CN107799110B - Sweep frequency type Helmholtz silencer - Google Patents
Sweep frequency type Helmholtz silencer Download PDFInfo
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- CN107799110B CN107799110B CN201711054798.8A CN201711054798A CN107799110B CN 107799110 B CN107799110 B CN 107799110B CN 201711054798 A CN201711054798 A CN 201711054798A CN 107799110 B CN107799110 B CN 107799110B
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
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- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
- Exhaust Silencers (AREA)
Abstract
The invention discloses a swept-frequency Helmholtz silencer, which comprises a bottom plate, a Helmholtz main body part, a Helmholtz neck part, a loudspeaker, a microphone, a signal generating circuit and a multiplying circuit, wherein the bottom plate is provided with a plurality of first electrodes; the two ends of the Helmholtz main body part are respectively connected with the bottom plate and the Helmholtz neck part, the loudspeaker is fixed on the bottom plate, and the microphone is arranged in the Helmholtz main body part; the multiplication circuit multiplies the sine or cosine signal output by the signal generation circuit with the signal output by the microphone; at the moment, the output signal of the multiplying circuit has sine or cosine change characteristics, and the output signal of the multiplying circuit is input into the loudspeaker, so that the impedance of the bottom plate has sine or cosine change characteristics along with time. Therefore, the silencer provided by the invention can enable the natural frequency of the silencer to change along with the time period in a certain frequency range without any mechanical transmission device, has the frequency sweeping characteristic, realizes the automatic silencing function in the frequency sweeping range, and has the advantages of simple structure and convenience in assembly and disassembly.
Description
Technical Field
The invention relates to the field of silencing devices, in particular to a frequency sweeping type Helmholtz silencer.
Background
Noise is a common phenomenon in the engineering field. The noise may affect the proper operation of the associated personnel and even be a health hazard. How to effectively control the propagation of noise is a long-term concern in the fields of mechanical engineering, aerospace, transportation and the like.
The helmholtz silencer has a simple structure and is easy to implement, so that the helmholtz silencer is widely applied and becomes one of important means for noise control at present. Helmholtz mufflers can generally be divided into two main categories, fixed and adjustable. Wherein a fixed muffler can only be used to control noise in a particular frequency band. When the external excitation frequency changes, the fixed muffler fails. The adjustable silencer enables the natural frequency of the silencer to change along with the change of external conditions by adjusting the volume of a cavity of the silencer or the size of a Helmholtz neck, and therefore the control frequency range of the dynamic vibration absorber is widened. The current adjustable silencer mainly comprises a frequency adjustable silencer and a silencer controlled by a motor. The silencer with adjustable frequency mainly adjusts the length of a cavity of the silencer in a manual mode to adjust the frequency of the silencer, but the silencer is not convenient to use in practice due to the adoption of the manual mode. The motor-controlled silencer mainly controls the pipe diameter of the silencer through the motor so as to adjust the frequency of the silencer, and the adjustable silencer needs a mechanical driving device and is relatively complex in structure, complex in operation and inconvenient to use, and the controlled noise frequency needs to be accurately predicted. Therefore, how to obtain a muffler with a simple structure and without any mechanical driving device is a technical problem which needs to be solved urgently in the field of the prior muffler device.
Disclosure of Invention
The invention aims to provide a swept-frequency Helmholtz silencer, which can overcome the defects that the conventional adjustable silencer needs a mechanical driving device, is complex in structure, is inconvenient to use and the like.
In order to achieve the purpose, the invention provides the following scheme:
a swept frequency Helmholtz muffler comprises a Helmholtz muffler and a swept frequency control circuit module;
the Helmholtz silencer comprises a bottom plate, a Helmholtz main body part and a Helmholtz neck part; both ends of the helmholtz body part are respectively connected with the bottom plate and the helmholtz neck part;
the sweep frequency control circuit module comprises a loudspeaker, a microphone, a signal generating circuit and a multiplying circuit;
the loudspeaker is fixed on the bottom plate, and the microphone is arranged in the Helmholtz main body part; the output end of the microphone and the output end of the signal generating circuit are respectively connected with the input end of the multiplying circuit, and the output end of the multiplying circuit is connected with the loudspeaker;
the output signal of the signal generating circuit is a sine signal or a cosine signal.
