing fluid noise. In this case, noise reduction becomes counterproductive.

[0003] Furthermore, the sound absorption coefficient curve of porous materials such as sound-absorbing cotton shows that the low-frequency sound absorption coefficient improves with increasing thickness of the sound-absorbing cotton. However, due to the limited internal space of range hoods, it is impossible to install thicker sound-absorbing cotton, especially in noisy fan systems. Space constraints prevent the installation of thicker sound-absorbing cotton in the air intake area, resulting in high noise levels and affecting the user experience. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of existing technologies that are difficult to reduce noise due to space limitations, and to provide a noise reduction device and a range hood containing the same.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

[0006] A noise reduction device for use in a fan system, the noise reduction device comprising:

[0007] A noise concentrator is provided within the fan system, which includes a volute. The noise concentrator is correspondingly disposed with the volute, and an air intake area is formed between the noise concentrator and the volute. The noise concentrator is disposed along the height direction of the fan system, and a reflective surface is provided on the noise concentrator facing the air intake area. The noise concentrator concentrates the noise from the volute through the reflective surface.

[0008] A noise reduction unit is disposed in the air inlet area and away from the air inlet of the fan system, and the noise reduction unit is used to absorb noise from the reflective surface.

[0009] In this solution, a noise concentrator is installed to collect noise generated by the volute and noise from different directions within the fan system. This prevents noise from being dispersed and noise reduction structures from being placed in different directions and locations. The concentrated noise is reflected to the noise reduction unit through a reflective surface, allowing the noise reduction unit to be placed in a specific location, which is the side wall of the fan system away from the air inlet. This allows the noise reduction unit to make reasonable use of the space within the air inlet area and avoids the resistance to airflow caused by the dispersed placement of noise reduction units. The noise reduction unit placed on the side wall of the fan system away from the air inlet can be thickened accordingly to improve the noise reduction effect while ensuring that the working efficiency of the fan system is not affected.

[0010] Preferably, the noise concentrator further includes a first driving unit disposed within the noise concentrator, one end of the first driving unit being connected to the reflective surface, and the first driving unit being used to drive the reflective surface closer to or further away from the air inlet area.

[0011] In this scheme, the above settings are used to achieve the movement of the reflective surface, thereby effectively concentrating and reflecting the noise.

[0012] Preferably, along the height direction of the fan system, the end of the reflective surface away from the noise reduction part is hinged to the housing of the noise concentrator, and the end of the reflective surface near the noise reduction part is close to or away from the air inlet area through the first drive part.

[0013] In this solution, the above-mentioned arrangement is used to make an angle between the reflective surface and the casing when the reflective surface moves, thereby concentrating the noise and reflecting it to the side wall of the fan system away from the air inlet, which is the location of the noise reduction unit. This achieves a specific location for the noise reduction unit, eliminating the need for dispersed noise reduction units, saving space, and reducing resistance to airflow in the air inlet area.

[0014] Preferably, the noise reduction unit includes a noise reduction surface, which is disposed corresponding to the reflective surface. The noise reduction unit also includes a second driving unit, which is used to drive the noise reduction surface to move closer to or away from the reflective surface.

[0015] In this scheme, the above settings are used to achieve the movement of the noise reduction surface. When the noise reduction surface moves, it maintains a correspondence with the moving reflective surface to prevent the noise that is concentrated and reflected from not being received by the noise reduction surface.

[0016] Preferably, along the height direction of the fan system, the end of the noise-reducing surface away from the noise concentrator is hinged to the outer shell of the noise-reducing part, and the end of the noise-reducing surface near the noise concentrator is close to or away from the reflective surface through the second driving part.

[0017] In this scheme, the above settings are used to correspond to the moving reflective surface when the noise reduction surface moves.

[0018] Preferably, when the impeller speed of the fan system is 500-800 r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 0-2°.

[0019] When the impeller speed of the fan system is 800-1200r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 2-5°.

[0020] When the impeller speed of the fan system is 1200-1600 r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 5-10°.

