Motion-frequency-adjustable system for measuring alternating flow resistance of sound absorption material

Abstract

The invention belongs to the technical field of sound absorption material flow resistance measurement, and particularly relates to a sound absorption material alternating flow resistance measurement system with adjustable motion frequency, which comprises a measurement closed cavity device, the measurement 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 closed cavity is fixed above the container, and the piston is fixed above the closed cavity. The top of the container is detachably and fixedly connected with a sealing cover through a fixing screw, a sealing ring is arranged between the sealing cover and the container, the sealing cover and the container form a closed cavity, a sleeve communicated with the container is fixed to one side of the container, a piston is connected into the sleeve in a sealed and sliding mode, a sound outlet is formed in the side wall of the container, and the sound outlet is communicated with the container. And a microphone is arranged in the sound outlet. The stability of the piston during reciprocating motion is ensured by arranging the anti-vibration assembly, the measurement precision is improved, the influence of the temperature change in the closed cavity on the measurement result is avoided by arranging the heat dissipation assembly, and the measurement precision is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sound absorption material flow resistance measurement, and particularly relates to a system for measuring sound absorption material alternating flow resistance with adjustable motion frequency. BACKGROUND

[0002] As one of the main means of sound field regulation, the sound absorption performance of a material is increasingly concerned by acoustic workers, and the flow resistance of the material is a basic parameter reflecting the internal porosity and partial structural characteristics of the material, and the flow resistance can be applied to establish the relationship between the structure of the material and some acoustic characteristics (such as sound absorption characteristics, attenuation characteristics, etc.) of the material, and the precondition for designing and producing high-performance sound absorption materials is to accurately and efficiently measure the flow resistance characteristics thereof.

[0003] The sound absorption material flow resistance measurement methods include direct current method, impedance tube method, and alternating current type measurement device method, etc., wherein the alternating current type measurement device method drives a piston to make reciprocating linear motion through a motor driving eccentric wheel to generate alternating airflow in a test cavity, and the sound pressure level in the wall is measured through a microphone, which is simple and convenient to operate, has higher resolution and better response characteristics than the traditional differential pressure gauge for measuring differential pressure, and has higher accuracy of measured alternating gas pressure, thereby ensuring the measurement accuracy of the flow resistance.

[0004] The existing device still has the following deficiencies:

[0005] 1. When the motor drives the eccentric wheel to rotate, the eccentric wheel often vibrates due to the unbalanced weight on both sides of the motor output shaft, which causes the piston to move unstably, thereby affecting the accuracy of the measurement results.

[0006] 2. When the piston moves back and forth, heat is generated by high-speed friction between the piston and the side wall of the piston cylinder, and the heat increases the temperature of the air in the cavity, thereby affecting the volume of the air and the air pressure in the cavity, and thereby affecting the accuracy of the measurement results. SUMMARY

[0007] The present application aims to solve the problems in the above background art, and provides a system for measuring sound absorption material alternating flow resistance with adjustable motion frequency.

[0008] To achieve the above object, the present application adopts the following technical scheme: a system for measuring sound absorption material alternating flow resistance with adjustable motion frequency, comprising:

[0009] The utility model provides a measuring closed cavity device, which 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 container top is detachably fixedly connected with the sealing cover 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, one side of the container is fixedly connected with a sleeve in communication with the container, the sleeve is slidably connected with the piston in a sealed manner, a sound outlet is formed in the side wall of the container, and a microphone is arranged in the sound outlet, and a driving assembly for driving the piston to reciprocate is arranged on the workbench.

[0010] The utility model provides a measuring test piece device, which comprises a measuring tube, a test piece and a perforated plate support, the measuring tube is installed above the container, and the test piece is fixed in the measuring tube through the perforated plate support.

[0011] Further, the driving assembly comprises a motor fixed to the bottom of the workbench, the output shaft of the motor extends through the workbench to above the workbench, an eccentric wheel is arranged on the output shaft of the motor, an annular groove is formed in the upper surface of the eccentric wheel, a piston rod is fixed to the piston, a movable rod is fixed to the end of the piston rod away from the piston, and the movable rod is slidably connected in the annular groove.

