JPH01302060A - Resonance silencer for air feed duct - Google Patents

Abstract

PURPOSE:To effectively attenuate a low frequency band noise without special installation space by incorporating one or more resonance cylinders with one open end and the other closed end having a depth of approx. 1/4 of the wavelength of a noise to b attenuated in a linear duct. CONSTITUTION:A duct 2 has a square section, cylindrical wall plates 4, 4 of the same material separately disposed oppositely to right and left side faces 5, 5 over all inner height of the duct in a longitudinally linear midway section in such a manner that the upper and lower end sides are secured to the upper and lower inner faces 6, 7 of the duct and cylindrical bottom plates 8, 8 are secured at predetermined positions between the wall plates 4, 4 and the right and left side faces 5, 5, and resultantly resonance cylinders 3, 3 with one open end and the other closed end surrounded thereby to be brought into plane contact with the open ends 10, 10 of an air passage 9 of the duct. The cylinders 3, 3 are secured by positioning the plates 8, 8 to form the depth of the cylinders 1/4 of the wavelength of a noise to be attenuated. Thus, a low frequency noise can be effectively attenuated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air supply tact in a building air conditioner or various smoke evacuation devices, etc., and particularly relates to a resonance muffling device for an air supply duct for reducing noise. Regarding.

[Prior art] Conventionally, in order to muffle the noise of an air supply duct, the inner peripheral surface of the duct was lined with a porous sound-absorbing material such as glass wool (lined duct), or the cross section was abruptly cut in the middle of the duct. A cavity-type muffler was used, which attenuates the transmitted sound toward the front of the duct by expanding the noise wave and reflecting the noise wave at the discontinuous boundary surface.

[Problems to be Solved by the Invention] However, although the porous sound-absorbing material of the lining duct can reduce high-frequency noise, it has a low sound-absorbing effect on low-frequency noise and cannot eliminate it.

On the other hand, in order to improve the attenuation value of a cavity-type silencer, the cross-sectional enlargement ratio must be increased (for example, several tens of times).
There are cases where it cannot be adopted due to bulk and space constraints.

The present invention has been made in view of the problems of such conventional tact noise reduction devices, and it eliminates the need for special installation space and is capable of extremely effectively attenuating low-frequency noise. The purpose is to provide a silencer.

[Means for Solving the Problems] The present invention has been completed in accordance with the above-mentioned object. That is, the present invention provides one or more of the following: The object of the present invention is to provide a resonance muffling device for an air supply duct, characterized in that a resonant tube is built into a straight tact, and the open end of the resonator tube is brought into contact with the air passage of the tact.

[Function] As a result of the above, in the resonant silencing device for the air supply duct of the present invention, the air inside the resonator cylinder resonates with the target frequency component of the noise propagating inside the duct, and the sound is violently generated in a mode with a peak at the open end of the resonator cylinder. It vibrates and converts the sound energy into frictional heat, dissipating it and attenuating the noise.

[Embodiment] Hereinafter, embodiments will be explained with reference to the drawings (first, see Figs. 1 and 2). In these figures, 1 is a resonance silencing device for an air supply duct according to the present invention, and the silencing device of this embodiment is The device 1 includes two resonance cylinders 3, 3 built into the left and right sides of a straight duct 2.

The tact 2 in this example is made of a galvanized iron plate and has a rectangular cross section, and in the straight section midway in the longitudinal direction, a cylindrical wall plate 4.4 of the same quality extends over the entire inner height of the tact and is spaced apart on the left and right inner surfaces 5, 5. The cylinder bottom plate 8.8 is placed at a predetermined position between the cylinder wall plates 4, 4 and the left and right inner surfaces 5, 5 of the tactile unit, while the upper and lower end sides thereof are respectively fixed to the upper and lower inner surfaces 6.7 of the tactile member. As a result, the resonator cylinders 3, 3, which are open at one end and closed at the other end, surrounding these are connected to the air passage 9 of the duct at the open end 10.
It has 2 built-in 10 interviews.

Note that the resonance tube 3 can resonate if its open end 10 faces the air passage 9 of the duct, and it is not necessarily necessary to arrange it parallel to the longitudinal direction of the duct.
1 is a curved portion formed at the other end of the cylindrical wall plate 4°4;
On the other hand, as shown in the figure, three sides of the cylinder wall of the resonance cylinder 3, upper, lower and outer sides, also serve as the outer peripheral iron plate 12 of the duct.

By positioning and fixing the cylinder bottom plate 8.8, the resonance cylinders 3, 3 are formed to have a cylinder depth of 1/4 of the target noise wavelength to be reduced. Both are 223 cm (in the figure, the target noise frequency is 75H2).

Note that the target noise wavelength is set to 1, for example, one with a large noise component in general for the rotational sound of an air supply fan, or a target wavelength depending on individual issues such as resonance of surrounding components (not shown) of the duct. .

Next, explaining the embodiment shown in FIG. 3, the silencer of this embodiment has two built-in resonant tubes 3.3 on the left and right sides as in the above embodiment, or in addition, two resonant cylinders 3. A resonant bottleneck 13 having a length of 1 and sound absorbing wall parts 15, 15 filled with glass wool 14, 14 are arranged side by side.

