This application claims the benefit of Korean Patent Application No. 10-2016-0106386, filed on Aug. 22, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
One or more embodiments relate to sound absorbing and insulating structures and methods of designing the sound absorbing and insulating structures, and more particularly, to sound absorbing and insulating structures configured to decrease the velocity of sound in an acoustic medium for improving the performance of sound absorption and insulation in spite of limitations on shapes and thicknesses, and methods of designing the sound absorbing and insulating structures.
Referring to
According to the invention, however, partitions having relatively complex shapes are used to adjust the effective propagation distance of waves. Thus, a sound absorbing or insulating wall having a simple structure and a method of designing the wall are required.
Korean Patent No. 10-1626093
One or more embodiments include sound absorbing and insulating structures configured to be placed in a sound wave propagation path to reduce noises and methods of designing the sound absorbing and insulating structures.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.
According to one or more embodiments, a sound absorbing and insulating structure includes: a back panel arranged along a sound wave propagation path and having a flat-plate shape; a plurality of rigid partitions spaced apart from the back panel and arranged at intervals in parallel with each other so as to form resonant spaces; and a fixation frame fixing the rigid partitions to the back panel.
The rigid partitions may have different lengths from the fixation frame.
The rigid partitions may be sequentially arranged in a long-to-short order.
A space between the back panel and the rigid partitions may be filled with an acoustic absorbent.
According to one or more embodiments, a sound absorbing and insulating structure includes: a rear panel including a rigid body and a penetration hole; a front panel arranged at a distance from the rear panel, the front panel including a rigid body and a penetration hole communicating with the penetration hole of the rear panel; and a plurality of resonators arranged between the rear panel and the front panel around a space connecting the penetration holes of the rear panel and the front panel, wherein the resonators includes a plurality of rigid partitions arranged in parallel with each other to form resonant spaces.
The rigid partitions of the resonators may have different lengths.
The rigid partitions of the resonators may be sequentially arranged in a long-to-short order.
At least one of the rigid partitions of the resonators may have an L-shape.
A space among the rigid partitions of the resonators, the front panel, and the rear panel may be filled with an acoustic absorbent.
According to one or more embodiments, there is provided a method of designing a sound absorbing and insulating structure for reducing noises by arranging a sound absorbing and insulating structure in a path along which sound waves having an audible frequency range propagate and reducing a propagation velocity of the sound waves, the method including: measuring a frequency range of sound waves; determining a size of a resonator in which resonance occurs in the measured frequency range; determining sizes and intervals of a plurality of rigid partitions so as to form resonant spaces corresponding to the determined size of the resonator; and fabricating a sound absorbing and insulating structure by arranging the rigid partitions having the determined sizes on a rigid panel at the determined intervals.
The method may further include determining whether to design a sound absorbing and insulating structure including a continuous back panel in which no penetration hole is formed or a sound absorbing and insulating structure including a resonator placed between two layers of a panel in which a plurality of penetration holes are formed.
The method may further include selecting a flat-plate shape or an L-shape as a shape of the resonant spaces of the resonator.
These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:
Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
Embodiments relate to sound absorbing and insulating structures for reducing noise, and methods of designing the sound absorbing and insulating structures. Acoustic media mainly stated in the present disclosure are air, rigid bodies, and porous acoustic absorbents.
In acoustics, the term “rigid” or “rigid body” is used to indicate a material having a very high acoustic impedance such that sound waves may not propagate through the material, and in the present disclosure, a metal or acrylic plate may be used as a rigid partition. Porous acoustic absorbents are typical materials used for sound absorption and insulation, and owing to the intrinsic characteristics and microstructure of the porous acoustic absorbents, sound wave energy transferred to the porous acoustic absorbents is dissipated. In the present disclosure, a material such as a polyurethane or polyethylene foam may be used as a porous acoustic absorbent.