[0021] In this solution, the above settings are used to adjust the angle of the reflecting surface according to the different noise intensities generated at different impeller speeds, thereby effectively concentrating and reflecting noise, while eliminating noise through the noise reduction surface.

[0022] Preferably, when the angle between the reflective surface and the side wall of the housing away from the air inlet area is 0-2°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 90-92°.

[0023] When the angle between the reflective surface and the side wall of the housing away from the air inlet area is 2-5°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 92-95°.

[0024] When the angle between the reflective surface and the side wall of the housing away from the air inlet is 5-10°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 95-100°.

[0025] In this solution, the above settings are used to adjust the angle of the noise reduction surface according to the angle change of the reflective surface at different impeller speeds, thereby effectively receiving and eliminating noise from the reflective surface.

[0026] Preferably, the noise-reducing surface is uniformly covered with sound-absorbing cotton.

[0027] In this solution, the above settings are used to effectively absorb and eliminate noise.

[0028] Preferably, the thickness of the sound-absorbing cotton is 30-230mm.

[0029] In this solution, by placing the noise reduction unit on the side wall of the fan system away from the air inlet, there is no need to worry that the noise reduction unit will create resistance to the airflow. At this time, the appropriate thickness of the sound-absorbing cotton can be selected according to the noise intensity, and there is no need to worry that the sound-absorbing cotton is too thick and will occupy the airflow space in the air inlet area.

[0030] A range hood, the range hood including the noise reduction device as described above.

[0031] In this solution, the range hood includes the aforementioned noise reduction device, which reduces noise reduction costs while ensuring that the working efficiency of the fan system is not affected, effectively concentrates and eliminates noise, achieves better noise reduction effect, and does not occupy the remaining space in the fan system.

[0032] The positive and progressive effects of this invention are as follows: By setting up a noise concentrator, this invention can collect the noise generated by the volute and the noise from different directions within the fan system, preventing the noise from being dispersed and the noise reduction structures from being arranged in different directions and positions. The concentrated noise is reflected to the noise reduction unit through the reflective surface, allowing the noise reduction unit to be set in a specific position, which is the side wall of the fan system away from the air inlet. This allows the noise reduction unit to make reasonable use of the space within the air inlet area, avoiding the resistance to airflow in the air inlet area caused by the dispersed placement of noise reduction units. The noise reduction unit set on the side wall of the fan system away from the air inlet can be thickened accordingly to improve the noise reduction effect while ensuring that the working efficiency of the fan system is not affected. Attached Figure Description

[0033] Figure 1 This is a perspective view of a range hood according to a preferred embodiment of the present invention.

[0034] Figure 2 This is a diagram showing the positional relationship between the noise concentrator and the noise reduction unit in a preferred embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a preferred embodiment of the reflective surface structure of the present invention.

[0036] Figure 4 This is a schematic diagram of a noise reduction surface structure according to a preferred embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of the second driving unit structure according to a preferred embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of the first driving unit structure according to a preferred embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram showing the angle between the reflecting surface and the noise-reducing surface when the impeller speed is 500-800 r, according to a preferred embodiment of the present invention.

[0040] Figure 8 This is a schematic diagram showing the angle between the reflecting surface and the noise-reducing surface when the impeller speed is 800-1200 r, according to a preferred embodiment of the present invention.

[0041] Figure 9This is a schematic diagram showing the angle between the reflecting surface and the noise-reducing surface when the impeller speed is 1200-1600 r, according to a preferred embodiment of the present invention.

[0042] Explanation of reference numerals in the attached figures:

[0043] Fan system 100

[0044] 101

[0045] Air intake area 102

[0046] Air inlet 103

[0047] Noise Concentrator 1

[0048] Reflective surface 11

[0049] First drive unit 12

[0050] Worm Gear 121

[0051] Motor 122

[0052] Gear 123

[0053] Casing 13

[0054] Noise Reduction Unit 2

[0055] Noise Reduction Surface 21

[0056] Second drive unit 22

[0057] Drive motor 221

[0058] Joystick 222

[0059] Casing 23 Detailed Implementation

[0060] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0061] This embodiment provides a noise reduction device, the specific structure of which is as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the noise reduction device is used for noise reduction in the fan system 100. The noise reduction device includes:

[0062] Noise concentrator 1 is installed in the fan system 100, which includes a volute 101. The noise concentrator 1 is correspondingly installed with the volute 101, and an air inlet area 102 is formed between the noise concentrator 1 and the volute 101. The noise concentrator 1 is installed along the height direction of the fan system 100, and a reflective surface 11 is provided on the noise concentrator 1 facing the air inlet area 102. The noise concentrator 1 concentrates the noise from the volute 101 through the reflective surface 11.

