WO2012147908A1

WO2012147908A1 - Sound attenuation system

Info

Publication number: WO2012147908A1
Application number: PCT/JP2012/061336
Authority: WO
Inventors: 良太木津; 裕道脇
Original assignee: 株式会社Ｉｈｉインフラシステム; ＮｅｘｔＩｎｎｏｖａｔｉｏｎ合同会社
Priority date: 2011-04-27
Filing date: 2012-04-27
Publication date: 2012-11-01
Also published as: JP2012237190A; JP2016026276A; JP5844679B2; JP6063547B2

Abstract

Louver units (22, 35) configured by providing a series of acute angle parts (21, 34) at the end (10a) of a pair of reflecting surfaces (10) having an attenuation property are configured in an adjoining manner with a specific interval therebetween so that the reflecting surfaces (10) are arranged facing each other, wherein incident sound entering from outside is caused to ingress without omission in a repeating reflection lane (32) at an angle of incidence in a specific range to cause multiple attenuated reflections between the reflecting surfaces (10) arranged facing the sound incident upon the reflecting surfaces (10) to effect sound attenuation. For example, an angle of inclination α of an inclined reflecting surface with respect to a virtual flat surface joining the ends of the reflecting surfaces is set to be greater than π/4 and less than π/2.

Description

Silencer system

The present invention relates to a silencer system applied as a noise countermeasure for backside sound absorbing plates, roads, railroads, buildings, buildings, etc., which are disposed, for example, under a girder of an elevated road.
This application claims priority on the basis of Japanese Patent Application No. 2011-1000020 filed in Japan on April 27, 2011, and is incorporated herein by reference. Is done.

A technology called a sound-absorbing plate has been developed for the purpose of reducing noise from the road, and the back-side sound-absorbing plate, which aims at measures against traffic noise in the vicinity of the elevated road by placing a sound-absorbing plate on the back side of the elevated road, Widely used in residential areas.

As disclosed in Patent Document 1, a conventional sound absorbing plate is disposed inside a panel member processed into a box shape including a panel portion having a design surface directed to the outside. A sound absorbing material is provided, and these are assembled like a unit, and a number of units can be connected to form a sound absorbing plate having a desired area. The panel portion has a large number of holes penetrating the front and back, and forms a so-called punching metal shape. The sound-absorbing material is composed of a glass fiber aggregate represented by so-called glass wool or a non-woven fabric made of polyester as disclosed in Patent Document 2, and spreads in a plane covering almost the entire area of the panel portion. It has become. The sound emitted from the noise source and incident on the sound absorbing plate is absorbed by a sound absorbing material disposed inside the panel member through a hole penetrating the panel portion and reduced.

In addition, the louver described in Patent Document 3 and Patent Document 4 is an alternative to the panel member. The louver is installed between the horizontal beams orthogonal to the horizontal beams on the lower surface of the horizontal beams arranged at appropriate intervals. A plurality are arranged in a line in the longitudinal direction with appropriate intervals. In the sound absorbing device including this type of decorative portion, the louver is intended to bring about designability in place of the design surface of the panel portion, and is improved in scenery as a public object.

Japanese Patent No. 2953989 Japanese Patent No. 3465622 Design Registration No. 1024537 Design Registration No. 1118521

In such a conventional sound absorbing device, the panel portion for holding the sound absorbing material and the louver instead of it are mainly intended to improve the design and have little effect of reducing sound such as sound absorbing effect, rather than incident sound. There was a problem that the sound was reflected to the sound source side. In particular, in the panel part of the panel type sound absorber, the incident sound reaches the sound absorbing material only in the part where the hole penetrating the front and back of the panel part is formed, and in the area other than the hole, the sound source side Will be reflected. This is also the case with louver type sound absorbers, where the reflection from the outer end surface of the louver or the reflected sound reflected from the side surface of the trapezoidal louver is directed outwards and does not reach the sound absorbing material and does not absorb sound. is there.

In addition, a panel material with a punching hole having a hole penetrating through the panel portion and a louver made of a material with a hole in the same manner have a lower strength than a material without a hole, and the drilling cost is low. There is a problem of becoming higher.

Furthermore, in the louver type sound absorbing device, in order to hide the sound absorbing material, the louver width and the louver interval have to be set to be approximately equal, and there is a problem that the sound absorption rate is lowered.

In addition, in the conventional sound absorbing device, the sound absorbing material that provides the sound absorbing effect is an indispensable element, but it is expensive, and since it is used in large quantities, the cost ratio to be tightened to the entire sound absorbing device is high, which increases the overall cost. Yes.

The present invention has been made in view of the above situation, and does not directly reflect incident sound to the sound source side, but absorbs all noise that is emitted from the sound source and propagates toward the sound absorbing device. It is an object of the present invention to provide a muffler system that makes it possible to enter a device without leakage and to mute the sound by significantly reducing the incident sound inside the device.

Another object of the present invention is to provide a muffler system that can attenuate and mute the sound pressure level of incident sound without using a sound absorbing material.

Furthermore, the present invention improves the cost increase due to the large amount of use of the sound absorbing material by making it possible to mute the sound by significantly reducing the incident sound without using the sound absorbing material at all or even in a small amount. The present invention is characterized by providing a silencing system that can significantly reduce the cost.

In the silencing system of the present invention, reflection surfaces that reflect and attenuate the incident sound as the sound is incident are arranged facing each other at an appropriate interval, and a plurality of reflection surfaces between which the reflected sound caused by the reflection is arranged are arranged. It is characterized by being configured to be reflected once.

In addition, an acute angle portion configured to have an inclined reflection surface that is widened in an acute angle shape from the front end side toward the rear end side is provided at the front end of the attenuation reflection plate disposed adjacently with an appropriate interval. It is a feature.

In addition, the inclination angle α of the inclined reflection surface from the virtual plane connecting the tips of the reflection surfaces is set to be larger than π / 4 and smaller than π / 2.

The distance W between the reflecting surfaces facing each other is not less than − (tan (2α) + cot (α)) h, where α is the inclination angle and h is the vertical distance from the base end to the tip of the acute angle portion. It is characterized by being set.

According to the silencing system to which the present invention is applied, the reflection surfaces having reflection attenuation properties with respect to the sound are arranged opposite to each other, and the incident sound emitted from the noise source is reflected a plurality of times between the reflection surfaces arranged opposite to each other. Since the high-order attenuation effect is exhibited by gradually attenuating, the incident sound can be silenced.

