KR101777467B1 - Broadband acoustic metamaterial unit element and structure using the same - Google Patents

Abstract

The present invention relates to a container comprising a liquid and a saturated vapor mixture of said liquid; A liquid absorbing portion formed inside the container; And a diaphragm for sealing the container, and a structure using the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a broadband acoustic meta-

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a broadband sound meta-material unit element and a structure using the same.

Acoustic metamaterial is an artificial structure with efficiency density and effective volumetric elasticity over the range of density and effective volume elastic modulus that natural fluid can have. Generally, acoustic metamaterial unit elements are arrayed .

Acoustic transparent cloak, acoustic super lens, sound absorbing plate, sound insulating plate, muffler, etc. have been developed as it becomes possible to produce an acoustic medium having properties that can not be obtained by substances existing in nature using such acoustic meta material. Particularly, when a meta material having an effective volume elastic modulus smaller than that of air is used, it becomes possible to drastically improve performance as a scratch plate, sound insulating plate and muffler.

The conventional acoustic metamaterial structure for making the ultimate effective bulk modulus includes a structure having a Helmholtz resonator as a unit element and a structure having a side hole as a unit element. However, these two structures have a problem that the frequency range at which the bulk modulus of elasticity is realized is very narrow, so that it can not be used for a wide band application.

The present invention relates to a container comprising a liquid and a saturated vapor mixture of said liquid; A liquid absorbing portion formed inside the container; And a diaphragm for sealing the container, and the like.

The technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a container comprising a liquid and a saturated vapor mixture of said liquid; A liquid absorbing portion formed inside the container; And a diaphragm for sealing the container.

The volume volumetric elastic modulus within the container may be 10,000 Pa or less.

The boiling point of the liquid may range from 30 ° C to 200 ° C.

And a temperature holding portion formed inside the container and holding the inside of the container at the boiling point temperature of the liquid.

Wherein the thermostatic holding unit comprises: a heating unit for heating the inside of the container; And a feedback signal unit operating according to the movement of the diaphragm.

And an anti-fog coating layer formed on the inner surface of the diaphragm.

And a heat insulating layer formed outside or inside the diaphragm.

The heat insulating layer may be formed of a plurality of layers spaced apart from each other by a predetermined distance, and may further include an auxiliary heating portion formed between the plurality of layers.

In one embodiment of the present invention, there is provided a broadband acoustic metamaterial structure disposed in a one-dimensional, two-dimensional, or three-dimensional space and including a plurality of the wideband sound meta-material unit elements.

The liquid contained in the container of the broadband sound meta-material unit element according to the present invention and the saturated vapor mixture of the liquid are formed at the boiling point of the liquid and maintain a constant pressure even if the volume changes, To a few hundred hertz, i.e., in a wide frequency band, for example, 10,000 Pa or less.

Therefore, the broadband sound meta-material unit element and the structure using the same according to the present invention can dramatically improve the performance as a sound-absorbing plate, a sound-insulating plate, and a muffler.

Figure 1 shows a pressure-volume diagram for a saturated vapor mixture of liquid and liquid at isothermal conditions.
FIG. 2 illustrates a broadband sound meta-material unit element according to a first embodiment of the present invention.
FIG. 3 illustrates the shape of a diaphragm in a broadband sound meta-material unit element according to a first embodiment of the present invention.
FIG. 4 illustrates a broadband sound meta-material unit according to a second embodiment of the present invention.
FIG. 5 illustrates a broadband sound meta-material unit element according to a third embodiment of the present invention.
FIG. 6 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a one-dimensional space.
FIG. 7 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a two-dimensional space.
FIG. 8 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a three-dimensional space.

The present inventors confirmed that the saturated vapor mixture of the liquid and the liquid maintains a constant pressure even when the volume changes, and when the container is incorporated into the container, it is confirmed that the inside of the container has a very small effective volume elastic modulus in a wide band, The broadband acoustic metamaterial unit element was completed.

