Patent Description:
In Patent Literature <NUM>, there is a description of a soundproof material including: a first sound-absorbing material arranged to face a sound source; a first soft sound-insulating layer, which is laminated on a surface of the first sound-absorbing material opposite to the sound source, and has an air permeability measured in accordance with JIS L1018 of <NUM> cc/cm<NUM>·sec or less; a second sound-absorbing material laminated on the first soft sound-insulating layer; and a second soft sound-insulating layer, which is laminated on the second sound-absorbing material, and has an air permeability measured in accordance with JIS L1018 of <NUM> cc/cm<NUM>·sec or less and a Young's modulus measured in accordance with JIS K7127 five or more times as high as that of the first soft sound-insulating layer, wherein at least the second soft sound-insulating layer is partially or entirely bonded to the second sound-absorbing material.

Patent Literature <NUM> discloses a lightweight, thin soundproof cover that suppresses noise in the high-frequency region exceeding <NUM> and with which it is possible to effectively suppress noise in the <NUM>-<NUM> low-frequency region. The soundproof cover is characterized by comprising a laminated member in which are laminated one or more low-density elastic porous layers having a density of <NUM>-<NUM>/cm3 [i.e. <NUM>-<NUM>/m3], and one or more high-density elastic porous layers having a density of <NUM>-<NUM>/cm3 [i.e. <NUM>-<NUM>/m3] and being coated with a low-air-permeability sheet having air permeability of <NUM> cc/cm2·sec or less.

In Non-Patent Literature <NUM>, there is a description of analysis of sensitivity of Biot parameters to acoustic characteristics. In Non-Patent Literature <NUM>, there are descriptions of development of a lightweight soundproof cover using the Biot theory (theory of vibration propagation in elastic porous materials), and an example application thereof to a transmission.

However, although, as described in Non-Patent Literatures <NUM> and <NUM>, analysis based on the Biot theory has been recognized as useful for evaluating the soundproof characteristics of a soundproof member, trial and error has still been required as to specifically what configuration a novel soundproof member having desired soundproof characteristics should have.

The present invention has been made in view of the above-mentioned problem, and one of the objects of the present invention is to provide a soundproof member having excellent soundproof characteristics.

In order to solve the above-mentioned problem, according to the present invention, there is provided a soundproof member according to claim <NUM>, including: a first elastic porous body layer; a first film layer; a second elastic porous body layer; and a second film layer, the layers being arranged in the stated order from a sound source side, wherein the first elastic porous body layer and the second elastic porous body layer each have: a thickness of <NUM> or more and <NUM> or less; a bulk density of <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less; and a Young's modulus of <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less, and wherein a total (L1/Λ1+L2/Λ2) of a ratio (L1/Λ1) of the thickness L1 (mm) of the first elastic porous body layer to a viscous characteristic length Λ1 (µm) thereof and a ratio (L2/Λ2) of the thickness L2 (mm) of the second elastic porous body layer to a viscous characteristic length A2 (µm) thereof is <NUM> or more, and wherein a ratio of the bulk density of the second elastic porous body layer to the bulk density of the first elastic porous body layer is <NUM> or more and <NUM> or less. According to the present invention, a soundproof member having excellent soundproof characteristics is provided.

In the soundproof member, the first elastic porous body layer and the second elastic porous body layer may each be a fibrous body layer. In the soundproof member, the first film layer and the second film layer may each be an elastomer film layer.

According to the present invention, a soundproof member having excellent soundproof characteristics is provided.

Now, one embodiment of the present invention will be described. The present invention is not limited to this embodiment.