That is, each cylinder wall plate 4', 4' of the left and right resonance cylinders 3, 3 in this example is as follows.
Approximately one-fourth of the target noise wavelength further from the fixed position of the cylinder bottom plate 8
By extending the length, the length of the flat plate excluding the curved portions 11 and 11 (22 in the figure) is approximately half of the target noise wavelength, and as a result, the cylinder wall plates 4°, 4° As a result, the air passage of the duct is narrowed, and a resonant bottleneck 13 having a length of approximately one-half of the target noise wavelength is formed between the left and right resonant parts.

Then, the air in the resonance bottle 13 resonates with the target frequency component of the noise propagated within the tact, and vibrates violently with a moat with peaks at the front and rear ends of the bottle, converting the sound energy into frictional heat, similar to the resonance tube 3.3. The noise is attenuated by converting and dissipating it. In addition, even when such resonant bottlenecks are installed in parallel, their target noise wavelengths are not necessarily made to match those of the resonant cylinder, but may also be made different to attenuate a plurality of noise components, or slightly shifted. The resonance may be bimodal.

On the other hand, as a result of extending the cylinder wall plates 4° and 4° beyond the fixed position of the cylinder bottom plate 8.8, a hollow portion 16.16 is formed between the cylinder wall plate extensions and the outer peripheral iron plate 12 of the duct. In one example, glass wool 14, 14 (
or sound absorbing material such as rock wool), and punched metal with a large number of through holes 17 in the 4° extension of the cylinder wall plate 4 is used to suppress noise in the high frequency range. Together, they form sound absorbing wall portions 15, 15 that absorb sound. In addition, as another example of such a means for arranging the sound absorbing material, there may be mentioned the provision of the sound absorbing material on the upper and lower inner surfaces of the duct when the resonance tubes are arranged on the left and right sides of the duct as described above.

Other points that are common to the embodiments described above are designated by the same numbers in the figures and their explanations will be omitted.

Next, referring to FIGS. 4 to 6, these are front views showing other embodiments of the present silencer, and first of all, they are different from the above embodiments, especially in the arrangement, shape, number, etc. of the resonance cylinders. In the embodiment shown in Fig. 4, four resonant tubes 3 are arranged all around the inner circumference of the cross section of the rectangular duct, and of course they have the same target noise wavelength and are formed by the same method. In this example, the depths are different (see Ill to Intersection 4 in the figure).
The structure is such that it is formed to attenuate a plurality of noise components. Similarly, in the embodiment shown in FIG. 5, resonance tubes 3 are formed all around the inner circumference of the duct cross section, but this embodiment differs in that three of them are built in an arc shape. Furthermore, in the embodiment shown in FIG. 6, the cylindrical wall 4" is fixed to the duct outer peripheral iron plate 12 via four wooden plate-shaped supports 18... It is arranged in the center of the ventilation passage.The points in common with the previous embodiment are designated by the same numbers in the drawings, and the explanation thereof will be omitted.

Although not shown in the drawings, the number of resonance tubes may of course be one, for example, it is possible to omit one of the left and right resonance tubes in the embodiments of FIGS. 1 and 2, or it is possible to use a rectangular duct cross section. It is also possible to divide the tube into three vertically or horizontally arranged sections using two intermediate partition plates, form ventilation passages on both sides, and fix a cylinder bottom plate at a predetermined depth in the central section to use this as a resonant tube. - It is also possible to form resonance cylinders in the same manner and stack a plurality of the silencing devices shown in the embodiments of FIGS. 1 and 2 vertically, or to arrange them side by side on the left and right.

The embodiments have been configured as described above, and the present invention does not cover the specific shapes, structures, materials, dimensions, number, and arrangement of the resonance tube, duct, air passage of the duct, open end of the resonance tube, etc., unless it is contrary to the above-mentioned gist. It goes without saying that these relationships and the like can be changed in various ways and are not limited to the above embodiments.

[Effects of the Invention] The resonant silencer for an air supply tact according to the present invention incorporates one or more resonant cylinders with one end open and the other end closed and having a depth of approximately one-fourth of the target noise wavelength in a straight duct; Since the open end of the resonator cylinder is brought into contact with the air passage of the duct,
It has an effective silencing range that extends to the low frequency range, and can set a target noise frequency and attenuate it intensively and extremely effectively.

Furthermore, the resonant silencer of the present invention incorporates one or more resonant cylinders, which have one end open and the other end closed, each having a depth of approximately one-fourth of the target noise wavelength, as described above, in the straight duct. There is no need to extremely enlarge the diameter, it can be compactly stored in a duct, it can be installed at any piping location without taking up much installation space, and it can also be made inexpensive.

[Brief explanation of the drawing]

The drawings show embodiments, and FIG. 1 is a perspective view of a resonant silencing device for an air supply duct according to the present invention, FIG. 2 is a cross-sectional view of the silencing device, and FIGS. Another embodiment of the invention muffler is shown, FIG. 3 is a cross-sectional view thereof, and FIGS. 4 to 6 are front views thereof.

Claims (1)

[Claims] One or more resonant cylinders having a depth of approximately one-fourth of the target noise wavelength and having one end open and the other end closed are built into a straight duct, and the open end of the resonator cylinder is brought into contact with the air passage of the duct. A resonant silencer for air ducts featuring: