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Poroelastic acoustical foam having enhanced sound-absorbing performance

Poroelastic acoustical foam having enhanced sound-absorbing performance description/claims

This application claims priority from Korean Patent Application No. 10-2007-0026059 filed on Mar. 16, 2007 and No. 10-2007-0106309 filed on October 22 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates to poroelastic acoustical foam, and, more particularly, to an optimal shape of poroelastic acoustical foam which can improve a sound-absorbing effect of low-frequency bands and middle-frequency bands.

2. Description of the Related Art

Poroelastic acoustical foams are designed to reduce noise and vibrations and are widely used in mechanical fields such as the automobile, airplane, and construction industries. Generally, poroelastic acoustical foams are porous materials having two phases: air and solid.

FIG. 1 is an enlarged view of a porous material. Referring to FIG. 1, a solid phase forms the frame of the porous material, and air fills in pores of the porous material. In this state, the two phases are physically coupled, thereby dynamically affecting each other. As a result, acoustic waves are dissipated as heat. The dissipation of thermal energy reduces the energy of sound waves transmitting through or reflected by the poroelastic acoustical foam, which, in turn, results in noise reduction.

Since the 1930s, many studies have been conducted on the development of poroelastic acoustical foams and the interpretation of their properties. In particular, in the 1950s, Maurice A. Biot conducted research on the propagation of elastic waves in porous materials, and thus laid the foundation for the analysis of the porous materials. Biot's study of porous materials not only directly and indirectly affected various fields including civil engineering, oil drilling engineering, soil engineering and marine engineering, but also was later applied in the analysis of the poroelastic acoustical foams.

Various studies on the sound-absorbing performance of poroelastic acoustical foams have also been conducted using Biot's theory, but most of the studies have relied on experiments. The studies have found that poroelastic acoustical foam shows better sound-absorbing performance when it has a wedge or trigonal pyramid shape. Wedge-shaped poroelastic acoustical foams are still widely used, mainly in anechoic chambers that require effective sound absorption.

FIGS. 2A and 2B are graphs illustrating sound absorption coefficients of a poroelastic acoustical foam having a simple rectangular shape and a poroelastic acoustical foam having a wedge shape, with respect to frequency. Referring to FIG. 2A, the lengths and widths of two shapes are the same, but the amounts of poroelastic acoustical foam used are different. In FIG. 2A, The amount of a porous material of the wedge shape is 65% of that of the rectangular shape. Referring to FIG. 2B illustrating sound absorption coefficients with respect to frequency, the rectangular poroelastic acoustical foam shows relatively better performance than the wedge-shaped poroelastic acoustical foam in some low-frequency bands. However, the wedge-shaped poroelastic acoustical foam shows far better performance than the square poroelastic acoustical foam in most frequency bands. That is, considering that high performance is displayed despite less amount of a porous material of wedge-shaped poroelastic acoustical foam, the performance of poroelastic acoustical foams can be greatly affected by the shape of the poroelastic acoustical foams when the material properties of the porous material are the same.

Nevertheless, most conventional studies have analyzed and experimented on poroelastic acoustical foams having conventional shapes, and no study has been conducted to obtain the optimal shape of poroelastic acoustical foams without initial shapes. That is, most of the conventional studies have attempted to identify properties of porous materials and interpret the performance of the poroelastic acoustical foams having given shapes in order to enhance the performance of the poroelastic acoustical foams. Further, the conventional studies have focused on enhancing the performance of poroelastic acoustical foams by repeating analyses and experiments based on their initial shapes, such as a wedge shape, and obtaining the optimal scales of the initial shapes.

Aspects of the present invention provide an apparatus and method for designing the optimal shape of poroelastic acoustical foam to obtain optimal performance under given conditions in a state where no initial shape is given.

However, aspects of the present invention are not restricted to the one set forth herein. The above and other aspects of the present invention will become more apparent to one of ordinary skill in the art to which the present invention pertains by referencing the detailed description of the present invention given below.

According to an aspect of the present invention, there is provided poroelastic acoustical foam which is made of a porous material, the poroelastic acoustical foam consisting of a wedge-shaped wedge unit where the cross section is reduced in one direction, and a bowl unit where formed at one end of the wedge unit where the cross section of the wedge unit is small. Further, the other end, where the cross section of the wedge unit is large, is separated from the wall, forming an air layer.

a wedge-shaped wedge unit where the cross section is reduced in one direction; and a bowl-shaped bowl unit where formed at one end of the wedge unit where the cross section of the wedge unit is small wherein the other end, where the cross section of the wedge unit is large, is separated from the wall, forming an air layer.

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