Installation structure of active noise reduction system for range hood and range hood

Abstract

This utility model relates to an installation structure and a range hood for an active noise reduction system of a fume extraction device. The active noise reduction system includes a sound acquisition device disposed in an air duct. The air duct has a first sidewall and a second sidewall opposite to each other in a first direction, and an airflow inlet. The airflow inlet is disposed adjacent to the first sidewall, and at least one sound acquisition device is disposed adjacent to the second sidewall. The sound acquisition device includes a housing and a sound acquisition element. The housing defines a sound propagation channel, which includes a first channel segment and a second channel segment arranged sequentially at an angle. The sound acquisition element is located in the first channel segment, and the housing has a second sound inlet for sound from the air duct to enter the second channel segment. The advantages are: the installation position of the sound acquisition device is reasonably arranged according to the airflow state in the air duct, resulting in good wind noise reduction and thus effectively improving the accuracy of sound acquisition in the active noise reduction system of the fume extraction device.

Description

Technical Field

[0001] This utility model relates to the field of kitchen appliance technology, and in particular to an installation structure for an active noise reduction system of a fume extraction device and a fume extraction hood. Background Technology

[0002] Kitchen appliances such as range hoods and integrated cooktops with fume extraction functions are used to purify the kitchen environment. The noise generated during operation of these appliances has always been a major problem for users. Active noise cancellation, as a new noise reduction technology, is being considered for application in range hoods. Active noise cancellation devices typically include a microphone and a speaker. The microphone collects the noise generated when the range hood is operating, and the collected noise sound waves are transmitted to the controller as electrical signals. The controller analyzes and processes the signals and sends instructions to the speaker to emit sound waves that match the noise sound waves, thus neutralizing the noise and achieving a noise reduction effect. For example, Chinese invention patent application CN202010935185.0 (publication number CN111928310A) discloses such a range hood with active noise cancellation. In this range hood, the microphone is located inside the casing and arranged in an array around the fan, while the speaker assembly is located below the fan. For example, similar disclosures have been made in the application for "Rainbow Hood and Active Noise Reduction Device" with application number CN202221822214.3 and the application for "Low Noise Range Hood" with application number CN202222650354.3.

[0003] The range hoods described in the aforementioned patent applications have certain shortcomings. First, they do not rationally and specifically arrange the microphones within the duct based on the airflow conditions. Instead, they are simply arranged in an array around the fan or on the side walls of the duct. A large number of microphones can cause congestion within the duct and occupy installation space for other components. Second, the impact of airflow conditions on microphone noise is not considered. For example, if microphones are placed in areas with high airflow velocity, the secondary noise (wind noise) generated as airflow passes over them will be greater. Therefore, a large number of microphones can significantly affect the accuracy of sound acquisition by the active noise cancellation device. In particular, existing microphone devices (sound acquisition devices) are basically only treated to prevent oil stains and do not consider the impact of wind noise within the range hood's duct, meaning they lack effective wind noise reduction, severely affecting the accuracy of sound acquisition and reducing the effectiveness of active noise cancellation. Utility Model Content

[0004] The first technical problem to be solved by this utility model is to provide an installation structure for an active noise reduction system of a fume extractor that can reasonably arrange the installation position of the sound acquisition device according to the airflow state in the duct, has a good wind noise reduction effect, and thus effectively improves the accuracy of sound acquisition, in light of the current state of the technology.

[0005] The second technical problem to be solved by this utility model is to provide a range hood that applies the above-mentioned active noise reduction system installation structure, in view of the current state of the prior art.

[0006] The technical solution adopted by this utility model to solve the first technical problem is: an installation structure of an active noise reduction system for a fume extraction device. The active noise reduction system includes a sound acquisition device, which is disposed in the air duct of the fume extraction device. The air duct has a first sidewall and a second sidewall opposite to each other in a first direction, and an airflow inlet for airflow to enter the air duct. The first direction is perpendicular to the extension direction of the air duct. The airflow inlet is disposed adjacent to the first sidewall. At least one sound acquisition device is disposed adjacent to the second sidewall. The sound acquisition device includes a housing and a sound acquisition element. The housing defines a sound propagation channel. The sound propagation channel includes a first channel segment and a second channel segment that are connected sequentially and arranged at an angle. The sound acquisition element is located in the first channel segment. The housing has a second sound inlet for sound in the air duct to enter the second channel segment.

[0007] Using the plane formed by the points at the middle position of the air duct in the first direction and along the extension direction of the air duct as the reference plane, the above-mentioned "airflow inlet is located near the first side wall and at least one sound acquisition device is located near the second side wall" can be understood as: the airflow inlet and at least one sound acquisition device are located on both sides of the reference plane.

[0008] The aforementioned "airflow inlet" refers to an opening in the "box" or "section of air duct" where the sound acquisition device is located. This opening can be directly connected to the outside, or it can be formed in a box (such as a smoke hood) that is connected to the aforementioned "box" or "section of air duct".

[0009] Within the duct, the airflow velocity is higher on the side adjacent to the airflow inlet in the first direction, and lower on the side farther from the airflow inlet. Based on the airflow conditions within the duct, placing the sound acquisition device on the side farther from the airflow inlet can better reduce the adverse effects of secondary noise (wind noise) generated by the direct impact of airflow on the sound acquisition device, thus improving the accuracy of sound acquisition. However, considering that the side adjacent to the airflow inlet is the main path for noise propagation and contains the most comprehensive noise signal information, a special structural design is implemented for the sound acquisition device. Specifically, the sound acquisition element is housed within a casing, and the sound propagation channel within the casing is divided into two segments arranged at an angle. This makes the sound propagation channel of the sound acquisition device a turning path design. This turning path design weakens high-frequency sounds (such as the high-frequency components of wind noise and non-target noise such as high-frequency components generated by the fan system) while having less impact on low-frequency sounds. Therefore, it is well-suited for low-frequency noise propagation within the acquisition device, facilitating accurate acquisition of low-frequency noise by the sound acquisition element. Since the structural design of the aforementioned sound acquisition device can reduce the impact of wind noise on the accuracy of sound acquisition to a certain extent, the sound acquisition device can be positioned closer to the airflow inlet in the first direction to more comprehensively acquire noise signals within the air duct, thereby further improving the accuracy of sound acquisition and enhancing the active noise reduction effect.

[0010] Considering that the airflow along the duct path is related to the relative positions of the fan and the air inlet in the first direction, and that the sound acquisition device is located near the second sidewall, the distance between the line connecting the fan and the air inlet and the second sidewall needs to be carefully designed to avoid the sound acquisition device being too close to the high-velocity area in the middle of the duct and thus being affected by strong wind noise. Specifically, a fan is also installed inside the duct of the fume extraction device or at the duct's port. The fan includes a volute and an impeller housed within the volute. The axis of the impeller extends vertically, and the airflow... The center position of the inlet is denoted as point F1, the center position of the bottom port of the impeller through the axis of the impeller is denoted as point F2, the line connecting point F1 and point F2 is denoted as line segment F1F2, the sound acquisition device is located in the area between line segment F1F2 and the second side wall in the air duct, the shortest distance between line segment F1F2 and the second side wall in the first direction is denoted as S1, the distance between the first side wall 101 and the second side wall 102 of the air duct 10 is a, and the value range of S1 / a satisfies the following condition: S1 / a≥1 / 10.

[0011] The “center position” of the airflow inlet mentioned above can be understood as the geometric center of a planar area enclosed by the boundary contour of the airflow inlet. If the airflow inlet is a regular structure such as a circle, ellipse, or rectangle, its “center position” is the center point position.

[0012] Considering that the airflow along the duct path is related to the relative positions of the fan and the air inlet in the first direction, and that the sound acquisition device is located near the second sidewall, the distance between the line connecting the fan and the air inlet and the second sidewall needs to be carefully designed to avoid the sound acquisition device being too close to the high-velocity area in the middle of the duct and thus being affected by strong wind noise. Specifically, a fan is also installed inside the duct of the fume extraction device or at the duct's port. The fan includes a volute and an impeller disposed within the volute. The volute includes an annular wall and cover plates connected to both axial ends of the annular wall. The impeller... The axis extends horizontally. The center position of the airflow inlet is denoted as point F1. The center position of the bottom of the annular wall in its width direction is denoted as point F3. The line connecting point F1 and point F3 is denoted as line segment F1F3. The sound acquisition device is located in the area between line segment F1F2 and the second side wall within the air duct. The shortest distance between line segment F1F3 and the second side wall in the first direction is denoted as S2. The distance between the first side wall 101 and the second side wall 102 of the air duct 10 is a. The value range of S2 / a satisfies the following condition: S2 / a ≥ 1 / 10.

[0013] Considering that sound propagation within the duct is affected by reflections from the duct sidewalls, the closer to the sidewall, the more sound is reflected, affecting the signal acquisition by the sound acquisition element. This can lead to a significant difference between the noise signal detected by the sound acquisition element and the main wave propagating through the duct's frontal surface. Therefore, the sound acquisition device should be placed as far away from the duct wall as possible within the duct, i.e., along the main path of noise propagation. This is also for more accurate and comprehensive noise acquisition. However, a larger distance between the sound acquisition device and the second sidewall means that the device is closer to the central area of ​​the duct, where the airflow velocity is also higher, making the sound acquisition device more susceptible to wind noise. Therefore, the distance between the sound acquisition device and the second sidewall needs to be selected within a suitable range. Specifically, the distance between the first and second sidewalls of the duct is denoted as 'a', and the distance between the sound acquisition device and the second sidewall is denoted as 'L1'. L1 and a satisfy the relationship: 0 < L1 / a < 0.3.

