JP6916879B2 - Soundproof structures, vehicle parts and automobiles - Google Patents

Description

The present invention relates to soundproof structures, vehicle parts and automobiles.

Vehicles such as automobiles are machines that have a power source such as an engine and can be moved by human operation, and generate various vibrations and noises. The sound transmitted to the inside of the vehicle includes not only the sound generated by the power source but also the sound generated outside the vehicle such as road noise, tire pattern noise, wind noise, etc. generated when the vehicle is running. .. If these sounds are transmitted to the inside of the vehicle, it causes discomfort to people. Therefore, soundproofing materials are used in the engine, engine room, interior, body, exhaust pipe area, etc. Measures are being taken.

Patent Document 1 describes an introduction passage that opens on one side of a flexible porous foam formed by foam molding, and a hollow portion that is formed in the back of the introduction passage and has a cross-sectional area larger than that of the introduction passage. A sound absorbing material having a large number of resonance chambers is disclosed.

Patent Document 2 discloses a sound absorbing / insulating structure comprising a resin molded body having a plurality of independent blind cavities having openings on the front surface or the back surface and a sound absorbing material, and having a specific 100 Hz to 10 kHz resonance sound absorbing peak frequency. Has been done.

Japanese Unexamined Patent Publication No. 08-260589 Japanese Unexamined Patent Publication No. 2001-249666

However, with the technological improvement of automobiles, there is a need for new soundproofing measures for automobiles. For example, lowering the center of gravity and ground clearance of automobiles is being considered as one of the measures to improve the fuel efficiency of automobiles. By lowering the center of gravity of the vehicle, the stability and operability of the vehicle can be improved, and by lowering the minimum ground clearance, air resistance can be reduced. However, as the minimum ground clearance of the vehicle becomes lower, the viscosity of the air flowing between the vehicle and the road surface during traveling increases. Then, noise generated from the road surface during running, such as tire pattern noise (frequency range of 500 to 3000 Hz, also simply referred to as pattern noise), is difficult to be reflected and diffused to the surroundings under the vehicle body, and the degree of noise entering the vehicle is high. Is estimated to be high. Similar problems can occur in electric vehicles.

Therefore, if the center of gravity and ground clearance of a car are lowered in order to improve the fuel efficiency of the car, it is assumed that the noise that was conventionally diffused outside the car will be transmitted to the person in the car. .. In particular, it is considered that these noises are likely to enter from the rear part of the vehicle and the bottom of the lower part of the luggage room (underfloor space) where the accommodation space is arranged. Since these noises include noises in the frequency range of 500 to 2000 Hz, which are unpleasant for humans, countermeasures are required.

Here, when the opening of a member having an opening, such as the sound absorbing material described in Patent Document 1 or the resin molded body described in Patent Document 2, is arranged to face the member constituting the vehicle, a person I sometimes felt unpleasant noise in the frequency range of 500 to 2000 Hz, but the cause was not well understood.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a soundproof structure capable of taking measures against noise in the frequency range of 500 to 2000 Hz, which is unpleasant for humans. do.

The cause of the noise in the frequency range of 500 to 2000 Hz, which makes people uncomfortable when the members described in Patent Documents 1 and 2 are arranged in the vehicle, has not been well understood, but the present inventor of the present invention. As a result of their examination, it has been empirically found that such noise may or may not be felt.
As a result of further studies, it was presumed that the cause of this noise was a phenomenon in which sound of a specific frequency called the resonance transmission frequency was transmitted through the soundproofing material due to resonance resonance.

Then, the present inventors obtain a resonance transmission frequency f in a soundproof structure provided with a sound absorbing material having a Helmholtz resonance structure and a sound insulating material, and design the soundproof structure so that f is less than 500 Hz. As a result, it has been found that the noise in the frequency range, which is unpleasant for humans, is not felt, and the soundproof structure suitable for use in a vehicle can be obtained.

{式（１）におけるＭは以下の式（２）で示され、Ｋは以下の式（３)で示される。

［式（３）におけるＫＨは以下の式（４）で示され、ＫＨＡは以下の式（５）で示される。

］｝That is, the soundproof structure of the present invention includes a sound absorbing material having a non-through hole and a sound absorbing material.
A soundproof structure comprising a soundproofing material provided with a predetermined distance separated by an air layer so as to face the surface of the sound absorbing material through which the non-penetrating holes are opened.
The non-through hole of the sound absorbing material has a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage.
Let L be the thickness of the air layer.
The circle-equivalent diameter of the introduction passage is d, the opening area is SH, and the thickness is t3.
The circle-equivalent diameter of the hollow portion is dV, the opening area is SV, the volume is V, and the thickness is t2.
The density of the material portion other than the non-through hole portion of the sound absorbing material is ρm, and the thickness obtained by subtracting the thickness t3 of the introduction passage and the thickness t2 of the hollow portion from the thickness T of the sound absorbing material is t1.
The thickness of the air layer is L, the density of air is ρ0 = 0.001293 g / cm ³ , and the speed of sound is C = 34000 cm / sec.
t1, t2 and t3 are all 0.1 cm or more and 5.0 cm or less,
d is 0.3 cm or more and 3.0 cm or less,
dV is 0.4 cm or more and 17.1 cm or less,
In the range where L is larger than 0 cm
The following equation (1) holds for the resonance transmission frequency f (Hz).

{M in the formula (1) is represented by the following formula (2), and K is represented by the following formula (3).

[KH in the formula (3) is represented by the following formula (4), and KHA is represented by the following formula (5).

]}

In the soundproof structure of the present invention, the shape of the non-through hole of the Helmholtz resonance structure and the thickness of the air layer between the sound absorbing material and the sound insulating material are adjusted so that the resonance transmission frequency f is less than 500 Hz. Therefore, the frequency of the sound coming out of the soundproof structure deviates from the frequency range of 500 to 2000 Hz, which is unpleasant for humans. Therefore, the soundproof structure can take measures against noise in the frequency range of 500 to 2000 Hz, which makes people uncomfortable.

