JP6902059B2 - Silent ventilation structure - Google Patents

Description

The present invention relates to a muffling ventilation structure such as a ventilation hood. More specifically, the present invention relates to an external hood type sound deadening ventilation structure provided on a wall and having a high sound deadening effect while maintaining air permeability.

Conventionally, ventilation structures such as ventilation hoods, ventilation sleeves, and louvers, which are required to have ventilation, allow sound to pass through at the same time as air, so noise countermeasures may be required. In the conventional ventilation structure, a sound absorbing material is installed in the structure in order to obtain sound deadening performance (see Patent Documents 1, 2, 3, 4, and 5).

The technique described in Patent Document 1 is an outdoor hood installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors. This outdoor hood is loaded into a cover to form an air passage and also has a sound deadening material that absorbs the sound entering the air passage, and the air passage is bent between the outdoor opening and the indoor opening. It includes a formed air passage main body portion and an air passage expansion portion formed by partially expanding the internal space of the air passage main body portion. It is said that this outdoor hood can have high sound absorption performance without increasing the size of the cover and without deteriorating the pressure loss.
The technique described in Patent Document 2 is a soundproof forced ventilation port provided with an exhaust fan on the inside and an exhaust port hood covering the exhaust port on the outside with the exhaust port provided on the wall material as a boundary. Is. In this soundproof forced ventilation port, the exhaust hood is made of a concrete plate, and a plate-shaped sound absorbing material made of an inorganic sound absorbing material is detachably attached to the inside of the concrete plate. The surface of the plate-shaped sound absorbing material is covered with an antifouling film that can be attached and detached. It is said that this soundproof forced ventilation port can sufficiently maintain both ventilation performance and soundproofing performance even in an environment used as a forced exhaust port for cooking, for example.

The technique described in Patent Document 3 is a silencer attached to a supercharger. This silencer has an annular portion having an inflow portion through which gas flows and is formed in an annular shape, a closed portion that closes an opening on one side of the annular portion in the central axis direction, and the other side in the central axis direction. It is provided with an outlet for discharging gas toward the air, and attenuates the sound entering from the outlet. The closing portion is a holding plate having a through hole made of punching metal or the like, a closing plate arranged on the side opposite to the discharge port side of the holding plate, and a closing portion sandwiched between the holding plate and the closing plate. It is equipped with a sound absorbing material. This silencer is said to be able to exhibit good sound deadening performance.
The technique described in Patent Document 4 is a louver-structured silencer in which bent-shaped ventilation passages for ventilation inside and outside the building are arranged in a multi-stage manner to reduce the sound pressure of noise sound waves passing through the ventilation passages. is there. This sound deadening device is provided on the surface of the blade body facing the air passage, the blade body formed in a bent shape that separates the adjacent air passages, the sound deadening chamber that accommodates the sound absorbing material in the space inside the blade body, and the surface of the blade body facing the air passage. It is provided with a plate-shaped member (curved surface-shaped sound wave reflecting plate) that guides noise sound waves entering from one of the first ventilation ports of the ventilation path to the inside of the sound deadening chamber. In this louver structure sound deadening device, the length of the ventilation path can be shortened, and the ventilation path and the sound deadening chamber can be laminated in multiple stages over the entire wall surface, so that excellent ventilation can be obtained while providing sound insulation. It is said that it can be done.

Similar to Patent Document 4, the technique described in Patent Document 5 also has a bent-shaped ventilation path for ventilating the inside and outside of the building arranged in a multi-stage manner so as to reduce the sound pressure of noise sound waves passing through the ventilation path. It is a sound deadening device with a louvered structure. This sound deadening device accommodates first and second sound wave reflecting plates having a curved shape that reflects noise sound waves, and a sound absorbing material, respectively, and introduces noise sound waves reflected by the first and second sound wave reflecting plates. The first and second muffling chambers are provided to reduce the sound pressure, and the first muffling chamber and the second muffling chamber are continuously arranged in the ventilation path. Similar to the sound deadening device of Patent Document 4, the sound deadening device having a louver structure can also shorten the length of the ventilation path, and the ventilation path and the sound deadening chamber can be laminated in a multi-stage manner over the entire wall surface. It is said that excellent breathability can be obtained while having sound insulation.

Japanese Unexamined Patent Publication No. 2010-266156 Japanese Unexamined Patent Publication No. 2004-232909 Japanese Unexamined Patent Publication No. 2014-005760 Japanese Unexamined Patent Publication No. 2008-144996 Japanese Unexamined Patent Publication No. 2008-12223

By the way, in the ventilation structure, it is effective to install a sound absorbing material in order to obtain sound deadening performance, but if a large amount of sound absorbing material is installed in order to improve the sound deadening performance and obtain high sound deadening performance, the ventilation property is impaired. There was a problem of being ventilated.
Further, in the technique described in Patent Document 1, in addition to the air passage main body portion, the internal space thereof is partially expanded to form the air passage expansion portion in the air passage formed by the sound deadening material. For this reason, there is a problem that not only the amount of the sound deadening material increases but also the outdoor hood itself becomes large. In addition, there is a problem that the air to be ventilated stagnates in the air passage extension portion. Further, since the air passage is formed by the muffling material, there is a problem that the muffling cannot be efficiently performed.
Further, in the technique described in Patent Document 2, since the antifouling film is attached to the entire surface of the sound absorbing material, it becomes difficult for the sound to come into contact with the sound absorbing material. There was a problem that it became difficult to absorb sound.

Further, in the technique described in Patent Document 3, since the sound absorbing material is covered with a holding plate having through holes evenly perforated such as punching metal, not only the manufacturing cost is high, but also the sound cannot be efficiently muted. There was a problem.
Further, the techniques disclosed in Patent Documents 4 and 5 are premised on a louver structure, and ventilation paths between sound deadening chambers (blades) are stacked in multiple stages between the decorative plate and the outer peripheral wall (concrete wall). There was a problem that it was difficult to arrange the concrete due to space restrictions. Further, in the techniques disclosed in Patent Documents 4 and 5, there is a problem that the cost is high because a curved sound wave reflector or a punching plate is used.
Therefore, in order to achieve both high sound deadening performance and ventilation in a sound deadening ventilation structure such as a ventilation hood, for example, an external hood type sound deadening ventilation structure installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors. Was required to absorb sound with higher efficiency while using the same volume of sound absorbing material.

The present invention solves the above-mentioned problems and problems of the prior art, and has a hood-type sound deadening ventilation structure such as a ventilation hood, for example, an external hood type installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors. It is an object of the present invention to provide a sound deadening ventilation structure capable of enhancing sound deadening performance while maintaining air permeability, and having a sound deadening effect higher than that of a conventional sound absorbing material and an air column resonance structure.

In order to achieve the above object, the sound deadening ventilation structure of the first aspect of the present invention is a hood type sound deadening ventilation structure, and is a sleeve connected to the hood body and the space inside the hood body. A hood provided with, at least one first opening provided in the hood body, at least one second opening provided in the sleeve, a sound absorbing material provided inside the hood body, and one of the surfaces of the sound absorbing material. It has a covering material that selectively covers the portion, and the traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different, and the covering material absorbs sound. The other part of the surface of the material is selectively exposed, and the selective exposed part is configured as at least one contact surface that contacts the space in the ventilation hood, and the sound absorbing material is the surface to which the sleeve is connected. and attached inner surface of the opposing hood body, and the inner surface of the hood body opposite to the first opening and the coating material is a material made of a material impervious to sound, the material of the material impervious to sound, A plate-shaped material with the same thickness as the covering material used is installed so as to block all the waveguides of the acoustic tube, and when evaluated by the 4-microphone method, the transmission loss is 5 dB or more over 250 Hz to 4000 Hz. It is a material of a certain material, and at least one contact surface is 100 Hz or more, and the order of the frequency resonance mode in the audible range is set to n = 1, 2, ... (Positive integer) from the lower side, and the resonance of the nth order. When the frequency corresponding to the frequency of the mode is λn, it exists within the range of λn / 16 from the point where the sound pressure of the sound wave corresponding to any of the frequencies of the resonance mode is maximized.

Here, at least one contact surface has a frequency of 100 Hz or higher, and the order of the resonance mode of the frequency in the audible range is set to n = 1, 2, ... (Positive integer) from the lower side, and the frequency of the resonance mode of the nth order is set. When the corresponding wavelength is λn, it is preferable that the frequency exists within the range of λn / 16 from the corner end portion in the hood body.
Further, the positive integer n is preferably 3 or less.
Further, it is preferable that the traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different by 90 °.

Further, it is preferable that at least one contact surface occupies an area of 1.0% to 50% with respect to the total area of the surface of the sound absorbing material.
Further, the sound absorbing material is preferably attached to an area of 50% or more with respect to the total area of the inner surface of the hood body excluding the first opening and the connecting portion of the sleeve.
The volume of the sound absorbing material is preferably 1.0% to 50% of the volume of the hood body.
In addition, the muffling ventilation structure is an external hood type muffling ventilation structure installed on the outdoor side of the ventilation port penetrating the wall separating the indoor and the outdoor, the hood body is arranged outdoors, and the sleeve is a wall. It is preferably arranged so as to penetrate.
Further, at least one side surface of the hood has at least one tubular body having an opening opening in the space inside the hood, and the inside of the tubular body is filled with a sound absorbing material, and the opening of the tubular body. It is selectively exposes a portion of the surface of the sound absorbing material, preferred to configure the selective exposure portion as a contact surface for contact with the space in the hood arbitrariness.

