JP2000099034A - Resonator type sound absorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorbing device coping with noise whose frequency vary in time and position. SOLUTION: In the device, a resonance space 16 is defined as the space surrounded by a wall body 15 made of a front surface wall 12, a firm wall 13, which is arranged opposing to the wall 12 with a gap, and a connecting wall 14, which connects the peripheral sections of the walls 12 and 13. An entrance 17 is provided on the wall 12 to connect the space 16 to the external. At least one of the walls 12 or 13 is made freely movable between the wall 14 in the direction closing to the other side or separating from the other side while maintaining airtighness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator type sound absorbing device having an adaptive sound absorbing capability capable of changing a resonance frequency according to a temporal or positional change of the frequency of a sound from a sound source.

[0002]

2. Description of the Related Art Conventionally, a resonator-type sound absorbing structure known as a so-called Helmholtz resonator is frequently used for air-conditioning ducts, walls, walls and the like. In recent years, active noise control techniques for reducing noise by arranging a secondary sound source near a noise source have been actively studied.

[0003]

The above-described resonator type sound absorbing structure has an advantage that sound can be absorbed by a simple mechanism, but has a problem that it cannot cope with a sound having a resonance frequency other than the resonance frequency determined at the time of design. ing. On the other hand, the above-described active noise control method has a certain effect on noise reduction in a space having a simple shape, but for example, noise in a space having a complicated shape such as around a pantograph of a railway or inside an engine of a car or the like. Sufficient effects have not yet been achieved for the reduction.

[0004]

According to the present invention, there is provided a resonator type sound absorbing device which can cope with noise whose frequency changes with time or position by improving the above described resonator type sound absorbing device. The purpose is to:

[0005] Therefore, a resonator-type sound absorbing device according to claim 1 of the present invention has a front wall, a rigid wall opposed to the front wall at a distance from the front wall, and peripheral portions of the front wall and the rigid wall. A space surrounded by a wall body composed of a connecting wall connecting each other is defined as a resonance space, and an entrance for communicating the resonance space with the outside is provided on the front wall, and at least one of the front wall or the rigid wall is provided. It is characterized by being movable in a direction approaching or moving away from the other side while maintaining airtightness with the connection wall.

[0006] In the above configuration, by moving at least one of the front wall and the rigid wall so as to approach or separate from the opponent, the distance between the front wall and the rigid wall is reduced or increased, and the volume of the resonance space is increased. When changed, the resonance frequency of the resonator type sound absorbing device can be changed accordingly.

According to a second aspect of the present invention, there is provided a resonator type sound absorbing device.
In the above structure, the resonator type sound absorbing device is provided by providing a partition in the wall body that extends substantially perpendicularly to the front wall and the rigid wall from the front wall to the rigid wall over the entire thickness direction of the resonator type sound absorbing device. The device is divided into a plurality of sound absorbing units, and the entrance of the front wall is provided corresponding to each sound absorbing unit, and at least one of the front wall or the rigid wall is configured as a divided body divided for each sound absorbing unit,
The front wall or the rigid wall can be moved independently of each other. Here, the divided body of the front wall or the rigid wall is moved for each sound absorbing unit,
The volume of the resonance space for each sound absorbing unit can be changed.

According to a third aspect of the present invention, there is provided a resonator type sound absorbing device.
In the configuration of the above, a detector for detecting the sound absorption frequency that is the frequency of the sound from the sound source is provided for each sound absorption unit, so that the resonance frequency of each sound absorption unit matches the sound absorption frequency based on the detected sound absorption frequency. Control means for moving the divided body of the front wall or the rigid wall is provided. Here, the resonance frequency of each sound absorbing unit is autonomously adjusted based on the sound absorbing frequency detected for each sound absorbing unit.