[0063] The noise reduction unit 2 is disposed in the air inlet 103 of the air inlet area 102 and away from the fan system 100. The noise reduction unit 2 is used to absorb noise from the reflective surface 11.

[0064] Specifically, along the height direction of the fan system 100, the air inlet 103 is located below the volute 101 and communicates with the air inlet area 102. The noise concentrator 1 is disposed within the fan system 100 and located on the side wall of the fan system 100 away from the volute 101. The noise concentrator 1 extends along the height direction of the fan system 100, corresponding to the volute 101, and the area between the noise concentrator 1 and the volute 101 is the air inlet area 102. The noise concentrator 1 is provided with a reflective surface 11 corresponding to the air inlet area 102. The reflective surface 11 has a flat surface and is made of a material used in the prior art for reflecting noise, such as stainless steel or other metal materials used for reflecting noise. By setting the noise concentrator 1, the noise generated by the volute 101 and noise from different directions within the fan system 100 are collected and reflected along the reflective surface 11, preventing noise diffusion in unexpected directions.

[0065] In addition, this embodiment also includes a noise reduction unit 2, which is located above the noise concentrator 1 along the height direction of the fan system 100, and is connected to the side wall of the fan system 100 away from the air inlet 103. The noise concentrated by the noise concentrator 1 is reflected to the noise reduction unit 2 through the reflective surface 11, so that the originally dispersed noise is concentrated and propagates along the reflection direction, and is finally absorbed and reduced by the noise reduction unit 2. Accordingly, the noise propagation along the reflection direction allows the noise reduction unit 2 to be set at a specific position, which is the side wall of the fan system 100 away from the air inlet 103. This allows the noise reduction unit 2 to make reasonable use of the space in the air inlet area 102, without the need to arrange noise reduction structures from different directions and positions, and avoids the resistance to airflow in the air inlet area 102 caused by the dispersed placement of the noise reduction unit 2. The noise reduction unit 2 set on the side wall of the fan system 100 away from the air inlet 103 can be thickened accordingly to improve the noise reduction effect while ensuring that the working efficiency of the fan system 100 is not affected.

[0066] like Figure 6As shown, in this embodiment, the noise concentrator 1 further includes a first driving unit 12, which is disposed inside the noise concentrator 1. One end of the first driving unit 12 is connected to the reflective surface 11, and the first driving unit 12 is used to drive the reflective surface 11 to move closer to or away from the air inlet area 102.

[0067] Specifically, the first drive unit 12 includes a worm gear 121, a motor 122, and a gear 123. The noise concentrator 1 also includes a housing 13. The reflective surface 11 is the surface of the housing 13 facing the air inlet area 102, and the reflective surface 11 can move relative to the housing 13. The first drive unit 12 is disposed inside the housing 13. The worm gear 121 extends along the thickness direction of the housing 13. One end of the worm gear 121 abuts against the surface of the reflective surface 11 away from the air inlet area 102, and the other end of the worm gear 121 is fitted with a gear 123. The gear 123 is used to mesh with the output shaft of the motor 122 so that when the motor 122 is turned on, it drives the reflective surface 11 abutting against the worm gear 121 to move closer to or away from the air inlet area 102. The first drive unit 12 can be electrically connected to the control board of the fan system 100 to drive the reflective surface 11 to move in real time. This is prior art and will not be described in detail here.

[0068] Furthermore, in this embodiment, along the height direction of the fan system 100, the end of the reflective surface 11 away from the noise reduction part 2 is hinged to the housing 13 of the noise concentrator 1, and the end of the reflective surface 11 near the noise reduction part 2 is close to or away from the air inlet area 102 through the first drive part 12.

