A low-noise ventilation box noise reduction system

Abstract

The present invention discloses a low-noise ventilation box noise reduction system, comprising an air inlet silencer box, a centrifugal wind wheel box and an exhaust box which are integrally arranged, wherein the air inlet silencer box, the centrifugal wind wheel box and the exhaust box are respectively provided with a longitudinal air inlet bin, a wind wheel bin and an exhaust bin; a centrifugal wind wheel with a horizontal axis is rotatably arranged in the wind wheel bin, the centrifugal wind wheel is synchronously mounted on a rotating shaft, and an external motor drive is connected to the rotating shaft; the sound waves generated by the centrifugal wind wheel of the present invention are projected along the axial direction to the outer cone surface of a conical sound-absorbing wind guide wall, and the outer cone surface of the conical sound-absorbing wind guide wall will absorb a part of the sound waves, thereby achieving the effect of noise reduction.

Description

Technical Field

[0001] The invention belongs to the field of bellows noise reduction. Background Art

[0002] The external fan ventilation box is an essential component of YKK box-type motors. External cooling air is pumped by the external fan and flows smoothly through the ventilation box's connection to the cooler. The old ventilation box had a simple structure, with the external fan exposed, resulting in high noise levels. However, as customers are increasingly demanding on noise levels, the improved ventilation box eliminates the external fan exposure, effectively reducing overall motor noise.

[0003] The old ventilation box structure is as follows Figure 1 As shown: the ventilation mesh is installed at the bottom of the ventilation box, close to the external fan. The external cooling air enters the external fan through the ventilation mesh, and enters the upper cooler after being stirred by the external fan. The disadvantage of this structure is that since there are air inlet holes on the ventilation mesh, the external fan is basically exposed to the outside, and the noise measurement point is 1 meter outside the ventilation mesh, so the noise is relatively large. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a low-noise ventilation box noise reduction system that can effectively reduce the noise of centrifugal fans and bellows.

[0005] Technical solution: To achieve the above-mentioned purpose, the present invention provides a low-noise ventilation box noise reduction system, comprising an integrated air intake silencer box, a centrifugal wind wheel box and an exhaust box, wherein the air intake silencer box, the centrifugal wind wheel box and the exhaust box are respectively provided with a longitudinal air intake chamber, a wind wheel chamber and an exhaust chamber;

[0006] A centrifugal wind wheel with a horizontal axis is rotatably arranged in the wind wheel compartment, and the centrifugal wind wheel is synchronously mounted on a rotating shaft, and an external motor drives and connects to the rotating shaft;

[0007] The upper end of the wind wheel compartment is connected to the exhaust compartment; the exhaust compartment and the wind wheel compartment together form an integrated connected compartment and the air intake compartment are separated by a partition wall; the lower part of the partition wall is hollowed out and provided with an air intake port coaxial with the wind wheel air intake compartment in the center of the centrifugal wind wheel;

[0008] A conical sound-absorbing air guide wall with a pointed end coaxially facing the air suction port is fixedly provided on the inner side of the lower part of the back plate of the air inlet silencer box. The conical sound-absorbing air guide wall forms an annular air guide channel connected to the air suction port in the lower part of the air inlet bin.

[0009] Furthermore, an upper portion of the back plate of the air inlet muffler box is evenly hollowed out to provide an air inlet mesh group, and an air outlet is provided on the side of the upper end of the air exhaust bin away from the partition wall.

[0010] Furthermore, an annular air guide tube with a rounded transition is fixedly provided coaxially along the inner edge contour of the air suction port.

[0011] Furthermore, the partition wall, the wall of the centrifugal wind wheel box, the conical sound-absorbing air guide wall, the upper wall of the exhaust box and the bottom wall of the air inlet sound-absorbing box are all made of sound-absorbing and sound-insulating materials.

