Noise reduction device for range hood and range hood

Abstract

The invention relates to a noise reduction device for a range hood and the range hood, the range hood comprises a shell, and the noise reduction device comprises a sound absorption part arranged in the shell; a piezoelectric regulation and control layer made of piezoelectric materials is further arranged on at least one side, facing the interior of the machine shell, of the sound absorption piece, and the piezoelectric regulation and control layer is configured to adjust the surface vibration frequency of the piezoelectric regulation and control layer through the inverse piezoelectric effect according to the frequency and intensity of incident sound waves, receive external voltage signals and generate vibration. Therefore, the acoustic impedance of the surface of the sound absorption part is adjusted to reduce sound wave reflection. The method has the advantages that the surface acoustic impedance problem of the sound absorption part can be effectively improved, the sound absorption and noise reduction efficiency is improved, and then the thickness requirement of a traditional sound absorption material is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of range hoods, and in particular to a noise reduction device for a range hood and the range hood. Background Art

[0002] Range hoods are kitchen appliances that purify the kitchen environment. Range hood noise reduction primarily relies on passive methods, with absorption, muffling, and insulation being the most widely used. Traditional sound insulation and absorption materials vary widely, including wool felt, polyester fiber, foam, and bicomponent fiber, with varying performance. Some newer materials also offer excellent sound absorption. Existing range hoods typically incorporate sound-absorbing foam within the fan housing (the upper housing housing the fan system), primarily around the fan housing and around the volute. However, conventional sound-absorbing materials, particularly those made of polyurethane and fiber, require a relatively thick thickness to achieve effective sound absorption and insulation. Current range hoods primarily utilize bicomponent fiber materials (such as PP+PET) and require a certain thickness, typically at least 2 cm. This compresses the flow path within the range hood, impacting air extraction efficiency (a 10%-15% decrease in air volume). Another issue that shouldn't be overlooked is the high acoustic impedance of existing two-component materials (PP + PET sound-absorbing cotton). This prevents much sound from being absorbed and instead causes significant reflection, which compromises the sound absorption effect. In particular, the thickness of the sound-absorbing material can lead to the accumulation of oil, which can penetrate the pores of the sound-absorbing layer (to a depth of 3-5mm), causing the sound absorption coefficient to decrease by over 40%, resulting in a decrease in the noise reduction effect. The thicker the sound-absorbing material becomes due to oil contamination, the more acoustic impedance problem is exacerbated. Much of the sound is reflected back rather than entering the material, resulting in a decrease in the actual sound absorption effect.

[0003] Therefore, the noise reduction device used in the existing range hood needs to be further improved. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a noise reduction device for range hoods that can effectively improve the surface acoustic impedance problem of the sound-absorbing component, enhance the sound absorption and noise reduction efficiency, and thereby reduce the thickness requirement of traditional sound-absorbing materials, based on the current status of the existing technology.

[0005] The second technical problem to be solved by the present invention is to provide a range hood with the above-mentioned noise reduction device in view of the current status of the existing technology.

[0006] The technical solution adopted by the present invention to solve the first technical problem is: a noise reduction device for a range hood, the range hood including a housing, including:

[0007] a sound absorbing member, arranged in the housing;

[0008] A piezoelectric control layer made of piezoelectric material is also provided on at least one side of the sound absorbing member facing the inside of the casing. The piezoelectric control layer is configured to adjust the surface vibration frequency of the piezoelectric control layer through the inverse piezoelectric effect according to the frequency and intensity of the incident sound wave, and receive an external voltage signal and generate vibration, thereby adjusting the acoustic impedance of the surface of the sound absorbing member to reduce sound wave reflection.

[0009] The aforementioned “reverse voltage effect” refers to the phenomenon that piezoelectric materials deform under the action of an electric field.

[0010] The above-mentioned "acoustic impedance" can be understood as the resistance encountered by sound waves when propagating on the surface of the medium.

[0011] As an improvement, the sound absorbing member is a fiber layer made of a bicomponent fiber material;

[0012] The piezoelectric control layer is a piezoelectric film covering the fiber layer; or

[0013] The piezoelectric control layer includes a plurality of thin film units covering the fiber layer and arranged in a matrix.

[0014] Using piezoelectric film to cover the surface improves the uniformity of vibration. Similarly, alternatively, using thin film matrix units can also achieve precise control of the partitions and broaden the noise reduction band.

