CN114648972A

CN114648972A - Sound absorbing structure and sound absorbing device

Info

Publication number: CN114648972A
Application number: CN202011500967.8A
Authority: CN
Inventors: 黄立锡
Original assignee: Zhejiang Institute Of Research And Innovation University Of Hong Kong
Current assignee: Zhejiang Institute Of Research And Innovation University Of Hong Kong
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2022-06-21
Also published as: WO2022127843A1

Abstract

The invention provides a sound absorbing structure comprising a sound absorbing material and a fully sealed 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. A fully sealed membrane is designed to cover all exposed areas of the sound absorbing material, wherein the fully sealed membrane extends in a continuous, dense fashion. The above-mentioned full-sealing film isolates the sound-absorbing material from the surrounding environment, thereby preventing the fibers or foams inside the sound-absorbing material from entering the surrounding air environment, or preventing dust in the outside air from entering the sound-absorbing material.

Description

Sound absorbing structure and sound absorbing device

Technical Field

The invention relates to a sound absorption structure, in particular to a sound absorption structure with a full-sealing film.

Background

Passive (passive) design of sound absorption is the preferred solution to all noise pollution problems. Conventional designs typically require direct contact between the ambient air and the sound absorbing material, which typically employs porous materials, such as fibrous or foam materials, for absorbing sound waves. However, such direct physical communication of air with sound-absorbing materials still presents problems, on the one hand, such as the fact that the shedding fibres cannot be completely prevented from entering the ambient air and thus causing damage to the respiratory system of the human body; on the other hand, for example, dust or other foreign substances may enter the inside of the sound-absorbing material to be accumulated in the sound-absorbing material, which may reduce the sound-absorbing characteristics of the sound-absorbing material, and bacteria, viruses, and the like may also grow inside the sound-absorbing material; in addition, the directly exposed fibers or foams lack certain aesthetics as an industrial finish.

Disclosure of Invention

In order to solve the above problems, the present invention provides a sound absorbing structure in which an all-seal film capable of covering all portions of the sound absorbing material to be exposed to the surrounding environment is disposed at the outer periphery of the sound absorbing material, thereby completely isolating the ambient air from the sound absorbing material.

The invention provides a sound absorbing structure comprising a sound absorbing material and a fully sealed 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. A fully sealed membrane is designed to cover all exposed areas of the sound absorbing material, wherein the fully sealed membrane extends in a continuous, dense fashion.

Preferably, the full sealing membrane is designed to extend in a pleated configuration.

Preferably, the sound absorbing structure further comprises a support frame disposed at least on an outer surface of the exposed region of the sound absorbing material to support the sound absorbing material, and at least one perforated region is perforated on the support frame.

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

Preferably, the full sealing film is arranged on the outer surface of the support frame to cover at least the perforated area of the support frame.

Preferably, the thickness of the fully sealed film is greater than or equal to 3 micrometers.

Preferably, the fully sealed membrane is attached to the support frame at a plurality of fixed points distributed discretely.

The invention also provides a sound absorption device which comprises the sound absorption structure and a supporting medium with the sound absorption structure arranged inside or mounted inside.

Preferably, the support medium is designed as a receiving housing with a gas inlet and a gas outlet, at least two sound-absorbing structures being held inside the receiving housing in such a way that they extend parallel to the longitudinal axis of the receiving housing.

Preferably, the support medium is a vertically extending support, and the sound absorbing material extends parallel to and is attached to the support.