[0012] Furthermore, the conical sound-absorbing air-guiding wall is composed of a central cone head, a first cone ring, a second cone ring, a third cone ring and a fourth cone ring, which are coaxially connected from the center to the outermost circle; any two adjacent ones of the central cone head, the first cone ring, the second cone ring, the third cone ring and the fourth cone ring can slide relative to each other along the axial direction.

[0013] Furthermore, a fixed arm is fixedly provided on the outer side of the back plate of the air inlet muffler box, the end of the central cone head away from the tip is fixedly connected to the fixed arm through a central fixing rod, the inner cone surface of the second cone ring is fixedly connected to the fixed arm through at least one connecting arm, and the fourth cone ring is fixedly connected to the back plate of the air inlet muffler box along the contour;

[0014] A first pair of telescopic devices and a second pair of telescopic devices are fixedly installed on the fixed arm, and the telescopic directions of the first pair of telescopic devices and the second pair of telescopic devices are parallel to the axis of the conical sound-absorbing air-guiding wall; the telescopic parts of the first pair of telescopic devices are connected to the first cone ring, and the telescopic parts of the second pair of telescopic devices are connected to the third cone ring, so that the first pair of telescopic devices and the second pair of telescopic devices respectively drive the first cone ring and the third cone ring to deviate along the axial direction.

[0015] Furthermore, a first sound-absorbing groove is provided on the outer cylindrical surface of the first cone ring, a second sound-absorbing groove is provided on the inner cylindrical surface of the second cone ring; a third sound-absorbing groove is provided on the outer cylindrical surface of the third cone ring, and a fourth sound-absorbing groove is provided on the inner cylindrical surface of the fourth cone ring;

[0016] When the telescopic parts of the first pair of telescoping joints and the second pair of telescoping joints are retracted a certain distance based on the initial state, the first cone ring and the third cone ring are offset a certain distance along the axis in the direction away from the tip of the central cone head, so that a first collapsed ring groove is formed between the central cone head and the second cone ring ring, and a second collapsed ring groove is formed between the second cone ring ring and the fourth cone ring ring; at the same time, a first annular sound guide channel connected to the second sound absorbing groove is formed on the inner upper part of the first collapsed ring groove, and the second sound absorbing groove is connected to the first sound absorbing groove; a second annular sound guide channel connected to the fourth sound absorbing groove is formed on the inner upper part of the second collapsed ring groove, and the fourth sound absorbing groove is connected to the third sound absorbing groove.

[0017] Furthermore, a noise measuring point is set one meter away from the centrifugal wind wheel on one side of the conical sound-absorbing wind guide wall, and a decibel meter is provided at the noise measuring point.

[0018] Furthermore, on the basis of the continuous rotation of the centrifugal wind wheel at a specific speed, the telescopic parts of the first pair of telescopes and the second pair of telescopes are controlled to gradually retract on the basis of the initial state. In the above process, the decibel meter at the noise measuring point continuously records the detected decibel number, and establishes a change relationship curve between the decibel value Q at the noise measuring point and the retraction distance H of the telescopic parts of the first pair of telescopes and the second pair of telescopes relative to the initial state. The minimum value q1 of the decibel value Q is taken on the change relationship curve to obtain the corresponding H value h1; when the retraction distance H of the telescopic parts of the first pair of telescopes and the second pair of telescopes relative to the initial state is h1, the best noise reduction effect can be obtained; according to the above rules, the best H value at other fan speeds is obtained.

[0019] Beneficial effect: The sound waves generated by the centrifugal wind wheel of the present invention are projected along the axial direction onto the outer conical surface of the conical sound-absorbing wind guide wall, and the outer conical surface of the conical sound-absorbing wind guide wall absorbs part of the sound waves, thereby achieving the effect of noise reduction;