In order to achieve the above object, the sound deadening ventilation structure of the second aspect of the present invention is a hood type sound deadening ventilation structure, and is a sleeve connected to the hood body and the space inside the hood body. The hood comprises, at least one first opening provided in the hood body, at least one second opening provided in the sleeve, and at least one side surface of the hood having an opening that opens into a space within the hood. It has at least one tubular body and a sound absorbing material provided inside the tubular body, and the traveling direction of the sound passing through the first opening is different from the traveling direction of the sound passing through the second opening. The opening of the tubular body selectively exposes a part of the surface of the sound absorbing material, and the selective exposed part is configured as a contact surface in contact with the space in the hood.

Here, the contact surface has a wavelength corresponding to the frequency of the nth-order resonance mode, with n = 1, 2, ... (Positive integer) from the lower side of the resonance mode order of the frequency in the audible range at 100 Hz or higher. When is λn, it must be within the range of λn / 16 from the point where the sound pressure of the sound wave corresponding to one of the wavelengths of the resonance mode is maximized, or λn / 16 from the corner end in the hood body. It is preferably within the range.
Further, the positive integer n is preferably 3 or less.
Further, it is preferable that the traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different by 90 °.
Further, the contact surface preferably occupies an area of 1.0% to 50% with respect to the total area of the inner surface of the hood excluding the first opening and the second opening.
The volume of the sound absorbing material is preferably 1.0% to 50% of the internal volume of the hood.

Further, the tubular body is preferably arranged in the hood body.
Further, it is preferable that the tubular body is arranged outside the hood, and the opening of the tubular body is open to at least one side surface of the hood.
In addition, the muffling ventilation structure is an external hood type muffling ventilation structure installed on the outdoor side of the ventilation port penetrating the wall separating the indoor and the outdoor, the hood body is arranged outdoors, and the sleeve is a wall. It is preferably arranged so as to penetrate.
Further, the tubular body is arranged so as to project outdoors, or is buried in the wall in a state of projecting toward the wall, and the opening of the tubular body is open to at least one side surface of the hood. Is preferable.
Further, the tubular body is preferably made of a material that does not allow sound to pass through.

Further, the length in the longitudinal direction of the internal space of the tubular body from the center of the opening on one end side of the tubular body to the end on the other end side of the tubular body is Ld, and the opening in the traveling direction of the sound traveling in the hood. When the width of the part is Lo and the wavelength of the frequency of the resonance mode in which the order of the resonance mode of the hood is 1 is λ, the length in the longitudinal direction is Ld satisfying the following equations (1) and (2). It is preferable to do so.
Ld> Lo ... (1)
0.011 × λ <Ld <0.25 × λ… (2)
Further, when the width of the internal space in the direction orthogonal to the longitudinal length of the internal space of the tubular body is Lw in the cross section parallel to the traveling direction of the sound in the hood, the width Lw of the internal space is calculated by the following equation. It is preferable to satisfy (3).
0.001 × λ <Lw <0.061 × λ… (3)

Further, the area of the opening of the tubular body is S1, the total surface area of the inner surface of the internal space of the tubular body is Sd, and the tubular body is tubular from the center of the opening on one end side to the end on the other end side of the tubular body. When the length of the internal space of the body in the longitudinal direction is Ld and the wavelength of the frequency of the resonance mode in which the order of the resonance mode of the hood is 1 is λ, the ratio of the area S1 to the area Sd S1 / Sd and the longitudinal direction. It is preferable that Ld satisfies the following formulas (4) and (2).
0 <S1 / Sd <40% ... (4)
0.011 × λ <Ld <0.25 × λ… (2)

According to the present invention, ventilation is maintained in a hood-type sound deadening ventilation structure such as a ventilation hood, for example, an external hood type sound deadening ventilation structure installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors. It is possible to improve the sound deadening performance as it is, and to provide a sound absorbing material and a sound deadening ventilation structure having a higher sound deadening effect than the air column resonance structure.

It is a schematic cross-sectional view which shows an example of the sound deadening ventilation structure which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the sound pressure distribution when the sound absorbing material and the covering material are removed from the sound deadening ventilation structure shown in FIG. It is a schematic cross-sectional view which shows an example of the sound deadening ventilation structure which concerns on other embodiment of this invention. It is a schematic cross-sectional view which shows another example of the sound deadening ventilation structure which concerns on other embodiment of this invention. It is a schematic cross-sectional view which shows another example of the sound deadening ventilation structure which concerns on other embodiment of this invention. It is a schematic cross-sectional view which shows another example of the sound deadening ventilation structure which concerns on other embodiment of this invention. It is a schematic cross-sectional view which shows another example of the sound deadening ventilation structure which concerns on other embodiment of this invention. It is a schematic cross-sectional view which shows the muffling ventilation structure of a reference example. It is a schematic cross-sectional view which shows the muffling ventilation structure of the comparative example 1. FIG. It is a schematic cross-sectional view which shows the muffling ventilation structure of Example 1-1 of this invention. It is a schematic cross-sectional view which shows the muffling ventilation structure of Example 1-2 of this invention. It is explanatory drawing which shows the basic calculation model used in the Example of this invention. 6 is a graph showing the relationship between the frequency of Example 1-1, Example 1-2, Reference Example 1, and Comparative Example 1 of the present invention and the average value of the square of the absolute value of sound pressure. It is a schematic cross-sectional view which shows the muffling ventilation structure used in Example 2 of this invention. It is a schematic diagram which shows an example of the sound pressure distribution of the sound deadening ventilation structure of Example 2 (distance x = 0 mm from the maximum point of sound pressure) shown in FIG. It is a graph which shows the relationship between the frequency of the sound deadening ventilation structure of Example 2 of the present invention (distance from the maximum point of sound pressure x = 0 to 105 mm), and the average value of the square of the absolute value of sound pressure. It is a graph which shows the relationship between the distance x from the maximum point of the sound pressure of the muffling ventilation structure of Example 2 of this invention, and the average value of the square of the absolute value of the sound pressure. It is a schematic diagram of the acoustic characteristic measurement system which carries out the acoustic tube 4 microphone measurement method.

The sound deadening ventilation structure according to the present invention will be described in detail below.
The description of the constituent elements described below is based on the typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
The sound deadening ventilation structure of the first embodiment of the present invention is a hood type sound deadening ventilation structure, and is a hood body, a hood having a sleeve connected to the hood body and communicating with a space inside the hood body, and a hood body. Selectively covers at least one first opening provided in the hood, at least one second opening provided in the sleeve, a sound absorbing material provided inside the hood body, and a part of the surface of the sound absorbing material. The covering material has a covering material, and the traveling direction of the sound passing through the first opening is different from the traveling direction of the sound passing through the second opening, and the covering material is one of the other surfaces of the sound absorbing material. It is characterized in that the portion is selectively exposed and the selectively exposed portion is configured as at least one contact surface in contact with the space in the ventilation hood.

Further, the muffling ventilation structure of the second embodiment of the present invention is a hood type muffling ventilation structure, and includes a hood body and a hood provided with a sleeve connected to the hood body and communicated with a space inside the hood body. At least one tubular body having at least one first opening provided in the hood body, at least one second opening provided in the sleeve, and an opening opening into the space within the hood on at least one side surface of the hood. And a sound absorbing material provided inside the tubular body, the traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different, and the tubular body The opening is characterized in that a part of the surface of the sound absorbing material is selectively exposed, and the selective exposed part is formed as a contact surface in contact with the space in the hood.

The present invention relates to a hood-type sound deadening ventilation structure such as a ventilation hood, for example, an external hood type sound deadening ventilation structure installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors. By selectively covering a part of the sound absorbing material arranged inside, or by connecting the tubular body having the sound absorbing material inside and having an opening selectively opened to the inside of the hood, particularly the hood body. As a result, the sound deadening performance can be improved while maintaining the air permeability. As a result, sound can be efficiently absorbed by the sound absorbing material as compared with the case where the sound absorbing material is not selectively covered.
Further, since a part of the sound absorbing material is covered, a region where the sound pressure is high and a region where the sound pressure is low can be remarkably generated inside the sound absorbing material as compared with the case where the sound absorbing material is not covered. For example, the sound pressure is low in the portion behind the contact surface of the covering region. When a region with high sound pressure and a region with low sound pressure are formed, the particle velocity increases in the region between them. As the particle velocity increases in the resistor (sound absorbing material), the loss increases. Therefore, the muffling effect can be enhanced.
Although the conventional sound absorbing material does not have a sufficient effect of reducing low frequency sound, the low frequency sound is superior to the conventional one in the present invention.

According to the present invention, the sound deadening performance can be enhanced by selectively covering a part of the sound absorbing material or by directing the opening of the tubular body having the sound absorbing material inside into the hood. In the present invention, the sound absorbing material is selectively coated with a material that does not allow sound to pass through, and a part of the sound absorbing material is selectively provided with an opening, so that the particle velocity of the sound flowing into the sound absorbing material is increased, thereby forming the sound absorbing material. It is based on the principle of increasing sound absorption.
In this way, the present invention can realize a hood-type sound deadening ventilation structure such as a conventional sound absorbing material and a ventilation hood having a higher sound deadening effect than the air column resonance structure.
As a result, the muffling ventilation structure of the present invention can be applied to equipment and building materials such as ducts of equipment, ventilation sleeves, and ventilation equipment for houses.