The equivalent circle diameter is the cross-sectional area (opening area SH or opening area SV) of the introduction passage or hollow portion when the introduction passage or hollow portion is cut in a direction perpendicular to the thickness direction. It is the diameter when replaced with a perfect circle. When the cross-sectional shape of the introduction passage or the hollow portion is a perfect circle, the diameter thereof may be used as it is as the diameter equivalent to the circle.
Further, in the soundproof structure of the present invention, n introduction passages having the same shape (n is a natural number of 2 or more) may be formed in one hollow portion of the sound absorbing material.
In this case, when the sound reaches each introduction passage of the sound absorbing material, the air in each introduction passage is simultaneously pushed toward the hollow portion. Since the air in the hollow part is an elastic body, it tries to push the air in the introduction passage to the outside.
The force that pushes the air out of the introduction passage depends on the volume of air in the hollow portion, in which case the Helmholtz resonance mechanism has a hollow portion with a volume of V / n in one introduction passage. It can be considered that there are n pieces. Further, it can be considered that M also has a resonance mechanism having a mass of M / n.
That is, the force for pushing air out to one introduction passage can be approximately calculated based on the value obtained by dividing the volume of air in the hollow portion by the number of introduction passages. Further, similarly, the opening area SV of the hollow portion can also be calculated as SV / n.
That is, in the above equation (1), the resonance transmission frequency f can be calculated by calculating as a value obtained by dividing V, M, and SV by n. Since SH is the area per introduction passage, the resonance transmission frequency f is calculated as it is without dividing by n.
In the soundproof structure of the present invention, a plurality of layers (n) of the constituent material (that is, the portion whose thickness is represented by t1) between the hollow portion of the sound absorbing material and the surface opposite to the opening surface of the hollow portion are formed. In the case of (1), M in the formula (1) is the density ρmk (k = 1 ... n n is a natural number) of each constituent material and the thickness t1k (k = 1 ... n) of each constituent material. When n is a natural number), it can be calculated as M = ρm1 × t11 × SV + ρm2 × t12 × SV + ... + ρmn × t1n × SV.
In the soundproof structure of the present invention, the air density and the speed of sound are ^{treated as constants with the air density ρ0 = 0.001293 g / cm 3} and the speed of sound C = 34000 cm / sec.

In the soundproof structure of the present invention, it is preferable that the sound absorbing material is made of a resin or a fibrous material. The resin is preferably an elastomer such as a foamed resin or rubber.
When the sound absorbing material is made of resin, it is particularly preferable as a vehicle part because it is easy to reduce the weight.
Further, when the resin is a foamed resin, its weight can be made lighter, and it can contribute to the improvement of fuel efficiency when it is used as a vehicle component.
In the soundproof structure of the present invention, the constituent material may be a composite material of resin and fiber. As a method of compounding, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

In the soundproof structure of the present invention, the soundproofing material is preferably a steel plate.

In the soundproof structure of the present invention, it is preferable that f in the formula (1) is larger than 50 Hz.

The vehicle component of the present invention is characterized by comprising the soundproof structure of the present invention.
Since the soundproof structure of the present invention is excellent in soundproofing performance, it is excellent as a vehicle component.
Examples of vehicle parts provided with the soundproof structure of the present invention include a raising material, a partition member, a luggage box, and the like.

The automobile of the present invention is characterized in that the soundproof structure of the present invention is arranged with the soundproofing material facing the road surface direction.
By arranging the sound insulating material of the present invention with the sound insulating material facing the road surface, it is possible to prevent the noise of the tire pattern noise transmitted from the road surface from being transmitted to the inside of the vehicle through the sound insulating structure.

FIG. 1 is a cross-sectional view schematically showing the structure of the soundproof structure of the present invention for explaining the formula (1). FIG. 2 is a cross-sectional view schematically showing a spring and a mass portion in the cross-sectional view of the soundproof structure shown in FIG. FIG. 3 is a cross-sectional view schematically showing only the spring and the mass portion of the soundproof structure shown in FIG. FIG. 4 is a graph showing an example of adjusting the resonance transmission frequency f. 5 (a) is a perspective view schematically showing an example of a sound absorbing material constituting the soundproof structure of the present invention, and FIG. 5 (b) is a cross-sectional view taken along the line AA in FIG. 5 (a). .. FIG. 6 is a perspective view schematically showing an example of the soundproof structure of the present invention. FIG. 7A is a perspective view schematically showing an example of a mold used in a method for manufacturing a sound absorbing material, and FIG. 7B is a sectional view taken along line BB of FIG. 7A. FIG. 8 is an explanatory diagram schematically showing an example of a step of producing a foamed resin in a method for producing a sound absorbing material. 9 (a), 9 (b), and 9 (c) are explanatory views schematically showing an example of a step of extracting protrusions from the foamed resin in a method for producing a sound absorbing material. FIG. 10A is an explanatory view schematically showing an example of a portion where the soundproof structure of the present invention is arranged, and FIG. 10B is a portion of a region shown by a broken line portion in FIG. 10A. It is an enlarged view. FIG. 11 is an explanatory diagram schematically showing an outline of an acoustic transmission loss test for a soundproof structure. 12 (a), 12 (b) and 12 (c) are graphs showing the relationship between the frequency and the transmission loss in Examples 1, 2 and 3, respectively. 13 (a) and 13 (b) are graphs showing the relationship between the frequency and the transmission loss in Comparative Examples 1 and 2, respectively.

(Detailed description of the invention)
Hereinafter, the soundproof structure of the present invention will be described in detail.
The soundproof structure of the present invention includes a sound absorbing material having a non-through hole and a sound insulating material provided so as to face a surface of the sound absorbing material in which the non-through hole is opened and separated by a predetermined distance with an air layer. Consists of.

First, the sound absorbing material constituting the soundproof structure of the present invention will be described.
The sound absorbing material constituting the soundproof structure of the present invention is a member having a non-through hole, and the non-through hole is a Helmholtz composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage. It has a resonance structure.
The details of the shape of the non-through hole will be described in detail later.

It is preferable that the portion other than the non-through hole portion of the sound absorbing material constituting the soundproof structure of the present invention is made of resin. The resin is preferably any one of a foamed resin composed of foamable resin particles (beads), a foamed resin having bubbles, a fiber, a thermoplastic resin, and a thermosetting resin.
Among these, a foamed resin is more preferable.
The density of the resin constituting the sound absorbing material in the soundproof structure of the present invention ^{is preferably 0.01 to 0.5 g / cm 3} , and the density ρm is 0.02 to 0.1 g / cm ³ . Is even more desirable. When the resin is a foamed resin, the density of the resin refers to the density of the foamed resin that has been foam-molded.
When the density of the resin is within the above range, it is easy to obtain the strength required as a sound absorbing material.
On the other hand, if the density of the resin ^{is less than 0.01 g / cm 3} , sufficient mechanical strength as a sound absorbing material may not be obtained. Further, when the density of the resin ^{exceeds 0.5 g / cm 3} , the weight of the sound absorbing material increases, which hinders the weight reduction of the vehicle.
Further, the resin constituting the sound absorbing material in the soundproof structure of the present invention is more preferably a foamed resin composed of foamable resin particles (beads). When the resin is a foamed resin composed of foamable resin particles (beads), the weight of the sound absorbing material can be reduced while maintaining the strength, which can contribute to the improvement of fuel efficiency when used for vehicle parts. ..
The foamed resin is obtained by foaming and molding foamable resin particles.

The foamable resin particles (beads) constituting the sound absorbing material in the soundproof structure of the present invention are particles containing a foaming agent inside the resin particles, and known particles can be preferably used.
Examples of the resin component constituting the foamable resin particles constituting the sound absorbing material in the soundproof structure of the present invention include olefin resins such as polyethylene and polypropylene, and styrene resins such as polystyrene. Examples of the styrene resin include a styrene homopolymer and a copolymer obtained by copolymerizing styrene and a monomer (or a derivative thereof) copolymerizable with styrene. The styrene copolymer may be a block copolymer, a random copolymer, or a graft copolymer.
Examples of the foaming agent include hydrocarbons such as propane, butane, and pentane.