[0012] Further, a stroke adjusting assembly is arranged between the eccentric wheel and the output shaft of the motor, the stroke adjusting assembly comprises a U-shaped frame fixed to the output shaft of the motor, a movable block is slidably connected in the U-shaped frame, and the eccentric wheel is arranged on the movable block.

[0013] Further, a shockproof assembly is further arranged in the U-shaped frame, the shockproof assembly comprises a counterweight slidably connected in the U-shaped frame, a rack is arranged on the counterweight and the movable block, a central shaft is fixed to the center of the U-shaped frame, a cylindrical gear meshing with the rack is rotatably connected to the central shaft, and a through groove is formed in the counterweight and the movable block and can be passed through by the rack.

[0014] Further, a spherical groove is formed in the bottom of the movable rod, and a ball is arranged in the spherical groove.

[0015] Further, a heat dissipation assembly is arranged on the piston rod, the heat dissipation assembly comprises an annular plate fixed to the piston rod, two symmetrical connecting plates are fixed to the annular plate, and heat dissipation plates are fixed to the ends of the connecting plates away from the annular plate.

[0016] Further, a plurality of first sliding rails and second sliding rails are arranged on the heat dissipation plate, the first sliding rails and the second sliding rails are arranged at intervals, and a first sliding rod and a second sliding rod are respectively slidably connected in the first sliding rails and the second sliding rails, two heat absorbing plates are rotatably connected to the first sliding rod through a torsion spring, one end of the heat absorbing plate away from the first sliding rod is rotatably connected to the second sliding rod, a first metal sheet and a second metal sheet are respectively fixed on the two heat absorbing plates, a third metal sheet is arranged on the heat dissipation plate at a position corresponding to the first metal sheet and the second metal sheet, a first semiconductor is arranged between the third metal sheet and the first metal sheet, and a second semiconductor is arranged between the third metal sheet and the second metal sheet.

[0017] Further, an electromagnet is embedded in one end of the first sliding rail away from the heat dissipation plate, a permanent magnet is arranged on the first sliding rod, and the sides of the electromagnet and the permanent magnet close to each other are magnetically opposite.

[0018] Further, a heat dissipation effect adjusting assembly is arranged on the output shaft of the motor, the heat dissipation effect adjusting assembly comprises a hollow cylinder fixed on the output shaft of the motor, a pressure sensitive resistor is arranged on one end of the hollow cylinder away from the output shaft of the motor, the pressure sensitive resistor and the electromagnet are connected in series, and a metal ball is fixed to one end of the hollow cylinder close to the output shaft of the motor through an elastic rope.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1、The present application sets up the anti-vibration assembly, sets up the counterweight in the U-shaped frame to balance the weight of the movable block and the eccentric wheel, balances the weight on both sides of the motor output shaft, prevents vibration caused by unbalanced weight on both sides of the motor output shaft when the eccentric wheel rotates, and ensures the stability of the piston reciprocating movement, thereby improving the measurement accuracy.

[0021] 2、The present application sets up the rack and the column gear, adjusts the position of the eccentric wheel to change the piston stroke, and the position of the counterweight changes synchronously with the position of the eccentric wheel under the cooperation of the column gear and the rack, so that the position of the counterweight does not need to be adjusted separately, thereby improving the work efficiency.

[0022] 3、The present application sets up the heat dissipation assembly, the piston reciprocating movement, the sleeve is cooled by the heat dissipation assembly, the heat generated by the friction between the piston and the sleeve is avoided to change the temperature in the closed cavity, thereby avoiding the influence of the temperature change in the closed cavity on the measurement result, and improving the measurement accuracy.