In addition, in a louver that is a structural member of a conventional sound absorbing device and improves the design, there is almost no effect of reducing the sound pressure level with respect to noise incident on the sound absorbing device, and rather the decorative surface of the louver facing the sound source side. However, there was a problem that the incident sound was reflected to the outside and the sound could not reach the sound absorbing material, but the reflection surface of the present invention was provided with an acute angle portion and formed into a louver shape, and the inclined reflection surface was inclined. According to the silencing system in which the range of the angle α is set within the range of π / 4 <α <π / 2 and the distance W between the reflecting surfaces is set to − (tan (2α) + cot (α)) h The incident sound can be taken into the sound absorbing device without leaking, and the taken incident sound can be attenuated by high-order attenuation by the repeated reflection attenuation effect. Furthermore, according to the silencing system of the present invention, incident light incident from the side can be reflected outward at the acute angle portion, and the surface of the acute angle portion and its periphery can be brightened. It is also possible to brighten the outside.

In addition, according to the silencer system of the present invention, it is possible to mute while eliminating the use of a sound-absorbing material made of glass fiber aggregate or polyester fiber aggregate, which has been indispensable for mass use in conventional sound absorbers. In addition, even when used in a small amount, it is possible to exhibit a sound pressure level reducing effect equal to or higher than that of the conventional one. Therefore, the use of the sound absorbing material, which is one of the main causes of the increase in the cost of the sound absorbing device, can be reduced to zero or a small amount, and the cost can be reduced.

Further, in a sound absorbing device to which the present invention in which the member constituting the reflecting surface is a louver type is applied, the strength as a beam can be improved by not providing a punching hole in the louver constituent member. Moreover, it is possible to set a wide louver width with respect to the louver interval, thereby expanding a blind spot area where the sound absorbing material can be hidden in visibility from the outside, and a wide exposed surface of the sound absorbing material can be set.

It should be noted that a muffler system as another example of the present invention has an input end through which sound can be incident from the outside, and the first reflection surface for reflecting the incident sound, that is, the incident sound is appropriately spaced with the incident sound. The repetitive reflection lane that can be reflected multiple times between the first reflecting surfaces that are arranged opposite to each other and reflected as a high-order incident sound, and the rear reflection side of the repetitive reflection lane. And a second reflection surface that reflects the incident sound that has reached the end side in a direction toward the input end side. In this silencing system, the above-described silencing system can be used in the repetitive reflection lane.

For example, the second reflecting surface is configured by connecting a plurality of unit shapes whose cross-sectional shapes are formed by appropriate curves or straight lines in the width direction. In such a second reflecting surface, each contact point forms a node, and a portion between adjacent nodes forms an abdomen, and the node is between the second reflecting surfaces or the second reflecting surface. It arrange | positions so that it may be located on the extended line with respect to the rear-end side of the position of between.

According to the sound absorbing system as described above, the first reflecting surfaces having reflection attenuation with respect to the sound are arranged to face each other, and the sound that has passed between the first reflecting surfaces on the rear end side of the first reflecting surfaces is the first. By providing a second reflection surface that reflects back and reflects the first reflection surface with an incident angle in an appropriate range toward the tip side of the reflection surface, the incident sound emitted from the noise source is reflected oppositely. A high-order attenuation effect can be exhibited by reflecting a plurality of times between the surfaces and gradually attenuating them. In addition, sound that has passed between the first reflecting surfaces without being reflected by the first reflecting surfaces is also reflected back toward the first reflecting surfaces, thereby repeatedly reflecting between the opposing first reflecting surfaces. With this configuration, the incident sound can be silenced.

In particular, when the cross-sectional shape of the second reflecting surface is configured as a parabola, when the sound entering from the outside reaches the second reflecting surface, almost all the sound is the focal point of the second reflecting surface forming the parabola. Therefore, the sound that has been reflected back and passed through the focal point is surely repeatedly reflected between the first reflecting surfaces, and a more reliable silencing effect can be obtained. In other words, in such a muffler system, compared to a sound absorbing device or the like that is mainly configured to absorb sound by the sound absorbing material, it is possible to absorb sound by using a small amount of sound absorbing material or without using any sound absorbing material. It becomes possible to mute.

FIG. 1 is a cross-sectional view showing a configuration of a silencing system according to an embodiment to which the present invention is applied, in which (A) shows a plurality of reflecting surfaces set in parallel in the depth direction. , (B) is a plurality of reflecting surfaces set to be inclined with respect to the depth direction and is set in parallel to each other, and (C) is adjacent among a plurality of reflecting surfaces set to be inclined with respect to the depth direction. It is a figure which shows one structure by which reflection surfaces were set non-parallel. 2A to 2I are enlarged sectional views showing the structure of the reflecting surface shown in FIG. FIGS. 3A to 3C are schematic diagrams showing how incident sound is reflected in the silencing system shown in each of FIGS. 1A to 1C. FIG. 4 is a cross-sectional view schematically showing an embodiment provided with an acute angle portion in the silencing system of the present invention. FIG. 4A is a pair of reflections back to back from the base end portion of the acute angle portion. (B) is formed such that the distance between a pair of back-to-back reflecting surfaces gradually increases from the base end of the acute angle portion toward the back, and (C) ) Is extended so that the distance between the pair of back-to-back reflecting surfaces is gradually reduced from the base end of the acute angle portion toward the back. FIGS. 5A to 5E are schematic cross-sectional views showing various modifications of the cross-sectional structure having the acute angle portion shown in FIG. FIG. 6 is a schematic view showing an embodiment of one unit constituting the silencing system of the present invention, where (A) is a cross-sectional view and (B) is a perspective view. FIGS. 7A to 7C are schematic views showing how the incident sound is reflected in the silencing system shown in each of FIGS. 4A to 4C. FIG. 8 (A) is a schematic diagram showing a state of reflection of incident sound in a silencing system in which a triangular portion set at an inner angle of 90 ° is provided at the tip of a reflecting surface arranged oppositely in parallel, FIG. 8 (B) Shows the state of reflection of incident sound in a silencing system in which a flat surface is provided at the tip of the reflecting surfaces arranged opposite to each other so that the distance between them gradually increases toward the back, and the overall shape is set to a substantially trapezoidal shape. It is a schematic diagram. FIG. 9 shows the exposure of the back surface in the relationship between the louver width and the arrangement pitch when a plurality of units formed in a louver shape with the inner angle of the triangular tip set to 90 ° are arranged in parallel and the blind spot width is 50 mm. It is a figure which shows the comparison of an area, (A) is what made the louver width 25, (B) is what made the louver width 50 mm. FIG. 10 is a cross-sectional view showing an example in which the pitch between the reflecting surfaces of the present invention is not constant. FIG. 11 is a cross-sectional view showing a modification of the acute angle portion of the present invention. FIG. 12 is a view as seen from the sound incident side of the muffler system showing an example in which the reflecting surface of the present invention is configured in a honeycomb shape. FIG. 13 is a cross-sectional view showing a modification of the silencing system of the present invention, and is a schematic view showing a state of reflection of incident sound, and a back-side reflecting surface having a parabolic cross section on the side opposite to the incident side is shown. In particular, (A) is a diagram showing a configuration of a silencing system of a type in which an acute angle portion is not formed at the tip, and (B) is a diagram of a silencing system of a type in which an acute angle portion is formed at the tip. It is a figure which shows a structure. FIG. 14 is a schematic view showing the dimensions of each part in a silencing system having an acute angle part on the tip side and a rear reflecting surface on the back side. FIG. 15 is a schematic diagram showing a state of reflection of incident sound in a silencing system in which the ratio of the louver width w to the louver distance W is set to the golden ratio. FIG. 16 shows an example in which the silencing system of the present invention is applied to a back surface sound absorbing device disposed on the back surface of a girder on an elevated road, and applied to a sound insulation wall and a sound insulation top plate disposed on a side wall portion of the elevated road. It is sectional drawing in the bridge-axis direction view which shows typically. FIG. 17 is a conceptual diagram showing a configuration of a grazing incidence sound absorption coefficient measurement test of a louver-type back surface sound absorbing device to which the sound deadening system of the present invention is applied. 18 is an enlarged cross-sectional view of the test body of FIG. 19A to 19C are cross-sectional views showing the configuration of the louver in FIG.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a silencing system according to an embodiment of the present invention will be described in detail with reference to the drawings. The silencing system of the present invention relates to a system that captures and silences noise generated from a noise source, and a silencing device and a sound absorbing device that include the silencing system. It is arranged along the bridge axis direction via a horizontal beam extending in the direction perpendicular to the bridge axis, and noise from vehicles traveling on the road under the overhead is reflected at the lower part of the girder and diffuses the noise around the road. The present invention is applied to a back surface sound absorbing device or the like for preventing this.