Optionally, the helmholtz body portion and the helmholtz neck portion are both structures with a cavity inside.
Optionally, the helmholtz body portion and the helmholtz neck portion are both cylindrical structures, cuboids or cubes, and the inner portions of the cylindrical structures, the cuboids or the cubes are cavities.
Optionally, the helmholtz body part and the helmholtz neck part are combined to form a convex structure with two open ends; the open end of the helmholtz body is closed by the bottom plate.
Optionally, the area of the cross section of the helmholtz neck part is 10% -50% of the area of the cross section of the helmholtz body part; the helmholtz neck portion and the helmholtz body portion are perpendicular to an axial plane of the helmholtz body portion.
Optionally, the microphone is located at any position in the cavity of the helmholtz body.
Optionally, the bottom plate is provided with a mounting port of the speaker.
Optionally, the output signal of the signal generating circuit is a signal with adjustable frequency and adjustable amplitude.
Optionally, the frequency of the output signal of the signal generating circuit is 10-200 Hz.
Optionally, the speaker is a dynamic speaker or a flat panel speaker.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a swept-frequency Helmholtz silencer, which comprises a bottom plate, a Helmholtz main body part, a Helmholtz neck part, a loudspeaker, a microphone, a signal generating circuit and a multiplying circuit, wherein the bottom plate is provided with a plurality of first connecting lines; both ends of the helmholtz body part are respectively connected with the bottom plate and the helmholtz neck part; the loudspeaker is fixed on the bottom plate, and the microphone is arranged in the Helmholtz main body part; the output end of the microphone and the output end of the signal generating circuit are respectively connected with the input end of the multiplying circuit, and the output end of the multiplying circuit is connected with the loudspeaker. The invention multiplies the sine or cosine signal output by the signal generating circuit by the signal output by the microphone by arranging the multiplying circuit, so that the output signal of the multiplying circuit has sine or cosine change characteristic, and the impedance of the bottom plate of the Helmholtz silencer also has sine or cosine change characteristic along with time after the output signal of the multiplying circuit is input to the loudspeaker, thus leading the natural frequency of the Helmholtz silencer to have frequency sweep characteristic, namely the natural frequency of the Helmholtz silencer to change along with the time period in a certain frequency range. Therefore, the silencer provided by the invention can realize automatic silencing without any mechanical transmission device, and has the advantages of simple structure and convenience in disassembly and assembly; and the natural frequency of the silencer changes periodically along with time in a certain frequency range, so that the effective control frequency range of the silencer is enlarged, the controlled noise frequency does not need to be accurately predicted, and the silencer is more convenient for practical engineering application.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is an elevation view of a swept frequency Helmholtz muffler according to an embodiment of the present invention;
fig. 2 is a perspective view of a swept frequency helmholtz muffler according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a swept-frequency Helmholtz silencer, which can overcome the defects that the conventional adjustable silencer needs a mechanical driving device, is complex in structure, is inconvenient to use and the like.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a front view of a swept-frequency helmholtz muffler according to an embodiment of the present invention, and fig. 2 is a perspective view of the swept-frequency helmholtz muffler according to the embodiment of the present invention.
As shown in fig. 1, the swept-frequency helmholtz silencer provided by the embodiment of the present invention includes a helmholtz silencer and a swept-frequency control circuit module.
The Helmholtz silencer comprises a bottom plate 1, a Helmholtz main body part 2 and a Helmholtz neck part 3; the frequency sweep control circuit module comprises a loudspeaker 4, a microphone 5, a signal generating circuit 6 and a multiplying circuit 7.
And the bottom plate 1 is provided with a mounting port of the loudspeaker 4.
