Helmholtz resonator and control method

Abstract

The invention provides a Helmholtz resonator and a control method, the Helmholtz resonator comprises a neck cavity and a resonant cavity, the neck cavity comprises at least two nested cylindrical cavity wall components; a first transmission mechanism is arranged, and the first transmission mechanism can drive the cylindrical cavity wall component to relatively move in the axis direction of the neck cavity; the resonant cavity comprises two opposite movable wall surfaces parallel to the central axis; a second transmission mechanism is arranged; and the second transmission mechanism can drive the two movable wall surfaces of the resonant cavity to relatively move along the direction of the second central axis. The technical scheme of the invention can adapt to the noise frequency change condition of the controlled space, and is widely applied to the technical field of vibration and noise reduction of the closed space.

Description

Technical Field

[0001] The invention relates to the technical field of vibration reduction and noise reduction, in particular to the technical field of vibration reduction and noise reduction of ships. Background Art

[0002] With the booming development of modern industry and transportation, the noise problem in enclosed spaces has become increasingly prominent. The noise in enclosed spaces such as pipelines, ship cabins, and car interiors will cause "acoustic fatigue" in related mechanical equipment, deteriorate the working environment, and reduce the work efficiency of personnel. In order to solve the noise problem, the technology of controlling and eliminating noise has been developed.

[0003] As a passive control technology with a simple structure and good noise attenuation ability within a specific frequency band, the Helmholtz resonator is widely used in the field of closed space noise control. The traditional Helmholtz sound absorption structure consists of a closed resonance cavity and a neck tube connected to the resonance cavity, which has a good absorption effect on low-frequency noise. When receiving external sound waves, the air in the neck of the Helmholtz sound absorption structure vibrates, and the air in the resonance cavity generates a restoring force, that is, the sound energy in the system is attenuated by the air movement in the neck of the resonator and adjusted by the stiffness of the air in the resonance cavity. If the frequency of the sound wave is equal to the natural frequency of the system, the neck air column will produce severe resonant vibration, overcome the friction resistance, and consume sound energy.

[0004] Traditional Helmholtz resonators have certain problems, namely, they can effectively absorb sounds near their resonance frequency, but the resonance frequency is determined at the beginning of the structural design of the Helmholtz resonator, resulting in a narrow sound absorption band and can only be used as a narrow-band low-frequency sound absorber. Summary of the invention

[0005] In order to solve the problem of narrow sound absorption frequency band of the existing Helmholtz resonator, the present invention provides a Helmholtz resonator and a control method.

[0006] The technical solution of the present invention is as follows:

[0007] A Helmholtz resonator comprises a neck cavity and a resonance cavity, wherein the neck cavity is connected to the resonance cavity, the neck cavity comprises a cylindrical cavity, and the resonance cavity comprises a rectangular cavity; the axis of the neck cavity is parallel to the connection direction between the neck cavity and the resonance cavity; the first central axis of the resonance cavity is parallel to the connection direction between the neck cavity and the resonance cavity, and the second central axis of the resonance cavity is perpendicular to the first central axis;

[0008] The neck cavity comprises at least two nested cylindrical cavity wall components; a first transmission mechanism is provided, and the first transmission mechanism can drive the cylindrical cavity wall component to move relatively along the axis direction of the neck cavity;

[0009] The resonance cavity comprises two opposite movable walls parallel to the central axis; a second transmission mechanism is provided; the second transmission mechanism can drive the two movable walls of the resonance cavity to move relative to each other along the direction of the second central axis.

[0010] Optionally, the second transmission mechanism drives the two movable walls to at least two positions: the first central axis is parallel to or coincides with the axis of the neck cavity.

