A movable frequency adjustable measurement of sound absorbing material alternating flow resistance system

Abstract

The present application belongs to the technical field of sound absorption material flow resistance measurement, and particularly relates to a system for measuring the alternating flow resistance of sound absorption material with adjustable motion frequency, comprising a measuring closed cavity device, wherein the measuring closed cavity device comprises a workbench, a container, a closed cavity, a piston, a microphone, a sealing ring and a sealing cover; the container is fixed above the workbench; the sealing cover is detachably fixed to the top of the container through a fixing screw; a sealing ring is arranged between the sealing cover and the container; the sealing cover and the container constitute a closed cavity; a sleeve in communication with the container is fixed to one side of the container; the piston is sealingly and slidably connected in the sleeve; a sound outlet is formed in the side wall of the container; and the microphone is arranged in the sound outlet. The present application ensures the stability of the reciprocating movement of the piston by arranging the anti-vibration assembly, improves the measurement accuracy, avoids the influence of the temperature change in the closed cavity on the measurement results by arranging the heat dissipation assembly, and improves the measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of sound-absorbing material flow resistance measurement technology, and in particular relates to a system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency. Background Technology

[0002] As one of the main means of sound field control, the sound absorption performance of materials has received increasing attention from acousticians. The flow resistance of a material is a basic parameter that reflects its internal porosity and some structural characteristics. The flow resistance can be used to establish the relationship between the material structure and some acoustic properties of the material (such as sound absorption characteristics, attenuation characteristics, etc.). The prerequisite for designing and producing high-performance sound-absorbing materials is to accurately and efficiently measure their flow resistance characteristics.

[0003] Methods for measuring the flow resistance of sound-absorbing materials include the DC method, impedance tube method, and AC measuring device method. Among them, the AC measuring device method uses a motor to drive an eccentric wheel to drive a piston to make reciprocating linear motion, thereby generating alternating airflow in the test chamber. The sound pressure level in the wall is measured by a microphone. It is simple and convenient to operate. Compared with the traditional differential pressure gauge to measure pressure difference, the microphone has higher resolution, better response characteristics, and higher accuracy in measuring alternating gas pressure, thus ensuring the accuracy of flow resistance measurement.

[0004] The existing device also has the following shortcomings:

[0005] 1. When the motor drives the eccentric wheel to rotate, the weight on both sides of the motor output shaft is unbalanced, and the eccentric wheel often vibrates when rotating, which makes the piston's reciprocating motion unstable and affects the accuracy of the measurement results.

[0006] 2. When the piston reciprocates, it rubs against the side wall of the piston cylinder at high speed, generating heat. This heat will raise the temperature of the air inside the cavity, thereby affecting the volume of air and the air pressure inside the cavity, thus affecting the accuracy of the measurement results. Summary of the Invention

[0007] The purpose of this invention is to address the problems mentioned in the background art by providing a system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency.

[0008] To achieve the above objectives, the present invention employs the following technical solution: a system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency, comprising:

[0009] A device for measuring a sealed cavity includes a worktable, a container, a sealed cavity, a piston, a microphone, a sealing ring, and a sealing cover. The container is fixed above the worktable, and the sealing cover is detachably fixed to the top of the container by fixing screws. A sealing ring is provided between the sealing cover and the container, and the sealing cover and the container form a sealed cavity. A sleeve communicating with the container is fixed to one side of the container, and a piston is slidably connected inside the sleeve. A sound outlet is opened on the side wall of the container, and a microphone is provided inside the sound outlet. A drive assembly for driving the piston to reciprocate is provided on the worktable.

[0010] A test specimen measuring device includes a measuring tube, a test specimen, and a perforated plate support. The measuring tube is installed above a container, and the test specimen is fixed inside the measuring tube by the perforated plate support.

[0011] Furthermore, the drive assembly includes a motor fixed to the bottom of the worktable, the output shaft of the motor extending through the worktable to the top of the worktable, an eccentric wheel on the output shaft of the motor, an annular groove on the upper surface of the eccentric wheel, a piston rod fixed to the piston, and a movable rod fixed to the end of the piston rod away from the piston, the movable rod being slidably connected in the annular groove.

[0012] Furthermore, a stroke adjustment component is provided between the eccentric wheel and the output shaft of the motor. The stroke adjustment component includes a U-shaped frame fixed on the output shaft of the motor, a movable block is slidably connected inside the U-shaped frame, and the eccentric wheel is disposed on the movable block.

