JP2020020137A - Noise reduction device - Google Patents

Abstract

To provide a noise reduction device which uses a balloon-type sound absorber utilizing membrane vibration type sound absorbing characteristics as a noise reduction medium, and significantly contributes to reduction of whole noise by effectively reducing a diffraction sound among the noises generated from a noise source.SOLUTION: In a noise reduction device comprising a sound insulation wall erected on a ground and the like and a balloon type sound absorber provided on a wall surface part of an upper end part of the sound insulation wall, the sound insulation wall is a single-layer wall structure; and the balloon type sound absorber is provided on a wall surface part on a noise source side of an upper end part of the sound insulation wall of the single-layer wall structure and/or on an opposite side of the noise source side; a resonance frequency in a state in which the inside is expanded by filling air is formed so as to have an appropriate surface density and air layer thickness for reducing construction noise and the like.SELECTED DRAWING: Figure 1

Description

  The present invention belongs to the technical field of a noise reduction device that reduces noise generated at a construction site or the like, and more specifically, reduces noise generated at a construction site or the like by using a membrane vibration type sound absorbing characteristic of a balloon type sound absorber. The present invention relates to a noise reduction device for reducing noise.

In general, noise generated at a construction site (construction noise) is dealt with by a sound insulation wall using a universal steel plate or a sound insulation sheet (sound insulation sheet).
The high frequency component of the construction noise can be expected to be reduced (sound reduction) by the sound insulation wall, but a low frequency band sound (hereinafter referred to as appropriate) included in so-called construction machine noise such as an idling sound of a generator or a heavy construction machine. Low frequency sounds are easily transmitted and diffracted, and it is difficult to effectively reduce them. This low-frequency sound is a major factor in complaints, such as rattling of private houses and discomfort to residents.

  In recent years, as a technique for reducing construction noise, Patent Literature 1 discloses a temporary scaffold 1 with a sound insulating material in which a sound insulating material 2 is attached to a temporary scaffold 1, wherein the sound insulating material 2 is a soundproof plate, a soundproof sheet, It consists of any one of the steel plates or a combination thereof, and is double-attached to the outer surface and the inner surface of the temporary scaffold 1. The back surface of the double sound insulating material 2 and the upper surface of the scaffold plate located at the upper end of the scaffold, A temporary scaffold 1 with a sound insulating material, to which a sound absorbing material 4 is attached, is disclosed (see claims 1, 2 and the like).

  According to the technology according to Patent Document 1, among the noises emitted from the noise source, the transmitted sound has a certain reduction effect due to the installation effect of the sound insulating material 2 and the sound absorbing material 4, but the diffraction effect due to the diffraction phenomenon. Diffraction sound circling above the temporary scaffold 1 has a problem that it cannot be expected to exhibit a sufficient reduction effect because it reaches the opposite side of the noise source.

  Patent Document 2 discloses a support member (frame scaffold) 11, a first soundproof material 21 and a second soundproof material 23 supported by the support member 11 so as to face each other with the support member 11 interposed therebetween; A plurality of bottomed tubular acoustic tubes 31 to 34 supported by the support member 11 so as to be disposed between the upper part of the first soundproofing member 21 and the upper part of the second soundproofing member 23; A soundproof device 10 is disclosed in which openings 31 to 34 are directed upward (see claim 1, FIG. 1 and the like).

  According to the technique according to Patent Document 2, among the noises emitted from the noise source, the transmitted sound has a considerable reduction effect due to the installation effect of the first soundproofing material 21 and the second soundproofing material 23, and the diffraction effect is high. A description is given that diffraction sound circling above the supporting member (framework scaffold) 11 due to a phenomenon is attenuated by the interference effect of the plurality of acoustic tubes 31 to 34 having the bottomed cylindrical shape, thereby improving the soundproofing effect. (See paragraphs [0007], [0008], etc.).

