CN112435646A

CN112435646A - Acoustic metamaterial large-area short-channel broadband ventilation sound insulator and barrier

Info

Publication number: CN112435646A
Application number: CN201910788813.4A
Authority: CN
Inventors: 杨志宇; 陈晖强; 周振威; 龚小超; 王春华
Original assignee: Lingbo Yisheng Technology Shenzhen Co ltd
Current assignee: Lingbo Yisheng Technology Shenzhen Co ltd
Priority date: 2019-08-26
Filing date: 2019-08-26
Publication date: 2021-03-02

Abstract

The invention belongs to the technical field of shock absorption and noise reduction, and particularly relates to a functional structure device capable of blocking noise and providing ventilation of a large channel. The multiple counterweight film resonators are coupled through the shared back cavity to greatly increase the number of resonance states of the device, so that the defect of a single counterweight film resonator-single back cavity super sound absorption device (US 9,711,129B 2) with rare number of resonance states is overcome, and the broadband sound insulation effect of the conventional super sound absorption device is greatly improved. A plurality of weighted film resonators are provided with a plurality of back cavities to form part of the side of the channel of the ventilation and sound insulation device, so that air can smoothly flow in the channel but can block sound waves in a wide frequency range.

Description

Acoustic metamaterial large-area short-channel broadband ventilation sound insulator and barrier

Technical Field

The invention belongs to the technical field of shock absorption and noise reduction, and particularly relates to a structural device capable of blocking noise and providing ventilation of a large channel.

Background

Many applications require noise reduction while at the same time providing sufficient passage for ventilation. The exhaust ports of large building central air conditioners, and road noise barriers that allow large natural airflows to exhaust vehicle exhaust, to name just two of many examples. Porous sound absorbing materials are an important type of sound absorbing and noise reducing material. Because the interior of the porous material is provided with a large number of micropores, when sound waves enter the interior of the material from the micropores, air in the pores is excited to vibrate, relative motion is generated between the vibrating air and the solid rib of the porous material, corresponding viscous resistance is generated in the micropores due to the viscosity of the air, and sound energy is attenuated accordingly. Since the magnitude of the viscous resistance is proportional to the frequency, the sound absorption performance of the porous sound absorbing material deteriorates as the frequency decreases. At present, the most mature technology uses porous sound absorption materials and perforated plates which are arranged on the side wall of a ventilation channel of a ventilation sound insulator to achieve the intensity of high-frequency sound waves in the attenuation channel, but the effect is weak below 500Hz, a long channel with the length of more than one meter can generate the sound insulation effect of several decibels, but the long channel increases the wind resistance, so that the porous materials adopted by the prior art for low-frequency noise cannot be used. To date, no ventilation and sound insulation device with large channel area and large channel area ratio, short channel and low wind resistance has been disclosed. In order to achieve such a ventilation insulator, the dissipation at low frequencies must be increased, which requires an increase in the energy density in the relevant device, for example by means of resonance, so that a local resonance acoustic metamaterial is highly desired. However, in order to obtain a broadband sound insulation effect, a local resonance acoustic metamaterial having a distribution of numerous densely distributed resonance states is required. The acoustic metamaterial provided by the invention has the resonance state distribution.

Disclosure of Invention

The multiple counterweight film resonators are coupled through the shared back cavity to greatly increase the number of resonance states of the device, so that the defect of a single counterweight film resonator-single back cavity super sound absorption device (US 9,711,129B 2) with rare number of resonance states is overcome, and the broadband sound insulation effect of the conventional super sound absorption device is greatly improved. A plurality of counterweight film resonators are matched with a plurality of back cavities to form the side surface of the channel part of the ventilation sound insulator, so that air can smoothly circulate in the channel, and sound waves can be blocked in a wide frequency range only by a short channel.

Drawings

FIG. 1A is a schematic view of an acoustic metamaterial wide area short channel broadband ventilation insulator.

FIG. 1B is another acoustic metamaterial large area short channel broadband ventilation insulator.

Figure 1C shows a weighted thin film resonator.

FIG. 1D shows another weighted film resonator.

FIG. 1E illustrates an acoustic metamaterial large area short channel broadband ventilation insulator with multiple weighted thin film resonators.

FIG. 1F is another acoustic metamaterial large area short channel broadband ventilation insulator with multiple weighted film resonators.

FIG. 2A 'port' type acoustic metamaterial large area short channel broadband ventilation and sound insulation device.

FIG. 2B 'L' type acoustic metamaterial large-area short-channel broadband ventilation sound insulator.

FIG. 2C is a schematic view of a concave acoustic metamaterial broad area short channel broadband ventilation insulator.