When the acoustic meta-material is constituted by using the wide-band acoustic meta-material unit elements according to the present invention, the acoustic meta-material unit element may be mixed with other types of acoustic meta-material unit elements or may be used without mixing. By arranging only the unit elements of the present invention in space without mixing, the acoustic volumetric elastic modulus can be made very small and the efficiency density can be produced as the efficiency density of the fluid filling the space remains the same. In some cases, a mixed structure is formed by introducing other types of unit elements. The most representative purpose is to make the effective volume elastic modulus very small and at the same time to change the efficiency density further. As a unit element for changing the efficiency density introduced at this time, a kind based on a tensioned film and a type using a double resonator have been developed. When an array is formed such that one of the acoustic meta-material unit elements for changing the efficiency density is alternately arranged with the volume modulus unit elements of the present invention, for example, the efficiency bulk modulus is small, and at the same time, It becomes possible to realize a large acoustic meta material.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

Hereinafter, the present invention will be described in detail.

The present invention relates to a container comprising a liquid and a saturated vapor mixture of said liquid; A liquid absorbing portion formed inside the container; And a diaphragm for sealing the container.

The present invention also provides a broadband acoustic metamaterial structure disposed in a one-dimensional, two-dimensional, or three-dimensional space and including a plurality of the wideband sound meta-material unit elements.

Here, in the broadband acoustic metamaterial structure, the one wideband sound meta-material unit element and the space including the one wide-band sound meta material unit element are called a unit cell. The size of the unit cell or the interval between unit cells is very small . The size of the unit cell may be less than or equal to 1/2 of the wavelength of the sound wave in the structure

Figure 1 shows a pressure-volume diagram for a saturated vapor mixture of liquid and liquid at isothermal conditions.

As shown in FIG. 1, the liquid can form a saturated vapor mixture (dotted line inner region) of the liquid and the liquid at the boiling point temperature of the liquid causing the phase change to gas, wherein the mixture undergoes constant pressure The slope of the curve on the pressure-volume diagram is zero, and finally the effective volumetric elastic modulus of the saturated vapor mixture of liquid and liquid is 0 Pa.

As used herein, the term " bulk modulus " refers to a value indicating the extent to which an object is subject to isotropic compressive stress and not to be compressed, and the unit is equal to the pressure unit :

.Bulk modulus = - V ·

.

)는 음의 값을 가지므로 효율체적탄성률은 양의 값을 갖지만, 본 발명을 통하여, 효율체적탄성률이 0 Pa이 되는 액체 및 상기 액체의 포화증기 혼합물을 찾아내고, 이를 이용한 것을 특징으로 한다. In almost all cases of thermodynamic systems, the slope of the curve on the pressure-volume diagram

) Has a negative value, the effective volumetric elastic modulus has a positive value, but through the present invention, a liquid having an effective volumetric elastic modulus of 0 Pa and a saturated vapor mixture of the liquid are found and used.

FIG. 2 illustrates a broadband sound meta-material unit element according to a first embodiment of the present invention.

As shown in FIG. 2, the broadband sound meta-material unit element 100 according to the first embodiment of the present invention comprises a container 10 comprising a liquid and a saturated vapor mixture of the liquid; A liquid absorbing portion 20 formed inside the container; And a diaphragm 30 for sealing the container.

Specifically, the broadband sound meta-material unit element 100 according to the present invention comprises a vessel 10, which comprises a liquid and a saturated vapor mixture of the liquid. At this time, outside air should be excluded inside the container (10). At this time, the saturated vapor mixture of the liquid and the liquid is formed at the boiling point of the liquid, and the inside of the vessel 10 should be able to maintain the approximate boiling point temperature.

The liquid has a relatively low boiling point, and the boiling point of the liquid may be between 30 ° C and 200 ° C. As the liquid, ethanol, methanol, ethanol / methanol mixture, gasoline, acetone, water and the like can be used.

The vessel 10 includes a liquid and a saturated vapor mixture of the liquid, wherein the interior of the vessel 10 may have a minimal effective bulk modulus at a broadband.

Specifically, the volume volumetric elastic modulus of the inside of the container 10 is preferably 10,000 Pa or less, more preferably 1,000 Pa or less, most preferably substantially 0 Pa, which corresponds to 1/10 of the volume elastic modulus of air, But is not limited thereto. The inside of the container 10 preferably maintains the boiling point temperature of the liquid so that the effective volumetric elastic modulus becomes 0 Pa.

