JP2017083652A - Sound deadening structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of further effectively exerting a suppression function of noise emitted from an air passage, while reducing a cost in a sound deadening structure for suppressing the noise.SOLUTION: A sound deadening structure includes a cover member 3 arranged by opening a space to an opening end 2 of an air passage body 1. This cover member 3 is arranged with a sound absorption material 4 on a plane opposite to the opening end 2 or provided with a reflection plane 5. This reflection plane 5 is made plane-shaped where a sound wave emitted from the opening end 2 is reflected in a regulated converging area 6 of a center direction of the cover member 3. The sound wave of the noise emitted from the opening end 2 is reflected in the converging area 6 of the center direction of the cover member 3 by the reflection plane 5 by the structure arranged in one block shape in this conversing area 6, and after that, it is attenuated by a direct sound absorbing action of the one block-shaped sound absorption material 4. Hence, the amount of the sound absorption material 4 is reduced, and yet, the direct sound absorption action can be obtained, and consequently, the sound deadening structure for effectively exerting the suppression function of the noise can be obtained, while reducing a cost.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a silencer structure that suppresses noise emitted from an air passage.

  At present, air conditioners mainly having an air blowing function are widely used, and technical developments for improving problems such as improving the capability of the main functions and reducing the power consumption are being made every day.

  Among such problems is the suppression of generated noise. In particular, in an air passage intended to convey blown air, it is a problem to suppress noise that propagates inside and is emitted from the opening end. In particular, from the viewpoint of increasing the flow resistance, it is a big problem in that it is difficult to cope with only simple physical soundproofing such as attaching a sound absorbing material to the inner surface of the air passage.

  In addition, the air path aiming at conveyance of blowing air here shows the air-conditioning duct which guides air from the outdoor to the indoor, for example by ventilation by a blower. Moreover, the ventilation path of the range hood for exhausting cooking smoke to the outdoors by ventilation with a blower, for example is shown. Moreover, the opening end in an air path shows the opening part for the inhalation | air-intake and exhaust_gas | exhaustion inside the ventilation path of the said air conditioning duct or range hood. And especially the noise which propagates from the air blower to the opening end on the indoor side is a problem.

  An example of a technique that effectively suppresses noise emitted from the opening end of the air passage without significantly increasing the flow resistance is ANC.

  This ANC refers to active noise control, and active noise that suppresses noise by sound interference by generating sound that is in reverse phase with respect to the noise propagating in the air path to be suppressed. Suppression technology.

  In such ANC technology, a microphone that serves as sound collecting means for detecting sound, a speaker that serves as sound generating means for generating anti-phase sound, and a control device for generating anti-phase sound are the basic components. It becomes an indispensable device.

  However, the ANC technique requires a complicated calculation processing capability for a control device that generates anti-phase sound, and this processing load increases according to the frequency of the sound. Therefore, it is generally difficult to cope with suppression of a high frequency band of about 1 kHz or more.

  In addition, in order to realize this complicated and high-load arithmetic processing in the control device, it is necessary to use an expensive control device such as a DSP or FGPA capable of high-speed arithmetic, which increases the cost of the entire system. It was a difficult point.

  Furthermore, the suppression effect can be exhibited only when the pipe diameter (wind path diameter) at which the sound propagating through the air path can be regarded as a plane wave is 1/2 or less of the wavelength of the suppression target sound, and the high frequency band is also the suppression target. Therefore, it is necessary to reduce the tube diameter. That is, for example, if the bandwidth is 1 kHz or less, the tube diameter needs to be about 17 cm or less.

  However, since the reduction in the diameter of the air passage is accompanied by an increase in the wind resistance, it is not suitable for suppressing the high frequency band from this point.

  For this reason, it is difficult to suppress noise including high-frequency components of about 1 kHz or more even using the ANC technology, and particularly noise components of around 2 kHz that are highly sensitive in the audible band are not affected by the suppression action, and the wind path It will be emitted from the open end of.

  Therefore, in order to further suppress noise, it is necessary to pay attention to suppression of sound in a high frequency band of about 1 KHz or higher, which is emitted from the opening end of the air passage.