[0069] Specifically, the noise concentrator 1 is positioned along the height of the fan system 100, and the reflective surface 11 also extends along the height of the fan system 100. The noise reduction part 2 is located above the noise concentrator 1. The end of the reflective surface 11 near the noise reduction part 2 is movably connected to the housing 13. That is, the size of the end of the reflective surface 11 near the noise reduction part 2 is smaller than the size of the housing 13, so that it can be embedded in the housing 13 when the reflective surface 11 moves. The end of the reflective surface 11 away from the noise reduction part 2 is hinged to the housing 13 via a pivot, allowing the portion of the reflective surface 11 near the middle area of ​​the volute 101 to move accordingly, thus specifically reflecting noise from the volute 101. This achieves an angle between the reflective surface 11 and the housing 13 when the reflective surface 11 moves, thereby concentrating and reflecting the noise to the side wall of the fan system 100 away from the air inlet 103, i.e., the location of the noise reduction part 2. This achieves a specific location for the noise reduction part 2, eliminating the need for dispersed placement of the noise reduction part 2, saving space, and reducing resistance to airflow within the air inlet area 102.

[0070] To prevent the reflective surface 11 from failing to return to its original position after being moved by the first drive unit 12, this embodiment also includes an elastic element (not shown in the figure). The elastic element is a spring, as is common in the prior art. One end of the elastic element is connected to the surface of the reflective surface 11 facing away from the air inlet area 102, and the other end is connected to the housing 13. By providing the elastic element, the reflective surface 11 can return to its original position by providing elastic force after movement. Preferably, the stroke of the elastic element is 2-20 mm.

[0071] like Figure 4 and Figure 5 As shown, in this embodiment, the noise reduction unit 2 includes a noise reduction surface 21, which is correspondingly disposed with the reflective surface 11. The noise reduction unit 2 also includes a second driving unit 22, which is used to drive the noise reduction surface 21 to move closer to or away from the reflective surface 11.

[0072] Specifically, the noise reduction part 2 is a parallelogram in cross-section. The noise reduction surface 21 is located on the side of the noise reduction part 2 facing the noise concentrator 1, while a second drive part 22 is located on the side of the noise reduction part 2 away from the noise concentrator 1. The second drive part 22 includes a drive motor 221 and a rocker arm 222. The drive motor 221 and the rocker arm 222 are located on the side of the noise reduction part 2 away from the noise concentrator 1. The noise reduction part 2 also includes a housing 23. The housing 23 includes two parallel side walls located between the noise reduction surface 21 and the side of the noise reduction part 2 away from the noise concentrator 1. The parallel side walls are respectively hinged to the noise reduction surface 21 and the side of the noise reduction part 2 away from the noise concentrator 1 via a pivot. When the drive motor 221 is turned on, it drives the rocker arm 222 to swing, thereby causing the noise reduction surface 21 to move closer to or further away from the reflective surface 11. It is understandable that the noise reduction surface 21 corresponds to the moving reflective surface 11 when it is moving, so as to prevent the noise reflected after concentration from not being received by the noise reduction surface 21.

[0073] In this embodiment, along the height direction of the fan system 100, the end of the noise reduction surface 21 away from the noise concentrator 1 is hinged to the outer shell 23 of the noise reduction part 2, and the end of the noise reduction surface 21 near the noise concentrator 1 is close to or away from the reflective surface 11 through the second drive part 22.

[0074] Specifically, the outer casing 23 includes two parallel side walls. One side wall is connected to the side wall of the fan system 100 away from the air inlet 103, and the other side wall is located near the noise concentrator 1. Both side walls are hinged to the noise reduction surface 21. When the second drive unit 22 is activated, since the parallel side wall is connected to the side wall of the fan system 100 away from the air inlet 103, the other side wall moves under the action of the rocker arm 222. Correspondingly, the noise reduction surface 21 rotates about the end of the noise reduction surface 21 away from the noise concentrator 1 under the action of the other side wall, so as to move closer to or away from the reflector surface 11. The second drive unit 22 can be electrically connected to the control board of the fan system 100 to drive the noise reduction surface 21 to move in real time. This is prior art and will not be described in detail here.