A main configuration in a soundproof member <NUM> according to this embodiment is schematically illustrated in <FIG>. The soundproof member <NUM> includes: a first elastic porous body layer <NUM>; a first film layer <NUM>; a second elastic porous body layer <NUM>; and a second film layer <NUM>, the layers being arranged in the stated order from a sound source S side, wherein the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> each have: a thickness of <NUM> or more and <NUM> or less; a bulk density of <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less; and a Young's modulus of <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less, and wherein a total (hereinafter referred to as "specific parameter (L1/Λ1+L2/Λ2)") of a ratio (L1/A1) of the thickness L1 (mm) of the first elastic porous body layer <NUM> to a viscous characteristic length Λ1 (µm) thereof and a ratio (L2/A2) of the thickness L2 (mm) of the second elastic porous body layer <NUM> to a viscous characteristic length A2 (µm) thereof is <NUM> or more.

That is, the inventors of the present invention have made extensive investigations in the development of a soundproof member having excellent soundproof characteristics, and as a result, have independently found that, surprisingly, a soundproof member falling within a predetermined range of the above-mentioned specific parameter (L1/Λ1+L2/Λ2) is excellent not only in transmission loss, but also in insertion loss. Thus, the present invention has been completed.

As illustrated in <FIG>, in the soundproof member <NUM>, the first elastic porous body layer <NUM> is arranged at the closest position to the sound source S among the above-mentioned four layers <NUM>, <NUM>, <NUM>, and <NUM>, the first film layer <NUM> is arranged on the opposite side of the first elastic porous body layer <NUM> to the sound source S, the second elastic porous body layer <NUM> is arranged on the opposite side of the first film layer <NUM> to the sound source S, and the second film layer <NUM> is arranged on the opposite side of the second elastic porous body layer <NUM> to the sound source S.

The sound source S is not particularly limited as long as the sound source S emits a sound serving as the target of soundproofing. The frequency of the noise to be emitted by the sound source S is not particularly limited, but may fall within, for example, the range of from <NUM> or more to <NUM> or less, or the range of from <NUM> or more to <NUM>,<NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> are each formed of an elastic porous body. The elastic porous body is not particularly limited as long as the elastic porous body is a porous material having elasticity and showing a sound-absorbing property, but may be, for example, a fibrous body or a foam-molded body. That is, the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each be independently formed of a fibrous body or a foam-molded body.

When the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> are each a fibrous body layer formed of a fibrous body, the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each be formed of a fibrous body of an organic fiber, or may each be formed of a fibrous body of an inorganic fiber, but are each preferably an organic fibrous body layer formed of a fibrous body of an organic fiber.

The organic fiber is, for example, one or more selected from the group consisting of: a resin fiber; cotton; wool; excelsior; a kudzu fiber; and a kenaf fiber. The organic fiber is preferably a resin fiber, particularly preferably a thermoplastic resin fiber.

The resin fiber is, for example, one or more selected from the group consisting of: polyester fibers, such as a polyethylene terephthalate (PET) fiber; polyamide fibers, such as a nylon fiber; polyolefin fibers, such as a polyethylene fiber and a polypropylene fiber; and acrylic fibers.

The inorganic fiber is, for example, one or more selected from the group consisting of: glass wool; rock wool; a silica fiber; an alumina fiber; a silica-alumina fiber; an aramid fiber; a rock wool long fiber; and a whisker (e.g., SiC).

The fibrous body is preferably a product (so-called resin felt) obtained by processing an organic fiber and/or an inorganic fiber with a resin (e.g., a thermosetting resin) into felt. Specifically, the fibrous body is preferably formed of partially joined organic fibers. In this case, the fibrous body may be an organic fibrous body containing first organic fibers and second organic fibers having a lower melting point than the first organic fibers, the first organic fibers being partially joined by the second organic fibers.

The fibrous body may be formed of inorganic fibers joined by a binder. In this case, for example, a resin, such as a phenol resin, may be used as the binder. The fibrous body may be a nonwoven fabric. The fibrous body may be a needle-punched fibrous body.

The foam-molded body is not particularly limited as long as the foam-molded body has open cells. The foam-molded body is produced by, for example, foaming a resin so as to form open cells. The foam-molded body may be produced by foaming a resin and then performing crushing processing or the like to impart openness to cells formed by the foaming.