[0011] Optionally, the Helmholtz resonator is provided with two cylindrical cavity wall components, and the natural frequency f of the Helmholtz resonator is r The control formula is:

[0012]

[0013] Among them, c is the speed of sound in the resonance cavity, S is the area of ​​one of the two movable walls, l is the distance between the two movable walls of the resonance cavity, (l1+l2) is the length of the neck cavity in the axial direction, l1 is the length of the cylindrical cavity wall component with a smaller inner diameter in the axial direction of the neck cavity, l2 is the length of the cylindrical cavity wall component with a larger inner diameter in the axial direction of the neck cavity, S2 is the area of ​​the cross section of the cylindrical cavity wall component with a larger inner diameter perpendicular to the axis of the neck cavity, S1 is the area of ​​the cross section of the cylindrical cavity wall component with a smaller inner diameter perpendicular to the axis of the neck cavity, and k=S1 / S2.

[0014] As mentioned above, the method for controlling the natural frequency of the Helmholtz resonator includes the following steps:

[0015] S1. Obtain frequency response data of the controlled space;

[0016] S2, judging whether the natural frequency of the Helmholtz resonator matches the target frequency of the controlled space, if the natural frequency of the Helmholtz resonator matches the target frequency of the controlled space, go to step S6; if the natural frequency of the Helmholtz resonator does not match the target frequency of the controlled space, go to step S3;

[0017] S3, determining whether the target frequency of the controlled space is greater than the natural frequency of the Helmholtz resonator;

[0018] S4, if the target frequency of the controlled space is less than the noise reduction frequency of the Helmholtz resonator, drive the first transmission mechanism to increase the length of the neck cavity along the axial direction; and / or drive the second transmission mechanism to increase the distance between the two movable walls, and go to step S1;

[0019] S5. If the target frequency of the controlled space is greater than the noise reduction frequency of the Helmholtz resonator, drive the first transmission mechanism to reduce the length of the neck cavity along the axial direction; and / or drive the second transmission mechanism to reduce the distance between the two movable walls, and go to step S1;

[0020] S6. End control.

[0021] Optionally, the Helmholtz resonator is provided with two cylindrical cavity wall components, and the natural frequency f of the Helmholtz resonator is r The control formula is:

[0022]

[0023] Among them, c is the speed of sound in the resonance cavity, S is the area of ​​one of the two movable walls, l is the distance between the two movable walls of the resonance cavity, (l1+l2) is the length of the neck cavity in the axial direction, l1 is the length of the cylindrical cavity wall component with a smaller inner diameter in the axial direction of the neck cavity, l2 is the length of the cylindrical cavity wall component with a larger inner diameter in the axial direction of the neck cavity, S2 is the area of ​​the cross section of the cylindrical cavity wall component with a larger inner diameter perpendicular to the axis of the neck cavity, S1 is the area of ​​the cross section of the cylindrical cavity wall component with a smaller inner diameter perpendicular to the axis of the neck cavity, and k=S1 / S2.

[0024] Optionally, the method for controlling the natural frequency of the Helmholtz resonator further comprises the following steps:

[0025] S7. Drive the second transmission mechanism so that the first central axis of the resonance cavity changes from a state where it coincides with the axis of the neck cavity to a state where the first central axis of the resonance cavity deviates from the axis of the neck cavity.

[0026] The technical effects of the present invention are as follows:

[0027] The Helmholtz resonator of the present invention has a movable neck cavity and a resonance cavity, that is, the volume of the neck cavity and the volume of the resonance cavity can be adjusted. By adjusting the volume of the neck cavity and the volume of the resonance cavity, the natural frequency (i.e., the vibration reduction frequency) range of the Helmholtz resonator changes, which can adapt to the noise frequency changes in the controlled space.

[0028] The control method of the present invention can adjust the length of the neck cavity and the distance between the two walls of the resonance cavity respectively through the first transmission mechanism and the second transmission mechanism, indirectly changing the volume of the neck cavity and the volume of the resonance cavity, thereby changing the natural frequency of the Helmholtz resonator.

[0029] In summary, the technical solution of the present invention achieves the purpose of the present invention.

[0030] The further effects of the above optional manner will be described below in conjunction with the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of the Helmholtz resonator of the present invention.

[0032] Figure 2 for Figure 1 A schematic structural diagram of another state of the illustrated embodiment.