[0075] like Figure 7 , Figure 8 and Figure 9 As shown, in this embodiment, when the impeller speed of the fan system 100 is 500-800r, the angle between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is 0-2°.

[0076] When the impeller speed of the fan system 100 is 800-1200r, the angle between the reflective surface 11 and the side wall of the casing 13 away from the air inlet area 102 is 2-5°.

[0077] When the impeller speed of the fan system 100 is 1200-1600 r, the angle between the reflector 11 and the side wall of the casing 13 away from the air inlet area 102 is 5-10°.

[0078] Specifically, when the impeller speed of the fan system 100 is 500-800 r / s, the fan system 100 is in a low-speed mode, the airflow velocity is slow, and the noise generated by the impeller is low. The angle α between the reflective surface 11 and the side wall of the casing 13 away from the air inlet area 102 is preferably 2°, so as to concentrate and specifically reflect the noise to the noise reduction part 2. When the impeller speed of the fan system 100 is 800-1200 r / s, the fan system 100 is in a high-speed mode, and the angle α between the reflective surface 11 and the side wall of the casing 13 away from the air inlet area 102 is preferably 5°, so as to concentrate and specifically reflect the noise to the noise reduction part 2. When the impeller speed of the fan system 100 is 1200-1600 r, the fan system 100 is in the instantaneous suction mode, the airflow velocity is fast, and the noise generated by the impeller is large. The angle α between the reflective surface 11 and the side wall of the casing 13 away from the air inlet area 102 is preferably 10°. By setting the first drive unit 12, the angle of the reflective surface 11 can be adjusted according to the different noise intensities generated at different impeller speeds, thereby effectively concentrating and reflecting the noise, while the noise reduction surface 21 eliminates the noise.

[0079] Furthermore, when the angle between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is 0-2°, the angle between the noise reduction surface 21 and the side wall of the fan system 100 away from the air inlet 103 is 90-92°.

[0080] When the angle between the reflective surface 11 and the side wall of the housing 13 away from the air inlet 102 is 2-5°, the angle between the noise reduction surface 21 and the side wall of the fan system 100 away from the air inlet 103 is 92-95°.

[0081] When the angle between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is 5-10°, the angle between the noise reduction surface 21 and the side wall of the fan system 100 away from the air inlet 103 is 95-100°.

[0082] Specifically, when the angle α between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is preferably 2°, the angle β between the noise-reducing surface 21 and the side wall of the fan system 100 away from the air inlet 103 is preferably 92°. When the angle α between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is preferably 5°, the angle β between the noise-reducing surface 21 and the side wall of the fan system 100 away from the air inlet 103 is preferably 95°. When the angle α between the reflective surface 11 and the side wall of the housing 13 away from the air inlet area 102 is preferably 10°, the angle β between the noise-reducing surface 21 and the side wall of the fan system 100 away from the air inlet 103 is preferably 100°. This allows the angle of the noise-reducing surface 21 to be adjusted according to the angle change of the reflective surface 11 at different impeller speeds, thereby effectively receiving and eliminating noise from the reflective surface 11.

[0083] In this embodiment, the noise-reducing surface 21 is uniformly covered with sound-absorbing cotton. Sound-absorbing cotton is a structure used in the prior art for absorbing and eliminating noise. The uniform distribution of sound-absorbing cotton on the noise-reducing surface 21 allows for the concentrated reflection and targeted absorption of noise within the fan system 100 through the movable noise-reducing surface 21 and the movable reflective surface 11. This eliminates the need for the sound-absorbing cotton to be dispersed throughout the fan system 100, avoiding airflow resistance caused by dispersed placement, which would affect the working efficiency of the fan system 100. It also avoids the high cost and low noise reduction effect associated with dispersed placement, thus effectively absorbing and eliminating noise.