The resin for forming the foam-molded body is not particularly limited as long as the resin can be foam-molded, and may be, for example, a thermoplastic resin. Specifically, the resin for forming the foam-molded body may be, for example, one or more kinds selected from the group consisting of: polyurethane; polyolefins, such as polyethylene and polypropylene; polystyrene; a phenol resin; a melamine resin; a nitrile butadiene rubber; a chloroprene rubber; a styrene rubber; a silicone rubber; a urethane rubber; EPDM; and an ethylene-vinyl acetate copolymer.

In the soundproof member <NUM>, the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> each have a thickness of <NUM> or more and <NUM> or less. That is, the thickness L1 of the first elastic porous body layer <NUM> is <NUM> or more and <NUM> or less, and the thickness L2 of the second elastic porous body layer <NUM> is <NUM> or more and <NUM> or less. Accordingly, the total (L1+L2) of the thickness L1 of the first elastic porous body layer <NUM> and the thickness L2 of the second elastic porous body layer <NUM> is <NUM> or more and <NUM> or less. The thickness of each of the elastic porous body layers <NUM> and <NUM> may be <NUM> or more and <NUM> or less, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The thickness L1 of the first elastic porous body layer <NUM> and the thickness L2 of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio (L2/L1) of the thickness L2 of the second elastic porous body layer <NUM> to the thickness L1 of the first elastic porous body layer <NUM> (ratio calculated by dividing the thickness L2 of the second elastic porous body layer <NUM> by the thickness L1 of the first elastic porous body layer <NUM>) may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> each have a bulk density of <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less. That is, the bulk density of the first elastic porous body layer <NUM> is <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less, and the bulk density of the second elastic porous body layer <NUM> is <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less. The bulk density of each of the elastic porous body layers <NUM> and <NUM> may be <NUM>/m<NUM> or more and <NUM>/m<NUM> or less, <NUM>/m<NUM> or more and <NUM>/m<NUM> or less, or <NUM>/m<NUM> or more and <NUM>/m<NUM> or less. The bulk density of each of the elastic porous body layers <NUM> and <NUM> is calculated on the basis of the thickness and mass per unit area thereof, which are measured by methods in conformity with JIS L <NUM>:<NUM>.

The bulk density of the first elastic porous body layer <NUM> and the bulk density of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio of the bulk density of the second elastic porous body layer <NUM> to the bulk density of the first elastic porous body layer <NUM> is <NUM> or more and <NUM> or less, or may be <NUM> or more and <NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> each have a Young's modulus of <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less. That is, the Young's modulus of the first elastic porous body layer <NUM> is <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less, and the Young's modulus of the second elastic porous body layer <NUM> is <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less. The Young's modulus of each of the elastic porous body layers <NUM> and <NUM> may be <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less, or <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less. The Young's modulus of each of the elastic porous body layers <NUM> and <NUM> is measured using, for example, a commercially available measurement apparatus (model QMA2011, manufactured by Mecanum Inc.

The Young's modulus of the first elastic porous body layer <NUM> and the Young's modulus of the second elastic porous body layer <NUM> may be set independently of each other. That is, the Young's modulus of the first elastic porous body layer <NUM> and the Young's modulus of the second elastic porous body layer <NUM> may be equal to or different from each other.

The ratio of the Young's modulus of the second elastic porous body layer <NUM> to the Young's modulus of the first elastic porous body layer <NUM> may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each have, for example, a true density of <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less, <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less, or <NUM>,<NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less. The true density of each of the elastic porous body layers <NUM> and <NUM> is measured in accordance with JIS K <NUM>:<NUM>.