(Silent ventilation structure)
Hereinafter, the muffling ventilation structure according to the present invention will be described in detail with reference to the preferred embodiments shown in the accompanying drawings.
(Silent ventilation structure of the first embodiment)
FIG. 1 is a cross-sectional view schematically showing an example of a muffling ventilation structure according to a first embodiment of the present invention.
The sound deadening ventilation structure 10 of the first embodiment of the present invention shown in FIG. 1 is a hood type sound deadening ventilation structure, and has a rectangular parallelepiped hood body 12 and a circular tube-shaped sleeve 14 connected to the hood body 12. A hood 16 provided, a sound absorbing material 18 attached to the inner surface of the hood body 12, a covering material 20 that selectively covers a part of the surface of the sound absorbing material 18, and a first opening 22 provided in the hood body 12. And a second opening 24 provided in the sleeve 14.
The sound deadening ventilation structure 10 is preferably provided so as to communicate the wall (for example, the outer peripheral wall, the concrete wall) 30 that separates the outdoor (external space) 26 and the indoor (internal space) 28 of a building such as a house. .. That is, it is preferable that the muffling ventilation structure 10 is provided so as to communicate with the two spaces, the outdoor 26 and the indoor 28.

(Food)
The hood 16 includes a hood body 12 and a sleeve 14 connected to the hood body 12. The sleeve 14 is connected to the hood body 12 so as to communicate with the space inside the hood body 12. The hood 16 may be installed on the outdoor side of the ventilation port penetrating the wall separating the indoor and the outdoor, for example. Further, as for the hood 16, preferably, the hood body 12 can be arranged outdoors, and the sleeve can be arranged so as to penetrate the wall 30.
The hood 16 is not particularly limited, and may be any hood as long as it is used as a ventilation hood, an external hood, or the like.

(Food body)
The hood body 12 is a hollow container having a vertically long rectangular parallelepiped shape, and a sound absorbing material 18 attached to the inner surface obtains a sound deadening effect. It is preferable that the hood body 12 protrudes from the wall 30 and is arranged outdoors 26.
A first opening 22 is provided below the hood body 12. In the example shown in FIG. 1, by providing the first opening 22 below the hood main body 12, for example, when it is arranged outdoors 26, rain or the like may fall, or dust, dust or the like may accumulate. It is preferable to be able to prevent this. One first opening 22 is provided below the hood body 12, but two or more may be provided as long as it is provided at least one below.
Above the hood body 12, an opening 13 that opens to the side surface (on the indoor 28 side) on the wall 30 side is provided. A sleeve 14 is connected to the opening 13, and a second opening 24 is provided at the tip of the sleeve 14 on the indoor side.
In the example shown in FIG. 1, one opening 13 is provided on the side surface of the hood main body 12 on the indoor 28 side, but two or more openings 13 may be provided.

That is, the sound S incident from the first opening 22 travels upward in the hood body 12. The sound S traveling upward along the middle dotted line in FIG. 1 in the hood main body 12 has the ceiling surface 12b and the left side surface 12c of the hood main body 12 blocked, and the opening 13 is opened in the right side surface of the hood main body 12 shown in FIG. Since the sleeve 14 is connected to the opening 13, the traveling direction is changed by 90 ° along the dotted line in FIG. 1, and the sleeve 14 travels to the right along the dotted line through the opening 13, and the second It exits from the opening 24. On the contrary, the sound S incident from the second opening 24 travels to the left in the sleeve 14, enters the hood body 12 through the opening 13, changes the traveling direction by 90 ° in the hood body 12, and changes the traveling direction by 90 °. It travels downward in 12 and exits from the first opening 22.
In the example shown in FIG. 1, the traveling direction of the sound S traveling through the first opening 22 and the traveling direction of the sound S traveling through the second opening 24 are different by 90 °. It is not limited to this, and may be different as many times as long as it is different. In the present invention, for example, the difference between the traveling direction of the sound S traveling through the first opening 22 and the traveling direction of the sound S traveling through the second opening 24 is 45 ° or more and 135 ° or less (45). ° to 135 °), more preferably 60 ° to 120 °, and most preferably 90 °.
In the present invention, the traveling direction of the sound S traveling through the first opening 22 can be defined as the vector direction of the acoustic intensity of the air at the center of the opening of the first opening 22, and the second opening. The traveling direction of the sound S traveling through the 24 can be defined as the vector direction of the acoustic intensity of the air at the center of the opening of the second opening 24.
Here, the direction of the particle velocity vector of sound is obtained by measuring the vector of acoustic intensity near the center of the opening surface of each opening using an acoustic particle velocity probe manufactured by Microflown Technologies.

In the example shown in FIG. 1, the hood body 12 is a hollow container having a vertically long rectangular parallelepiped shape, but the present invention is not limited thereto. The hood body 12 can be arranged outdoors 26 from the wall 30, and may be a hollow container having any shape as long as it is vertically long. For example, a rectangular parallelepiped, a cylinder, or the like can be mentioned.
The material of the hood body 12 is not particularly limited as long as it is used for a ventilation hood, an external hood, etc., and the incident sound is not amplified by vibration or the like or propagated to the outside. May be used. For example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, dichrome molybdenum, metals such as alloys thereof, acrylic resin, polymethyl methacrylate, polycarbonate, polyamided, polyarylate, polyetherimide, polyacetal. , Polyether ether ketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, triacetyl cellulose and other resin materials, carbon fiber reinforced plastics (CFRP), carbon fiber, and glass fiber reinforced. Examples include plastic (GFRP: Glass Fiber Reinforced Plastics), concrete similar to the wall material of a building, mortar, and the like.
As the hood body 12, a conventionally known ventilation hood or a hood body such as an external hood can be used as long as it is a hood body used for a hood-type sound deadening ventilation structure.

(sleeve)
The sleeve 14 has a vertically long circular tube shape, is formed of a cylindrical circular tube, is connected to the opening 13 of the hood body 12, travels in the hood body 12, is changed by a predetermined angle, and proceeds from the opening 13. The incident sound is advanced and emitted from the second opening 24 at the tip thereof, or vice versa. When the sound absorbing material 18 is attached to the inner surface of the sleeve 14, the sound absorbing material 18 obtains a sound deadening effect. The sleeve 14 is arranged so as to penetrate the wall 30.
In the example shown in FIG. 1, the sleeve 14 has a vertically long circular tube shape, but the present invention is not limited thereto. The sleeve 14 may have any shape as long as it can be arranged so as to penetrate the wall 30. For example, a rectangular parallelepiped, a cylinder, or the like can be mentioned.
The material of the sleeve 14 is not particularly limited as long as it is used for a ventilation sleeve or the like and the incident sound is not amplified by vibration or the like or propagated to the outside, and any material may be used. .. For example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, dichrome molybdenum, metals such as alloys thereof, acrylic resin, polymethyl methacrylate, polycarbonate, polyamided, polyarylate, polyetherimide. , Polyacetal, polyether ether ketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, triacetyl cellulose and other resin materials, carbon fiber reinforced plastics (CFRP), carbon fiber, and glass. Examples include fiber reinforced plastics (GFRP: Glass Fiber Reinforced Plastics), concrete similar to wall materials of buildings, mortar, and the like.
As the sleeve 14, if it is a ventilation sleeve or a sleeve used for an external hood type sound deadening ventilation structure, a conventionally known ventilation sleeve or a sleeve used for an external hood can be used.

(Sound absorbing material)
The sound absorbing material 18 absorbs sound by converting the sound energy of the sound passing through the inside into heat energy.
In the example shown in FIG. 1, the sound absorbing material 18 has an inner surface (ceiling surface 12b) of the hood body 12 facing the first opening 22 and an inner surface (side surface) of the hood body 12 facing the surface to which the sleeve 14 is connected. It is attached to 12c). In the first opening 22, the bottom surface of the sound absorbing material 18 is not completely closed. Here, the reason for attaching the sound absorbing material 18 to the ceiling surface 12b and the side surface 12c of the hood body 12 will be described in detail later, but the sound pressure is applied to the corner end 12a of the upper left corner of the hood body 12 shown in FIG. This is because there is a point that becomes the maximum of. That is, if there is a contact surface on which the sound absorbing material 18 is exposed at the point where the sound pressure is maximized, sound can be efficiently absorbed. However, the present invention is not limited to this, and if the point where the sound pressure in the hood 16 is maximized is included, the inner surface of the hood 16 or the hood body 12 excluding the first opening 22 and the opening 13 It may be pasted anywhere, it may be pasted on the entire surface, or it may be pasted anywhere on the inner surface of the sleeve 14.
The sound absorbing material 18 is not particularly limited, and conventionally known sound absorbing materials can be appropriately used. For example, foam materials such as urethane foam, soft urethane foam, wood, ceramic particle sintered material, phenol foam, and materials containing minute air; glass wool, rock wool, microfiber (3M synthetic product, etc.), floor mats, etc. Fibers such as rugs, melt blown non-woven fabrics, metal non-woven fabrics, polyester resin non-woven fabrics, metal wool, felt, insulation boards, and glass non-woven fabrics, and non-woven fabric materials; wood wool cement boards; nanofiber materials such as silica nanofibers; gypsum boards; Various known sound absorbing materials are available.