[0084] In this embodiment, the thickness of the sound-absorbing cotton is 30-230mm. Specifically, according to the sound absorption coefficient test in the prior art, the sound-absorbing cotton has a better sound absorption effect for low-frequency noise as the thickness increases. Through tests on sound-absorbing cotton with thicknesses of 30mm, 80mm, 130mm, 180mm, and 230mm, it was found that, while saving costs, the sound-absorbing cotton with a thickness of 130mm can meet the noise reduction requirements for low-frequency noise. The difference in sound absorption effect for low-frequency noise between sound-absorbing cotton with a thickness greater than 130mm and that with a thickness of 130mm is small, but the cost is higher. Therefore, the thickness of the sound-absorbing cotton is preferably 130mm.

[0085] In addition, it is understood that by setting the noise reduction part 2 on the side wall of the fan system 100 away from the air inlet 103, there is no need to worry that the noise reduction part 2 will cause resistance to the airflow. At this time, the appropriate thickness of the sound-absorbing cotton can be selected according to the noise intensity, and there is no need to worry that the sound-absorbing cotton is too thick and occupies the flow space of the airflow in the air inlet area 102.

[0086] This embodiment also provides a range hood that includes the above-mentioned noise reduction device, so as to reduce noise reduction costs, effectively concentrate and eliminate noise, and achieve better noise reduction effect without occupying the remaining space in the fan system 100, while ensuring that the working efficiency of the fan system 100 is not affected.

[0087] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A noise reduction device, said noise reduction device being used for noise reduction in a fan system, characterized in that, The noise reduction device includes: A noise concentrator is provided within the fan system, which includes a volute. The noise concentrator is correspondingly disposed with the volute, and an air intake area is formed between the noise concentrator and the volute. The noise concentrator is disposed along the height direction of the fan system, and a reflective surface is provided on the noise concentrator facing the air intake area. The noise concentrator concentrates the noise from the volute through the reflective surface. The noise reduction unit is disposed in the air inlet area and away from the air inlet of the fan system. The noise reduction unit is used to absorb noise from the reflective surface. The noise reduction unit includes a noise reduction surface, which is disposed corresponding to the reflective surface. The noise reduction unit also includes a second driving unit, which is used to drive the noise reduction surface to move closer to or away from the reflective surface.

2. The noise reduction device as described in claim 1, characterized in that, The noise concentrator further includes a first driving unit, which is disposed inside the noise concentrator. One end of the first driving unit is connected to the reflective surface, and the first driving unit is used to drive the reflective surface closer to or away from the air inlet area.

3. The noise reduction device as described in claim 2, characterized in that, Along the height direction of the fan system, the end of the reflective surface away from the noise reduction part is hinged to the housing of the noise concentrator, and the end of the reflective surface near the noise reduction part is close to or away from the air inlet area through the first drive part.

4. The noise reduction device as described in claim 1, characterized in that, Along the height direction of the fan system, the end of the noise reduction surface away from the noise concentrator is hinged to the outer shell of the noise reduction part, and the end of the noise reduction surface near the noise concentrator is close to or away from the reflective surface through the second drive part.

5. The noise reduction device as described in claim 3, characterized in that, When the impeller speed of the fan system is 500-800 r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 0-2°. When the impeller speed of the fan system is 800-1200r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 2-5°. When the impeller speed of the fan system is 1200-1600 r, the angle between the reflective surface and the side wall of the casing away from the air inlet area is 5-10°.

6. The noise reduction device as described in claim 5, characterized in that, When the angle between the reflective surface and the side wall of the housing away from the air inlet is 0-2°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 90-92°. When the angle between the reflective surface and the side wall of the housing away from the air inlet area is 2-5°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 92-95°. When the angle between the reflective surface and the side wall of the housing away from the air inlet is 5-10°, the angle between the noise reduction surface and the side wall of the fan system away from the air inlet is 95-100°.

7. The noise reduction device as described in claim 1, characterized in that, The noise-reducing surface is evenly covered with sound-absorbing cotton.

8. The noise reduction device as described in claim 7, characterized in that, The thickness of the sound-absorbing cotton is 30-230mm.

9. A range hood, characterized in that, The range hood includes a noise reduction device as described in any one of claims 1-8.

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