FIG. 2D 'one' type acoustic metamaterial large area short channel broadband ventilation insulator.

FIG. 2E is a schematic view of a hexagonal acoustic metamaterial large area short channel wide frequency ventilation insulator.

FIG. 2F is a triangular acoustic metamaterial large area short channel broadband ventilation insulator.

FIG. 3A is a two-dimensional array of a single layer acoustic metamaterial large area short channel broadband sound insulator ventilation and insulation barrier.

FIG. 3B is a two-dimensional array of multilayer acoustic metamaterial large area short channel broadband sound insulator ventilation and insulation barriers.

FIG. 4A is a cross-sectional side view of an acoustic metamaterial large area short channel wide frequency acoustic vent barrier two dimensional array acoustic vent barrier with single sided streamlined cavities.

FIG. 4B is a cross-sectional side view of a two-dimensional array of acoustic metamaterial large area short channel wide frequency acoustic ventilation barriers with double sided streamlined cavities.

FIG. 5 is a graph of the measured transmission attenuation spectrum (solid line) and transformer noise spectrum (dashed line) of a real acoustic metamaterial large area short channel wide frequency ventilation insulator. The inset is a photograph of the sample.

Figure 6A single cavity-single weighted thin film resonator of reference-1.

Figure 6B measured transmission attenuation spectra of the structure depicted in figure 6A.

Detailed Description

SUMMARY

The invention is based on sound absorption metamaterial (US patent 8,579,073B 2, Chinese patent CNZL2142364, invention-1) and super sound absorption device (US 9,711,129B 2, invention-2). It is to be noted that the super sound absorbing device in invention-2 has only one back cavity, and the only opening of the back cavity is covered by one weighted film resonator (US 7,395,898B 2, invention-3). In reference-1 (Applied Physics Letters110, 021901 (2017)), the super sound absorbing device of invention-2 is disposed on a side wall of one of the channels. In this scenario, the resonance of the super-sound absorber creates an acoustic impedance in the channel close to 0. Such 0 impedance is strongly mismatched with the acoustic impedance of air, thereby isolating the sound waves propagating along the pipe. As can be seen from reference-1, the resonant mode of this single back cavity-single weighted film resonator device is rare, and therefore, it can only have a certain sound insulation effect in some narrow frequency bands.

FIG. 1A shows a representative device of the present invention. A volume 101 is bounded by a plurality of weighted film resonators 102 and a substantially rigid body housing 103. The space completely enclosed by the rigid housing and the resonator of the counterweight is called the 'opening' of the sealed cavity. The vibrations of the weighted film resonators on the respective openings can be effectively coupled to each other only with the aid of the back cavity. Without the back cavity, their vibrations are independent of each other and do not affect each other. Figure 1B shows a slightly different arrangement to that of figure 1A. The original capsule 101 is divided by a partition 104 into two capsule compartments 111 and 115.

Fig. 1C shows a representative weighted film resonator comprising a planar and acoustically transparent rigid frame 121, an elastic membrane 122 secured at its edges to the frame 121, and one or more tabs 123 affixed to the membrane. The patches may be of symmetrical shape such as circular or square, or asymmetrical such as semicircular, triangular, crescent-shaped, etc. The thickness of the platelets may be uniform or non-uniform, i.e., thicker or thinner near the straight edge regions of the semicircular plates than the rest, so that their vibrational modes on the film resemble the decorative film of invention-1. One particular example is a film without decorative tabs. The single resonator can be divided into several resonators by adding a frame, such as the structure of fig. 1D, with an additional rigid bar 131 dividing the original frame 121 into left 132 and right 133 frames. The vibrations of two weighted film resonators mounted on the two frames are effectively coupled only with the aid of the back cavity. Without the back cavity, their vibrations are independent of each other and do not affect each other.

Several resonator devices are mounted at the opening of the sealed chamber to form a straight channel, the plane of the resonator devices being parallel to the axis of the straight channel, as shown in figures 1A and 1B. As shown in fig. 1E, more resonator film weights 141 may be mounted at suitable locations within the capsule, such as behind the outer resonator film weights 142, and/or elsewhere, as shown in fig. 1E. As shown in fig. 1F, the resonator 151 divides the sealed chamber 152 into several sealed sub-chambers. The cross-sectional shape of the channel may be any polygonal shape such as square/rectangular, L-shaped, ' concave, ' straight, ' hexagonal, triangular, etc. as illustrated in fig. 2. In the example shown in fig. 1, the cross-sectional shape of the channel is square, or "square".