Patent No. 6149270 (Japanese Unexamined Patent Application Publication No. 2014-77315) JP-A-2017-111216

According to the technique disclosed in Patent Document 2, the transmitted sound and the diffracted sound emitted from the noise source both have a noise reduction effect, but have the following problems and are problems to be solved.
(1) It is necessary to prepare a large number of a plurality (for example, four) of acoustic tubes 31 to 34, which greatly increases the cost. In addition, it is necessary to arrange the plurality of types of acoustic tubes 31 to 34 regularly between the support members 11 as shown in FIG. 2 and the like, which is very troublesome. Therefore, there was a problem that economic efficiency and mounting workability were poor.
(2) Since the plurality of types of acoustic tubes 31 to 34 are all cylindrical with a bottom (see claim 1 and the like), rainwater is stored in the acoustic tubes 31 to 34 and cannot exhibit a predetermined effect. It was necessary to take measures against rainy weather, which was also very troublesome. Therefore, there is also a problem that the maintainability is poor.
(3) The target frequency for reducing noise is mainly from 250 to 500 Hz (see paragraph [0022], etc.). Regarding low-frequency sound that is frequently generated by so-called construction machine noise such as idling sound of a generator or heavy construction equipment. Did not expect much reduction effect. Therefore, there is a demand for a further improved noise reduction performance.

Accordingly, an object of the present invention is to use a balloon-type sound absorber that utilizes the sound absorption characteristics of a membrane vibration type as a noise reduction medium, and to effectively reduce the total noise by effectively reducing, among other noises, emitted from the noise source. An object of the present invention is to provide a noise reduction device which greatly contributes to reduction of noise.
In addition, an object of the present invention is to reduce the low-frequency noise that is frequently generated by so-called construction machine noise such as idling noise of a generator or heavy construction equipment, in particular, economical efficiency, installation workability, and maintenance. An object of the present invention is to provide a noise reduction device excellent in performance.
Furthermore, an object of the present invention is to provide a very reasonable and versatile noise reduction device, such as being able to easily attach a balloon-type sound absorber to an existing sound insulation wall (universal steel plate). is there.

As means for solving the problems of the background art, a noise reduction device according to the invention described in claim 1 is a sound insulation wall erected on the ground or the like, and a balloon type provided on a wall portion at an upper end portion of the sound insulation wall. A noise reduction device comprising a sound absorber,
The sound insulation wall has a single-layer wall structure,
The balloon-type sound absorber is provided on a noise source side and / or a wall surface opposite to the noise source side at an upper end portion of the sound insulating wall having the single-layer wall structure, and is filled with air and inflated. Is formed so as to have a surface density and an air layer thickness appropriate for reducing noise in construction and the like.

The noise reduction device according to the invention described in claim 2 is a noise reduction device including a sound insulation wall erected on the ground or the like and a balloon-type sound absorber provided on a wall portion at an upper end portion of the sound insulation wall,
The sound insulation wall is a multi-layer wall structure of two or more layers at predetermined intervals,
The balloon-type sound absorber is provided at an upper end portion between the respective wall portions of the sound insulation wall of the multi-layer wall structure, and a resonance frequency in a state in which the inside is filled with air and inflated has a noise of construction or the like. Characterized by having an appropriate areal density and an air layer thickness to reduce the thickness.

  According to a third aspect of the present invention, in the noise reduction device according to the first aspect, the inflated balloon-type sound absorbing body restraining member is provided so as to sandwich the balloon-type sound absorbing body with the wall surface in a sandwich shape. It is characterized by having been done.

  The invention described in claim 4 is the noise reduction device according to any one of claims 1 to 3, wherein the sound insulating wall is formed of a sound insulating panel such as a universal steel plate and / or a sound insulating sheet. And

  According to a fifth aspect of the present invention, in the noise reduction device according to any one of the first to fourth aspects, the sound insulation wall is provided on a support member formed by three-dimensionally assembling a single pipe member and / or a framed scaffold. It is characterized by being fixedly erected.

  According to a sixth aspect of the present invention, in the noise reduction device according to any one of the first to fifth aspects, the balloon-type sound absorber has a surface density and an air space appropriate for reducing noise such as construction. The resonance frequency for forming to have a thickness is about 40 to 300 Hz as a standard.

  According to a seventh aspect of the present invention, in the noise reduction device according to any one of the first to sixth aspects, the sound insulation wall is erected to surround a noise source such as a construction site. .