[0015] In order to adapt to the noise in the operating environment of the range hood, as an improvement, the operating voltage of the piezoelectric control layer is 0-100V, and the vibration frequency response range is 10-1000Hz.

[0016] The piezoelectric film may be an organic piezoelectric polymer film or a piezoelectric composite material film. As an improvement, the piezoelectric film is a flexible PVDF piezoelectric film.

[0017] The flexibility of PVDF can adapt to the uneven curved structure inside the casing; on the other hand, it is also resistant to oil and corrosion, extending the service life.

[0018] In order to achieve multi-band coordinated noise reduction, the sound absorbing component includes a first fiber layer and a second fiber layer arranged in sequence, the first fiber layer is close to the piezoelectric control layer relative to the second fiber layer, the second fiber layer has a first side facing the first fiber layer and a second side away from the above-mentioned first fiber layer, and a plurality of gradient perforated structures are distributed on the second fiber layer, each of the gradient perforated structures is constructed as follows: at least two noise reduction holes are arranged in sequence from the first side to the second side of the second fiber layer, of the two adjacent noise reduction holes, the one adjacent to the first side of the second fiber layer is recorded as the first noise reduction hole, and the one away from the first side of the second fiber layer is recorded as the second noise reduction hole, the opening area of ​​the first noise reduction hole is larger than that of the second noise reduction hole, and the depth of the first noise reduction hole is greater than that of the second noise reduction hole.

[0019] The above-mentioned “gradient perforated structure” can be understood as an array of holes on the fiber layer whose pore size / depth changes according to a specific rule, thereby achieving broadband sound absorption.

[0020] This structural design creates a honeycomb-like wall structure, which absorbs low-frequency noise through the gradient micro-perforated resonant structure of the sound-absorbing layer. The stepped micro-perforation design achieves a multi-mechanism coupling of Helmholtz resonance, plate resonance, and viscous friction. Combined with fractal impedance gradients and phase interference, it achieves highly effective noise reduction in the low-frequency range of 100-500Hz. Furthermore, the two-component material itself achieves a sound absorption coefficient exceeding 0.9 in the mid- and high-frequency ranges. Furthermore, the active vibration of the piezoelectric material generates reverse sound waves, effectively canceling out incident sound waves.

[0021] According to the Helmholtz resonance formula (S is the hole area, V is the cavity volume, and L is the effective hole length). Large-aperture noise reduction holes (such as 6mm) correspond to lower resonant frequencies (approximately 100-300Hz), converting low-frequency sound energy into heat energy through air column vibration. For noise reduction holes with smaller openings (such as 6mm), the plate resonance effect in the mid-frequency band (200-500Hz) dominates, and the honeycomb wall vibration couples with the secondary holes, broadening the sound absorption bandwidth. Microporous structures with relatively small openings can target high-frequency noise (above 500Hz) by dissipating sound energy through air viscous friction. The boundary layer effect on the microporous surface is significant, increasing the acoustic resistance.

[0022] As an improvement, the noise reduction holes of each gradient perforated structure of the second fiber layer are polygonal holes and / or circular holes arranged in a nested manner.

[0023] As a further improvement, the smallest noise reduction hole among the noise reduction holes of each gradient perforated structure of the second fiber layer is a circular hole, and the remaining noise reduction holes are regular hexagonal holes.

[0024] In order to further improve the sound absorption and noise reduction effect, each of the gradient perforated structures on the second fiber layer is covered by the first fiber layer to form a corresponding Helmholtz resonance cavity.

[0025] The above-mentioned "Helmholtz resonance chamber" can be understood as an acoustic structure consisting of a cavity and a narrow neck. When the sound wave frequency is equal to its resonance frequency, the air column at the neck vibrates violently and consumes sound energy.

[0026] As an improvement, the sound-absorbing component is a sound-absorbing cotton formed by a composite of PP material and PET material.

[0027] As an improvement, the surface of the PET material of the sound-absorbing component is sprayed with a graphene conductive coating, and the microvoltage generated by the vibration of the piezoelectric control layer can be transmitted to the graphene conductive coating to absorb oil smoke particles.

[0028] The surface of the PP+PET two-component noise reduction material PET is sprayed with graphene conductive material, so that the microvoltage generated by the vibration of the piezoelectric control layer material is transmitted to the graphene PET, which can further absorb oil fume particles.

