JP2012123293A - Stationary inductance electrical appliance and low frequency sound absorbing wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, taking note of characteristic frequencies of noise emitted from stationary inductance electrical appliances, a stationary inductance electrical appliance equipped with a low frequency sound absorbing member that can effectively reduce noise in the low frequency range.SOLUTION: In a stationary inductance electrical appliance whose body is surrounded by a noise barrier configured by combining sound intercepting boards, each sound intercepting board 24 is lined with a low frequency sound absorbing member 31 configured by stacking one over another a perforated board 21a having openings 25 whose bores and lengths are so formed as to achieve resonance with the frequency of the sound wave of the noise to be reduced, a sound absorbing material 22 formed of an interconnected cell hard foam substance made of either a porous material or an interconnected cell substance and a textile sound absorbing material 23.

Description

  Embodiments of the present invention relate to a static induction electric device represented by a transformer and a reactor, and a low frequency sound absorbing wall that covers the static induction electric appliance and reduces low frequency noise generated from the static induction electric appliance.

  In static induction appliances such as transformers and reactors, it is known that noise based on the power supply frequency is generated from the main body of the static induction appliance, and in particular, noise in a low frequency region of 100 to 200 Hz is often a problem. As a means for reducing the noise in the low frequency region, a soundproof structure such as a soundproof tank generally made of a steel plate is often installed so as to surround the stationary induction main body.

  FIG. 11 is a vertical sectional view showing a schematic configuration of a static induction electric device having a general noise reduction structure, and a general noise reduction means of the static induction electric device will be described with reference to FIG.

  The soundproof structure 2 is a soundproof structure provided so as to surround the periphery of the stationary induction electric body 1 and is combined so as to cover the stationary induction electric body 1 with a sound insulating wall 4 made of a metal panel such as a steel plate. It is configured.

  The porous sound absorbing material 3 is installed on the inner surface of the sound insulating wall 4 in order to prevent an increase in noise level due to build-up inside the soundproof structure 2.

  With this configuration, noise generated from the static induction electric body 1 is reduced by the transmission loss of the sound insulating wall 4 constituting the soundproof structure 2 and the sound absorption effect by the porous sound absorbing material 3. Noise can be reduced.

  As described above, various proposals for improving the performance of the porous sound absorbing material 3 used for preventing an increase in the noise level due to build-up and the method for constructing the same are made in the soundproof structure 2. ing.

  For example, a film and a porous layer such as glass wool are combined in order to improve the sound absorption characteristics of the sound absorbing material with respect to noise in a low frequency range of 100 Hz to 200 Hz, which is a characteristic frequency range of typical noise generated from a static induction appliance. Low frequency sound absorbing members are often used.

The above configuration will be described with reference to FIG. FIG. 12 is a longitudinal sectional view showing the configuration of the low frequency sound absorbing member. In the figure, the low frequency sound absorbing member 5 has a thickness of about 50 μm and an area density of 0.68 to 0.78 kg / m ² , or 1. A film 6 made of a silicon-based resin of 1.75 to 1.85 kg / m ² and a porous body layer 7 made of glass wool (density 32 kg / m ³ ) laminated on the back side of the film 6 are low An effect is obtained with respect to noise in the frequency domain.

  The low-frequency sound-absorbing member 5 configured in this way is disposed on the inner surface of a metal sound-insulating wall 4 such as a steel plate that houses the stationary induction electric body 1 or on the floor surface on which the stationary induction electric body 1 is installed.

  In the soundproof structure of the static induction appliance having such a configuration, the peak frequency of the sound absorption coefficient of the low frequency sound absorbing member 5 can be shifted to the low frequency region side by setting the surface density of the film 6 as described above. At the same time, the sound absorption coefficient in the low frequency region near 200 Hz can be improved.

  Moreover, in order to improve the sound absorption effect with respect to noise in a low frequency range of 400 Hz or less, particularly 120 Hz or less, a low frequency sound absorbing member in which a porous sound absorbing plate and a fibrous sound absorbing material are combined may be used.