Here, the volume of the sound absorbing material 18 is not particularly limited, but if it is small, the sound deadening effect is low, and if it is large, the space inside the hood 16, that is, the hood body 12 or the sleeve 14 is narrowed, and the ventilation property is lowered. Therefore, it is preferably 1.0 to 50% of the internal volume of the hood body 12.
In the example shown in FIG. 1, the sound absorbing material 18 is an inner surface (side surface 12c) of the hood body 12 facing the surface to which the sleeve 14 is connected, and an inner surface (ceiling surface) of the hood body 12 facing the first opening 22. Although it is attached to 12b), the present invention is not limited to this, as long as the sound absorbing material 18 can obtain a sound deadening effect, the sound absorbing material 18 is a hood body 12 excluding the first opening 22 and the opening 13. It is preferable that the material is attached to an area of 50% or more of the total area of the inner surface of the above.

(Coating material)
The covering material 20 selectively covers a part of the surface of the sound absorbing material 18. As a result, the covering material 20 selectively exposes the other part (other than the covered part) of the surface of the sound absorbing material 18, and the contact surface in which the selected exposed part comes into contact with the space in the hood body 12. It is configured as 32.
In the example shown in FIG. 1, the contact surface 32 is the contact surface 32a on the left surface (near the corner end 12a in the upper left corner of FIG. 1) of the sound absorbing material 18 attached to the ceiling surface 12b of the hood body 12, and the hood. It is preferably composed of the contact surface 32b of the upper surface (near the corner end 12a of the upper left corner in FIG. 1) of the sound absorbing material 18 attached to the left side surface 12c in FIG. 1 of the main body 12.
Therefore, the covering material 20 covers the surface of the sound absorbing material 18 except for the two contact surfaces 32a and 32b.
Here, the contact surface 32 preferably occupies an area of 1.0% to 50% with respect to the total area of the surface of the sound absorbing material 18. The reason is that if the contact surface 32 has an area within this range, the sound deadening effect can be improved as compared with the conventional case in which the entire surface area of the sound absorbing material 18 is not covered with the covering material 20 at all. ..
In the present invention, since it is difficult to make a strict calculation of the sound absorbing material 18 such as when the surface is uneven, the area of the contact surface 32 of the sound absorbing material 18 is defined as the area of the opening portion of the covering material 20. To do. Here, the area of the opening portion of the covering material 18 is defined as the area of a plane including the opening frame of the covering material 20 or a surface approximated by a smooth curved surface. The area of the opening portion of the covering material 18 may be calculated by the same method as the conventionally known area calculation method described above.

By the way, FIG. 2 is a schematic view showing a sound pressure distribution when the sound absorbing material 18 and the covering material 20 are removed from the sound deadening ventilation structure 10 shown in FIG. 1 (see FIG. 8 described later). In this sound pressure distribution, in the sound deadening ventilation structure 50 shown in FIG. 8 to be described later, a sound having a frequency of 300 Hz enters the hood body 12 from the first opening 22, travels in the hood body 12, and travels from the opening 13 to the sleeve 14. This is the sound pressure distribution when entering, traveling through the sleeve 14, and exiting from the second opening 24. Further, this sound pressure distribution represents the sound pressure level of a sound having a frequency of 300 Hz (the logarithm log ₁₀ (| p |) of the absolute value of the sound pressure) in terms of density. Both the horizontal axis and the vertical axis represent the coordinates (distance) of the coordinate system with 0 as the origin in FIG.
As shown in FIG. 2, when the sound entering the hood body 12 from the first opening 22 propagates in the hood body 12, the side surface 12c of the hood body 12 facing the opening 13 and the ceiling surface of the hood body 12 The corner end portion (upper left corner portion in the hood body 12) 12a in contact with 12b becomes the maximum sound pressure. That is, in the case of the sound deadening ventilation structure 50 (see FIG. 8) in which the sound absorbing material 18 is not arranged, the upper left corner end portion 12a is the maximum point p _{max of the} sound pressure. Note that FIG. 2 also shows that the opening of the tubular body 42, which will be described later, may be arranged in the vicinity _{of the maximum sound pressure point p max.}

In this case, the sound deadening effect is enhanced when the surface of the sound absorbing material 18 is close to the position of the _{maximum point p max.} Therefore, when the sound absorbing material 18 is arranged in the hood body 12, if the surface of the sound absorbing material 18 is located near the portion where the sound pressure is high, the sound is efficiently absorbed by the sound absorbing material 18 and the sound deadening effect is enhanced. In particular, for sound having a frequency that easily passes through the muffling ventilation structure 50 (see FIG. 8), the sound pressure increases at the corner end 12a in the upper left corner, so that the surface of the sound absorbing material 18 comes to the corner 12a. It is preferable to place it like this.
Therefore, it is preferable that the contact surfaces 32 (32a and 32b) of the sound absorbing material 18 are provided in the vicinity of the corner end portion 12a of the upper left corner of the hood body 12. By doing so, the sound absorbing material 18 can be arranged at the position of the maximum point of the sound pressure to efficiently absorb sound, and a high sound deadening effect can be obtained.

Dressing 20 is preferably a material made of a material impervious to sound. The reason is that the sound is strongly absorbed at the point where the sound pressure of the corner end portion 12a of the upper left corner of the hood body 12 is maximized. In the present invention, the sound-impermeable material has a configuration in which a material in a used state, for example, a plate-shaped material having the same thickness as the covering material 20 used, is installed so as to block all the waveguides of the acoustic tube. is defined as the material of the material is transmission loss 5dB or more over 250Hz~4000Hz when evaluated at 4 microphone technique. The frequency is set to 250 Hz to 4000 Hz because it is 250 to 4000 Hz that can be stably measured by the acoustic tube measurement.
In the 4-microphone method, as in the acoustic characteristic measurement system 60 shown in FIG. 18, a sound insulating material 70 used as a covering material 20 is arranged in an aluminum acoustic tube (tube body 62), and the acoustic tube (tube body 62) is arranged. The acoustic characteristics are measured by the transfer function method using four microphones 64 arranged in the tube body 62).

This method follows "ASTM E2611-09: Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method". As the acoustic tube, for example, an aluminum tube body 62 is used as the one having the same measurement principle as WinZac manufactured by Nippon Acoustic Engineering Co., Ltd. (For WinZac, the web document "https://www.noe.co. You can refer to "jp / en / download / pdf / winzac.pdf".). A cylindrical box 68 containing the speaker 66 was arranged below the tube 62, and the tube 62 was placed on the upper surface of the box 68. Sound of a predetermined sound pressure is output from the speaker 66, and measurement is performed with four microphones 64. In this way, the acoustic transmission loss can be measured in a wide spectral band.
Specifically, using this method, a material 70 made of a sound-impermeable material is arranged as shown in FIG. 18 so as to block an acoustic tube (tube body 62) having a diameter of 4 cm without a gap, and measurement is performed. The transmittance T can be obtained, and the transmission loss TL = 10 * log ₁₀ (1 / T) can be obtained. As described above, the value of the transmission loss TL is, is defined as a material of a material with a sound insulation shall be 5dB or more over 250Hz～4000Hz.

The covering material 20 made of a sound-impermeable material may be any material as long as it is a material that does not transmit sound. For example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, dichrome molybdenum, alloys thereof, etc. Metallic materials, acrylic resin, polymethyl methacrylate, polycarbonate, polyamided, polyarylate, polyetherimide, polyacetal, polyether etherketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, triacetyl cellulose Resin materials such as carbon fiber reinforced plastics (CFRP: Carbon Fiber Reinforced Plastics), carbon fibers, and glass fiber reinforced plastics (GFRP: Glass Fiber Reinforced Plastics), concrete similar to wall materials of buildings, mortar, etc. Can be done.

In the present invention, the contact surface 32 (32a, 32b) preferably has a center position such that the wavelength of the resonance mode frequency of the hood 16 (particularly, the hood body 12) is λ, 100 Hz or more, and the frequency in the audible range. When the order of the resonance mode is n = 1, 2, ... (Positive integer) from the lower frequency side and the wavelength corresponding to the frequency of the nth resonance mode is λn, the hood 16 (particularly, the hood body 12) ) Is preferably within the range of λn / 16 from the point where the sound pressure is maximized.
In the present invention, the wavelength λ corresponds to the wavelength of the resonance mode frequency of the hood 16. The frequency of the resonance mode is defined as the sound pressure is measured in the indoor 28 space on the side of one of the hoods 16 (for example, the first opening 22) and the other outlet (for example, the second opening 24). It corresponds to the peak (maximum) frequency at the time of. Specifically, the frequency of the resonance mode of the hood is for measuring the sound pressure at a position 50 cm from the outlet on one side of the hood, generating white noise from the speaker at a distance of 50 cm, and measuring the sound pressure at a position 50 cm from the outlet on the other side. It is defined as the frequency at which the observed sound pressure is maximized when the frequency spectrum of the sound pressure is measured by measuring with a microphone. At this time, the order of the resonance mode is defined as n = 1, 2, ... (Positive integer) from the lower frequency side. The reason for these is that the sound having the wavelength λ of the resonance mode and the wavelength corresponding to the audible range becomes a sound that is easy to come out, so it becomes a sound that must be eliminated, and the contact surface 32 has a sound pressure. This is because the sound deadening effect is higher when the sound is closer to the maximum point, and the sound deadening effect is weaker when the sound pressure is farther from the maximum point.

