Sound absorbing structure and sound absorbing device

Abstract

The present invention provides a sound absorbing structure comprising a sound absorbing material and a full seal membrane, wherein the sound absorbing material is designed to absorb sound waves, said sound absorbing material having at least one exposed area exposed to the surrounding environment, through which said sound waves enter said sound absorbing material. The full seal membrane is designed to cover all exposed areas of said sound absorbing material, wherein said full seal membrane extends in a continuous and dense form. The above-mentioned full seal membrane isolates the sound absorbing material from the surrounding environment, thereby preventing the entry of fibers or foam material inside the sound absorbing material into the surrounding air environment, or preventing the entry of dust from the external air into the sound absorbing material.

Description

TECHNICAL FIELD

[0001] The present application relates to a sound absorption structure, in particular to a sound absorption structure with a full-sealing membrane. BACKGROUND

[0002] Passive (non-source) design of sound absorption is the preferred solution for all noise pollution problems. Traditional design generally requires direct contact between ambient air and sound absorption material, in which the sound absorption material is generally porous material, such as fiber material or foam material, for absorbing sound waves. However, there are still some problems in the direct physical connection between air and sound absorption material. On the one hand, it is impossible to completely prevent, for example, fibers from falling into the ambient air and thereby causing damage to the respiratory system of the human body; on the other hand, for example, dust or other foreign matter can enter the inside of the sound absorption material, thereby accumulating in the sound absorption material, which can reduce the sound absorption properties of the sound absorption material, and bacteria and viruses can also breed inside the sound absorption material; in addition, the directly exposed fibers or foams lack a certain aesthetic appearance as industrial products. SUMMARY

[0003] In order to solve the above problems, the present application provides a sound absorption structure, which is provided with a full-sealing membrane on the outer periphery of the sound absorption material, which can cover all the parts of the sound absorption material exposed to the surrounding environment, thereby completely isolating the ambient air from the sound absorption material.

[0004] The present application provides a sound absorption structure, which comprises a sound absorption material and a full-sealing membrane, wherein the sound absorption material is designed to absorb sound waves, the sound absorption material has at least one exposed area exposed to the surrounding environment, and the sound waves enter the sound absorption material through the exposed area. The full-sealing membrane is designed to cover all the exposed areas of the sound absorption material, wherein the full-sealing membrane extends in a continuous and dense form.

[0005] Preferably, the full-sealing membrane is designed to extend in a pleated configuration.

[0006] Preferably, the sound absorption structure further comprises a support frame, which is arranged at least on the outer surface of the exposed area of the sound absorption material to support the sound absorption material, and at least one perforated area is provided through the support frame.

[0007] Preferably, the full-sealing membrane is arranged between the support frame and the sound absorption material to cover at least the perforated area of the support frame.

[0008] Preferably, the full-sealing membrane is arranged on the outer surface of the support frame to cover at least the perforated area of the support frame.

[0009] Preferably, the thickness of the full-sealing membrane is greater than or equal to 3 microns.

[0010] Preferably, the full-sealing membrane is attached to the support frame at a plurality of fixed points distributed discretely.

[0011] The present application also provides a sound absorption device comprising the sound absorption structure as described above, and further comprising a support medium in which the sound absorption structure is built-in or mounted.

[0012] Preferably, the support medium is designed as a housing having a gas inlet and a gas outlet, and at least two sound absorption structures are held inside the housing in a manner extending parallel to a longitudinal axis of the housing.

[0013] Preferably, the support medium is a vertically extending support, and the sound absorption material extends parallel to and is attached to the support. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a schematic diagram of a sound absorption device in the prior art;

[0015] Figure 2a is a schematic diagram of a support frame being covered by the sound absorption material shown in Figure 1 ; is a schematic diagram of the support frame in from the A direction;

[0016] Figure 2b is a schematic diagram of the support frame in Figure 2a from the B direction;

[0017] Figure 3a is a schematic diagram of a full-sealing membrane being arranged between the support frame and the sound absorption material;

[0018] Figure 3b is a schematic diagram of the full-sealing membrane completely shielding the perforations of the support frame from the B direction;

