JPH0765495B2 - Exhaust sound absorber and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust sound absorber that exhibits an excellent sound absorbing effect particularly against aircraft noise, and a manufacturing method thereof.

(Prior Art) Conventionally, as a sound absorber used by being inserted into a ventilation duct having a relatively short length which penetrates a wall of a room, a sound absorber shown in FIG.
As shown, the duct a has an air passage c that directly penetrates the porous sound absorbing body b, and is of a splitter type or a cell type, or although not shown, the air passage is bent into an L shape. Things are known.

(Problems to be solved by the invention) The effect of these sound absorbers as sound absorbers for aircraft noise was examined, and the maximum noise level of aircraft noise was 50.
It is 8 dB generated around 0 Hz, and a large noise reduction effect is necessary for this, but it is about 15 dB for the splitter type and about 8 dB for the cell type, and the noise level is 70 dB or 7 dB.
It is desired to bring it down to only about 7 dB and approach the conversation interruption level (SIL) of 40 dB as the target level.

(Means for Solving the Problems) The present invention significantly reduces the noise level at 500 Hz, which is the center of aircraft noise, and its vicinity, and reduces the noise level to 20%.
It is about dB or more and about 25 dB, and the muffling effect in a wide range of frequencies from 100 Hz to 5000 Hz is significantly larger than the conventional muffling effect, and further toward the 5000 Hz, the muffling effect, that is, the muffling volume gradually increases, Thus, unlike a sound deadening curve that peaks in a certain frequency range and falls at higher frequencies, it provides a sound absorber for the interior of a ventilation opening that exhibits excellent sound absorbing characteristics that maintains a rising curve. In a sound absorbing body for exhaust gas, which is installed in a ventilation hole penetrating the air ventilation passage in a porous molded body having the size and shape of the above, in the air ventilation passage, the air introduction side ventilation passage part and the air outlet side ventilation passage The exhaust sound absorbing body is formed by arranging the parts at mutually different positions, and forming an intermediate air passage part between the inlet side and outlet side air passage parts in the enlarged space air passage part.

Furthermore, the present invention provides the above-mentioned sound absorbing body of the present invention, that is, a method of manufacturing the sound absorbing body having an air ventilation path having a different cross-sectional area at each portion, which can be easily and inexpensively manufactured. At least one sound absorbing plate having at least one side air passage formed therein, at least one sound absorbing plate having an enlarged space air passage portion formed therein, and the air introduction side passage having a phase shifted from each other. It is characterized in that at least one sound absorbing plate in which at least one part is bored is sequentially superposed and configured as one body with each other.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings. 1 to 3 show an exhaust sound absorber according to an embodiment of the present invention.
(1) shows a porous molded body such as synthetic resin foam mat, inorganic fiber, and synthetic resin fiber mat, which is to be installed by fitting it into a ventilation hole such as a ventilation hole formed in a wall of a house or a building. It has a suitable shape and size. The porous molded body (1)
Is the same as the conventional exhaust sound absorber in that it has an air vent passage (2) penetrating in the front-rear direction, but according to the present invention, the air vent passage (2) is configured as follows. To do. That is, the air inlet side air passage portion (2a) and the air outlet side air passage portion (2b) of the air air passage are positioned relative to each other, and in the illustrated embodiment, they are positioned above and below each other. And the intermediate space passage portion (2c) between both the air passage portions (a) and (2b) is formed in the expanded space air passage portion. Thus, in the sound absorbing body of the present invention, the air introduction port side air passage portion (2a) is directed toward the indoor side during use, and the air outlet port side air passage portion (2b) is provided.
Is installed so that it faces the outside. The air introduction port side air passage (2a) has a long and short cross section, and the air introduction port (3)
Is opened at the lower rear surface of the sound absorber, and the air outlet port side air passage portion (2b) has a long and short cross section, and the air outlet port (4)
Is open at the upper front of the sound absorber, and both ventilation passages (2a)
The opening areas of the inlet (3) and the outlet (4) of (2b) were the same. The length of the sound absorber in the front-rear direction is approximately the same as the thickness of the wall of the chamber in which it is to be installed, and it is a rectangular parallelepiped of a size suitable for fitting into a rectangular ventilation vent provided on the wall. . As shown in FIG. 4, the sound absorber is installed in a return air ventilation port (6) provided in a wall (5) of the chamber, and an exhaust duct (having a rectangular cross section) tightly fitted to the ventilation port (6). It was housed tightly via 7). In the drawing, (8) is a protection frame plate attached to a wall (5) that protects the exposed surface of the sound absorbing body facing the indoor side by hermetically sealing the gap between the duct (7) and the sound absorbing body, (9)
Is a ventilation fan provided on the outside of the sound absorbing body on the front side of the sound absorber, and (10) is a protective casing having an openable and closeable door-type lid on the front surface surrounding the outer periphery of the sound absorbing body, which is airtightly attached to the outer surface of the wall (5). .