[0020] In this case, a curve showing the relationship between the decibel value Q at the noise measurement point and the retraction distance H of the telescopic parts of the first pair of telescopic joints and the second pair of telescopic joints relative to the initial state can be obtained. By taking the minimum value q1 of the decibel value Q on the changing relationship curve, the corresponding H value h1 can be obtained. At a specific speed, when the retraction distance H of the telescopic parts of the first pair of telescopic joints and the second pair of telescopic joints relative to the initial state is h1, the best noise reduction effect can be obtained. According to the above rules, the best H values ​​at other fan speeds are obtained, and by executing the best H values ​​at each fan speed in real time, the dynamic best noise reduction effect can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Attachment Figure 1 This is a schematic diagram of the existing bellows structure;

[0022] Attachment Figure 2 This is a schematic diagram of the improved bellows structure;

[0023] Attachment Figure 3 For the Figure 2 "The front cross-sectional diagram of the bellows structure after further improvement based on the previous one;

[0024] Attachment Figure 4 For attachment Figure 3 An enlarged schematic diagram of the mark 8;

[0025] Attachment Figure 5 For attachment Figure 4 A schematic diagram of the first pair of retractors and the second pair of retractors driving the first cone ring and the third cone ring to deviate along the axis direction respectively;

[0026] Attachment Figure 6 For attachment Figure 4 Stereoscopic image of

[0027] Attachment Figure 7 For attachment Figure 5 Stereoscopic image of

[0028] Attachment Figure 8 Schematic diagram of the back panel structure of the air inlet silencer box;

[0029] Attachment Figure 9 The graph is a relationship curve between the decibel value Q at the noise measurement point and the retraction distance H of the telescopic parts of the first pair of telescopic devices and the second pair of telescopic devices relative to the initial state. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings. Figure 1 It is a schematic diagram of the existing bellows structure.

[0031] As attached Figures 2 to 9 The low-noise ventilation box noise reduction system is as follows: Figure 2 As shown, it includes an integrated air inlet silencer box 9, a centrifugal wind wheel box 14 and an exhaust box 2, and the air inlet silencer box 9, the centrifugal wind wheel box 14 and the exhaust box 2 respectively have a longitudinal air inlet bin 5, a wind wheel bin 12 and an exhaust bin 3; a centrifugal wind wheel 13 with a horizontal axis is rotatably arranged in the wind wheel bin 12, and the centrifugal wind wheel 13 is synchronously installed on the rotating shaft 15, and the external motor drives the connecting rotating shaft 15; the upper end of the wind wheel bin 12 is connected to the exhaust bin 3; the integrated connecting bin formed by the exhaust bin 3 and the wind wheel bin 12 is separated from the air inlet bin 5 by a partition wall 4; an air outlet 1 is provided on the side of the upper end of the exhaust bin 3 away from the partition wall 4; the lower part of the partition wall 4 is hollowed out and an air inlet 10 is provided which is coaxial with the wind wheel air inlet bin 13a in the center of the centrifugal wind wheel 13; the upper part of the back plate 9.1 of the air inlet silencer box 9 is evenly hollowed out and an air inlet mesh group 18 is provided, as shown Figure 8 As shown, a conical sound-absorbing air guide wall 8 with a pointed coaxial center facing the air suction port 10 is fixedly provided on the inner side of the lower part of the back plate 9.1 of the air inlet silencer box 9. The conical sound-absorbing air guide wall 8 forms an annular air guide channel 5.1 in communication with the air suction port 10 at the lower part of the air inlet bin 5; the sound waves generated by the high-speed rotating centrifugal wind wheel 13 pass through the air suction port 10 along the axial direction and are projected onto the outer cone surface of the conical sound-absorbing air guide wall 8 along the axial direction. The smooth outer cone surface of the conical sound-absorbing air guide wall 8 absorbs part of the sound waves, thereby achieving the effect of noise reduction. In this case, relative to Figure 1 The existing bellows structure can effectively reduce the noise by about 15 decibels at the same normal fan speed.

[0032] An annular air guide tube 17 with a rounded transition is fixedly provided coaxially along the inner edge contour of the air suction port 10. The annular air guide tube 17 guides the flow direction of the air path to a more rounded transition to avoid sudden changes, thereby reducing the whistling sound of local vortex.