[0033] Figure 3 Schematic diagram of the Helmholtz resonator of the present invention.

[0034] Figure 4 for Figure 1 A perspective view of the experimental setup of the illustrated embodiment.

[0035] Figure 5 for Figure 4 A perspective view of another angle of the experimental setup shown.

[0036] Figure 6 Flow chart of the control method of the present invention.

[0037] Figure 7 for Figure 4 The simulation experimental results of the experimental device are shown in Figure 1.

[0038] Figure 8 for Figure 4 The simulation experimental results of the experimental device are shown in Figure 2.

[0039] Fig. 9 for Figure 4 The simulation results of the experimental device are shown in Figure 3.

[0040] Fig.10 for Figure 4 Four simulation results of the experimental setup are shown.

[0041] Fig.11 for Figure 4 The simulation results of the experimental device are shown in Fig.

[0042] Fig.12 for Figure 4VI. Simulation results of the experimental setup shown.

[0043] The symbols in the figure are explained as follows:

[0044] 101, movable wall; 102, resonance cavity; 103, movable wall; 104, neck cavity; 105, cylindrical cavity wall component; 106, cylindrical cavity wall component;

[0045] 401, controlled space;

[0046] 501, stepping motor; 502, second transmission mechanism; 503, stepping motor; 504, first transmission mechanism. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0048] like Figure 1 and Figure 4 As shown, the Helmholtz resonator of the present invention comprises a neck cavity 104 and a resonance cavity 102. The neck cavity 104 is connected to the resonance cavity 102, and the neck cavity 104 is connected to the controlled space 401. The neck cavity 104 is a cylindrical cavity, and the resonance cavity 102 is a rectangular cavity. The cylindrical neck cavity 104 has an axis ( Figure 1 The center line of the middle neck cavity 104 from top to bottom and perpendicular to the horizontal direction). The resonance cavity 102 has three axes. For the convenience of subsequent description, Figure 1 The axis of the resonance cavity 102 that coincides with the axis of the neck cavity 104 is the first central axis. Figure 1 The axis in the horizontal direction is the second central axis, and the third axis of the resonance cavity 102 is not involved in the description for the time being.

[0049] The neck cavity 104 is composed of a cylindrical cavity wall component 105 and a cylindrical cavity wall component 106 which are nested together. The cylindrical cavity wall component 105 and the cylindrical cavity wall component 106 can move relative to each other along the axis direction of the neck cavity 104, so that the volume of the neck cavity 104 increases or decreases. Figure 1 , Figure 4 and Figure 5, the first transmission mechanism 504 drives the above relative movement between the cylindrical cavity wall component 105 and the cylindrical cavity wall component 106. Specifically, the first transmission mechanism 504 includes transmission parts including bevel gears, and is connected to the resonance cavity 102 (the wall surface except the movable wall surface 101 and the movable wall surface 103). The stepper motor 501 is connected to the first transmission mechanism 504 as a power source, and the first transmission mechanism 504 transmits power to the resonance cavity 102, and the above relative movement between the cylindrical cavity wall component 105 and the cylindrical cavity wall component 106 is achieved by lifting or lowering the resonance cavity 102.

[0050] Combination Figure 1 , Figure 4 and Figure 5 , the two opposite walls (active wall 101 and active wall 103) of the resonance cavity 102 can move relative to each other along the second central axis direction, so that the volume of the resonance cavity 102 increases or decreases. The active wall 101 and the active wall 103 are respectively connected to the second transmission mechanism 502. The second transmission mechanism 502 includes a screw transmission structure, and the stepper motor 503 is connected to the second transmission mechanism 502 as a power source. The second transmission mechanism 502 further drives the active wall 101 and the active wall 103 to achieve the aforementioned relative movement between the two. Figure 5 As shown, the stepper motor 503 and the second transmission mechanism 502 are arranged on the slide rail so as to move synchronously with the lifting or lowering of the resonance cavity 102. Figure 5 In the illustrated embodiment, there are two sets of stepper motors 503 and connected second transmission mechanisms 502 , corresponding to the movable wall surface 101 and the movable wall surface 103 respectively.