[0023] 4、The present application sets up the heat dissipation effect adjusting assembly, the motor speed is greater, the piston reciprocating generates more heat, the heat absorption plate heat dissipation efficiency is higher, the motor speed is smaller, the piston reciprocating generates less heat, and the heat dissipation efficiency of heat absorption plate also changes small, thereby ensuring that the gas temperature in the closed cavity remains stable when the motor rotates at different speeds, avoiding the influence of temperature change on the measurement result. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a kind of whole structure schematic diagram of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0025] Figure 2 It is a top view structure schematic diagram of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0026] Figure 3 It is Figure 2 A-A direction section view in it;

[0027] Figure 4 It is Figure 3 Enlarged view at B in it;

[0028] Figure 5 It is Figure 3 Enlarged view at C in it;

[0029] Figure 6 It is a U-shaped frame internal structure schematic diagram of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0030] Figure 7 It is a measuring test piece device structure schematic diagram of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0031] Figure 8 It is a whole structure schematic diagram of the heat dissipation assembly of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0032] Figure 9 It is a part structure schematic diagram of the heat dissipation assembly of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0033] Figure 10 It is a structure schematic diagram of the state of heat dissipation assembly corresponding to different motor speeds in the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application;

[0034] Figure 11 It is a current direction schematic diagram of the heat dissipation assembly of the measuring sound-absorbing material alternating flow resistance system of adjustable motion frequency provided by the present application.

[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 particular, the motor 9 rotates the eccentric wheel 91, which drives the piston rod 41 and the piston 4 to reciprocate in the sleeve 21 under the action of the annular groove 911 and the movable rod 42. The sliding friction between the bottom of the movable rod 42 and the bottom of the annular groove 911 is converted into rolling friction by the ball 421, thereby reducing the friction between the movable rod 42 and the annular groove 911, making the movement of the piston 4 in the sleeve 21 more stable, and reducing the wear of the movable rod 42 and the eccentric wheel 91, prolonging the service life of the device.

[0045] The eccentric wheel 91 and the output shaft of the motor 9 are provided with a stroke adjusting assembly. The stroke adjusting assembly includes a U-shaped frame 92 fixed to the output shaft of the motor 9, and a movable block 921 slidingly connected in the U-shaped frame 92. A control assembly is arranged in the U-shaped frame 92 for controlling the movement of the movable block 921. The control assembly is of existing technology and will not be described here. The eccentric wheel 91 is arranged on the movable block 921.

[0046] In particular, the motor 9 rotates the eccentric wheel 91, which drives the piston rod 41 and the piston 4 to reciprocate in the sleeve 21 under the action of the annular groove 911 and the movable rod 42. The sliding friction between the bottom of the movable rod 42 and the bottom of the annular groove 911 is converted into rolling friction by the ball 421, thereby reducing the friction between the movable rod 42 and the annular groove 911, making the movement of the piston 4 in the sleeve 21 more stable, and reducing the wear of the movable rod 42 and the eccentric wheel 91, prolonging the service life of the device.

[0047] The U-shaped frame 92 is further provided with an anti-vibration assembly. The anti-vibration assembly includes a counterweight 93 slidingly connected in the U-shaped frame 92. The counterweight 93 is used to adjust the balance of the U-shaped frame 92, to avoid the U-shaped frame 92 tilting due to excessive weight on one end, and to avoid the eccentric wheel 91 vibrating due to the tilting of the U-shaped frame 92 when rotating, thereby ensuring the stable rotation of the eccentric wheel 91 around the output shaft of the motor 9, and ensuring the stability of the movement of the piston 4. A rack 94 is arranged on the counterweight 93 and the movable block 921. A central shaft 95 is fixed at the center of the U-shaped frame 92. A cylindrical gear 951 is rotatably connected to the central shaft 95 and engages with the rack 94. A through groove 96 is formed in the counterweight 93 and the movable block 921 for the rack 94 to pass through. When adjusting the position of the movable block 921, the counterweight 93 moves synchronously with the movable block 921 under the cooperation of the cylindrical gear 951 and the rack 94, to ensure the balance of the two ends of the U-shaped frame 92, without the need to separately adjust the position of the counterweight 93, thereby improving the working efficiency.