[0014] The aforementioned "distance between the sound acquisition device and the second side wall" should be understood as the distance from the side of the sound acquisition device furthest from the second side wall to the second side wall.

[0015] Considering that the airflow velocity within the duct is related to the location and front-to-back dimensions of the airflow inlet, the larger the front-to-back dimensions of the airflow inlet, the greater the impact of wind noise on the sound acquisition device at the same location. Therefore, the sound acquisition device should be placed as close as possible to the second sidewall, and L1 should be appropriately reduced. Similarly, the greater the distance between the center of the airflow inlet and the first sidewall, i.e., the closer the airflow inlet is to the central area of ​​the duct, the greater the impact of wind noise on the sound acquisition device at the same location, and L1 should also be appropriately reduced. The distance between the side of the airflow inlet adjacent to the first sidewall and the first sidewall in the first direction is denoted as c, and the value of c is in the range of 0 < c < 50 mm. The dimension of the airflow inlet in the first direction is denoted as c1, where c1, a, and L1 satisfy the following conditions:

[0016] 0.05 < L1 / a < 0.3, when 1 / 5 < c1 / a < 1 / 3;

[0017] 0.05 < L1 / a < 0.25, when 1 / 3 ≤ c1 / a < 2 / 3.

[0018] In order to ensure that the airflow can flow more smoothly along the extension direction of the duct after entering the duct through the airflow inlet, and to reduce the impact of airflow disturbance caused by abrupt changes in cross-section on the accuracy of noise acquisition by the sound acquisition device, the opening of the airflow inlet is oriented in the same direction as the extension direction of the duct.

[0019] To facilitate the installation of the sound acquisition device in the air duct and to ensure that the sound acquisition device meets the corresponding spacing requirements between the sound acquisition device and the second side wall of the air duct, a crossbeam is provided in the air duct along the direction parallel to the second side wall, and the sound acquisition device is mounted on the crossbeam.

[0020] A single sound acquisition device can be installed near the first sidewall, but it should still be protected from reflections from the left and right sidewalls of the air duct. The position of the sound acquisition device in the second direction should be reasonably selected. The air duct has a third and a fourth sidewall in the second direction. The second direction is perpendicular to the first direction and the extension direction of the air duct. The distance between the third and fourth sidewalls is denoted as b. One sound acquisition device is installed near the first sidewall. The distance between the sound acquisition device and the third sidewall is denoted as b1, and the distance between the sound acquisition device and the fourth sidewall is denoted as b2. b1, b3, and b satisfy the following conditions: 1 / 5 ≤ b1 / b ≤ 1 / 2; 1 / 5 ≤ b2 / b ≤ 1 / 2.

[0021] The aforementioned "distance between the sound acquisition device and the third side wall" should be understood as the distance from the center position of the main body of the sound acquisition device (the center position in the second direction) to the third side wall. Similarly, the aforementioned "distance between the sound acquisition device and the fourth side wall" should be understood as the distance from the center position of the main body of the sound acquisition device (the center position in the second direction) to the fourth side wall.

[0022] Generally, when cooking on one side, the airflow of the range hood on both sides is controlled (e.g., by changing the ventilation area of ​​the oil mesh grilles at the air inlets on both sides). This results in a difference in airflow between the left and right sides of the duct. To minimize or reduce the adverse effects of this airflow difference on the accuracy of sound acquisition, two or more sound acquisition devices can be installed near the first sidewall and spaced as far apart as possible. Specifically, the duct has opposing third and fourth sidewalls in the second direction, which is perpendicular to both the first direction and the duct's extension direction. The distance between the third and fourth sidewalls is denoted as b. At least two sound acquisition devices are installed near the first sidewall, arranged sequentially and at intervals along the second direction. The distance between the sound acquisition device near the third sidewall and the third sidewall is denoted as b1', and the distance between the sound acquisition device near the fourth sidewall and the fourth sidewall is denoted as b2'. b, b1', and b2' satisfy the following conditions: 1 / 6 ≤ b1' / b ≤ 2 / 5; 1 / 6 ≤ b2' / b ≤ 2 / 5.

[0023] Similarly, the "distance between the sound acquisition device and the third side wall" mentioned above should be understood as the distance from the center position of the main body of the sound acquisition device (the center position in the second direction) to the third side wall. Likewise, the "distance between the sound acquisition device and the fourth side wall" mentioned above should be understood as the distance from the center position of the main body of the sound acquisition device (the center position in the second direction) to the fourth side wall.

[0024] As an improvement, a sound acquisition device is also provided within the air duct near the first sidewall. The sound acquisition device near the first sidewall is designated as the first sound acquisition device, and the sound acquisition device near the second sidewall is designated as the second sound acquisition device. The number of the first sound acquisition devices is greater than or equal to the number of the second sound acquisition devices. Considering that the side of the air duct near the airflow inlet is the main path for noise propagation and contains the most comprehensive noise signal information, in a preferred embodiment, a larger number of sound acquisition devices need to be installed along this path to more comprehensively collect noise information within the air duct.

[0025] Designing the sound propagation channel of the sound acquisition device as a first channel segment and a second channel segment arranged at an angle, and placing the sound acquisition element within the first channel segment, effectively isolates the sound acquisition element from external airflow interference and prevents oil contamination from the airflow. The angled arrangement of the first and second channel segments also creates a turning path design for the sound propagation channel, which attenuates high-frequency sounds (such as the high-frequency components of wind noise and high-frequency noise generated by fan systems, etc., and has minimal impact on low-frequency sounds). Therefore, it is well-suited for handling low-frequency noise propagating within the acquisition device, facilitating accurate acquisition of low-frequency noise by the sound acquisition element.

[0026] As an improvement, the extension direction of the second channel segment is consistent with the extension direction of the air duct, and the second sound inlet is located on the leeward side of the housing, with its opening direction consistent with the extension direction of the air duct. The phrase "the extension direction of the second channel segment is consistent with the extension direction of the air duct" can be understood as the overall extension direction of the second channel segment being consistent with or parallel to the extension direction of the air duct, or it can be understood as the overall extension direction of the second channel segment having a slight tilt angle relative to the extension direction of the air duct (e.g., a tilt angle of 0-30°). Considering the need for a sufficiently long second channel segment along the sound propagation path to reduce wind noise and minimize the impact of airflow on sound acquisition, arranging the second channel segment along the air duct extension direction allows the entire acquisition device to be smaller in size perpendicular to the air duct extension direction, thus occupying less space in the range hood's air duct. This results in lower wind resistance at the location of the acquisition device within the air duct, preventing any impact on the stability of airflow within the air duct and simultaneously reducing wind noise to a certain extent. The “leeward side of the casing” mentioned above can be understood as the side of the casing adjacent to the fan system along the extension direction of the air duct.

[0027] To facilitate the smooth entry of sound from the air duct into the sound propagation channel of the sound acquisition device and to reduce excessive sound pressure loss due to excessive bends during sound propagation, the extension direction of the first channel segment is perpendicular to the extension direction of the second extension segment.

[0028] The structural design of the aforementioned sound acquisition device can reduce the impact of wind noise on the accuracy of sound acquisition to a certain extent. Therefore, the sound acquisition device can be positioned closer to the airflow inlet in the first direction to more comprehensively acquire noise signals within the duct. Specifically, in the preferred embodiment, the plane formed by the points at the middle position of the duct in the first direction and along the duct extension direction is used as the reference plane. The distance between the sound acquisition device located near the second sidewall and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.4≤a1 / a<0.5.

[0029] The aforementioned "distance between the sound acquisition device and the reference plane" should be understood as the distance from the side of the sound acquisition device closest to the reference plane to the reference plane.

[0030] As an improvement, the housing also has an extension wall at the second sound inlet, extending along the opening direction of the second sound inlet. Considering that the sound acquisition device is used in the duct of the fume extraction device, providing an extension wall at the second sound inlet of the housing, extending along the opening direction of the second sound inlet, can form a "flow dead zone" in the inner region corresponding to the extension wall. The airflow in this area is basically still, and airflow pressure fluctuations cannot be transmitted, but it does not affect the transmission of sound waves. That is, the flow dead zone can block the transmission of turbulent vortex pulsations, and at the same time make the turbulent vortices farther away from the sound acquisition element, reducing the transmission of turbulent airflow pulsations to the sound acquisition element, while the pressure pulsations of noise are not affected, thus improving the accuracy of sound acquisition.

[0031] The design of the extended wall on the housing of the aforementioned sound acquisition device can further enhance the effect of wind noise reduction. Therefore, the sound acquisition device can be positioned closer to the airflow inlet in the first direction to more comprehensively collect noise signals within the duct. Specifically, in the preferred embodiment, the plane formed by the points at the middle position of the duct in the first direction and along the duct extension direction is used as the reference plane. The distance between the sound acquisition device located near the second side wall and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.3≤a1 / a<0.5.

[0032] The housing can be a one-piece structure, such as a one-piece bent tube structure. However, for the convenience of installing components such as the sound acquisition element, the housing is preferably a split structure designed to be assembled together using fasteners. Specifically, the housing includes a mounting frame and a windproof cover. The front side wall of the mounting frame has a receiving groove. The sound acquisition element is placed in the receiving groove, which constitutes the first channel segment. The windproof cover covers the mounting frame and defines a sound acquisition channel that communicates with the receiving groove and is located in front of the receiving groove. This sound acquisition channel constitutes the second channel segment. The windproof cover defines the second sound inlet at its leeward end with the mounting frame, and an extension wall is formed at the second sound inlet, extending along the opening direction of the second sound inlet.

[0033] To reduce the adverse impact on the accuracy of sound acquisition caused by airflow disturbance caused by direct impact of airflow on the windproof cover, the windproof cover has a guide surface that gradually slopes towards the inside of the air duct along the direction of airflow. The angle formed between the guide surface and the extension direction of the air duct is denoted as A, and the value of A is in the range of A≤60°.