  The configuration of the low-frequency sound absorbing member used in this case will be described with reference to FIG.

  A porous metal sound absorbing plate 8 having a thickness of 3 mm to 12 mm, a fibrous sound absorbing material 9 having a thickness of 30 mm to 100 mm, an air layer 10 having a thickness of 30 mm to 100 mm, and a thickness of 30 mm to 100 mm from the generated sound source side (upper side in the figure). The fibrous sound absorbing material 9 is disposed in order. Further, a sound insulating plate (not shown) may be further disposed on the back side of the fibrous sound absorbing material 9.

  In the sound absorbing structure having the above-described configuration, by combining the metal porous sound absorbing plate 8 and the fibrous sound absorbing material 9, a higher sound absorption rate can be obtained than in the case where each is used alone, and the static induction appliance It becomes possible to obtain a high sound absorption coefficient in a low frequency region of 120 Hz or less, which is a characteristic frequency of noise generated from the main body 1.

  In addition, as an example of a static induction appliance using a soundproof wall that applies the principle of a silencer, for example, a rod-shaped sound absorbing plate made of open-celled hard foam material has a convex curved surface along its longitudinal direction at its axial center. The sound absorbing plate is formed at both ends of the sound absorbing plate in the width direction according to the both ends of the sound insulating plate, the sound absorbing plate side of the sound insulating tube is directed to the noise generating source side, and the sound insulating tube There is a static induction electric device using soundproof walls arranged in close proximity to each other or at a predetermined interval.

  The configuration of the sound barrier used here will be described with reference to FIGS. 14 and 15.

  In the figure, 11 is a soundproof wall, 12 is a soundproof tube, 13a is a sound absorbing plate made of an aluminum foam material constituting the soundproof tube, and 13b is a sound insulating plate made of an aluminum flat plate.

  The soundproof cylinder 12 constituting the soundproof wall 11 is formed in a shape having a convex curved surface portion along the longitudinal direction at the center in the width direction, and both ends of the sound absorbing plate 13a made of open cell hard foam material and the sound insulating plate 13b. Are combined to form a hollow portion 14 with a sound absorbing plate 13a and a sound insulating plate 13b.

  The sound wave having a frequency corresponding to the thickness of the air layer of the cavity portion 14 of the soundproofing cylinder 12 can be absorbed with a high sound absorption rate by the incident position of the sound wave on the sound absorbing plate 13a.

  Such a soundproof cylinder has high sound absorption performance for sound waves having a wide range of frequencies. Further, as described above, since the sound absorbing plate 13a is formed in a shape having a convex curved surface portion, it is possible to absorb sound waves incident at an arbitrary angle with respect to the sound absorbing plate with a high sound absorption rate. .

JP 2007-324388 A Japanese Patent Laid-Open No. 10-183813 JP-A-3-228905

  All of the above aims to enhance the sound absorption effect in the low frequency region, which is a problem due to the noise of static induction appliances.

  Here, when trying to reduce the noise in the low frequency region by combining only the sound absorbing material, for example, when using glass wool, it is necessary to take a large air layer due to the problem of the sound absorbing characteristics, and the whole In many cases, the thickness becomes large, which is a problem when applied to realistic equipment.

  Here, a resonance type silencer will be described as one of typical silencers that exert an effect on a specific frequency.

  The resonance frequency f of the Helmholtz type silencer, which is one of the resonance type silencers, is obtained by the equation (1) (provided that the shape of the opening is a round hole).

f = {c / (2π)} √ [S / {V (L + 0.8d)}] (1)
Here, c is the sound velocity of the medium, S is the opening area of the silencer, V is the volume of the silencer, L is the length of the opening (neck length), and d is the diameter of the opening.

  For example, when a transformer is taken as an example of a typical static induction device, the main frequency of the generated sound is twice the power supply frequency and its harmonic component, so the characteristics of the generated noise The frequency is a known value. Therefore, it is possible to reduce noise by the silencer by configuring the silencer so that the resonance frequency of the silencer matches the characteristic frequency of the generated noise in advance.