According to a fourth aspect of the present invention, there is provided a resonator type sound absorbing device, wherein a space surrounded by a wall including a front wall is a resonance space, and the front wall is provided with an inlet for communicating the resonance space with the outside.
The resonance space is divided into a plurality of parts by providing a partition wall substantially parallel to the front wall in the wall body, and a communication port for communicating the spaces on both sides is provided on the partition wall, and an opening / closing means for opening and closing the communication port is provided. It is characterized by having.

In the above structure, when the communication port is open, the space on both sides of the partition wall becomes a resonance space, whereas when the communication port is closed by the opening / closing means, the front wall is bounded by the partition wall. Only the space on the side becomes a substantial resonance space. Thus, by opening and closing the communication port by the opening and closing means, it is possible to change the substantial volume of the resonance space and change the resonance frequency.

According to a fifth aspect of the present invention, there is provided a resonator type sound absorbing device.
In the above structure, a partition is provided in the wall body, which extends substantially perpendicularly to the front wall and the partition wall over the entire area in the thickness direction of the sound absorbing unit, and the resonator type sound absorbing device is divided into a plurality of sound absorbing units. An entrance of the front wall, a communication port of the partition, and the opening / closing means for opening and closing the communication port are provided corresponding to the unit. Here, the volume of the substantial resonance space of each sound absorbing unit can be changed by opening and closing the opening and closing means for each sound absorbing unit.

According to a sixth aspect of the present invention, there is provided a resonator type sound absorbing apparatus.
In the configuration of the above, a detector for detecting the sound absorption frequency that is the frequency of the sound from the sound source is provided for each sound absorption unit, so that the resonance frequency of each sound absorption unit matches the sound absorption frequency based on the detected sound absorption frequency. A control means for opening and closing the opening and closing means is provided. Here, the resonance frequency of each sound absorbing unit is autonomously adjusted based on the sound absorbing frequency detected for each sound absorbing unit.

According to a seventh aspect of the present invention, there is provided a resonator type sound absorbing device.
In any one of the constitutions (1) to (6), the resonator type sound absorbing device is characterized in that it is attached to a case member that covers a part or the whole of a sound source, or is configured as a part of the case member.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic diagram of a Helmholtz resonator. The Helmholtz resonator 1 has a resonance space 3 provided in a wall 2 and communicates the resonance space 3 with the outside through an inlet 4 provided in the wall 2. The Helmholtz resonator 1 absorbs sound by converting acoustic energy input into the resonance space 3 through the inlet 4 into heat energy by resonance.

The resonance frequency f of the Helmholtz resonator 1
₀ is given by the following _{equation (1)} , where c is the sound speed, V is the volume of the resonance space 3, V is the diameter of the inlet 4, and d is the depth of the inlet 4, that is, t is the thickness of the wall 2 at the inlet 4. expressed.

[0016]

(Equation 1)

In the equation (1), a is a constant.
The value is about 80 to 0.85. As is clear from the equation (1), the resonance frequency f ₀ decreases as the volume V of the resonance space 3 increases. Further, the resonance frequency f ₀ larger the diameter d of the inlet 4 is reduced along with reduced, the resonance frequency f ₀ larger the depth t increases the inlet 4 is reduced. That is, as the aspect ratio (t / d) of the entrance 4 increases, the resonance frequency f ₀ decreases.

According to the present invention, the resonance frequency f ₀ of the resonator type sound absorbing device using the Helmholtz resonator 1 is changed by changing the volume V of the resonance space 3 based on the above principle. It is an object of the present invention to make it possible to absorb sound in a lower frequency range than before by increasing the aspect ratio (t / d) of Aspect 4 as much as possible.