[0034] The design of the extended wall on the housing of the aforementioned sound acquisition device can further enhance the effect of wind noise reduction. Therefore, the sound acquisition device can be positioned closer to the airflow inlet in the first direction to more comprehensively collect noise signals within the duct. Specifically, in the preferred embodiment, the plane formed by the points at the middle position of the duct in the first direction and along the duct extension direction is used as the reference plane. The distance between the sound acquisition device located near the second side wall and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.2≤a1 / a<0.5.

[0035] As an improvement, the second channel section is also equipped with a windproof and sound-permeable component. This windproof and sound-permeable component further enhances the windproof effect of the sound acquisition device, effectively eliminating wind noise. Even if a small amount of airflow enters the sound acquisition channel, pressure pulsations can be weakened within the windproof and sound-permeable component, thereby reducing the impact on the accuracy of microphone sound acquisition. The aforementioned windproof and sound-permeable component is made of porous sound-absorbing material, such as sound-absorbing cotton.

[0036] To further improve the oil-proof effect and prevent the sound acquisition element from coming into contact with oil, an oil-proof and sound-permeable membrane is also provided in the first channel section.

[0037] The technical solution adopted by this utility model to solve the second technical problem is as follows: a range hood, including an air duct and an active noise reduction system. The active noise reduction system includes a sound acquisition device, a speaker and a controller. The controller receives noise signals from the sound acquisition device and generates noise reduction signals, which are then transmitted to the speaker to emit noise reduction waves. The sound acquisition device and the speaker are both located in the air duct of the range hood. The range hood also includes the installation structure of the active noise reduction system of the above-mentioned range hood.

[0038] Compared with existing technologies, the advantages of this invention are as follows: The airflow velocity is higher on the side of the duct adjacent to the airflow inlet in the first direction, while the airflow velocity is lower on the side farther from the airflow inlet. Based on the airflow state within the duct, placing the sound acquisition device on the side farther from the airflow inlet can better reduce the adverse effects of secondary noise (wind noise) directly impacting the sound acquisition device, thus improving the accuracy of sound acquisition. However, considering that the side of the duct adjacent to the airflow inlet is the main path for noise propagation and contains the most comprehensive noise signal information, a special structural design is implemented for the sound acquisition device. Specifically, the sound acquisition element is housed within a casing, and the sound propagation channel within the casing is divided into two segments arranged at an angle. This makes the sound propagation channel of the sound acquisition device a turning path design. This turning path design weakens high-frequency sounds (such as the high-frequency components of wind noise and high-frequency components generated by the fan system, etc., which are non-target noises) while having less impact on low-frequency sounds. Therefore, it is well-suited for low-frequency noise propagation within the acquisition device, facilitating accurate acquisition by the sound acquisition element. Since the structural design of the aforementioned sound acquisition device can reduce the impact of wind noise on the accuracy of sound acquisition to a certain extent, the sound acquisition device can be positioned closer to the airflow inlet in the first direction to more comprehensively acquire noise signals within the air duct, thereby further improving the accuracy of sound acquisition and enhancing the active noise reduction effect. Attached Figure Description

[0039] Figure 1 This is a vertical sectional view of the range hood of this utility model, cut along the front-to-back direction (the fan is placed horizontally);

[0040] Figure 2 This is a vertical sectional view of the air duct portion of the range hood in an embodiment of the present utility model, cut along the left and right direction (only one sound collection device is provided near the first side wall);

[0041] Figure 3 This is a vertical sectional view of the duct section of the range hood in this embodiment of the present invention, cut along the left and right direction (only three sound collection devices are set near the first side wall);

[0042] Figure 4 This is a three-dimensional structural diagram of the sound acquisition device according to an embodiment of the present utility model;

[0043] Figure 5 This is an exploded view of the sound acquisition device according to an embodiment of the present invention;

[0044] Figure 6 This is a vertical sectional view of the sound acquisition device according to an embodiment of the present utility model, cut along the front-back direction;

[0045] Figure 7 for Figure 6 A schematic diagram of the structure after removing the windproof and sound-permeable components;

[0046] Figure 8 This is a transverse cross-sectional view of the sound acquisition device according to an embodiment of the present utility model, cut along the left-right direction.

[0047] Figure 9 A schematic diagram of the sound propagation process at the first sound inlet of the mounting bracket;

[0048] Figure 10a A spectrum diagram of sound acquisition designed for a sound acquisition device with no bends in the sound propagation path;

[0049] Figure 10b Spectrum diagram of sound acquisition after setting a turning path in the sound propagation path of the sound acquisition device

[0050] Figure 11a A spectrum diagram of sound acquisition without an extension wall on the windproof cover of the sound acquisition device;

[0051] Figure 11b A spectrum diagram of sound collected behind an extension wall installed on the windproof cover of the sound acquisition device;

[0052] Figure 12a A spectrum diagram of sound collected without a guide surface on the windshield of the sound acquisition device;

[0053] Figure 12b The spectrum of sound collected after a guide surface was installed on the windproof cover of the sound acquisition device;

[0054] Figure 13 The spectrum obtained by the sound acquisition device at a position of a1 / a = 0.5 (specifically, close to 0.5);

[0055] Figure 14 The spectrum obtained by setting the sound acquisition device at a1 / a = 0.15;

[0056] Figure 15 This is a vertical sectional view of the range hood of this utility model, cut along the front-to-back direction (the fan is placed vertically). Detailed Implementation

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0058] In the specification and claims of this utility model, terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," are used to describe various exemplary structural parts and elements of this utility model. However, the use of these terms is merely for the purpose of explanation and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this utility model can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0059] Figures 1-15 The installation structure of the active noise reduction system of the fume extraction device of this utility model and a preferred embodiment of the fume extraction hood are shown.

[0060] Active noise reduction systems are typically installed in the duct 10 of kitchen appliances such as range hoods or integrated cooktops with fume extraction functions. Sound acquisition devices, a crucial component of active noise reduction systems, are also located within the duct 10 of the fume extraction device. Taking a range hood as an example, the aforementioned "duct 10" can refer to the range hood's casing or a box structure with a dedicated channel for the passage of fumes, such as the channel between the fan system and the fume collection hood in a ceiling-mounted range hood. See details... Figure 1 An active noise cancellation system generally includes a sound acquisition device 1, a speaker, and a controller. The sound acquisition device 1 includes a sound acquisition element 11 (generally a microphone). The microphone collects the noise generated when the range hood is operating. The collected noise sound waves are then transmitted to the controller in the form of electrical signals. After analysis and processing, the controller sends a command to the speaker to control the speaker to emit sound waves that match the noise sound waves, thereby neutralizing the noise sound waves and achieving the noise reduction effect. The sound acquisition device in this embodiment can be used to install the aforementioned sound acquisition element 11 and provide protection against oil and wind.

[0061] The range hood's duct 10 extends vertically, with its top connected to the fan system 90. The fan system 90 can be installed within the ceiling, or it can be installed within the duct 10, which can be formed by the internal space of the range hood's fan frame. The bottom of the duct 10 is connected to the range hood's smoke collection hood 61. The duct 10 includes a first sidewall 101 and a second sidewall 102 facing each other front-to-back (in the first direction), and a third sidewall 103 and a fourth sidewall 104 facing each other left-to-right (in the second direction). The first sidewall 101 is located on the front side, and the second sidewall 102 is located on the rear side. The rear bottom of the duct 10 also has an airflow inlet 105 connected to the smoke collection hood 61, with the opening of the airflow inlet 105 facing upwards, i.e., consistent with the extension direction of the duct 10. The rear side of the smoke hood 61 has a vertically extending smoke inlet chamber 611, the top of which is connected to the aforementioned airflow inlet 105. The front side of the smoke inlet chamber 611 also has an air inlet 610 for external airflow to enter.

[0062] The airflow inlet 105 is located near the first sidewall 101, i.e., rearward, while at least one sound acquisition device is located near the second sidewall 102 of the air duct 10, i.e., forward. Specifically, taking the plane formed by points at the middle position of the air duct 10 in the first direction and extending along the direction of the air duct 10 as a reference plane, the above-mentioned "airflow inlet 105 is located near the first sidewall 101, and at least one sound acquisition device 1 is located near the second sidewall 102" can be understood as: the airflow inlet and at least one sound acquisition device 1 are located on opposite sides of the above-mentioned reference plane. Since the airflow velocity is higher on the side of the air duct 10 near the airflow inlet 105 in the transverse direction (i.e., the first direction), and lower on the side away from the airflow inlet 105, placing the sound acquisition device on the side of the air duct 10 away from the airflow inlet 105 according to the airflow state can better reduce the adverse effects of secondary noise (wind noise) generated by the direct impact of airflow on the sound acquisition device and improve the accuracy of sound acquisition.

[0063] like Figure 1 As shown, the fan can be placed horizontally. Specifically, the fan 90 includes a volute 91 and an impeller 92 disposed within the volute 91. The axis of the impeller 92 extends vertically, that is, in the same direction as the extension of the air duct 10. The center position of the airflow inlet 105 is denoted as point F1, and the center position of the bottom port of the impeller 92 through the axis of the impeller 92 is denoted as point F2. The line connecting points F1 and F2 is denoted as line segment F1F2. Viewed from a vertical cross-section of the air duct 10 along the first direction, the sound acquisition device 1 is located within the air duct 10 in the area between line segment F1F2 and the second sidewall 102. Figure 1As shown, the shortest distance in the first direction between line segment F1F2 and the second sidewall 102 is denoted as S1, and the distance between the first sidewall 101 and the second sidewall 102 of the air duct 10 is a. Considering that the airflow in the airflow path within the air duct is related to the relative position of the fan and the airflow inlet in the first direction, and the sound acquisition device is located near the second sidewall, the distance between the line connecting the fan and the airflow inlet and the second sidewall needs to be reasonably designed to avoid the sound acquisition device being too close to the high-velocity area in the middle of the air duct and being affected by strong wind noise. Specifically, the value range of S1 / a satisfies the following condition: S1 / a ≥ 1 / 10.