  In order to suppress the noise emitted from the opening end of such an air passage, it is effective to dispose the sound-absorbing material at an interval facing the opening end.

  In this sound absorbing material, the vibration energy of the incident sound is replaced with the vibration of the structure by the structure of the structure having fine open cells and spaces, and the sound is attenuated by converting the heat energy. For example, soft urethane, glass wool, or a metal porous material, which is a porous material, is molded into a plate shape or a lump shape.

  Therefore, the sound absorbing performance (sound absorption rate) of this sound absorbing material is improved in proportion to the density and volume of the structure to some extent. Generally, if the same material is used, the density is higher and the thickness in the sound traveling direction is larger. The ability to suppress noise will also increase.

  In addition, from the principle that sound vibration is attenuated by replacing vibration energy of sound with vibration of the structure, that is, by converting heat energy, the sound absorption performance of the high frequency band sound that easily induces micro vibrations in the structure is also high. It is particularly suitable for suppressing high frequency band sounds.

  Thus, in order to suppress the noise emitted from the opening end of the air passage, it is effective to arrange the sound absorbing material so as to face the opening end and be spaced apart.

  However, how to reduce the cost required for noise suppression even in the configuration using the sound absorbing material is a problem in terms of wide application to general home appliances and the like. Conventionally, a silencing structure of this type of air passage is known to have a structure that reduces the cost required by reducing the amount of sound-absorbing material used to solve such problems (for example, Patent Document 1).

  Hereinafter, a conventional silencing structure of the air passage will be described with reference to FIG.

  As shown in the figure, a conventional noise suppression device for an air passage opening includes a suction port 101 for opening one end and sucking air in a cylindrical air intake duct 100 forming an air passage for conveying air. ing. A cover member 102 having a shape for covering the opening by providing a space for intake to the intake port 101 is disposed.

  The surface of the cover member 102 facing the air inlet 101 is formed in a concave lens shape so that noise emitted from the air inlet 101 is reflected on the end side of the cover member 102. Further, a sound absorbing material 103 that absorbs the reflected noise is attached in a ring shape to the end of the surface of the cover member 102 facing the air inlet 101.

  With the above configuration, if noise propagates inside the intake duct 100, the noise is emitted from the intake port 101 to the surrounding space. The noise emitted from the intake port 101 is directed to a surface of the cover member 102 that is disposed with a space with respect to the intake port 101 and that faces the intake port 101. At this time, the noise is reflected to the end side of the cover member 102 because the surface of the cover member 102 facing the air inlet 101 is formed in a concave lens shape.

  Since the sound absorbing material 103 is attached to the end of the surface of the cover member 102 that faces the air inlet 101, the reflected noise is attenuated by the sound absorbing effect of the sound absorbing material 103.

  Accordingly, the sound absorbing material 103 attached to the end of the cover member 102 in a ring shape can be efficiently suppressed by attenuating the noise emitted from the intake port 101 by sound absorption. For this reason, the cost is reduced with respect to a structure in which the sound absorbing material 103 is arranged in a plane on the surface facing the air inlet 101.

Japanese Patent No. 4423665

  In such a conventional silencing structure of the air passage, a space is provided for the air inlet 101 serving as the opening end of the air intake duct 100 that propagates noise to cover the opening, and the noise emitted from the air inlet 101 is covered with the cover member. A cover member 102 formed in the shape of a concave lens to be reflected on the end side of 102 is disposed. Further, since the sound absorbing material 103 is attached in a ring shape to the end of the surface of the cover member 102 facing the air inlet 101, the reflected noise is attenuated by the sound absorbing effect of the sound absorbing material 103. Therefore, the noise absorbing material 103 used for noise suppression is reduced by forming a ring shape with respect to the conventional structure in which the sound absorbing material 103 is arranged in a plane on the surface facing the intake port 101.

  However, if the sound (sound wave) has a wall surface in the traveling direction as a characteristic, it is basically based on the “law of reflection” of the spatial propagation wave reflected in the opposite direction at the same angle as the incident angle with respect to the wall surface. Here, the cover member 102 is formed in a concave lens shape that covers the opening with respect to the intake port 101 at the open end of the intake duct 100. That is, the noise emitted from the air inlet 101 and traveling to the cover member 102 is mainly reflected in the center direction, not the end portion of the cover member 102.