The broadband sound meta-material unit element 100 according to the present invention further includes a liquid absorbing portion 20 and the liquid absorbing portion 20 is formed inside the container 10, And absorbs the liquid contained therein, which determines the performance of the broadband sound meta-material unit element 100. The liquid absorbing portion 20 may have a large surface area so as to maximize the surface of the liquid absorbed by the saturated vapor of the liquid. The liquid absorbing portion 20 may be formed of a porous material.

That is, since the liquid absorbing portion 20 is preferably capable of absorbing liquid and has a large surface area, a porous nonwoven fabric or a sponge may be suitable.

For example, in order to widen the surface area of the liquid absorbing portion 20, a porous nonwoven fabric or sponge capable of absorbing liquid is formed into a wavy form, and then a plurality of piles are stacked vertically so that the bent portions are in contact with each other. It is possible to maximize the surface in contact with the saturated vapor of the liquid.

When the temperature of the vessel 10 is maintained at a boiling point, the diaphragm 30 becomes flat when the pressure of the sound wave is not applied from the outside. When there is a sound wave, the pressure of the sound wave oscillates in a sine wave shape with time.

When the pressure of the sound wave is positive, the diaphragm 30 is inflated into the container 10 to form a curved surface, thereby reducing the volume occupied by the saturated vapor inside the container. Accordingly, condensation occurs on the surface of the liquid absorbing portion 20 to generate condensation heat. The temperature of the surface of the liquid absorbing portion 20 becomes slightly higher than the ambient temperature, that is, the boiling point temperature of the liquid. When the temperature of the surface where the liquid and the saturated vapor meet is higher than the boiling point temperature of the liquid, the pressure inside the vessel 10 becomes slightly higher than the atmospheric pressure, It grows big. The larger the surface area at which the saturated vapor and the liquid meet, the smaller the temperature rise of the surface where the liquid and the saturated vapor meet in accordance with the same volume change. As a result, the effective volume elastic modulus within the vessel 10 becomes closer to 0 Pa . Therefore, it is preferable to increase the area of the surface where the liquid and the saturated vapor meet, which is achieved by using the liquid absorbing portion 20 having a large surface area.

On the other hand, when the pressure of the sound wave is negative, the diaphragm 30 expands out of the vessel 10 to form a curved surface, which increases the volume occupied by saturated steam in the vessel. Accordingly, evaporation occurs on the surface of the liquid absorbing portion 20, and the temperature of the surface of the liquid absorbing portion 20 is lowered by a slight difference from the ambient temperature, that is, the boiling point temperature of the liquid, due to the heat of vaporization. When the temperature of the surface where the liquid and the saturated vapor meet is lower than the boiling point temperature of the liquid, the pressure inside the vessel 10 becomes slightly lower than the atmospheric pressure, Pa. The larger the surface area at which the saturated vapor and the liquid meet, the smaller the temperature drop of the surface where the liquid and the saturated vapor meet in accordance with the same volume change. As a result, the effective volume modulus of elasticity in the vessel 10 becomes closer to 0 Pa . Therefore, it is preferable to increase the area of the surface where the liquid and the saturated vapor meet, which is achieved by using the liquid absorbing portion 20 having a large surface area.

As described above, as the surface area of the liquid absorbing portion 20 is increased, the temperature change of the surface of the liquid absorbing portion 20 is reduced. When the surface area of the liquid absorbing portion 20 is infinitely large, There is no change in temperature of the surface of the container 10 and thus a minute pressure change. Therefore, the effective volume modulus of elasticity in the container 10 becomes 0 Pa.

The broadband acoustical meta-material unit element 100 according to the present invention also includes a diaphragm 30 that seals the vessel 10 to prevent leakage of the saturated vapor, Materials can be used.

The general wall may be a means for keeping the pressure inside and outside different, but the diaphragm 30 should keep the pressure inside and outside the same. The diaphragm 30 may be made of various thin films such as cellophane and lap, and a corrugated metal plate may be used.

FIG. 3 illustrates a diaphragm in a broadband sound meta-material unit element according to a first embodiment of the present invention. In FIG. 3, a corrugated metal plate is used to maintain the pressure inside and outside the diaphragm 30 The corrugated metal sheet may have a corrugated shape in a plurality of concentric circles.