[0064] like Figure 15 As shown, the fan can also be vertically mounted. Specifically, the fan 90 includes a volute 91 and an impeller 92 disposed within the volute 91. The axis of the impeller 92 extends horizontally, specifically in line with the first direction. The volute 91 includes an annular wall 911 and cover plates 912 connected to both axial ends of the annular wall 911. The axis of the impeller 92 extends horizontally. The center position of the airflow inlet 105 is denoted as point F1, and the center position of the bottom of the annular wall 911 of the volute in its width direction is denoted as point F3. The line connecting point F1 and point F3 is denoted as line segment F1F3. Viewed from the vertical section of the duct 10 along the first direction, the sound acquisition device 1 is located within the area between line segment F1F3 and the second sidewall 102 in the duct 10. The shortest distance between line segment F1F3 and the second sidewall 102 in the first direction is denoted as S2, and the distance between the first sidewall 101 and the second sidewall 102 of the duct 10 is a. Considering that the airflow along the flow path in the duct is related to the relative position of the fan and the air inlet in the first direction, and the sound acquisition device is set near the second side wall, the distance between the line connecting the fan and the air inlet and the second side wall needs to be reasonably designed to avoid the sound acquisition device being too close to the high-velocity area in the middle of the duct and being affected by strong wind noise. Specifically, the value range of S2 / a satisfies the following condition: S2 / a≥1 / 10.

[0065] Considering that sound propagation within the duct 10 is affected by reflections from the sidewalls of the duct 10, the closer to the sidewalls, the more sound is reflected, affecting the accuracy of signal acquisition by the sound acquisition element 11. This can lead to a significant difference between the noise signal detected by the sound acquisition element 11 and the main wave propagating through the duct 10. Therefore, the sound acquisition device should be placed as far away from the walls of the duct 10 as possible, i.e., on the main path of noise propagation within the duct 10. Of course, placing the sound acquisition device on the main path of noise propagation within the duct 10 is also for more accurate and comprehensive noise acquisition. The greater the distance between the sound acquisition device and the second sidewall 102, the closer the sound acquisition device is to the central area of ​​the air duct 10. The airflow velocity near the central area of ​​the air duct 10 is also greater, and the sound acquisition device 1 is more affected by wind noise. Therefore, the distance between the sound acquisition device and the second sidewall 102 needs to be selected within a suitable range. Specifically, in this embodiment, the distance between the first sidewall 101 and the second sidewall 102 of the air duct 10 is a, and the distance between the sound acquisition device and the second sidewall 102 is denoted as L1. The relationship between L1 and a is: 0 < L1 / a < 0.3, and the preferred range is: 0.05 < L1 / a < 0.25. Using the plane formed by points at the midpoint of the air duct 10 in the first direction and extending along the air duct 10 as a reference plane, the distance between the sound acquisition device adjacent to the first sidewall 101 and the reference plane is denoted as a1. a1 and a satisfy the condition: 0.2 < a1 / a < 0.5, with a preferred range of 0.25 < a1 / a < 0.35. The aforementioned "distance between the sound acquisition device and the second sidewall 102" should be understood as the distance between the side of the sound acquisition device furthest from the second sidewall 102 and the second sidewall 102 itself.

[0066] To prevent vibrations on the second sidewall 102 from being directly transmitted to the sound acquisition device and affecting the accuracy of the microphone's sound acquisition, a horizontal beam 106 extending to the left and right is provided inside the air duct 10. This horizontal beam 106 extends horizontally and is parallel to the first sidewall 101. The sound acquisition device located adjacent to the second sidewall 102 is correspondingly mounted on the aforementioned horizontal beam 106.

[0067] Considering that the airflow velocity at different locations within the duct 10 is related to the position of the airflow inlet 105 and its front-to-back dimensions, the larger the front-to-back dimensions of the airflow inlet 105, the greater the impact of wind noise on the sound acquisition device at the same location. Therefore, the sound acquisition device should be placed as close as possible to the second sidewall 102, and the aforementioned L1 value should be appropriately reduced. Similarly, the greater the distance between the center of the airflow inlet 105 and the first sidewall 101, that is, the closer the airflow inlet 105 is to the duct, the better. In the central area of ​​10, the sound acquisition device at the same location is more affected by wind noise, and L1 should be appropriately reduced. Specifically, the distance between the side of the airflow inlet 105 adjacent to the first sidewall 101 and the first sidewall 101 in the first direction is denoted as c. In order to allow the flue gas to pass smoothly through the front air inlet of the air inlet chamber of the smoke hood for intake and exhaust, the airflow inlet 105 needs to be arranged as far back as possible. Preferably, the value of c is in the range of 0 < c < 50 mm, and preferably, the value of c is in the range of 2 < c < 20 mm. The dimension of the airflow inlet 105 in the first direction is denoted as c1, where c1, a, and L1 satisfy the following conditions:

[0068] 0.05 < L1 / a < 0.3, when 1 / 5 < c1 / a < 1 / 3;

[0069] 0.05 < L1 / a < 0.25, when 1 / 3 ≤ c1 / a < 2 / 3.

[0070] The sound acquisition device installed near the first sidewall 101 can be a single device, or two or more. For example... Figure 2 It is shown that only one sound acquisition device is set near the first sidewall 101 to avoid the influence of sound acquisition by the reflection of the left and right sidewalls of the air duct 10. The position of the sound acquisition device in the second direction should be reasonably selected. Specifically, the distance between the third sidewall 103 and the fourth sidewall 104 is denoted as b. There is one sound acquisition device near the first sidewall 101. The distance between the sound acquisition device and the third sidewall 103 is denoted as b1. The distance between the sound acquisition device and the fourth sidewall 104 is denoted as b2. b1, b3 and b satisfy the following conditions: 1 / 5 ≤ b1 / b ≤ 1 / 2; 1 / 5 ≤ b2 / b ≤ 1 / 2.

[0071] Generally, during unilateral cooking, the airflow on both sides of the range hood is controlled (e.g., by changing the ventilation area of ​​the oil mesh grilles at the left and right air inlets). This results in a difference in airflow between the left and right sides of the duct 10. To minimize or reduce the adverse effects of this airflow difference on the accuracy of sound acquisition, in another preferred embodiment, two or more sound acquisition devices can be installed adjacent to the first sidewall 101, and they should be spaced as far apart as possible. Figure 3Three sound acquisition devices are shown. The three sound acquisition devices are arranged sequentially at intervals along the second direction. The distance between the sound acquisition device adjacent to the third side wall 103 and the third side wall 103 is denoted as b1', and the distance between the sound acquisition device adjacent to the fourth side wall 104 and the fourth side wall 104 is denoted as b2'. The following conditions are satisfied between b, b1', and b2': 1 / 6 ≤ b1' / b ≤ 2 / 5; 1 / 6 ≤ b2' / b ≤ 2 / 5.

[0072] Considering that the side of the air duct 10 adjacent to the airflow inlet 105 is the main path for noise propagation and contains the most comprehensive noise signal information, it is necessary to install more sound acquisition devices 1 on this path to collect noise information in the air duct more comprehensively. In this embodiment, a sound acquisition device is also installed in the air duct 10 adjacent to the first side wall 101. The sound acquisition device 1 installed adjacent to the first side wall 10 is referred to as the first sound acquisition device, and the sound acquisition device 1 installed adjacent to the second side wall 102 is referred to as the second sound acquisition device. The number of first sound acquisition devices is greater than the number of second sound acquisition devices. Of course, the number of first sound acquisition devices and the number of second sound acquisition devices can also be the same.

[0073] The sound acquisition device of this embodiment includes a sound acquisition element 11 and a housing 2. The housing 2 defines a sound propagation channel, which includes a first channel segment and a second channel segment connected sequentially. The sound acquisition element 11 is located in the first channel segment, which has a first sound inlet 211 communicating with the second channel segment. The housing 2 has a second sound inlet 45 for external sound to enter the second channel segment. The extension line of the opening direction of the first sound inlet 211 intersects the extension line of the opening direction of the second sound inlet 45. In a preferred embodiment, both the first and second channel segments are straight channels, and the extension lines of the first and second channel segments intersect. The extension line of the first channel segment can be understood as the line connecting the location of the sound inlet of the channel segment to the location of the sound acquisition element 11, and the extension line of the second channel segment can be understood as the line connecting the location of the sound inlet of the channel segment to the location of the sound outlet.

[0074] The sound acquisition device is located below the fan system, meaning that the noise generated by the fan system propagates downwards along the air duct 10, and the sound acquisition device is positioned precisely along the downward propagation path within the air duct 10. In addition to the housing, the sound acquisition device includes an oil-proof and sound-permeable membrane 28 and a windproof and sound-permeable component 30. The housing includes a mounting bracket 20 and a windproof cover 40.

[0075] The mounting bracket 20 can be installed on the side wall or crossbeam of the air duct 10. Its front side wall has a receiving slot 21 for placing the sound acquisition element 11, which constitutes the first channel section of the aforementioned housing 2. The front of the receiving slot 21 has an opening serving as a first sound inlet 211 for sound to enter the receiving slot 21. This first sound inlet 211 should be understood as an opening that allows external (in this embodiment, a sound acquisition channel) sound to enter the receiving slot 21 and be effectively acquired by the sound acquisition element. Figure 9 The openings defined by the boundary points A1, A2, etc. of the middle receiving groove 21 in the circumferential direction do not necessarily refer to the maximum opening at the front of the receiving groove 21.