  In the embodiment of the present invention, as described above, attention is paid to the characteristic frequency in the noise generated by a static induction electric device represented by a transformer, a reactor, etc., and particularly noise in a low frequency region can be effectively reduced. For the purpose.

  In order to solve the above problems, in a static induction electric machine according to an embodiment of the present invention, a static induction electric body that generates noise having a specific characteristic frequency, an opening diameter and a resonance frequency so as to resonate with the noise of the characteristic frequency A perforated member that includes an opening having an opening length and covers the stationary induction electric body, an open-cell foam material that covers the perforated member and is configured of either a porous material or an open-cell body; It has a fibrous sound absorbing material that covers the perforated member, and a sound insulating plate that covers the open cell foam material and the fibrous sound absorbing material.

  With such a configuration, the noise reduction performance in the low frequency region is improved by a combination of sound absorbing materials having different sound absorbing characteristics, and a perforated member, an open cell rigid foam material, and a fibrous sound absorbing material are used. Due to the resonance effect of the low frequency sound absorbing member, noise in the low frequency region can be more effectively reduced.

  In addition, in the static induction device according to the embodiment of the present invention, the low-frequency sound absorbing member includes an opening having a plurality of different opening diameters so as to obtain a resonance effect with respect to different frequencies. A low frequency sound absorbing member is formed using a perforated member.

  With such a configuration, the noise reduction effect can be improved by setting the aperture diameter of the perforated member so as to resonate with the characteristic frequency even for noise having different frequency components.

  Moreover, in the static induction device according to the embodiment of the present invention, as the above-described low-frequency sound absorbing member, as an open-celled hard foam material composed of either a porous material or an open-cell body, a metal such as aluminum or iron It is characterized by using materials.

  By adopting such a configuration, it is possible to realize a low-frequency sound absorbing structure with excellent environmental resistance even when used in oil, for example.

  Moreover, in the static induction appliance which concerns on embodiment of this invention, you may arrange | position the cylindrical member by which the internal diameter and length were adjusted as a low frequency sound absorption member mentioned above so that a board | substrate might be penetrated.

  In addition, the cylindrical member can reduce the plate thickness of the perforated member by arranging ones having a plurality of different dimensions, and exhibit a resonance effect for a plurality of frequency components. Therefore, it is possible to realize a low-frequency sound absorption structure that is lighter and has a large sound absorption effect.

  Further, the static induction device according to the embodiment of the present invention is characterized in that, in the above-described low frequency sound absorbing member, the low frequency sound absorbing member is housed in a box-shaped housing to form a panel shape. .

  By adopting such a configuration, it is easy to install in a specific portion that is a target of noise reduction, and it is possible to improve workability such as soundproofing work.

  Further, in the static induction device according to the embodiment of the present invention, in the low-frequency sound absorbing member, a plurality of resonances with respect to the opening of the panel-shaped sound absorbing member that is housed in a box-shaped housing and configured in a panel shape. It is characterized in that a partition is provided in the box-shaped casing so as to form a box.

  With such a configuration, the degree of freedom of the resonance frequency determined by the opening diameter, opening length, and volume behind the housing increases, so that a more ideal design is possible and low frequency sound absorption with a greater sound absorption effect is possible. A structure can be realized.

  Further, in the low frequency sound absorbing wall according to the embodiment of the present invention, the low frequency sound absorbing wall covers the stationary induction electric body that generates noise having a specific characteristic frequency, and so as to resonate with the noise of the characteristic frequency. An opening member having an opening having an opening diameter and an opening length and covering the stationary induction body, and an open cell foam covering the opening member and made of either a porous material or an open cell body And a sound absorbing plate that covers the open-cell foamed material and the fibrous sound absorbing material.

  With such a configuration, the noise reduction performance in the low frequency region is improved by a combination of sound absorbing materials having different sound absorbing characteristics, and a perforated member, an open cell rigid foam material, and a fibrous sound absorbing material are used. Due to the resonance effect of the low frequency sound absorbing member, noise in the low frequency region can be more effectively reduced.