[0033] In the overall airflow path of this case, when the centrifugal wind wheel 13 rotates at high speed, the outdoor air enters the air intake bin 5 through the air inlet mesh group 18 on the upper part of the back plate 9.1 under the action of negative pressure. The air entering the air intake bin 5 flows downward, and then is sucked into the wind wheel air inlet bin 13a in the center of the centrifugal wind wheel 13 of the wind wheel bin 12 through the annular air guide channel 5.1 and the air suction port 10 in turn. The air entering the wind wheel air inlet bin 13a is driven by the high-speed rotating centrifugal wind wheel 13 and thrown upward to the exhaust bin 3, so that wind pressure is formed in the exhaust bin 3. Finally, the air in the exhaust bin 3 is discharged through the air outlet 1 under the action of wind pressure and blown to the condenser that needs heat dissipation.

[0034] In order to improve the sound insulation effect of the wall, the partition wall 4, the wall of the centrifugal wind wheel box 14, the conical sound-absorbing air guide wall 8, the upper wall of the exhaust box 2 and the bottom wall of the air inlet silencer box 9 in this case are all made of sound-absorbing and sound-insulating materials; the wall of the sound-absorbing and sound-insulating material is a composite layer structure formed by bonding and superimposing micro-perforated thin plates and polyester foam pads.

[0035] This case makes the following further optimization design based on the above structure:

[0036] like Figures 3 to 9 As shown, the conical sound-absorbing air-guiding wall 8 is composed of a central cone head 8a, a first cone ring 8b, a second cone ring 8c, a third cone ring 8d and a fourth cone ring 8e, which are coaxially spliced ​​from the center to the outermost circle; the central cone head 8a, the first cone ring 8b, the second cone ring 8c, the third cone ring 8d and the fourth cone ring 8e are all made of sound-absorbing and sound-insulating materials; any two adjacent ones of the central cone head 8a, the first cone ring 8b, the second cone ring 8c, the third cone ring 8d and the fourth cone ring 8e can slide relative to each other along the axial direction; a vertical fixed arm 23 is fixedly provided on the outside of the back plate 9.1 of the air inlet silencer box 9, and the end of the central cone head 8a away from the tip is fixedly connected to the fixed arm 23 by a central fixing rod 27, and the inner cone surface of the second cone ring 8c is fixedly connected to the fixed arm 23 by at least one connecting arm 25, and the fourth cone ring 8e is fixedly connected to the back plate 9.1 of the air inlet silencer box 9 along the contour.

[0037] A first pair of telescopic devices 26 and a second pair of telescopic devices 24 are fixedly mounted on the fixed arm 23. The telescopic directions of the first pair of telescopic devices 26 and the second pair of telescopic devices 24 are both parallel to the axis of the conical sound-absorbing air guide wall 8. The telescopic portion of the first pair of telescopic devices 26 is connected to the first cone ring 8b, and the telescopic portion of the second pair of telescopic devices 24 is connected to the third cone ring 8d, so that the first pair of telescopic devices 26 and the second pair of telescopic devices 24 respectively drive the first cone ring 8b and the third cone ring 8d to deviate along the axial direction.

[0038] A first sound-absorbing groove 31 is provided on the outer cylindrical surface of the first cone ring 8b, and a second sound-absorbing groove 30 is provided on the inner cylindrical surface of the second cone ring 8c; a third sound-absorbing groove 29 is provided on the outer cylindrical surface of the third cone ring 8d, and a fourth sound-absorbing groove 28 is provided on the inner cylindrical surface of the fourth cone ring 8e;

[0039] When the telescopic parts of the first pair of telescoping members 26 and the second pair of telescoping members 24 are retracted a certain distance based on the initial state, the first cone ring 8b and the third cone ring 8d are offset a certain distance along the axis toward the direction away from the tip of the central cone head 8a, so that a first collapsed ring groove 20 is formed between the central cone head 8a and the second cone ring 8c, and a second collapsed ring groove 19 is formed between the second cone ring 8c and the fourth cone ring 8e; at the same time, a first annular sound guide channel 22 connected to the second sound absorbing groove 30 is formed on the inner upper part of the first collapsed ring groove 20, and the second sound absorbing groove 30 is connected to the first sound absorbing groove 31; a second annular sound guide channel 21 connected to the fourth sound absorbing groove 28 is formed on the inner upper part of the second collapsed ring groove 19, and the fourth sound absorbing groove 28 is connected to the third sound absorbing groove 29.