[0051] like Figure 2 As shown, since the movable wall 101 and the movable wall 103 in this embodiment are respectively provided with the second transmission mechanism 502 , the first central axis of the resonance cavity 102 can be set to be parallel to or coincide with the axis of the neck cavity 104 .

[0052] Figure 3 Shows the Figure 1 The control mechanism of the embodiment shown is described in detail as follows:

[0053] Exciting the Helmholtz resonator with an external pressure p0 at the neck opening gives:

[0054]

[0055] Where j is an imaginary unit, ω is the angular frequency, M is the mass of the air in the neck cavity, K is the stiffness caused by the volume of air in the resonance cavity, C is the damping caused by the viscosity effect of the air in the resonance cavity, and v HR is the volume of the neck cavity of the Helmholtz resonator, SHR Represents the cross-sectional area of ​​the neck cavity.

[0056]

[0057] Among them, ξ HR is the damping coefficient, ω HR is the angular frequency corresponding to the natural frequency of the Helmholtz resonator, and ρ is the gas density.

[0058] From formula (2), we can get the natural frequency of the Helmholtz resonator as:

[0059]

[0060] Where V is the volume of the resonant cavity, S HR is the area of ​​the cross section of the neck cavity perpendicular to its axis, l e is the length of the neck cavity, and c is the speed of sound in the resonance cavity 102.

[0061] refer to Figure 1 , since the volume of the resonant cavity 102 is V=Sl, where l is Figure 1 Where, S is the distance between the movable wall 101 and the movable wall 103, S is the area of ​​the movable wall (the movable wall 101 or the movable wall 103), l1 and l2 are the lengths of the non-overlapping portions of the cylindrical cavity wall component 106 and the cylindrical cavity wall component 105 in the axial direction of the neck cavity 104, l1 is the length of the cylindrical cavity wall component 106 with a smaller inner diameter in the axial direction of the neck cavity 104, and l2 is the length of the cylindrical cavity wall component 105 with a larger inner diameter in the axial direction of the neck cavity 104, then the above formula (4) can be expressed as:

[0062]

[0063] Among them, l is the distance between the two movable walls (movable wall 101 or movable wall 103) of the resonance cavity 102, S2 is the area of ​​the cross-section of the cylindrical cavity wall component 105 with a larger inner diameter perpendicular to the axis of the neck cavity 104, S1 is the area of ​​the cross-section of the cylindrical cavity wall component 106 with a smaller inner diameter perpendicular to the axis of the neck cavity 104, and k=S1 / S2.

[0064] It can be seen from the above formula (5) that the natural frequency of the Helmholtz resonator can be changed by changing l, l1, and l2. Figure 1 The embodiment shown can achieve synchronous regulation of the natural frequency of the Helmholtz resonator by the resonance cavity 102 and the neck cavity 104 by adjusting l and / or l1, l2. The aforementioned synchronous regulation can make the natural frequency regulation range of the Helmholtz resonator wider, and can achieve cross-peak regulation and optimize the noise reduction effect.

[0065] Figure 2 shows the Helmholtz resonator and Figure 1 Different adjusted working conditions are shown. Figure 1 In the working state of the Helmholtz resonator shown, the first central axis of the resonance cavity 102 coincides with the axis of the neck cavity 104; Figure 1 In the working state of the Helmholtz resonator shown, the first central axis of the resonance cavity 102 is parallel to the axis of the neck cavity 104 and does not overlap, that is, the first central axis of the resonance cavity 102 deviates from the axis of the neck cavity 104 . Figure 2 The working state of the Helmholtz resonator shown can further optimize the noise reduction effect near the target frequency and amplify the sound waves of non-target frequencies. This effect has practical significance for the application of ship systems. For example, the noise generated by mechanical equipment in the ship cabin needs to be reduced, but the sound waves of the ship communication system and alarm system cannot be suppressed but need to be enhanced.