The true density of the first elastic porous body layer <NUM> and the true density of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio of the true density of the second elastic porous body layer <NUM> to the true density of the first elastic porous body layer <NUM> may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

When the first elastic porous body layer <NUM> and/or the second elastic porous body layer <NUM> is a fibrous body layer, the average fiber diameter of fibers forming the fibrous body layer is not particularly limited, but may fall within, for example, the range of from <NUM> or more to <NUM>,<NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each have, for example, a tortuosity of <NUM> (-) or more and <NUM> (-) or less, <NUM> (-) or more and <NUM> (-) or less, or <NUM> (-) or more and <NUM> (-) or less. The tortuosity of each of the elastic porous body layers <NUM> and <NUM> is measured using, for example, a commercially available measurement apparatus (tortuosity and characteristic length measurement system Torvith, manufactured by Nihon Onkyo Engineering Co.

The tortuosity of the first elastic porous body layer <NUM> and the tortuosity of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio of the tortuosity of the second elastic porous body layer <NUM> to the tortuosity of the first elastic porous body layer <NUM> may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each have, for example, a loss factor of <NUM> (-) or more and <NUM> (-) or less, <NUM> (-) or more and <NUM> (-) or less, or <NUM> (-) or more and <NUM> (-) or less.

The loss factor of the first elastic porous body layer <NUM> and the loss factor of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio of the loss factor of the second elastic porous body layer <NUM> to the loss factor of the first elastic porous body layer <NUM> may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each have, for example, a Poisson's ratio of <NUM> or more and <NUM> or less, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less. When the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> are each a fibrous body layer, the Poisson's ratio thereof is nearly <NUM> (zero).

The first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> may each have, for example, a viscous characteristic length of <NUM> or more and <NUM> or less, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The viscous characteristic length of each of the elastic porous body layers <NUM> and <NUM> is measured using, for example, a commercially available measurement apparatus (tortuosity and characteristic length measurement system Torvith, manufactured by Nihon Onkyo Engineering Co.

The viscous characteristic length of each of the elastic porous body layers <NUM> and <NUM> is expressed by the following equation (I) (reference:<NPL>)).

In the equation (I), Λ represents the viscous characteristic length (µm), σ represents a flow resistivity (Ns/m<NUM>), φ represents a porosity (-), η represents the viscosity of air (Pa·s), α∞ represents the tortuosity (-), and Q represents a shape parameter.

The porosity φ is calculated by the following equation (II). In the equation (II), ρ represents the bulk density (kg/m<NUM>), and ρt represents the true density (kg/m<NUM>).

The viscous characteristic length of the first elastic porous body layer <NUM> and the viscous characteristic length of the second elastic porous body layer <NUM> may be set independently of each other. However, the ratio of the viscous characteristic length of the second elastic porous body layer <NUM> to the viscous characteristic length of the first elastic porous body layer <NUM> may be, for example, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first film layer <NUM> and the second film layer <NUM> are each formed of a film. The first film layer <NUM> and the second film layer <NUM> are each preferably formed of a resin film, particularly preferably formed of a thermoplastic resin. Further, the first film layer <NUM> and the second film layer <NUM> are each preferably formed of an elastomer film, particularly preferably formed of a thermoplastic elastomer (TPE).

The thermoplastic elastomer is, for example, one or more selected from the group consisting of: a polyurethane-based thermoplastic elastomer; a polystyrene-based thermoplastic elastomer; a polyester-based thermoplastic elastomer; a polyamide-based thermoplastic elastomer; a polyvinyl chloride thermoplastic elastomer; and a polyolefin-based thermoplastic elastomer.

The thicknesses of the first film layer <NUM> and the second film layer <NUM> are smaller than the thicknesses of the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM>. The thickness of each of the first film layer <NUM> and the second film layer <NUM> may be, for example, <NUM> or more and <NUM> or less, <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less.

The first film layer <NUM> and the second film layer <NUM> are each preferably formed of a non-porous film. The bulk density and true density of each of the first film layer <NUM> and the second film layer <NUM> may each be, for example, <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less, <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less, or <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less.