According to the noise reduction device of the present invention, the following effects can be obtained.
(1) Even for low-frequency noise, for which countermeasures were difficult with conventional noise reduction technology, a balloon-type sound absorber utilizing film-vibration-type sound absorption characteristics was used as a noise reduction medium, and more appropriate surface density and air By using a layer, noise can be reduced by utilizing the resonance vibration energy of the film surface.
(2) Since the resonance frequency can be tuned (adjusted) flexibly by changing parameters such as the surface density of the film and the thickness of the air layer, for example, sound in a targeted low frequency band can be reduced to some extent and effectively. Incidentally, the frequency at which construction noise can be effectively reduced is 40 to 300 Hz according to experiments and analysis by the present applicant.
(3) Of the noises emitted from the noise source, especially by effectively reducing the diffracted sound, it greatly contributes to the reduction of the whole noise. In particular, low-frequency noise, which is often generated by so-called construction machine noise such as idling noise of a generator or heavy construction equipment, can be effectively reduced.
(4) Since the balloon-type sound absorber can be easily attached to an existing sound insulation wall (universal steel plate), it is very rational and excellent in versatility.
(5) The noise reduction device according to the present invention is a balloon type at the upper end of a fence (sound insulation wall composed of a universal steel plate or the like) of about 3 m in height, which is often seen on a construction site every day. Since the noise reduction effect can be realized by simply extending the sound absorber, it is very excellent in versatility, and very excellent in economy, installation workability, and maintenance.

FIG. 2 is a side view illustrating the noise reduction device according to the first embodiment. FIG. 3 is a perspective view showing a balloon-type sound absorber used in the noise reduction device of the first embodiment (FIG. 1). FIG. 2 is a schematic plan view illustrating the noise reduction device according to the first embodiment. FIG. 7 is a side view illustrating a noise reduction device according to a second embodiment. It is a side view for demonstrating the Example of the case 3 and the case 5 (fixation of a gantry) of the full size test based on FIG. Equation 1 for obtaining the resonance frequency is shown. A is a schematic diagram showing the first embodiment, and B is a schematic diagram showing the second embodiment. 9 is a table summarizing test cases A to D of <Effect confirmation test 1>. It is a figure showing the sound receiving point regarding the said test cases A-D. 10 is a graph showing frequency characteristics at point E in FIG. 9 for test cases A to D, respectively. FIG. 10 is a contour diagram showing a sound pressure distribution in an 80 Hz band in FIG. 9. It is explanatory drawing which showed the test situation (test case 1-8) of <effect confirmation test 3 (full size test)>. It is a graph for confirming the sound reduction effect (noise reduction effect) about the test cases 1-5 among the said test cases 1-8. It is a graph for confirming a sound reduction effect (noise reduction effect) about test cases 6-8 among the test cases 1-8. It is a graph for confirming the sound-reducing effect in the test cases 1 and 8 about the test cases 7 and 8 at the point 5 m from the sound insulation wall. It is a graph for confirming the sound reduction effect at a point 10 m away from the sound insulation wall in the test cases 7 and 8 among the test cases 1 to 8. It is a graph for confirming the sound reduction effect in the test case 7 and 8 among the said test cases 1 to 8 at the point 20 m from the sound insulation wall.

The present invention has been made by the inventor of the present applicant to study and study the nature of the propagation of diffracted sound among the construction noises (transmitted sound and diffracted sound), and as a result, a universal steel plate normally used in a construction site has been studied. It is considered that if an inflated flexible non-permeable membrane material (balloon) is interposed in a sound insulation wall made of a material such as a material, a single resonance system in which an air layer acts as a spring is formed, and a resonance frequency based on the single resonance system is obtained. I started out focusing on the ceremony.
Therefore, in order to confirm the degree of the sound absorbing effect of the film material, a mock-up test using a 1/4 scale model, and a full-scale test were performed. A feeling that can be reduced was obtained.
That is, according to the present invention, a noise reduction device utilizing the sound absorption characteristics of a membrane vibration type using a balloon-type sound absorber can effectively reduce the construction noise (transmitted sound and diffraction sound), in particular, diffraction sound, and even low-frequency sound. It is based on technical ideas that can be reduced.

  Hereinafter, an embodiment of a noise reduction device according to the present invention will be described with reference to the drawings.

As shown in FIGS. 1 to 3, the noise reduction device 10 according to the first embodiment includes a sound insulation wall 1 erected on the ground 11 and the like, and a balloon-type sound absorber provided on a wall surface at an upper end portion of the sound insulation wall 1. Consists of two.
The sound insulation wall 1 has a single-layer wall structure.
In addition, the balloon-type sound absorber 2 is provided on a wall portion 1a on the noise source S side (and / or the side opposite to the noise source side) at the upper end of the sound insulating wall (universal steel plate) 1 having the single-layer wall structure, It is formed so that the resonance frequency in a state where the inside is filled with air and expanded is provided with an appropriate areal density and an air layer thickness for reducing noise such as construction work.