  If the reflection of noise in the cover member 102 is mainly in the central direction, the sound absorbing material 103 attached to the end of the cover member 102 in a ring shape cannot obtain much of the direct sound absorbing action.

  Therefore, although the overall cost can be reduced by reducing the amount of the sound absorbing material 103, many direct sound absorbing actions cannot be obtained. For this reason, there has been a problem that an effective noise suppression function cannot be sufficiently achieved.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a muffler structure that can perform a noise suppression function more effectively while reducing costs.

  In order to achieve this object, the sound deadening structure according to the present invention includes a cylindrical air passage body that has an opening end that is an opening provided at an end portion thereof and allows air to pass through the internal space, and the opening end. A cover member that reflects a sound wave from the light source toward a convergence region provided in a central portion of the reflection surface via a reflection surface that faces the opening end, and is provided between the air passage body and the cover member And a sound-absorbing material that absorbs the reflected sound wave provided in a lump shape in the convergence area, thereby achieving the intended purpose.

  According to the present invention, since a direct sound absorbing action can be obtained while reducing the amount of the sound absorbing material used, it is possible to provide a sound deadening structure that can perform a noise suppressing function more effectively while reducing costs. .

The side view which cut and showed the structure of the sound deadening structure concerning Embodiment 1 of this invention partially The top view which showed the structure only of the cover member with which the sound deadening structure which concerns on Embodiment 1 is equipped. The side view which cut and showed an example of the composition of the cover member with which the sound deadening structure concerning Embodiment 1 is provided The side view which cut and showed another example of the composition of the cover member with which the sound deadening structure concerning Embodiment 1 is provided The side view which cut and showed another example of the composition of the cover member with which the sound deadening structure concerning Embodiment 1 is provided The side view which cut and showed another example of the composition of the cover member with which the sound deadening structure concerning Embodiment 1 is provided The side view which cut and showed another example of the composition of the cover member with which the sound deadening structure concerning Embodiment 1 is provided The front view which permeate | transmitted and showed the structure of the example of 1 adaptation of the sound deadening structure concerning Embodiment 2 The top view which showed an example of the arrangement configuration of the cover member in an example of the silencing adaptation which concerns on Embodiment 2. FIG. The top view which showed the other example of the arrangement configuration of the cover member in an example of the adaptation of the sound deadening structure which concerns on Embodiment 2. FIG. The front view which permeate | transmitted and showed the other example of adaptation of the silencing structure which concerns on Embodiment 2. FIG. The front view which permeate | transmitted and showed the other example of adaptation of the silencing structure which concerns on Embodiment 2. FIG. The front view which showed another example of adaptation of the sound deadening structure concerning Embodiment 2 partially fractured after penetration The front view which showed another example of adaptation of the sound deadening structure concerning Embodiment 2 partially fractured after penetration Perspective side view showing conventional structure by transmission

  The silencing structure according to the present invention has a cylindrical air passage body having an opening end, which is an opening provided at an end portion, through which blown air passes, and a sound wave from the opening end is opposed to the opening end. A cover member that reflects toward the convergence region provided in the center of the reflection surface via the reflection surface, a space provided between the air passage body and the cover member, and a lump in the convergence region And a sound-absorbing material that absorbs the reflected sound wave.

  In other words, the structure in which the sound wave traveling toward the cover member is reflected to the convergence region and the sound absorbing material is arranged in a lump shape in the convergence region, thereby obtaining a direct sound absorbing effect while reducing the amount of the sound absorbing material used. It is done. As a result, the noise suppressing function can be more effectively achieved while reducing the cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples embodying the present invention, and do not limit the technical scope of the present invention.
Further, in each of the drawings, description of details of each part not directly related to the present invention is omitted.

(Embodiment 1)
As shown in FIG. 1 and FIG. 2, the sound deadening structure according to the present embodiment is a cover member that is arranged with a space open to the opening end 2 of the air passage body 1 and that covers the opening end 2. 3 and a structure in which a sound absorbing material 4 having a sound absorbing action is arranged on the surface of the cover member 3 facing the opening end 2 is provided.