[0013] Furthermore, the U-shaped frame is also provided with a vibration damping component, which includes a counterweight block slidably connected to the U-shaped frame. Both the counterweight block and the movable block are provided with racks. A central shaft is fixed at the center of the U-shaped frame. A spur gear that meshes with the rack is rotatably connected to the central shaft. Both the counterweight block and the movable block are provided with through slots through which the rack can pass.

[0014] Furthermore, a spherical groove is provided at the bottom of the movable rod, and a ball bearing is provided in the spherical groove.

[0015] Furthermore, the piston rod is provided with a heat dissipation assembly, which includes an annular plate fixed to the piston rod, two symmetrically arranged connecting plates fixed on the annular plate, and a heat dissipation plate fixed at the end of the connecting plate away from the annular plate.

[0016] Furthermore, the heat sink is provided with multiple first slide rails and second slide rails, which are spaced apart. A first slide rod and a second slide bar are slidably connected inside the first slide rail and the second slide rail, respectively. Two heat absorption plates are rotatably connected to the first slide bar by a torsion spring. The end of the heat absorption plate away from the first slide bar is rotatably connected to the second slide bar. A first metal sheet and a second metal sheet are fixed on the two heat absorption plates, respectively. A third metal sheet is provided on the heat sink at a position corresponding to the first metal sheet and the second metal sheet. A first semiconductor is provided between the third metal sheet and the first metal sheet, and a second semiconductor is provided between the third metal sheet and the second metal sheet.

[0017] Furthermore, an electromagnet is embedded in the end of the first slide rail away from the heat sink, and a permanent magnet is provided on the first slide rod. The electromagnet and the permanent magnet have opposite magnetic properties on the side that are close to each other.

[0018] Furthermore, the output shaft of the motor is provided with a heat dissipation adjustment component, which includes a hollow cylinder fixed on the output shaft of the motor. A varistor is provided at the end of the hollow cylinder away from the output shaft of the motor. The varistor and the electromagnet are connected in series. A metal ball is fixed at the end of the hollow cylinder near the output shaft of the motor by an elastic rope.

[0019] Compared with existing technologies, the advantages of this invention are:

[0020] 1. This invention incorporates a vibration-damping component. By setting a counterweight within the U-shaped frame to balance the weight of the movable block and the eccentric wheel, the weight on both sides of the motor output shaft is balanced, preventing vibration caused by the imbalance of weight on both sides of the motor output shaft when the eccentric wheel rotates. This ensures the stability of the piston during reciprocating movement and improves measurement accuracy.

[0021] 2. By setting up a rack and pinion, the position of the eccentric wheel is adjusted to change the piston stroke. With the cooperation of the pinion and rack, the position of the counterweight changes synchronously with the position of the eccentric wheel, eliminating the need to adjust the position of the counterweight separately and improving work efficiency.

[0022] 3. By incorporating a heat dissipation component, the present invention dissipates heat from the sleeve during the reciprocating movement of the piston, preventing the heat generated by friction between the piston and the sleeve from altering the temperature inside the sealed cavity. This avoids the influence of temperature changes inside the sealed cavity on the measurement results and improves measurement accuracy.

[0023] 4. By setting up a heat dissipation effect adjustment component, the higher the motor speed, the more heat is generated when the piston reciprocates, and the higher the heat dissipation efficiency of the heat absorption plate. The lower the motor speed, the less heat is generated when the piston reciprocates, and the heat dissipation efficiency of the heat absorption plate also decreases. This ensures that the gas temperature in the sealed cavity remains stable when the motor rotates at different speeds, avoiding the influence of temperature changes on the measurement results. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of an adjustable motion frequency measurement system for sound-absorbing materials with alternating flow resistance, provided by the present invention.

[0025] Figure 2 This is a top view schematic diagram of an adjustable motion frequency measurement alternating flow resistance system for sound-absorbing materials provided by the present invention.

[0026] Figure 3 yes Figure 2 Sectional view along the AA direction;

[0027] Figure 4 yes Figure 3 Enlarged view at point B in the middle;

[0028] Figure 5 yes Figure 3 Enlarged view at point C;

[0029] Figure 6 This is a schematic diagram of the internal structure of a U-shaped frame for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency, provided by the present invention.

[0030] Figure 7 This is a schematic diagram of the measuring specimen device for a measuring alternating flow resistance system for sound-absorbing materials with adjustable motion frequency, provided by the present invention.