The foamable resin particles constituting the sound absorbing material in the soundproof structure of the present invention may be, if necessary, a flame retardant, a flame retardant aid, a processing aid, a filler, an antioxidant, a light resistance stabilizer, and an antistatic agent. Known additives such as agents and colorants may be added. As an example of the use of additives, if a black colorant is used, stains will not be noticeable.

Flame retardants include metal hydrated flame retardants such as aluminum hydroxide and magnesium hydroxide, phosphoric acid flame retardants such as red phosphorus and ammonium phosphate, tetrabromobisphenol A (TABB), brominated polystyrene, and chlorinated paraffin. Halogen-based flame retardants such as, ammonium carbonate, nitrogen-based flame retardants such as melamine cyanurate, and the like can be mentioned.
Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.
Examples of the processing aid include stearate, liquid paraffin, olefin wax, stearylamide compound, epoxy compound and the like.
Examples of the filler include silica, talc, calcium silicate and the like.
Examples of the antioxidant include alkylphenols, alkylenebisphenols, alkylphenol thioethers, β, β-thiopropionic acid esters, organic phosphite esters, phenol-nickel complexes and the like.
Examples of the light resistance stabilizer include benzotriazole-based ultraviolet absorbers and hindered amine-based stabilizers.
Examples of the antistatic agent include low molecular weight antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds and aliphatic ethanolamide compounds, and high molecular weight antistatic agents.
Examples of the colorant include dyes and pigments.

The average particle size of the foamable resin particles constituting the sound absorbing material in the soundproof structure of the present invention is preferably 300 μm to 2400 μm, and more preferably 800 μm to 2000 μm.
The foaming ratio of the foamable resin particles constituting the sound absorbing material in the soundproof structure of the present invention is preferably 10 to 60 times.
By setting the foaming ratio in the range of 10 to 60 times, it becomes easy to adjust ^{the density of the resin in the range of 0.02 to 0.1 g / cm 3.}
On the other hand, when the foaming ratio is less than 10 times, the sound absorbing material may become too hard or too heavy. If the foaming ratio exceeds 60 times, the strength of the sound absorbing material may be insufficient.
As the foamed resin having bubbles constituting the sound absorbing material in the soundproof structure of the present invention, polyurethane or the like can be used. By mixing polyurethane, a foaming agent, etc. as a main agent, foaming, and molding, a foamed resin having air bubbles can be obtained, and a sound absorbing material can be produced by this.
Organic fibers and inorganic fibers can be used as the fiber material constituting the sound absorbing material in the soundproof structure of the present invention, and polyester, polyamide, acetate and the like can be used as the organic fibers. As the inorganic fiber, alumina, silica, and mullite fiber are desirable. It is desirable to bond the fibers together with a binder to form a felt.
As the thermoplastic resin constituting the sound absorbing material in the soundproof structure of the present invention, polypropylene resin, polyethylene resin, polyester resin, polystyrene resin and the like can be used. A sound absorbing material can be produced by molding a thermoplastic resin as a resin pellet, heating the resin pellet, and performing a molding process such as injection molding or extrusion molding.
As the thermosetting resin constituting the sound absorbing material in the soundproof structure of the present invention, melamine resin, urea resin, polyurethane, polyurea, polyamide, polyacrylamide and the like can be used. A sound absorbing material can be produced by preheating a thermosetting resin, putting it in a mold, pressurizing it, raising the mold temperature, and curing it.

Further, the portion of the soundproof structure of the present invention other than the non-through hole portion of the sound absorbing material may be made of a material such as an inorganic material or a metal material in addition to the resin material.

The thickness T of the sound absorbing material in the soundproof structure of the present invention is not particularly limited, but is preferably 1.0 cm or more.
Further, the thickness T of the sound absorbing material is preferably 12 cm or less. Further, it is more desirable that the thickness T of the sound absorbing material is 2 to 10 cm.
If the thickness of the sound absorbing material is less than 1 cm, the length of the non-through hole becomes too short, and it may be difficult to design a soundproof structure having a predetermined resonance transmission frequency.

The non-through hole provided in the sound absorbing material in the soundproof structure of the present invention has a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage.
Further, the shapes of the plurality of non-through holes provided in the sound absorbing material may be the same shape or different shapes.

The introduction passage provided in the sound absorbing material in the soundproof structure of the present invention has a circle-equivalent diameter of d, an opening area of SH, and a thickness of t3.
The shape of the introduction passage provided in the sound absorbing material in the soundproof structure of the present invention is preferably cylindrical or prismatic. That is, it is preferable that the opening area SH has a constant shape at any position in the thickness direction.
Further, the cross-sectional shape when the introduction passage provided in the sound absorbing material in the soundproof structure of the present invention is cut in the direction perpendicular to the thickness direction is circular, elliptical, triangular, quadrangular, hexagonal, octagonal or the like. It may be, preferably circular or oval. This is because stress is not concentrated from the corners in these circular and elliptical shapes because there are no corners.
The circular equivalent diameter d of the introduction passage provided in the sound absorbing material in the soundproof structure of the present invention is 0.3 cm or more and 3.0 cm or less, preferably 0.5 cm or more, and preferably 2.0 cm or less. preferable.
The opening area SH of the introduction passage provided in the sound absorbing material in the soundproof structure of the present invention is preferably ^{0.007 to 7.5 cm 2.}
The opening area SH referred to here is the opening area of the introduction passage per non-through hole.
When the opening area SH is within the above range, the sound received by the sound absorbing material can be sufficiently sent into the hollow portion, so that the soundproofing performance is excellent.
The thickness t3 of the introduction passage provided in the sound absorbing material in the soundproof structure of the present invention is 0.1 cm or more and 5.0 cm or less, preferably 0.5 cm or more, and preferably 2.0 cm or less. preferable.

The hollow portion provided in the sound absorbing material in the soundproof structure of the present invention has a circle-equivalent diameter of dV, an opening area of SV, a volume of V, and a thickness of t2.
The shape of the hollow portion provided in the sound absorbing material in the soundproof structure of the present invention is preferably cylindrical or prismatic. That is, it is preferable that the opening area SV has a constant shape at any position in the thickness direction.
Further, the cross-sectional shape when the hollow portion provided in the sound absorbing material in the soundproof structure of the present invention is cut in the direction perpendicular to the thickness direction is circular, elliptical, triangular, quadrangular, hexagonal, octagonal or the like. It may be, preferably circular or oval. This is because stress is not concentrated from the corners in these circular and elliptical shapes because there are no corners.
Further, in the sound absorbing material in the soundproof structure of the present invention, the above-mentioned shapes may be different or the same in the introduction passage and the hollow portion.
Further, in the sound absorbing material in the soundproof structure of the present invention, the positional relationship between the introduction passage and the hollow portion may be such that the hollow portion is connected to the outside via the introduction passage, and the center (non-penetrating) of the introduction passage and the hollow portion. The centers in the cross-sectional shape when cut in the direction perpendicular to the thickness direction of the holes) may or may not match.
In the sound absorbing material in the soundproof structure of the present invention, the circular equivalent diameter dV of the hollow portion is 0.4 cm or more and 17.1 cm or less, preferably 1.0 cm or more, and preferably 15 cm or less.
In the sound absorbing material in the soundproof structure of the present invention, the opening area SV of the hollow portion is preferably ^{0.125 to 229 cm 2.}
The opening area SV referred to here is the opening area of the hollow portion per non-through hole.
When the opening area SV is within the above range, the sound received by the sound absorbing material is easily reflected in the hollow portion, so that the soundproofing performance is excellent.
In the sound absorbing material in the soundproof structure of the present invention, the volume V of the hollow portion is preferably ^{0.0028 to 1145 cm 3.}
The volume V of the hollow portion referred to here is the volume of the hollow portion per non-through hole.
In the sound absorbing material in the soundproof structure of the present invention, the thickness t2 of the hollow portion is 0.1 cm or more and 5.0 cm or less, preferably 0.5 cm or more, and preferably 2.0 cm or less.