The film layers <NUM> and <NUM> preferably have such flexibility as to be able to follow oscillatory deformations of the elastic porous body layers <NUM> and <NUM>. The Young's modulus of each of the first film layer <NUM> and the second film layer <NUM> may be, for example, <NUM> MPa or more and <NUM>,<NUM> MPa or less, <NUM> MPa or more and <NUM>,<NUM> MPa or less, or <NUM> MPa or more and <NUM> MPa or less. The Young's modulus of each of the film layers <NUM> and <NUM> is measured by a method in conformity with JIS K7127:<NUM>.

The first elastic porous body layer <NUM> and the first film layer <NUM> may be adjacently arranged via another layer, or may be arranged in contact with each other, but are preferably arranged in contact with each other as illustrated in <FIG>.

Similarly, the second elastic porous body layer <NUM> and the second film layer <NUM> may be adjacently arranged via another layer, or may be arranged in contact with each other, but are preferably arranged in contact with each other as illustrated in <FIG>.

The first film layer <NUM> and the second elastic porous body layer <NUM> may be adjacently arranged via another layer, or may be arranged in contact with each other, but are preferably arranged in contact with each other as illustrated in <FIG>.

The above-mentioned four layers <NUM>, <NUM>, <NUM>, and <NUM> are preferably a press molded body (preferably a hot press molded body) integrally molded by press molding (preferably hot press molding). In this case, the first elastic porous body layer <NUM> and the first film layer <NUM> are preferably arranged in contact with each other, the first film layer <NUM> and the second elastic porous body layer <NUM> are preferably arranged in contact with each other, and the second elastic porous body layer <NUM> and the second film layer <NUM> are preferably arranged in contact with each other.

The soundproof member <NUM> may further include another layer in addition to the above-mentioned four layers <NUM>, <NUM>, <NUM>, and <NUM>. That is, for example, the soundproof member <NUM> may further include another layer on the sound source S side of the first elastic porous body layer <NUM>, and/or may further include another layer on the opposite side of the second film layer <NUM> to the sound source S.

The soundproof member <NUM> has a feature in that the specific parameter (L1/Λ1+L2/Λ2) falls within the specific range of <NUM> or more. The specific parameter (L1/Λ1+L2/Λ2) is calculated as the sum of the ratio (L1/Λ1) of the thickness L1 (mm) of the first elastic porous body layer <NUM> to the viscous characteristic length Λ1 (mm) thereof and the ratio (L2/A2) of the thickness L2 (mm) of the second elastic porous body layer <NUM> to the viscous characteristic length A2 (mm) thereof.

The specific parameter (L1/Λ1+L2/Λ2) of the soundproof member <NUM> is, for example, preferably <NUM> or more, more preferably <NUM> or more, particularly preferably <NUM> or more.

The upper limit value of the specific parameter (L1/Λ1+L2/Λ2) of the soundproof member <NUM> is not particularly limited, but the specific parameter may be, for example, <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. The range of the specific parameter (L1/Λ1+L2/Λ2) of the soundproof member <NUM> may be specified by arbitrarily combining any one of the above-mentioned lower limit values and any one of the above-mentioned upper limit values.

<FIG> shows a relationship, determined through numerical simulation, between the specific parameter (L1/Λ1+L2/Λ2) of a soundproof member (horizontal axis), and the total value (dB) of the perpendicular transmission loss and insertion loss of the soundproof member (vertical axis).

The numerical simulation was performed using a computer having installed thereon commercially available acoustic analysis software (ACTRAN (trademark), manufactured by Free Field Technologies).

Specifically, a model in which vibration and sound were propagated one-dimensionally in the perpendicular direction of a flat plate-shaped soundproof member sample that was, like the soundproof member <NUM> illustrated in <FIG>, formed of a first sound-absorbing layer that was an elastic porous body (corresponding to the first elastic porous body layer <NUM>), a first sound-insulating layer that was a film (corresponding to the first film layer <NUM>), a second sound-absorbing layer that was an elastic porous body (corresponding to the second elastic porous body layer <NUM>), and a second sound-insulating layer that was a film (corresponding to the second film layer <NUM>), which were laminated in the stated order from the sound source side, was created, and the perpendicular transmission loss and insertion loss of the soundproof member sample were calculated. Physical property values included in the software ACTRAN (trademark) were used as the physical property values of air.