Both ends of the helmholtz body 2 are connected to the bottom plate 1 and the helmholtz neck 3, respectively.
Helmholtz main part 2 with Helmholtz neck 3 is the inside structure that is the cavity, specifically does Helmholtz main part 2 with Helmholtz neck 3 is inside cylindrical structure, cuboid or the cube that is the cavity, just Helmholtz main part 2 with Helmholtz neck 3 makes up and forms both ends open-ended convex structure. The open end of the helmholtz body 2 is closed by the bottom plate 1.
Preferably, as shown in fig. 2, the helmholtz body portion 2 and the helmholtz neck portion 3 are each a cylindrical structure having a hollow inside.
Preferably, the area of the cross section of the helmholtz neck portion 3 is 10% to 50% of the area of the cross section of the helmholtz body portion 2. The helmholtz neck portion 3 and the helmholtz body portion 2 are perpendicular to an axial plane of the helmholtz body portion 2 in both cross-sections.
As shown in fig. 1 and 2, the speaker 4 is fixed to the base plate 1, the microphone 5 is provided inside the helmholtz body 2, and the microphone 5 is located at an arbitrary position in the cavity of the helmholtz body 2.
The output end of the microphone 5 and the output end of the signal generating circuit 6 are respectively connected with the input end of the multiplying circuit 7, and the output end of the multiplying circuit 7 is connected with the loudspeaker 4.
The output signal of the signal generating circuit 6 is a sine signal or a cosine signal.
The output signal of the signal generating circuit 6 is a signal with adjustable frequency and adjustable amplitude.
Preferably, the frequency of the output signal of the signal generating circuit 6 is 10-200 Hz.
The loudspeaker 4 is an electrodynamic loudspeaker or a flat panel loudspeaker.
Preferably, the multiplication circuit 7 is an AD825 analog multiplier.
Preferably, the signal generating circuit 6 is an ICL8038 multifunctional signal generator.
The working principle of the swept-frequency Helmholtz silencer provided by the embodiment of the invention is as follows:
the dynamic model of the swept-frequency helmholtz silencer can be expressed as follows:
where ρ and c are the air density and the sound velocity, respectively. M, C and K are the air mass, damping and stiffness, respectively, in the Helmholtz neck 3, and
s and SkThe cross-sectional areas of the helmholtz neck 3 and the bottom plate 1, respectively. V is the helmholtz muffler cavity volume. x is the number ofkIs the displacement of the cone of the loudspeaker 4. PoutIs an external sound pressure. x is the air particle displacement in the helmholtz neck 3.
As shown in fig. 1, the microphone 5 and the signal generating circuit 6 are connected to two input terminals of a multiplying circuit 7, respectively, and the output terminal of the multiplying circuit 7 is connected to the speaker 4. Neglecting the influence of the cone quality of the loudspeaker 4 and the inductance in the internal circuit, the displacement x of the cone of the loudspeaker 4kCan be simplified to be represented as:
xk＝pin·K(2)；
in the formula, K isOutput signal, p, of signal generating circuit 6inThe sound pressure in the cavity measured by the microphone 5 can be expressed as:
the formula (3) is substituted into the formula (2) and can be obtained by finishing,
the formula (4) is substituted into the formula (1) and can be obtained by finishing,
in the formula (I), the compound is shown in the specification,
as can be seen from the formula (5), the Helmholtz muffler has a natural frequency of
From the above analysis, it can be found that, when the output signal K of the signal generating circuit 6 is a sine signal or a cosine signal, the value of f (K) in the formula (6) changes periodically within a certain range, so that the natural frequency of the helmholtz silencer changes periodically within a certain frequency range, the natural frequency of the helmholtz silencer has a frequency sweeping characteristic, and the effective control frequency band of the silencer is effectively expanded.