[0029] As an improvement, the sound-absorbing component is further provided with a nanofiber filter layer for blocking oil smoke on the outside of the piezoelectric control layer. The nanofiber filter layer is combined with the piezoelectric material to form a sandwich structure of nanofiber layer + piezoelectric control layer + sound-absorbing layer. The nanofiber layer is located on the outermost side and directly contacts the oil smoke, intercepting the oil smoke, which can protect the piezoelectric control layer and the sound-absorbing layer and reduce the pollution of oil. The high-frequency vibration of the piezoelectric control layer material can make the oil droplets attached to the nanofiber filter layer detach from the surface to prevent clogging of the pores. In addition, the electrical energy generated by the vibration of the piezoelectric material of the piezoelectric control layer can drive a small electrostatic dust collection module to further absorb the escaped tiny oil droplets.

[0030] In order to improve the antifouling performance and facilitate cleaning, the nanofiber filter layer is a PVDF / PAN / PU composite nanofiber membrane with a fiber diameter of 100-500nm and a surface contact angle greater than 150°.

[0031] The technical solution adopted by the present invention to solve the second technical problem is: a range hood, including a casing and a noise reduction device arranged in the casing, the noise reduction device adopts the above-mentioned noise reduction device for range hoods, and the noise reduction device is arranged on the inner wall of the casing.

[0032] Compared with the existing technology, the advantages of the present invention are as follows: the noise reduction device of the present invention is provided with a piezoelectric control layer on the side of the sound-absorbing component. This piezoelectric control layer can actively adjust the surface vibration frequency through the inverse piezoelectric effect, dynamically matching the characteristics (frequency / intensity) of the incident sound wave, significantly reducing sound wave reflection (the sound wave reflectivity can be reduced from 30% to 8%). Through active vibration, the acoustic impedance is closely matched with the air medium, guiding the sound waves to efficiently enter the interior of the sound-absorbing layer, greatly improving the sound absorption efficiency. Based on this, this solution optimizes the sound energy transmission path through the control layer, allowing the sound-absorbing component to achieve the same noise reduction with a relatively small thickness. In turn, the internal flow channel space of the range hood casing is freed up, directly improving the air volume efficiency and solving the problem of air volume attenuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the three-dimensional structure of the noise reduction device according to an embodiment of the present invention;

[0034] Figure 2 is an exploded view of a noise reduction device according to an embodiment of the present invention;

[0035] Figure 3 is a sectional perspective view of a noise reduction device according to an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the three-dimensional structure of the range hood according to an embodiment of the present invention without the fume collecting hood. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0038] In the present specification and claims, directional terms such as "front," "back," "up," "down," "left," "right," "side," "top," and "bottom" are used to describe various exemplary structural parts and components of the present invention. However, these terms are used herein for convenience of description only and are based on the exemplary orientations shown in the accompanying drawings. Because the embodiments disclosed herein can be arranged in various orientations, these directional terms are intended for illustrative purposes only and should not be construed as limiting. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0039] Figures 1-4A preferred embodiment of the noise reduction device for a range hood and a range hood according to the present invention is shown. The range hood comprises a housing 10 and a fan system 11 disposed within the housing 10. Fan system 11 is typically a centrifugal fan, comprising a volute 111 and an impeller 112 rotating within the volute 111. The housing 10 generally comprises a fan frame and a fume hood disposed at the bottom of the fan frame. The interior of the fan frame communicates with the interior of the fume hood. An air inlet is defined on the front sidewall of the fume hood, allowing external fumes to enter the hood. The centrifugal fan is housed within the fan frame. When the centrifugal fan operates, it generates negative pressure, drawing external fumes into the hood through the air inlet. An oil screen is also provided at the air inlet of the fume hood to filter the fumes. An oil cup is provided at the bottom of the fume hood. The cup is a long, strip-shaped oil cup extending from side to side to collect grease that flows down from the fume hood. The front of the smoke hood is also equipped with a smoke shield that can be deflected forward and backward relative to the smoke hood. The smoke shield is connected to the main body of the smoke hood via a hinge mechanism. Specifically, the smoke shield can be deflected forward to open the aforementioned air inlet and deflected backward to block and close the aforementioned air inlet. The hinge mechanism for driving the deflection of the smoke shield can adopt a conventional hinge mechanism in the prior art and will not be described in detail here.

[0040] See also Figure 4 A noise reduction device 2 is provided on the inner side wall of the fan rack. The noise reduction device 2 faces the air inlet of the fan system 11 in the fan rack. The noise reduction device includes a sound absorbing member 20 and a piezoelectric control layer 31 arranged on the outer side of the sound absorbing member 20.