[0066] Figure 6 The flow chart of the control method of the Helmholtz resonator of the present invention is shown. Figure 1 , Figure 2 , Figure 4 and Figure 5 right Figure 6 The steps shown in are described below.

[0067] Obtaining Frequency Response Data

[0068] In this step, data of the sound pressure amplitude-frequency response near the target frequency of the controlled space 401 is obtained. When the data of the sound pressure amplitude-frequency response of the controlled space 401 is obtained for the first time, data of the sound pressure amplitude-frequency response of the controlled space 401 should be obtained in two cases: before the Helmholtz resonator is connected to the controlled space 401 and after the Helmholtz resonator is connected to the controlled space 401.

[0069] Compare the noise reduction frequency with the target frequency

[0070] Compare the data of the sound pressure amplitude-frequency response of the controlled space 401 in the two cases obtained in the previous step to determine whether the noise reduction frequency of the Helmholtz resonator matches the target frequency of the controlled space 401. If the noise reduction frequency of the Helmholtz resonator matches the target frequency of the controlled space 401, go to step "cavity bias"; if the noise reduction frequency of the Helmholtz resonator does not match the target frequency of the controlled space 401, further determine whether the target frequency of the controlled space 401 is greater than the noise reduction frequency of the Helmholtz resonator.

[0071] Increase cavity volume

[0072] If the target frequency of the controlled space 401 is less than the noise reduction frequency of the Helmholtz resonator, the first transmission mechanism 504 is driven to increase the length of the neck cavity 104 along its axial direction; and / or the second transmission mechanism 502 is driven to increase the distance between the movable wall surface 101 and the movable wall surface 103. The increased length value of the neck cavity 104 along its axial direction or the distance value between the movable wall surface 101 and the movable wall surface 103 can be obtained according to the above formula (5).

[0073] Then go to the step of "obtaining frequency response data", and after obtaining the sound pressure amplitude-frequency response data near the target frequency of the controlled space 401 again, the subsequent steps such as "comparing the noise reduction frequency with the target frequency" are sequentially executed.

[0074] Reduce cavity volume

[0075] If the target frequency of the controlled space 401 is greater than the noise reduction frequency of the Helmholtz resonator, the first transmission mechanism 504 is driven to reduce the length of the neck cavity 104 along the axial direction; and / or the second transmission mechanism 502 is driven to reduce the distance between the movable wall surface 101 and the movable wall surface 103. The reduced length value of the neck cavity 104 along the axial direction or the distance value between the movable wall surface 101 and the movable wall surface 103 can be obtained according to the aforementioned formula (5).

[0076] Then go to the step of "obtaining frequency response data", and after obtaining the sound pressure amplitude-frequency response data near the target frequency of the controlled space 401 again, the subsequent steps such as "comparing the noise reduction frequency with the target frequency" are sequentially executed.

[0077] Cavity bias

[0078] If it is determined that the Helmholtz resonator noise reduction frequency matches the target frequency of the controlled space 401, it indicates that the currently set length value of the axial direction of the neck cavity 104 and the distance value between the movable wall surface 101 and the movable wall surface 103 are appropriate. In order to further enhance the vibration reduction effect, the second transmission mechanism 502 can be driven so that the first central axis of the resonance cavity 102 is changed from a state of coinciding with the axis of the neck cavity 104 (such as Figure 1 ) reaches a state where the first central axis of the resonance cavity 102 deviates from the axis of the neck cavity 104 (as shown in Figure 2 shown).

[0079] End Control

[0080] End the control process of the current cycle, and repeat the process from the beginning step (obtaining frequency response data) in the next cycle. Figure 6 The control flow shown.