Thus, in the sound absorbing body of the present invention, the air to be exhausted from the interior of the room due to the operation of the fan (9) flows from the air introducing port (3) to the air introducing port side ventilation passage part (2a) and the intermediate ventilation passage part (2c). ),
Exhaust is performed through the air outlet side air passage portion (2b) to the outside through the outlet port (4).

On the other hand, when aircraft noise enters through the outlet port (4) and enters the intermediate air passage portion (2c) of the expanded space in front of it through the air outlet port side air passage portion (2b), it absorbs sound in front of it. Sound is absorbed by the wall, and its reflection and dispersion are repeated to generate an interference effect, and sound is absorbed by the surrounding sound absorbing wall, so that the air located in the lower part, which is displaced from the outlet port (4) located in the upper part, is located. The noise leaking into the room from the inlet (3) through the inlet-side air passage (2a) is significantly reduced. The silencing effect is greater as the positions of the inlet port (3) and the outlet port (4) are displaced, that is, the greater the distance is.

It is difficult to manufacture the sound absorber of the present invention in which the air ventilation passages (2) partially differ in cross-sectional shape, size, and position as described above, at a time by molding with a normal mold, internal drawing, etc. Is. Next, a description will be given of an embodiment of the high production method of the present invention, which is easy to manufacture.

According to the usual method, a large number of porous molded sound absorbing plates of the same thickness and shape are formed by pressure formation, or a band-shaped porous molded sheet of the same thickness is created and cut into a certain size to obtain the same thickness. , Prepare and prepare a large number of shaped porous molded plates. In order to manufacture the sound absorbing body having the structure of the above-mentioned embodiment, four porous molded sound absorbing plates (11) are prepared, and one of them is
In the lower part of it, there is a rectangular hole (2
a ') is formed by hollowing out and two of them have a large square hole (2c) for the expanded space ventilation path (2c) in the center.
c ') is internally formed, and for the remaining one sheet, a rectangular hole (2b') for the air outlet side air passage (2b) is internally formed at the upper part thereof, and these punched sound absorbing plates (11 2) are polymerized and bound to each other via an adhesive to obtain the above-mentioned laminated sound absorbing body of the present invention.

6 and 7 show another embodiment of the present invention. In this embodiment, the air introduction port side air passage portion (2a) is provided at the center of the back surface of the sound absorber, and the air outlet port side air passage portion (2b) is provided at the upper and lower parts of the front surface of the sound absorber. In this case, the opening area of each of the outlets (4) and (4) of the two ventilation passages (2b) and (2b) is equal to the opening of the inlet (3) of one ventilation passage (2a). It is preferable to design it so that the total opening area thereof is equal to the opening area of the introduction port (3) by halving the area.