[0076] The mounting bracket 20 also has a third mounting portion 263 extending to the left and right sides respectively, protruding beyond the wind shield 40, and a fourth mounting portion 264 extending downward at the bottom of the mounting bracket 20, protruding beyond the wind shield 40. Both the third mounting portion 263 and the fourth mounting portion 264 are connected to the crossbeam inside the air duct 10 by screws. The lower part of the receiving groove 21 of the mounting bracket 20 has a forward-extending connecting post 265, and the wind shield 40 can be connected to the connecting post 265 of the mounting bracket 20 by screws 50.

[0077] The wind shield 40 includes a left side wall 411 and a right side wall 412 arranged opposite each other and spaced apart, and a front side wall 413 connecting the front edge of the left side wall 411 and the front edge of the right side wall 412, thereby forming a rear-opening shield structure. The front side wall 413 of the wind shield 40 is located in front of the receiving groove 21 of the mounting bracket 20. The front side wall 413 of the wind shield 40 has a shape along the airflow direction within the air duct 10 (e.g., ...). Figure 6The guide surface 4130 (in the direction indicated by the hollow arrow) gradually slopes towards the inside of the air duct 10. Specifically, the guide surface 4130 is located at the lower part of the front sidewall 413, that is, at the windward end of the front sidewall 413. It slopes forward from bottom to top, while the upper part of the front sidewall 413 is basically vertically extended and is opposite to the portion of the receiving groove 21 of the mounting bracket 20 in the front-back direction. Along the airflow direction inside the air duct 10, the guide surface 4130 of the wind shield 40 is located upstream of the receiving groove 21 of the mounting bracket 20. Arranging the guide surface 4130 of the wind shield 40 lower also ensures that there is sufficient space inside the wind shield 40, opposite to the front of the receiving groove 21, to arrange components such as the windproof sound-permeable component 30 and the oil-proof sound-permeable membrane 28. Furthermore, considering that the excessively large tilt angle of the guide surface 4130 towards the inside of the air duct 10 will also affect the airflow within the air duct 10 to some extent, such as affecting the air volume or generating additional noise, the tilt angle of the guide surface 4130 of the wind shield 40 needs to be reasonably designed. The included angle formed between the guide surface 4130 of the wind shield 40 and the side wall of the air duct 10 used to install the wind shield 40 (i.e., the extension direction of the air duct) is denoted as A, and the value range of A is: A≤60°.

[0078] To improve the oil-proof effect, the windproof cover 40 in this embodiment can be made of plastic or metal.

[0079] In this embodiment, the windproof cover 40 and the front side of the mounting bracket 20 form a vertically extending gap channel in the front-rear direction. The upper end of this gap channel (i.e., the end closer to the noise source) is open, and the lower end (i.e., the end away from the noise source) is closed, which is the sound acquisition channel 200. The sound acquisition channel 200 is located on the front side of the mounting bracket 20, thus constituting the second channel segment of the aforementioned housing 2. More specifically, a second sound inlet 45, which communicates with the sound acquisition channel 200, is defined between the leeward end of the windproof cover 40 (i.e., the section along the extension direction of the air duct, close to the fan system of the range hood) and the front side wall of the mounting bracket 20. The opening direction B4 of the second sound inlet 45 faces upward. In this embodiment, both the air duct 10 and the sound acquisition channel 200 extend vertically, that is, the extension direction of the sound acquisition channel 200 is consistent with the extension direction B2 of the air duct 10. Considering that the ideal noise acquisition method for the sound acquisition element 11 is to acquire the tiny pressure fluctuations generated by the noise in a stable flow field, since the second sound inlet 45 is located at the leeward end of the windproof cover 40, when the airflow in the duct 10 passes through the top of the windproof cover 40, the sudden change in airflow will cause the flow field to become unstable. When the flow field is unstable, pressure fluctuations caused by changes in airflow will occur, causing the tiny noise pressure to be covered by the airflow pressure fluctuations, thus affecting the accuracy of the sound acquisition element 11 in acquiring the sound. Specifically: as shown in Figure 10, the target noise sound pressure and the airflow turbulence pressure are both pressure pulsations in the air. One of the main differences between the two is that the magnitude of the sound wave is relatively small, 2 to 3 orders of magnitude smaller than the airflow pressure pulsation. Therefore, when the microphone acquires data, if both pressure pulsations are acquired at the same time, the sound pressure pressure pulsation is often covered by the airflow pressure pulsation, thus making it impossible to accurately acquire the noise. In this application, airflow generates turbulent vortices when passing through the protective cover shell. These turbulent vortices cause pressure pulsations in the airflow, which are then transmitted to the microphone through the gaps in the windproof and sound-permeable component 30 and the oil-proof and sound-permeable membrane 28, thus affecting the accuracy of noise acquisition. On the other hand, these turbulences themselves also generate secondary noise, which also affects the accuracy of primary noise acquisition. To solve the above technical problems, in this embodiment, the windproof cover 40 is constructed with an extension wall 46 at the second sound inlet 45 extending along the opening direction of the second sound inlet 45 (that is, along the airflow direction within the air duct 10). The vertical length of the windproof cover 40 is denoted as H, and the length of the extension wall 40 is denoted as L, where 0.4 < L / H < 1. This creates a "flow dead zone" in the inner region corresponding to the extension wall 46 (see details). Figure 9In this area, the airflow is basically still, and the airflow pressure fluctuations cannot be transmitted, but the transmission of sound waves is not affected. That is, this dead zone of flow blocks the transmission of turbulent vortex pulsations, and at the same time makes the turbulent vortexes farther away from the sound acquisition element, reducing the transmission of airflow turbulent pulsations to the sound acquisition element, while the pressure pulsations of noise are not affected, thus improving the accuracy of sound acquisition.

[0080] In this embodiment, the air duct 10 also extends vertically, that is, the extension direction of the sound acquisition channel 200 is consistent with the extension direction B2 of the air duct 10. The opening direction B1 of the first sound inlet 211 intersects with the extension direction B3 of the sound acquisition channel 200 to form a first included angle. Considering that if the included angle between the orientation B1 of the first sound inlet 211 and the extension direction B3 of the sound acquisition channel 200 is too small, oil will still enter the receiving tank 21 through the first sound inlet 211 and contaminate the sound acquisition element 11. If the included angle between the orientation B1 of the first sound inlet 211 and the extension direction B3 of the sound acquisition channel 200 is too large, the sound propagation path will turn too much, which will have an adverse effect on the sound propagation, that is, a part of the sound pressure will be lost, which is not conducive to the accurate acquisition of noise by the sound acquisition element. Therefore, the included angle between the orientation of the first sound inlet 211 and the extension direction B3 of the sound acquisition channel 200 also needs to be reasonably designed. Preferably, the first included angle in this embodiment is 90°, that is, the opening direction B1 of the first sound inlet 211 is perpendicular to the extension direction B3 of the sound acquisition channel 200.

[0081] The lower section of the sound acquisition channel 200 is opposite to the first sound inlet 211 at the front of the receiving slot 21 of the mounting bracket 20 in the front-back direction. After the windproof cover 40 is installed, it can effectively prevent the high-speed oil fume airflow from directly impacting the windproof sound-permeable component 30, greatly reducing the pollution of the windproof sound-permeable component 30 by oil fumes. At the same time, after the windproof cover 40 and the mounting bracket 20 are combined, only the upper second sound inlet 45 is retained, which directly isolates the noise of the lower airflow and the noise interference of secondary turbulence, so that the noise entering the windproof sound-permeable component 30 mainly comes from the top, that is, the direction of the main noise source of the range hood, thereby ensuring the accuracy of noise acquisition.

[0082] Since the sound acquisition element 11 is installed in the receiving slot 21 of the mounting bracket 20 and a windproof cover 40 is provided outside the mounting bracket 20, the interference of the airflow in the air duct 10 to the sound acquisition element 11 can be effectively isolated, and the oil in the airflow can be prevented from contaminating the sound acquisition element 11. At the same time, a windproof sound-permeable component 30 is provided in the sound acquisition channel formed between the mounting bracket 20 and the windproof cover 40, which can effectively reduce the impact of wind noise. Even if a small amount of airflow enters the sound acquisition channel 200, the pressure pulsation can be weakened in the windproof sound-permeable component 30, thereby reducing the impact on the accuracy of microphone sound acquisition. Furthermore, considering that the noise in the duct 10 (mainly from the fan system) propagates along the extension direction of the duct 10 and in the opposite direction to the airflow direction within the duct 10, arranging the sound acquisition channel 200 along the extension direction of the duct allows the second sound inlet 45 of the sound acquisition channel 200 to face the sound source so that the noise can be directly received. Also, considering the need for a sufficiently long windproof and sound-permeable component 30 along the sound propagation path to reduce wind noise and decrease the impact of airflow in the duct 10 on sound acquisition, this embodiment arranges the sound acquisition channel 200, which houses the windproof and sound-permeable component 30, along the extension direction of the duct 10. This allows the entire sound acquisition device to be smaller in size perpendicular to the duct extension direction, thus occupying less space in the duct 10 of the range hood. Consequently, the wind resistance at the location of the sound acquisition device within the duct 10 is reduced, thus not affecting the stability of the airflow within the duct 10 and simultaneously reducing wind noise to a certain extent. Based on this, considering that the duct environment of the range hood is full of oil, if the opening direction B1 of the first sound inlet 211 is consistent with the extension direction B3 of the sound collection channel 200, the sound collection element 11 is easily contaminated by the oil flowing down the duct 10. Therefore, in this embodiment, the opening direction B1 of the first sound inlet 211 of the receiving groove 21 is set at a certain angle with the extension direction B3 of the sound collection channel 200. This makes the entire sound propagation path of the noise in the duct 10 from the second sound inlet 45 into the sound collection channel 200 and then propagating to the location of the sound collection element 11 in the receiving groove 21 a turning path. This turning path can prevent too much oil from directly passing through the sound collection channel 200 and contacting the sound collection element 11. Instead, most of the oil adheres to the side wall of the sound collection channel 200 or the windproof and sound-permeable part 30, thereby keeping the sound collection element 11 as far away from the oil as possible and extending the service life of the sound collection element 11.Furthermore, considering that the target noise (mainly from the fan system) to be collected by the active noise cancellation system is low-frequency noise, the sound propagation path within the sound acquisition device adopts a turning path design. This weakens high-frequency sounds (such as the high-frequency sound portion of wind noise and non-target noise such as the high-frequency sound components generated by the fan system) while having a smaller impact on low-frequency sounds. Therefore, it is well-suited for the propagation of low-frequency noise within the sound acquisition device, facilitating accurate acquisition by the sound acquisition element 11. The main reason is that low-frequency noise has a longer wavelength, making it better suited to the bends and irregular shapes of pipes. When low-frequency noise propagates in a curved pipe, its longer wavelength makes it less susceptible to obstruction and reflection, thus allowing for better propagation and diffusion. High-frequency noise, on the other hand, has a shorter wavelength and is easily reflected and absorbed by the shape and bends of the pipe, making it more difficult for it to propagate and diffuse within the pipe compared to low-frequency noise.