[0041] See also Figure 2 and Figure 3The sound-absorbing member 20 of this embodiment is a fiber layer made of a bicomponent fiber material, including a sound-absorbing cotton made of PP+PET bicomponent fibers. It comprises a first fiber layer 21 and a second fiber layer 22. The first fiber layer 2130 has a thickness ranging from 8 to 15 mm, preferably 10 mm, and directly contacts the piezoelectric control layer 31. The second fiber layer 2240 has a thickness ranging from 2 to 8 mm, preferably 5 mm, and is arranged on the side of the first fiber layer 21 away from the side closest to the first fiber layer 21. More specifically, the second fiber layer 22 has a first side facing the first fiber layer 21 and a second side facing away from the first fiber layer 21. A plurality of gradient perforated structures 200 are distributed on the second fiber layer 22. Each gradient perforated structure 200 is constructed as follows: at least two noise reduction holes are sequentially arranged from the first side to the second side of the second fiber layer 22. Of the two adjacent noise reduction holes, the one adjacent to the first side of the second fiber layer 22 is denoted as the first noise reduction hole 201, and the one away from the first side of the second fiber layer 22 is denoted as the second noise reduction hole 202. The opening area of ​​the first noise reduction hole 201 is larger than that of the second noise reduction hole 202, and the depth of the first noise reduction hole 201 is greater than that of the second noise reduction hole 202. After the first fiber layer 21 completely covers the second fiber layer 22, a closed Helmholtz resonance cavity is formed at the contact point of the corresponding gradient perforations.

[0042] The noise reduction holes of each gradient perforated structure 200 of the second fiber layer 22 are nested polygonal holes and / or circular holes, similar to a honeycomb hole structure. In a preferred embodiment, the smallest noise reduction hole among the noise reduction holes of each gradient perforated structure 200 of the second fiber layer 22 is a circular hole, and the remaining noise reduction holes are regular hexagonal holes. Figure 3 The diagram shows three nested noise reduction holes, namely the outer noise reduction hole 200a, the middle noise reduction hole 200b and the inner noise reduction hole 200c. The three noise reduction holes are all hexagonal holes. Among them, the outer noise reduction hole 200a is a regular hexagonal hole with a side length of 6mm and a hole depth of 0.5mm. According to the Helmholtz resonance formula (S is the hole area, V is the cavity volume, and L is the effective hole length). The large aperture (6mm) corresponds to a lower resonant frequency (100-300Hz), and can convert low-frequency sound energy into heat energy through air column vibration. The middle-layer noise reduction hole 200b is also a regular hexagonal hole with a side length of 3mm and a hole depth of 1.0mm. The plate resonance effect in the mid-frequency band (200-500Hz) and the honeycomb wall vibration are coupled with the middle hole to broaden the sound absorption bandwidth. The inner-layer noise reduction hole 200c is a circular hole with a diameter of 1mm and a hole depth of 1.6mm. It can reduce noise in the high-frequency band (above 500Hz) and dissipate sound energy through air viscous friction, making the boundary layer effect on the microporous surface significant and increasing the acoustic resistance.

[0043] The piezoelectric control layer 31 is made of piezoelectric material and is arranged on at least one side of the sound absorbing member 20 facing the inside of the housing 10. The piezoelectric control layer 31 can be a piezoelectric film covered on the fiber layer, such as Figure 2 The piezoelectric control layer 31 shown in the figure is made of a piezoelectric film, and the piezoelectric film is used to cover and improve the surface vibration uniformity. The piezoelectric control layer 31 of this embodiment is configured to: adjust the surface vibration frequency of the piezoelectric control layer 31 through the inverse piezoelectric effect according to the frequency and intensity of the incident sound wave, and receive an external voltage signal and generate vibration, thereby adjusting the acoustic impedance of the surface of the sound absorbing member 20 to reduce the reflection of the sound wave. Among them, the "inverse voltage effect" refers to the phenomenon that the piezoelectric material deforms under the action of an electric field. The "acoustic impedance" of the sound absorbing member 20 can be understood as the resistance encountered by the sound wave when it propagates on the surface of the medium. When the sound wave acts on the surface of the piezoelectric material, the piezoelectric material generates an electric charge due to mechanical stress, and the amplitude of the charge is proportional to the intensity of the sound wave (sound pressure), and the frequency of the charge change corresponds to the frequency of the sound wave. Based on this, the frequency and intensity of the incident sound wave are obtained.