Further, the contact surface 32 (32a, 32b) preferably has a center position of the nth-order resonance mode wavelength λn, and at a wavelength corresponding to the audible range, the corner end portion 12a in the hood body 12 Preferably, within the range of λn / 16 from the corner end 12a in the hood body 12 corresponding to the point at which the traveling direction of the sound passing through the first opening 22 and the traveling direction of the sound passing through the second opening 24 bend. It is preferable to be present in. The reason is that the sound deadening effect is higher when the contact surface 32 is closer to the corner end portion 12a in the hood body 12 where the maximum sound pressure is reached.
Here, the positive integer n, which is the order of the resonance mode, is preferably 3 or less. That is, in particular, among the sounds having the wavelength λ of the resonance mode and corresponding to the wavelength corresponding to the audible range, the sound having a relatively low frequency such as the order n = 1, 2, 3 of the resonance mode is omitted. This is because it is easier to hear and the low frequency sound needs to be turned off. Moreover, there is a problem that the low frequency sound is difficult to be easily erased by the sound absorbing material 18.
The muffling ventilation structure of the first embodiment of the present invention is basically configured as described above.

(Silent ventilation structure of the second embodiment)
FIG. 3 is a cross-sectional view schematically showing an example of a muffling ventilation structure according to a second embodiment of the present invention.
In the sound deadening ventilation structure 40 of the second embodiment of the present invention shown in FIG. 3, the sound deadening ventilation structure 10 of the first embodiment of the present invention shown in FIG. 1 and the sound absorbing material 18 are attached to the inner surface of the hood body 12. Since they have the same configuration except that they have a tubular body 42, the same components are numbered the same, and detailed description thereof will be omitted.
The sound deadening ventilation structure 40 of the present embodiment is a hood type sound deadening ventilation structure, and includes a rectangular hood body 12, a hood 16 having a circular tube-shaped sleeve 14 connected to the hood body 12, and a hood body 12. Two tubular bodies 42 (42a and 42b) having openings 44 that open into the inner space, a sound absorbing material 18 provided inside the tubular bodies 42 (42a and 42b), and a hood body 12 are provided. It has a first opening 22 and a second opening 24 provided in the sleeve 14.
Similar to the sound deadening ventilation structure 10, the sound deadening ventilation structure 40 also has a wall (for example, an outer peripheral wall, concrete) that separates the outdoor (external space) 26 and the indoor (internal space) 28 of a building such as a house, referring to FIG. It is preferable that the wall) 30 is provided so as to communicate with the wall. That is, the muffling ventilation structure 10 is preferably provided so as to communicate the two spaces, the outdoor 26 and the indoor 28.

(Tubular body)
In the example shown in FIG. 3, the tubular bodies 42a and 42b of the two tubular bodies 42 are the inner surface of the ceiling surface 12b in the hood body 12, and the side surface on the left side (for example, the outdoor 26 side (see FIG. 1)). It is arranged so as to be in contact with the inner surface of 12c. The longitudinal length of the tubular body 42a is equal to the length of the inner surface of the ceiling surface 12b of the hood body 12, and the longitudinal length of the tubular body 42b is the longitudinal length of the inner surface of the hood body 12 (side surface 12c). Equal to length).
The tubular bodies 42a and 42b each have an opening 44 that selectively opens into the space inside the hood body 12.
The inside of the tubular body 42 (42a and 42b) is filled with a sound absorbing material 18. The bottom surface of the sound absorbing material 18 at the position of the first opening 22 is completely closed by the bottom surface of the tubular body 42b.
The openings 44 (44a and 44b) of the tubular bodies 42 (42a and 42b) are located at the corner ends 12a in the upper left corner of the hood body 12. The opening 44a of the tubular body 42a is located above the corner end 12a in the upper left corner of the hood body 12. The opening 44b of the tubular body 42b is located on the left side of the corner end 12a in the upper left corner of the hood body 12. The openings 44 (44a and 44b) selectively expose a part of the surface of the sound absorbing material 18 from the tubular body 42, and the contact surface that contacts the exposed part of the sound absorbing material 18 with the space in the hood body 12. It is configured as 32 (32c and 32d).

By the way, it can be said that the side surface of the tubular body 42 that comes into contact with the space inside the hood body 12 constitutes the covering material 20. Here, the tubular body 42 is preferably made of a material that does not allow sound to pass through.
Here, the shape of the tubular body 42 is not particularly limited as long as it can be arranged at a predetermined position in the hood body 12, has an opening 44, and can be filled with the sound absorbing material 18. Examples of the shape of the tubular body 42 include a quadrangular prism tube shape, a circular tube shape, a labyrinth shape, and the like.
Further, the material of the tubular body 42 is not particularly limited as long as it can be filled with the sound absorbing material 18. The material of the tubular body 42 is preferably a material that does not allow sound to pass through, for example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, dichrome molybdenum, metal materials such as alloys thereof, acrylic resin, and the like. Resin materials such as polymethyl methacrylate, polycarbonate, polyamide id, polyarylate, polyetherimide, polyacetal, polyether ether ketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, triacetyl cellulose, carbon fiber Examples thereof include reinforced plastics (CFRP: Carbon Fiber Reinforced Plastics), carbon fibers, and glass fiber reinforced plastics (GFRP: Glass Fiber Reinforced Plastics), concrete and mortar similar to wall materials of buildings.

Since the position of the opening 44 of the tubular body 42 and the center position thereof are equal to the position in the longitudinal direction of the contact surface 32 and the center position thereof, also in the sound deadening ventilation structure 40 of the second embodiment of the present invention. Similar to the muffling ventilation structure 10 of the first embodiment of the present invention, the wavelength λ of the resonance mode satisfies λ = 2L / n, and at the wavelength corresponding to the audible range, λ from the maximum point of the sound pressure in the hood 16. It is preferably within the range of / 8, or is preferably within the range of λ / 8 from the corner end 12a of the upper left corner of the hood body 12 of the hood 16. The reason is that the sound deadening effect is higher when the opening 44 (that is, the contact surface 32) of the tubular body 42 is closer to the maximum sound pressure point, and the sound deadening effect is weaker when the opening 44 (that is, the contact surface 32) is away from the maximum sound pressure point. ..
Further, the positive integer n is preferably 3 or less. The reason is that the sound of a relatively low frequency of 3 or less, which has a low order of resonance mode, is likely to come out, and therefore it is necessary to positively eliminate it.
In the example shown in FIG. 3, two tubular bodies 42a and 42b are arranged on the ceiling surface 12b in the upper left corner and the left side surface 12c in the hood body 12, but the opening 44 (contact surface 32) of the tubular body 42. ) Is within the range of λn / 16 from the maximum point of the sound pressure in the hood 16 or the corner end 12a in the upper left corner of the hood body 12 in the hood body 12, or 3 or more. The tubular body 42 may be arranged at any position including the maximum point of sound pressure in the hood 16 or the corner end 12a in the upper left corner of the hood body 12.
Further, it is preferable that the area of the contact surface and the volume of the sound absorbing material are defined in the same manner as in the sound deadening ventilation structure 10 of the first embodiment of the present invention.

In the muffling ventilation structure 40 shown in FIG. 3, the tubular bodies 42 (42a, 42b) are arranged in the hood body 12, but the present embodiment is not limited to this, as in the muffling ventilation structure 40A shown in FIG. The tubular body 42 (42a, 42b) may be arranged outside the hood body 12.
In the sound deadening ventilation structure 40A, the side surfaces of the tubular bodies 42a and 42b are arranged outside the hood body 12, above the ceiling surface 12b of the hood body 12, and outside the left side surface 12c, respectively. ..
The openings 44 (44a, 44b) of the tubular bodies 42 (42a, 42b) have a ceiling surface 12b in FIG. 4 with respect to the corner end 12a of the upper left corner of the hood body 12, which is the maximum point of the sound pressure of the hood 16. It opens on the left side and on the ceiling side of the left side surface 12c. The surface of the sound absorbing material 18 in the tubular body 42 (42a, 42b) constitutes the contact surface 32 (32a, 32b) at the opening 44 (44a, 44b).
In the sound deadening ventilation structure 40A shown in FIG. 4, the opening 44a of the tubular body 42a is located at the corner end 12a (within the range of λn / 16) in the upper left corner of the hood body 12, and the opening 44b of the tubular body 42b is also located. , At the corner end 12a (within the range of λn / 16) in the upper left corner of the hood body 12. The reason is that the sound deadening effect is higher when the opening 44 (that is, the contact surface 32) of the tubular body 42 is closer to the maximum sound pressure point, and the sound deadening effect is weaker when the opening 44 (that is, the contact surface 32) is away from the maximum sound pressure point. ..
However, this embodiment is not limited to the above configuration, and the position of the opening 44 (contact surface 32) of the tubular body 42 is the maximum point of the sound pressure in the hood 16, or the corner end of the upper left corner of the hood body 12. Within the range of 12a to λn / 16, one or more tubular bodies 42 include the maximum point of sound pressure in the hood 16 or the corner end 12a in the upper left corner of the hood body 12. It may be arranged at any position, or at least one tubular body 42 of two or more tubular bodies 42 may be arranged inside the hood body 12, and at least one remaining tubular body 42 may be arranged outside the hood body 12. Is also good.

For example, as in the sound deadening ventilation structure 40B shown in FIG. 5, a tubular body 42c having a smaller longitudinal size with respect to the hood body 12 is externally attached with the longitudinal direction aligned with respect to the hood body 12 to the outside of the hood 16. You may place it. Further, as in the sound deadening ventilation structure 40B shown in FIG. 6, a tubular body 42d having a small size in the longitudinal direction with respect to the hood body 12 is inserted in the hood body 12 with the longitudinal direction aligned and arranged in the hood 16. You may. Also in the tubular bodies 42c and 42d, the respective openings 44 are arranged at any position including the maximum point of sound pressure in the hood 16 or the corner end 12a in the upper left corner in the hood body 12. Is preferable.