In the present embodiment, the sound insulating wall 1 has a single-layer wall structure in which a plurality of universal steel plates (for example, a height of about 3400 mm and a width of about 540 mm) are arranged in a line without any gap and formed in a wall shape.
In the present embodiment, the support member 9 for supporting the sound insulating wall (universal steel plate) 1 is formed by three-dimensionally assembling single pipe members 9a to 9e of a predetermined length on the ground 11 using orthogonal clamps 9f and free clamps 9g. The sound insulation wall 1 is constructed and is erected on the ground 11 via the support member 9. The present invention can be similarly implemented by using a framework scaffold instead of the support member 9.
The sound insulation wall 1 is not limited to the universal steel plate 1 but may be any member (sound insulation panel) that can be formed into a wall shape. Sound insulation sheets (soundproof sheets) can also be implemented. The height of the sound insulating wall 1 is, of course, not limited to about 3400 mm, and is not particularly limited, but a range of about 2000 to 5000 mm is practical.

In the present embodiment, the balloon-type sound absorber 2 is formed in a rectangular parallelepiped shape having a width (W) of about 1700 to 2500 mm, a height (H) of about 1000 mm, and a depth (D) of about 400 mm. The material is a soft vinyl chloride sheet. An air injection hole 2a is formed in the bottom portion.
In the present embodiment, the balloon-type sound absorber 2 having the above-described configuration is arranged such that the wall 1a at the upper end of the sound insulating wall 1 is spaced apart from the support member 9 (particularly, the single pipe member 9e) by an interval as shown in FIG. Are provided continuously in the direction perpendicular to the plane of the drawing.
Incidentally, the balloon-type sound absorber 2 according to the present embodiment is detachably mounted on the sound insulating wall (universal steel plate) 1 using a magic tape (registered trademark) or a double-sided tape.
The balloon-type sound absorber 2 is not limited to a soft vinyl chloride sheet, but can be suitably implemented as long as it is not breathable and has excellent flexibility (particularly, resin). Further, the form (shape and size) of the balloon-type sound absorber 2 is not limited to the above, and the design can be appropriately changed according to the required sound absorption performance and the like.

Specifically, the balloon-type sound absorber 2 has a resonance frequency of f (Hz), an air density of p (kg / m ³ ), a sound velocity of c (m / s), a balloon speed of the balloon-type sound absorber 2, The surface density of the side surface 2b of the sound absorbing body 2 opposite to the sound insulating wall 1 is m1 (kg / m ² ), the surface density of the sound insulating wall (universal steel plate) 1 is m2 (kg / m ² ), and the thickness of the air layer When the (depth dimension (D)) is L (m), the following equation 1 (see also FIG. 6)
f = (1 / 2π) {(pc ² / L) × (m1 + m2) / m1 · m2}
The surface density (m1) of the film and the thickness (L) of the air layer at which the resonance frequency determined by the above becomes 100 Hz or less.
By the way, the balloon-type sound absorber 2 according to the present embodiment implements the surface density m1 of the side surface 2b at 1.52 (kg / m ² ), and the surface density of both the upper surface 2c and the lower surface 2d is 4.34. (Kg / m ² ). The thickness (sheet thickness) of the side surface 2b is slightly less than 1.00 mm, whereas the upper surface 2c and the lower surface 2d are as thick as about 2.00 mm.

In this embodiment, as an example only, the surface density m1 of the side surface 2b of the balloon-type sound absorber 2 is set to 1.52 (kg / m ² ), and the surface density m2 of the sound insulation wall (universal steel plate) 1 is set. Is carried out at 1000 (kg / m ² ), and the thickness (the depth dimension (D)) of the air layer is carried out at the 400 mm (0.4 m). Since the air density p is 1.205 (kg / m ³ ) and the sound velocity c is 343.5 (m / s), the resonance frequency (f) ≒ 77.0 Hz. Incidentally, since the surface density m2 of the sound insulating wall 1 was very large, it was calculated as 1 / m2 ≒ 0.
This value is within the frequency range of 40 to 80 Hz, which is particularly likely to occur among the low-frequency sounds that are often generated by so-called construction machine noise such as idling sounds of generators and heavy construction equipment. Can be expected to be reduced significantly.