[0031] Figure 8 This is a schematic diagram of the overall structure of the heat dissipation component of an adjustable motion frequency measurement sound-absorbing material alternating flow resistance system provided by the present invention.

[0032] Figure 9 This is a schematic diagram of the heat dissipation component of an adjustable motion frequency measurement sound-absorbing material alternating current resistance system provided by the present invention.

[0033] Figure 10 This is a schematic diagram of the heat dissipation component state structure corresponding to different motor speeds in an alternating current resistance system for measuring sound-absorbing materials with adjustable motion frequency, provided by the present invention.

[0034] Figure 11 This is a schematic diagram of the current direction of a heat dissipation component in an adjustable motion frequency measurement system for alternating current resistance of sound-absorbing materials, provided by the present invention.

[0035] In the figure, 1 is the workbench, 2 is the container, 21 is the sleeve, 22 is the sound outlet, 3 is the sealed cavity, 4 is the piston, 41 is the piston rod, 42 is the movable rod, 421 is the ball, 5 is the microphone, 6 is the sealing ring, 7 is the sealing cover, 71 is the fixing screw, 81 is the measuring tube, 82 is the test piece, and 83 is the perforated plate bracket.

[0036] 9 motor, 91 eccentric wheel, 911 annular groove, 92 U-shaped frame, 921 movable block;

[0037] 93 counterweight, 94 rack, 95 central shaft, 951 column gear, 96 through slot;

[0038] 411 Annular plate, 412 Connecting plate, 43 Heat sink, 431 First slide rail, 432 Second slide rail, 433 First slide rod, 434 Second slide rod, 435 Heat absorber plate, 4351 First metal sheet, 4352 Second metal sheet, 4311 Third metal sheet, 436 First semiconductor, 437 Second semiconductor, 4312 Electromagnet, 4331 Permanent magnet;

[0039] 10 Hollow cylinder, 101 Varistor, 102 Elastic rope, 103 Metal ball. Detailed Implementation

[0040] The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0041] like Figures 1-11 As shown, a system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency includes:

[0042] A device for measuring a sealed cavity includes a workbench 1, a container 2, a sealed cavity 3, a piston 4, a microphone 5, a sealing ring 6, and a sealing cover 7. The container 2 is fixed above the workbench 1. The top of the container 2 is detachably and fixedly connected to the sealing cover 7 by a fixing screw 71. A sealing ring 6 is provided between the sealing cover 7 and the container 2. The sealing cover 7 and the container 2 form a sealed cavity 3. A sleeve 21 communicating with the container is fixed to one side of the container 2. The piston 4 is slidably connected inside the sleeve 21. A sound outlet 22 is opened on the side wall of the container 2. A microphone 5 is provided inside the sound outlet 22. The microphone 5 is used to measure the sound pressure level in the sealed cavity 3. A drive assembly for driving the piston 4 to move back and forth is provided on the workbench 1.

[0043] The drive assembly includes a motor 9 fixed to the bottom of the worktable 1. The output shaft of the motor 9 extends through the worktable 1 to the top of the worktable 1. An eccentric wheel 91 is provided on the output shaft of the motor 9. An annular groove 911 is provided on the upper surface of the eccentric wheel 91. A piston rod 41 is fixed on the piston 4. A movable rod 42 is fixed at the end of the piston rod 41 away from the piston 4. The movable rod 42 is slidably connected in the annular groove 911. A spherical groove is provided at the bottom of the movable rod 42. A ball bearing 421 is provided in the spherical groove.

[0044] In actual operation, the motor 9 rotates to drive the eccentric wheel 91 to rotate. Under the action of the annular groove 911 and the movable rod 42, the piston rod 41 and the piston 4 reciprocate within the sleeve 21. The ball 421 transforms the sliding friction between the bottom of the movable rod 42 and the bottom of the annular groove 911 into rolling friction, thereby reducing the friction between the movable rod 42 and the annular groove 911, making the piston 4 move more smoothly within the sleeve 21. At the same time, it can reduce the wear of the movable rod 42 and the eccentric wheel 91, and extend the service life of the device.

[0045] A stroke adjustment component is provided between the eccentric wheel 91 and the output shaft of the motor 9. The stroke adjustment component includes a U-shaped frame 92 fixed on the output shaft of the motor 9. A movable block 921 is slidably connected inside the U-shaped frame 92. A control component for controlling the movement of the movable block 921 is provided inside the U-shaped frame 92. The control component adopts existing technology and will not be described in detail here. The eccentric wheel 91 is located on the movable block 921.