<1 First embodiment>
A first embodiment of the silencing system of the present invention will be described in detail with reference to FIGS. The silencing system 1 according to the first embodiment includes a plurality of reflecting surfaces 10 that allow incident external sound emitted from a noise source or the like and reflect the incident sound while attenuating the incident sound. The reflecting surfaces 10 are arranged to face each other with an appropriate interval between the reflecting surfaces 10. The arrangement of the reflecting surfaces 10 is set so that sound can enter the reflecting surface 10 and the reflected sound generated by the reflection can be reflected a plurality of times between the reflecting surfaces 10 opposed to each other.

It is important that the reflecting surface 10 has a property that the reflected sound with respect to the incident sound becomes smaller, that is, a reflection attenuation property for the sound, and the higher this reflection attenuation property is, the more preferable it is that the sound can be silenced more efficiently. That is, the reflective surface 10 can be configured by forming a material having reflection attenuation properties into a plate shape, a cylindrical shape, or the like. The silencing system 1 can be configured by disposing the reflecting surfaces 10 made of a material having reflection attenuation properties so as to face each other as shown in FIG. Specifically, in the silencing system 1 shown in FIG. 1, each of the front and back surfaces is formed with the reflecting surface 10 because the reflecting plate 11 having the reflecting surface 10 is made of a material having reflection attenuation (FIG. 2 ( (See A) and (B)).

In the silencing system 1 shown in FIG. 1A, each reflector 11 has a distance between the reflecting surfaces 10 facing each other from the front end (lower end in the figure) 10a side to the rear end (upper end in the figure) 10b side. It is set to be almost constant. And the reflective surface 10 of each reflector 11 is set perpendicular | vertical with respect to the virtual straight line which connects the front-end | tips 10a or rear-ends 10b. In the silencing system 1 shown in FIG. 1B, each reflector 11 has a distance between the reflecting surfaces 10 facing each other from the front end 10a side (lower end in the figure) to the rear end 10b side (upper end in the figure). The reflecting surfaces 10 of the respective reflecting plates 11 are set so as to be substantially constant, and are inclined at a predetermined angle with respect to a virtual straight line connecting the leading ends 10a or the trailing ends 10b. The In the silencing system 1 shown in FIG. 1C, each reflector 11 has a distance between the reflecting surfaces 10 facing each other from the front end 10a side (lower end in the figure) to the rear end 10b side (upper end in the figure). The pair of reflecting surfaces 10 that gradually reduce toward the rear end 10b and the pair of reflecting surfaces 10 that gradually increase toward the rear end 10b are alternately arranged and set. Here, the closer ends between the reflecting plates 11 in FIG. 1C are set with a finite interval, but not limited thereto, the ends are brought into contact with each other, It is also possible to configure it integrally.

The structures of the reflecting surface 10 and the reflecting plate 11 are not only composed of a material having reflection attenuation as shown in FIGS. 2A and 2B, but are also shown in FIG. As described above, a material having no reflection attenuation may be used as the core material 11c, and a surface layer 11d having reflection attenuation may be provided on the surface of the core material 11c to form a laminated structure. It is also possible to provide a reflection-damping surface 11d by applying a surface coating to the core material 11c. Here, FIG. 2A shows the reflecting surface 10 having a flat surface or a smooth cylindrical closed curved surface, and the reflection attenuating material of FIG. 2 shows a reflective surface 10 made of a porous material. Further, as shown in FIG. 2 (D), the reflecting surface 10 of the present invention has a pair of

thin surface materials

11e and 11e (reflecting surfaces) having reflection attenuation properties, and a pair of the

surface materials

11e and 11e. The reflective surface 10 can also be configured by interposing an intermediate material 11f having a corrugated cross section and fixing the

surface materials

11e and 11e to the intermediate material 11f. Further, as shown in FIG. 2E, the reflection surface 10 is configured by sandwiching the front and back surfaces of a flexible core material 11g such as rubber or sponge with

surface materials

11h and 11h having reflection attenuation properties. However, the sound pressure of the sound incident on the

surface materials

11h and 11h may be effectively attenuated by buffering the sound with the flexible core material 11g located in the middle. In addition, the reflecting surface 10 may be formed not only as a smooth surface, but also as shown in FIG. In this case, the sound wave passing through this vicinity, that is, the air vibration, is reduced in pressure by the concave portion and disturbed and attenuated. In addition, as shown in FIG. 2G, the reflecting surface 10 is made of a material having reflection attenuation, forms irregularities on the surface, and scatters sound waves that pass near the surface to attenuate the reflection. You may make it aim at improvement. Further, as shown in FIG. 2 (H), the reflecting surface 10 is a surface material in which a large number of hairs 11j for attenuating sound pressure are planted on the front and back surfaces of the core material 11i in the surface direction of the surface. It may be provided. As shown in FIG. 2 (I), the reflecting plate 11 constituting the reflecting surface 10 is provided with a large number of holes 11k penetrating the front and back, and the incident sound passes through the vicinity of the hole 11k. In addition, the sound pressure level may be reduced by reducing pressure or the like. In this case, in order to drill a large number of through holes 11k, a punching cost is required, which is higher than other examples.

The silencing system 1 of the present embodiment can take various configurations as described above, and the incident sound is reflected a plurality of times between the reflective surfaces 10 arranged to face each other, and the level of the input sound is increased each time the reflection is performed. Next, it is configured to be attenuated and muffled. For example, FIGS. 3A to 3C show how incident sound is reflected in the silencing system 1 shown in FIGS. 1A to 1C.