Further, as in the sound deadening ventilation structure 40D shown in FIG. 7, the tubular bodies 46 (46a, 46b) are arranged outside the hood 16 so that their longitudinal directions coincide with the longitudinal directions of the hood body 12, and are side-branched. May be. At this time, the tubular body 46a projects outward (upper side in FIG. 7) on the ceiling surface 12b including the corner end portion 12a on the ceiling side in the hood body 12 of the hood 16 so as to be orthogonal to the ceiling surface 12b. Further, the tubular body 46b projects outward (upper side in FIG. 7) on the ceiling surface 14a of the sleeve 14 of the hood 16 so as to be orthogonal to the ceiling surface 14a of the sleeve 14.
The opening 48 of the tubular body 46 (46a, 46b) is open to the ceiling surface 12b of the hood body 12 of the hood 16 and the ceiling surface 14a of the sleeve 14. The surface of the sound absorbing material 18 in the tubular body 46 (46a, 46b) constitutes a contact surface 32 at the opening 48.

In the sound deadening ventilation structure 40D shown in FIG. 7, the opening 48 (contact surface 32) of the tubular body 46a is located near the maximum sound pressure point (within the range of λn / 16) in the hood 16 (hood body 12). Alternatively, the opening 48 (contact surface 32) of the tubular body 46b is located in the vicinity of the corner end 12a (within the range of λn / 16) in the upper left corner of the hood body 12, and the opening 48 (contact surface 32) is inside the hood 16 (hood body 12). It is near the other maximum points of sound pressure (within the range of λn / 16). That is, it is preferable that the opening 48 (contact surface 32) of the tubular body 46 (46a, 46b) is within the range of λn / 16 from the maximum point of sound pressure. The reason is that the sound deadening effect is higher when the opening 48 (contact surface 32) of the tubular body 46 (46a, 46b) is closer to the maximum point of sound pressure. Further, the positive integer n is preferably 3 or less. The reason is that the sound of a relatively low frequency of 3 or less, which has a low order of resonance mode, is likely to come out, and therefore it is necessary to positively eliminate it.

However, the present embodiment is not limited to the above configuration, and the position of the opening 48 (contact surface 32) of the tubular body 46 is the maximum point (belly) of the sound pressure in the hood body 12, or the upper left in the hood body 12. If it is within the range of λn / 16 from the corner end 12a, one or three or more tubular bodies 46 can be attached to the ceiling surface 12b in the hood body 12 of the hood 16, or the left side surface 12c, the sleeve 14. It may be projected outward so as to be orthogonal to the ceiling surface 14a of the.
Further, the tubular body 42 and the tubular body 46 may be used in combination, or the sound absorbing material 18 and the covering material 20 of the sound deadening ventilation structure of the present embodiment may be used in combination, and the tubular body 42 and the tubular body 46 may be used in combination.

Further, in the second embodiment of the present invention, for example, as shown in FIGS. 6 and 7, in the longitudinal direction of the internal space of the tubular body 42 of the sound deadening ventilation structure 40C and the tubular body 46 of the sound deadening ventilation structure 40D. Assuming that the length is Ld and the width of the opening 44 (contact surface 32) of the tubular body 42 and the opening 48 (contact surface 32) of the tubular body 46 in the direction of sound wave traveling in the hood 16 is Lo, the tubular body The longitudinal length Ld of the internal spaces of 42 and 46 is larger than the width Lo of the openings 44 and 48 (contact surface 32), respectively.
That is, the length Ld preferably satisfies the following formula (1).
Ld> Lo ... (1)

Here, the length in the longitudinal direction of the internal space of the tubular bodies 42 and 46 can be said to be the length of the sound wave in the internal space of the tubular bodies 42 and 46 in the longitudinal direction, and can be obtained by simulation. it can.
In the example shown in FIG. 6, since the internal space of the tubular body 42 extends in the longitudinal direction thereof (hence, the traveling direction of the sound wave in the hood 16), the traveling direction of the sound wave in the internal space is tubular. It is the longitudinal direction of the internal space of the body 42 (that is, the traveling direction of the sound wave in the hood 16, and thus the vertical direction in the figure). Therefore, the length Ld is the other end side of the tubular body 42 from the center position of the opening 44 (contact surface 32) on one end side (upper side in the drawing) of the tubular body 42 in the longitudinal direction of the internal space of the tubular body 42. It is the length to the end (the end face of the internal space). When the length of the internal space of the tubular body 42 in the longitudinal direction differs depending on the position, the length Ld is an average value of the lengths at each position.
When the width of the opening 44 (contact surface 32) differs depending on the position, the width Lo of the opening 44 (contact surface 32) is an average value of the widths at each position.

Further, in the example shown in FIG. 7, since the internal space of the tubular body 46 projects in a direction orthogonal to the ceiling surface of the hood body 12 and the sleeve 14, the traveling direction of the sound wave in the internal space is the projecting direction. (Upper and lower direction in the figure). Therefore, the length Ld is the length from the opening 48 (contact surface 32) in the protruding direction to the upper end surface of the internal space. When the length of the internal space of the tubular body 46 in the longitudinal direction differs depending on the position, the length Ld is the average value of the depths at each position.
When the width of the opening 48 differs depending on the position, the width Lo of the opening 48 is an average value of the widths at each position.

Further, the wavelength of the frequency of the resonance mode in which the order of the resonance mode of the muffling ventilation structure 40C and the hood 16 of the 40D is 1 (n = 1) (that is, the wavelength of the sound wave at the resonance frequency of the first resonance (n = 1)). ) Λ (= λ1), the longitudinal length Ld of the internal spaces of the tubular bodies 42 and 46 satisfies 0.011 × λ <Ld <0.25 × λ.
That is, it is preferable that the length Ld also satisfies the following equation (2).
0.011 × λ <Ld <0.25 × λ… (2)
As can be seen from the above equation (2), the length Ld is smaller than λ / 4, and the tubular bodies 42 and 46 are not silenced by resonance.
The length Ld more preferably satisfies 0.016 × λ <Ld <0.25 × λ, and further preferably 0.021 × λ <Ld <0.25 × λ.

When the sound of the lowest resonance frequency (n = 1) of the hood 16 is muted by using the resonance type tubular body, the length of at least 1/4 of the wavelength λ of the resonance frequency is required, and the tubular body must have a length of at least 1/4. The size will increase. Therefore, there is a problem that it is difficult to achieve both high breathability and soundproofing performance.
Further, the resonance type tubular body selectively mutes sound of a specific frequency (frequency band). Therefore, it is necessary to design the hood 16 according to the resonance frequency, and there is a problem that the versatility is low.
Further, the resonance of the hood 16 occurs at a plurality of frequencies, but the resonance type tubular body silences the sound of a specific frequency. Therefore, there is a problem that the resonance sound to be muted is only one frequency, and the resonance sound of other frequencies cannot be muted because the frequency band in which the resonance type tubular body is muted is narrow.

On the other hand, in the present embodiment, the length Ld in the longitudinal direction of the internal space in the tubular body 42 and 46 is the width of the openings 44 and 48 in the traveling direction of the sound traveling in the hood 16. Assuming that the wavelength of the sound wave at the resonance frequency of the first resonance (n = 1) of the hood 16 is λ, which is larger than Lo, the length Ld in the longitudinal direction of the internal space is based on the above equations (1) and (2). The inside of the tubular bodies 42 and 46 to be filled is connected to the sound field space of the first resonance of the hood 16 and arranged.
The tubular bodies 42 and 46 have sound energy due to the viscosity of the fluid in the vicinity of the wall surfaces of the tubular bodies 42 and 46, the unevenness (surface roughness) of the wall surface, and the sound absorbing material 18 and the like arranged in the tubular bodies 42 and 46. Is converted into heat energy to mute the sound. The viscosity of the fluid in the vicinity of the wall surface, the unevenness (surface roughness) of the wall surface, and the sound absorbing material 18 arranged in the tubular body 42 and 46 can be said to be an energy conversion mechanism.

Here, the sound waves in the hood 16 are tubular because the width Lo of the openings 44 and 48 of the tubular bodies 42 and 46 is smaller than the longitudinal length Ld of the internal space of the tubular bodies 42 and 46. When flowing into the body 46, the moving speed of gas (air) molecules increases while maintaining the sound pressure. The conversion efficiency from sound energy to thermal energy by the above-mentioned conversion mechanism depends on the sound pressure and the moving speed of gas molecules. Therefore, as the moving speed of gas molecules increases while maintaining the sound pressure, the conversion efficiency from sound energy to thermal energy by the above-mentioned conversion mechanism increases.
Since the principle of this sound deadening does not depend on the wavelength of the sound wave, the longitudinal length Ld of the internal space of the tubular bodies 42 and 46 is smaller than 1/4 of the wavelength λ at the resonance frequency of the first resonance of the hood 16. However, high soundproofing performance can be exhibited. Therefore, it is possible to obtain high soundproofing performance while maintaining the air permeability of the hood 16 by downsizing the tubular bodies 42 and 46.
Further, since the principle of sound deadening by the tubular bodies 42 and 46 does not depend on the wavelength of the sound wave, soundproofing performance can be exhibited even if the length and shape of the hood 16 (hood body 12 and sleeve 14) are different. It is possible, and it is highly versatile because it does not require a design that matches the hood 16.
Further, since the principle of muffling by the tubular bodies 42 and 46 does not depend on the wavelength of the sound wave, it is possible to mute the sound in a wide frequency band.