[0040] A noise measuring point 50 is set one meter away from the centrifugal wind wheel 13 on one side of the conical sound-absorbing wind guide wall 8, and a decibel meter is provided at the noise measuring point.

[0041] Working principle:

[0042] In the initial state Figure 3 and 4 The outer conical surface of the conical sound-absorbing wind guide wall 8 absorbs part of the sound waves, thereby achieving the effect of noise reduction. The sound waves not absorbed by the outer conical surface of the conical sound-absorbing wind guide wall 8 are transmitted upward to the upper part of the air intake bin 5 through the annular air guide channel 5.1. The attenuated sound waves are finally transmitted into the room through the air intake mesh group 18 on the upper part of the back plate 9.1, and are finally transmitted to the decibel meter at the noise measuring point 50. In this state, the outer conical surface of the conical sound-absorbing wind guide wall 8 is a smooth outer conical surface. Although it can avoid the formation of vortexes at the annular air guide channel 5.1, the smooth outer conical surface of the conical sound-absorbing wind guide wall 8 has limited ability to absorb noise.

[0043] In the initial state, the centrifugal wind wheel 13 rotates continuously at a specific speed. Figure 5 and 7, the telescopic parts of the first pair of telescoping members 26 and the second pair of telescoping members 24 are controlled to gradually retract based on the initial state, so that the first cone ring 8b and the third cone ring 8d are gradually offset along the axis in a direction away from the tip of the central cone head 8a. During the above process, the decibel meter at the noise measuring point 50 continuously records the detected decibel value, and establishes a relationship curve 80 between the decibel value Q at the noise measuring point 50 and the retraction distance H of the telescoping parts of the first pair of telescoping members 26 and the second pair of telescoping members 24 relative to the initial state, as shown in FIG. Figure 9 As shown; until a first collapsed ring groove 20 is formed between the central cone head 8a and the second cone ring ring 8c, and a second collapsed ring groove 19 is formed between the second cone ring ring 8c and the fourth cone ring ring 8e; at the same time, a first annular sound guide channel 22 connected to the second sound absorbing groove 30 is formed on the inner upper part of the first collapsed ring groove 20, and the second sound absorbing groove 30 is connected to the first sound absorbing groove 31; a second annular sound guide channel 21 connected to the fourth sound absorbing groove 28 is formed on the inner upper part of the second collapsed ring groove 19, and the fourth sound absorbing groove 28 is connected to the third sound absorbing groove 29.

[0044] At this time, the sound waves generated by the high-speed rotating centrifugal wind wheel 13 pass through the air suction port 10 along the axial direction and are projected onto the outer cone surface of the conical sound-absorbing wind guide wall 8 along the axial direction. Since the outer cone surface of the conical sound-absorbing wind guide wall 8 forms a first collapsed annular groove 20 and a second collapsed annular groove 19, when the sound waves reach the first collapsed annular groove 20 and the second collapsed annular groove 19, they are respectively transmitted to the second sound-absorbing groove 30 and the fourth sound-absorbing groove 28 through the first annular sound guide channel 22 and the second annular sound guide channel 21 to be dissipated and weakened, and then pass through the second sound-absorbing groove 30 and the fourth sound-absorbing groove 28 to be dissipated and weakened. The sound waves weakened by the sound groove 30 and the fourth sound absorbing groove 28 are further transmitted to the first sound absorbing groove 31 and the third sound absorbing groove 29 respectively and are completely eliminated; thereby achieving a more enhanced sound absorption effect and sound wave capture intensity. Although there is a stronger sound wave capture intensity at this time, the greater the collapse depth of the first collapse ring groove 20 and the second collapse ring groove 19, the easier it is to generate vortices in the first collapse ring groove 20 and the second collapse ring groove 19, thereby forming a whistling sound caused by the vortex, thereby forming a new noise source.