[0048] The measuring device includes a measuring tube 81, a test piece 82, and a perforated plate support 83. When measuring the test piece 82, the sealing cover 7 is removed, the measuring tube 81 is installed above the container 2, and then the test piece 82 is fixed in the measuring tube 81 by the perforated plate support 83.

[0049] The piston rod 41 is provided with a heat dissipation assembly, the heat dissipation assembly comprises an annular plate 411 fixed on the piston rod 41, two symmetrically arranged connecting plates 412 are fixed on the annular plate 411, a heat dissipation plate 43 is fixed on the end of the connecting plate 412 away from the annular plate 411, a plurality of first sliding rails 431 and second sliding rails 432 are arranged on the heat dissipation plate 43, the first sliding rails 431 and the second sliding rails 432 are arranged at intervals, first sliding rods 433 and second sliding rods 434 are respectively and slidably connected in the first sliding rails 431 and the second sliding rails 432, two heat absorption plates 435 are rotatably connected on the first sliding rod 433 through a torsion spring, the heat absorption plates 435 and the heat dissipation plate 43 are made of heat-conducting and non-conductive ceramic material, the end of the heat absorption plate 435 away from the first sliding rod 433 is rotatably connected to the second sliding rod 434, in the natural state of the torsion spring, the first sliding rod 433 and the second sliding rod 434 are respectively located on the side of the first sliding rail 431 and the second sliding rail 432 close to the heat dissipation plate 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 arranged on the heat dissipation plate 43 at a position corresponding to the first metal sheet 4351 and the second metal sheet 4352, a first semiconductor 436 is arranged between the third metal sheet 4311 and the first metal sheet 4351, and a second semiconductor 437 is arranged between the third metal sheet 4311 and the second metal sheet 4352.

[0050] As shown in Figure 11 , in specific work, the heat dissipation assembly is connected with current, and the arrow direction in the figure represents the direction of the current. According to the Peltier effect, when the current passes through the loop composed of two different conductors, the joints will appear heat absorption and heat release phenomenon respectively. Specifically, when the current flows from one conductor to another, one joint will absorb heat, and the other joint will release heat. In the embodiment, when the current flows from the first semiconductor 436 to the second semiconductor 437, heat is released, and when the current flows from the second semiconductor 437 to the first semiconductor 436, heat is absorbed, so that the heat absorption plate 435 can dissipate heat for the sleeve 21, and avoid the heat generated by the friction between the piston 4 and the sleeve 21 when reciprocating to affect the measurement result.

[0051] The electromagnet 4312 is embedded in one end of the first sliding rail 431 away from the heat dissipation plate 43, the permanent magnet 4331 is arranged on the first sliding rod 433, the electromagnet 4312 and the permanent magnet 4331 are opposite to each other in magnetic property, when the electromagnet 4312 is electrified, the electromagnet 4312 generates an attractive force to the permanent magnet 4331, the greater the current of the electromagnet 4312, the stronger the attractive force of the electromagnet 4312 to the permanent magnet 4331, the attractive force of the electromagnet 4312 to the permanent magnet 4331 drives the first sliding rod 433 to move to the direction close to the sleeve 21, the output shaft of the motor 9 is provided with a heat dissipation effect adjusting assembly, the heat dissipation effect adjusting assembly comprises a hollow cylinder 10 fixed to the output shaft of the motor 9, the hollow cylinder 10 is provided with a piezoresistor 101 at one end away from the output shaft of the motor 9, the piezoresistor 101 is connected in series with the electromagnet 4312, the one end of the hollow cylinder 10 close to the output shaft of the motor 9 is fixed with a metal ball 103 through an elastic rope 102;