Further, as described above, from the viewpoint of soundproofing performance and breathability, the length Ld of the internal spaces of the tubular bodies 42 and 46 in the longitudinal direction is determined by the above equation (2) (that is, 0.011 × λ <Ld <. 0.25 × λ) is preferably satisfied, 0.016 × λ <Ld <0.25 × λ is more preferable, and 0.021 × λ <Ld <0.25 × λ is satisfied. Is more preferable.
Further, when the width of the internal space in the direction orthogonal to the longitudinal length of the internal spaces of the tubular bodies 42 and 46 is Lw in the cross section parallel to the traveling direction of the sound in the hood 16, the internal space of the tubular bodies 42 and 46. The width Lw preferably satisfies the following formula (3).
0.001 × λ <Lw <0.061 × λ… (3)
The width Lw of the internal space of the tubular bodies 42 and 46 more preferably satisfies 0.001 × λ <Lw <0.051 × λ, and 0.001 × λ <Lw <0.041 × λ. It is more preferable to meet. In FIG. 7, the width Lw of the internal space is the length in the left-right direction in the drawing, and coincides with the width Lo of the opening 48 (contact surface 32).

Further, in the present embodiment, the ratio S1 / Sd of the area S1 of the opening 44 and 48 to the surface area Sd of the inner wall of the inner space of the tubular body 42 and 46 is set to 0 <S1 / Sd <40%. By reducing the ratio of the area of the surface on which the sound wave is incident to the surface area of the conversion mechanism of the sound absorbing material 18 or the like, the gas molecule corresponding to the sound wave flowing into the conversion mechanism of the sound absorbing material 18 or the like while maintaining a high sound pressure P. The moving speed of the can be increased to improve the soundproofing performance.
From the viewpoint of increasing the moving speed of gas molecules, it is preferable that the area S1 (ratio S1 / Sd) of the openings 44 and 48 is small, but if the areas S1 of the openings 44 and 48 are too small, sound waves enter the internal space. Since it becomes difficult to flow in, the soundproofing performance becomes low. From the above viewpoint, the areas S1 of the openings 44 and 48 with respect to the surface area Sd of the inner wall of the internal space are preferably 0.1% <S1 / Sd <40%.
That is, the ratio S1 / Sd of the area S1 to the area Sd preferably satisfies the following formula (4).
0 <S1 / Sd <40% ... (4)
The ratio S1 / Sd is more preferably 0.3% <S1 / Sd <35%, and more preferably 0.5% <S1 / Sd <30%.
The surface area Sd of the inner wall of the internal space is measured with a resolution of 1 mm. That is, when it has a fine structure such as unevenness of less than 1 mm, the surface area Sd may be obtained by averaging this.
The muffling ventilation structure of the second embodiment of the present invention is basically configured as described above.

The sound deadening ventilation structure of the present invention will be specifically described with reference to Examples.
The materials, dimensions, amounts used, proportions, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the examples shown below.

(Reference example)
First, the hood-type sound deadening ventilation structure 50 of the comparative example shown in FIG. 8 to which the sound absorbing material and the covering material are not attached at all was produced as a two-dimensional simulation structure.
As shown in FIG. 8, the hood body 12 of the hood 16 is composed of an ideal rigid plate having no thickness, has a length of 186 mm in the longitudinal direction (longitudinal direction) and a length of 95 mm in the width direction (thickness direction). It had a vertically long rectangular parallelepiped shape. In this embodiment, since it is a two-dimensional simulation, the thickness is not assumed. An ideal rigid plate is a plate that completely reflects sound. Also, since it is a two-dimensional simulation, the depth direction is not considered.
The sleeve 14 was made of an ideal rigid plate having no thickness, and had a rectangular parallelepiped shape having a height of 100 mm and a length of 200 mm. The opening 13 to which the sleeve 14 is connected was a rectangular opening having a height of 100 mm from a position 48 mm from the bottom surface along the longitudinal direction of the hood body 12.

(Comparative Example 1)
Next, on the inner surface of the side surface 12c facing the opening 13 of the hood body 12 of the sound deadening ventilation structure 50 of the reference example shown in FIG. 8 and the inner surface of the ceiling surface 12b, a flow resistance of 20000 [Pa · S / m] having a thickness of 20 mm. ² ] The sound absorbing material 18 made of glass wool was attached, and the hood-type sound deadening ventilation structure 52 of Comparative Example 1 shown in FIG. 9 was produced as a two-dimensional simulation structure.

(Example 1-1)
Next, a part of the surface of the sound absorbing material 18 attached to the inner surface of the side surface 12c of the hood body 12 of the sound deadening ventilation structure 52 of Comparative Example 1 shown in FIG. 9 and the inner surface of the ceiling surface 12b is ideally formed without thickness. The hood-type sound deadening ventilation structure 10 of Example 1-1 of the present invention shown in FIG. 10 was produced as a two-dimensional simulation structure by covering with a covering material 20 of a rigid body plate. The hood-type muffling ventilation structure 10 of Example 1-1 shown in FIG. 10 is the same as the hood-type muffling ventilation structure 10 of the first embodiment of the present invention shown in FIG. 1, except that specific dimensions are included. It is the same. Since it is a two-dimensional simulation, it is an ideal rigid plate with no thickness, but concrete assumptions include, for example, stainless steel with a thickness of 1 mm.
The covering material 20 covers the surface of the sound absorbing material 18 attached to the ceiling surface 12b of the hood body 12 of the sound deadening ventilation structure 10 shown in FIG. 10 with a space of 40 mm from the upper left corner to the right side of the surface of the sound absorbing material 18. The surface of the sound absorbing material 18 attached to the side surface 12c of the hood body 12 was covered with a space of 40 mm below the upper left corner of the surface of the sound absorbing material 18. The end of the sound absorbing material 18 attached to the inner surface of the ceiling surface 12b of the hood body 12 of the sound deadening ventilation structure 10 of Example 1-1 shown in FIG. 10 is a side surface opposite to the side surface 12c. Since it is completely closed by the above, it can be regarded that the tubular body 42 (42a) is inserted in contact with the inner surface of the ceiling surface 12b of the hood body 12.
As a result, the contact surface 32a in contact with the space of the hood body 12 on the ceiling surface 12b of the hood body 12 of the sound deadening ventilation structure 10 shown in FIG. 1 was the surface of the sound absorbing material 18 having an area of 40 mm in the width direction. The contact surface 32b on the side surface 12c of the hood body 12 that contacts the space of the hood body 12 was the surface of the sound absorbing material 18 having an area of 40 mm in the longitudinal direction.

(Example 1-2)
Next, the bottom surface of the sound absorbing material 18 attached to the inner surface of the side surface 12c of the hood body 12 of the sound deadening ventilation structure 10 of Example 1-1 shown in FIG. 10 (the bottom surface of the sound absorbing material 18 at the position of the first opening 22). ) Was covered with the covering material 20 and closed, and the hood-type sound deadening ventilation structure 11 of Example 1-2 of the present invention shown in FIG. 11 was produced as a two-dimensional simulation structure. In the sound deadening ventilation structure 11, a tubular body 42 (42b) composed of a side surface 12c, an opposing covering material 20, a covering material 20 with the bottom surface closed, and orthogonal side surfaces on both sides of the side surface 12c is formed on the inner surface of the side surface 12c of the hood body 12. It can be regarded as having been inserted in contact with.

The basics of the muffling ventilation structure 10 of Example 1-1, the muffling ventilation structure 10 of Example 1-2, the muffling ventilation structure 50 of Reference Example, and the muffling ventilation structure 52 of Comparative Example 1 produced in this manner are shown in FIG. Using a two-dimensional calculation model, simulation calculation was performed by the finite element method using the acoustic module of the finite element method calculation software COMSOL Multiphysics ver.5.3 (COMSOL).
Using such a simulation model, as shown in FIG. 12, sound waves were incident from the outside of a hemispherical surface (radius 1 m) in one (lower) space partitioned by a wall. The incident sound wave was incident into the hood body 12 through the first opening 22 of the muffling ventilation structure 10. Next, the sound wave incident on the hood body 12 was emitted from the second opening 24 into the other (right side) space. As a result, sound waves reaching a quarter spherical surface (radius 1 m) in the space on the right side were detected.
Thus, the square of the sound pressure _{p i} measured m points at each position of 1/4 spherical surface of the right side of the space (i), the absolute value of the sound pressure _{p i |} below the ^second average value asp ^| p i It was calculated by the formula (5). m is the number of measurement points.

When the sound pressure p is given as a function of the 1/4 arc (l), the square | p | ² of the absolute value of the sound pressure is integrated along the 1/4 arc (l) and described below. The line integral value isp of the square of the absolute value of the sound pressure represented by the equation (6) is obtained.
The sound represented by the following equation (7) is obtained by dividing the line integral value isp of the square of the absolute value of the sound pressure obtained in this way by the length L (= πr / 2) of the 1/4 arc of the radius r. The average value asp of the square of the absolute value of the pressure | p | ^{2 may be calculated.}

ａｓｐ＝ｉｓｐ／（πｒ／２）＝２×ｉｓｐ／（πｒ） …（７）

asp = isp / (πr / 2) = 2 × isp / (πr)… (7)

FIG. 13 shows the average value asp of the square of the absolute value of the sound pressure with respect to the frequency of Example 1-1, Example 1-2, Reference Example, and Comparative Example 1 thus obtained.
As is clear from FIG. 13, Examples 1-1 and 1-2 have an average of the squares of the absolute values of sound pressure in the range of 200 Hz to 700 Hz as compared with Reference Example and Comparative Example 1. It can be seen that the value asp is small, the incident sound can be reduced, and the sound can be muted. From these results, it was shown that the sound deadening ventilation structure of the present invention is superior in sound deadening effect as compared with the case where the conventional sound absorbing material 18 is simply installed (Comparative Example 1).
Therefore, it can be said that the effectiveness of the present invention was shown.

