Integrated variable air pressure acoustic impedance tube testing device

Abstract

The utility model discloses an integrated variable air pressure acoustic impedance tube testing device which comprises an impedance tube, one end of the impedance tube is provided with a loudspeaker, and the other end of the impedance tube is provided with a blind plate. Two microphones are mounted on the impedance tube in a sealing manner; a barometer, an air valve and a pressure release valve are further mounted on the impedance tube, and the air valve is connected with a double-head air pump; the loudspeaker is connected with the signal generator through the first signal amplifier; the microphone is connected with the second signal amplifier and then connected with the data acquisition card, and acquired data are imported into the computer. The number of the impedance tubes is one or two, when the number of the impedance tubes is one, the sample is located in the impedance tubes and located between the microphone far away from the loudspeaker and the blind plate, when the number of the impedance tubes is two, the two impedance tubes are connected through the flange plate, and the sample is installed at the connecting position. According to the utility model, through the air valve and the double-head air pump, the air pressure in the impedance tube is adjusted according to the use requirements, so that acoustic performance parameters such as the sound absorption coefficient and the sound reduction index of a measured material under different pressure intensities are measured.

Description

Technical Field

[0001] The utility model relates to the technical field of acoustic testing, in particular to an integrated variable air pressure acoustic impedance tube testing device. Background Art

[0002] Impedance tubes are currently widely used to test the sound absorption, sound insulation, and transmission loss of various acoustic materials. They play a crucial role in evaluating sound absorption and noise reduction in industries such as automotive, high-speed rail, aviation, and home appliances. Based on the measurement principle, impedance tube testing methods include the standing wave ratio method and the transfer function method.

[0003] The sound absorption performance of the same acoustic material is related to the pressure it is in. The impedance tubes currently developed are all designed to test acoustic materials under normal atmospheric pressure. For finished products made of materials whose working environment has a pressure different from atmospheric pressure, such as aviation equipment and automobile tires, the existing impedance tubes can no longer meet the requirements of measuring their sound absorption performance in complex environments. Utility Model Content

[0004] In view of the shortcomings in the prior art, the present invention provides an integrated variable air pressure acoustic impedance tube testing device to solve the problem that the impedance tube can only be tested for corresponding product performance at standard atmospheric pressure during use.

[0005] The utility model achieves the above technical objectives through the following technical means.

[0006] An integrated variable air pressure acoustic impedance tube testing device comprises an impedance tube, a loudspeaker is mounted on one end of the impedance tube, and a blind plate is mounted on the other end;

[0007] Two microphones are sealed and installed on the impedance tube;

[0008] The impedance tube is also equipped with a pressure gauge, an air valve and a pressure relief valve, and the air valve is connected to the double-head air pump;

[0009] The loudspeaker is connected to the signal generator via the first signal amplifier; the microphone is connected to the second signal amplifier and then to the data acquisition card to import the acquired data into the computer.

[0010] In the above technical solution, the number of the impedance tubes is 2, and the two impedance tubes are connected by a flange, and a sample is installed at the connection.

[0011] In the above technical solution, the number of the impedance tube is 1, and the sample is placed inside the impedance tube through a sample holder. The sample is located between the microphone and the blind plate away from the speaker.

[0012] In the above technical solution, the speaker is covered with a sound-absorbing sponge and placed in an insulating box.

[0013] In the above technical solution, the microphone is connected by a double ferrule.

[0014] In the above technical solution, a base is clamped at the lower portion of the impedance tube.

[0015] In the above technical solution, the impedance tube is made of aluminum cylinder.

[0016] In the above technical solution, small holes are provided at the installation locations of the pressure gauge, the air valve and the pressure relief valve, and the diameter of the small holes is less than 5% of the inner diameter of the impedance tube.

[0017] In the above technical solution, the flange is matched with the O-ring through a groove.

[0018] In the above technical solution, one end of the impedance tube on which the blind plate is installed is provided with a flange, and the flange is matched with an O-ring through a groove.

[0019] The beneficial effects of the utility model are:

[0020] (1) The utility model uses an air valve and a double-head air pump to adjust the air pressure inside the impedance tube according to the use requirements, and maintains the stability of the adjusted air pressure through good sealing, thereby measuring acoustic performance parameters such as the sound absorption coefficient and sound insulation of the measurement material under different pressures. The air pressure range is determined by the sealing condition, the working conditions of the sensor, and the strength of the tube wall.

[0021] (2) The utility model adopts the technical means of combining pressure regulation and sealing, and has the characteristics of simple structure and installation, and easy use and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an exploded view of the variable air pressure acoustic impedance tube testing device described in Example 1 of the present utility model;

[0023] Figure 2 Dimensional drawing of the variable air pressure acoustic impedance tube testing device described in Example 1 of the present utility model;

[0024] Figure 3 This is an exploded view of the variable air pressure acoustic impedance tube testing device described in Example 2 of the present utility model;

[0025] Figure 4 This is a dimensional diagram of the variable air pressure acoustic impedance tube testing device described in Example 2 of the present utility model;

[0026] Figure 5 This is a partial schematic diagram of the loudspeaker of the present invention;

[0027] In the figure: 1. loudspeaker; 2. loudspeaker base; 31. first air valve; 32. second air valve; 41. first air pressure gauge; 42. second air pressure gauge; 51. first microphone; 52. second microphone; 53. third microphone; 54. fourth microphone; 61. first pressure relief valve; 62. second pressure relief valve; 71. first base; 72. second base; 73. third base; 74. fourth base; 8. blind plate; 91. first impedance tube; 92. second impedance tube; 10. sample rack; 11. sound-absorbing sponge; 12. insulation box; 13. sample. DETAILED DESCRIPTION

[0028] The following will be combined with the accompanying drawings in the examples of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1

[0030] like Figure 1 As shown, an integrated variable air pressure acoustic impedance tube testing device includes two impedance tubes, namely a first impedance tube 91 and a second impedance tube 92, wherein one impedance tube is provided with a flange at one end, and the other impedance tube is provided with flanges at both ends, and the flanges are matched with grooves and O-rings to achieve good sealing; the two impedance tubes are connected through the flanges, and a sample is installed at the connection between the two impedance tubes; a loudspeaker 1 is installed at the other end of the impedance tube with a flange at one end, and the loudspeaker 1 is connected to the signal generator through a first signal amplifier, and the first signal amplifier and signal generator are not shown in the figure; the other end of the impedance tube with flanges at both ends is connected to a blind plate 8 through a flange.

[0031] Two microphones are sealed and mounted on each impedance tube, for example, using a double ferrule connection to enhance airtightness. Specifically, first microphone 51 and second microphone 52 are mounted on first impedance tube 91, while third microphone 53 and fourth microphone 54 are mounted on second impedance tube 92. The microphones are connected to a second signal amplifier and then to a data acquisition card, which then imports the collected data into a computer.

[0032] The two impedance tubes are also equipped with small holes in their walls for installing pressure gauges, air valves, and pressure relief valves, respectively. Specifically, the first impedance tube 91 is equipped with a first pressure gauge 41, a first air valve 31, and a first pressure relief valve 61, while the second impedance tube 92 is equipped with a second pressure gauge 42, a second air valve 32, and a second pressure relief valve 62. The diameter of the small holes in the impedance tube walls connecting the pressure gauges, air valves, and pressure gauges is less than 5% of the impedance tube's inner diameter. The air valves are connected to a double-headed air pump, which, connected to the first and second air valves 31 and 32, pumps air into and out of the two impedance tubes to increase and decrease pressure. The first and second pressure gauges 41 and 42 display the real-time air pressure inside the impedance tubes to meet the experimental requirements. If the air pressure inside the impedance tubes is too high, posing a safety hazard, the first and second pressure relief valves 61 and 62 automatically vent air to reduce the pressure inside the impedance tubes.

[0033] like Figure 5 As shown, the speaker 1 is connected to the impedance tube via the speaker base 2 , the speaker 1 and the impedance tube are coaxially arranged, and the speaker 1 is covered by a sound-absorbing sponge 11 and placed in an insulating box 12 .

[0034] The lower portion of each impedance tube is respectively connected to two bases. Specifically, the lower portion of the first impedance tube 91 is respectively connected to the first base 71 and the second base 72 , and the lower portion of the second impedance tube 92 is respectively connected to the third base 73 and the fourth base 74 .

[0035] In this embodiment, the impedance tube is an aluminum cylindrical tube. It should be noted that the circular impedance tube is used here only for the convenience of describing this application, and does not indicate that the impedance tube must have this specific shape.

[0036] This embodiment is used to measure the sound insulation of the sample. Figure 1 Assemble in this way, place the sample at the connection between the two impedance tubes, and seal the gaps around the sample with sealants such as vaseline, silicone grease, silicone rubber, etc.

[0037] See also Figure 2 , let the distance between the first microphone 51 and the second microphone 52 be S1, the distance between the second microphone 52 and the sample be L1, the distance between the sample and the third microphone 53 be L2, and the distance between the third microphone 53 and the fourth microphone 54 be S2.

[0038] After checking that the holes on the impedance tube are sealed properly, open the first air valve 31 and the second air valve 32, and use the double-headed air pump to pump air in or out until the inside of the impedance tube reaches the required pressure. Once the pressure stabilizes, close the air pump and the air valves. Use the signal generator to make the speaker 1 emit a sound signal, generating a stable one-dimensional plane wave inside the impedance tube. Calculate the sound pressure transmission coefficient t based on the sound pressures p1, p2, p3, and p4 measured by the first microphone 51, the second microphone 52, the third microphone 53, and the fourth microphone 54. p :

[0039]

[0040] Among them: intermediate amount f is the sound frequency (Hz), obtained by the signal generator; c is the speed of the sound wave in the impedance tube (m / s), which is calculated from the speed of sound in a vacuum environment;

[0041] Then the sound insulation of the sample is obtained:

[0042]

[0043] After the measurement is completed, disconnect the air valve from the air pump, open the air valve, and balance the air pressure in the impedance tube; finally, take out the sample.

[0044] Example 2

[0045] With respect to Example 1, Figure 3 As shown, an integrated variable air pressure acoustic impedance tube testing device of this embodiment includes only one impedance tube, namely a first impedance tube 91. A first microphone 51 and a second microphone 52 are mounted on the first impedance tube 91. A first barometer 41, a first air valve 31, and a first pressure relief valve 61 are mounted on the first impedance tube 91. The lower portion of the first impedance tube 91 is respectively connected to the first base 71 and the second base 72. A loudspeaker 1 is mounted on one end of the first impedance tube 91, and a flange at the other end of the first impedance tube 91 is connected to a blind plate 8. The sample is placed inside the first impedance tube 91 through a sample holder 10. The sample is located between the second microphone 52 and the blind plate 8. The sample holder 10 is made of rigid material and is firmly fixed to the impedance tube when in use. The parameters, settings, working principles, functions, and controls of each component are the same as those in Example 1 and will not be repeated here.

[0046] This embodiment is used to measure the sound absorption coefficient of a sample. There are two methods. The operating frequency ranges of the two methods are calculated according to GB / T 18696.2-2002 and GB T 18696.1-2004.

[0047] (1) Transfer function method

[0048] according to Figure 3The impedance tube is assembled in the following manner: the sample to be tested is placed inside the impedance tube along with the sample holder 10; the gaps around the sample can be sealed with a sealant such as vaseline, silicone grease, silicone rubber, etc.

[0049] Ginseng Figure 4 , let the distance between the first microphone 51 and the second microphone 52 be S1, the distance between the second microphone 52 and the sample be d, and the inner diameter of the impedance tube be r.