In the silencing system 1 configured as shown in FIG. 1A, sound incident in parallel to the reflecting surface 10 can pass from the front end 10a side to the rear end 10b side without being reflected by the reflecting surface 10. Therefore, when a sound absorbing material (not shown) such as a glass fiber aggregate such as glass wool or a polyester fiber aggregate is disposed on the rear end 10b side, incident sound can be directly absorbed by the sound absorbing material. In addition, as shown in FIG. 3A, in the muffler system 1 having the configuration of FIG. 1A, when sound is incident at an incident angle inclined with respect to the reflecting surface 10, the tip 10a side of the reflecting surface 10 is viewed. It is possible to reflect a plurality of times between the reflecting surfaces 10 facing each other toward the rear end 10b, and to gradually attenuate the level of the input sound according to the number of reflections. The output level Pn of the nth-order attenuation sound is given by Equation 1 where P0 is the initial input level of the incident sound, μ is the reflection attenuation coefficient specific to the reflecting surface 10 and n is the number of reflections. However, the reflection attenuation coefficient μ satisfies 0 <μ <1. Of course, the value of the reflection attenuation coefficient μ is preferably closer to 0 because sound can be attenuated with a smaller number of reflections.

In the silencing system 1 having the configuration shown in FIG. 1B, as shown in FIG. 3B, the front end 10a side to the rear end 10b side are substantially perpendicular to a virtual straight line connecting the front ends 10a of the reflecting surfaces 10. The sound incident on the reflecting surface 10, that is, the sound incident on the reflecting surface 10 with a certain inclination angle or more, is reflected between the reflecting surfaces 10 arranged facing each other from the front end 10 a side to the rear end 10 b side. It is possible to reflect the sound repeatedly, and to gradually attenuate the level of the input sound according to the number of reflections. Of course, the sound incident on the reflecting surface 10 in parallel can pass from the front end 10 a side to the rear end 10 b side without being reflected by the reflecting surface 10.

In the silencing system 1 configured as shown in FIG. 1 (C), as shown in FIG. 3 (C), the sound incident on the virtual straight line connecting the tips 10a of the reflecting surfaces 10 with a certain range of inclination angle is The reflection surface 10 is reflected several times between the reflection surfaces 10 facing from the front end 10a side to the rear end 10b side, and the return pitch is gradually shortened, and the input is performed according to the number of reflections. It is possible to gradually attenuate the sound level. Therefore, the number of reflections can be increased while the depth is shorter than the configuration of the reflecting surface 10 as shown in FIG. However, depending on the incident angle of the sound with respect to the inclination of the reflecting surface 10, the traveling direction of the higher-order reflected sound may reverse and return toward the tip 10a before sufficient reflection attenuation is achieved. So be careful. Of course, the sound that enters between the tip 10a portions of the reflecting surface 10 can pass from the tip 10a side to the rear end 10b side without being reflected by the reflecting surface 10.

As described above, in the silencing system 1 according to the present embodiment, the inclination angle of the reflecting surface 10 is considered in consideration of the relationship between the position of the sound source and the position where the silencing system 1 is disposed and the incident angle of the sound to be silenced. It can be said that it is preferable to define the configuration of In addition, it is possible to select a sound to be passed through without being attenuated and a sound to be attenuated at a higher order depending on the inclination angle of the reflecting surface 10 and the sound incident angle.

<2 Second Embodiment>
Next, a second embodiment of the silencing system of the present invention will be described in detail with reference to FIGS. The silencing system 20 of the second embodiment is configured by providing an acute angle portion 21 at the tips 10a of two reflecting surfaces 10 back to back. The inner angle of the tip 21a of the acute angle portion 21 is preferably set to less than 90 °. More preferably, it is set in a range of about 55 ° to 80 °. Here, it seems that the acute angle portion 21 has to be an acute angle, that is, less than 90 ° in terms of name, but does not necessarily have to be an acute angle. The angle of the corner portion constituting the acute angle portion 21 is desirably defined by a typical incident angle of incident sound, and it is important to set the incident sound from outside without leaking outside. . In addition, it is preferable that the surface of the acute angle portion 21 has a reflection attenuation property with respect to sound.

As shown in FIG. 4 (A), the silencing system 20 of the present embodiment has these reflecting surfaces 10 and a series of acute angle portions 21 integrally provided at the tips 10a of two reflecting surfaces 10 that are parallel to each other and back to back. A so-called louver-shaped louver unit 22 is formed. The plurality of louver units 22 are provided side by side with appropriate intervals so that the reflecting surfaces 10 are parallel to each other. Although the width between the louver units 22 will be described in detail later, the width is set to a predetermined distance or more defined according to the vertical distance from the tip 10a of the reflecting surface 10 to the tip 21a of the acute angle portion 21, the louver unit width, and the like. It is preferable. If the width between the louver units is set lower than the predetermined value, the sound incident parallel to the reflecting surface 10 with respect to the acute angle portion 21 may not be successfully taken into the silencing system 20 and reflected outside. Be careful.

As shown in FIG. 5 (A), the louver unit 22 can be formed into a sharp angle portion 21 by forming the tip shape of a solid member 22a made of a material having a reflection attenuation property to sound at a substantially acute angle. . In this case, the front and back surfaces of the members constituting the louver unit 22 become the reflecting surface 10. Further, as shown in FIG. 5B, a basic shape is formed using a solid member 22b made of a material that does not have reflection attenuation for sound as a core material, and a layer 22c having reflection attenuation is formed on the surface thereof. Thus, the louver unit 22 can also be configured. Further, as shown in FIG. 5C, a basic shape is formed by using a hollow member 22d made of a material that does not have reflection attenuation for sound as a core material, and a layer 22e having reflection attenuation on the surface thereof. The louver unit 22 can also be configured by forming. Of course, as shown in FIG. 5D, a pair of reflecting surfaces 10 and acute angle portions 21 are formed in series by a hollow member 22f made of a material having a reflection attenuation property to sound to constitute a louver unit 22. It is also possible. In addition, as shown in FIG. 5 (E), while a pair of reflecting surfaces 10 and acute angle portions 21 are formed in series by a hollow member 22g, the inner surface and the outer surface each have a reflection attenuation property for sound. By forming the layers 22h and 22i having the louver unit 22, it is possible to configure the louver unit 22 having a reflection attenuation property for sound inside and outside.

In addition, the louver unit 22 is formed of, for example, a material having a reflection attenuation property with respect to sound at an acute angle at each of the tips 10a of the pair of reflecting surfaces 10 having a cross-sectional shape as shown in FIG. The rear end portion 23 formed at a right angle to the reflecting surface 10 with the rear end 10b side of the reflecting surface 10 facing the inner side of the louver unit 22, The locking portion 24 can be formed by inclining the end portion of the rear end portion 23 toward the inner top portion of the acute angle portion 21 at an angle of less than 90 °. As shown in FIG. 6B, the louver unit 22 has a substantially the same cross-sectional shape and is extended by a predetermined length in the depth direction.