Since the temperature of the outside is lower than the internal temperature of the vessel 10, saturated steam condenses on the inner surface of the diaphragm 30, and the condensed liquid droplets increase the mass of the diaphragm 30, The anti-fog coating layer (not shown) formed on the inner surface of the diaphragm 30 may be further included to improve the anti-fog coating.

FIG. 4 illustrates a broadband sound meta-material unit according to a second embodiment of the present invention.

As shown in FIG. 4, the broadband sound meta-material unit element according to the second embodiment of the present invention comprises a container 10 comprising a saturated vapor mixture of a liquid and the liquid, as described above; A liquid absorbing portion 20 formed inside the container; And a diaphragm (30) for sealing the container, and a constant temperature holding part (40) formed inside the container and holding the inside of the container at the boiling point temperature of the liquid. At this time, the constant temperature holding part (40) includes a heating part (41) for heating the inside of the container; And a feedback signal unit 42 that operates in accordance with the movement of the diaphragm 30. [

Specifically, the container 10, the liquid absorbing portion 20, and the diaphragm 30 are as described above.

As an example of the feedback signal unit 42, a conductor formed on one side of the inner surface or the outer surface of the diaphragm and a contact formed with a small clearance therebetween may be included. Contact and non-contact of the conductor and the contact are determined according to the movement of the diaphragm. At this time, it is preferable that copper tape or copper wire is used as the conductor, but it is not limited thereto.

When the diaphragm 30 expands into the inside, the heating unit 41 generates heat by contacting the conductor and the contact of the feedback signal unit 42. When the diaphragm 30 expands to the outside The heating section 41 does not generate heat and naturally cools it by making the conductor and the contact of the feedback signal section 42 contactless. By repeating this process, the inside of the container 10 can be maintained at the boiling point temperature of the liquid.

Meanwhile, by finishing the outside of the broadband sound meta-material unit element 100 according to the present invention with an insulating material, the internal temperature can be uniformly maintained, and the capacity of the heating unit 41 of the constant temperature holding unit 400 can be reduced .

FIG. 5 illustrates a broadband sound meta-material unit element according to a third embodiment of the present invention.

As shown in FIG. 5, the broadband sonic meta-material unit element according to the third embodiment of the present invention comprises a vessel 10 comprising a liquid and a saturated vapor mixture of the liquid, as described above; A liquid absorbing portion 20 formed inside the container; And a diaphragm (30) for sealing the container, wherein a heat insulating layer (50) formed outside or inside the diaphragm may be further formed, wherein the heat insulating layer is formed of a plurality of layers spaced at a predetermined interval, And an auxiliary heating portion 60 formed between the layers.

Specifically, the container 10, the liquid absorbing portion 20, and the diaphragm 30 are as described above.

At this time, the heat insulating layer 50 may be formed outside or inside the diaphragm 30 and may include a plurality of layers 51 and 52 spaced apart from each other by a predetermined distance, Films of flexible material can be used. Between the plurality of layers 51 and 52 can be filled with air to enhance heat insulation, thereby preventing the liquid from condensing on the inner surface of the diaphragm 30.

The auxiliary heating portion 60 may be formed between the plurality of layers 51 and 52 when the heat insulating layer 50 includes a plurality of layers 51 and 52 spaced apart from each other by a predetermined distance. This assist can keep the temperature of the diaphragm 30, which is in contact with the saturated vapor, higher than the boiling point of the liquid due to the formation of the heating portion 50, thereby preventing the liquid from condensing on the inner surface of the diaphragm 30 . The auxiliary heating part 60 may be formed in the form of a porous plate, and the air gap formed in the auxiliary heating part in the form of a porous plate can freely pass the air so that a pressure difference does not occur.

For example, when a plurality of layers 51 and 52 spaced apart from each other are formed outside the diaphragm 30, and an auxiliary heating portion 60 is formed therebetween, the upper insulating layer 51 is divided into the auxiliary heating portion 60 And the lower insulating layer 52 may serve to insulate the auxiliary heating portion 60 with the saturated steam therein so that the inside of the heating portion 60 is saturated with the inside of the heating portion 60. [ Steam may serve to reduce the amount of heat supplied from the auxiliary heating portion 60. At this time, the upper insulating layer 51 and the lower insulating layer 52 may be formed of two layers, respectively.