Drawings

FIG. 1 is a schematic view of a muffler assembly according to the prior art;

FIG. 2a is a schematic view of a support frame being placed over the sound absorbing material shown in FIG. 1;

FIG. 2b is a schematic view of the support frame of FIG. 2a as viewed from direction A;

FIG. 3a is a schematic view of an all-seal membrane disposed between a support frame and a sound absorbing material;

FIG. 3B is a schematic view of the fully sealed membrane completely blocking the perforations of the support frame as viewed from direction B;

FIG. 4 is a schematic view of a fully sealed membrane disposed outside of a support frame;

FIG. 5 is a schematic view of another sound absorbing device of the present invention;

FIG. 6a is a front view of one example of a sound absorbing structure with a pleated design;

FIG. 6b is a cross-sectional view of the example shown in FIG. 6 a;

FIG. 7 is a schematic view of another example of a sound absorbing structure with a pleated design;

FIG. 8a is a sinusoidal configuration of the full seal membrane;

FIG. 8b is a zigzag configuration of the full seal membrane;

FIG. 8c is a butterfly configuration of the holo-seal membrane;

FIG. 9 is an example of a gas flow direction parallel to the direction of extension of the membrane pleats;

list of reference numerals

1. An accommodating case; 2. a gas inlet; 3. a gas outlet; 4. a sound absorbing material; 5. a support frame; 6. perforating; 7. a full-sealing film; 8. supporting member

Detailed Description

Referring now to the drawings, illustrative aspects of the disclosed structure will be described in detail. Although the drawings are provided to present some embodiments of the invention, the drawings are not necessarily to scale of particular embodiments, and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. The position of some components in the drawings can be adjusted according to actual requirements on the premise of not influencing the technical effect. In the various figures that follow, like parts bear the same reference numerals.

The sound absorber has two typical spatial configurations. In particular, one configuration is a channel absorber known in the art as shown in fig. 1. The channel sound absorber is provided with a containing shell 1, a gas inlet 2 and a gas outlet 3 are respectively arranged at two ends of the containing shell 1, and gas enters the containing shell 1 from the gas inlet 2 and leaves the containing shell 1 from the gas outlet 3 in a one-way flowing manner. Inside the containment casing 1 a plurality of sound-absorbing materials 4 (in the form of muffling sheets in fig. 1) are arranged, extending parallel to the longitudinal axis of the casing (not shown), with spaces between adjacent sound-absorbing materials 4 to form a plurality of longitudinal channels for the gas to flow through. As the vibrating air enters the sound absorbing material 4, it is gradually absorbed as it flows downstream. Most of the surface area of the sound-absorbing material 4 (except for the fixed position with the housing case) is exposed to the gas environment in the housing case 1, and sound waves can enter the sound-absorbing material through the exposed area of the sound-absorbing material 4, so that the sound-absorbing effect is achieved.

With further reference to fig. 2, a support frame 5 is generally disposed on the outer peripheral surface of the sound absorbing material 4, and the support frame 5 is generally in the form of a protective plate with perforations 6, so as to not hinder the physical communication between the ambient air and the sound absorbing material 4 while serving as a positioning support for the sound absorbing material 4. Specifically, at least one perforated area (area range with a plurality of perforations) is perforated on the outer peripheral wall of the support frame 5 to allow ambient air to communicate with the sound absorbing material 4 and to prevent fibers (when the sound absorbing material is a fibrous material) from being carried away by the airflow. As shown in fig. 2, perforated regions may be provided in the top and bottom walls of the support frame 5, respectively. It will be understood by those skilled in the art that the perforated region may be formed according to the relative position of the gas flow direction and the sound absorbing material, and is shown schematically and not exhaustive herein. In general, the thickness of the outer peripheral wall of the support frame 5 is preferably 1 mm. The perforations 6 are typically 2-5 mm in diameter and have a perforation rate in the range of 20% -25%, where the perforation rate is defined as the ratio of the area of the perforations to the total surface area of the support frame. The shape of the perforations 6 is not limited herein and may be circular, rectangular or any other shape. When the support frame 5 is used, the area of the exposed area of the sound-absorbing material 4 exposed to the surrounding environment will be much smaller and will be limited to the portion corresponding to the support frame 5 with the perforations 6.