Incidentally, according to a test and analysis performed by the inventor of the present applicant, the areal density is about 0.43 to 4.34 kg / m ² , and the thickness of the balloon-type sound absorber ² is 0.35 to ² . When the air layer thickness in the inflated state (the depth dimension (D)) is about 100 mm to about 100 mm, the diffraction noise and, consequently, the low-frequency sound of the construction noise can be effectively reduced. ing.

As shown in FIG. 4, the noise reduction device 20 according to the second embodiment includes a sound insulation wall 1 erected on the ground 11 and the like, and a balloon-type sound absorber 2 provided on a wall portion at an upper end portion of the sound insulation wall 1. Become.
The sound insulation wall 1 has a multi-layer wall structure of two or more layers spaced at a predetermined interval.
The balloon-type sound absorber 2 is provided at an upper end portion between the respective wall portions of the sound insulation wall 1 having the multi-layer wall structure. It is formed so as to have an appropriate areal density and an air layer thickness to reduce the noise of the air.

Incidentally, in this embodiment, the universal steel plate 1 and the balloon-type sound absorbing body 2 which are the same (same shape and same size) as those of the above-mentioned embodiment 1 are used, and the sound insulation wall (universal steel plate) 1 according to this embodiment 2 In the embodiment, a double wall structure is formed in which two rows of front and rear walls are formed with a gap of slightly shorter than the depth dimension of the balloon-type sound absorber 2 (less than 40 cm). The balloon-type sound absorber 2 is fixed to the wall at the upper end of one of the sound insulation walls 1 in the front and rear two rows with a magic tape (registered trademark) or a double-sided tape, and is inflated. And the sound insulation walls 1 and 1 are provided so as to be in close contact with each other to some extent. The design of the space between the sound insulation walls 1 and 1 is appropriately changed according to the depth dimension (D) of the balloon-type sound absorber 2 to be used.
The support member 9 supporting the two rows of front and rear sound insulation walls 1 and 1 is constructed by appropriately changing the design as shown in FIG. 4 based on the support member 9 according to the first embodiment.

Due to the configuration of the noise reduction device 20 according to the second embodiment, when calculating the resonance frequency f (Hz) of the balloon-type sound absorber 2, m1 in the above equation 1 (see the paragraph [0024] and FIG. 6) is The surface density of the upper surface 2c of the balloon-type sound absorber ² corresponds to 4.34 (kg / m ² ), and m2 corresponds to the surface density of the lower surface 2d and 4.34 (kg / m ² ). , L correspond to the height H (1.0 m) of the balloon-type sound absorber 2.
Therefore, when the above numerical values of the second embodiment are substituted into the above equation 1, the air density p is 1.205 (kg / m ³ ) and the sound velocity c is 343.5 (m / s). Resonance frequency (f) ≒ 40.7 Hz.
This numerical value is within a range of a sound pressure level (frequency band) of 40 to 80 Hz, which is said to be particularly frequently generated among low-frequency sounds that are frequently generated by so-called construction machine noises such as idling sounds of generators and heavy construction machines. Therefore, the noise can be effectively reduced.
By the way, when the target resonance frequency is set to 300 Hz, as an example, when both m1 and m2 are performed at 0.43 (kg / m ² ) and L is set at 0.18 m, the above equation 1 is obtained. Since the base resonance frequency (f) is 305.1 Hz, an effective sound reduction of 300 Hz of the resonance frequency can be expected.

  Hereinafter, a confirmation test of the noise reduction effect performed mainly on Examples 1 and 2 will be described.

<Effect confirmation test 1>
The sound insulation wall 1 was examined under the conditions of a single-layer wall (Example 1) and a double wall (Example 2). FIG. 7A schematically illustrates the first embodiment, and FIG. 7B schematically illustrates the second embodiment.
In the case of a single-layer wall, the sound absorption characteristics of the membrane vibration type of the balloon-type sound absorber 2 attached to the wall of the sound insulation wall 1 were used. In the case of a double wall, the air layer of the balloon-type sound absorber 2 installed inside the sound insulating walls 1 and 1 acts as a spring to reduce the diffraction sound by the double film.
The resonance frequency (f) under each condition is as shown in the above equation 1 (see the paragraph [0024] and FIG. 6).
The resonance frequency (f) in the case of the single-layer wall according to FIG. 7A was calculated assuming that the density of the sound insulating wall 1 is sufficiently large. The frequency band to be attenuated was set to about 80 Hz based on the representative frequency characteristics of the noise of the construction machine (reference source: The Acoustical Society of Japan; prediction model of construction work “ASJ CN-Model 2007”).

