WO2022127843A1

WO2022127843A1 - Sound absorbing structure and sound absorbing device

Info

Publication number: WO2022127843A1
Application number: PCT/CN2021/138641
Authority: WO
Inventors: 黄立锡
Original assignee: 香港大学浙江科学技术研究院
Priority date: 2020-12-18
Filing date: 2021-12-16
Publication date: 2022-06-23
Also published as: CN114648972A

Abstract

A sound absorbing structure, comprising a sound absorbing material (4) and a hermetic sealing membrane (7). The sound absorbing material (4) is designed to absorb sound waves; the sound absorbing material (4) has at least one exposed area exposed in the surrounding environment; sound waves enter the sound absorbing material (4) by means of the exposed area. The hermetic sealing membrane (7) is designed to cover all exposed areas of the sound absorbing material (4), and the hermetic sealing membrane (7) extends in a continuous dense form. The hermetic sealing membrane (7) isolates the sound absorbing material (4) from the surrounding environment, thereby preventing fibers or foam material inside the sound absorbing material (4) from entering the surrounding air environment, or preventing dust in the external air from entering the sound absorbing material (4).

Description

Sound-absorbing structures and sound-absorbing devices

technical field

The invention relates to a sound absorption structure, in particular to a sound absorption structure with a fully sealed membrane.

Background technique

Passive (passive) designs for sound absorption are the preferred solution to all noise pollution problems. Traditional designs generally require direct contact between ambient air and sound absorbing materials, which generally employ porous materials, such as fibrous materials or foam materials, for absorbing sound waves. However, there are still some problems with such direct physical communication of air and sound-absorbing material. On the one hand, it is impossible to completely prevent, for example, shed fibers from entering the ambient air and thereby causing damage to the human respiratory system; on the other hand, for example, dust or Other foreign objects, etc. will enter the sound-absorbing material and accumulate in the sound-absorbing material, which will reduce the sound-absorbing properties of the sound-absorbing material, and bacteria and viruses may also breed inside the sound-absorbing material; in addition, directly exposed fibers or As an industrial product, foam lacks certain aesthetics.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a sound absorbing structure, which is provided with a fully sealed film on the outer periphery of the sound absorbing material. The ambient air is completely isolated from the sound absorbing material.

The present invention provides a sound absorbing structure comprising a sound absorbing material and a hermetically sealed membrane, wherein the sound absorbing material is designed to absorb sound waves, the sound absorbing material has at least one exposed area exposed to the surrounding environment, the Sound waves enter the sound absorbing material through the exposed area. The hermetic membrane is designed to cover all exposed areas of the sound absorbing material, wherein the hermetic membrane extends in a continuous dense form.

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

Preferably, the sound absorbing structure further includes a support frame, the support frame is arranged at least on the outer surface of the exposed area of the sound absorbing material to support the sound absorbing material, the support frame is provided with At least one perforated area.

Preferably, the hermetic 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 hermetic membrane 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 full sealing film is greater than or equal to 3 microns.

Preferably, the hermetic membrane is attached to the support frame at discretely distributed fixed points.

The present invention also provides a sound absorption device, which includes the above sound absorption structure, and also includes a support medium with the sound absorption structure built in or installed with the sound absorption structure.

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

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

Description of drawings

Fig. 1 is a schematic diagram of a muffler device in the prior art;

Figure 2a is a schematic view of a support frame being covered on the sound absorbing material shown in Figure 1;

Figure 2b is a schematic view of the support frame in Figure 2a viewed from the A direction;

Figure 3a is a schematic diagram of the fully sealed membrane arranged between the support frame and the sound absorbing material;

Figure 3b is a schematic view of the fully sealed film viewed from the direction B that completely covers the perforations of the support frame;

FIG. 4 is a schematic diagram of the fully sealed membrane arranged outside the support frame;

5 is a schematic diagram of another sound absorbing device of the present invention;

Figure 6a is a front view of an example of a sound absorbing structure with a pleated design;

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

7 is a schematic diagram of another example of a sound absorbing structure with a pleated design;

Figure 8a is a sinusoidal configuration of a hermetic membrane;

Figure 8b is a serrated configuration of a hermetically sealed membrane;

Figure 8c is the butterfly-like configuration of the fully sealed membrane;

FIG. 9 is an example of the direction of airflow parallel to the direction in which the pleats of the membrane extend;

List of reference signs

1. accommodating shell; 2. gas inlet; 3. gas outlet; 4. sound absorbing material; 5. supporting frame; 6. perforation;

Detailed ways

Referring now to the accompanying drawings, the schematic scheme of the structure disclosed in the present invention will be described in detail. Although the drawings are provided to present some embodiments of the present invention, the drawings are not necessarily to scale of specific embodiments and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. public content. Some components in the drawings can be adjusted in position according to actual needs without affecting the technical effect. In the following figures, similar parts are given the same reference numerals.