The sound absorbing body is a cardboard box or a container (12) made of synthetic resin or the like, whose entire circumferential surface is protected by a cardboard box. When the sound absorbing body is installed, as shown in FIG. ) The outer surface of the exhaust duct (7) was airtightly fitted to the inner peripheral surface of the exhaust duct (7). The method of manufacturing the sound absorbing body is substantially the same as the method of manufacturing the sound absorbing body of the above-described embodiment. That is, as shown in FIG. 9, two porous sound absorbing plates (11) each having a rectangular hole (2a ') for an inlet-side air passage (2a) punched out in the central part and an enlarged space in the central part. Two porous sound absorbing plates (11) punched out with a large rectangular hole (2c ') for the ventilation part (2c), and rectangular holes for the outlet side ventilation passage part (2b) at the upper and lower parts respectively. The point that two porous sound absorbing plates (11) formed by punching out (2b ') are prepared are
Although substantially the same as the above-mentioned embodiment, in order to form a sound absorbing body of a laminated body in which these sound absorbing plates (11) are integrally polymerized, a corrugated cardboard container capable of accommodating and accommodating the laminated body of these sound absorbing plates (11) exactly 12) A rectangular hole (13) of the same diameter is previously formed in the central portion corresponding to the inlet (3) of the inlet side air passage portion (2a).
Is prepared, and the sound absorbing plate (11) is sequentially polymerized in the container (12) to obtain a sound absorbing body of the present invention in which these laminated bodies are integrally held by the container (12). To be In this case, the use of an adhesive for adhering the sound absorbing plates (10) to each other can be omitted, and the production can be further facilitated.

Thus, the hole (13) of the container (12) has the inlet (3).
Allows the inflow of air. In the above-described example of manufacturing the laminated sound absorbing body, the punched sound absorbing plates having the same thickness are used, but one or a plurality of punched sound absorbing plates having different thicknesses may be combined and stacked as needed to be manufactured. In addition, adjustments such as the length of each air passage part (2a), (2b) and the size of the expanded space air passage part (2c) can be freely adjusted by selecting the number of sheets used and the thickness of the sound absorbing plate. The sound absorber of can be manufactured. Incidentally, the allowance device (12) has a lid plate piece (12a) that can be bent, as shown in the tenth drawing, and the opening part of the punching sound absorbing plate (11) is closed after being housed. If
Furthermore, the solid holding of the sound absorbing body can be ensured. In this case, the lid plate piece (12a) has a hole (14) of the same shape and the same size at a position corresponding to the outlet ports (4) and (4) of the air outlet port side air passage portions (2b) and (2b). ) Allow ventilation even when the lid piece (12a) formed with (14) is closed. In drawings (15)
Is the folding margin provided at the tip of the lid piece (12a), (16) (16)
Indicates a fold provided on the rim of the body of the container (12), which facilitates closing of the lid piece (12a) and improves the airtightness of the peripheral edge of the container opening, and the fold (16 )
A lid piece may be polymerized and attached to the (16) via a paste.

Next, a more concrete example and its muffling effect will be further clarified.

The sound absorbing body of the present invention having the structure shown in FIG. 6 is made of glass fiber having an average fiber diameter of 2 μm, and has a density of 24 kg / m ³ and a thickness of 20 mm.
Molded glass wool matte of 20mm thick, 240 x 24
Prepare a 0mm porous sound absorbing board, two of each, 60m in the center
m × 200 mm rectangular air inlet side hole for air passage part punched out, 200 mm × 200 mm for expanded space air passage part hole punched, 30 mm × 200 m for top and bottom
A rectangular m-shaped hole for the air outlet side air passage was punched out, and the punched sound-absorbing plates thus obtained were sequentially fitted tightly into the container with a lid made of corrugated cardboard and laminated to form a lid. Then, the laminated sound absorber of the present invention was produced. The container is
I used the one of approximately 240 mm x 240 mm x 130 (depth). As shown in Fig. 8, this was installed in the exhaust duct on the wall of the building, and the effect of silencing the noise from the fighter (altitude 370 m) was tested. The muffling characteristics are shown in FIG. For comparison, the same size of the splitter type sound absorber was installed in the same manner, and the sound deadening effect was tested. The measurement result is as shown in the graph of FIG. The sound deadening characteristic curve I is based on the sound absorbing body of the present invention, and the same curve C is based on the conventional splitter type sound absorbing body. As is clear from this graph, in the conventional sound absorber, the noise elimination volume of 500 Hz is only 14 dB, but in the case of the noise absorber of the present invention, the noise elimination volume of 26 dB is 85 dB at 500 Hz. Obtained a significant noise reduction effect of less than 60 dB. Furthermore, the sound deadening effect against noise up to 5000 Hz increases as the frequency increases in the sound absorber of the present invention, and shows a sound deadening volume of 40 dB or more, while it does not drop during this period, the conventional sound absorber has a noise of around 2000 Hz. The noise reduction peaked at about 24 dB, and at higher frequencies, the muffling effect decreased as the frequency increased. As the sound absorbing material, it is preferable to use glass fibers having an average fiber diameter of 10 μm or less. Further, a plurality of air inlet port side air passage portions (2a) may be provided. In addition, ventilation path (2a) (2
When a plurality of each of b) are provided, they may be arranged on the left and right.