Further, in the sound absorbing material in the soundproof structure of the present invention, the preferable relationship between the dimensions of the introduction passage and the hollow portion in the non-through hole is as follows.
It is preferable that the thickness t3 of the introduction passage and the thickness t2 of the hollow portion are the same, and the ratio of the thickness t3 of the introduction passage and the thickness t2 of the hollow portion is not particularly limited, but is 2: 1 to 1: 1. It is also preferable that it is 4.
Further, it is preferable that the total of the thickness t3 of the introduction passage and the thickness t2 of the hollow portion is 1.0 cm or more.
When the total of the thickness t3 of the introduction passage and the thickness t2 of the hollow portion is 1.0 cm or more, soundproofing performance in the frequency range of 500 to 2000 Hz can be easily obtained, and noise due to tire pattern noise can be particularly reduced.

In the sound absorbing material in the soundproof structure of the present invention, the thickness obtained by subtracting the thickness t3 of the introduction passage and the thickness t2 of the hollow portion from the thickness T of the sound absorbing material is defined as t1. t1 corresponds to the thickness of the mass part M described later.
t1 is 0.1 cm or more and 5.0 cm or less, preferably 0.5 cm or more, and preferably 2.0 cm or less.
t1 corresponds to the thickness of the material portion other than the non-through hole portion, which is located on the surface of the sound absorbing material opposite to the surface on which the non-through hole is opened.

The arrangement pattern of the non-through holes opened on the surface of the sound absorbing material in the soundproof structure of the present invention may be an equilateral arrangement in which the non-through holes are arranged at the vertices of the squares in a plane in which the squares are continuously arranged vertically and horizontally. , It may be a staggered arrangement in which non-through holes are arranged at the vertices of the triangles in a plane in which equilateral triangles are arranged continuously in the vertical and horizontal directions.
Among these, a staggered arrangement is desirable. When the arrangement pattern of the non-through holes is a staggered arrangement, all the adjacent non-through holes tend to be evenly spaced, so that the sound attenuation efficiency is good.

The sound insulation material in the soundproof structure of the present invention will be described.
The sound insulation material in the soundproof structure of the present invention is a member provided so as to face the surface through which the non-penetrating holes of the sound absorbing material are opened and separated by a predetermined distance with an air layer. A connecting member for providing an air layer may be separately provided between the sound absorbing material and the sound insulating material, and sound insulation is provided by fixing the sound absorbing material and the sound insulating material at the place where the soundproof structure of the present invention is installed. An air layer may be provided between the material and the sound absorbing material.

The sound insulation material in the soundproof structure of the present invention is preferably a plate-shaped member, and preferably a steel plate.
When the place where the soundproof structure of the present invention is installed is inside the vehicle, a part of the steel plate constituting the vehicle body can be regarded as the soundproof material.
The sound insulation material in the soundproof structure of the present invention preferably has a thickness of 0.1 to 20 cm. Further, it is preferable to have an area larger than the area of the surface on which the non-through hole of the sound absorbing material is opened, and when the sound insulating material is arranged facing the surface on which the non-through hole of the sound absorbing material is opened, the non-through hole is formed. It is preferable that a sound insulating material is present for the opening.

The thickness L of the air layer in the soundproof structure of the present invention is a predetermined distance between the sound absorbing material and the sound insulating material, and the thickness L of the air layer is 0 cm or more, preferably 0.1 to 20 cm.
In the soundproof structure of the present invention, it is preferable that the sound absorbing material and the sound insulating material are arranged so that their surfaces are parallel to each other. In this case, the thickness of the air layer is constant. If there is a step on the surface of the sound absorbing material or sound insulating material, or if the surfaces of the sound absorbing material and the sound insulating material are arranged so as not to be parallel, the thickness of the air layer is the average of the distance between the sound absorbing material and the sound insulating material. It is preferable to set it as a value (average value at 9 points).
Further, the air density ρ0 is 0.001293 g / cm ³ , and the sound velocity C is 34000 cm / sec.

{式（１）におけるＭは以下の式（２）で示され、Ｋは以下の式（３)で示される。

［式（３）におけるＫＨは以下の式（４）で示され、ＫＨＡは以下の式（５）で示される。

］｝The soundproof structure of the present invention described so far is
t1, t2 and t3 are all 0.1 cm or more and 5.0 cm or less,
d is 0.3 cm or more and 3.0 cm or less,
dV is 0.4 cm or more and 17.1 cm or less,
In the range where L is larger than 0 cm
The following equation (1) holds for the resonance transmission frequency f (Hz).

{M in the formula (1) is represented by the following formula (2), and K is represented by the following formula (3).

[KH in the formula (3) is represented by the following formula (4), and KHA is represented by the following formula (5).

]}

Equation (1) is a basic equation for obtaining the resonance transmission frequency f, and is an equation for obtaining a frequency at which the acoustic transmission loss becomes lower than the value predicted from the mass law.

Hereinafter, the technical significance of the equation (1) in the soundproof structure of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing the structure of the soundproof structure of the present invention for explaining the formula (1).
The soundproof structure 1 shown in FIG. 1 is composed of a sound absorbing material 10 having a non-through hole 30 and a sound insulating material 20.
The non-through hole 30 has an introduction passage 31 and a hollow portion 32.
The circle-equivalent diameter of the introduction passage 31 is indicated by a double-headed arrow d, and the circular-equivalent diameter of the hollow portion 32 is indicated by a double-headed arrow dV.
Since the shapes of the sound absorbing material introduction passage 31 and the hollow portion 32 shown in FIG. 1 are both cylindrical, the circular equivalent diameter d of the introduction passage 31 and the circular equivalent diameter dV of the hollow portion 32 are both cylindrical diameters. ..
Further, the thickness of the sound absorbing material 10 is indicated by T, the thickness of the introduction passage 31 is indicated by t3, and the thickness of the hollow portion 32 is indicated by t2. The thickness obtained by subtracting the thickness t2 of the portion 32 is shown as t1.
The thickness of the air layer between the sound absorbing material 10 and the sound insulating material 20 is shown as L.

FIG. 2 is a cross-sectional view schematically showing a spring and a mass part in the cross-sectional view of the soundproof structure shown in FIG. 1, and FIG. 3 schematically shows only the spring and the mass part of the soundproof structure shown in FIG. It is sectional drawing which shows.
In FIG. 2, a portion made of a material other than the non-through hole portion of the sound absorbing material, which is located above the hollow portion 32, is shown as a mass portion M with different hatching.
Further, in order to model the vibration of the sound transmitted from the sound insulating material 20 to the mass portion M through the non-through hole 30 of the sound absorbing material 10, the spring KH, which is two springs, is sandwiched between the mass portion M and the sound insulating material 20. And the model connected by spring KHA is shown.
Further, in order to obtain the spring constant KHA of the spring KHA, it is necessary to consider the spring KA connecting between the sound absorbing material 10 and the sound insulating material 20, so it is shown in FIG.
FIG. 3 is a diagram showing only the mass portion M, the spring KH, and the spring KHA.
Hereinafter, the technical significance of the equation (1) will be described with reference to FIGS. 2 and 3.

ρｍは質量部Ｍを構成する材料の密度であり、ＳＶ×ｔ１は質量部Ｍの体積であるので、Ｍは質量部Ｍの重量に相当する。M in the formula (1) is represented by the following formula (2).

Since ρm is the density of the material constituting the mass part M and SV × t1 is the volume of the mass part M, M corresponds to the weight of the mass part M.

式（３）におけるＫＨはバネＫＨのバネ定数であり、ＫＨＡはバネＫＨＡのバネ定数である。
式（３）はバネＫＨとバネＫＨＡを直列接続したときの合成バネ定数Ｋを示している。K in the formula (1) is represented by the following formula (3).

KH in the formula (3) is the spring constant of the spring KH, and KHA is the spring constant of the spring KHA.
Equation (3) shows the synthetic spring constant K when the spring KH and the spring KHA are connected in series.

バネ定数ＫＨは、非貫通孔の導入通路及び中空部の寸法により決まるバネ定数であり、ρ０とＣは定数として考えるので、導入通路の開口面積ＳＨと中空部の体積Ｖにより定まる。Equation (4) shows the spring constant KH of the spring KH.

The spring constant KH is a spring constant determined by the dimensions of the introduction passage and the hollow portion of the non-through hole, and since ρ0 and C are considered as constants, they are determined by the opening area SH of the introduction passage and the volume V of the hollow portion.

式（７）で規定するバネ定数ＫＡは、遮音材から吸音材の非貫通孔の導入通路に到達するまでの振動に対応するバネ定数であり、ρ０とＣは定数として考えるので、中空部の開口面積ＳＶと、空気層の厚さＬにより定まる。
式（６）で規定するバネ定数ＫＨＡは、式（７）により定めたバネ定数ＫＡに対して、音が導入通路を通る影響を踏まえて補正することにより定められるバネ定数であり、この補正には導入通路の開口面積ＳＶと中空部の開口面積ＳＨを使用する。
式（６）のバネ定数ＫＡとして式（７）を代入してバネ定数ＫＨＡを表すと式（５）となる。

The spring constant KHA of the spring KHA in the formula (3) can be obtained from the formulas (6) and (7).

The spring constant KA defined by the equation (7) is a spring constant corresponding to the vibration from the sound insulating material to the introduction passage of the non-through hole of the sound absorbing material, and ρ0 and C are considered as constants. It is determined by the opening area SV and the thickness L of the air layer.
The spring constant KHA specified by the equation (6) is a spring constant determined by correcting the spring constant KA determined by the equation (7) in consideration of the influence of sound passing through the introduction passage, and this correction is used. Uses the opening area SV of the introduction passage and the opening area SH of the hollow portion.
Substituting the equation (7) as the spring constant KA of the equation (6) to express the spring constant KHA, the equation (5) is obtained.

In this way, KH and KHA are determined by defining each variable representing the dimensions and the like of each part of the soundproof structure. Since K is determined by substituting this into the equation (3), the resonance transmission frequency f can be obtained by substituting it into the equation (1) together with the M determined by the equation (2).
By designing the soundproof structure so that the resonance transmission frequency f obtained by the equation (1) is less than 500 Hz, noise in the frequency range that makes people uncomfortable is not felt, and it is suitable for use in a vehicle. It can be a soundproof structure.
It is more preferable that f is larger than 50 Hz.

FIG. 4 is a graph showing an example of adjusting the resonance transmission frequency f.
FIG. 4 shows the relationship between the frequency and the transmission loss for the soundproof structure A and the soundproof structure B. The soundproof structure A is an example of a soundproof structure in which the resonance transmission frequency f is in the range of 500 to 2000 Hz, and the soundproof structure B is an example of the soundproof structure of the present invention.
Both the soundproof structure A and the soundproof structure B are basically upward-sloping graphs in which the transmission loss increases as the frequency increases according to the mass law. Each has a region where the transmission loss becomes small, and the frequency corresponding to the minimum value of the valley is the resonance transmission frequency.
In soundproof structure A, the resonance transmission frequency f _A are within the range of 500～2000Hz, people are more likely to pass through noise feel uncomfortable frequency domain. On the other hand, in the soundproof structure B, the resonance transmission frequency f _B is in the range of less than 500 Hz, and noise in the frequency range of 500 to 2000 Hz, which is a frequency range that makes people uncomfortable, cannot be felt.
Further, in the soundproof structure B, the resonance transmission frequency f _B is larger than 50 Hz.

Subsequently, an example of a specific structure of the soundproof structure of the present invention will be described with reference to the drawings.
5 (a) is a perspective view schematically showing an example of a sound absorbing material constituting the soundproof structure of the present invention, and FIG. 5 (b) is a cross-sectional view taken along the line AA in FIG. 5 (a). ..
As shown in FIG. 5A, the sound absorbing material 10 has a non-through hole 30. As shown in FIG. 5B, the non-through hole 30 includes an introduction passage 31 that opens to the surface and a hollow portion 32 that is connected to the outside via the introduction passage 31.
The arrangement pattern of the non-through holes 30 of the sound absorbing material 10 shown in FIG. 5A is a staggered arrangement.
In the sound absorbing material 10, the introduction passage 31 has a columnar shape, and its diameter d is the equivalent circle diameter d of the introduction passage 31 (double-headed arrow d in FIG. 5B). The opening area SH of the introduction passage 31 is represented by d / 2 × d / 2 × π using the equivalent circle diameter d and the pi. The thickness of the introduction passage 31 is represented by t3 (double-headed arrow t3 in FIG. 5B).
The hollow portion 32 has a columnar shape, and its diameter dV is the equivalent circle diameter dV of the hollow portion 32 (double-headed arrow dV in FIG. 5B). The opening area SV of the hollow portion 32 is represented by dV / 2 × dV / 2 × π using the equivalent circle diameter dV and the pi. The thickness of the hollow portion 32 is represented by t2 (double-headed arrow t2 in FIG. 5B). The volume V of the hollow portion 32 is represented by SV × t2 using the opening area SV and the thickness t2.
The thickness of the sound absorbing material 10 is represented by T (double arrow T in FIG. 5B), and the thickness obtained by subtracting the thickness t3 of the introduction passage and the thickness t2 of the hollow portion from the thickness T of the sound absorbing material is t1. (Represented by the double-headed arrow t1 in FIG. 5B).