  The air passage body 1 has a cylindrical shape and constitutes an air passage for allowing the air flow of the blown air to pass through the internal space. In addition, the air passage body 1 is an air passage for passing a flowing air of blown air. For example, the air duct body 1 is provided from a piping duct, a range hood, or an intake port of an air cleaner to an exhaust port in ventilation ventilation for guiding the blown air. This is the air flow path.

  The blown air flowing inside the air passage body 1 is not shown in the figure, but is generated by an electric blower based on rotational driving of blades by an electric motor, for example. As a result, noise that propagates inside the air passage body 1 is generated.

  Therefore, for example, if the electric blower is disposed on the left side of the air passage body 1 in the horizontal direction in FIG. 1, the noise propagates in the air passage body 1 from the left to the right, and the open end 2 It will be emitted to the external space as a sound wave. In addition, the progress of the sound wave is schematically displayed by a dotted arrow line in the figure.

  The opening end 2 is provided at one end of the cylindrical air passage body 1 as an opening that communicates the space inside the air passage body 1 with the outside. In addition, the opening end 2 should just be in one end of the air path body 1, and the other end does not necessarily need to be an opening.

  The cover member 3 has a disk shape having a surface facing the opening end 2 and is sized to cover the opening end 2 by providing a space.

  A surface of the cover member 3 facing the opening end 2 is provided with a reflecting surface 5 that reflects sound waves emitted and traveling from the opening end 2 toward the center of the cover member 3.

  The reflecting surface 5 is emitted from the opening end 2 and reflects the traveling sound wave to the central portion of the cover member 3, that is, to the prescribed convergence region 6 schematically indicated by a thick dotted line in the drawing. Is configured. The central direction and the central part here refer to the central direction and the vicinity of the center in FIG. 2 when the cover member 3 is viewed from the traveling direction of the sound wave. And since the cover member 3 is comprised by the size which covers the air path body 1, the cover member 3 is slightly large with respect to the air path body 1. FIG. Further, in the present embodiment, since the cross sections thereof are substantially matched, the central direction and the central portion substantially coincide with the central portion in the cross section perpendicular to the blowing direction of the air passage body 1. The surface shape of the reflecting surface 5 is, for example, a concave shape as shown in the figure, but the incident angle and the reflection angle with respect to the converging region 6 are the same at the incident position of the sound wave on the same surface, and the converging region 6 is as small as possible. It is desirable to narrow down the range.

  The surface shape of the reflecting surface 5 may be a concentric combination of a plurality of concave surfaces having different curvatures as long as the above conditions are satisfied. In FIG. 1, a surface shape is formed by combining two types of concave shapes. When combined concentrically, each concave surface forms a donut shape except for the circular shape at the center.

  The sound absorbing material 4 is arranged in a lump shape in the convergence region 6 in the central direction of the cover member 3, and is fixed to the support rod 7 protruding from the center of the cover member 3 toward the opening end 2. ing. In other words, a part of the sound absorbing material 4 constitutes the convergence region 6.

  As described above, the sound-absorbing material 4 has improved sound-absorbing performance (sound-absorbing rate) in proportion to the density and volume of the structure to some extent. The greater the thickness, the higher the sound attenuation capability.

  However, even if the density and the thickness in the sound traveling direction are increased to a certain extent, it is not possible to improve the sound absorption performance to a certain extent.

  Accordingly, it is a practical point to achieve the sound absorbing performance required in the convergence region 6 in consideration of the characteristics of the sound absorbing material 4 and to combine them into the minimum size.

  The space provided between the opening end 2 and the cover member 3 secures an air passage for air flowing out from the opening end 2 or air flowing into the tubular air passage body 1 from the opening end 2. . That is, this space is provided with an opening in the air passage from the central axis of the air passage body 1 toward the side wall, in other words, from the center of the cover member 3 toward the peripheral direction (vertical direction in FIG. 1).