The curvature energy of a weighted film resonator is typically highly concentrated at the die-to-film contact edge, and the film-to-fixture frame contact edge. This type of dissipation is the primary dissipation mechanism of acoustic energy in the channel (invention-1). The combination of the sealed cavity and the resonator of the thin film counterweight form a hybrid resonator (invention-2), and the combination of resonance and curvature energy dissipation thereof causes the sound wave in the channel to be absorbed in a large amount. The main difference between the inventive device and the hybrid resonator of invention-2 is that the hybrid resonator of invention-2 is formed by a single weighted thin film resonator mounted on a single back cavity opening. As can be seen from reference-1, such a sound insulator has only a few resonance modes available in the frequency range in which sound insulation is required, and therefore has a sound insulation effect in only a few narrow frequency bands at most. The structure of the invention has a plurality of counterweight thin film resonators sharing a closed cavity, and the counterweight thin film resonators are coupled through a commonly shared back cavity to generate a plurality of resonance modes. This greatly increases the range of design parameters and insulator performance, leading to the broadband insulator demonstrated in the present invention. Even with the 'I' -shaped ventilation noise insulator having only one opening, several subframes can be divided on the opening surface to form several counterweight film resonators (see FIG. 1D), and the vibration of the counterweight film resonators is coupled through the closed cavity to generate more resonance modes than that of the single counterweight film resonator, so that the effect of sound insulation in a wide frequency band can be realized. The frequency range and the sound insulation amount of the wide frequency band can be adjusted through the design of the counterweight film resonator (see invention-3), the shape and the size of the channel and the volume of the sealed cavity, so that the channel of the ventilation sound insulator meets the actual wind resistance limiting requirement, and the optimized sound insulation effect is achieved aiming at the frequency spectrum characteristic of a noise source. The theory, simulation and design difficulty of the device of the invention that a plurality of counterweight thin film resonators share one back cavity is far higher than that of a hybrid resonance sound insulator (invention-2) of a single counterweight thin film resonator and a single sealed cavity, and technicians familiar with the hybrid resonance sound insulator (invention-2) cannot easily master and overcome the theory, simulation and design difficulty. Only those skilled in the art who dare to and can break through the difficulty, namely the inventor of the patent, successfully master the relevant theory, simulation and design.

Since the channel is completely empty and there is no object obstructing the flow of air, the function of this device is to provide sound insulation and a large area for the free circulation of air. In practical application, the wind resistance mainly comes from equipment and pipelines which need to be driven by a fan, such as air conditioning pipelines which are distributed all over a building, or oil fume extraction pipelines which reach various kitchens and oil fume filters at air outlets, and the like, and the additional wind resistance brought by the ventilation and sound insulation device is negligible compared with the wind resistance of the equipment, so that the wind resistance of an actual ventilation system is almost irrelevant to the length of the ventilation and sound insulation device channel, but the length of the ventilation and sound insulation device channel is increased, and a superior sound insulation effect can be brought. Therefore, the device of the invention can thoroughly solve the problems of large wind resistance and low sound insulation effect of the prior art adopting the porous sound-absorbing material.

As shown in fig. 3, a plurality of ventilation insulators having the same outer boundary dimensions and internal passages form a two-dimensional array that can form a planar barrier with a large air area ratio that blocks broadband sound waves through the passages. Several layers of barriers with the same channel and peripheral dimensions are stacked to form a multi-layer combined barrier, so that the sound insulation quantity can be increased on the premise of hardly increasing the wind resistance. If the barriers of the layers have sound insulation effects of different frequency bands, the barriers formed by overlapping the barriers can have broadband sound insulation effects. To reduce wind resistance, the non-vented portion of the barrier may be shaped in a streamline form, such as a one-way streamline form in fig. 4A or a two-way streamline form in fig. 4B.

Examples of the present invention

Fig. 5 shows a photograph 501 of a ventilation insulator of a real example. The outer frame dimensions of the ventilation and noise insulation device are 30 cm × 30 cm, the air duct is 10 cm × 10 cm, and the air duct is only 10 cm long. Its measured transmission attenuation spectrum 502 is designed for the noise spectrum 503 of the transformer. In the 5 main noise peak frequency bands of the transformer, the ventilation sound insulator can insulate sound by 13 decibels at 200Hz, insulate sound by 21 decibels at 300Hz, insulate sound by 17 decibels at 400Hz, insulate sound by 11 decibels at 500Hz, and insulate sound by 7 decibels at 800 Hz. If several similar ventilation and sound insulation devices are connected in front and back, the sound insulation amount can be correspondingly increased. If the acoustic sponge provided by the prior art is used instead, the obtained measured transmission attenuation spectrum 504 shows that the sound insulation amount at 200Hz is only 1 dB. The sound insulating advantage of this particular device of the invention is quite evident below 800Hz compared to acoustic sponges. If the outer dimension of the back cavity is reduced to 20 cm × 20 cm, the frequency of the maximum sound insulation peak can be increased. It can be seen from the measured transmission attenuation spectrum 505 of this sample that there is a 15 db sound insulation at 800Hz, although it is not ideal for blocking the peak of the transformer noise 502 at 200 Hz. The amount of sound insulation achieved was complementary to the first sample when used in series. These two examples are described in relation to the iceberg corner only, and reflect in part the powerful function and design latitude of the inventive structure for ventilation and sound insulation applications.