Sound absorbing devices have two typical spatial configurations. Specifically, one configuration is the channel sound absorber known in the prior art as shown in FIG. 1 . The channel sound absorber has an accommodating shell 1, and a gas inlet 2 and a gas outlet 3 are respectively provided at both ends of the accommodating shell 1. The gas will flow into the accommodating shell 1 from the gas inlet 2 in a unidirectional flow, and flow from the gas inlet 2 to the accommodating shell 1. The outlet 3 leaves the housing housing 1 . Inside the accommodating housing 1, a plurality of sound-absorbing materials 4 (in the form of sound-absorbing sheets in FIG. 1 ) extending parallel to the longitudinal axis (not shown) of the housing are arranged. There are spaces therebetween to form a plurality of longitudinal channels for the gas to flow through. When the vibrating air enters the sound absorbing material 4, it is gradually absorbed in the process of flowing downstream. At this time, most of the surface area of the sound absorbing material 4 (except for the fixed position with the accommodating shell) is exposed to the gas environment in the accommodating shell 1, and sound waves can pass through the exposed area of the sound absorbing material 4 Into the sound-absorbing material, so as to achieve the effect of noise reduction.

Further referring to FIG. 2 , a support frame 5 is generally arranged 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 that the sound-absorbing material 4 can be positioned and supported while being positioned and supported. The physical communication of ambient air with the sound absorbing material 4 is also not hindered. Specifically, at least one perforated area (area with a plurality of perforations) is formed through the outer peripheral wall of the support frame 5 to allow the ambient air to communicate with the sound absorbing material 4 and prevent fibers (when the sound absorbing material uses fibers material) is carried away by the airflow. As shown in FIG. 2 , perforated areas may be provided on the top wall and the bottom wall of the support frame 5 respectively. Of course, those skilled in the art should understand that the perforated area can be opened according to the relative positional relationship between the gas flow direction and the sound absorbing material, which is only schematically shown herein, not exhaustive. In general, the thickness of the outer peripheral wall of the support frame 5 is preferably 1 mm. The diameter of the perforations 6 is generally 2-5 mm, and the perforation rate is in the range of 20%-25%, where the perforation rate is defined as the ratio of the area of the perforations to the entire surface area of the support frame. The shape of the perforation 6 is not limited herein, it 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 part corresponding to the support frame 5 with the perforations 6 .

Figures 3 and 4 show schematic views of providing a hermetic membrane 7 for a structure similar to that according to Figure 2, wherein Figure 3b is a view of Figure 3a from the direction B, the shape of the perforations in Figure 3b is the same as the shape of the perforations in Figure 2b different. In view of the generally small thickness of the hermetic membrane 7, the above-mentioned support frame 5 is still preferably required to maintain the basic shape of the sound absorbing material 4. At the same time, studies have shown that the support frame 5 with a perforation rate greater than 23% has almost zero influence on the sound absorption performance of the sound absorption material 4 .

In order to be able to cover the remaining exposed areas of the sound absorbing material 4 (corresponding to the positions of the perforations), in the case shown in FIG. It needs 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 can be arranged between the support frame 5 and the sound absorbing material 4 as shown in FIG. 3 , or can be arranged outside the support frame 5 as shown in FIG. and installation difficulty. The arrangement of the full sealing film 7 inside the support frame can better protect the full sealing film 7 . The fully sealed membrane arrangement 7 on the outside of 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 passages within the accommodating housing 1 .

Whether the hermetic membrane is to be arranged on the outside or inside of the support frame, it is designed to be fixed to the support frame at several key structural locations, ie attached to the support frame through a number of discretely distributed fixing points. Additionally, it should be noted that the hermetically sealed film may not adhere to the support frame over the entire contact surface. If the hermetic membrane is fully glued to the support frame, the only part of the membrane that is also able to allow sound to pass through is the part corresponding to the perforations of the support frame, the stiffness of the diaphragm is sharp over small distances increase and will destroy mid to low frequency performance. A loose attachment with several fixing points is thus most preferred.