(Anechoic chamber mock-up test)
A mock-up test using a 1/4 scale model was performed in an anechoic chamber in order to confirm the sound reduction effect of the measure combining the sound insulation wall 1 and the sound absorber (balloon sound absorber) 2.
The extension (overall width) of the universal steel plate 1 used as the sound insulation wall 1 was 21.6 m. The balloon-type sound absorber ² was made into a rectangular parallelepiped balloon when inflated with a soft vinyl chloride sheet (area density of 1.52 kg / m ² ) in consideration of ease of processing and area density.
FIG. 8 shows the test case, and FIG. 9 shows the positions of the sound receiving points where the amount of reduction was measured.
(Test results)
The test was performed using pink noise as the sound source. FIG. 10 shows the frequency characteristics at point E (see FIG. 9) of each case, and FIG. 11 shows the sound pressure distribution contour in the 80 Hz band.
From the results of FIG. 10, there was no significant change in the noise level (dBA) of each of the cases A to D. Comparing the single-layer wall cases A and B, in the adjusted resonance frequency band, the case B corresponding to the first embodiment has a noise reduction of 2.3 dB at the maximum in the 63-80 Hz band, and 1.5 dB on average. The effect was confirmed. Comparing the double-walled cases C and D, in case C, an increase in the sound pressure level (resonance phenomenon) was observed in the 80 Hz band, but in case D, a reduction of about 5.0 dB was confirmed in the 63 to 80 Hz band. .
From the results in FIG. 11, the sound pressure distribution after 20 m from the sound source is totally attenuated in the cases B and D in which the sound absorber is installed, as compared with the cases A and C in which the sound absorber (balloon type sound absorber 2) is not installed. A tendency (sound-reducing effect) was observed.

(Discussion)
Under the condition that the sound absorber (balloon-type sound absorber 2) was installed at the upper end (top) of the single-layer wall of Case B (Example 1 above), the effect of reducing the diffraction sound was recognized as described above.
In the case of the double wall of the case D (Example 2 above), it is generally expected that the universal steel plate 1 restricts the incident wave from the sound absorbing surface (upper end) of the sound absorbing body (balloon sound absorbing body 2) other than the sound absorbing surface (upper end). It is considered that the amount of reduction of the diffracted sound was improved in the different frequency bands.
(Task)
The sound reduction effect of a combination of a universal steel plate (sound insulation wall 1) and a sound absorber (balloon-type sound absorber 2) for diffraction sound of low-frequency noise generated during construction was confirmed by a laboratory test. As a result, in case B according to Example 1, a noise reduction effect of about 2.3 dB was confirmed. In Case D according to Example 2, a noise reduction effect of about 5.0 dB was confirmed.

<Effect confirmation test 2 (full-scale test)>
Next, the present applicant confirmed the noise reduction effect of the balloon-type sound absorber 2 using the full-sized sound insulation wall 1 outdoors. The test situation is shown in FIG.
The height of the sound insulation wall 1 was 3 m.
The balloon-type sound absorber 2 was formed in a rectangular parallelepiped shape having a width (W) of 1700 mm, a height (H) of 1000 mm, and a depth (D) of 500 mm. The material is a soft vinyl chloride sheet. An air injection hole (2a) is formed in the bottom part.
The film thickness (sheet thickness) and the surface density are 1.00 mm on the side surface 2b (see FIG. 1) and the upper surface 2c (see FIG. 2) among the six surfaces of the rectangular parallelepiped, and 1.32 kg / m ^2. The other four surfaces were formed at 0.5 mm and 0.66 kg / m ² .
The balloon-type sound absorber 2 having the above-described configuration is provided on the wall surface 1a at the upper end of the sound insulating wall 1 so as not to interfere with the support member 9 (particularly, the single pipe member 9e).
The air was blown and sucked by a hand-type blower through the air injection hole (2a).
The universal steel plate was temporarily fixed with Velcro (registered trademark), and then fixed with air pressure.