FIG. 6 is a perspective view schematically showing an example of the soundproof structure of the present invention.
FIG. 6 shows a soundproof structure 1 in which the soundproofing material 20 is provided so as to face the surface of the sound absorbing material 10 shown in FIG. Shown.
The sound insulating material 20 shown in FIG. 6 is a plate-shaped member, and has an area larger than the area of the surface on which the non-through hole 30 of the sound absorbing material 10 is opened. Therefore, the sound insulating material is present so as to face the opening of the non-through hole.
An air layer is provided between the sound absorbing material 10 and the sound insulating material 20, and the thickness of the air layer is represented by L (double-headed arrow L in FIG. 6).

Subsequently, a method for manufacturing the soundproof structure of the present invention will be described.
The sound absorbing material constituting the soundproof structure of the present invention forms, for example, a non-through hole having a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside via the introduction passage in the resin layer. It can be manufactured by doing so.
The method for forming the non-through hole in the resin layer is not particularly limited, but for example, the through hole may be manually formed in the resin layer using a tool such as a cutter.
Further, in the case of industrial mass production, a method of arranging a protrusion having a shape of an introduction passage and a hollow portion in a mold, forming a resin layer in the mold, and then removing the protrusion can be mentioned. An example of such a method will be described below.

First, a foamed resin is produced by a bead method in which foamable resin particles are filled in a mold formed by arranging a plurality of protrusions protruding inside and heated and foamed.
Next, non-through holes can be formed in the foamed resin by extracting the protrusions from the foamed resin.

In the above method, a foamed resin is produced by a bead method in which foamed resin particles are filled in a mold and foamed by a method such as steam heating.
Since a plurality of protrusions protruding inward are arranged in the mold, the foamed resin particles are not filled in the protrusions. Therefore, by extracting the protrusion from the foamed resin, a non-through hole corresponding to the shape of the protrusion can be formed in the foamed resin.

The material of the protrusion is not particularly limited, but it is desirable that at least a part thereof is made of a resin elastic body.
When at least a part of the protrusion is made of a resin elastic body, the protrusion is deformed when the protrusion is pulled out from the foamed resin, and the protrusion becomes easy to pull out.

Further, it is desirable that the protrusion has a substantially mushroom shape including a shaft portion and an umbrella portion, and the shaft portion is fixed to the mold.
When the protrusion has a substantially mushroom shape consisting of a shaft portion and an umbrella portion and the shaft portion is fixed to the mold, the foamed resin is formed with an introduction passage corresponding to the shape of the shaft portion to form the shape of the umbrella portion. Correspondingly, a hollow portion will be formed.

In the protrusion, it is desirable that the shaft portion is made of metal and the umbrella portion is made of the resin elastic body.
When the shaft of the protrusion is made of metal, the mechanical strength is high, so that the protrusion is less likely to be damaged by repeated use, the life of the protrusion can be maintained for a long time, and a highly durable mold can be obtained. ..
Further, when the umbrella portion of the protrusion is made of a resin elastic body, only the umbrella portion can be deformed, so that the protrusion can be easily pulled out from the foamed resin.

In the protrusions, it is desirable that the heat resistant temperature of the resin elastic body is higher than the temperature of heat foaming of the foamable resin particles.
If the heat-resistant temperature of the resin elastic body is higher than the heat-foaming temperature of the foamable resin particles in the bead method, the shape of the protrusions is less likely to be deformed by the heat when the foamable resin particles are foamed, and the durability against repeated use. Is obtained.
Since the heating temperature of the foamable resin particles in the bead method is 80 to 150 ° C., it is desirable that the heat resistant temperature of the resin elastic body is higher than the above temperature, specifically 100 to 180 ° C. , 155 to 180 ° C. is more desirable.

In the protrusions, it is desirable that the A hardness of the resin elastic body is 50 ° or less.
When the A hardness of the resin elastic body is 50 ° or less, the shape of the non-through hole can be sufficiently maintained during molding of the foamed resin by heat foaming, and when the protrusions are removed from the foamed resin after molding, the protrusions are formed. It deforms and becomes easy to pull out.
The A hardness means the hardness using a type A durometer measured in accordance with JIS K 6253-3 (2012).

In the protrusions, the resin elastic body is preferably a silicone resin or a silicone gel.
When the resin elastic body is a silicone resin or a silicone gel, the heat-resistant temperature of the resin elastic body is high, so that the shape of the protrusions is not easily deformed during heating and foaming, and the resin elastic body has high durability in repeated use. Further, it is easily deformed when the protrusions are pulled out from the foamed resin, and the protrusions can be easily pulled out from the foamed resin. Further, even when a protrusion having a shape that forms a Helmholtz resonance structure is used, the protrusion (capsule portion) forming the hollow portion is deformed so that it can pass through the introduction passage, so that the protrusion is formed of foamed resin. The protrusions can be removed from the foamed resin without damaging the Helmholtz resonance structure.

An example of a method for manufacturing a sound absorbing material in such a soundproof structure of the present invention will be described with reference to the drawings.

FIG. 7A is a perspective view schematically showing an example of a mold used in a method for manufacturing a sound absorbing material, and FIG. 7B is a sectional view taken along line BB of FIG. 7A.
In the method for manufacturing the sound absorbing material, first, a mold 50 as shown in FIG. 7A is prepared.
The mold 50 has a plurality of protrusions 60 inside the mold 50. As shown in FIG. 7B, the protrusion 60 has a substantially mushroom shape including a shaft portion 61 and an umbrella portion 62, and the shaft portion 61 is fixed to the mold 50.

FIG. 8 is an explanatory diagram schematically showing an example of a step of producing a foamed resin in a method for producing a sound absorbing material.
Next, as shown in FIG. 8, the foamed resin 70 is produced by a bead method in which the mold 50 is filled with foamable resin particles and heated and foamed.

9 (a), 9 (b), and 9 (c) are explanatory views schematically showing an example of a step of extracting protrusions from the foamed resin in a method for producing a sound absorbing material.
As shown in FIG. 9A, a protrusion 60 composed of a shaft portion 61 and an umbrella portion 62 is embedded in the foamed resin 70 after foam molding, and the umbrella portion 62 is made of a resin elastic body.
When the protrusion 60 is pulled out from the foamed resin 70, the umbrella portion 62 is deformed as shown in FIG. 9B. This is because the umbrella portion 62 is made of a resin elastic body and is easily deformed, and the foamed resin 70 is not deformed. The protrusion 60 can be pulled out from the foamed resin 70 by passing the umbrella portion 62 while deforming.
When the protrusion 60 is removed from the foamed resin 70, the shape of the umbrella portion 62 returns to its original shape as shown in FIG. 9C, and the space in which the protrusion 60 is buried becomes a non-through hole 30. Of the non-through holes 30, the shape of the introduction passage 31 that opens to the surface corresponds to the shape of the shaft portion 61, and the shape of the hollow portion 32 connected to the outside via the introduction passage 31 corresponds to the shape of the umbrella portion 62. do.
A sound absorbing material can be manufactured through such a process.