The longitudinal cross-sectional view which shows the low frequency sound absorption structure of the transformer which concerns on the 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the low frequency sound absorption structure of the transformer which concerns on the modification of the 1st Embodiment of this invention. The front view which shows the low frequency sound-absorbing structure (perforated member) of the transformer which concerns on the 1st Embodiment of this invention. The front view which shows the modification of the perforated member in the 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the low frequency sound absorption structure of the transformer which concerns on the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the modification of the low frequency sound absorption structure of the transformer which concerns on the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the modification of the low frequency sound absorption structure of the transformer which concerns on the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the modification of the low frequency sound absorption structure of the transformer which concerns on the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the low frequency sound absorption structure of the transformer which concerns on the 3rd Embodiment of this invention. The longitudinal cross-sectional view which shows the modification of the low frequency sound absorption structure of the transformer which concerns on the 3rd Embodiment of this invention. The elevation sectional view which shows the soundproof structure of the conventional transformer. The longitudinal cross-sectional view which shows the conventional low frequency sound absorption structure. The longitudinal cross-sectional view which shows the conventional low frequency sound absorption structure. The side view which shows the conventional low frequency sound absorption structure. The cross-sectional view which shows the conventional low frequency sound absorption structure.

  Hereinafter, an embodiment of a static induction electric machine according to the present invention will be described with reference to the drawings, taking a transformer as an example.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 and 3. FIG. 1 is a longitudinal sectional view showing a configuration of a low-frequency sound absorbing member that forms a low-frequency sound absorbing structure in the transformer of the present embodiment, and FIG. 3 is a front view of the perforated member in FIG. 1 viewed from the sound source side. It is.

  Hereinafter, the configuration of the low-frequency sound absorbing member in the present embodiment will be described with reference to the drawings.

  Porous material such as perforated plate 21a, glass wool, rock wool, aluminum fiber material, and the like, which are perforated members in which openings 25 having a predetermined opening diameter d1 are provided at predetermined intervals p in order from the sound source side (upper side in the figure). A low-frequency sound-absorbing member 31 formed by superposing a sound-absorbing material 22 made of an open-celled hard foam material such as a material, urethane, polyethylene, or aluminum foam, and a fibrous sound-absorbing material 23 having different sound-absorbing characteristics from the sound-absorbing material 22 Is attached to the inner surface of the sound insulation plate 24.

  The sound wave propagated from the sound source side first has an opening diameter of the opening 25 of the perforated member 21 due to the resonance effect of the Helmholtz type silencer formed by the perforated plate 21a and the sound absorbing materials 22 and 23 behind the perforated plate 21a. The noise of the resonance frequency component determined by d1, the plate thickness, the back layer, and the operation range is reduced.

  Furthermore, due to the combined effect of the sound absorbing effect of the sound absorbing material itself having a double structure with the sound absorbing material 22 made of a porous material or open-cell hard foam material and the fibrous sound absorbing material 23 having a different sound absorbing characteristic from the sound absorbing material 22, Compared with the sound absorbing effect obtained with a single sound absorbing material, the sound absorbing characteristics can be improved more effectively in a wider band.

  Here, as the sound absorbing material 22 made of a porous material or an open-cell hard foam material, when a metal material such as aluminum is used, the influence of performance degradation due to moisture absorption or the like is relatively small and stable against environmental changes. The effect can be obtained and the recycling is relatively easy.

  Next, a modification of the first embodiment will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of a low-frequency sound absorbing member used in this modification.

  In FIG. 2, an air layer 26 is provided between the low frequency sound absorbing member 31 and the sound insulating plate 24. In this modification, by adopting such a configuration, it is possible to realize a sound absorbing structure that is further excellent in sound absorbing characteristics in a low frequency region.