By way of comparison, figure 6A shows the single cavity-single weighted thin film resonator structure reported in reference-1, with an effective channel length of 10 cm, and figure 6B shows the measured transmission attenuation spectrum 601 of the structure. It can be seen from the figure that the structure has more effective sound insulation effect only in a few narrow frequency bands, such as 400Hz, 450Hz, 700Hz, and the like, and is in obvious disadvantage compared with the wide-range broadband effect of the structure of the invention.

It is contemplated that various other changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the subject matter, may be made by those skilled in the art without departing from the spirit of the invention and the scope of protection as defined in the appended claims.

Claims

1. A ventilation and sound insulation metamaterial structure comprising a volume of space bounded entirely by a substantially rigid shell structure and a plane defined by one or more openings in the shell structure; and elastic or flexible films; a substantially rigid weight mounted on said membrane, whereby said membrane and said weight establish a plurality of eigenfrequencies of resonance forming a membrane-type acoustic metamaterial;

wherein the boundary of the membrane is tightly fixed with the boundary of the opening on the shell structure;

wherein the membrane face forms part of the side walls of a vertical channel, the remaining side walls of the channel being formed by the rigid shell structure; the cross section of the channel is polygonal; the central axis of the vertical channel is a straight line.

2. The ventilation and sound insulation metamaterial structure of claim 1, wherein:

and selecting the eigen-vibration frequency of the thin film so as to block the sound wave propagating in the metamaterial channel.

3. The ventilation and sound insulation metamaterial structure of claim 1, wherein:

the venting acoustic metamaterial structure provides an effective mass density irregularity of a thin film type acoustic metamaterial in an anti-resonance state that, in combination with the reflective surface and the enclosed space between the thin film and the solid surface, achieves an almost 0 impedance state at a predetermined frequency.

4. The ventilation and sound insulation metamaterial structure of claim 1, wherein:

the substantially rigid weights have a transverse dimension less than a transverse dimension of the elastic or flexible breathable film.

5. The ventilation and sound insulation metamaterial structure of claim 1, wherein: the membrane is prestressed in-plane by a predetermined amount.

6. The ventilation and sound insulation metamaterial structure of claim 1, wherein: the inner surface of the shell and the space comprise a material having acoustic absorption properties.

7. A ventilation and sound insulation metamaterial structure comprising a plurality of volumes of space each bounded entirely by a substantially rigid shell structure and a plane defined by one or more openings in the shell structure;

and elastic or flexible films; a substantially rigid weight mounted on said membrane, whereby said membrane and said weight establish a plurality of eigenfrequencies of resonance,

wherein, the film surfaces on the shell structure openings jointly form part of side walls of a vertical channel, and the other side walls are formed by rigid shell structures of the ventilation and sound insulation metamaterial structures;

wherein the cross section of the channel is polygonal; the central axis of the vertical channel is a straight line.

8. The ventilation and sound insulation metamaterial structure of claim 7, wherein:

9. The ventilation and sound insulation metamaterial structure of claim 7, wherein:

10. The ventilation and sound insulation metamaterial structure of claim 7, wherein:

11. The ventilation and sound insulation metamaterial structure of claim 7, wherein:

the membrane is prestressed in-plane by a predetermined amount.

12. The ventilation and sound insulation metamaterial structure of claim 7, wherein:

the inner surface of the shell and the space comprise a material having acoustic absorption properties.

13. A plurality of the ventilation and sound insulation metamaterial structures of claims 1-6 or 7-12 configured as a two-dimensional large area wall or panel, wherein the channels of the ventilation and sound insulation metamaterial structures are substantially perpendicular to the plane formed by the wall or panel, thereby forming a large area ventilation and sound insulation wall or panel.

14. A large area ventilated sound insulating wall or panel as claimed in claim 1 wherein: the unventilated part of the wall or the plate is provided with a streamline protruding structure so as to reduce the wind pressure caused when the wind blows to the wall or the plate.