Further, the pair of reflecting surfaces 10 of the louver unit 22 of the present embodiment does not necessarily have to be parallel to each other. For example, as shown in FIG. 4B, the base end portion 21b of the acute angle portion 21 The distance between the reflecting surfaces 10 gradually increases from the position toward the rear end 10b, or the rear end 10b from the position of the base end portion 21b of the acute angle portion 21 as shown in FIG. It is also possible to configure such that the distance between the reflecting surfaces 10 gradually decreases toward the side. Of course, the configuration of the louver unit 22 is shown in FIGS. 5A to 5 which are shown as the cross-sectional structure of FIG. 4A even when the louver unit 22 has a cross-sectional shape as shown in FIGS. 4B and 4C. It is also possible to configure as shown in (E).

In each louver unit 22 shown in FIGS. 4 (A) to 4 (C), sound is incident on each acute angle portion 21 from a direction perpendicular to a virtual straight line connecting the tips 21a of each louver unit 22. FIGS. 7 (A) to 7 (C) show the state of reflection in the case of making them, respectively. As shown in FIG. 7, the sound incident on the acute angle portion 21 in this way is not bounced back to the external space on the incident side, and all the sounds are adjacent to each other between the louver units 22. The light is incident between the opposing reflecting surfaces 10 and gradually attenuated while being reflected a plurality of times between the reflecting surfaces 10. Of course, as shown in FIG. 7A, when the reflecting surfaces 10 facing each other are set in parallel, the reflected sound is reflected at a constant reflecting pitch toward the rear end 10b side of the reflecting surface 10. proceed. In the case where the distance between the reflecting surfaces 10 facing each other is set to be reduced toward the rear end 10b side, the reflected sound is reflected while the reflection sound is gradually reduced in reflection pitch as shown in FIG. 7B. It progresses toward the rear end 10b side. On the other hand, when the distance between the reflecting surfaces 10 facing each other is set to increase toward the rear end 10b, the reflected sound is reflected while the reflection pitch gradually increases as shown in FIG. 7C. It proceeds toward the rear end 10b side of the reflecting surface 10. Of course, if the number of reflections is sufficiently higher than the reflection attenuation performance indicated by the reflection attenuation coefficient μ of the reflection surface 10, the incident sound to the silencing system 20 of this embodiment is before the rear end 10b side is reached. Extremely attenuated and silenced. Further, since the louver unit 22 is provided with an acute angle portion 21 at the tip 21a, the surface of the acute angle portion 21 and its surroundings, and an elevated road can be reflected by reflecting light such as sunlight incident from the side by the acute angle portion 21. The back surface can be brightened, and reflected light can be guided to the road side under the elevated road, and the back surface of the elevated road and the road under the elevated road can be brightened.

Here, the acute angle portion 21 of the louver unit 22 shown in FIGS. 4 (A) to 4 (C) is set to be less than 90 °, but when it is set to an obtuse angle, for example, 90 °, FIG. As shown in FIG. 8 (A), the incident sound incident under the same conditions as described above is reflected by the inclined surface 121c of the tip 121a of the louver unit 122 set at an obtuse angle, and the reflected sound faces and is adjacent to the louver. It reaches the inclined surface 121c of the tip 121a of the unit 122 and is reflected, and the reflected sound is returned to the external space on the original incident side, and cannot be taken into the silencing system.

Further, when a substantially trapezoidal Uber unit 222 having a flat surface is formed by eliminating the acute angle portion 21 of the louver unit 22 shown in FIG. 4B, as shown in FIG. 8B, the flat surface 221a has a flat surface. All of the incident sound is reflected in the external space on the incident side, which contributes to a decrease in the muffling rate and the sound absorption rate. Of course, the incident sound is not limited to the sound incident perpendicularly to the flat surface 221a, and any sound incident from any direction is reflected to the external space. From this point of view, it is advantageous and preferable that the tip 10a of the reflecting surface 10 is provided with an acute angle portion 21 having an acute tip 21a. However, the angle of the tip 21a is not necessarily set to an acute angle. However, it may be obtuse, trapezoidal or arcuate for design reasons, processing, cost reasons, or the like.

Further, when the inner angle of the distal end 21a of the louver unit 22 is set to an appropriate value, when the proximal end portion 21b of the adjacent louver unit 22 is visually observed from the extension line of the inclined surface 21c of the distal end 21a of the louver unit 22. The gap between the base end portions 21b of the louver units 22 adjacent to each other, that is, the width between the louver units is a blind spot region. In this case, for example, even if a sound absorbing material (not shown) extending between the louver units 22 is disposed on the rear end 10b side (base end side) of the louver unit 22, the inclination angle of the inclined surface 21c of the louver unit 22 is determined. From a low angle position, the sound absorbing material disposed on the rear end 23 side enters the blind spot region and cannot be visually observed.

Here, without changing the size of the blind spot area, the improvement of the sound absorption rate of the sound absorbing device composed of the louver unit 22 to which the silencing system 20 of the present invention is applied can be achieved without changing the width between the louver units. This is achieved by reducing the arrangement pitch between the louver units 22. For example, as shown in FIGS. 9A and 9B, the width between the louver units is set to 50 mm, and the length from the front end 10a to the rear end 10b of the reflecting surface 10 is set to 50 mm. The inner angle of the tip portion 21a of the unit 22 is set to 90 °, the width of the louver unit 22 of one silencing system 20 is set to 25 mm (see FIG. 9A), and the width of the other louver unit 22 is set to 50 mm. Setting is made (see FIG. 9B). In this case, the arrangement pitch of the louver units 22 shown in FIG. 9A is 75 mm, and the arrangement pitch of the louver units 22 shown in FIG. 9B is 100 mm. Therefore, the total width between the louver units set in the 300 mm width, that is, the total blind spot area width, is 200 mm for the former (FIG. 9A) and the latter (FIG. 9B). Is 150 mm. Therefore, the former (FIG. 9A) has a wider area reaching the sound absorbing material, and the sound absorption rate is improved. Therefore, if the width of the louver unit 22 is set to be relatively narrow and the width between the louver units is set to be relatively wide as in the former (FIG. 9A), the sound absorbing effect is enhanced while maintaining the design. This is preferable.

<3 Modifications of First and Second Embodiments>
In the above description, the distance between the opposing reflecting surfaces 10 or the width between the louver units has been described as being constant. Of course, this distance is not necessarily constant. For example, as shown in FIG. 10, it is also possible to set so that the interval is gradually narrowed in the direction of the distance between the reflecting surfaces 10 or conversely widened. When set in this way, the sound that has been repeatedly reflected through the narrow area of the reflecting surface 10 and attenuated, and the sound that has been repeatedly reflected through the wide area of the reflecting surface 10 and attenuated, Sound that has passed through a narrowly spaced region has a higher attenuation level and can provide non-uniformity.