[0083] An oil-resistant and sound-permeable membrane 28 covers the first sound inlet 211 of the receiving groove 21 of the mounting bracket 20, specifically at the edge of the front opening of the receiving groove 21. More specifically, to facilitate installation of the oil-resistant and sound-permeable membrane 28 and ensure its sealing after installation, the receiving groove 21 also forms an annular stepped portion 210 at the edge of its first sound inlet 211, and the oil-resistant and sound-permeable membrane 28 is disposed on this annular stepped portion 210. To ensure the oil-resistant performance of the oil-resistant and sound-permeable membrane 28 while effectively transmitting sound waves, the oil-resistant and sound-permeable membrane 28 in this embodiment is preferably a polyethylene film. Wherein, such as Figure 3 As shown, there is a fourth distance, denoted as f, between the oil-proof sound-permeable membrane 28 and the sound acquisition element 11. The value of f is in the range of f ≥ 2mm. This avoids contact between the membrane and the sound acquisition element 11 due to membrane vibration or micro-deformation, which could lead to variations in sound propagation and affect the accuracy of sound acquisition. It can be understood that the fourth distance f between the oil-proof sound-permeable membrane 28 and the sound acquisition element 11 refers to the distance between the oil-proof sound-permeable membrane 28 and the microphone chip on the sound acquisition element 28. That is, the oil-proof sound-permeable membrane 28 can have partial contact with other components of the circuit board where the microphone chip is located (such as solder joints or fixing screws). The windproof sound-permeable component 30 does not directly contact the oil-proof sound-permeable membrane 28 to ensure the oil-proof effect. Specifically, the oil-proof sound-permeable membrane 28 and the main body of the windproof sound-permeable component 30 have a sixth distance, denoted as n, in the front-to-back direction. To avoid the oil-proof sound-permeable membrane 28 coming into contact with the windproof sound-permeable component 30 and affecting the sound transmission effect at this point, the sixth distance n between the oil-proof sound-permeable membrane 28 and the windproof sound-permeable component 30 should be greater than 0.1 mm, preferably within the range of 0.5 mm to 3 mm.

[0084] To effectively mitigate airflow and eliminate airflow impact, the windproof sound-permeable component 30 is made of porous sound-absorbing material, such as polyurethane foam or melamine foam, with a porosity greater than 70%. In this embodiment, the windproof sound-permeable component 30 not only prevents airflow from impacting the oil-proof sound-permeable membrane 28 and generating additional noise, but also, due to its porous material properties, absorbs high-frequency components of sound energy, achieving a filtering function for noise signals. More specifically, the front sidewall of the windproof sound-permeable component 30 is fitted against the rear sidewall of the front sidewall 413 of the windproof cover 40, thus compressing the component. This compression increases the material density, effectively reducing the possibility of airflow pressure pulsation penetration and further enhancing the windproof effect.

[0085] The windproof and sound-permeable component 30 of this embodiment includes an extension section 301 extending upward from the top edge of the first sound inlet 211 of the receiving groove 21, and the length of the extension section 301 of the windproof and sound-permeable component 30 is denoted as h, and the dimension of the first sound inlet 211 of the receiving groove 21 in the vertical direction is m, wherein the value range of h / m is: 0.125≤h / m≤0.6. Since the sound acquisition channel 200 has a vertically extending section and a horizontally extending section, that is, there is a turning part at the first sound inlet 211 of the receiving groove 21, if the extension length of the outer peripheral edge of the windproof sound-permeable component 30 relative to the edge of the first sound inlet 211 of the receiving groove 21 is too short (e.g., h / m is less than 0.125), it will also be greatly affected by wind noise. After the above parameter design, the windproof effect of the windproof sound-permeable component is effectively guaranteed, and the accuracy of sound acquisition is avoided due to the excessively short extension length of the outer peripheral edge of the windproof sound-permeable component. Of course, considering the adverse effect of the windproof sound-permeable component 30 on sound attenuation, the length of the extension section 301 of the windproof sound-permeable component 30 should not be too large. If h / m is greater than 0.6, it will cause the sound to not effectively meet the sound pressure requirements of the sound acquisition element 11 when it propagates to the receiving groove 21, thus reducing the accuracy of noise acquisition.

[0086] To ensure windproof performance, the front-to-back dimension (thickness) of the main body of the windproof sound-permeable component 30 is denoted as e, where e ranges from 40mm ≥ e ≥ 3mm. Specifically, when e ≥ 3mm, the windproof sound-permeable component 30 can effectively prevent the airflow in the duct from directly impacting the sound-collecting element 11. However, considering the adverse effects of the windproof sound-permeable component 30 (generally made of porous material that can prevent airflow disturbance and transmit sound) on sound attenuation, the front-to-back dimension (thickness) of the windproof sound-permeable component 30 cannot be too large, and e ≤ 40mm is required. Meanwhile, given a fixed front-to-back dimension (i.e., thickness) of the windproof sound-permeable component 30, the left-to-right dimension d1 of the main body of the windproof sound-permeable component 30 must also be adapted accordingly. That is, e / d1 needs to be reasonably limited. Specifically, if e / d1 is too small (e.g., e / d1 < 0.2), it means that the main body of the windproof sound-permeable component 30 is larger in the left-to-right direction, increasing the area of ​​its upper part in contact with oil stains, which will directly affect the service life of the windproof sound-permeable component 30. If e / d1 is too large (e.g., e / d1 > 0.5), it means that the main body of the windproof sound-permeable component 30 is smaller in the left-to-right direction, which is not conducive to the transmission of sound from a larger angle range in the upper horizontal direction into the sound acquisition channel 200, affecting the accuracy of sound acquisition.

[0087] In this embodiment, after the sound acquisition element 11 is installed in the receiving slot 21 of the mounting frame 20, an oil-proof and sound-permeable membrane 28 is set at its first sound inlet 211, and a windproof and sound-permeable component 30 is set outside it. A windproof cover 40 is then set outside the windproof and sound-permeable component 30. This sound acquisition device employs the above three layers of protection, which can effectively eliminate wind noise and prevent oil contamination. After the windproof cover 40 covers the windproof and sound-permeable component 30, a second sound inlet 45 is reserved at the leeward end to communicate with the outside. According to the airflow pattern, the flow near the second sound inlet 45 of the windproof and sound-permeable component 30 is a low-speed, high-static-pressure region. The presence of this low-speed, high-static-pressure region reduces wind noise, thereby ensuring that the target noise to be collected (i.e., the noise of the fan system) can be effectively transmitted to the receiving slot 21 of the mounting frame 20 through the second sound inlet 45, ensuring the accuracy of noise data acquisition.

[0088] The sound acquisition device in this embodiment incorporates several wind noise reduction structural designs, including a "turning path" design where the first and second channel segments in the sound propagation channel are arranged at an angle, an extension wall 46 extending in the opening direction of the second sound inlet 45 at the housing 2, and a guide surface 4130 on the windproof cover 40. This design ensures that even when the sound acquisition device is located in an area with relatively high flow velocity within the air duct 10 (such as near the airflow inlet 105 in the first direction), wind noise is minimized, meeting the accuracy requirements for sound acquisition and guaranteeing the comprehensiveness of sound signal acquisition. See details... Figures 10a-12b The graphs show a comparison of the spectrum diagrams for the presence and absence of a turning path design, the presence and absence of an extension wall 46 design, and the presence and absence of a guide ramp design. Specifically, Figure 10a The spectrum diagram of sound acquisition for a sound acquisition device with no bends in the sound propagation path (and no extension walls or guide surfaces). Figure 10b The spectrum of sound acquisition after setting a turning path (but without setting an extension wall and a guide surface) on the sound propagation path of the sound acquisition device. Specifically, "the sound propagation path of the sound acquisition device has no turning design" means that the first channel segment of this embodiment is omitted and only the second channel segment is retained. The sound acquisition element 11 is also correspondingly set in the second channel segment. Figure 11a The spectrum diagram of sound acquisition without extension wall 46 on the windproof cover 40 of the sound acquisition device (a turning path is provided, but no guide surface is provided). Figure 11b The spectrum of sound acquisition after an extension wall 46 (with a turning path but no guide surface) is provided on the windproof cover 40 of the sound acquisition device. Specifically, "the windproof cover 40 of the sound acquisition device does not have an extension wall 46" means that the windproof cover 40 in this embodiment is omitted. Figure 6 The middle section of the extended wall 46, and the top of the wind shield 40 is basically flush with the top of the mounting bracket 20 and the top of the windproof and soundproof component 30. Figure 12a The image shows a spectrum of sound collected when the windshield 40 of the sound acquisition device does not have a guide surface (but has a turning path and an extension wall). Figure 12b The spectrum of sound acquisition after setting a guide surface (with a turning path and extension wall) on the windproof cover 40 of the sound acquisition device. Specifically, "no guide surface on the windproof cover 40" means that the front side wall of the windproof cover 40 is a complete vertical side wall, without a guide surface as shown in the image. Figure 4The guide surface 4130 is shown. In each spectrogram, the red curve represents the sound signal captured by the (front) microphone when active noise cancellation is enabled, and the green curve represents the sound signal captured by the microphone after active noise cancellation is enabled. The horizontal axis represents frequency, and the vertical axis represents the capability amplitude. The first column of RMS (80Hz to 500Hz) in each spectrogram represents the energy in this frequency band; the second column of RMS (1650Hz to 3000Hz) in each spectrogram represents the energy in this frequency band.