[0019] Figure 4 is a schematic diagram of a full-sealing membrane being arranged outside the support frame;

[0020] Figure 5 is a schematic diagram of another sound absorption device according to the present application;

[0021] Figure 6a is a front view of one example of a sound absorption structure with a pleated design;

[0022] Figure 6b is a cross-sectional view of the example shown in Figure 6a ; is a cross-sectional view of the example shown in

[0023] Figure 7 is a schematic diagram of another example of a sound absorption structure with a pleated design;

[0024] Figure 8a is a sinusoidal configuration of a full seal membrane;

[0025] Figure 8b Figure 8b is a sawtooth configuration of a full seal membrane;

[0026] Figure 8c Figure 8c is a butterfly configuration of a full seal membrane;

[0027] Figure 9 Figure 9a is an example of a corrugation extending in a direction parallel to the gas flow direction;

[0028] List of Reference Signs

[0029] 1. housing; 2. gas inlet; 3. gas outlet; 4. sound absorbing material; 5. support frame; 6. perforations; 7. full seal membrane; 8. support DETAILED DESCRIPTION

[0030] Referring now to the drawings, illustrative embodiments of the structure disclosed herein will be described in detail. Although the drawings presented herein are intended to present some embodiments of the present application, the drawings are not necessarily drawn to scale and certain features can be exaggerated, removed or sectioned for the sake of better understanding and explanation of the disclosure. Some components in the drawings can be adjusted in position according to actual needs without affecting the technical effects. In the following figures, similar components are designated by the same reference numerals.

[0031] There are two typical spatial configurations of sound absorbing devices. Specifically, one configuration is a channel absorber known in the prior art as shown in Figure 1 The channel absorber has a housing 1 with a gas inlet 2 and a gas outlet 3 respectively formed at both ends of the housing 1, and the gas flows unidirectionally from the gas inlet 2 into the housing 1 and exits the housing 1 from the gas outlet 3. Inside the housing 1, there are a plurality of sound absorbing materials 4 (in the form of sound absorbing sheets in Figure 1 the drawings) extending parallel to the longitudinal axis (not shown) of the housing, and there are gaps between adjacent sound absorbing materials 4 to form a plurality of longitudinal channels for the gas to flow through. When the vibrating air enters the sound absorbing materials 4, it will be gradually absorbed during the downstream flow. At this time, most of the surface area of the sound absorbing materials 4 (except for the fixed position between the housing) is exposed to the gas environment inside the housing 1, and the sound waves can enter the sound absorbing materials through the exposed area of the sound absorbing materials 4 to achieve sound absorption.

[0032] Further reference is made to Figure 2a and Figure 2bA support frame 5, typically in the form of a protective plate with perforations 6, is typically arranged on the outer periphery of the sound absorbing material 4, so as to perform a positioning support function for the sound absorbing material 4, while not hindering the physical communication of ambient air with the sound absorbing material 4. In particular, at least one perforated area (an area range with a plurality of perforations) is provided through the outer peripheral wall of the support frame 5, so as to allow the communication of ambient air with the sound absorbing material 4 and to prevent the fibers (when the sound absorbing material is in the form of a fibrous material) from being carried away by the air flow. As shown in Figures 2a and Figure 2b 2b, the perforated areas can be provided on the top and bottom walls of the support frame 5. Of course, the person skilled in the art will understand that the perforated areas can be provided according to the relative position of the direction of the air flow with respect to the sound absorbing material, which is shown here only by way of example and is not exhaustive. Typically, the thickness of the outer peripheral wall of the support frame 5 is preferably 1 mm. The diameter of the perforations 6 is typically between 2 and 5 mm, and the perforation rate is in the range of 20% to 25%, the perforation rate being defined here as the ratio of the area of the perforations to the entire surface area of the support frame. The shape of the perforations 6 is not limited here and can be circular, rectangular or any other shape. When the support frame 5 is used, the area of the exposed region of the sound absorbing material 4 exposed to the surrounding environment will be considerably smaller and will be limited to the portion of the support frame 5 with the perforations 6.