  The cover member 3 and the support rod 7 are not particularly defined as long as the shape can be maintained for a long period of time under the usage conditions (temperature, presence or absence of oil contained in the blown air, etc.) For example, a metal material such as iron may be used.

  Although it is necessary to fix and arrange the cover member 3 at a predetermined position with respect to the air passage body 1, details of the fixing method do not depend on the gist of the present plan, and thus detailed description using the drawings is omitted. . For example, the cover member 3 may be fixed to the tip end of a rod-like stay member that extends from the air passage body 1, for example.

  The above is the basic structure, but each element may be configured as shown below.

  For example, the reflecting surface 5 provided in the cover member 3 has an inclined angle with respect to the plane constituting the open end 2 as it is closer to the center from the outer periphery of the cover member 3 as shown in FIG. It is also possible to use a Fresnel shape with a shallow depth.

  When the Fresnel shape is used as the reflecting surface 5, if the material of the convergence region 6 is the same, the depth of the reflecting surface 5 is shallow with respect to the continuous combination of concave shapes, that is, the dimension is indicated by Sa in the figure. It is an advantage that the thickness of the cover member 3 can be reduced.

  However, it should be noted that noise suppression performance is impaired because outward sound wave reflection occurs at the step portion of the Fresnel shape.

  Further, as shown in FIG. 4, for example, the sound absorbing performance of the sound absorbing material 4 is covered by covering the opposing surface of the sound absorbing material 4 and the side surface portion not included in the convergence region 6 of the sound absorbing material 4 with a hard protective cover 8. It is good also as a structure which protects from the deterioration factor from the external world which causes deterioration and destruction of this.

  The deterioration factor mentioned here means that the blown air directly collides with or adheres to the sound absorbing material 4 along the flow of the blown air when the blown air contains a large amount of liquid components such as moisture and oil and dust. This indicates the matter that degrades the sound absorption performance.

  Therefore, since the protective cover 8 is hard and does not allow liquid to pass therethrough, it is formed using, for example, a metal material such as iron, and is fixed to the support rod 7 with screws or the like. It is.

  When the protective cover 8 is formed of a hard material, most of the sound traveling toward the protective cover 8 is reflected without being transmitted.

  However, the facing surface of the protective cover 8 that faces the opening end 2 may have a shape having a plane parallel to the plane that forms the opening end 2.

  With such a shape having a flat surface, the sound wave traveling from the direction of the opening end 2 is directed again toward the opening end 2 and reflected, thereby suppressing the diffusion of noise to the surrounding space.

  Further, as shown in FIG. 5, for example, the sound absorbing material 4 has a shape that is a shadow of a sound wave traveling from the direction of the opening end 2 and omits the non-convergent region 20 adjacent to the reflecting surface that is not included in the converging region 6. Further downsizing is possible.

  In addition, when miniaturization is aimed at in such a shape, even if a liquid component etc. are contained in blowing air, it is direct to the sound-absorbing material 4 such as liquid adhering to the reflecting surface 5 along the flow of blowing air. Adhesion and penetration can also be reduced.

  Therefore, the point which can further suppress deterioration of sound absorption performance like the above is also an advantage.

  The sound absorbing material 4 shown in FIG. 5 has a dome shape extending from the protective cover 8 toward the reflecting surface by further cutting away the portion corresponding to the side surface of the convergence region 6.

  Further, as shown in FIG. 6, for example, instead of being fixed to the support bar 7 and being fixed to the center of the reflection surface 5, one end is fixed to the side surface of the cover member 3 and the other end is provided with the protective cover 8. The sound absorbing material 4 may be lifted from the reflecting surface 5 by using the support stay 7a to be fixed. Here, the protective cover 8 is fixed to the sound absorbing material 4.

  With such a configuration, even if a liquid component or the like is included in the blown air, direct adhesion and penetration of the liquid or the like adhering to the reflection surface 5 along the flow of the blown air is further reduced. can do.

  Therefore, as described above, it is possible to further suppress the deterioration of the sound absorption performance.