Fig. 3 and 4 show a schematic view of providing a fully sealed membrane 7 for a structure similar to that according to fig. 2, wherein fig. 3B is a view from the direction B of fig. 3a, the shape of the perforations in fig. 3B differing from the shape of the perforations in fig. 2B. In view of the generally small thickness of the full-seal film 7, it is still preferable that the above-described support frame 5 is required to maintain the basic shape of the sound absorbing material 4. Meanwhile, studies have shown that the influence of the supporting frame 5 having a perforation rate of more than 23% on the sound absorbing performance of the sound absorbing material 4 is almost zero.

In order to be able to cover the remaining exposed areas of the sound-absorbing material 4 (corresponding to the location of the perforations), in the case shown in fig. 2 with perforated areas only on the top and bottom walls of the support frame 5, full-sealing membranes 7 need to be arranged on the top and bottom sides of the sound-absorbing material 4 to cover the locations of the sound-absorbing material 4 that may still be exposed to the surrounding environment through the perforated areas of the support frame 5. The full-sealing film 7 may be disposed between the support frame 5 and the sound-absorbing material 4 as shown in fig. 3, or may be disposed outside the support frame 5 as shown in fig. 4, which may be determined depending on factors such as the shape and installation difficulty of the specific sound-absorbing material 4. The arrangement of the full-sealing membrane 7 inside the support frame enables a better protection of this full-sealing membrane 7. The provision of the full-seal membrane arrangement 7 outside the support frame 5 can provide a smoother outer surface of the overall sound-absorbing structure, for example to promote the flow of gas in the channels inside the containment casing 1.

Whether this full sealing membrane is to be arranged outside or inside the support frame, it is designed to be fixed to the support frame at several critical structural positions, i.e. by a plurality of discrete distributed fixation points. In addition, it should be noted that the whole sealing film may not be adhered to the support frame over the entire contact surface. If the hermetically sealed membrane is fully bonded to the support frame, the only part of the membrane that is also capable of allowing sound to pass through is the part corresponding to the perforations of the support frame, the stiffness of the membrane when spanning small distances increases drastically and will destroy the performance of medium to low frequencies. Whereby loose attachment with several fixation points is most preferred.

Fig. 5 shows another typical spatial configuration of the sound absorption device, i.e. a configuration in which the sound absorption material 4 is to be suspended to a vertically extending support 7, such as a wall in a room, which is particularly suitable for indoor use. In particular, as shown, the side of the sound absorbing material 4 facing the wall will be attached directly to the wall. Preferably, a 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. A full sealing film 7 may be arranged between the support frame 5 and the sound-absorbing material 4. Of course, although not shown, the whole sealing film 7 may also be arranged on the outer surface of the support frame 5 (i.e., the side facing away from the sound absorbing material).

With the sound absorber of this configuration, the sound waves can enter the sound absorber 4 perpendicularly to the sound absorber (normal incidence) or obliquely to the sound absorber (oblique incidence). This is referred to as random incidence if the sound waves are able to impact the sound absorber from various angles. The function principle of the full-seal membrane in this embodiment is the same as above, but the thickness of the full-seal membrane used in particular may vary depending on the material of the full-seal membrane used and the configuration of the sound absorbing material in particular, and is not limited herein.

The traditional thinking is that the indirect communication between the sound absorbing material and the ambient air prevents sound waves from entering the sound absorbing material, thereby influencing the sound absorbing effect of the sound absorbing material. This is true for most high frequency sounds (e.g. greater than 1kHz), but not for low frequency sounds (e.g. below 200Hz) and medium frequency sounds (200-1000 Hz). For low and medium frequency sounds, with a reasonable choice of membrane thickness, the sound will cause the membrane to vibrate sufficiently and thus to pass through the membrane. Since the vibration of the membrane is caused by the disturbing sound, it does not generate additional sound.