[0052] In the non-working state, the metal ball 103 is separated from the piezoresistor 101 under the tension of the elastic rope 102, the piezoresistor 101 is not pressed, the resistance value of the piezoresistor is in a high state, the current passing through the electromagnet 4312 is small, the attractive force of the electromagnet 4312 to the permanent magnet 4331 is relatively small, when the motor 9 rotates, the hollow cylinder 10 rotates synchronously, the metal ball 103 contacts and presses the piezoresistor 101 under the action of centrifugal force, the greater the rotating speed of the motor 9, the greater the centrifugal force of the metal ball 103, the greater the pressure of the metal ball 103 to the piezoresistor 101, the smaller the resistance value of the piezoresistor 101, the greater the current passing through the electromagnet 4312, the greater the attractive force of the electromagnet 4312 to the permanent magnet 4331, the greater the distance of the first sliding rod 433 moving to the direction close to the sleeve 21, the better the heat dissipation effect of the heat dissipation plate 435, when the motor 9 stops rotating, the metal ball 103 is separated from the piezoresistor 101, the resistance value of the piezoresistor 101 increases, the current passing through the electromagnet 4312 decreases, the attractive force of the electromagnet 4312 to the permanent magnet 4331 decreases, the first sliding rod 433 returns to the initial position under the action of the torsional spring;

[0053] In the specific working process, the greater the rotating speed of the motor 9, the greater the frequency of the piston 4 reciprocating, the greater the heat generated by the friction between the piston 4 and the sleeve 21, at the same time, the greater the rotating speed of the motor 9, the greater the attractive force of the electromagnet 4312 to the permanent magnet 4331, thereby the first sliding rod 433 is attracted to the direction close to the sleeve 21, the heat absorption plate 435 is close to the sleeve 21 to increase the heat dissipation effect, that is, the greater the rotating speed of the motor 9, the more heat generated by the piston 4 reciprocating, the higher the heat dissipation efficiency of the heat absorption plate 435, the smaller the rotating speed of the motor 9, the less heat generated by the piston 4 reciprocating, the lower the heat dissipation efficiency of the heat absorption plate 435, thereby the temperature of the gas in the sealed cavity 3 is kept stable when the motor 9 rotates at different rotating speeds, the influence of temperature change on the measurement result is avoided.

[0054] The specific steps of the present application in making flow resistance measurement are as follows:

[0055] S1. With the measuring tube 81 and the sealing cover 7 not installed, start the motor 9, measure the background noise sound pressure level Lp,b and the static pressure Ps of the working piston 4;

[0056] S2. Fix the test piece 82 with the perforated plate support 83 at the lower end of the measuring tube 81, then install it on the container 2, adjust the motion frequency and stroke hs of the piston 4, and after the piston 4 moves stably, measure the frequency f of the piston reciprocating motion, the stroke hs and the sound pressure level Lp,s in the closed cavity 3;

[0057] S3. Replace the measuring tube 81 and the test piece 82 with the sealing cover 7, keep the frequency of the piston 4 motion unchanged, adjust the stroke ht of the piston 4, and after the piston 4 moves stably, measure the sound pressure level Lp,t in the closed cavity 3 when the end is sealed;

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

[0059]

[0060] In the formula, k' is the effective specific heat ratio of air, k' = 1.37 under standard temperature and humidity and standard atmosphere;

[0061] S5. Test the effectiveness of the above measurement by using the following two formulas:

[0062]

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

[0064] If the above two formulas are not met, change the motion frequency of the piston 4 or adjust the motion stroke of the piston 4 to retest until the requirements are met.

[0065] The above is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A tunable frequency motion measuring sound absorbing material alternating flow resistance system, characterized in that, Include: The measuring closed cavity device includes a workbench (1), a container (2), a closed 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 container (2) top is detachably fixedly connected with sealing cover (7) through fixed screw (71), the sealing cover (7) and the container (2) are provided with sealing ring (6), the sealing cover (7) and the container (2) constitute a closed cavity (3), one side of the container (2) is fixed with sleeve (21) communicated with the container, the sleeve (21) is sealingly connected with the piston (4) in the sleeve (21), the container (2) side wall is provided with sound outlet (22), the sound outlet (22) is provided with microphone (5), the workbench (1) is provided with driving assembly for driving piston (4) reciprocating movement; The measuring test piece device includes a measuring pipe (81), a test piece (82) and a perforated plate support (83), the measuring pipe (81) is installed above the container (2), the test piece (82) is fixed in the measuring pipe (81) through the perforated plate support (83).

2. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 1, characterized in that, The driving assembly includes a motor (9) fixed on the bottom of the workbench (1), the output shaft of the motor (9) extends through the workbench (1) to above the workbench (1), the output shaft of the motor (9) is provided with an eccentric wheel (91), the upper surface of the eccentric wheel (91) is provided with an annular groove (911), the piston (4) is fixed with a piston rod (41), the end of the piston rod (41) away from the piston (4) is fixed with a movable rod (42), the movable rod (42) is slidingly connected in the annular groove (911).

3. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 2, characterized in that, The eccentric wheel (91) and the output shaft of the motor (9) are provided with a stroke adjusting assembly, the stroke adjusting assembly includes a U-shaped frame (92) fixed on the output shaft of the motor (9), the U-shaped frame (92) is slidingly connected with a movable block (921), and the eccentric wheel (91) is arranged on the movable block (921).

4. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 3, characterized in that, The U-shaped frame (92) is provided with a shockproof assembly, the shockproof assembly includes a counterweight block (93) slidingly connected in the U-shaped frame (92), the counterweight block (93) and the movable block (921) are provided with a rack (94), the center of the U-shaped frame (92) is fixed with a center shaft (95), the center shaft (95) is rotatably connected with a cylindrical gear (951) engaged with the rack (94), and the counterweight block (93) and the movable block (921) are provided with a through groove (96) through which the rack (94) passes.

5. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 2, characterized in that, The bottom of the movable rod (42) is provided with a spherical groove, and the spherical groove is provided with a ball (421).

6. A moving frequency adjustable measurement of sound absorbing material alternating flow resistance system according to claim 1, characterized in that, The piston rod (41) is provided with a heat dissipation assembly, the heat dissipation assembly 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 the end of the connecting plate (412) away from the annular plate (411) is fixed with a heat dissipation plate (43).

7. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 6, characterized in that, The heat dissipation plate (43) is provided with a plurality of first sliding rails (431) and second sliding rails (432), the first sliding rails (431) and the second sliding rails (432) are arranged at intervals, the first sliding rails (431) and the second sliding rails (432) are slidably connected with first sliding rods (433) and second sliding rods (434) respectively, the first sliding rods (433) are rotatably connected with two heat absorbing plates (435) through torsion springs, the heat absorbing plates (435) are rotatably connected with the second sliding rods (434) at the ends away from the first sliding rods (433), the heat absorbing plates (435) are fixed with first metal sheets (4351) and second metal sheets (4352) respectively, the heat dissipation plate (43) is provided with third metal sheets (4311) at positions corresponding to the first metal sheets (4351) and the second metal sheets (4352), the third metal sheets (4311) and the first metal sheets (4351) are provided with first semiconductors (436), and the third metal sheets (4311) and the second metal sheets (4352) are provided with second semiconductors (437).

8. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 7, characterized in that, The first sliding rails (431) are embedded with electromagnets (4312) at the ends away from the heat dissipation plate (43), the first sliding rods (433) are provided with permanent magnets (4331), and the electromagnets (4312) and the permanent magnets (4331) are opposite in magnetism on the sides close to each other.

9. A moving frequency adjustable measurement of the flow resistance of sound absorbing material system according to claim 8, characterized in that, The output shaft of the motor (9) is provided with a heat dissipation effect adjusting assembly, the heat dissipation effect adjusting assembly comprises a hollow cylinder (10) fixed to the output shaft of the motor (9), the hollow cylinder (10) is provided with a piezoresistor (101) at the end away from the output shaft of the motor (9), the piezoresistor (101) and the electromagnet (4312) are connected in series in circuit, and the hollow cylinder (10) is fixed with a metal ball (103) through an elastic rope (102) at the end close to the output shaft of the motor (9).

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