FIG. 2 and FIG. 3 schematically show a resonator-type sound absorbing device according to a first embodiment of the present invention. The resonator type sound absorbing device 11 includes a front wall 12 and a rigid wall 13 arranged in parallel with the front wall 12 with a space between the front wall 12 and the front wall 12.
And a connecting wall 14 extending in a direction perpendicular to the front wall 12 and the rigid wall 13 between the peripheral edges of the front wall 12 and the rigid wall 13 and connecting the peripheral edges of the front wall 12 and the rigid wall 13 to each other. . The front wall 12, the rigid wall 13, and the connecting wall 14 constitute a wall body 15. The rigid wall 13 is a wall that can reflect sound,
For example, it is formed of a synthetic resin plate (polymethyl methacrylate plate or the like) having a thickness of about 3 to 4 mm. Also, the front wall 12
Also, it is preferable that the rigid wall 13 be formed of the same material as that of the rigid wall 13 and have the same thickness.

In this case, the front wall 12 and the rigid wall 13 have a disc shape, while the connecting wall 14 has a cylindrical shape, and the area surrounded by the front wall 12, the rigid wall 13 and the connecting wall 14 is shown. Form a cylindrical resonance space 16, but the present invention is not limited to this. For example, the front wall 12 and the rigid wall 13 may have a rectangular plate shape, and the connecting wall 14 may have a rectangular cylindrical shape.

The front wall 12 is provided with a plurality of entrances 17 at predetermined intervals in the vertical and horizontal directions, respectively, and the front wall 12 is a porous wall. Also, behind the rigid wall 13,
Moving means 18 is provided for moving the rigid wall 13 in a direction to approach or separate from the front wall 12 while maintaining airtightness between the rigid wall 13 and the connecting wall 14. The moving means 18 includes, for example, a screw device rotatably screwing the male screw 18a to a female screw (not shown) provided on the rigid wall 13 side, and a step motor for rotating the male screw.

The above-described resonator type sound absorbing device 11 is one in which a plurality of Helmholtz resonators 1 of FIG. 1 are arranged in an array in the vertical and horizontal directions, respectively, and each sound absorbing portion 11 a ( For convenience, one block defined by a dotted line in FIG. 3) can be considered to constitute the Helmholtz resonator 1. Accordingly, when the volume of the resonance space for each individual sound absorbing portion 11a is V and the diameter and depth of each inlet 17 are d and t, respectively, the total volume of the resonance space 16 is divided by the number of the sound absorbing portions 11a. About the part 11a, the above equation 1
The following relationship holds. In addition, in the apparatus shown in FIGS. 2 and 3, no partition is actually provided between the adjacent sound absorbing portions 11a.

When the rigid wall 13 is moved toward or away from the front wall 12 as shown by the imaginary line in FIG. 2 by the moving means 18, and the volume of the resonance space 16 is increased or decreased, the sound absorbing portions 11a are correspondingly moved. The corresponding volume V also changes, and the resonance frequency f ₀ of the resonator type sound absorbing device 11 changes. The present resonator-type sound absorbing device 11 is suitable for use in an environment in which a temporal change and a positional change of a sound absorbing frequency, which is a frequency of a sound from a sound source (not shown), are relatively small.
The sound absorption frequency is periodically detected by a detector (not shown), and the rigid wall 13 is appropriately moved in accordance with the fluctuation of the sound absorption frequency, so that the resonance frequency f ₀ of the resonator type sound absorption device 11 is changed to the sound absorption at that time. What is necessary is just to control so that it may match with a frequency.
In the above embodiment, the resonance frequency is changed by moving the rigid wall 13, but instead the front wall 12 may be moved or the front wall 12 may be moved.
Alternatively, both the rigid wall 13 and the rigid wall 13 may be moved.

Hereinafter, the movement of the rigid wall 13, that is, the resonance space 1, will be described using an experimental device including the resonator type sound absorbing device 11.
The result of the actual measurement of the change in the resonance frequency f ₀ accompanying the change in the volume of No. 6 will be described. As shown in FIG. 4, the experimental device 21 is provided with the resonator type sound absorbing device 11 near one end of a cylindrical acoustic tube 22, and the connecting wall 14 is formed near one end of the experimental device 21. ing. A speaker 23 as a sound source is arranged at the other end of the acoustic tube 22, and a microphone 24 inserted into the acoustic tube 22 is connected to the detection device 25.