[0081] In other embodiments of the control method of the Helmholtz resonator, the parameters of the Helmholtz resonator (the length value of the neck cavity 104 in the axial direction, the distance value between the active wall 101 and the active wall 103) can be determined by formula (5) before the Helmholtz resonator is connected to the controlled space 401, so that the noise reduction frequency of the Helmholtz resonator reaches or approaches the target frequency. If the noise reduction frequency of the Helmholtz resonator is only close to the target frequency due to various environmental factors, the subsequent steps of "increasing the cavity volume" and "reducing the cavity volume" can be relied on for fine-tuning, so as to achieve the purpose as soon as possible.

[0082] The following is an explanation of the technical effect of the present invention through simulation experiment data. Figure 4 The experimental device shown in the figure is used for simulation. The simulation software used is COMSOL Multiphysics 6.2. The width of the controlled space 401 is 1.497m, the depth is 0.3m, and the height is 0.394m. A single-pole point source is added in the controlled space 401 as a point sound source excitation. The volume flow rate of the point sound source is 1×10 -4 m 3 / s, that is, Q0 = 1 × 10 -4 m 3 / s. The air density in the simulation environment is 1.21kg / m 3 , the speed of sound is 340m / s.

[0083] Figure 7 In the displayed data, the "enclosed space" curve represents the frequency response curve when the controlled space 401 is not connected to the Helmholtz resonator; the "coupled symmetric resonator" curve represents the frequency response curve when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 coincides with the axis of the neck cavity 104. Figure 7 As shown, after the Helmholtz resonator is connected, the Helmholtz resonator has a vibration reduction and noise reduction effect on the first-order sound pressure peak of the controlled space 401.

[0084] Figure 8 In the displayed data, the "enclosed space" curve represents the frequency response curve when the controlled space 401 is not connected to the Helmholtz resonator; the "coupled asymmetric resonator" curve represents the frequency response curve when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 is parallel to the axis of the neck cavity 104 but does not overlap. Figure 7 compared to, Figure 8 In the experiment shown, the volume of the resonant cavity 102 and the volume of the neck cavity 104 do not change, but the resonant cavity 102 is offset relative to the neck cavity 104. Figure 8As shown, when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 deviates from the axis of the neck cavity 104, the vibration reduction and noise reduction effect of the Helmholtz resonator on the first-order sound pressure peak of the controlled space 401 is better than Figure 7 The vibration and noise reduction effects shown.

[0085] Figure 7 and Figure 8 The frequency corresponding to the first-order peak is 114 Hz. The total sound pressure level before connecting to the Helmholtz resonator is 120.0577 dB. The total sound pressure level at the first-order peak after connecting to the symmetrical resonator is 62.9554 dB. The total sound pressure level at the first-order peak after connecting to the asymmetrical resonator is 49.3588 dB.

[0086] Fig. 9 In the displayed data, the "enclosed space" curve represents the frequency response curve when the controlled space 401 is not connected to the Helmholtz resonator; the "coupled symmetric resonator" curve represents the frequency response curve when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 coincides with the axis of the neck cavity 104. Figure 7 The Helmholtz resonator setup shown, Fig. 9 In the experiment shown, an operation of reducing the cavity volume is performed, so that the Helmholtz resonator has a vibration reduction and noise reduction effect on the second-order sound pressure peak of the controlled space 401. Figure 7 and Fig. 9 It is shown that the frequency range of vibration and noise reduction of the Helmholtz resonator of the present invention can be effectively adjusted.

[0087] Fig.10 In the displayed data, the "enclosed space" curve represents the frequency response curve when the controlled space 401 is not connected to the Helmholtz resonator; the "coupled asymmetric resonator" curve represents the frequency response curve when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 is parallel to the axis of the neck cavity 104 but does not overlap. Fig. 9 compared to, Fig.10 In the experiment shown, the volume of the resonant cavity 102 and the volume of the neck cavity 104 do not change, but the resonant cavity 102 is offset relative to the neck cavity 104. Fig.10 As shown, when the controlled space 401 is connected to the Helmholtz resonator and the first central axis of the resonance cavity 102 deviates from the axis of the neck cavity 104, the vibration reduction and noise reduction effect of the Helmholtz resonator on the second-order sound pressure peak of the controlled space 401 is better than Fig. 9 The vibration and noise reduction effects shown. Figure 8 and Fig.10 It is shown that the frequency range of vibration and noise reduction of the Helmholtz resonator of the present invention can be effectively adjusted.