When sound waves strike the membrane, the membrane vibrates with it, whereby the sound waves are transmitted to the sound absorbing material located below the membrane. The acoustic effect of the membrane is mainly the increased inertia of the air movement, which is evaluated by the mass ratio. Specifically, the mass ratio m₁Is calculated in a manner that

m₁＝ρ_m s/ρ₀h

Where ρ is_mIs the material density of the film, s is the thickness of the film, p₀Referring to air density, h refers to the typical air depth traveled by sound waves, such as the height of the air passing space in the duct or the thickness of the sound absorbing material. When the membrane material adopts a stainless steel membrane with the thickness of 10 micrometers and the sound absorption material adopts a typical size h of 0.1m, the mass ratio is m₁＝7850×10^-5And/(1.225 × 0.1) ═ 0.64. At present, m is not present₁Is used to determine whether the sound waves are mostly reflected back by the membrane or penetrate the membrane, but values equal to or less than 1 are considered to be beneficial for sound passage. Of course this is also related to the frequency of the sound. For low frequency sound waves, where the membrane mass ratio helps to establish low frequency resonances and promotes sound absorption, a high mass ratio, such as 10 or even 100, may be used. But when m is₁A larger value of (a) will significantly impede the passage of high frequency sound waves. For such frequencies, existing films will be too thick. Although both calculations and experiments have shown that reducing the thickness of the film is more conducive to the passage of high frequency sound waves, the material is complicated, expensive and fragile when the thickness is less than a certain value. At present, the material film with the thickness of 5 microns can be produced on the market, and the cost of the material film is reduced along with the maturation of the processing technologyTo lower, and thus, the use of 5 or even 3 micron films of material is expected.

To avoid the use of expensive ultra-thin membranes, the present invention also provides another solution to the problem of high frequency sound passing through a fully sealed membrane, namely providing a corrugated design to increase the contact area between the ambient air and the sound absorbing material.

Figures 6a, 6b and 7 show a schematic view of the full sealable membrane 7 in its pleated configuration. Wherein in fig. 6a and 6b the full sealing membrane 7 is arranged outside the support frame 7, in which the sound-absorbing material is configured cylindrically. In fig. 7, the full-sealing membrane 7 is arranged between the support frame 5 and the sound-absorbing material 4. The term "wrinkled" is used herein only as a general term, and refers to the case where the surface area of the full packing film is increased due to being bent. The accordion shape may include a variety of configurations, and typical configurations may be, for example, sinusoidal as shown in FIG. 8a, saw tooth as shown in FIG. 8b, and butterfly as shown in FIG. 8 c.

In the configuration shown in fig. 7, the air flow may run perpendicular to the direction of extension of the pleats, the air flow direction being indicated by arrow C. The use of a smooth outer surface can support outside airflow and avoid high drag. Otherwise, the air flow may cause more resistance as it traverses the peaks and valleys of the folds in the membrane. But if the flow velocity of the gas is within a reasonable range, it may also act to reduce drag as the folds of the membrane may act as an air bearing for the gas flow passing through. Of course, as shown in fig. 9, the air flow direction D may also be parallel to the extension direction of the pleats. The extending direction of the wrinkles is not particularly limited in this context, and the technician may design the wrinkles according to the actual environment of the construction site.

The corrugated design of the fully sealed membrane allows for an increase in the total surface area of the membrane, thereby compensating for the partial acoustic reflection of high frequency sounds by the membrane. The adoption of the design can also increase the aesthetic property of the device.

With regard to the material of the omniseal membrane, the membrane can in principle be produced from any material, the main acoustic influence being taken into account by its surface mass density ρ_mAnd s. The damping performance of the pure material is improved unless the material is specially designedOften negligible. In the present application, the function of the membrane is not sound absorption, the damping of natural materials contributing little to sound absorption compared to sound absorbing materials. Thus, the choice of chemical composition of the film is not determined by its sound absorption properties, but may be determined by other factors such as fire resistance, corrosion resistance, aesthetics, product cost, and the like. The membrane may even be a tightly woven silk or the like if the sound absorbing material does not require absolute air tightness.