[0045] Therefore, the regularity and trend of the relationship between the decibel value Q at the noise measurement point 50 and the retraction distance H of the telescopic parts of the first pair of telescopic members 26 and the second pair of telescopic members 24 relative to the initial state cannot be accurately known in advance;

[0046] In this case, a curve 80 showing the relationship between the decibel value Q at the noise measurement point 50 and the retraction distance H of the telescopic parts of the first pair of telescopic members 26 and the second pair of telescopic members 24 relative to the initial state can be obtained. Figure 9 As shown; taking the minimum value q1 of the decibel value Q on the change relationship curve 80, the corresponding value h1 of H can be obtained;

[0047] The conclusion obtained at this time is that: at a specific rotation speed, the best noise reduction effect can be achieved when the retraction distance H of the telescopic parts of the first pair of telescopic devices 26 and the second pair of telescopic devices 24 relative to the initial state is h1;

[0048] According to the above rules, the optimal H value at other fan speeds can be obtained, and the optimal H value at each fan speed can be executed in real time to achieve the dynamic optimal noise reduction effect.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low-noise ventilation box noise reduction system, characterized in that: It comprises an air inlet silencer box (9), a centrifugal wind wheel box (14) and an air exhaust box (2) which are integrally arranged, wherein the air inlet silencer box (9), the centrifugal wind wheel box (14) and the air exhaust box (2) respectively contain a longitudinal air inlet chamber (5), a wind wheel chamber (12) and an air exhaust chamber (3); A centrifugal wind wheel (13) with a horizontal axis is rotatably arranged in the wind wheel compartment (12); the centrifugal wind wheel (13) is synchronously mounted on a rotating shaft (15); and an external motor is connected to the rotating shaft (15); The upper end of the wind wheel chamber (12) is connected to the exhaust chamber (3); the integrated connected chamber formed by the exhaust chamber (3) and the wind wheel chamber (12) is separated from the air intake chamber (5) by a partition wall (4); the lower part of the partition wall (4) is hollowed out to provide an air intake port (10) coaxial with the wind wheel air intake chamber (13a) at the center of the centrifugal wind wheel (13); A conical sound-absorbing air guide wall (8) with a pointed end coaxially facing the air suction port (10) is fixedly provided on the inner side of the lower part of the back plate (9.1) of the air inlet sound-absorbing box (9), and the conical sound-absorbing air guide wall (8) enables the lower part of the air inlet bin (5) to form an annular air guide channel (5.1) connected to the air suction port (10); The upper part of the back plate (9.1) of the air inlet muffler box (9) is evenly hollowed out to form an air inlet mesh group (18), and the upper end of the air exhaust bin (3) is provided with an air outlet (1) on a side away from the partition wall (4); The air suction port (10) is coaxially and fixedly provided with an annular air guide tube (17) with a rounded transition along the inner edge contour; The partition wall (4), the wall of the centrifugal wind wheel box (14), the conical sound-absorbing air guide wall (8), the upper wall of the exhaust air box (2) and the bottom wall of the air inlet sound-absorbing box (9) are all made of sound-absorbing and sound-insulating materials; The conical sound-absorbing air guide wall (8) is composed, from the center to the outermost circle, of a central cone head (8a), a first cone ring (8b), a second cone ring (8c), a third cone ring (8d) and a fourth cone ring (8e) which are coaxially movably spliced ​​together; any two adjacent ones of the central cone head (8a), the first cone ring (8b), the second cone ring (8c), the third cone ring (8d) and the fourth cone ring (8e) can slide relative to each other along the axial direction.