[0088] Fig. 9 and Fig.10 The frequency corresponding to the second-order peak is 227Hz. The total sound pressure level before connecting to the Helmholtz resonator is 131.0840dB, the total sound pressure level at the second-order peak after connecting to the symmetrical resonator is 63.3154dB, and the total sound pressure level at the first-order peak after connecting to the asymmetrical resonator is 45.2795dB.

[0089] Fig.11 The experimental data of the following two cases are shown: the volume of the resonance cavity 102 and the volume of the neck cavity 104 are not changed, and only the deviation direction between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 is adjusted (such as Figure 1 In the left and right directions shown in FIG. 1 , the distance between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 is 40 mm. Fig.11 As shown, the different deviation directions between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 do not reflect any difference in the vibration reduction effect of the Helmholtz resonator.

[0090] Fig.12 The experimental data of the following two cases are shown: the volume of the resonance cavity 102 and the volume of the neck cavity 104 are not changed, and only the deviation direction between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 is adjusted (such as Figure 1 In the left and right directions shown in FIG. 1 , the distance between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 is 80 mm. Fig.11 As shown, the different deviation directions between the first central axis of the resonance cavity 102 and the axis of the neck cavity 104 do not reflect any difference in the vibration reduction effect of the Helmholtz resonator.

[0091] The vibration reduction and noise reduction effect of the Helmholtz resonator due to the deviation between the first central axis of the resonant cavity 102 and the axis of the neck cavity 104 is shown in Tables 1 and 2. Table 1 shows the vibration reduction and noise reduction for the first order peak (corresponding to a frequency of 114 Hz). The volume of the resonant cavity 102 remains unchanged. Only by adjusting the positions of the movable wall 101 and the movable wall 103, the resonant cavity 102 and the neck cavity 104 are aligned as shown in Table 1. Figure 2 Table 2 is for the second order peak (corresponding frequency 227 Hz) vibration reduction and noise reduction, the volume of the resonance cavity 102 remains unchanged, and only by adjusting the positions of the active wall 101 and the active wall 103, the resonance cavity 102 and the neck cavity 104 are as follows Figure 2 Bias state shown.

[0092] Table 1

[0093] Offset distance(mm) 20 40 60 80 First order peak total sound pressure (dB) 60.8318 49.3588 60.8409 69.6951

[0094] In Table 1, when the offset distance is 80 mm, the anti-resonance peak of the Helmholtz resonator is at a frequency of 113 Hz, and the minimum value of the total sound pressure level at this frequency is 52.0236 dB.

[0095] Table 2

[0096] Offset distance(mm) 5 10 15 20 Second order peak total sound pressure (dB) 60.6628 45.2795 60.1083 73.94157

[0097] When the offset distance in Table 2 is 15 mm, the anti-resonance peak of the Helmholtz resonator is at a frequency of 226 Hz, and the "second-order peak total sound pressure" in Table 2 is the total sound pressure at a frequency of 226 Hz. When the offset distance in Table 2 is 20 mm, the anti-resonance peak of the Helmholtz resonator is at a frequency of 225 Hz, and the "second-order peak total sound pressure" in Table 2 is the total sound pressure at a frequency of 225 Hz.

[0098] It is worth noting that the above description is only a preferred embodiment of the present invention, and does not limit the scope of patent protection of the present invention. The present invention can also be replaced by equivalent technologies. Therefore, any equivalent changes made by using the description and illustrations of the present invention, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A Helmholtz resonator, comprising a neck cavity and a resonance cavity, wherein the neck cavity is connected to the resonance cavity, characterized in that: The neck cavity includes a cylindrical cavity, and the resonance cavity includes a rectangular cavity; the axis of the neck cavity is parallel to the connection direction between the neck cavity and the resonance cavity; the first central axis of the resonance cavity is parallel to the connection direction between the neck cavity and the resonance cavity, and the second central axis of the resonance cavity is perpendicular to the first central axis; The neck cavity comprises at least two nested cylindrical cavity wall components; a first transmission mechanism is provided, and the first transmission mechanism can drive the cylindrical cavity wall component to move relatively along the axis direction of the neck cavity; The resonance cavity comprises two opposite movable walls parallel to the central axis; a second transmission mechanism is provided; the second transmission mechanism can drive the two movable walls of the resonance cavity to move relative to each other along the direction of the second central axis.