In addition, it should be noted that although the support frame is used in the illustrated embodiments of the present invention, it is not a necessary component, and for the more rigid sound absorbing material, an all-seal membrane may be directly placed over the outer surface of the sound absorbing material to cover all exposed areas of the sound absorbing material exposed to the ambient environment. When a support frame is employed, it is disposed at least on the outer surface of the exposed region of the sound absorbing material, thereby preventing the sound absorbing material from being deformed. For example, for the sound absorber in the middle position of fig. 1, the entire periphery of the sound absorber may be exposed to the ambient air environment, so the support frame may be fitted over the entire periphery of the sound absorber. However, for the construction shown in fig. 5, no supporting frame may be required on this side, since the side of the sound-absorbing material facing the wall is not in contact with the environment and is already supported by the wall.

In this context, "fully sealed membrane" refers to a continuous and densely extended cover without macroscopic holes in it and capable of separating the sound-absorbing material (inside) from the ambient air environment (outside), which enables the object of preventing fibers or foam inside the sound-absorbing material from entering the ambient air environment, or preventing dust in the outside air from entering the sound-absorbing material. But this does not represent an internal-external communication without molecular dimensions of air, and therefore does not require as high a hermetic seal as food packaging. On the contrary, if several air holes must be formed without affecting the above-mentioned function of the inner and outer partitions because of the requirement of the balance of the air pressure between the inner and outer sides, it should be regarded as the full-sealing film of the present invention.

By physically surrounding the sound absorbing material with a fully sealed membrane to isolate it from the surrounding environment, direct contact between ambient air and the sound absorbing material is reduced. Sound in the low to mid frequency range can still easily pass through the membrane. When there is a lot of high frequency sound, the corrugated design will be able to compensate for the reflection of sound by the membrane. The product according to the invention will achieve an effective absorption of sound in all ranges.

Besides solving the problems of environmental air pollution, poor product performance and the like, the use of the full-sealing film can increase the selection of porous material varieties. For example, some materials are very economical and cannot be used without a seal, and become available with a seal design. While others may be directly available from nature and promote sustainability. In addition, the corrugated design may be combined with artistic features to further enhance the aesthetics of the overall sound absorber.

Claims

1. A sound absorbing structure, 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-seal membrane (7) designed to cover all exposed areas of the sound-absorbing material (4), wherein the full-seal membrane extends in a continuous, dense manner.

2. The sound absorbing structure of claim 1 wherein the full sealing membrane is designed to extend in a convoluted configuration.

3. The sound absorbing structure of claim 2, further comprising a support frame disposed at least on an outer surface of the exposed region of the sound absorbing material to support the sound absorbing material, the support frame having at least one perforated region perforated therethrough.

4. A sound-absorbing structure according to claim 3, wherein the omniseal membrane is arranged between the support frame and the sound-absorbing material to cover at least the perforated region of the support frame.

5. A sound-absorbing structure as claimed in claim 3, wherein the omniseal membrane is arranged on the outer surface of the support frame to cover at least the perforated region of the support frame.

6. The sound absorbing structure of claim 1 wherein the fully sealed membrane has a thickness of greater than or equal to 3 microns.

7. A sound absorbing structure according to claim 3, wherein the omniseal membrane is attached to the support frame at a plurality of fixing points distributed discretely.

8. A sound-absorbing device comprising a sound-absorbing structure according to any one of the preceding claims, and a support medium in which the sound-absorbing structure is built or in which the sound-absorbing structure is mounted.

9. A sound-absorbing device as claimed in claim 8, wherein the support medium is designed as a containment casing with a gas inlet and a gas outlet, at least two sound-absorbing structures being held inside the containment casing in such a way that they extend parallel to the longitudinal axis of the containment casing.

10. A sound-absorbing device as claimed in claim 8, wherein the support medium is a vertically extending support member, and the sound-absorbing material extends parallel to the support member and is attached to the support member.