  In addition, about the number and arrangement | positioning of the opening part 25 of the perforated board 21a, it is not limited to what was shown in FIG. Further, regarding the thickness of the porous material or the open-cell hard foam material and the fibrous sound absorbing material constituting the sound absorbing structure, the thickness of the perforated plate 21a, the opening diameter d1 of the opening 25, the working range of the opening 25, and What is necessary is just to determine suitably within the range of the dimension determined by the frequency used as the object of reduction.

  Next, still another modification of the first embodiment will be described with reference to FIG. FIG. 4 shows a modification of the perforated plate 21a shown in FIG. In the low frequency sound-absorbing member 31 of this modification, the perforated plate 21a includes openings 25 having a plurality of different opening diameters d1 and d2, which are adjusted to resonate with a plurality of different frequencies. (FIG. 4 shows a case of a perforated member having two types of opening diameters).

  By adopting such a configuration, the Helmholtz-type resonance structure that exhibits an effect only in the vicinity of a single resonance frequency can be configured to exhibit an effect for a plurality of different frequencies. Sound absorption characteristics can be improved.

  The arrangement and number of the openings 25 of the perforated plate 21a are not limited to those illustrated. Further, although only two types of different opening diameters are shown in FIG. 4, a combination of openings having a plurality of opening diameters of three kinds or more may be used.

[Second Embodiment]
A second embodiment of a static induction electric machine according to the present invention will be described with reference to FIG. 5, taking a transformer as an example, as in the first embodiment. FIG. 5 is a longitudinal sectional view showing a configuration of a low-frequency sound absorbing member applied to the transformer according to the present embodiment, and the configuration of the low-frequency sound absorbing member of the present embodiment will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the part which is the same as or similar to drawing referred in embodiment mentioned above, and description is abbreviate | omitted.

  In the figure, a perforated member 21, a porous or open-cell hard foam sound absorbing material 22, and a fibrous sound absorbing material 23 are attached to a sound insulating plate 24 in order from the sound source side (upper side in the figure). The perforated member 21 is formed by penetrating a pipe-shaped opening cylinder 32 open at both ends in the substrate 21b. The opening diameter and length of the opening cylinder 32 are appropriately determined depending on the resonance frequency of the sound wave that is the target of noise reduction.

  The sound wave propagated from the sound source side is firstly opened by the resonance effect of the Helmholtz-type silencer formed by the portion constituted by the perforated member 21 and the sound absorbing materials 22 and 23 behind the perforated member 21. The noise at the resonance frequency determined by the 32 aperture diameter, length, back layer and working range is reduced.

  Furthermore, the sound absorption effect of a single sound absorbing material is compared with the combined effect of the sound absorbing effect of the sound absorbing material itself composed of a porous or open-celled rigid foam and the sound absorbing material 23 having a double structure. Thus, the sound absorption characteristics can be improved more effectively in a wider band.

  Further, since the opening member 21 has the opening cylinder 32 formed in the substrate 21b to form the opening, the thickness of the substrate 21b of the opening member 21 is reduced with respect to the opening length necessary for resonance. Therefore, it is possible to realize a lighter sound absorbing structure while ensuring sound absorbing performance.

  As a modification of this configuration, an air layer 26 may be provided between the sound absorbing material 23 and the sound insulating plate 24 as shown in FIG.

  With the configuration as described above, it is possible to achieve a light-absorbing structure that is excellent in sound-absorbing characteristics in a lower frequency region and that is lightweight.

  Note that the number and arrangement of the opening cylinders 32 do not necessarily match those shown in the drawing, and may be appropriately determined according to the target frequency and the size of the sound absorbing member.

  Next, a modification of the second embodiment will be described with reference to FIG. FIG. 7 is a longitudinal sectional view showing the configuration of the low-frequency sound absorbing member of this modification. In the figure, the opening cylinders 32a and 32b having openings with different diameters adjusted to resonate at different frequencies are used as substrates. A perforated member 21 is formed so as to penetrate through 21b and is attached to the sound insulating plate 24 so as to overlap with the sound absorbing materials 22 and 23 as in the example shown in FIG.