[0046] In actual operation, the position of the movable block 921 within the U-shaped frame 92 is controlled by the control component, thereby changing the distance between the movable block 921 and the center of the output shaft of the motor 9, thus adjusting the eccentricity of the eccentric wheel 91 and changing the stroke of the piston 4.

[0047] The U-shaped frame 92 is also equipped with a vibration damping component, which includes a counterweight 93 slidably connected within the U-shaped frame 92. The counterweight 93 is used to adjust the balance of the U-shaped frame 92, preventing the U-shaped frame 92 from tilting due to excessive weight at one end. This, in turn, prevents vibration caused by the tilt of the U-shaped frame 92 when the eccentric wheel 91 rotates, ensuring that the eccentric wheel 91 rotates stably around the output shaft of the motor 9, thereby ensuring the stability of the piston 4's movement. Both the counterweight 93 and the movable block 921 are equipped with racks 94. A central shaft 95 is fixed at the center of the U-shaped frame 92. A spur gear 951 that meshes with a rack 94 is rotatably connected to the central shaft 95. Both the counterweight 93 and the movable block 921 are provided with through slots 96 through which the rack 94 can pass. When the position of the movable block 921 is adjusted, the counterweight 93 and the movable block 921 move synchronously under the cooperation of the spur gear 951 and the rack 94 to ensure that the two ends of the U-shaped frame 92 are balanced. There is no need to adjust the position of the counterweight 93 separately, which results in high working efficiency.

[0048] The measuring specimen device includes a measuring tube 81, a specimen 82, and a perforated plate bracket 83. When measuring time 82, the sealing cover 7 is removed, the measuring tube 81 is installed above the container 2, and then the specimen 82 is fixed inside the measuring tube 81 through the perforated plate bracket 83.

[0049] The piston rod 41 is equipped with a heat dissipation assembly, which includes an annular plate 411 fixed to the piston rod 41. Two symmetrically arranged connecting plates 412 are fixed on the annular plate 411. A heat dissipation plate 43 is fixed to the end of each connecting plate 412 away from the annular plate 411. The heat dissipation plate 43 has multiple first slide rails 431 and second slide rails 432, spaced apart. A first slide rod 433 and a second slide rod 434 are slidably connected within the first slide rails 431 and 432, respectively. Two heat-absorbing plates 435 are rotatably connected to the first slide rod 433 via a torsion spring. Both the heat-absorbing plates 435 and the heat dissipation plates 43 are made of thermally conductive but non-conductive ceramic material, absorbing heat... The end of plate 435 away from the first slide bar 433 is rotatably connected to the second slide bar 434. In the natural state of the torsion spring, the first slide bar 433 and the second slide bar 434 are respectively located on the side of the first slide rail 431 and the second slide rail 432 close to the heat sink 43. The two heat absorber plates 435 are respectively fixed with a first metal sheet 4351 and a second metal sheet 4352. A third metal sheet 4311 is provided on the heat sink 43 at the position corresponding to the first metal sheet 4351 and the second metal sheet 4352. A first semiconductor 436 is provided between the third metal sheet 4311 and the first metal sheet 4351, and a second semiconductor 437 is provided between the third metal sheet 4311 and the second metal sheet 4352.

[0050] like Figure 11 As shown, during actual operation, current is supplied to the heat dissipation component. The arrows in the figure indicate the direction of the current. According to the Peltier effect, when current flows through a circuit composed of two different conductors, heat absorption and heat release will occur at the joint. Specifically, when current flows from one conductor to another, one joint will absorb heat, while the other joint will release heat. In this embodiment, heat is released when current flows from the first semiconductor 436 to the second semiconductor 437, and heat is absorbed when current flows from the second semiconductor 437 to the first semiconductor 436. This enables the heat-absorbing plate 435 to dissipate heat from the sleeve 21, preventing the heat generated by friction between the piston 4 and the sleeve 21 during reciprocating movement from affecting the measurement results.