Further, as shown in FIG. 7, for example, the space 9 may be provided inside the sound absorbing material 4. As a result, the sound absorbing performance can be further improved. This is an application of a technique in which the sound absorbing material 4 improves the sound absorption rate particularly in the low frequency band when an air layer is provided behind the sound incident direction.
(Embodiment 2)
By the way, since the cover member 3 is configured to have a size covering the open end 2 of the air passage body 1 as described above, it is necessary to increase the size in accordance with the tube diameter of the air passage body 1 itself.

  As described above, when the size of the cover member 3 needs to be increased in accordance with the tube diameter of the air passage body 1, the entire volume of the cover member 3 including the sound absorbing material 4 and the reflecting surface 5 is increased. However, the problem is that the arrangement space of the cover member 3 and the overall cost also increase.

  Therefore, in the present embodiment, several arrangement relationships between the air passage body 1 and the cover member 3 for solving the arrangement space and cost increase are exemplified.

  8 to 10 show an example in which a plurality of cover members 3 having a reflecting surface having a diameter smaller than the tube diameter of the air passage body 1 are opposed to the opening end 2 in order to deal with the above-described problems. That is, the effect can be obtained even if a plurality of cover members 3 that are small in size according to the tube diameter of the air passage body 1 are spread in a flat shape.

  In the illustrated example, a blower fan 10 including an electric blower is provided above the air passage body 1, the indoor air is sucked from the opening end 2 at the lower end, and the outdoor air is exhausted by the flow of the blown air upward. An example of application to a range hood is shown.

  Here, FIG. 8 is a front view showing the structure of the range hood through, and FIGS. 9 and 10 are plan views showing only the arrangement state of the cover member 3 provided in the range hood.

  In the figure, the flow of the blown air is schematically shown using a dashed-dotted thick arrow line, and the propagation of noise is schematically shown using a dotted thin arrow line.

  As shown in the figure, for example, a plurality of small sized plates are used for the rectifying plate 11 for increasing the intake air speed by narrowing the opening area of the air passage disposed opposite to the opening end 2 of the air passage body 1. The cover member 3 is arranged in a flat shape with the reflection surface 5 facing the opening end 2. At this time, the side wall of the opening end 2 and the end of the assembly of the cover members 3 are made to coincide.

  In addition, regarding the arrangement form of the plurality of cover members 3, for example, as shown in FIG. 9, the gaps are not generated in the combination of the reflecting surfaces 5 by being aligned vertically and horizontally.

  Moreover, as shown in FIG. 10, the center of the reflecting surface 5 is arranged in a triangular shape and further arranged without a gap, thereby increasing the corresponding area of the reflecting surface 5 with respect to the opening end 2 and further reducing noise. It can also be increased. In other words, at least three cover members 3 can be adjacent to each other, and the connecting lines connecting the central portions of the reflection surfaces of the cover member 3 can be arranged in a triangle.

  In this way, the use of a plurality of cover members 3 spread in a flat manner can reduce the overall volume of the cover member 3 and reduce the cost, and also reduce the thickness from the reflecting surface 5 to the end of the sound absorbing material 4. It is also possible.

  Therefore, it can also be used as noise suppression means in a blower device in which an empty space is limited in the depth direction opposite to the opening end 2.

  In addition, in the utilization to a blower device that needs to cover a plurality of cover members 3 in this way, when the pipe diameter of the air passage body 1 is large, noise propagating through the inside of the air passage body 1 is a considerably high frequency band. Since it does not become a plane wave, it is a problem that it is difficult to achieve the noise suppressing effect.

  For this problem, as shown in FIG. 11, the noise propagated by disposing a lattice body 12 that divides the tube diameter into a plurality of faces facing the opening end 2 inside the air passage body 1 is transmitted in a high frequency band. It is effective to make it into a plane wave.

  In addition, as described above, each aperture diameter of the lattice body 12 is desirably set to ½ or less of the wavelength of the sound to be suppressed. In addition, the length in the longitudinal direction of the air path of the lattice body 12 (vertical direction in FIG. 11) is desirably set to be 1/2 or more of the wavelength of the sound to be suppressed.

  Further, in FIG. 12, the ANC that performs the above-described active noise control function, which is shown as a whole by a dotted encircled line, on the sound generation source side inside the air passage body 1 that is the previous stage of the lattice body 12. Means 13 may be arranged and provided.