  By adopting such a configuration, the Helmholtz-type resonance configuration that exhibits an effect only in the vicinity of a single resonance frequency can be configured to be effective for a plurality of different frequencies. It is possible to improve sound absorption characteristics with respect to sound waves.

  Note that the arrangement and number of the opening cylinders are not limited to those illustrated.

  Further, as for the types of the opening cylinders having different opening diameters, only two types of large and small are shown in FIG. 7, but a combination of three or more types may be used.

  Although not shown, an air layer as shown in FIG. 6 may be provided between the sound absorbing material 23 and the sound insulating plate 24.

  Next, still another modification of the second embodiment will be described with reference to FIG. FIG. 8 is a longitudinal cross-sectional view showing the configuration of the low-frequency sound absorbing member of the present modification, in which a plurality of opening cylinders 33a and 33b adjusted to resonate at different frequencies and having different opening lengths are used as substrates. A perforated member 21 is formed so as to penetrate through 21 b, and a low frequency sound absorbing member is formed by overlapping with the sound absorbing materials 22 and 23, and is attached to the sound insulating plate 24.

  By adopting such a configuration, the Helmholtz-type resonance configuration that exhibits an effect only in the vicinity of a single resonance frequency can be configured to exhibit an effect at a plurality of different frequencies. On the other hand, the sound absorption characteristics can be improved.

  Note that the arrangement and number of the opening cylinders are not limited to those illustrated. Also, regarding the types of opening cylinders having different opening lengths, only two types of long and short are shown in FIG. 8, but a combination of three or more types may be used.

  Further, although only one type of opening diameter of the opening cylinder is shown in FIG. 8, a combination of opening cylinders having a plurality of different opening diameters may be used.

  Although not shown, an air layer similar to the air layer shown in FIG. 6 may be provided between the sound absorbing material 23 and the sound insulating plate 24.

[Third Embodiment]
A third embodiment of the static induction electric machine of the present invention will be described with reference to FIG. 9, taking a transformer as an example, as in the above-described embodiment. FIG. 9 is a longitudinal sectional view showing the configuration of the low-frequency sound absorbing member in the transformer according to this embodiment, and the configuration of the low-frequency sound absorbing member of this embodiment will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the part which is the same as or similar to drawing referred in embodiment mentioned above, and description is abbreviate | omitted.

  In FIG. 9, a perforated plate 21a, a sound absorbing material 22 made of porous or open-celled hard foam, and a fibrous sound absorbing material 23 are stacked in order from the sound source side (upper side of the figure). A box-shaped housing 34 is provided so as to cover the fibrous sound-absorbing material 23, and a panel-shaped low-frequency sound absorbing member is formed. Moreover, the opening part 25 is formed in the perforated plate 21a. The opening diameter of the opening 25 and the length of the opening 25 are appropriately determined depending on the resonance frequency of the target sound wave. This panel-like low-frequency sound absorbing member is a low-frequency sound absorbing member for a static induction machine by arranging a plurality of members having the same configuration in the surface direction.

  By making the low-frequency sound absorbing member into the shape of a plurality of panels, it becomes easy to handle, and it is possible to provide a sound absorbing structure with excellent portability and storage.

  The opening diameter, opening length, and number of the perforated plate 21a are not necessarily limited to those illustrated. Moreover, in the said embodiment, the perforated member which formed the opening part which has an opening diameter so that Formula (1) may be satisfied in the board | substrate which has the board thickness adjusted so that it may resonate with the frequency of the sound used as sound absorption object previously. However, the thickness of the substrate is reduced, and the cylindrical member whose inner diameter and length are adjusted so as to satisfy the expression (1) is disposed on the perforated member formed by penetrating the substrate. You may do it.

  Although not shown, an air layer may be provided between the sound absorbing material 23 and the housing 34.

  Next, a modification of the third embodiment will be described with reference to FIG. FIG. 10 is a longitudinal sectional view showing the configuration of the low-frequency sound absorbing member of this modification. In the figure, a partition plate 35 is provided inside the housing 34 in accordance with the arrangement of the opening 25.