According to the present disclosure, sound absorption or insulation is accomplished by reducing sound wave energy reflected from or transmitted through a sound absorbing and insulating structure when sound waves are incident on the sound absorbing and insulating structure. The performance of sound absorption or insulation is defined using a coefficient by the amount of reflected or transmitted energy measured at each frequency in a given frequency band. In the case of sound absorption, an absorption coefficient may be mainly considered, and in the case of sound insulation, a transmission coefficient or transmission loss may be mainly considered. In the present disclosure, the performance of sound insulation is indicated by transmission loss.
When discussing sound absorption, a high absorption coefficient means that the performance of sound absorption is high because the amount of reflected energy is small. Similarly, when discussing sound insulation, high transmission loss means that the amount of transmitted energy is small and thus the performance of sound insulation is high.
Embodiments 1 and 2 relate to results of approaches to sound absorption, and embodiment 3 and a modification thereof relate to results of approaches to sound insulation. In the embodiments of the present disclosure, however, the performance of sound absorption and the performance of sound insulation overlap each other to some degree, and thus sound absorbing structures and sound insulating structures of the embodiments will be referred to as sound absorbing and insulating structures.
According to the embodiments, rigid structures are inserted/arranged so as to tailor the velocity of sound in air and a porous acoustic absorbent.
During the process of inventing, it was found that the frequency at which a sound absorbing and insulating material for reducing noise has a high degree of performance is mainly determined by a relationship between a characteristic length of the sound absorbing and insulating material and the wavelength of incident waves. Embodiments provides sound absorbing panels using porous acoustic absorbents (Embodiments 1 and 2), and sound insulating panels (Embodiment 3 and a modification thereof) each constituted by two panels (or layers) in which holes are periodically formed for ventilation and heat dissipation. The sound absorption characteristics of porous acoustic absorbents are significantly affected by the thickness of the porous acoustic absorbents, and thus an acoustic absorbent having a very large thickness is installed to guarantee sound absorption performance even in a low frequency band. In the case of a sound insulating panel in which ventilation holes are periodically formed, the distance (interval) between the ventilation holes have a large effect on the frequency of a sound applied to the panel, and thus it is difficult to reduce a target frequency while guaranteeing ventilation.
Therefore, in the present disclosure, a method of tailoring the velocity of sound is used as a method of guaranteeing the performance of sound absorption and insulation at a low frequency without varying limited thicknesses and spaces.
That is, in the present disclosure, the velocity of sound in an acoustic medium is tailored to improve the performance of sound absorption and insulation of a given structure. Before describing effects obtainable by tailoring the velocity of sound in a medium, physical phenomena related to two subjects of the present disclosure, that is, a sound absorption problem using a porous acoustic absorbent and a sound insulation problem using a double panel having holes will be first described. Techniques described below were obtained during the process of inventing and have not been known in the art except for techniques described with reference to
Referring to
Referring to
As illustrated in
Therefore, it was found that the sound absorption performance of an porous acoustic absorbent is significantly affected by a ¼ resonant mode occurring in proportion to the thickness of the porous acoustic absorbent or a characteristic length of a panel on a plane. Thus, if the thickness of an acoustic absorbent is increased, the frequency at which resonance occurs may be lowered.
In the case of a sound insulating panel including two layers, if the size of a unit structure of the sound insulating panel is increased or the size of holes is reduced while maintaining the size of the unit structure, the frequency at which resonance occurs may be further lowered.
In general, however, there is a limit to the thickness of an acoustic absorbent or the size of a unit structure or holes of a sound insulating panel when engineering designs are required, and thus a frequency tailoring method is required for obtaining a high degree of sound absorption and insulation performance without changing original specifications.
Embodiments provide methods of overcoming such limitations by tailoring the velocity of sound. For example, a method of designing a structure for obtaining a low wave propagation velocity is provided. If the velocity of sound waves is reduced, phenomena may occur such as a phenomenon in which waves travel a much longer distance than an originally given distance in a porous acoustic absorbent or an internal space of a double panel, and thus the performance of sound absorption and insulation may be improved at various frequencies by using such phenomena occurring at a low wave propagation velocity and inducing various resonant modes.