The soundproof structure of the present invention can be obtained by providing the sound insulating material so as to face the surface through which the non-penetrating holes of the sound absorbing material thus obtained are opened and to be separated by a predetermined distance with an air layer. ..
The sound insulating material may be provided by separately providing a connecting member for providing an air layer between the sound absorbing material and the sound insulating material, and the sound absorbing material and the sound insulating material are fixed at the place where the soundproof structure of the present invention is installed. Therefore, an air layer may be provided between the sound insulating material and the sound absorbing material.
In addition, when the place where the soundproof structure is installed is inside the vehicle, a part of the steel plate constituting the vehicle body is regarded as a soundproof material, and the soundproofing material is arranged so as to be separated from the steel plate by a predetermined distance to provide soundproofing inside the vehicle. You may try to get a structure.
In these examples, the sound absorbing material and the sound insulating material are arranged by adjusting the thickness L of the air layer between the sound insulating material and the sound absorbing material so that the resonance transmission frequency f obtained by the equation (1) is smaller than 500 Hz. To obtain a soundproof structure.

Subsequently, examples of vehicle parts and automobiles provided with the soundproof structure of the present invention will be described.
The vehicle component of the present invention is characterized by comprising the soundproof structure of the present invention.
Since the vehicle component of the present invention is excellent in soundproofing performance, it is excellent as a vehicle component.
Examples of vehicle parts provided with the soundproof structure of the present invention include a raising material and a luggage box.

The automobile of the present invention is characterized in that the soundproof structure of the present invention is arranged with the soundproofing material facing the road surface direction.
By arranging the sound insulating material of the present invention with the sound insulating material facing the road surface, it is possible to prevent the noise of the tire pattern noise transmitted from the road surface from being transmitted to the inside of the vehicle through the sound insulating structure.

An example in which the soundproof structure of the present invention is used as a vehicle component and an example of an automobile in which the soundproof structure of the present invention is arranged will be described with reference to FIGS. 10 (a) and 10 (b).
FIG. 10A is an explanatory view schematically showing an example of a portion where the soundproof structure of the present invention is arranged, and FIG. 10B is a portion of a region shown by a broken line portion in FIG. 10A. It is an enlarged view.
As shown in FIG. 10A, the automobile 100 includes a luggage room 103 behind the rear seat 101. As shown in FIG. 10B, a plate-shaped floor member 105 is laid under the luggage room 103, and an underfloor space 109 exists under the floor member 105.
A steel plate 20 that is a part of the body of the automobile 100 exists under the underfloor space 109, and the steel plate 20 serves as the sound insulation material 20 of the soundproof structure 1. A sound absorbing material 10 is provided on the sound insulating material 20 so that the surfaces having non-through holes face each other, and the soundproof structure 1 composed of the sound insulating material 20 and the sound absorbing material 10 is arranged in the automobile. The thickness L of the air layer between the sound insulating material 20 and the sound absorbing material 10 is adjusted so that the resonance transmission frequency f obtained by the equation (1) is smaller than 500 Hz.

Since the soundproof structure of the present invention has a Helmholtz resonance structure type non-through hole, it is excellent in soundproof performance in the frequency range of 500 to 2000 Hz. The soundproof structure of the present invention adjusts the shape of the non-through hole of the Helmholtz resonance structure, the thickness of the air layer between the sound absorbing material and the sound insulating material, and the like so that the resonance transmission frequency f becomes less than 500 Hz. Therefore, the frequency of the sound coming out of the soundproof structure deviates from the frequency range of 500 to 2000 Hz, which is unpleasant for humans. Therefore, it is possible to prevent noise in the frequency range of 500 to 2000 Hz, which makes people feel uncomfortable, from entering the vehicle interior, and it is possible to reduce that people in the vehicle interior feel uncomfortable.

(Example)
Specific examples for explaining the present invention in more detail will be shown below, but the present invention is not limited to these examples.

(Example 1)
(Making a protrusion unit)
Drill 10 holes (diameter 0.3 cm, depth 0.5 cm) so that the distance between adjacent side surfaces of the hollow parts adjacent to the surface of an aluminum plate with a thickness of 0.1 cm is 1.0 cm in a staggered arrangement. I prepared the aluminum substrate opened in.
Subsequently, an acrylic mold was prepared for producing a protrusion to be attached to the aluminum substrate.
The acrylic mold can be divided into two (one is a male mold and the other is a female mold), and inside [a cylinder with a diameter of 0.3 cm and a length of 1.5 cm as a shaft, and an umbrella part. The shape of a cylinder having a diameter of 1.0 cm and a length of 1.0 cm is a substantially mushroom shape in which the central axes of the cylinders are aligned and connected]. In order to obtain a cavity of this shape, the surface of each divided mold was machined. On the surfaces of the male and female molds, dents (cavities) corresponding to the shapes obtained by dividing the above-mentioned substantially mushroom shape into two along the length direction are formed, respectively.
0.5 part of the curing agent [Shin-Etsu Chemical Co., Ltd., CAT-RM] is mixed with 100 parts of the main agent of the silicone resin [Shin-Etsu Chemical Co., Ltd., KE-17], and vacuum defoaming (defoaming) is performed. After performing foaming time (20 minutes), it was poured into the cavities of the female mold and the female mold, and the female mold and the female mold were combined and fixed with a rubber band, and cured at 70 ° C. for 20 minutes. After curing, the female mold and the female mold are separated, the cured product is taken out, and burrs are removed to form a cylinder with a diameter of 1.0 cm and a length of 1.0 cm and a cylinder with a diameter of 0.3 cm and a length of 1.5 cm. A substantially mushroom-shaped molded body was obtained in which the central axes of each cylinder were aligned and connected. The A hardness of the resin elastic body constituting the molded body was 50 °.
Subsequently, a protrusion unit in which 10 protrusions were fixed on the aluminum substrate was prepared by inserting an end portion having a diameter of 0.3 cm of the molded body into a hole in the aluminum substrate to a depth of 0.5 cm. The protrusion was composed of a cylindrical shaft portion having a diameter of 0.3 cm and a length of 1.0 cm and a cylindrical umbrella portion having a diameter of 1.0 cm and a length of 1.0 cm.

(Effervescent resin foam)
The protrusion unit is attached to the die holder to prepare the mold, and the pre-foamed primary foam particles (made of polypropylene, average particle diameter 3.5 mm, foaming agent: carbon dioxide) are filled in the mold and foamed with heated steam. A plate-shaped perforated foamed resin was prepared by molding (143 ° C., 10 seconds), removing it from the mold, and drying it at 80 ° C. for 12 hours. At this time, the foaming ratio of the foamed resin was 30 times.