  In such a configuration, by appropriately changing the position of the partition plate 35, the volume corresponding to the back layer of the perforated plate 21a can be easily changed. The volume of the back layer is formed corresponding to the resonance frequency of the Helmholtz type silencer, as is apparent from the above-described equation (1).

  Therefore, the constituent factor for determining the resonance frequency increases by one, and it becomes easy to match the frequency of the sound wave to be absorbed, and a more effective sound absorbing structure can be realized.

  The opening diameter, the opening length, and the number of the openings 25 of the perforated plate 21a are not necessarily limited to those illustrated. Further, the opening 25 may be an opening cylinder instead of a simple opening.

  Although not shown, an air layer may be provided between the sound absorbing material 23 and the housing 34.

  In this example, the perforated plate provided with the opening shown in the first embodiment was used as the perforated member. However, the opening cylinder was passed through the substrate as shown in the second embodiment. Alternatively, a perforated member in which an opening is formed may be used.

[Other Embodiments]
The embodiments described above are merely examples, and the present invention is not limited to these. For example, the features of different types of embodiments can be combined in various ways.

DESCRIPTION OF SYMBOLS 1 ... Static induction electric machine body 2 ... Soundproof structure 3 ... Porous sound absorption material 4 ... Sound insulation wall 5 ... Low frequency sound absorption member 6 ... Film 7 ... Porous body layer 8 ... Metal porous sound absorption board (open-cell foaming material)
DESCRIPTION OF SYMBOLS 9 ... Fibrous sound absorption material 10 ... Air layer 11 ... Sound insulation wall 12 ... Sound insulation cylinder 13a ... Sound absorption board 13b ... Sound insulation board 14 ... Hollow part 21 ... Hole member 21a ... Hole plate 21b ... Substrate 22 ... Porous sound absorption material 23 ... fibrous sound absorbing material 24 ... sound insulating plate 25 ... opening 26 ... air layer 30 ... resonance action range 31 ... low frequency sound absorbing members 32, 32a, 32b, 33a, 33b ... open tube 34 ... housing 35 ... partition plate

Claims (9)

A static induction body that generates noise having a specific characteristic frequency; and
A perforated member that includes an opening having an opening diameter and an opening length so as to resonate with the noise of the characteristic frequency and covers the stationary induction body;
An open-cell foam covering the perforated member and composed of either a porous material or an open-cell body;
A fibrous sound absorbing material covering the perforated member;
A sound insulating plate covering the open cell foam material and the fibrous sound absorbing material;
A static induction machine characterized by comprising:   The stationary induction device according to claim 1, wherein the perforated member is a perforated plate in which openings having different opening diameters are formed.   The perforated member is characterized in that an opening is formed through an opening cylinder having an opening diameter and an opening length adjusted so as to resonate with a characteristic frequency of noise to be reduced. The static induction machine according to claim 1.   The static induction machine according to claim 3, wherein the cylindrical member has a plurality of different diameters.   The static induction machine according to claim 3 or 4, wherein the cylindrical member is formed in a plurality of different dimensions.   The static induction machine according to any one of claims 1 to 5, wherein the low-frequency sound absorbing member is configured by combining a plurality of panel-like sound absorbing members housed in a box-shaped housing.   The stationary induction machine according to claim 6, wherein the low-frequency sound absorbing member configured in a panel shape is provided with a plurality of partitions along the length direction of the opening.   The static induction device according to any one of claims 1 to 7, wherein a metal material is used as a material of the porous material or the open cell body. A low-frequency sound-absorbing wall covering a stationary induction body that generates noise having a specific characteristic frequency,
A perforated member that includes an opening having an opening diameter and an opening length so as to resonate with the noise of the characteristic frequency and covers the stationary induction body;
An open-cell foam covering the perforated member and composed of either a porous material or an open-cell body;
A fibrous sound absorbing material covering the perforated member;
A sound insulating plate covering the open cell foam material and the fibrous sound absorbing material;
A low-frequency sound-absorbing wall characterized by comprising:

Images