In the numerical simulation, for each of the first sound-absorbing layer and the second sound-absorbing layer of the soundproof member sample, the true density ρt was fixed at <NUM>,<NUM>/m<NUM>, the fiber diameter was fixed at <NUM>, the tortuosity α∞ was fixed at <NUM>, the loss factor was fixed at <NUM>, and the Poisson's ratio was fixed at <NUM>, and under these conditions, the thickness was varied from <NUM> to <NUM>, the bulk density was varied from <NUM>/m<NUM> to <NUM>,<NUM>/m<NUM>, and the Young's modulus was varied from <NUM>,<NUM> Pa to <NUM>,<NUM> Pa, and the perpendicular transmission loss and insertion loss of the soundproof member sample were calculated.

Each point plotted in <FIG> is a result calculated by the numerical simulation. The total value (dB) of the perpendicular transmission loss and the insertion loss shown on the vertical axis of <FIG> is an average value calculated by subjecting results, calculated in the frequency range of from <NUM> or more to <NUM>,<NUM> or less by the numerical simulation, to weighted correction in consideration of the frequency characteristics of the human ear (e.g., difficulty in hearing low-frequency sound).

As shown in <FIG>, the inventors of the present invention have made extensive investigations regarding what configuration a soundproof member having excellent soundproof characteristics has, in particular, regarding a configuration required for improving not only the transmission loss, but also the insertion loss, and as a result, have found that, surprisingly, the specific parameter (L1/Λ1+L2/Λ2), i.e., the total of the ratio (L1/Λ1) of the thickness L1 (mm) of the first elastic porous body layer <NUM> to the viscous characteristic length Λ1 (µm) thereof and the ratio (L2/Λ2) of the thickness L2 (mm) of the second elastic porous body layer <NUM> to the viscous characteristic length A2 (µm) thereof shows a high correlation with the total of the transmission loss and the insertion loss.

The soundproof member <NUM> according to the present invention has a configuration and soundproof characteristics (specifically, such soundproof characteristics that the total of the acoustic loss and the insertion loss is <NUM> dB or more) corresponding to, among the points plotted in <FIG>, points plotted within the range in which the specific parameter (L1/A1+L2/A2) on the horizontal axis is <NUM> or more (more specifically, <NUM> or more and <NUM> or less).

In <FIG>, the point plotted as a white circle represents the specific parameter (L1/Λ1+L2/Λ2) and soundproof characteristics of Example actually realized as an example of the soundproof member <NUM> according to the present invention.

That is, the soundproof member <NUM> according to this Example was a flat plate-shaped hot press molded body formed of the first elastic porous body layer <NUM>, the first film layer <NUM>, the second elastic porous body layer <NUM>, and the second film layer <NUM> that were laminated in the stated order from the sound source side, and had a specific parameter (L1/Λ1+L2/Λ2) of <NUM> (-) and a total of acoustic loss and insertion loss of <NUM> dB.

Specifically, each of the first elastic porous body layer <NUM> and the second elastic porous body layer <NUM> included in the soundproof member <NUM> according to Example was a nonwoven fabric (organic fibrous body layer) obtained by needle-punching PET fibers partially joined by another resin fiber and having an average fiber diameter of <NUM>, and had a thickness of <NUM>, a bulk density of <NUM>/m<NUM>, a true density of <NUM>,<NUM>/m<NUM>, a Young's modulus of <NUM>,<NUM> Pa, a viscous characteristic length of <NUM>, a tortuosity of <NUM> (-), a loss factor of <NUM> (-), and a Poisson's ratio of nearly <NUM> (zero).