(Separation of protrusion unit)
After foam molding, the foamed resin and the protrusion unit were taken out in an integrated state, and the foamed resin and the protrusion unit were separated.
As a result, a sound absorbing material having a non-through hole formed of an introduction passage and a hollow portion was produced.

(Arrangement of sound insulation material)
A soundproof structure was obtained by arranging the steel plates at a distance of 0.5 cm so as to face the open surface of the non-through hole of the sound absorbing material.
The dimensions of this soundproof structure are ρm = 0.03 g / cm ³ , d = 0.3 cm, SH = 0.07 ^{cm 2} , t3 = 1.0 cm, dV = 1.0 cm, SV = 0.79 cm ² , V = 0.79 ^{cm 3} , t2 = 1.0 cm, T = 3.0 cm, t1 = 1.0 cm, L = 0.5 cm.

(Examples 2 and 3, Comparative Examples 1 and 2)
In Example 1, the dimensions of the protrusion unit to be used were changed, and the diameters of the shafts were set to 0.7 cm, 0.8 cm, 0.9 cm, and 1.0 cm, respectively, and the sound absorbing material was produced in the same manner as in Example 1. Obtained a soundproof structure. These soundproof structures have the same structure except that the equivalent circle diameter d of the introduction passage is different.
The structures of the soundproof structures of each Example and Comparative Example are summarized in Table 1 below.
In Comparative Example 2, since the introduction passage and the opening of the hollow portion have the same shape, a non-through hole other than the non-through hole of the Helmholtz resonance structure is formed.

[Calculation of the value of f in equation (1)]
For the soundproof structure of each Example and each Comparative Example, the value of f was calculated based on the equation (1).
The values of f in the formula (1) calculated for the soundproof structures of each example and each comparative example are summarized in Table 1 below.

[Actual measurement of resonance transmission frequency]
For the soundproof structures of each example and each comparative example, the resonance transmission frequency was actually measured by measuring the transmission loss while changing the frequency.
The transmission loss measurement was performed by an acoustic transmission loss test. The measurement was performed in accordance with JIS A 1416 "Measurement method of air noise blocking performance of building members in the laboratory".
FIG. 11 is an explanatory diagram schematically showing an outline of an acoustic transmission loss test for a soundproof structure.
FIG. 11 shows an acoustic transmission loss measuring device 80. The sound transmission loss measuring device 80 is provided with a sound source chamber 81 that generates sound from the speaker 83, and a sound receiving chamber 82 that receives sound through the soundproof structure 1 that is a test body. The sound source room 81 is provided with a sound source room side microphone 84, and the sound receiving room 82 is provided with a sound receiving room side microphone 85, and the sound pressure level L1 and the sound receiving room side microphone 85 measured by the sound source room side microphone 84 are provided. The sound pressure level L2 measured in 1 can be taken into the measuring device 86.
When measuring the sound absorption coefficient, the sound absorbing material and the sound insulating material (that is, the sound insulating structure) according to each Example and each Comparative Example are set between the sound source room and the sound receiving room shown in FIG. A sound (100 dB) was generated from the sound source, and the sound pressure level L1 in the sound source room and the sound pressure level L2 in the sound receiving room were measured. The measurement was performed in the frequency range of 100 to 2000 Hz.
(Calculation of transmission loss)
Transmittance: r = L2 / L1
It was determined from transmission loss (dB) = ₁₀ Log 10 (1 / r).
In the obtained transmission loss chart, the minimum value of the valley in the region where the transmission loss becomes small was defined as the resonance transmission frequency.
The resonance transmission frequencies actually measured for the soundproof structures of each example and each comparative example are summarized in Table 1 below.

12 (a), 12 (b) and 12 (c) are graphs showing the relationship between the frequency and the transmission loss in Examples 1, 2 and 3, respectively, and FIGS. 13 (a) and 13 (b). ) Are graphs showing the relationship between the frequency and the transmission loss in Comparative Examples 1 and 2, respectively.
Comparing these graphs, in Examples 1 to 3 under the condition satisfying the equation (1), the minimum value does not occur in the frequency range of 500 Hz to 2000 Hz, which is a frequency range that makes people uncomfortable. That is, it is understood that the sound transmission loss of the resonance transmission frequency component does not decrease in the range of 500 Hz to 2000 Hz.

1, 2 Soundproof structure 10 Sound absorbing material 20 Sound insulating material (steel plate)
30 Non-through hole 31 Introduction passage 32 Hollow part 50 Mold 60 Protrusion 61 Shaft part 62 Umbrella part 70 Foamed resin 80 Sound transmission loss measuring device 81 Sound source room 82 Sound receiving room 83 Speaker 84 Sound source room side microphone 85 Sound receiving room side microphone 86 Measuring device 100 Automobile 101 Rear seat 103 Luggage room 105 Floor member 109 Underfloor space

Claims (7)

Sound absorbing material with non-through holes and
A soundproof structure comprising a soundproofing material provided with a predetermined distance separated by an air layer so as to face the surface of the sound absorbing material through which the non-through hole is opened.
The non-through hole of the sound absorbing material has a Helmholtz resonance structure including an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage.
Let L be the thickness of the air layer.
The circle-equivalent diameter of the introduction passage is d, the opening area is SH, and the thickness is t3.
The circle-equivalent diameter of the hollow portion is dV, the opening area is SV, the volume is V, and the thickness is t2.
The density of the material portion other than the non-through hole portion of the sound absorbing material is ρm, and the thickness obtained by subtracting the thickness t3 of the introduction passage and the thickness t2 of the hollow portion from the thickness T of the sound absorbing material is t1.
The thickness of the air layer is L, the density of air is ρ0 = 0.001293 g / cm ³ , and the speed of sound is C = 34000 cm / sec.
t1, t2 and t3 are all 0.1 cm or more and 5.0 cm or less,
d is 0.3 cm or more and 3.0 cm or less,
dV is 0.4 cm or more and 17.1 cm or less,
In the range where L is larger than 0 cm
A soundproof structure characterized in that the following equation (1) holds for the resonance transmission frequency f (Hz).

{M in the formula (1) is represented by the following formula (2), and K is represented by the following formula (3).

[KH in the formula (3) is represented by the following formula (4), and KHA is represented by the following formula (5).

]} The soundproof structure according to claim 1, wherein the sound absorbing material is made of a resin or a fibrous material. The soundproof structure according to claim 2, wherein the resin is a foamed resin. The soundproof structure according to any one of claims 1 to 3, wherein the sound insulation material is a steel plate. The soundproof structure according to any one of claims 1 to 4, wherein f in the formula (1) is larger than 50 Hz. A vehicle component comprising the soundproof structure according to any one of claims 1 to 5. An automobile comprising the soundproofing structure according to any one of claims 1 to 5 in which the soundproofing material is arranged toward the road surface.

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