Here, the above-mentioned resonance frequency f ₀ was obtained by measuring the normal incidence sound absorption coefficient α ₀ . That is, when a sine-wave sound wave is generated by the speaker 23 and propagated through the acoustic tube 22 toward the resonator-type sound absorbing device 11, a standing wave is generated due to interference between the input wave and the reflected wave. The standing wave ratio n can be obtained by measuring the sound pressure with the microphone 24.

The acoustic reflection coefficient of the resonator type sound absorbing device 11 is R
Then, since R can be obtained from the standing wave ratio n, the normal incidence sound absorption coefficient α ₀ is expressed by the following equation (2).

[0027]

(Equation 2) Therefore, by tracking the change in the standing wave ratio n while changing the frequency of the sound from the microphone 24, it is possible to know the relationship between the frequency of the sound from the sound source and the normal incidence sound absorption coefficient α ₀ , and Frequency f of the sound absorber 11
₀ can be obtained as the frequency at which the normal incidence sound absorption coefficient α ₀ becomes maximum.

Next, while changing the gap size between the front wall 12 and the rigid wall 13, that is, the volume of the resonance space 16 in a plurality of ways, the resonance frequency f ₀ of the resonator type sound absorbing device 11 is obtained according to the above principle. The results are shown in FIG. The horizontal axis is speaker 2
3, the vertical axis is the normal incidence sound absorption coefficient α ₀ , and here, the gap between the front wall 12 and the rigid wall 13 is 6
mm, 8 mm, 10 mm, and 12 mm (curves I to IV, respectively). In each case, the resonance frequency f ₀ , that is, the peak value of the normal incidence sound absorption coefficient α ₀ , decreases as the gap, that is, the volume of the resonance space 16 increases.

FIG. 6 shows a second embodiment of the present invention.
The resonator-type sound absorbing device 11 of this embodiment is rigidly mounted on the wall 15 of the resonator-type sound absorbing device 11 of the first embodiment from the front wall 12 at right angles to the front wall 12 and the rigid wall 13. Wall 1
By providing a partition 26 extending over the entire thickness direction of the resonator type sound absorbing device 11 up to 3 and dividing the resonance space 16 into a plurality, the resonator type sound absorbing device 11 is divided into a plurality of sound absorbing units 11b. Here, each sound absorbing unit 1
A plurality of entrances 17 are provided in the front wall 12 corresponding to 1b, and each sound absorbing unit 11b includes a plurality of sound absorbing portions 11a.

The rigid wall 13 is divided into a plurality of divided bodies 13a for each sound absorbing unit 11b, and each divided body 13a approaches the front wall 12 while maintaining the airtightness between the connecting wall 14 and the partition 26. Alternatively, the moving means 18 for moving in the separating direction is provided independently for each divided body 13a. Further, a detector 27 for detecting the sound absorption frequency, which is the frequency of the sound from the sound source, is provided in the rigid wall 13 in an embedded manner or the like corresponding to each of the entrances 17, and moves in accordance with the sound absorption frequency detected by the detector 27. There is provided a control means 28 for controlling the driving of the means 18 and moving each of the divided bodies 13a such that the resonance frequency of the sound absorbing unit 11b matches the sound absorbing frequency.

In the above configuration, the resonator-type sound absorbing device 11 of the second embodiment detects the sound absorbing frequency of each sound absorbing unit 11b with the detector 27 even if the sound absorbing frequency changes in position. By moving the divided body 13a of the rigid wall 13 by the control means 28 via each moving device 18 according to the detection result, each sound absorbing unit 11b
Are controlled so that the resonance frequencies of the respective sound absorption units 11b coincide with the sound absorption frequency at the position of the sound absorption unit 11b.