[0050] After checking that the holes on the impedance tube are properly sealed, the first air valve 31 is opened, and the dual-head air pump operates to draw air in or out until the desired pressure is reached inside the impedance tube. Once the pressure stabilizes, the air pump and valve are closed. A signal generator is used to cause the speaker 1 to emit a sound signal, generating a stable one-dimensional plane wave inside the impedance tube. The sound pressure at the location is measured by the first microphone 51 and the second microphone 52. This is amplified by a second signal amplifier, input to a data acquisition card, and then into a computer. Spectral analysis is used to calculate the transfer function between the two microphones, which is then used to calculate the normal-incidence absorption coefficient (the specific calculation process follows existing techniques).

[0051] (2) Standing Wave Ratio Method

[0052] according to Figure 3 The impedance tube is assembled in the following manner: the sample to be tested is placed inside the impedance tube along with the sample holder 10; the gaps around the sample can be sealed with a sealant such as vaseline, silicone grease, silicone rubber, etc.

[0053] After checking that the sealing of each hole on the impedance tube is in good condition, open the first air valve 31 and use the double-head air pump to operate the air intake or exhaust operation to allow the air pressure inside the impedance tube to reach the required environment. After the air pressure stabilizes, close the air pump and the air valve; use the signal generator to make the speaker 1 emit a sound signal, generating a stable one-dimensional plane wave inside the impedance tube. The speaker releases a normal-incident sinusoidal plane wave. After the incident wave contacts the measuring piece, it forms a reflected wave. The reflected wave and the incident wave overlap in the impedance tube body to form a standing wave. The minimum sound pressure p is obtained through the first microphone 51 and the second microphone 52. min and extreme sound pressure p max , we get the standing wave ratio n:

[0054]

[0055] According to the sound absorption coefficient formula:

[0056]

[0057] Where α is the sound absorption coefficient;

[0058] After the measurement is completed, disconnect the air valve from the air pump, open the air valve, and balance the air pressure in the impedance tube; finally, take out the sample.

[0059] In the description of this application, it should be noted that the terms "upper," "lower," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral connections; mechanical connections, electrical connections, direct connections, indirect connections through an intermediary, or internal connections between two components. A person of ordinary skill in the art will understand the specific meanings of the above terms in this application based on the specific circumstances. A device includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the elements.

[0060] The foregoing description is intended only to provide specific embodiments of the present application, which will enable those skilled in the art to understand and implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. An integrated variable air pressure acoustic impedance tube test device, characterized in that: It comprises an impedance tube, a loudspeaker (1) is mounted on one end of the impedance tube, and a blind plate (8) is mounted on the other end; Two microphones are sealed and installed on the impedance tube; The impedance tube is also equipped with a pressure gauge, an air valve and a pressure relief valve, and the air valve is connected to a double-head air pump; The loudspeaker (1) is connected to a signal generator via a first signal amplifier; after the microphone is connected to the second signal amplifier, it is connected to a data acquisition card to import the acquired data into a computer.

2. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The number of the impedance tubes is 2, and the two impedance tubes are connected by a flange, and a sample is installed at the connection.

3. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The number of the impedance tube is 1, and the sample is placed inside the impedance tube through a sample holder (10), and the sample is located between a microphone far away from the speaker (1) and a blind plate (8).

4. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The loudspeaker (1) is covered with a sound-absorbing sponge (11) and is placed in an insulating box (12).

5. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The microphone is connected by a double ferrule.

6. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The lower part of the impedance tube is clamped with a base.

7. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The impedance tube is in the shape of an aluminum cylinder.

8. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: The installation positions of the pressure gauge, the air valve and the pressure relief valve are provided with small holes, and the diameter of the small holes is less than 5% of the inner diameter of the impedance tube.

9. The integrated variable air pressure acoustic impedance tube testing device according to claim 2, characterized in that: The flange is matched with an O-ring through a groove.

10. The integrated variable air pressure acoustic impedance tube testing device according to claim 1, characterized in that: One end of the impedance tube on which the blind plate (8) is mounted is provided with a flange, and the flange is matched with an O-ring through a groove.

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