  By providing the cover member 3, the ANC means 13 can be provided with the function of suppressing only the sound wave on the low frequency side below the frequency band targeted for plane wave generation, and the noise of a wide frequency band as a whole. Suppression can be realized. That is, it is possible to allow the ANC means 13 to have only the function of suppressing sound waves on the low frequency side below the frequency band of the sound to be suppressed by the sound absorbing material 4.

  In addition, since the ANC means 13 can specialize in the suppression of the low frequency sound, it is possible to reduce the processing load of the control device realized in combination, and the lower cost control device can be utilized, so the overall cost is reduced. This is also advantageous in that it can be reduced.

  Furthermore, in place of the arrangement of the ANC means 13, as shown in FIG. 13, by providing an air chamber of a side branch structure on the inner surface of the air passage body 1, the natural frequency based on the air resonance is centered. One or more resonator bodies 14 that absorb and mute the sound may be provided.

  The resonator body 14 is a Helmholtz resonator including a cavity 15a that forms an air chamber separated from the outside, and an opening 15b that connects the cavity 15a, the outside, and the space.

  In this Helmholtz resonator, the air in the vicinity of the opening hole 15b becomes a mass body, and the air in the cavity 15a acts as an elastic body to form a vibration system, which is determined by the relationship between the mass and the elastic body. Generates frequency.

  If this natural frequency and the frequency of the sound incident on the aperture 15b overlap, resonance occurs and the incident sound receives a damping effect due to the viscous friction of air against the wall surface of the aperture 15b. A sound absorbing function will be produced.

  Therefore, it is effective if the resonator body 14 is configured so that this natural frequency is the same as the peak frequency band among the sound waves of the low frequency side noise below the frequency band targeted for the plane wave. Noise (on the low frequency band side) can be suppressed.

  In this way, if the configuration using the resonator body 14 instead of the ANC means 13, there is no need to use a plurality of expensive devices such as a microphone, a speaker, a control device, etc., and this is unnecessary and the overall cost is low. Can be achieved. In addition, since it is based on passive silencing consisting of a physical configuration, it is advantageous in that the performance hardly deteriorates due to changes in environmental factors and the influence of dirt, and the function of suppressing noise can be achieved over a long period of time.

  In addition, as shown in FIG. 14, the resonator bodies 14 and 14a (two types of structures are mounted in description on a figure) which set several different natural frequencies can also be arranged and provided.

In this case, since each natural frequency to which the resonator bodies 14 and 14a can be applied can be set corresponding to a plurality of peaks in the frequency band on the low frequency side, more comprehensive (low frequency Noise on the band side can be suppressed. (Outline of the embodiment)
In the sound deadening structure according to the embodiment of the present invention, a cylindrical shape is formed so as to cover the opening end 2 by opening a space with respect to the opening end 2 of the air passage body 1 for passing the flowing air of the blown air inside. The sound absorbing material 4 is disposed on the surface of the cover member 3 facing the opening end 2 of the cover member 3. A surface facing the opening end 2 of the cover member 3 is provided with a reflecting surface 5, and this reflecting surface 5 is emitted from the opening end 2 and reflects the traveling sound wave to a prescribed convergence region 6 in the center direction of the cover member 3. The surface shape to be made is configured. The sound absorbing material 4 is structured to be arranged in a lump in the convergence region 6 in the center direction of the cover member 3.

  Thereby, the sound wave of the noise propagating through the inside of the air passage body 1 and emitted from the opening end 2 is reflected by the reflecting surface 5 provided in the cover member 3 to the convergence region 6 defined in the center direction of the cover member 3.

  The reflected sound wave is attenuated by receiving the direct sound absorbing action because the sound absorbing material 4 is arranged in a lump shape in the convergence region 6, and as a result, the noise emitted from the opening end 2 is reduced. It can be effectively suppressed.

  Therefore, since the sound absorbing material can be reduced in volume as a lump shape and a direct sound absorbing action can be obtained, it is possible to provide an effect of providing a sound deadening structure capable of performing a noise suppressing function more effectively while reducing costs. Can do.