[0089] By comparison Figure 10a and Figure 10b The two spectrum diagrams show that, with active noise cancellation enabled and the sound acquisition device configured with a turning path, the noise reduction effect in the 80-500Hz range (especially in the low-frequency band) is more pronounced. Specifically, for example... Figure 10a As shown, the sound acquisition device without a turning path reduced the low-frequency energy by 4.6 dB (i.e., 52.30-47.7; the same applies to other frequency spectrum diagrams), while the reduction was 5.19 dB with a turning path. This indicates that the sound acquisition device with a turning path has a better noise reduction effect on low-frequency noise below 500 Hz. Regarding high-frequency noise reduction, such as... Figure 10a As shown, in the 1650-3000Hz frequency band, the energy of the sound acquisition device without a turning path only decreased by 0.42dB (i.e., 44.26-43.84, and the same applies to other frequency spectrum diagrams), while with a turning path, such as Figure 10b As shown, the energy was reduced by 0.7 dB in the 1650-3000 Hz frequency band, indicating that the sound acquisition device with a turning path also has a better noise reduction effect on high-frequency noise above 1650 Hz. Through the comparison of the above noise reduction effects, it can be reflected that there is a significant difference in the accuracy of sound acquisition at the same acquisition position between the sound acquisition device with and without a turning path. Among them, the sound acquisition device with a turning path has a relatively better wind noise reduction effect. Therefore, when arranged in the air duct 10, the position of the sound acquisition device can be relatively closer to the airflow inlet 105 in the first direction to collect noise signals more comprehensively. Specifically, the distance between the sound acquisition device set near the second side wall 102 and the reference plane is denoted as a1, and a1 and a satisfy the relationship: 0.4≤a1 / a<0.5. When the sound acquisition device is positioned closer to the reference plane, i.e., when a1 / a < 0.4, its noise reduction effect is significantly reduced. This is because the airflow velocity at this location is relatively high, and the resulting wind noise exceeds the wind noise reduction range that the sound acquisition device with this structural design (which has a turning path and no extension wall or guide surface) can achieve.

[0090] By comparison Figure 11a and Figure 11b The two spectrum diagrams show that, with active noise cancellation enabled and the sound acquisition device set to extension wall 46, the noise reduction effect in the 80-500Hz range (especially in the low-frequency band) is more significant. Specifically, for example... Figure 11a As shown, the sound acquisition device without extension wall 46 exhibits a 6.21dB reduction in low-frequency energy, while the device with extension wall 46 shows a 6.52dB reduction. This indicates that the sound acquisition device with extension wall 46 has a better noise reduction effect on low-frequency noise below 500Hz. Regarding high-frequency noise reduction, such as... Figure 11a As shown, in the 1650-3000Hz frequency band, the sound acquisition device without extension wall 46 only experienced a 0.13dB energy reduction, while with extension wall 46 present, the energy reduction was significantly higher. Figure 11b As shown, the energy in the 1650-3000Hz frequency band decreased by 0.84dB, indicating that the sound acquisition device with extension wall 46 has a better noise reduction effect on high-frequency noise above 1650Hz. Through the comparison of the above noise reduction effects, it can be reflected that there is a significant difference in the accuracy of sound acquisition at the same acquisition position with and without extension wall 46. The sound acquisition device with extension wall 46 has a relatively better wind noise reduction effect. Therefore, when arranged within the air duct 10, the location of the sound acquisition device can be further closer to the airflow inlet 105 in the first direction to more comprehensively acquire noise signals. Specifically, when the sound acquisition device is simultaneously set with a turning path and extension wall 46, the distance between the sound acquisition device located near the second side wall 102 and the reference plane is denoted as a1, and a1 and a satisfy the relationship: 0.3≤a1 / a<0.5. When the sound acquisition device is positioned closer to the reference plane, i.e. when a1 / a < 0.3, its noise reduction effect is significantly reduced. This is because the airflow velocity at this location is relatively high, and the resulting wind noise exceeds the wind noise reduction range that the sound acquisition device with this structural design (which has a turning path and an extension wall, but no guide surface) can achieve.

[0091] By comparison Figure 12a and Figure 12b The two spectrum diagrams show that, with active noise cancellation enabled and the sound acquisition device set to a guide surface of 4130°, the noise reduction effect in the 80-500Hz range (especially in the low-frequency band) is more pronounced. Specifically, for example... Figure 10a As shown, the sound acquisition device without the guide surface 4130 exhibits a 5.95dB reduction in low-frequency energy, while the device with the guide surface 4130 shows a 7.17dB reduction. This indicates that the guide surface provides better noise reduction for low frequencies below 500Hz. Regarding high-frequency noise reduction, such as... Figure 12aAs shown, in the 1650-3000Hz frequency band, the sound acquisition device without the guide surface 4130 only experienced a 0.6dB energy reduction, while with the guide surface 4130, such as Figure 12b As shown, the energy was reduced by 1.36 dB in the 1650-3000 Hz frequency band, indicating that the sound acquisition device with the guide surface 4130 has a better noise reduction effect on high-frequency noise above 1650 Hz. Through the comparison of the above noise reduction effects, it can be reflected that there is a significant difference in the accuracy of sound acquisition at the same acquisition position between the sound acquisition device with and without the guide surface 4130. The sound acquisition device with the guide surface 4130 has a relatively better wind noise reduction effect. Therefore, when arranged within the air duct 10, the sound acquisition device can be positioned further closer to the airflow inlet 105 in the first direction to more comprehensively acquire noise signals. Specifically, when the sound acquisition device is simultaneously equipped with a turning path, an extension wall 46, and a guide surface 4130, that is... Figure 6 The distance between the sound acquisition device and the reference plane, which is located near the second side wall 102, is denoted as a1. a1 and a satisfy the relationship: 0.2≤a1 / a<1 / 2. Considering that the sound acquisition device may interfere with other components in the air duct if it is set too close to the reference plane, the preferred value range is: 0.25≤a1 / a<0.35.

[0092] The above Figure 12b The spectrum is obtained by setting the sound acquisition device at a1 / a = 0.2. Figure 13 The sound acquisition device was set at a position a1 / a = 0.5 (specifically, close to 0.5) to measure the spectrum. Figure 14 The spectrum is obtained by setting the sound acquisition device at a position a1 / a = 0.15, where, Figure 13 and Figure 14 The sound acquisition device corresponding to the spectrum diagram and Figure 12b The sound acquisition devices used in all of them have the same structure, namely, they all adopt a sound acquisition device with a turning path design, an extension wall, and a guide surface. Because the sound acquisition device has a turning path, an extension arm structure, and a guide surface, it can achieve a better wind noise reduction effect. This allows the sound acquisition device to be placed further closer to the airflow inlet 105 in the first direction, so as to collect noise signals more comprehensively.

[0093] pass Figure 13 It can be seen that when the location of the sound acquisition device is a1 / a=0.5, the energy in the 80-500Hz frequency band (low frequency band) is reduced by 6.45dB, and the energy in the 1650-3000Hz frequency band is reduced by 0.8dB.

[0094] pass Figure 14 It can be seen that when the location of the sound acquisition device is a1 / a=0.15, the energy in the 80-500Hz frequency band (low frequency band) is reduced by 5.95dB, and the energy in the 1650-3000Hz frequency band is reduced by 0.68dB.

[0095] pass Figure 12b It can be seen that when the location of the sound acquisition device is a1 / a=0.2, the energy in the 80-500Hz frequency band (low frequency band) is reduced by 7.17dB, and the energy in the 1650-3000Hz frequency band is reduced by 1.36dB.

[0096] The comparison of the above spectrum diagrams shows that when the sound acquisition device is located outside the interval [0.2, 0.5), its active noise reduction effect in both the low and high frequency bands is not ideal. This is likely because the airflow velocity at this location is relatively high, and the resulting wind noise exceeds the wind noise reduction range that the sound acquisition device (which has a turning path, extension wall, and guide surface) can achieve. However, when the sound acquisition device is located within the interval [0.2, 0.5), it can basically cancel or eliminate the wind noise effect within this interval. Thus, the closer the sound acquisition device is to the airflow inlet (or the reference plane), the more comprehensive the sound acquisition, and therefore, the better the active noise reduction effect.