A plurality of detectors 27 are provided for each sound absorbing unit 11b.
This is because it is preferable to detect the sound absorption frequency at a plurality of locations of each sound absorption unit 11b in order to make the resonance frequency of each sound absorption unit 11b an optimum value when the distribution of the sound absorption frequency exists within the sound absorption units. However, each sound absorbing unit 11b
Is sufficiently small, only one detector 27 may be provided for each sound absorbing unit 11b.

In the second embodiment, the rigid wall 1
3 is divided into divided bodies 13a for each of the sound absorbing units 11b, and the divided bodies 13a are moved independently of each other. However, the front wall 12 is divided into divided bodies for each of the sound absorbing units 11b. The body may be moved.

In order for the resonator type sound absorbing device 11 to absorb noise in a low frequency range, the diameter d of the inlet 17 is reduced while the depth of the inlet 17 is reduced, as is apparent from the equation (1). It is necessary to increase t to increase the aspect ratio (t / d). However, when the depth t is increased, the thickness of the front wall 12 increases, and the resonator type sound absorbing device 1
The overall size of 1 increases. Therefore, in order to increase the aspect ratio (t / d) by setting the depth t to a certain limit or less, it is preferable that the diameter d of the inlet 17 be as small as possible, for example, about several tens μm to 100 μm or less.

As described above, by reducing the volume of the resonance space 16 by moving the rigid wall 13 or the like, the resonance frequency f ₀ can be increased to cope with a high frequency range. By making the diameter d of 17 smaller and making it possible to cope with a low frequency range, the frequency range of sound that can be coped with by the resonator type sound absorbing device 11 can be expanded as a result. Further, as the diameter d of the inlet 17 becomes smaller, it is possible to respond more finely to the positional change of the sound absorption frequency. Therefore, it is preferable to make the diameter d of the inlet 17 as small as possible.

Here, in order to form an entrance 17 having a small diameter d in the front wall 12 having a thickness t as small as possible, for example, a synchrotron radiation light source (hereinafter, referred to as an SR light source)
It is preferable to use an X-ray lithography method using
That is, as shown in FIG. 7, a small SR light source 31 (for example, having an energy of about 0.6 GeV, a radiation spectrum having a peak wavelength of about 1.5 nm, and a spot size of about 30 mm × 5 mm) ), Through a X-ray mask 32 having a large number of holes 32a, a polymethyl methacrylate plate 33 (hereinafter, PMMA plate 33), which is a material of the front wall 12, is irradiated with SR light, and then is irradiated with a predetermined developer, for example. After developing the PMMA plate 33 for about several hours, as shown in FIG.
A hole 33a is formed in the PMMA plate 33 at a position irradiated with the SR light via the. This PMMA plate 33 is attached to the front wall 12.
(The hole 33a becomes the inlet 17).

As the X-ray mask 32, for example, a copper plate or other metal plate having a hole 32a having a diameter of about several tens μm to 100 μm and a thickness of about 100 to 200 μm can be used. PMMA plate 3
3, a hole 33a having a diameter of about 10 μm to 100 μm or less.
Can be formed in large numbers. The thickness of the PMMA plate 33 is, for example, about 3 to 4 mm or less, and the aspect ratio of the hole 33a can be about 10 to 100, depending on the diameter of the hole 33a. In the present invention, by setting the aspect ratio of the hole 33a to about 100 at the maximum,
It becomes possible to absorb noise in a low frequency range of about 0 to 300 Hz.