  The silencing structure according to the present invention can more effectively suppress the noise emitted from the air passage while reducing the cost. Therefore, a ventilation device such as a general household range hood, an air conditioner, etc. It is useful as a silencing structure used in

DESCRIPTION OF SYMBOLS 1 Air path body 2 Open end 3 Cover member 4 Sound absorbing material 5 Reflecting surface 6 Convergence area | region 8 Protective cover 7a Support stay 9 Space part 12 Grid body 13 ANC means 14, 14a Resonator body 20 Out-of-convergence area | region

Claims (20)

A cylindrical air passage body having an opening end which is an opening provided at the end portion and passing the blown air through the internal space;
A cover member that reflects sound waves from the opening end toward a convergence region provided in a central portion of the reflecting surface through a reflecting surface opposed to the opening end;
A space provided between the air passage body and the cover member;
A sound deadening structure comprising a sound absorbing material that is provided in a lump shape in the convergence region and absorbs the reflected sound wave. The reflective surface is
The silencing structure according to claim 1, wherein the sound absorbing structure has a concave shape in which an incident angle and a reflection angle with respect to the convergence region are the same at an incident position of a sound wave with respect to the reflection surface. The reflective surface is
The silencing structure according to claim 2, wherein a plurality of concave surfaces having different curvatures are concentrically combined. The reflective surface is
2. The muffler structure according to claim 1, wherein the silencer structure has a Fresnel shape in which an inclination angle with respect to a plane constituting the opening end is shallower as it is closer to the center of the cover member. The sound absorbing material is
The silencing structure according to claim 1, wherein a facing surface facing the opening end and a side surface not included in the convergence region are covered with a hard protective cover. The facing surface is
The silencing structure according to claim 5, wherein the silencing structure is a plane parallel to a plane constituting the open end. The sound absorbing material is
The silencing structure according to claim 1, wherein the sound deadening structure has a shape in which a non-convergence region adjacent to the reflection surface that is a shadow of a sound wave traveling from the opening end and is not included in the convergence region is omitted. The sound absorbing material is fixed and held by the protective cover,
The noise reduction structure according to claim 5, wherein the cover member and the protective cover are fixed by a support stay and the sound absorbing material is floated from the reflection surface. The sound absorbing material is
The silencing structure according to claim 1, wherein a space portion serving as an air layer is provided inside. 2. The silencing structure according to claim 1, wherein a plurality of the cover members having the reflecting surface whose diameter is smaller than the tube diameter of the air passage body are arranged facing the opening end. The silencing structure according to claim 10, wherein the side wall of the opening end and the end of the cover member are aligned to cover the cover member in a planar shape. The sound deadening structure according to claim 10, wherein the plurality of cover members are arranged vertically and horizontally and spread in a flat shape. At least three of the cover members are adjacent to each other;
The silencing structure according to claim 10, wherein the connection lines respectively connecting the center portions of the reflection surfaces of the cover member are triangular. The silencing structure according to claim 10, wherein a lattice body that divides the tube diameter into a plurality of portions facing the opening end is arranged inside the air passage body. The opening diameter of each of the lattice bodies is
The muffler structure according to claim 14, wherein the muffler structure is set to ½ or less of a wavelength of a sound to be suppressed. The length in the longitudinal direction of the air passage body in each lattice body is
The muffler structure according to claim 14, wherein the muffler structure is ½ or more of a wavelength of a sound to be suppressed. The muffler structure according to claim 14, wherein ANC means for performing an active noise control function is disposed on a side of the lattice body opposite to the cover member. The ANC means includes
The silencing structure according to claim 17, which has a function of suppressing a sound wave on a low frequency side that is equal to or lower than a frequency band of a sound to be suppressed by the sound absorbing material. One or more resonator bodies that absorb and mute sound centered on a natural frequency based on air resonance by an air chamber having a side branch structure on the side opposite to the cover member in the lattice body are disposed. Item 15. The muffler structure according to Item 14. A plurality of the resonator bodies;
The plurality of resonator bodies are:
20. The muffler structure according to claim 19, wherein at least two different natural frequencies are set.

Images