Figure 5 shows another typical spatial configuration of the sound absorbing device, ie in which the sound absorbing material 4 is to be suspended from a vertically extending support 7, such as a wall in a room, this configuration is particularly suitable for use in Indoor use. Specifically, 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 mounted 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 hermetic membrane 7 may be arranged between the support frame 5 and the sound absorbing material 4 . Of course, although not shown, the hermetic membrane 7 may also be arranged on the outer surface of the support frame 5 (ie the side away from the sound absorbing material).

For the sound absorbing device of this configuration, the sound waves can enter the sound absorbing material 4 in a manner perpendicular to the sound absorbing material (normal incidence) or oblique to the sound absorbing material (oblique incidence). If sound waves can strike the sound absorbing device from all angles, then this is called random incidence. The working principle of the fully-sealed film in this embodiment is the same as the above, but the thickness of the fully-sealed film used can be changed with the material of the fully-sealed film used and the configuration of the specific sound absorbing material. is not limited.

The traditional idea is that the indirect communication between the sound-absorbing material and the ambient air will prevent the sound wave from entering the sound-absorbing material, thereby affecting the sound absorption effect of the sound-absorbing material. This is true for most high frequency sounds (eg greater than 1 kHz), but not for low frequency sounds (eg below 200 Hz) and mid frequency sounds (200-1000 Hz). For low frequency and mid frequency sounds, with a reasonable choice of membrane thickness, the sound will cause the membrane to vibrate sufficiently and thereby pass through the membrane. Since the vibration of the membrane is caused by the interfering sound, it does not generate additional sound.

When sound waves impinge on 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 inertia added to the air movement, which is evaluated by the mass ratio. Specifically, the calculation method of the mass ratio m ₁ is:

m ₁ =ρ _m s/ρ ₀ h

where ρ _m is the material density of the membrane, s is the thickness of the membrane, ρ ₀ is the air density, and h is the typical air depth at which the sound waves travel, such as the height of the air passing space in a duct or the thickness of the sound absorbing material. When the membrane material adopts a 10-micron stainless steel membrane and the sound absorbing material adopts a typical size h=0.1m, the mass ratio is m ₁ =7850×10 ⁻⁵ /(1.225×0.1)=0.64. There is currently no clear limit for m1 to judge whether sound waves are mostly reflected back by the membrane or penetrate the membrane, but a value equal to or less than ₁ would be considered beneficial for sound transmission. Of course this also depends on the frequency of the sound waves. For low frequency sound waves, the membrane mass ratio helps to establish low frequency resonance and promotes sound absorption, then a high mass ratio such as 10 or even 100 can be used. However, when the value of m ₁ is large, it will obviously hinder the passage of high-frequency sound waves. Existing films would be too thick for such frequencies. Although both calculations and experiments have proved that reducing the thickness of the membrane will be more conducive to the passage of high-frequency sound waves, when the thickness of the material is less than a certain value, its processing technology is complicated, the cost is expensive, and it is relatively fragile. At present, material films with a thickness of 5 microns can be produced on the market, and as the processing technology matures, the cost will be reduced to a lower level, so it is expected to use material films of 5 microns or even 3 microns.

In order to avoid the use of expensive ultra-thin membranes, the present invention also provides another method that can solve the problem of high frequency sound passing through the fully sealed membrane, that is, to provide a pleated design to increase the contact area between the ambient air and the sound absorbing material.

Figures 6a, 6b and 7 show schematic views of the full sealing membrane 7 in a corrugated configuration. Wherein in Figures 6a and 6b, the hermetic membrane 7 is arranged outside the support frame 7, in this figure the sound absorbing material is configured in a cylindrical shape. In FIG. 7 , the hermetic membrane 7 is arranged between the support frame 5 and the sound absorbing material 4 . "Corrugated" is used herein only as a general term, which refers to the situation where the hermetic membrane has an increased surface area due to being bent. The corrugation may include various configurations, typical configurations may be, for example, a sinusoidal shape as shown in Figure 8a, a zigzag shape as shown in Figure 8b, and a butterfly shape as shown in Figure 8c.

In the structure shown in FIG. 7 , the airflow may travel perpendicular to the direction of extension of the pleats, the direction of which is indicated by arrow C. FIG. Use a smooth outer surface to support outside airflow and avoid high drag. Otherwise, the airflow may cause more resistance as it traverses the peaks and valleys of the pleats on the membrane. However, if the flow velocity of the gas is within a reasonable range, the folds of the membrane can also act to reduce drag while the folds of the membrane may act as an air bearing for the airflow passing therethrough. Of course, as shown in FIG. 9 , the airflow direction D can also be parallel to the extending direction of the pleats. The extension direction of the folds is not specifically limited in this paper, and the technical personnel can design according to the actual environmental conditions of the construction site.