[0044] The piezoelectric control layer 31 of this embodiment can adopt a 0.2mm thick flexible PVDF piezoelectric film, which is closely attached to the outside of the first fiber layer 21 of the sound-absorbing component 20 and covers most of the total surface of the sound-absorbing component 20. The electrode connection end of the piezoelectric control layer 31 is connected to the voltage regulation module of the range hood control system. The operating voltage range is 0-100V. By applying a 0-100V voltage, the PVDF piezoelectric film generates 10-1000Hz mechanical vibration, so that the surface impedance of the piezoelectric material matches the air medium, effectively reducing the reflection of sound waves.

[0045] The noise reduction device also includes a nanofiber filter layer 41 located outside the piezoelectric control layer 31, thereby forming a three-layer composite structure with the piezoelectric control layer 31 and the sound-absorbing element 20. The nanofiber filter layer 41 is a nanofiber membrane made of PVDF / PAN / PU composite nanofibers, which can be specifically prepared using an electrospinning process. The fiber diameter of the nanofiber filter layer 41 is 300nm, and the surface contact angle is 152°, forming a super-oleophobic surface. The nanofiber membrane can effectively intercept the oil smoke inside the range hood from entering the sound-absorbing element 20 due to its nanometer-scale fiber diameter and high specific surface area. At the same time, the vibration of the piezoelectric material actively removes surface oil stains, achieving a self-cleaning function. The energy generated by the vibration of the piezoelectric control layer 31 can cause the surface of the two-component material of the sound-absorbing layer to have micro-static electricity, further intercepting the oil smoke. In other words, the electrical energy generated by the vibration of the piezoelectric material can drive a small electrostatic dust collection module to further absorb the escaping tiny oil droplets, achieving the purpose of blocking the oil droplets through physical interception and electrostatic adsorption.

[0046] The surface of the PET material of the sound absorbing element 20 of this embodiment is sprayed with a graphene conductive coating. The microvoltage generated by the vibration of the piezoelectric control layer 31 can be transmitted to the graphene conductive coating to absorb oil smoke particles.

[0047] The noise reduction device of this embodiment features a piezoelectric control layer 31 on the side of the sound-absorbing element 20. This piezoelectric control layer 31 actively adjusts the surface vibration frequency through the inverse piezoelectric effect, dynamically matching the characteristics (frequency / intensity) of the incident sound wave, significantly reducing sound wave reflection (reflectivity can be reduced from 30% to 8%). Active vibration closely matches the acoustic impedance of the air medium, effectively guiding sound waves into the sound-absorbing layer, significantly improving sound absorption efficiency. Based on this, this solution optimizes the sound energy transmission path through the control layer, allowing the sound-absorbing element 20 to achieve equivalent noise reduction with a relatively small thickness. This, in turn, frees up space within the range hood casing 10, directly improving airflow efficiency and addressing the problem of airflow attenuation. To address the limited frequency coverage of conventional sound-absorbing materials, particularly the poor sound absorption performance in the low-frequency range below 500 Hz, this embodiment leverages the active tuning capabilities of piezoelectric materials combined with the passive absorption properties of the two-component material of the sound-absorbing element 20 to achieve wide-band noise control (100 Hz-5 kHz). Specifically, the gradient perforation structure 200 of the second fiber layer 22 of the sound-absorbing element 20 mimics natural fractal structures (such as pine cones and honeycombs). The apertures of the noise-reduction holes, which progress from 6mm to 3mm to 1mm, form a self-similar nesting pattern, stimulating multiple resonant modes and enhancing low-frequency noise reduction. Furthermore, the increasing depth of the holes (0.5mm for the outer layer, 1.0mm for the middle layer, and 1.6mm for the inner layer) creates a gradual change in acoustic impedance according to (approximately) the Fibonacci ratio (0.5→1→1.6), further reducing reflection losses.

[0048] Based on the above embodiments, other embodiments can be obtained by replacing and improving the relevant technical features. The piezoelectric control layer 31 can also be replaced by a structure including multiple thin film units covered on the fiber layer and arranged in a matrix. For example, the piezoelectric control layer 31 is composed of a matrix of multiple (greater than 100) independently controlled 3cm×3cm PVDF thin film units, each of which is connected to an independent voltage controller. In this way, the noise spectrum of different areas in the housing 10 can be controlled in different zones.