At this time, when too much heat is supplied from the auxiliary heating unit 60 to the inside, there is a problem in operation of the heat holding unit 40, Is preferably maintained at a level at which the temperature of the liquid remains somewhat higher than the boiling point of the liquid, but is not limited thereto.

FIG. 6 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a one-dimensional space.

As shown in FIG. 6, a structure in which a plurality of wideband sound meta-material unit elements are arranged in a one-dimensional space includes a duct 200; And a plurality of wideband sound meta-material unit elements 100 formed in the duct 200. [ For example, air may be filled in the upper part of the duct 200, and a plurality of broadband sound meta-material unit elements 100 may be installed in the lower part of the duct 200. For example, May be arranged in a line.

FIG. 7 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a two-dimensional space.

As shown in FIG. 7, a structure in which a plurality of wideband sound meta-material unit elements are arranged in a two-dimensional space includes two plates (upper plate and lower plate) 300 spaced at a predetermined interval; And a plurality of wideband sound meta-material unit elements 100 formed between the two plates 300. [ For example, air may be filled in the upper part between the two plates 300, and a plurality of broadband acoustic meta-material units (not shown) may be filled in the lower part. The elements 100 may be arranged and filled in a square array.

FIG. 8 shows a structure in which a plurality of wideband sound meta-material unit elements are arranged in a three-dimensional space.

As shown in FIG. 8, a structure in which a plurality of wideband sound meta-material unit elements are arranged in a three-dimensional space includes a three-dimensional space; And a plurality of wideband sound meta-material unit elements 100 formed in the three-dimensional space. The three-dimensional space corresponds to a passage through which sound can pass. For example, air can be filled in half of the three-dimensional space, and a plurality of broadband sound meta-material unit elements 100) may be arranged in a cube array and filled. In this case, the effective bulk modulus of elasticity of the structure may be about twice that of the wideband sound meta-material unit element 100.

As described above, the liquid contained in the container of the broadband sound meta-material unit element according to the present invention and the saturated vapor mixture of the liquid are formed at the boiling point temperature of the liquid and maintain a constant pressure even when the volume changes, The inside of the container has a very low effective bulk modulus of elasticity ranging from several hertz to several hundreds of hertz, that is, broad band, for example, 10,000 Pa or less.

Therefore, the broadband sound meta-material unit element and the structure using the same according to the present invention can dramatically improve the performance as a sound-absorbing plate, a sound-insulating plate, and a muffler.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (9)

A container comprising a liquid and a saturated vapor mixture of said liquid;
A liquid absorbing portion formed inside the container;
A diaphragm for sealing the vessel; And
And a temperature holding portion formed inside the container and holding the inside of the container at the boiling point temperature of the liquid,
Wherein the thermostatic holding unit comprises: a heating unit for heating the inside of the container; And a feedback signal portion that operates in accordance with the movement of the diaphragm
Broadband sound meta - material unit element.
The method according to claim 1,
The volume volumetric elastic modulus of the inside of the container is preferably 10,000 Pa or less
Broadband sound meta - material unit element.
The method according to claim 1,
The boiling point temperature of the liquid is from 30 [deg.] C to 200 [
Broadband sound meta - material unit element.
delete delete The method according to claim 1,
Further comprising an anti-fog coating layer formed on the inner surface of the diaphragm
Broadband sound meta - material unit element.
The method according to claim 1,
And a heat insulating layer formed outside or inside the diaphragm
Broadband sound meta - material unit element.
8. The method of claim 7,
Wherein the heat insulating layer is formed of a plurality of layers spaced apart from each other by a predetermined distance and further includes an auxiliary heating portion formed between the plurality of layers
Broadband sound meta - material unit element.
Comprising a plurality of broadband sound meta-material unit elements arranged in a one-dimensional, two-dimensional or three-dimensional space and comprising a plurality of broadband sound meta-material unit elements according to any one of claims 1 to 3,
Broadband acoustic metamaterial structure.

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