Further, for example, as shown in FIG. 11, the acute angle portion 21 includes an acute angle front end portion 21d that is widened toward the rear end 10b from the front end 10a, and a rear end portion from the rear end portion of the acute angle front end portion 21d to the rear end 10b. A parallel portion 21e extending in parallel toward the surface is formed. Further, an inclined surface 21f that is substantially parallel to the inclined surface on one side of the acute angle tip portion 21d is formed to extend from the rear end portion of the parallel portion 21e. That is, the acute angle portion 21 may have the inclined surface 21f formed in a step shape. That is, the section from the distal end 21a of the acute angle portion 21 to the proximal end, that is, the distal end portion 10a of the reflecting surface 10 does not have to have a linear cross-sectional shape, and is desired without departing from the gist of the present invention. It is possible to set to the shape.

Further, in the muffling system 20 of the present invention, it is only necessary that the reflecting surface 10 is provided so as to be opposed so that the incident sound that has entered can be repeatedly reflected and attenuated in the interior of the muffling system 20. In addition to the louver type as shown in FIG. 6 (B), for example, as shown in FIG. 12, it is provided in a honeycomb shape in which a large number of regular hexagonal tubes are arranged side by side without gaps. It may be a thing. Of course, the reflection surface 10 in this case corresponds to the inner surface of each regular hexagonal cylinder, and the tip of the reflective surface 10 forms an acute angle portion 21 by integrating the peripheral edges of adjacent regular hexagonal cylinders. The cross-sectional shape when cut from the front end side to the rear end side forms an acute angle. FIG. 12 is a schematic view seen from the front end side of the silencing system 20 configured in a honeycomb shape. Of course, the reflecting surfaces 10 facing each other here are formed in a honeycomb-like structure in which regular hexagonal cylinders are combined. It can be set to an arbitrary shape such as a shape or a cylindrical shape, and is not particularly limited.

<4 Third embodiment>
Next, a third embodiment of the silencing system of the present invention will be described in detail with reference to FIGS. 13 and 14. The silencing system 30 of the third embodiment can not only provide the acute angle portion 21 at the tip 10a of the reflecting surface 10, but can also have a rear reflecting surface on the rear end side as shown in FIG. . More specifically, the first reflecting surface 31 having an input end on the front end side through which sound can be incident from the outside and reflecting the incident sound with the incidence of sound with an incident angle within a predetermined range is appropriately spaced. Thus, they are arranged opposite to each other to form a repetitive reflection lane 32. The repetitive reflection lane 32 reflects the reflected sound generated by the reflection on the first reflecting surface 31 to the first reflecting surface 31 that is opposed to be disposed as a higher-order incident sound, and between the first reflecting surfaces 31 that are opposed to each other. Is set so that it can be reflected a plurality of times, and the reflection is attenuated gradually and higher. On the back side of the repetitive reflection lane 32, a second reflecting surface 33 is provided that reflects the incident sound that reaches the back side in a direction toward the input end side. The second reflecting surface 33 is provided so as to extend in a direction substantially orthogonal to the direction extending from the front end 31 a side to the rear end 31 b side of the first reflecting surface 31. The second reflecting surface 33 is preferably formed by connecting a plurality of curved shapes set in a concave shape from the front end 31a side to the rear end 31b side of the first reflecting surface 31 in the width direction. In other words, the second reflecting surface 33 is arranged at the rear end 31b side position of the first reflecting surface 31 with a plurality of first reflecting surfaces 31 with appropriate intervals between the continuous contact, that is, the node 33a and the curved abdomen 33b. Is disposed over the width direction in which is attached. More preferably, the positions of adjacent nodes 33 a are set such that one node 33 a is set at an intermediate position of a certain repetitive reflection lane 32, and the other (adjacent) node 33 a is one from the repetitive reflection lane 32. It is set at an intermediate position between the repeated reflection lanes 32 that are more than a distance. Further, the apex position of the abdomen 33b is preferably an intermediate position between the repeated reflection lanes 32 located between the repeated reflection lanes 32 where the nodes 33a are arranged. Desirably, the cross-sectional shape between adjacent node portions 33a of the second reflecting surface 33 is set to a parabolic shape, and the focal point is set to the center position of the repetitive reflection lane 32 where the abdominal portion 33b is located.

When the silencing system 30 is configured by the first reflecting surface 31 and the second reflecting surface 33 in this way, as shown in FIG. 13A, the first reflecting surface 31 is incident on the first reflecting surface 31 at an angle within a predetermined range from the outside. The sound that has been reflected is reflected by the first reflecting surface 31 and gradually progresses toward the rear end 31b while being repeatedly reflected between the repetitive reflection lanes 32. The light is reflected back to the tip 31 a side by the second reflecting surface 33 and led to another repeated reflection lane 32. Thus, the incident sound is silenced while being further repeatedly reflected between the first reflecting surfaces 31 facing each other in the repeated reflection lane 32 different from that at the time of entering, and further being attenuated by higher order.

Of course, as shown in FIG. 13B, in addition to the configuration of FIG. 13A, an acute angle portion 34 can be provided at the tip 31a of the pair of adjacent first reflecting surfaces 31. In the case where the acute angle portion 34 is provided, the sound that enters at an incident angle within a predetermined range has a significantly increased number of reflections, and an extremely high-order reflection attenuation effect can be obtained. As can be seen from FIG. 13B, all the sound that has entered the repetitive reflection lane 32 between the adjacent acute angle portions 34 in parallel with the first reflection surface 31 is reflected by the second reflection surface 33 having a parabolic cross section. All of the reflected sound passes through the focal point F of the parabola, enters another repeated reflection lane 32 having an acute angle portion 34, and enters between the opposing first reflecting surfaces 31 in the repeated reflection lane 32. While being repeatedly reflected, the reflection is attenuated by the higher order and the sound is muted. Further, when the acute angle portion 34 is provided, it is possible to brighten the surface of the acute angle portion, the periphery thereof, the back of the elevated road, etc. by reflecting light such as sunlight incident from the side by the acute angle portion 34. In addition, reflected light can be guided to the road side under the overpass, and the back side of the overpass and the road under the overpass can be brightened.

In order to more preferably configure the muffler system 30 described above, it is indispensable to follow a predetermined dimensional relationship, and a preferable setting will be described with reference to FIG. The silencing system 30 of the present embodiment includes a louver unit 35 in which a pair of first reflecting surfaces 31 are arranged in parallel at an interval w, and an acute angle portion 34 is provided in series at the tip 31a. That is, the width of the acute angle portion 34 is equal to w. The louver units 35 are arranged in parallel in the width direction with a width W. That is, the repetition width is equal to W. Here, the inclination angle of the acute angle reflection surface 34c from the virtual straight line connecting the distal ends 34a of the louver unit 35 is α, the vertical distance from the base end 34b of the acute angle portion 34 to the distal end 34a is h, and When the length from the front end 31a to the rear end 31b of the first reflecting surface 31, that is, the repetitive reflection portion length is H, the acute angle portion width w is given by the following equation (2).