Claims

1. A mounting structure of an active noise reduction system of an oil fume suction device, the active noise reduction system comprising a sound collecting device arranged in an air duct (10) of the oil fume suction device, characterized in that: The air duct (10) has a first sidewall (101) and a second sidewall (102) opposite each other in a first direction and an air inlet (105) for airflow to enter the air duct (10). The first direction is perpendicular to the extension direction of the air duct (10). The air inlet (105) is disposed adjacent to the first sidewall (101). At least one sound acquisition device is disposed adjacent to the second sidewall (102). The sound acquisition device includes a housing (2) and a sound acquisition element (11). The housing (2) defines a sound propagation channel. The sound propagation channel includes a first channel segment and a second channel segment that are connected in sequence and arranged at an angle. The sound acquisition element (11) is located in the first channel segment. The housing (2) also has a second sound inlet (45) for sound in the air duct (10) to enter the second channel segment.

2. The mounting structure of an active noise reduction system of an oil fume extraction device according to claim 1, characterized in that: A fan (90) is also provided inside the duct (10) of the fume extraction device or at the port of the duct (10). The fan (90) includes a volute (91) and an impeller (92) disposed inside the volute (91). The axis of the impeller (92) extends vertically. The center position of the airflow inlet (105) is denoted as point F1. The center position of the bottom port of the impeller (92) through the axis of the impeller (92) is denoted as point F2. The line connecting point F1 and point F2 is denoted as line F2. Segment F1F2, the sound acquisition device (1) is located in the area between segment F1F2 and the second side wall (102) in the air duct (10), the shortest distance between segment F1F2 and the second side wall (102) in the first direction is denoted as S1, the distance between the first side wall (101) and the second side wall (102) of the air duct (10) is a, and the value range of S1 / a satisfies the following condition: S1 / a≥1 / 10.

3. The mounting structure of an active noise reduction system of an oil fume extraction device according to claim 1, characterized in that: A fan (90) is also provided inside the duct (10) of the fume extraction device or at the port of the duct (10). The fan (90) includes a volute (91) and an impeller (92) disposed inside the volute (91). The volute (91) includes an annular wall (911) and cover plates (912) connected to the axial ends of the annular wall (911). The axis of the impeller (92) extends horizontally. The center position of the airflow inlet (105) is denoted as point F1, and the center position of the bottom of the annular wall (911) in its width direction is denoted as point F2. Point F3 is drawn, and the line connecting point F1 and point F3 is denoted as line segment F1F3. The sound acquisition device (1) is located in the area between line segment F1F2 and the second side wall (102) within the air duct (10). The shortest distance between line segment F1F3 and the second side wall (102) in the first direction is denoted as S2. The distance between the first side wall (101) and the second side wall (102) of the air duct (10) is a. The value range of S2 / a satisfies the following condition: S2 / a≥1 / 10.

4. The mounting structure of an active noise reduction system of a cooking fume extractor according to claim 1, characterized in that: The distance between the first sidewall (101) and the second sidewall (102) of the air duct (10) is a, and the distance between the sound acquisition device and the second sidewall (102) is denoted as L1. The relationship between L1 and a is: 0 < L1 / a < 0.

3.

5. The mounting structure of an active noise reduction system of a cooking fume device according to claim 4, characterized in that: The distance between the side of the airflow inlet (105) adjacent to the first sidewall (101) and the first sidewall (101) in the first direction is denoted as c, and the value of c is in the range of 0 < c < 50 mm. The dimension of the airflow inlet (105) in the first direction is denoted as c1, where c1, a, and L1 satisfy the following conditions: 0.05 < L1 / a < 0.3, when 1 / 5 < c1 / a < 1 / 3; 0.05 < L1 / a < 0.25, when 1 / 3 ≤ c1 / a < 2 / 3. 6.The installation structure of the active noise reduction system of the cooking fume device according to claim 1, characterized in that: The opening of the airflow inlet (105) is oriented in the same direction as the extension direction of the air duct (10).

7. The mounting structure of an active noise reduction system of a cooking fume device according to claim 1, characterized in that: The air duct (10) is provided with a crossbeam (106) arranged in a direction parallel to the first side wall (101), and the sound acquisition device is located on the crossbeam (106).

8. The mounting structure of the active noise reduction system of the cooking fume device according to any one of claims 1 to 7, characterized in that: The air duct (10) has a third sidewall (103) and a fourth sidewall (104) opposite each other in the second direction. The second direction is perpendicular to the first direction and the extension direction of the air duct (10). The distance between the third sidewall (103) and the fourth sidewall (104) is denoted as b. There is a sound acquisition device installed near the first sidewall (101). The distance between the sound acquisition device and the third sidewall (103) is denoted as b1, and the distance between the sound acquisition device and the fourth sidewall (104) is denoted as b2. b1, b3 and b satisfy the following conditions: 1 / 5≤b1 / b≤1 / 2; 1 / 5≤b2 / b≤1 / 2.

9. The mounting structure of an active noise reduction system of an extractor hood according to any one of claims 1 to 7, characterized in that: The air duct (10) has a third sidewall (103) and a fourth sidewall (104) opposite each other in the second direction. The second direction is perpendicular to the first direction and the extension direction of the air duct (10). The distance between the third sidewall (103) and the fourth sidewall (104) is denoted as b. At least two sound acquisition devices are arranged adjacent to the first sidewall (101). Each sound acquisition device is arranged sequentially at intervals along the second direction. The distance between the sound acquisition device adjacent to the third sidewall (103) and the third sidewall (103) is denoted as b1'. The distance between the sound acquisition device adjacent to the fourth sidewall (104) and the fourth sidewall (104) is denoted as b2'. b, b1' and b2' satisfy the following conditions: 1 / 6≤b1' / b≤2 / 5; 1 / 6≤b2' / b≤2 / 5.

10. The mounting structure of the active noise reduction system of the cooking fume device according to any one of claims 1 to 7, characterized in that: A sound acquisition device is also provided in the air duct (10) near the first side wall (101). The sound acquisition device near the first side wall (101) is referred to as the first sound acquisition device, and the sound acquisition device near the second side wall (102) is referred to as the second sound acquisition device. The number of the first sound acquisition devices is greater than or equal to the number of the second sound acquisition devices.

11. The mounting structure of an active noise reduction system of an extractor hood according to any one of claims 1 to 7, characterized in that: The extension direction of the second channel segment is consistent with the extension direction of the air duct (10). The second sound inlet (45) is located on the leeward side of the housing (2). The opening direction of the second sound inlet (45) is consistent with the extension direction of the air duct (10).

12. The mounting structure of an active noise reduction system of a cooking fume device according to claim 11, characterized in that: The extension direction of the first channel segment is perpendicular to the extension direction of the second channel segment.

13. The mounting structure of an active noise reduction system of a cooking fume device according to claim 10, characterized in that: The plane formed by the points at the middle position of the air duct (10) in the first direction and along the extension direction of the air duct (10) is used as the reference plane. The distance between the sound acquisition device installed near the second side wall (102) and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.4≤a1 / a<0.

5.

14. The mounting structure of an active noise reduction system of a cooking fume device according to claim 10, characterized in that: The housing also has an extension wall (46) at the second sound inlet (45) that extends in the opening direction of the second sound inlet (45).

15. The mounting structure of an active noise reduction system of a cooking fume device according to claim 14, characterized in that: The plane formed by the points at the middle position of the air duct (10) in the first direction and along the extension direction of the air duct (10) is used as the reference plane. The distance between the sound acquisition device installed near the second side wall (102) and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.3≤a1 / a<0.

5.

16. The installation structure of the active noise reduction system of the fume extraction device according to claim 14, characterized in that: The housing includes a mounting bracket (20) and a windproof cover (40). A receiving groove (21) is provided on the front side wall of the mounting bracket (20). The sound acquisition element (11) is placed in the receiving groove (21). The receiving groove (21) constitutes the first channel segment. The windproof cover (40) covers the mounting bracket (20) and defines a sound acquisition channel (200) that communicates with the receiving groove (21) and is located in front of the receiving groove (21). The sound acquisition channel (200) constitutes the second channel segment. The windproof cover (40) defines the second sound inlet (45) with the mounting bracket (20) at the leeward end. An extension wall (46) is formed at the second sound inlet (45) extending along the opening direction of the second sound inlet (45).

17. The mounting structure of an active noise reduction system of a cooking fume hood according to claim 16, wherein: The windproof cover (40) has a guide surface (4130) at the windward end that gradually slopes towards the inside of the airflow channel (10) along the direction of airflow. The angle formed between the guide surface (4130) and the extension direction of the airflow channel (10) is denoted as A, and the value of A is in the range of A≤60°.

18. The mounting structure of an active noise reduction system of a cooking fume hood according to claim 17, characterized in that: The plane formed by the points at the middle position of the air duct (10) in the first direction and the extension direction of the air duct (10) is used as the reference plane. The distance between the sound acquisition device installed near the second side wall (102) and the reference plane is denoted as a1. a1 and a satisfy the relationship: 0.2≤a1 / a<0.

5.

19. The mounting structure of an active noise reduction system of a cooking fume device according to claim 10, characterized in that: The second channel section is also equipped with a windproof and sound-permeable component (30).

20. The mounting structure of an active noise reduction system of a cooking fume device according to claim 10, characterized in that: The first channel section is also equipped with an oil-proof and sound-permeable membrane (28).

21. A range hood, comprising a duct (10) and an active noise reduction system, wherein the active noise reduction system comprises a sound acquisition device, a speaker, and a controller, wherein the controller receives noise signals from the sound acquisition device and generates noise reduction signals, which are then transmitted to the speaker to emit noise reduction waves, wherein the sound acquisition device and the speaker are both disposed within the duct (10) of the range hood, characterized in that: It also includes the installation structure of the active noise reduction system of the fume extraction device according to any one of claims 1 to 20.

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