(Supplementary explanation of the experimental situation)
In this full-scale test, a sufficient space space could not be secured on the right side, and there was a possibility that the effect confirmation test might be adversely affected. Therefore, measures against reflected sound were taken with a soundproof sheet or a universal steel plate just in case.
Of the test cases 1 to 8, in the case of the case 3 and the case 5, the column of the sound insulating wall (fixed to the gantry) is as shown in FIG. 5 in order to enhance the adhesion (fixation) of the sound absorbing body to the universal steel plate. We devised various ideas. This is provided so that the constraining member 4 of the inflated balloon-type sound absorber 2 sandwiches the balloon-type sound absorber 2 with the wall surface portion 1a in a sandwich shape. Specifically, a single-tube member (restraining member) 4 of two upper and lower stages arranged in parallel with the sound insulating wall 1 (to extend in a direction perpendicular to the plane of FIG. 5) is attached to the vertical ground (vertical bar) 9a of the supporting member 9. The expanded sound absorber (balloon-type sound absorber 2) is supported by the single pipe members (supporting members) 3, 3 protruding horizontally from the upper end by the universal steel plate (sound insulation wall 1) and the single pipe member 4. This shows a test case in which the adhesion (fixing property) of the sound absorber to the universal steel plate is enhanced by sandwiching the sound absorber in a sandwich shape.
Cases 4 and 5 show test cases using soundproof sheets instead of universal steel plates.
The other test cases will not be described because it is determined that no particular explanation is necessary in view of the above <Effect confirmation test 1>.

(First test result)
FIG. 13 shows the results of the first test.
<When the sound insulation wall (1) is a universal steel plate (cases 1 to 3, see the upper graph in FIG. 13)>
It was found that when the sound absorbing body (2) was fixed by the gantry (single pipe member 4) as in the case 3, the noise reduction effect increased.
It was found that at the resonance frequency (80 Hz), the frequency was reduced by 3.6 dB, and the maximum volume reduction was reduced by 6.1 dB at 400 Hz.
It was found that the noise level (dBA) did not have a significant noise reduction effect (Cases 1 to 3: 68 dB).
<When the sound insulating wall (1) is a soundproof sheet (cases 4, 5, see the lower graph in FIG. 13)>
It was found that the resonance frequency (80 Hz) reduces the sound volume by 1.6 dB, and the maximum sound volume decreases by 3.1 dB at 125 Hz.
It was found that the noise level (dBA) did not have a significant sound reduction effect (Case 4, 5: 71 dB)
When the sound insulation wall is a sound insulation sheet (sound insulation sheet), the rigidity of the back surface is low, so that it is determined that the sound absorption effect by the membrane vibration is lower than in the cases 1 to 3 implemented with the universal steel plate.

(Second test result)
FIG. 14 shows the results of the second test.
By installing the sound absorber on the double wall of the case 8, it was found that the sound volume was reduced by 3.6 dB in the 100 Hz band, and the maximum sound reduction was reduced by 7.0 dB at 250 Hz.
With only the double wall of the case 7, the sound pressure level increases in the 80 Hz band. It is determined that a resonance phenomenon has occurred. However, in case 8 in which a sound absorber (balloon-type sound absorber 2) is installed in case 7, the increased sound pressure level is reduced. It can be seen that the effect of installing the sound absorber (balloon sound absorber 2) is remarkable only by paying attention to this point.

(Third test result)
The results of the third test are shown in FIGS.
In the case of a double wall, an increase in sound pressure level can be confirmed as a whole at 80 to 100 Hz as in the case of a room test in an anechoic chamber, but it is significantly reduced by installing a sound absorber (balloon sound absorber 2). I understood that.
In the band of 1 KHz or less, the sound absorbing body has an advantage in reducing the sound pressure level, but in a band higher than 1 KHz, it tends to work in the negative direction. In particular, it was found that the larger the distance from the sound insulation wall, the larger the distance.

  However, the noise to be measured is a so-called synthesized sound of the transmitted sound and the diffracted sound, and although it is impossible to identify how much the diffracted sound can be reduced, the balloon-type sound absorber 2 is installed on the sound insulating wall 1. Then, since the noise reduction effect is clearly recognized, it is considered that the present invention works particularly effectively in reducing the diffraction sound.