The corrugated design of the hermetic membrane increases the overall surface area of the membrane, thereby compensating for the membrane's partial sound reflection of high frequency sounds. Adopting this design can also increase the aesthetics of the device.

Regarding the material of the hermetic membrane, in principle the membrane can be made of any material, where the main acoustical influence is its surface mass density ρ _m s. Damping properties of pure materials are usually negligible unless the material is specially designed. In this application, the function of the membrane is not sound absorption, and the damping of natural materials contributes little to sound absorption compared to sound absorbing materials. Thus, the choice of chemical composition of the membrane is not determined by its sound absorption properties, but by other factors such as fire resistance, corrosion resistance, aesthetics, product cost, and the like. If the sound-absorbing material does not require absolute air tightness, the membrane can even be made of tightly woven silk or other materials.

In addition, it should be noted that although the supporting frame is used in the exemplified embodiments of the present invention, it is not a necessary component. For a relatively hard sound-absorbing material, the fully-sealed film can be directly sleeved on the sound-absorbing material. External surface to cover all exposed areas of sound absorbing material exposed to the surrounding environment. When a support frame is employed, it is arranged at least on the outer surface of the exposed area of the sound absorbing material, thereby preventing deformation of the sound absorbing material. For example, for the sound-absorbing material in the middle position in FIG. 1 , the entire outer circumference of the sound-absorbing material may be exposed to the surrounding air, so the support frame can be sleeved on the entire outer circumference of the sound-absorbing material. However, for the structure shown in Figure 5, 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, there may be no need to arrange a support frame on this side.

In this context, "fully sealed membrane" refers to a continuous and densely extending cover without macroscopically visible pores and capable of separating the sound absorbing material (inner) from the surrounding air environment (outer), which enables Targets that prevent fibers or foams inside the sound absorbing material from entering the surrounding air environment, or prevent dust from the outside air from entering the sound absorbing material. But this does not mean that there is no internal and external communication at the air molecular scale, so there is no need for high air tightness requirements like food packaging. On the contrary, if several ventilation holes must be opened due to the requirement of balance of internal and external air pressure without affecting the above-mentioned function of separating the inside and outside, it should also be regarded as the fully sealed film of the invention.

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

In addition to solving the above problems of environmental air pollution and product performance deterioration, the use of the fully sealed film can also increase the selection of porous material varieties. For example, some materials that are so economical that they cannot be used without a seal become available with a sealed design. Others may be obtained directly from nature and contribute to sustainable development. In addition, the pleated design can be combined with artistic features to further enhance the aesthetics of the entire sound absorption device.

Claims

A sound absorbing structure is characterized by comprising:

a sound absorbing material (4) designed to absorb sound waves, the sound absorbing material having at least one exposed area exposed to the surrounding environment, through which the sound waves enter the sound absorbing material;

A fully-sealed membrane (7) designed to cover all exposed areas of the sound absorbing material (4), wherein the fully-sealed membrane extends in a continuous dense form.
The sound absorbing structure of claim 1, wherein the hermetic membrane is designed to extend in a corrugated configuration.
3. The sound absorbing structure according to claim 2, wherein the sound absorbing structure further comprises a support frame arranged at least on the outer surface of the exposed area of the sound absorbing material so as to support the sound absorbing material. For supporting, at least one perforated area is formed through the supporting frame.
The sound absorbing structure according to claim 3, wherein the fully sealing film is arranged between the supporting frame and the sound absorbing material to cover at least the perforated area of the supporting frame.
The sound absorbing structure according to claim 3, wherein the fully sealing film is arranged on the outer surface of the support frame to cover at least the perforated area of the support frame.
The sound absorbing structure according to claim 1, wherein the thickness of the fully sealed film is greater than or equal to 3 microns.
4. The sound absorbing structure of claim 3, wherein the hermetic membrane is attached to the support frame at discretely distributed fixed points.
A sound absorbing device, characterized in that it comprises the sound absorbing structure according to any one of the preceding claims, and further comprises a supporting medium in which the sound absorbing structure is built in or installed with the sound absorbing structure.
The sound absorbing device according to claim 8, wherein the supporting medium is designed as an accommodating shell, and the accommodating shell has a gas inlet and a gas outlet, and at least two sound absorbing structures are parallel to the The manner in which the longitudinal axis of the accommodating housing extends is held inside the accommodating housing.
9. The sound absorbing device of claim 8, wherein the support medium is a vertically extending support, and the sound absorbing material extends parallel to and is attached to the support.