The sweep frequency type Helmholtz silencer provided by the embodiment of the invention has the beneficial effects that:
because the output signal of the signal generating circuit 6 provided by the embodiment of the present invention may be a sine signal or a cosine signal, the sine or cosine signal output by the signal generating circuit 6 is multiplied by the signal of the microphone 5 by the multiplying circuit 7, so that the output signal of the multiplying circuit 7 also has sine or cosine change characteristics, the output signal of the multiplying circuit 7 is input to the speaker 4, so that the impedance of the bottom plate 1 of the helmholtz muffler also has sine or cosine change characteristics with time, and further the natural frequency of the helmholtz muffler has frequency sweeping characteristics, that is, the natural frequency of the helmholtz muffler changes with time period within a certain frequency range. Therefore, the Helmholtz silencer provided by the invention can realize automatic silencing without any mechanical transmission device, and has the advantages of simple structure and convenience in disassembly and assembly; and the natural frequency of the Helmholtz silencer changes periodically along with time in a certain frequency range, so that the effective control frequency range of the Helmholtz silencer is enlarged, the controlled noise frequency does not need to be accurately predicted, and the Helmholtz silencer is more convenient for practical engineering application.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (9)
1. A swept frequency type Helmholtz silencer is characterized by comprising a Helmholtz silencer and a swept frequency control circuit module;
the Helmholtz silencer comprises a bottom plate, a Helmholtz main body part and a Helmholtz neck part; both ends of the helmholtz body part are respectively connected with the bottom plate and the helmholtz neck part;
the sweep frequency control circuit module comprises a loudspeaker, a microphone, a signal generating circuit and a multiplying circuit;
the loudspeaker is fixed on the bottom plate, and the microphone is arranged in the Helmholtz main body part; the output end of the microphone and the output end of the signal generating circuit are respectively connected with the input end of the multiplying circuit, and the output end of the multiplying circuit is connected with the loudspeaker;
the output signal of the signal generating circuit is a sine signal or a cosine signal, and the output signal of the signal generating circuit is a signal with adjustable frequency and adjustable amplitude;
the multiplication circuit multiplies the sine signal or the cosine signal with the signal output by the microphone, so that the output signal of the multiplication circuit also has sine or cosine change characteristics, the output signal of the multiplication circuit is input to the loudspeaker, so that the impedance of the bottom plate also has sine or cosine change characteristics along with time, and further the natural frequency of the Helmholtz silencer has frequency sweeping characteristics.
2. A swept frequency helmholtz muffler according to claim 1, wherein the helmholtz body section and the helmholtz neck section are both internally hollow structures.
3. A swept frequency helmholtz muffler according to claim 2, wherein the helmholtz body section and the helmholtz neck section are each cylindrical, cuboid or cubic structures with a cavity inside.
4. A swept frequency helmholtz muffler according to claim 3, wherein the helmholtz body portion and the helmholtz neck portion combine to form a convex structure open at both ends; the open end of the helmholtz body is closed by the bottom plate.
5. A swept frequency Helmholtz muffler according to claim 4, wherein the area of the cross-section of the Helmholtz neck portion is 10% to 50% of the area of the cross-section of the Helmholtz main body portion; the helmholtz neck portion and the helmholtz body portion are perpendicular to an axial plane of the helmholtz body portion.
6. A swept frequency helmholtz muffler according to claim 2, wherein the microphone is located anywhere within the cavity of the helmholtz body section.
7. A swept frequency helmholtz muffler as claimed in claim 1, wherein the bottom plate is provided with a mounting port for the speaker.
8. A swept frequency helmholtz muffler according to claim 1, wherein the frequency of the output signal of the signal generating circuit is 10-200 Hz.
9. A swept frequency helmholtz muffler according to claim 1, wherein the loudspeaker is an electrodynamic loudspeaker or a plate loudspeaker.
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| CN201711054798.8A CN107799110B (en) | 2017-11-01 | 2017-11-01 | Sweep frequency type Helmholtz silencer |
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| CN110491362B (en) * | 2019-08-21 | 2022-02-01 | 宁波奥克斯电气股份有限公司 | Noise processing method and device of air conditioner, air conditioner and mobile terminal |
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