2. A Helmholtz resonator according to claim 1, characterized in that: The second transmission mechanism drives the two movable walls to at least two positions: the first central axis is parallel to or coincides with the axis of the neck cavity.

3. The Helmholtz resonator according to claim 1, characterized in that: Two cylindrical cavity wall parts are provided, and the natural frequency f of the Helmholtz resonator r The control formula is: Among them, c is the speed of sound in the resonance cavity, S is the area of ​​one of the two movable walls, l is the distance between the two movable walls of the resonance cavity, (l1+l2) is the length of the neck cavity in the axial direction, l1 is the length of the cylindrical cavity wall component with a smaller inner diameter in the axial direction of the neck cavity, l2 is the length of the cylindrical cavity wall component with a larger inner diameter in the axial direction of the neck cavity, S2 is the area of ​​the cross section of the cylindrical cavity wall component with a larger inner diameter perpendicular to the axis of the neck cavity, S1 is the area of ​​the cross section of the cylindrical cavity wall component with a smaller inner diameter perpendicular to the axis of the neck cavity, and k=S1 / S2.

4. The method for controlling the natural frequency of a Helmholtz resonator according to claim 1, characterized in that: The steps include: S1. Obtain frequency response data of the controlled space; S2, judging whether the natural frequency of the Helmholtz resonator matches the target frequency of the controlled space, if the natural frequency of the Helmholtz resonator matches the target frequency of the controlled space, go to step S6; if the natural frequency of the Helmholtz resonator does not match the target frequency of the controlled space, go to step S3; S3, determining whether the target frequency of the controlled space is greater than the natural frequency of the Helmholtz resonator; S4, if the target frequency of the controlled space is less than the noise reduction frequency of the Helmholtz resonator, drive the first transmission mechanism to increase the length of the neck cavity along the axial direction; and / or drive the second transmission mechanism to increase the distance between the two movable walls, and go to step S1; S5. If the target frequency of the controlled space is greater than the noise reduction frequency of the Helmholtz resonator, drive the first transmission mechanism to reduce the length of the neck cavity along the axial direction; and / or drive the second transmission mechanism to reduce the distance between the two movable walls, and go to step S1; S6. End control.

5. The method for controlling the natural frequency of a Helmholtz resonator according to claim 4, characterized in that: Two cylindrical cavity wall parts are provided, and the natural frequency f of the Helmholtz resonator r The control formula is: Among them, c is the speed of sound in the resonance cavity, S is the area of ​​one of the two movable walls, l is the distance between the two movable walls of the resonance cavity, (l1+l2) is the length of the neck cavity in the axial direction, l1 is the length of the cylindrical cavity wall component with a smaller inner diameter in the axial direction of the neck cavity, l2 is the length of the cylindrical cavity wall component with a larger inner diameter in the axial direction of the neck cavity, S2 is the area of ​​the cross section of the cylindrical cavity wall component with a larger inner diameter perpendicular to the axis of the neck cavity, S1 is the area of ​​the cross section of the cylindrical cavity wall component with a smaller inner diameter perpendicular to the axis of the neck cavity, and k=S1 / S2.

6. The method for controlling the natural frequency of a Helmholtz resonator according to claim 4, characterized in that: The following steps are also included: S7. Drive the second transmission mechanism so that the first central axis of the resonance cavity changes from a state where it coincides with the axis of the neck cavity to a state where the first central axis of the resonance cavity deviates from the axis of the neck cavity.

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