In addition, each of the first film layer <NUM> and the second film layer <NUM> included in the soundproof member <NUM> according to Example was a non-porous film of a polyurethane-based thermoplastic elastomer, and had a thickness of <NUM>, a bulk density and true density of <NUM>,<NUM>/m<NUM>, and a Young's modulus of <NUM> MPa.

Meanwhile, in <FIG>, the black filled rhombus is plotted, as Comparative Example <NUM>, for a soundproof member that is a flat plate-shaped hot press molded body formed of a first sound-absorbing layer that is polyurethane foam, a first sound-insulating layer that is a non-porous film of a polyurethane-based thermoplastic elastomer, a second sound-absorbing layer that is polyurethane foam, and a second sound-insulating layer that is a non-porous film of a polyurethane-based thermoplastic elastomer, which are laminated in the stated order from the sound source side. The soundproof member according to Comparative Example <NUM> had a specific parameter (L1/Λ1+L2/Λ2) of <NUM> (-), and a total of acoustic loss and insertion loss of <NUM> dB.

In addition, in <FIG>, the black filled triangle is plotted, as Comparative Example <NUM>, for a soundproof member formed of one sound-absorbing layer that is polyurethane foam. The soundproof member according to Comparative Example <NUM> had a specific parameter (L1/Λ1+L2/Λ2) of <NUM> (-), and a total of acoustic loss and insertion loss of <NUM> dB.

In addition, in <FIG>, the black filled circle is plotted, as Comparative Example <NUM>, for a soundproof member formed of single sound-absorbing layer that is an organic fibrous body (PET fibrous body) identical to each of the nonwoven fabrics included as the elastic porous body layers <NUM> and <NUM> in the soundproof member <NUM> according to Example described above. The soundproof member according to Comparative Example <NUM> had a specific parameter (L1/Λ1+L2/Λ2) of <NUM> (-), and a total of acoustic loss and insertion loss of <NUM> dB.

<FIG> is a plot of the results of the above-mentioned numerical simulation with the horizontal axis representing the total (L1+L2) of the thickness of the first sound-absorbing layer (corresponding to the thickness L1 of the first elastic porous body layer <NUM>) and the thickness of the second sound-absorbing layer (corresponding to the thickness L2 of the second elastic porous body layer <NUM>).

<FIG> is a plot of the results of the above-mentioned numerical simulation with the horizontal axis representing the total (A1+A2) of the viscous characteristic length of the first sound-absorbing layer (corresponding to the viscous characteristic length Λ1 of the first elastic porous body layer <NUM>) and the viscous characteristic length of the second sound-absorbing layer (corresponding to the viscous characteristic length A2 of the second elastic porous body layer <NUM>).

Claim 1:
A soundproof member (<NUM>), comprising:
a first elastic porous body layer (<NUM>);
a first film layer (<NUM>);
a second elastic porous body layer (<NUM>); and
a second film layer (<NUM>),
the layers being arranged in the stated order from a sound source side,
wherein the first elastic porous body layer (<NUM>) and the second elastic porous body layer (<NUM>) each have:
a thickness of <NUM> or more and <NUM> or less;
a bulk density of <NUM>/m<NUM> or more and <NUM>,<NUM>/m<NUM> or less; and
a Young's modulus of <NUM>,<NUM> Pa or more and <NUM>,<NUM> Pa or less, and
characterized in that a total, L1/Λ1 + L2/Λ2, of a ratio, L1/Λ1, of the thickness L1, in mm, of the first elastic porous body layer (<NUM>) to a viscous characteristic length Λ1, in µm, thereof and a ratio, L2/Λ2, of the thickness L2, in mm, of the second elastic porous body layer (<NUM>) to a viscous characteristic length Λ2, in µm, thereof is <NUM> or more, and
wherein a ratio of the bulk density of the second elastic porous body layer (<NUM>) to the bulk density of the first elastic porous body layer (<NUM>) is <NUM> or more and <NUM> or less.