Although the embodiments have been described above with reference to the drawings, the present invention is not limited thereto, and includes a range of design changes and application variations usually performed by those skilled in the art without departing from the technical idea thereof. I will mention it just in case.
For example, in the first embodiment (see FIG. 1), the balloon-type sound absorber 2 is provided on the noise side S, and is implemented on the site such as a construction site. Instead of S, the noise side S may be provided on the side opposite to the noise side S, or the noise side S may be provided on the side opposite to the noise side S and used together (with a double balloon structure).
When the balloon-type sound absorber 2 is implemented with a double-layered wall structure as in Example 2 (see FIG. 4), in addition to providing the sound-insulating walls 1 between each other, the balloon-type sound absorber 2 is further provided in Example 1 (FIG. 4). Of course, it is also possible to adopt a double balloon structure provided on the noise side S as shown in FIG.
The noise reduction device according to the present invention is usually formed so as to surround a noise source such as a construction site, including or excluding an entrance portion, and is implemented on a sound insulation wall 1 in a certain range where noise countermeasures are required. Of course, only the balloon type sound absorber 2 may be partially installed.
Furthermore, in the present embodiment, the top surface of the balloon-type sound absorber 2 is implemented with the height almost equal to the top of the sound insulation wall 1, but the present invention is not limited to this, and the arrangement projects upward from the top of the sound insulation wall 1. May be implemented, or may be implemented at a position lower than the top end.
Incidentally, it is clear that the sound insulation wall 1 can be implemented with a triple-layer wall structure or more, and the sound reduction effect is further enhanced. However, it is not realistic in view of the occupied area of the noise reduction device itself and cost effectiveness.

1 sound insulation wall (universal steel plate)
Reference Signs List 1a Wall portion 2 Balloon type sound absorber 2a Air injection hole 2b Side surface 2c Upper surface 2d Lower surface 3 Single tube member (support member)
4 Single pipe member (restraint member)
S Noise source 9 Support member 9a-9e Single pipe member 9f Orthogonal clamp 9g Free clamp 10 Noise reduction device 11 Ground 20 Noise reduction device

Claims (7)

A noise reduction device comprising a sound insulation wall erected on the ground and the like, and a balloon-type sound absorber provided on a wall portion at an upper end of the sound insulation wall,
The sound insulation wall has a single-layer wall structure,
The balloon-type sound absorber is provided on a noise source side and / or a wall surface opposite to the noise source side at an upper end portion of the sound insulating wall having the single-layer wall structure, and is filled with air and inflated. The noise reduction device is characterized in that the resonance frequency of the noise reduction device is formed so as to have a surface density and an air layer thickness appropriate for reducing noise in construction or the like. A noise reduction device comprising a sound insulation wall erected on the ground and the like, and a balloon-type sound absorber provided on a wall portion at an upper end of the sound insulation wall,
The sound insulation wall is a multi-layer wall structure of two or more layers at predetermined intervals,
The balloon-type sound absorber is provided at an upper end portion between the respective wall portions of the sound insulation wall of the multi-layer wall structure, and a resonance frequency in a state in which the inside is filled with air and inflated has a noise of construction or the like. A noise reduction device characterized in that the noise reduction device is formed so as to have an appropriate surface density and an air layer thickness for reducing air pollution.   2. The noise reduction device according to claim 1, wherein the inflated balloon-type sound absorbing body restraining member is provided so as to sandwich the balloon-type sound absorbing body with the wall surface in a sandwich shape. 3.   The noise reduction device according to any one of claims 1 to 3, wherein the sound insulation wall is formed of a sound insulation panel such as a universal steel plate and / or a sound insulation sheet.   The noise according to any one of claims 1 to 4, wherein the sound insulation wall is fixedly installed on a support member formed by three-dimensionally assembling a single pipe member and / or a framed scaffold. Reduction device.   The resonance frequency for forming the balloon-type sound absorber so as to have an appropriate surface density and an air layer thickness for reducing noise in construction or the like is a standard of 40 to 300 Hz. The noise reduction device according to any one of claims 1 to 5.   The noise reduction device according to any one of claims 1 to 6, wherein the sound insulation wall is provided so as to surround a noise source such as a construction site.