Of course, the inclination angle α of the acute-angle reflecting surface 34c must satisfy the following equation 3 using an appropriate parameter κ. However, (pi) is a circumference and (kappa) satisfy | fills 0 <(kappa) <2.

In addition, among the sounds incident on the first reflecting surface 31 in parallel, all the sounds reflected by the acute angle portion 34 enter the first reflecting surface 31 under the condition that the louver unit width W is expressed by the following equation (4). Limited to meet. In other words, the louver unit interval W is preferably set so as to satisfy Equation 4.

The sound that travels between the adjacent louver units 35 set so as to satisfy such conditions, that is, while reflecting on the repetitive reflection lane 32, passes from the point where it is initially reflected by the acute angle portion 34 to the rear end 31 b side. When the number of reflections reflected by the first reflecting surface 31 before reaching the second reflecting surface 33 is n ^* , the following equation 5 is given. It is assumed that the total number of repeated reflections from the second reflection surface 33 until it is repeatedly reflected by another repeated reflection lane 32 and escapes to the outside is n.

Next, a specific example of the silencer system 30 that satisfies the above conditions will be shown, and the silencer will be described with reference to FIG. In this example, the value of the repetitive reflection coefficient μ was set to 0.9 while setting the inclination angle α of the acute angle reflection surface 34c = 54 °, the acute angle width w = 50, and the repetitive reflection length H = 150. The repetitive reflection width W was set to the minimum value obtained by substituting the value of the inclination angle α of the acute angle reflection surface 34c and the value of the acute angle width w into Equation 4.

In this case, the input sound P0 incident on the acute angle portion 34 in parallel to the first reflecting surface 31 has a total number of repeated reflections n of at least 20 as shown in FIG. It can be seen that the ratio of the next output sound P20 is about 10% or less. Of course, if the value of the repetitive reflection coefficient μ is set to a smaller value, the repetitive reflection attenuation effect, that is, the silencing effect becomes larger.

Note that the value of the parameter κ defining the inclination angle α of the acute angle reflection surface 34c in this example is κ = 1.2, and α = κ · π / 4 = 54 ° from Equation 2. Thus, it can be seen that under the above conditions, the ratio W / w of the louver unit interval to the acute angle width is just the golden ratio, which is excellent in design.

Further, although not set in detail under the above conditions, F in FIG. 14 is a parabola focal point which is a cross-sectional shape of the second reflecting surface 33, and P is a distance between the midpoint of the parabola and the focal point F, that is, a focal length. D is a distance between the connecting points of the second reflecting surface 33, that is, the distance between the node 33a and the rear end portion 31b of the first reflecting surface 31, and D is the midpoint of the parabola and the rear of the first reflecting surface 31. This is the distance from the end 31b. As can be seen from FIG. 15, when the focal length P is too long, the reflected sound reflected by the second reflecting surface 33 whose cross-sectional shape forms a parabolic shape has a smaller incident angle with respect to the first reflecting surface 31 and is repeatedly reflected. Since the number of times cannot be increased, it is preferable to set the focal length P short. When P <D is set, a part of the sound reflected by the second reflecting surface 33 escapes to the adjacent repetitive reflection lane 32 without entering the repetitive reflection lane 32 having the acute angle portion 34 and is less repetitive reflected. I get out to the outside with the number of times. In the case of P> D, the reflected sound reflected by the second reflecting surface 33 does not enter the repetitive reflection lane 32 having the acute angle portion 34, but enters the original repetitive reflection lane 32. Therefore, P = It is preferable to set P ≧ D close to D. Such poor incidence on the repetitive reflection lane 32 having the acute angle portion 34 of the reflected sound on the second reflecting surface 33 can be eliminated to some extent by adjusting the value of d.

The silencing system 30 of the present invention configured as described above can be applied to, for example, a silencing device that silences noise caused by incidence of noise emitted from a noise source, or a sound absorbing device that absorbs sound when used in combination with a sound absorbing material. Is possible. For example, as shown in FIG. 16, these silencers and sound absorbers can be provided on the side of the underside of an elevated girder 41 such as an expressway 40 so that a so-called back surface sound absorbing effect can be produced. In this case, even if the noise of the vehicle traveling on the road under the overhead is reflected by the inclined surface 34c constituting the tip portion 34a of the louver unit 35 of the sound absorbing device to which the present invention is applied, That is, it is possible to enter the repetitive reflection lane 32 constituted by the first reflecting surfaces 31 arranged opposite to each other so as not to return to the space on the incident side, that is, the road side under the elevated. Further, the sound incident on the repetitive reflection lane 32 is repeatedly reflected between the vertical side surfaces of adjacent louvers, and is absorbed by the sound absorbing material disposed on the rear end side of the louver unit 35 while being attenuated by reflection. Furthermore, since the louver unit 35 is provided with an acute angle portion 34 at the tip 34a, the surface of the acute angle portion 34, its periphery, and an elevated road can be reflected by reflecting light such as sunlight incident from the side by the acute angle portion 34. The back surface can be brightened, reflected light can be guided to the underpass road, and the overpass 40 and underpass can be made bright.

In addition, for the purpose of preventing noise emitted from a vehicle traveling on the elevated road from leaking out to the periphery of the elevated road, the noise-reducing wall formed by applying the noise reduction system 30 of the present invention to the side portion 42 of the elevated road. Can be arranged. The sound deadening wall includes a vertical portion 42a erected along the side portion 42 of the elevated road, and a ceiling portion 42b formed in series from the upper end of the vertical portion 42a. In this case, in addition to the negative effect of preventing the leakage of noise, it is possible to obtain a more positive effect that the noise itself is silenced.

In addition, a panel-like device or a box-like device to which the silence system 30 of the present invention is applied can be used as a countermeasure against noise generated around the engine or noise generated at a construction site. In the above description, the typical configuration of the silencing system 30 according to the present invention has been described. However, the present invention is not limited thereto, and various forms and configurations can be taken without departing from the gist of the present invention.

<5 Examples>
In this example, a test of the oblique incidence sound absorption coefficient was performed on a louver type sound absorbing device to which the sound deadening system of the present invention was applied and a test specimen for comparison, and the performance was compared. The test contents and test results are shown below.