2. A low-noise ventilation box noise reduction system according to claim 1, characterized in that: A fixing arm (23) is fixedly provided on the outside of the back plate (9.1) of the air inlet muffler box (9); the end of the central cone head (8a) away from the tip is fixedly connected to the fixing arm (23) via a central fixing rod (27); the inner cone surface of the second cone ring (8c) is fixedly connected to the fixing arm (23) via at least one connecting arm (25); and the fourth cone ring (8e) is fixedly connected to the back plate (9.1) of the air inlet muffler box (9) along its contour; A first pair of telescopic devices (26) and a second pair of telescopic devices (24) are fixedly mounted on the fixed arm (23); the telescopic directions of the first pair of telescopic devices (26) and the second pair of telescopic devices (24) are both parallel to the axis of the conical sound-absorbing air guide wall (8); the telescopic parts of the first pair of telescopic devices (26) are connected to the first cone ring (8b), and the telescopic parts of the second pair of telescopic devices (24) are connected to the third cone ring (8d), so that the first pair of telescopic devices (26) and the second pair of telescopic devices (24) respectively drive the first cone ring (8b) and the third cone ring (8d) to deviate along the axis direction.

3. A low-noise ventilation box noise reduction system according to claim 2, characterized in that: A circle of first sound absorbing grooves (31) is arranged on the outer cylindrical surface of the first cone ring (8b), and a circle of second sound absorbing grooves (30) is arranged on the inner cylindrical surface of the second cone ring (8c); a circle of third sound absorbing grooves (29) is arranged on the outer cylindrical surface of the third cone ring (8d), and a circle of fourth sound absorbing grooves (28) is arranged on the inner cylindrical surface of the fourth cone ring (8e); When the telescopic parts of the first pair of telescoping devices (26) and the second pair of telescoping devices (24) are retracted a certain distance based on the initial state, the first cone ring (8b) and the third cone ring (8d) are both offset a certain distance along the axis in a direction away from the tip of the central cone head (8a), so that a first collapsed ring groove (20) is formed between the central cone head (8a) and the second cone ring (8c), and a second collapsed ring groove (19) is formed between the second cone ring (8c) and the fourth cone ring (8e); at the same time, a first annular sound guide channel (22) connected to the second sound absorbing groove (30) is formed on the inner upper part of the first collapsed ring groove (20), and the second sound absorbing groove (30) is connected to the first sound absorbing groove (31); and a second annular sound guide channel (21) connected to the fourth sound absorbing groove (28) is formed on the inner upper part of the second collapsed ring groove (19), and the fourth sound absorbing groove (28) is connected to the third ring sound absorbing groove (29).

4. A low-noise ventilation box noise reduction system according to claim 3, characterized in that: A noise measuring point (50) is arranged one meter away from the centrifugal wind wheel (13) on one side of the conical sound-absorbing wind guide wall (8), and a decibel meter is arranged at the noise measuring point.

5. The working method of the low-noise ventilation box noise reduction system according to claim 4 is characterized in that: On the basis of the centrifugal wind wheel (13) continuously rotating at a specific speed, the telescopic parts of the first pair of telescopic devices (26) and the second pair of telescopic devices (24) are controlled to gradually retract on the basis of the initial state. In the above process, the decibel meter at the noise measuring point (50) continuously records the detected decibel number, and establishes a change relationship curve (80) between the decibel value Q at the noise measuring point (50) and the retracted distance H of the telescopic parts of the first pair of telescopic devices (26) and the second pair of telescopic devices (24) relative to the initial state. The minimum value q1 of the decibel value Q is taken on the change relationship curve (80) to obtain the corresponding H value h1; when the retracted distance H of the telescopic parts of the first pair of telescopic devices (26) and the second pair of telescopic devices (24) relative to the initial state is h1, the best noise reduction effect can be obtained; according to the above rule, the best H value at other fan speeds is obtained.

Images