[0033] Figures 3a-3b and Figure 4 Figures 3a and 3b show a schematic view of the provision of a full-sealing membrane 7 for a structure similar to that according to Figures 2a and Figure 2b 2b, in which Figure 3b the view is from the B direction Figure 3a , Figure 3b the shape of the perforations differs from that in Figure 2b . Given the typically small thickness of the full-sealing membrane 7, it is still preferable to need the support frame 5 described above in order to maintain the basic shape of the sound absorbing material 4. At the same time, studies have shown that a support frame 5 with a perforation rate greater than 23% has almost no effect on the sound absorption performance of the sound absorbing material 4.

[0034] In order to be able to cover the remaining exposed region of the sound absorbing material 4 (corresponding to the position of the perforations), in the case of Figures 2a and Figure 2b 2b, in which only the top and bottom walls of the support frame 5 have perforated areas, the full-sealing membrane 7 needs to be arranged on the top and bottom sides of the sound absorbing material 4, so as to cover the positions of the sound absorbing material 4 that can still be exposed to the surrounding environment through the perforated areas of the support frame 5. The full-sealing membrane 7 can be arranged between the support frame 5 and the sound absorbing material 4, as shown in Figure 3a and Figure 3b , or can be arranged on the top and bottom sides of the sound absorbing material 4, as shown in Figure 4The full-sealing membrane 7 is shown to be arranged outside the support frame 5, which can be determined according to the shape and installation difficulty of the specific sound-absorbing material 4, etc. Arranging the full-sealing membrane 7 inside the support frame can better protect the full-sealing membrane 7. Arranging the full-sealing membrane 7 outside the support frame 5 can provide a smoother outer surface for the entire sound-absorbing structure, thereby facilitating, for example, the flow of gas in the passage within the housing 1.

[0035] Regardless of whether the full-sealing membrane is arranged outside or inside the support frame, it is designed to be fixed to the support frame at several key structural positions, i.e., attached to the support frame through multiple discrete distribution fixing points. In addition, it should be noted that the full-sealing membrane can not be bonded to the support frame with the entire contact surface. If the full-sealing membrane is completely bonded to the support frame, the only part of the membrane that can still allow sound to pass through is the part corresponding to the perforations of the support frame, the stiffness of the diaphragm increases sharply when crossing a small distance and will destroy the performance of medium to low frequencies. Therefore, loose attachment with several fixing points is the most preferred.

[0036] Figure 5 Another typical spatial configuration of the sound-absorbing device is shown, i.e., where the sound-absorbing material 4 will be hung to a vertically extending support 8, such as a wall in a room, which is particularly suitable for indoor use. Specifically, as shown, the side of the sound-absorbing material 4 facing the wall will be directly attached to the wall. Preferably, the support frame 5 is installed on the other side of the sound-absorbing material exposed to the surrounding environment to maintain the shape of the sound-absorbing material 4. The full-sealing membrane 7 can be arranged between the support frame 5 and the sound-absorbing material 4. Of course, although not shown, the full-sealing membrane 7 can also be arranged on the outer surface of the support frame 5 (i.e., the side away from the sound-absorbing material).

[0037] For such a configuration of the sound-absorbing device, sound waves can enter the sound-absorbing material 4 in a way perpendicular to the sound-absorbing material (normal incidence) or inclined to the sound-absorbing material (oblique incidence). If the sound waves can impact the sound-absorbing device from various angles, this way is called random incidence. The principle of action of the full-sealing membrane in this embodiment is the same as above, but the thickness of the full-sealing membrane used can vary depending on the material of the full-sealing membrane used and the configuration of the specific sound-absorbing material, which is not limited herein.

[0038] Conventional wisdom holds that the lack of direct connection between sound-absorbing materials and the ambient air prevents sound waves from entering the material, thus reducing its absorption effectiveness. This is true for most high-frequency sounds (e.g., above 1kHz), but it is not true for low-frequency sounds (e.g., below 200Hz) and mid-frequency sounds (200-1000Hz). For low- and mid-frequency sounds, given a properly chosen membrane thickness, the sound will cause the membrane to vibrate sufficiently to pass through it. Since the membrane vibration is caused by the interfering sound, it does not generate any additional sound.