[0051] An electromagnet 4312 is embedded in the end of the first slide rail 431 away from the heat sink 43. A permanent magnet 4331 is provided on the first slide rod 433. The electromagnet 4312 and the permanent magnet 4331 have opposite magnetic properties on the side that are close to each other. When the electromagnet 4312 is energized, it attracts the permanent magnet 4331. The greater the current through the electromagnet 4312, the stronger the attraction of the electromagnet 4312 to the permanent magnet 4331. The attraction of the electromagnet 4312 to the permanent magnet 4331 drives the first slide rod 433 to move closer to the sleeve 21. A heat dissipation effect adjustment component is provided on the output shaft of the motor 9. The heat dissipation effect adjustment component includes a hollow cylinder 10 fixed on the output shaft of the motor 9. A varistor 101 is provided at the end of the hollow cylinder 10 away from the output shaft of the motor 9. The circuit connection between the varistor 101 and the electromagnet 4312 is in series. A metal ball 103 is fixed at the end of the hollow cylinder 10 close to the output shaft of the motor 9 by an elastic rope 102.

[0052] In the non-operating state, the metal ball 103 separates from the varistor 101 under the tension of the elastic rope 102. The varistor 101 is not under pressure, and its resistance is relatively high. The current through the electromagnet 4312 is very small, and the attraction force of the electromagnet 4312 on the permanent magnet 4331 is also relatively weak. When the motor 9 rotates, the hollow cylinder 10 rotates synchronously. Under the action of centrifugal force, the metal ball 103 contacts and squeezes the varistor 101. Furthermore, the higher the speed of the motor 9, the greater the centrifugal force on the metal ball 103, and the stronger the effect of the metal ball 103 on the varistor 101. The greater the applied pressure, the smaller the resistance of the varistor 101, the greater the current through the electromagnet 4312, the greater the attraction of the electromagnet 4312 to the permanent magnet 4331, the farther the first slide rod 433 moves towards the sleeve 21, and the better the heat dissipation effect of the heat sink 435. When the motor 9 stops rotating, the metal ball 103 separates from the varistor 101, the resistance of the varistor 101 increases, the current through the electromagnet 4312 decreases, the attraction of the electromagnet 4312 to the permanent magnet 4331 decreases, and the first slide rod 433 returns to its initial position under the action of the torsion spring.

[0053] In actual operation, the higher the speed of motor 9, the higher the frequency of piston 4 reciprocating, and the greater the heat generated by friction between piston 4 and sleeve 21. At the same time, the higher the speed of motor 9, the greater the attraction of electromagnet 4312 to permanent magnet 4331, thereby attracting the first slide rod 433 towards sleeve 21, bringing heat-absorbing plate 435 closer to sleeve 21 to increase heat dissipation. That is, the higher the speed of motor 9, the more heat is generated when piston 4 reciprocates, and the higher the heat dissipation efficiency of heat-absorbing plate 435. The lower the speed of motor 9, the less heat is generated when piston 4 reciprocates, and the lower the heat dissipation efficiency of heat-absorbing plate 435. This ensures that the gas temperature in sealed cavity 3 remains stable when motor 9 rotates at different speeds, avoiding the influence of temperature changes on measurement results.

[0054] The specific steps for measuring flow resistance in this invention are as follows:

[0055] S1. Without installing the measuring tube 81 and the sealing cover 7, turn on the motor 9 and measure the background noise sound pressure level Lp,b and static pressure Ps when the piston 4 is working.

[0056] S2. Fix the test piece 82 to the lower end of the measuring tube 81 with the perforated plate bracket 83, and then install it on the container 2. Adjust the movement frequency and stroke hs of the piston 4. After the piston 4 moves stably, measure the reciprocating frequency f, stroke hs and sound pressure level Lp,s in the sealed cavity 3.

[0057] S3. Replace the measuring tube 81 and the test piece 82 with the sealing cap 7, keep the frequency of piston 4 movement unchanged, adjust the stroke ht of piston 4, and measure the sound pressure level Lp,t in the sealed cavity when the end is sealed after piston 4 movement is stable.

[0058] S4. Calculate the flow resistance R of the specimen according to the following formula:

[0059]

[0060] In the formula, к' is the effective specific heat ratio of air, which is 1.37 under standard temperature, humidity and atmospheric conditions.