In sound absorbing and insulating structures according to embodiments, an acoustic waveguide structure having a plurality of resonators is formed to tailor the velocity of sound. In the following embodiments, rigid partitions are mainly used for simplicity in shape. However, other structures may be used.
Hereinafter, embodiments will be described with reference to the accompanying drawings.
Referring to
The unit cells include a plurality of rigid panels arranged in parallel with the rigid wall, and a frame fixing the rigid panels to the rigid wall.
A space among the rigid wall, the rigid panels, and the frame may be filled with a porous acoustic absorbent.
The sound absorbing and insulating structure 300 having the above-described configuration may be considered as having a porous sound absorbing layer and a sound velocity tailoring structure inserted in the porous sound absorbing layer. That is, unit cells (refer to an enlarged portion in
Referring to
The general porous acoustic absorbent illustrated in
The sound absorbing and insulating structure 300 of Embodiment 1 is modified to provide a sound absorbing and insulating structure 400 of Embodiment 2 having improved sound absorption performance in a wide frequency range. The sound absorbing and insulating structure 400 of Embodiment 2 will now be described.
When the sound absorbing and insulating structure 400 of Embodiment 2 illustrated in
As illustrated in
Owing to the low velocities of wave propagation and the occurrence of various resonant modes, the absorption coefficient α of the sound absorbing and insulating structure 400 is increased in a wide frequency range as illustrated in
A back panel 410 and a fixation frame 420 not described in the description of Embodiment 2 are substantially the same as those described in Embodiment 1. The position of an acoustic waveguide 440 is substantially the same as the position of the acoustic waveguide in Embodiment 1 but the width of the acoustic waveguide 440 is different from the width of the acoustic waveguide of Embodiment 1 because the rigid partitions 430 have different lengths.
Referring to
The front panel 520 and the rear panel 510 are plate-shaped members having areas and spaced apart from each other, and penetration holes are formed in the front panel 520 and the rear panel 510. The penetration holes are formed at substantially the same position in the front panel 520 and the rear panel 510 and have substantially the same size. Each of the front panel 520 and the rear panel 510 includes a rigid body.
The resonators 560 are arranged between the front panel 520 and the rear panel 510, and each of the resonators 560 includes plate-shaped members having ends contacting the front panel 520 and the rear panel 510. Four resonators 560 are provided in one unit structure.
Referring to
The rigid partitions 530 arranged in each of the resonators 560 may form an acoustic waveguide having a plurality of side resonant spaces 550. The side resonant spaces 550 may cause sound waves having a particular frequency to resonate, and thus the velocity of sound may be tailored in the resonators 560. Like the sound absorbing and insulating structure 300 or 400 of Embodiment 1 or 2, various structures may be designed by adjusting the lengths and number of the rigid partitions 530 based on the unit structure, and a space among the front panel 520, the rear panel 510, and the rigid partitions 530 may be filled with a material such as an acoustic absorbent instead of air.
Meanwhile, as shown in
As illustrated in
Alternatively, two of the four resonators 560 illustrated in
The test was performed under the following conditions: a space among the front panel 520, the rear panel 510 or 610, and the rigid partitions 530 or 630 was filled with air; the length of one side of a unit structure was 50 mm; the length of one side of a central penetration hole having a square shape was 15 mm; and the thickness of the rigid partitions 530 or 630 was 2 mm.
Referring to
Referring to
Referring to
As illustrated in
In the case of a unit structure not having the resonators 560 or 660, the above-described ¼ wavelength resonant mode does not occur until the frequency of waves reaches about 3000 Hz, that is, occurs when the frequency of waves is higher than about 3000 Hz (refer to narrow lines in
However, in the case of the sound absorbing and insulating structures 500 and 600 of Embodiment 3 and the modification of Embodiment 3, the resonant mode occurs in a relatively low frequency range because the velocity of wave propagation is low in the sound absorbing and insulating structures 500 and 600 as indicated by thick lines in
Therefore, the performance of sound absorption and insulation may be improved according to the embodiments, and a frequency band in which sound absorption and insulation are guaranteed may be effectively adjusted by using the method of tailoring the velocity of sound. For example, it is possible to achieve improvements in the performance of sound absorption and insulation in a frequency band of about 2000 Hz or lower which are difficult to achieve using an existing sound absorbing and insulating structure including a two-layer sound insulating panel and penetration holes formed in the two-layer sound insulating panel.
An embodiment provides a method of designing a sound absorbing and insulating structure based on the above-described embodiments as follows.
The method of designing a sound absorbing and insulating structure according to the embodiment may include measuring the frequency range of noises mainly occurring in a place in which a sound absorbing and insulating structure will be installed, and designing resonators 560 or 660 or the sizes of resonant spaces 350, 450, 550, or 650. Basically, according to the method of designing a sound absorbing and insulating structure of the embodiment, a sound absorbing and insulating structure is arranged in a propagation path of sound waves having an audible frequency range, and the velocity of sound wave propagation is reduced to decrease noises.
According to the embodiment, the method of designing a sound absorbing and insulating structure may include: measuring the frequency range of noises occurring in a place in which the sound absorbing and insulating structure will be arranged; determining the size of a resonator 560 or 660 generating resonance within the measured frequency range; determining the sizes and intervals of a plurality of rigid partitions 330, 430, 530, or 630 to form resonant spaces 350, 450, 550, or 650 corresponding to the determined size of the resonator 560 or 660; and fabricating the sound absorbing and insulating structure by arranging the rigid partitions 330, 430, 530, or 630 having the determined sizes on a rigid panel at the determined intervals.
When the sizes of the resonant spaces 350, 450, 550, or 650 are determined, the thicknesses of the rigid partitions 330, 430, 530, or 630 and the height and width of the sound absorbing and insulating structure may be considered in addition to the lengths and intervals of the rigid partitions 330, 430, 530, or 630. In addition, the width (d) of a unit cell may be considered. If the width (d) increases, sound waves may be reflected or transmitted in various directions, and thus the width (d) may be maintained to be within or smaller than a certain range. For this, the width (d) of the unit cell may be set to be less than a wavelength λmin corresponding to a maximum frequency fmax in a frequency band (fa, fmin≦fa≦fmax) of sound waves Pi to be absorbed.
In addition, the method of designing a sound absorbing and insulating structure may further include determining whether to design a sound absorbing and insulating structure 300 or 400 including a continuous back panel 310 in which no penetration hole is formed or a sound absorbing and insulating structure 500 or 600 including a resonator 560 or 660 placed between two panel layers in which a plurality of penetration holes are formed.
In addition, the method of designing a sound absorbing and insulating structure may further include: determining whether to fill a space corresponding to an acoustic waveguide 340 or 440 or the resonant spaces 350 or 450 with an acoustic absorbent; and determining the type of the acoustic absorbent. If a porous material is determined as the acoustic absorbent, at least one porous material selected from the group consisting of a polyurethane foam, a polyester foam, a melamine foam, and the like may be used as the acoustic absorbent.
In addition, according to the embodiment, the method of designing a sound absorbing and insulating structure may further include selecting the shape of the resonant spaces 550 or 650 of the resonator 560 or 660 from one of a flat-plate shape and an L-shape. When compared to the case of considering resonant spaces having one shape, the performance of the sound absorbing and insulating structure may be improved in a relatively wide range.
As described above, the method of the embodiment may make it possible to easily design a sound absorbing and insulating structure having improved performance in a place in which the sound absorbing and insulating structure will be placed.
As described above, according to the one or more of the above embodiments, the velocity of sound may be tailored to improve the sound adsorption or insulation performance of the sound absorbing and insulating structures.
It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.
While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims.
Number | Date | Country | Kind |
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10-2016-0106386 | Aug 2016 | KR | national |