<5-1. Test method for oblique incidence sound absorption coefficient>
The test method was carried out in accordance with the sound absorption performance test method specified in the 1995 construction technology evaluation system open call for participants “development of a sound absorbing plate with a large noise reduction effect”. The test room where the oblique incidence sound absorption coefficient was measured was a semi-anechoic room having a floor surface of 7 m × 8 m and a height of 6 m. The test body 51 is arranged and set as shown in FIG. 17, and 20 m ² or more is installed on the floor surface in the test room. An enlarged view of the test body 51 of FIG. 17 is shown in FIG. As shown in FIG. 18, the test body 51 is placed and set in the order of a corrugated steel plate 52, a sound absorbing material 53, and a louver 54. Further, as the louver 54, three types of test bodies (

louvers

54a, 54b, 54c) having different shapes as shown in FIG. 19 are used, and the arrangement pitch of the

louvers

54a, 54b, 54c is set to 100 mm, 125 mm, and 150 mm, respectively. And testing. However, the louver 54c in FIG. The louver 54a in (a) and the louver 54b in (b) have no holes formed in any reflecting surface, and only the louver 54c in (c) is punched and punched on all surfaces to obtain a porosity of 58. The hole 54d is formed in%. The length of each louver is set to 4000 mm. The test sound (Time-stretched Pulse) used in the signal compression method is adopted as the test sound emitted from the speaker 55 as a sound source. The measurement frequency range is a 1/3 octave band of 400 Hz to 4000 Hz. The microphone 56 is a precision-class sound level meter type 1/2 microphone. The incident angle and the arrangement of the sound source (speaker) 55 and the microphone 56 are set as shown in FIG. 17, and in the test, the incident angle of sound is 0 degree (vertical incidence), 15 degrees (π / 12), 30 degrees ( The reflected sound was measured under four conditions of π / 6) and 45 degrees (π / 4). The speaker 55 and the microphone 56 are arranged with reference to a floor surface that is a rigid wall surface. Under conditions other than the incident angle of 0 degree, the speaker 55 and the microphone 56 were arranged on the circumference having a radius of 3 m from the rigid wall surface. Under the condition of an incident angle of 0 degree, the distance between the speaker 55 and the rigid wall surface is 3 m, and the distance between the microphone 56 and the rigid wall surface is 2.5 m. When the test body is installed on a rigid wall surface or when the test body 51 is installed with a back air layer of 60 cm, the speaker 55 and the microphone 56 are arranged with reference to the rigid wall surface as in the test under the rigid wall condition. .

<5-2. How to find the oblique incidence sound absorption coefficient α (θ)>
Before and after the test body 51 is installed, the reflected sound component observed in the same measurement arrangement is extracted from each waveform. The power spectrum of the reflected sound obtained under the rigid wall condition at the sound incident angle θ is Pr (f), and the power spectrum of the reflected sound obtained under the test specimen installation condition is Ps (f). Here, the sound absorption coefficient of the test body 51 with respect to the incident angle θ is defined as the following formula 6 by the energy ratio of the sound lost before and after installation of the test body.

<5-3. Calculation method of average oblique incidence sound absorption coefficient αRA>
The average spectrum proposed by the Acoustical Society of Japan as the frequency characteristics of road traffic noise (Tachibana et al. “Energy-Based Road Noise Prediction Method”, Journal of Acoustical Society of Japan, Vol. 50, No. 3 (1994)) The average oblique incident sound absorption coefficient was calculated using the oblique incident sound absorption coefficient measurement results of each specimen (see Table 1).

Here, LAi: A characteristic spectrum (dB) of road traffic noise at the i-th frequency
αi: Oblique Incidence Absorption Rate at i-th Frequency, Incidence Angle θ The oblique incident sound absorption coefficient αRA (θ) for road traffic noise is obtained by the following equation (7).

The arithmetic average of the oblique incident sound absorption coefficient αRA (θ) obtained at each angle is calculated, and the result is defined as the average oblique incident sound absorption coefficient αRA. Based on this definition, the sound absorption coefficient αRA is as shown in Equation 8.

<5-4. Calculation method and display method of measurement results>
The measurement results are summarized in Table 2. As can be seen from Table 2, it can be seen that those having an acute angle portion and those not having an acute angle portion have a higher sound absorption rate. However, although it seems that there is not much difference between the louver 54b of (b) and the louver 54c of (c), in fact, the louver 54b of (b) is a reflection surface without holes. The louver 54c of (c) has holes 54d over the entire surface, and it is considered that the sound transmitted through the holes 54d is absorbed by the sound absorbing material 53, and there is no hole. When the louver 54c of (c) is configured, it is necessary to note that the sound incident on the flat surface corresponding to the upper side of the trapezoid is reflected to the sound source side and the sound absorption rate is extremely reduced. . Therefore, it can be seen that the amount of the sound incident on the acute angle portion reflected toward the side surface portion of the louver and returned to the outside is reduced as compared with the case where the acute angle portion is not provided. This is also clear from the comparison of the louver 54a of (a) and the louver 54b of (b), with respect to the louver 54a of (a) in which the internal angle of the acute angle portion is set to be less than 90 ° (about 60 °). The louver 54b of (b) set to 90 ° is inferior in sound absorption rate.

1 silencer system, 10 reflective surface, 11 reflector, 20 silencer system, 21 acute angle part, 22 louver unit, 30 silencer system, 31 first reflective surface, 32 repetitive reflection lane, 33 second reflective surface, 33a node, 33b abdomen, 34 sharp corners, 35 louver units

Claims

Reflecting surfaces that reflect the incident sound while attenuating the incident sound are arranged to be opposed to each other with an appropriate interval, and the reflected sound generated by the reflection is reflected a plurality of times between the reflecting surfaces arranged to face each other. Silencer system characterized by that.
It is characterized in that an acute angle portion configured to have an inclined reflection surface that is widened in an acute angle shape from the front end side toward the rear end side is provided at the front end of the attenuation reflection plate that is arranged adjacently with an appropriate interval. The muffler system according to claim 1.
3. The silencing system according to claim 2, wherein an inclination angle α of the inclined reflecting surface from a virtual plane connecting between the tips of the reflecting surfaces is set to be larger than π / 4 and smaller than π / 2.
The distance W between the reflecting surfaces facing each other is not less than − (tan (2α) + cot (α)) h, where α is the inclination angle and h is the vertical distance from the base end to the tip of the acute angle portion. The muffler system according to claim 2 or 3, wherein the muffler system is set.
Furthermore, the incident sound that is disposed on the rear end side of the repetitive reflection lane and is reflected on the rear end side of the reflection surface is reflected back and reflected in the direction toward the sound input side. The silencing system according to claim 1, further comprising a reflective surface.
The second reflecting surface is formed by connecting a plurality of unit shapes whose cross-sectional shape is formed by an appropriate curve or straight line in the width direction, each connecting contact forms a node, and between adjacent nodes The middle part forms the abdomen,
The silencing system according to claim 5, wherein the node portion is located on an extension line with respect to a rear end side of the position between the second reflecting surfaces or between the second reflecting surfaces.