[0061] S5. The validity of the above measurements shall be verified using the following two formulas:

[0062]

[0063] L p,s -L p,b >10dB

[0064] If the requirements of the above two equations are not met, change the movement frequency of piston 4 or adjust the movement stroke of piston 4 and retest until the requirements are met.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency, characterized in that, include: A measuring device for a sealed cavity includes a workbench (1), a container (2), a sealed cavity (3), a piston (4), a microphone (5), a sealing ring (6), and a sealing cover (7). The container (2) is fixed above the workbench (1). The top of the container (2) is detachably and fixedly connected to the sealing cover (7) by a fixing screw (71). A sealing ring (6) is provided between the sealing cover (7) and the container (2). The sealing cover (7) and the container (2) form a sealed cavity (3). A sleeve (21) communicating with the container is fixed on one side of the container (2). The piston (4) is slidably connected inside the sleeve (21). A sound outlet (22) is opened on the side wall of the container (2). A microphone (5) is provided inside the sound outlet (22). A drive assembly for driving the piston (4) to move back and forth is provided on the workbench (1). The measuring specimen device includes a measuring tube (81), a specimen (82) and a perforated plate bracket (83). The measuring tube (81) is installed above the container (2), and the specimen (82) is fixed inside the measuring tube (81) by the perforated plate bracket (83). The drive assembly includes a motor (9) fixed to the bottom of the worktable (1). The output shaft of the motor (9) extends through the worktable (1) to the top of the worktable (1). An eccentric wheel (91) is provided on the output shaft of the motor (9). An annular groove (911) is provided on the upper surface of the eccentric wheel (91). A piston rod (41) is fixed on the piston (4). A movable rod (42) is fixed at the end of the piston rod (41) away from the piston (4). The movable rod (42) is slidably connected in the annular groove (911). The piston rod (41) is provided with a heat dissipation assembly, which includes an annular plate (411) fixed on the piston rod (41). Two symmetrically arranged connecting plates (412) are fixed on the annular plate (411), and a heat dissipation plate (43) is fixed at one end of the connecting plate (412) away from the annular plate (411). The heat sink (43) is provided with a plurality of first slide rails (431) and second slide rails (432), which are spaced apart. A first slide rod (433) and a second slide rod (434) are slidably connected inside the first slide rail (431) and the second slide rail (432), respectively. Two heat-absorbing plates (435) are rotatably connected to the first slide rod (433) by a torsion spring. The end of the heat-absorbing plate (435) away from the first slide rod (433) is rotatably connected to the second slide rod (434). On the heat sink (43), a first metal sheet (4351) and a second metal sheet (4352) are respectively fixed on the two heat absorption plates (435). A third metal sheet (4311) is provided on the heat sink (43) at a position corresponding to the first metal sheet (4351) and the second metal sheet (4352). A first semiconductor (436) is provided between the third metal sheet (4311) and the first metal sheet (4351), and a second semiconductor (437) is provided between the third metal sheet (4311) and the second metal sheet (4352). An electromagnet (4312) is embedded in the end of the first slide rail (431) away from the heat sink (43), and a permanent magnet (4331) is provided on the first slide rod (433). The electromagnet (4312) and the permanent magnet (4331) are magnetically opposite on the side that are close to each other. The output shaft of the motor (9) is provided with a heat dissipation effect adjustment component. The heat dissipation effect adjustment component includes a hollow cylinder (10) fixed on the output shaft of the motor (9). A varistor (101) is provided at the end of the hollow cylinder (10) away from the output shaft of the motor (9). The varistor (101) and the electromagnet (4312) are connected in series. A metal ball (103) is fixed at the end of the hollow cylinder (10) near the output shaft of the motor (9) by an elastic rope (102).

2. The system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency according to claim 1, characterized in that, A stroke adjustment component is provided between the eccentric wheel (91) and the output shaft of the motor (9). The stroke adjustment component includes a U-shaped frame (92) fixed on the output shaft of the motor (9). A movable block (921) is slidably connected inside the U-shaped frame (92). The eccentric wheel (91) is located on the movable block (921).

3. The system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency according to claim 2, characterized in that, The U-shaped frame (92) is provided with a vibration damping component, which includes a counterweight (93) slidably connected to the U-shaped frame (92). Both the counterweight (93) and the movable block (921) are provided with racks (94). A central shaft (95) is fixed at the center of the U-shaped frame (92). A spur gear (951) that meshes with the rack (94) is rotatably connected to the central shaft (95). Both the counterweight (93) and the movable block (921) are provided with through slots (96) through which the rack (94) can pass.

4. The system for measuring the alternating flow resistance of sound-absorbing materials with adjustable motion frequency according to claim 1, characterized in that, The bottom of the movable rod (42) is provided with a spherical groove, and a ball bearing (421) is provided in the spherical groove.

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