[0039] When sound waves hit the membrane, the membrane vibrates, and the sound waves are transmitted to the sound-absorbing material below the membrane. The acoustic effect of the membrane is mainly the inertia added to the air movement, which is evaluated by the mass ratio. Specifically, the mass ratio m1 is calculated as

[0040] m1=ρ m s / ρ0 h

[0041] Among them, ρ m refers to the material density of the membrane, s refers to the thickness of the membrane, ρ0 refers to the air density, and h refers to the typical air depth of the sound wave, such as the height of the air passing through the space in the pipe or the thickness of the sound absorbing material. When the membrane material is a 10-micron stainless steel membrane and the sound absorbing material is selected with a typical size of h=0.1m, the mass ratio is m1=7850×10 -5 / (1.225×0.1)=0.64. Currently, there's no clear limit for m1 to determine whether a sound wave is mostly reflected by the membrane or penetrates it, but values ​​equal to or less than 1 are considered beneficial for sound transmission. This, of course, also depends on the frequency of the sound wave. For low-frequency sound waves, the membrane mass ratio helps establish low-frequency resonance and promotes sound absorption, so a high mass ratio, such as 10 or even 100, can be used. However, larger values ​​of m1 significantly hinder the passage of high-frequency sound waves. For such frequencies, existing membranes are too thick. Although calculations and experiments have shown that reducing membrane thickness will facilitate the passage of high-frequency sound waves, processing becomes complex, costly, and fragile when the material thickness is below a certain value. Currently, 5-micron-thick membranes can be produced on the market, and as processing technology matures, costs will drop even further, potentially enabling the use of 5-micron or even 3-micron membranes.

[0042] In order to avoid using expensive ultra-thin membranes, the present invention also provides another method for solving the problem of high-frequency sound passing through the fully sealed membrane, namely, providing a pleated design to increase the contact area between ambient air and the sound-absorbing material.

[0043] Figure 6a 、 6b and Figure 7A schematic view of the full-sealing membrane 7 in a pleated configuration is shown. In Figure 6a and 6b the full-sealing membrane 7 is arranged outside the support frame 5, in this figure the sound absorbing material is configured in a cylindrical shape. In Figure 7 the full-sealing membrane 7 is arranged between the support frame 5 and the sound absorbing material 4. In this context "pleated" is a general term referring to the situation where the full-sealing membrane has an increased surface area due to being folded. The pleating can comprise a variety of configurations, typical configurations can for example be sinusoidal as shown in Figure 8a , saw-toothed as shown in Figure 8b and butterfly-shaped as shown in Figure 8c .

[0044] In the configuration shown in Figure 7 the gas flow can travel perpendicular to the direction of the pleats, the direction of the gas flow is indicated by arrow C. The use of a smooth outer surface enables the support of the gas flow on the outside and avoids high resistance. Otherwise the gas flow across the peaks and valleys of the pleats in the membrane can cause a greater resistance. However, if the flow velocity of the gas is within a reasonable range, the pleats of the membrane can act as an air bearing for the gas flow passing through it, which can also reduce the resistance. Of course, the direction of the gas flow D can also be parallel to the direction of the pleats, as shown in Figure 9 . In this context the direction of the pleats is not specifically limited, the skilled person can design it according to the actual circumstances of the construction site.

[0045] The pleated design of the full-sealing membrane enables an increase in the total surface area of the membrane, which compensates for the partial sound reflection of the membrane for high-frequency sound. The use of this design also enables an increase in the aesthetics of the device.

[0046] With regard to the material of the full-sealing membrane, in principle the membrane can be made of any material, the main acoustic influence is considered in its surface mass density p m s. Unless the material is specially designed, the damping performance of the pure material is usually negligible. In this application, the function of the membrane is not sound absorption, the damping of the natural material has little contribution to sound absorption compared to the sound absorbing material. Therefore, the selection of the chemical composition of the membrane is not determined by its sound absorption performance, but can be determined by other factors such as fire resistance, corrosion resistance, aesthetics, product cost, etc. If the sound absorbing material does not require absolute air tightness, the membrane can even be made of tightly woven silk or the like.