Claims

1. A noise reduction device for a range hood, the range hood comprising a housing (10), comprising: A sound absorbing member (20) is arranged in the housing (10); The invention is characterized in that: a piezoelectric control layer (31) composed of a piezoelectric material is further provided on at least one side of the sound absorbing member (20) facing the inside of the housing (10); the piezoelectric control layer (31) is configured to: adjust the surface vibration frequency of the piezoelectric control layer (31) through the inverse piezoelectric effect according to the frequency and intensity of the incident sound wave, receive an external voltage signal and generate vibration, thereby adjusting the acoustic impedance of the surface of the sound absorbing member (20) to reduce sound wave reflection.

2. The noise reduction device for a range hood according to claim 1, characterized in that: The sound absorbing member (20) is a fiber layer made of a bicomponent fiber material; The piezoelectric control layer (31) is a piezoelectric film covering the sound absorbing element; or The piezoelectric control layer (31) comprises a plurality of thin film units covering the fiber layer and arranged in a matrix.

3. The noise reduction device for a range hood according to claim 2, characterized in that: The operating voltage of the piezoelectric control layer (31) is 0-100V, and the vibration frequency response range is 10-1000Hz.

4. The noise reduction device for a range hood according to claim 2, characterized in that: The piezoelectric film is a flexible PVDF piezoelectric film.

5. The noise reduction device for a range hood according to claim 2, characterized in that: The sound absorbing member (20) comprises a first fiber layer (21) and a second fiber layer (22) which are arranged in sequence, wherein the first fiber layer (21) is close to the piezoelectric control layer (31) relative to the second fiber layer (22), and the second fiber layer (22) has a first side facing the first fiber layer (21) and a second side facing away from the first fiber layer (21), and a plurality of gradient perforated structures (200) are distributed on the second fiber layer (22), and each of the gradient perforated structures (200) is constructed as follows: at least two noise reduction holes are arranged in sequence from the first side to the second side of the second fiber layer (22), and one of the two adjacent noise reduction holes adjacent to the first side of the second fiber layer (22) is recorded as the first noise reduction hole (201), and the other away from the first side of the second fiber layer (22) is recorded as the second noise reduction hole (202), the opening area of ​​the first noise reduction hole (201) is larger than that of the second noise reduction hole (202), and the depth of the first noise reduction hole (201) is larger than that of the second noise reduction hole (202).

6. The noise reduction device for a range hood according to claim 5, characterized in that: The noise reduction holes of each gradient perforated structure (200) of the second fiber layer (22) are polygonal holes and / or circular holes arranged in a nested manner.

7. The noise reduction device for a range hood according to claim 6, characterized in that: The smallest noise reduction hole among the noise reduction holes of each gradient perforated structure (200) of the second fiber layer (22) is a circular hole, and the remaining noise reduction holes are regular hexagonal holes.

8. The noise reduction device for a range hood according to claim 6, characterized in that: Each of the gradient perforated structures (200) on the second fiber layer (22) is covered by the first fiber layer (21) to form a corresponding Helmholtz resonance cavity.

9. The noise reduction device for a range hood according to any one of claims 2 to 8, characterized in that: The sound absorbing member (20) is a sound absorbing cotton formed by combining PP material and PET material.

10. The noise reduction device for a range hood according to claim 9, characterized in that: The surface of the PET material of the sound absorbing element (20) is sprayed with a graphene conductive coating, and the microvoltage generated by the vibration of the piezoelectric control layer (31) can be transmitted to the graphene conductive coating to absorb oil smoke particles.

11. The noise reduction device for a range hood according to any one of claims 2 to 8, characterized in that: The sound absorbing member (20) is further provided with a nanofiber filter layer (41) for blocking oil smoke on the outer side of the piezoelectric control layer (31).

12. The noise reduction device for a range hood according to claim 11, characterized in that: The nanofiber filter layer (41) is a PVDF / PAN / PU composite nanofiber membrane, the composite nanofiber membrane has a fiber diameter of 100-500 nm and a surface contact angle greater than 150°.

13. A range hood comprising a housing (10) and a noise reduction device disposed in the housing (10), characterized in that: The noise reduction device adopts the noise reduction device for a range hood according to any one of claims 1 to 12, and the noise reduction device is arranged on the inner side wall of the housing (10).

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