(Example 2)
The hood-type sound deadening ventilation structure 10A of Example 2 shown in FIG. 14 was produced as a two-dimensional simulation structure, respectively. In the sound deadening ventilation structure 10A shown in FIG. 14, the surface of the sound absorbing material 18 attached to the ceiling surface 12b of the hood body 12 in the hood type sound deadening ventilation structure 10 of Example 1-1 shown in FIG. 10 is completely closed. There is no contact surface 32a, and the position on the upper side of the contact surface 32b in the longitudinal direction is located on the surface of the sound absorbing material 18 attached to the ceiling surface 12b in the longitudinal direction of the hood body 12, whereas it is located x mm below. It was different in that it was supposed to be. The bottom surface of the sound absorbing material 18 at the position of the first opening 22 is completely closed.
Therefore, it can be said that Example 2 in which x = 0 mm is the same as the sound deadening ventilation structure 10 of Example 1-1 shown in FIG.
Next, the distance x from the surface of the sound absorbing material 18 on the ceiling surface 12b of the hood body 12 to the upper end of the contact surface 32b is changed from 0 mm to 5 mm, 25 mm, 45 mm, 65 mm, 85 mm, and 105 mm. A ventilation structure 10A was produced.

For the six types of muffling ventilation structures 10A produced in this way, using the basic two-dimensional calculation model shown in FIG. 12, finite elements using the acoustic module of the finite element method calculation software COMSOL Multiphysics ver.5.3 (COMSOL). Simulation calculation was performed by the method, and the average value asp of the square of the absolute value of sound pressure | p | ^{2 was obtained.}
FIG. 15 shows the sound pressure distribution (sound pressure level (dB): log10 (| p |)) of the sound having a frequency of 300 Hz in the predetermined space thus obtained and in the sound deadening ventilation structure 10 of Example 1-1. Both the horizontal axis and the vertical axis represent the coordinates (distance) of the coordinate system with 0 as the origin in FIG.
From FIG. 15, in the sound of 300 Hz, the sound absorbing material 18 on the ceiling surface and the sound absorbing material 18 on the side surface correspond to the corner end portion 12a of the upper left corner of the hood body 12 in the sound deadening ventilation structure 10A shown in FIG. It can be seen that the corner end of the upper left corner where the sound pressure is in contact is the maximum point p _{max of the sound pressure.}

Further, the average value asp of the square of the absolute value of the sound pressure with respect to the frequency of the sound deadening ventilation structure 10A of the seven types of Example 2 including the sound deadening ventilation structure 10 of Example 1-1 shown in this manner is shown in FIG. 16 is shown.
Further, from the average value asp of the square of the absolute value of the sound pressure with respect to the frequency shown in FIG. 16, the average of the square of the absolute value of the sound pressure of the sound deadening ventilation structure 10A of the seven types of Example 2 with respect to the distance x at the frequency of 300 Hz. The value asp value is shown in FIG.

From FIG. 16, it can be seen that the muffling ventilation structure 10 (x = 0 mm) of Example 1-1 shown in FIG. 10 has a sound pressure peak (maximum point) at 300 Hz. It can be seen that the sound deadening ventilation structure 10A (x = 5 mm to 105 mm) of the remaining six types of Example 2 also has a sound pressure peak (maximum point) in the vicinity of 300 Hz.
_{Further, focusing on 300 Hz from FIGS. 16 and 17, the maximum point p max} of the sound pressure at which the sound of 300 Hz passes through the muffling ventilation structure 10A is the corner end of the upper left corner of the sound absorbing material 18 shown in FIG. Since it is a position, it can be said that the distance between the surface (contact surface 32) of the sound absorbing material 18 and the maximum sound pressure point p _{max is x.} Here, it can be seen that the smaller the distance x, that is, the closer the surface (contact surface 32) of the sound absorbing material 18 and the sound pressure _maximum point p max of the sound deadening ventilation structure 10A are, the higher the sound deadening effect is.
Here, since the wavelength λ of the resonance mode is 1133 mm (n = 1), nλ / 16 is 70 mm. Therefore, in FIG. 17, x = 0 mm, 5 mm, 25 mm, 45 mm, and 65 mm circled. It can be seen that the five points of the above have a lower sound pressure and a higher muffling effect than the two points of x = 85 mm and 105 mm on the outside of the circle. That is, it was found that a higher sound deadening effect can be obtained by the presence of the surface (contact surface 32) of the sound absorbing material 18 within nλ / 16 from the point where the sound pressure becomes maximum.
Therefore, it can be said that the effectiveness of the present invention has been demonstrated.
From the above Examples 1-1, 1-2, and 2, the effect of the present invention is clear.

The muffling ventilation structure of the present invention has been described in detail with reference to various embodiments and examples, but the present invention is not limited to these embodiments and examples and does not deviate from the gist of the present invention. Of course, various improvements or changes may be made in the above.

10, 10A, 11, 40, 40A, 40B. 40C, 40D, 50, 52 Silent ventilation structure 12 Hood body 12a Square end 12b, 14a Ceiling surface 12c Side surface 13 Opening 14 Sleeve 16 Hood 18 Sound absorbing material 20 Covering material 22 First opening 24 Second opening 26 Outdoor (outside) space)
28 Indoor (internal space)
30 walls (peripheral wall, concrete wall)
32, 32a, 32b, 32c, 32d Contact surfaces 42, 42a, 42b, 42c, 42d, 46, 46a, 46b Tubular body 44, 44a, 44b, 48 Opening 60 Acoustic characteristic measurement system 62 Tube 64 Microphone 66 Speaker 68 Box 70 Material of sound-impermeable material asp Average value of the square of the absolute value of sound pressure n Order of resonance mode (positive integer)
p _max Sound pressure maximum point S sound

Claims (8)

It has a hood-type sound deadening ventilation structure.
A hood and a hood having a sleeve connected to the hood body and communicating with the space inside the hood body.
With at least one first opening provided in the hood body,
With at least one second opening provided in the sleeve,
The sound absorbing material provided inside the hood body and
It has a covering material that selectively covers a part of the surface of the sound absorbing material, and has.
The traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different.
The covering material selectively exposes the other part of the surface of the sound absorbing material, and the selective exposed portion is configured as at least one contact surface in contact with the space in the ventilation hood.
The sound absorbing material is attached to the inner surface of the hood body facing the surface to which the sleeve is connected and the inner surface of the hood body facing the first opening.
The coating material is a material made of a material impervious to sound,
The material that does not allow sound to pass through is a plate-shaped material with the same thickness as the covering material used, which is installed so as to block all the waveguides of the acoustic tube, and is 250 Hz when evaluated by the 4-microphone method. It is a material with a transmission loss of 5 dB or more over ~ 4000 Hz.
The at least one contact surface corresponds to the frequency of the nth-order resonance mode by setting n = 1, 2, ... (Positive integer) from the lower side of the resonance mode order of the frequency in the audible range at 100 Hz or higher. A muffling ventilation structure existing within the range of λn / 16 from the point where the sound pressure of the sound wave corresponding to any of the wavelengths of the resonance mode is maximized when the wavelength is λn. The at least one contact surface corresponds to the frequency of the nth-order resonance mode by setting n = 1, 2, ... (Positive integer) from the lower side of the resonance mode order of the frequency in the audible range at 100 Hz or higher. The muffling ventilation structure according to claim 1, wherein when the wavelength is λn, the sound deadening ventilation structure exists within the range of λn / 16 from the corner end portion in the hood body. The muffling ventilation structure according to claim 1 or 2, wherein the traveling direction of the sound passing through the first opening and the traveling direction of the sound passing through the second opening are different by 90 °. The sound deadening ventilation structure according to any one of claims 1 to 3, wherein the at least one contact surface occupies an area of 1.0% to 50% with respect to the total area of the surface of the sound absorbing material. Any of claims 1 to 4, wherein the sound absorbing material is attached to an area of 50% or more with respect to the total area of the inner surface of the hood body excluding the first opening and the connecting portion of the sleeve. The muffling ventilation structure according to item 1. The sound deadening ventilation structure according to any one of claims 1 to 5, wherein the volume of the sound absorbing material is 1.0% to 50% of the internal volume of the hood body. The muffling ventilation structure is an external hood type muffling ventilation structure installed on the outdoor side of a ventilation port penetrating a wall separating indoors and outdoors.
The hood body is placed outdoors and
The muffling ventilation structure according to any one of claims 1 to 6, wherein the sleeve is arranged so as to penetrate the wall. Further, it has at least one tubular body having an opening opening in the space in the hood on at least one side surface of the hood.
The inside of the tubular body is filled with the sound absorbing material.
The opening of the tubular body selectively exposes a part of the surface of the sound absorbing material, and the selective exposed portion is configured as at least one contact surface in contact with the space in the hood. The muffling ventilation structure according to any one of 1 to 6.

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