[0047] In addition, it should be noted that although the supporting frame is used in the example embodiments of the present application, it is not an essential component. For a hard acoustic material, a full-sealing membrane can be directly fitted on the outer surface of the acoustic material to cover all the exposed areas of the acoustic material exposed to the surrounding environment. When a supporting frame is used, it is at least arranged on the outer surface of the exposed area of the acoustic material to prevent the acoustic material from deforming. For example, for an acoustic material located in the middle position, the entire outer periphery thereof can be exposed to the surrounding air environment, so the supporting frame can be fitted on the entire outer periphery of the acoustic material. However, for a structure as shown in FIG. 1, since the side of the acoustic material facing the wall is not in contact with the environment and is already supported by the wall, the supporting frame can not be arranged on this side. Figure 1 Figure 5

[0048] In this context, the "full-sealing membrane" refers to a continuous and dense covering without macroscopically visible holes and capable of separating the acoustic material (inside) and the surrounding air environment (outside), which can achieve the goal of preventing the acoustic material inside from entering the surrounding air environment, or preventing the dust in the external air from entering the acoustic material. However, this does not mean that there is no air molecule-scale communication between the inside and the outside, so it is not necessary to have as high airtightness requirement as food packaging. On the contrary, if several air vents must be opened for air pressure balance between the inside and the outside without affecting the function of separating the inside and the outside, it should also be considered as the full-sealing membrane of the present application.

[0049] By physically surrounding the acoustic material with the full-sealing membrane to isolate it from the surrounding environment, the direct contact between the ambient air and the acoustic material is reduced. Sound in the low to medium frequency range can still easily pass through the membrane. When there is a large amount of high-frequency sound, the pleated design will be able to compensate for the reflection of the membrane to the sound. The product according to the present application will achieve effective absorption of sound in various ranges.

[0050] In addition to solving the above problems of environmental air pollution and deterioration of product performance, the use of the full-sealing membrane can also increase the selection of porous material varieties. For example, some materials are very economical and cannot be used without sealing, but can be used with a sealing design. In addition, the pleated design can be combined with artistic features to further improve the aesthetics of the entire acoustic device.​​

Claims

1. A sound absorbing structure, characterized by, Comprising: a sound absorbing material (4) designed to absorb sound waves, said sound absorbing material having at least one exposed area exposed to the surrounding environment through which said sound waves enter said sound absorbing material; a full-sealing membrane (7) designed to cover all exposed areas of said sound absorbing material (4), wherein said full-sealing membrane extends in a continuous and dense form; a support frame (5) arranged at least on the outer surface of said exposed areas of said sound absorbing material to support said sound absorbing material, at least one perforated area being provided through said support frame; wherein said full-sealing membrane contacts said support frame and is loosely attached to said support frame at a plurality of discrete fixing points, and said full-sealing membrane is in a state of sufficient vibration in the area between fixing points to transmit sound waves to said sound absorbing material, so as to avoid the rigidity of said full-sealing membrane increasing.

2. The sound absorbing structure according to claim 1, characterized in that, Said full-sealing membrane is designed to extend in a pleated configuration.

3. The sound absorbing structure according to claim 1, characterized by Said full-sealing membrane is arranged between said support frame and said sound absorbing material to cover at least the perforated area of said support frame.

4. The sound absorbing structure according to claim 1, characterized by Said full-sealing membrane is arranged on the outer surface of said support frame to cover at least the perforated area of said support frame.

5. The sound absorbing structure according to claim 1, wherein The thickness of said full-sealing membrane is greater than or equal to 3 microns.

6. A sound absorbing device, characterized by A sound absorbing structure according to any one of the preceding claims, further comprising a supporting medium in which said sound absorbing structure is built-in or mounted.

7. The sound absorbing device according to claim 6, characterized in that Said supporting medium is designed to accommodate a housing, said housing having a gas inlet and a gas outlet, and at least two sound absorbing structures are held inside said housing in a manner extending parallel to the longitudinal axis of said housing.

8. The sound absorbing device of claim 6, wherein Said supporting medium is a vertically extending support, said sound absorbing material extending parallel to and being attached to said support.

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