(Effects of the Invention) As described above, according to the present invention, in the exhaust sound absorber, the air vent passage provided through the sound absorbing molded body is formed with the intermediate portion in the enlarged space vent passage portion, and the air at both ends thereof is The inlet side air passage part and the air outlet side air passage part are provided so that they are located at mutually opposite positions, so a noise reduction effect centered on 500 Hz is provided.
It can be remarkably improved as compared with the conventional sound absorber, and the sound deadening effect increases with the increase of the frequency from 100 to 5000 Hz, and in particular, it has the effect of producing a sound deadening level of 20 dB or more from around 500 Hz to 5000 Hz.

[Brief description of drawings]

1 to 3 show a sound absorber according to an embodiment of the present invention, FIG. 1 is a cutaway side view thereof, FIG. 2 is a sectional view taken along line II-II, and FIG. 3 is a perspective view. Figure 4 is a cutaway side view of the installed state,
FIG. 5 is an exploded plan view of the sound absorbing body of one example of the method for manufacturing the sound absorbing body of the present invention, FIG. 6 is a cutaway side view of the sound absorbing body of another embodiment, FIG. 7 is a perspective view thereof, and FIG. FIG. 9 is a cutaway side view of the installed state, FIG. 9 is an exploded plan view of the sound absorbing body of another example of the sound absorbing body manufacturing method of the invention, and FIG. 10 is a perspective view of the sound absorbing body container of the invention. FIG. 11 is a graph showing sound deadening characteristics of the sound absorbing body of the present invention and the conventional sound absorbing body, and FIGS. 12A and 12B are perspective views of the conventional sound absorbing body. (1) …… Sound absorption molded body (2) …… Air ventilation passage (2a) …… Air inlet side ventilation passage (2b) …… Air introduction outlet side ventilation passage (2c) …… Enlarged space ventilation passage (3) …… Air inlet (4) …… Air outlet

Claims (3)

[Claims] 1. A sound absorbing body for exhaust having a porous molded body having a predetermined size and shape, which is installed in a ventilation port penetrating an air ventilation passage, wherein an air introduction port side ventilation passage portion and an air of the air ventilation passage are provided. An exhaust sound absorber, which is provided with the outlet port side ventilation passage portion being located at a position relative to each other and in which an intermediate ventilation passage portion between both inlet side and outlet port side ventilation passage portions is formed in the expanded space ventilation passage portion. 2. An air inlet of the air inlet side of the air passage is provided at the center of the back surface of the sound absorber, and the outlet of the air outlet side air passage is located above and below the front surface of the sound absorber. The sound absorber for exhaust gas according to claim 1, wherein two sound absorbers are provided in each. 3. A phase of at least one sound absorbing plate having at least one air introduction side air passage formed therein, at least one sound absorbing plate having an enlarged space air passage formed therein, and the air introduction side passage. A method for manufacturing an exhaust sound absorbing body, characterized in that at least one sound absorbing plate in which at least one air outlet side air passage portion is formed by being displaced is sequentially superposed and configured as one body.