FIG. 9 shows a third embodiment of the present invention.
The resonator-type sound absorbing device 41 of this embodiment is configured such that, for example, the peripheral portions of a front wall 42 and a rigid wall 43, both of which have a disc shape, are connected to each other by a cylindrical connecting wall 44, so that these front walls 42 A cylindrical space surrounded by a wall body 45 including a rigid wall 43 and a connecting wall 44 is defined as a resonance space 46. Further, a disk-shaped partition wall 47 is provided between the front wall 42 and the rigid wall 43 in the resonance space 46, and the resonance space 46 is divided into a first space 48 between the front wall 42 and the partition wall 47, and the partition wall 47 and the rigid wall. The space 43 is divided into a second space 49. Here, the front wall 42 and the rigid wall 43 can be formed of, for example, a synthetic resin plate having a thickness of about 3 to 4 mm, as in the first embodiment. It can be formed of a Si plate of about 0.5 mm.

A plurality of entrances 50 are formed in the front wall 42, a plurality of communication holes 51 are formed in the partition wall 47, and a plurality of small opening / closing actuators 52 (opening / closing means) for opening and closing the communication holes 51 are provided. Provided. As shown in FIG.
The opening / closing actuator 52 includes a metal layer 52a (not shown).
It is composed of three layers sandwiched between two polyimide layers (insulating layers) in a sandwich shape from above and below, and is arranged on a partition wall 47 serving as a substrate. In this embodiment, the insulating layer 47a is formed over the partition wall 47; however, the insulating layer 47a is not necessarily provided.

The opening / closing actuator 52 having the three-layer structure has a substantially T-shaped base 53 fixed on a partition 47 and a long opening / closing valve 5 connected to the base 53 through a bent portion 54.
The on-off valve portion 55 is formed in a curved shape by curling in advance. Thereby, at all times, that is, the switch 5
When the switch 6 is turned off and not energized, the on-off valve unit 5 is turned on as shown by the solid line in FIG.
5 is curved to open the communication hole 51. On the other hand, when the switch 56 is turned on and power is supplied between the partition 47 and the metal layer 52a of the opening / closing actuator 52 by the power supply 57, the opening / closing valve portion 55 is adsorbed by the partition 47 as shown by a virtual line in FIG. , The communication hole 51 is closed. In this embodiment, the partition 47 itself is used as a counter electrode layer of the opening / closing actuator 52, but the counter electrode layer may be laminated on the partition 47 separately from the partition 47.

In the above-described resonator type sound absorbing device 41, each opening / closing actuator 52 is opened to open the first and second spaces 48,
Assuming that the first and second spaces 49 and 49 are in communication, the first and second spaces 48 and 49
Becomes a substantial resonance space, and the resonance frequency f ₀ of the resonator type sound absorbing device 41 has a relatively small value. On the other hand, each opening / closing actuator 52 is closed to close the first space 48 and the second space 49.
Is cut off, only the first space 48 becomes a substantial resonance space, and the volume of the resonance space is reduced. Therefore, the resonance frequency f ₀ of the resonator type sound absorbing device 41 is set to a value larger than when the opening / closing actuator 52 is opened. Become. As described above, in the present embodiment, the resonance frequency f ₀ of the resonator type sound absorbing device 41 can be changed by opening and closing the communication hole 51 with the opening and closing actuator 52.

Next, an experimental result of measuring a change in resonance frequency when the communication hole 51 is opened and closed by the opening and closing actuator 52 in the resonator type sound absorbing device 41 is shown. In this experiment, 400 mm was applied to the front wall 42 made of a 1 mm thick PMMA plate.
In addition to providing the inlet 50 having a diameter of 100 μm, the partition 47 made of a PMMA plate having a thickness of 1 mm is provided with 25 communication holes 51 having a diameter of 1 mm, and an opening / closing actuator 52 is provided corresponding to each communication hole 51. The sound absorption frequency and the normal incidence sound absorption were changed by changing the sound absorption frequency in the same manner as in the experimental apparatus of FIG. The relationship with the rate α ₀ was measured.

In FIG. 11, the horizontal axis represents the sound absorption frequency, and the vertical axis represents the normal incidence sound absorption coefficient α ₀ , as described above.
The peak at ₀ is the resonance frequency. A curve I in FIG. 11 indicates a characteristic when the communication hole 51 is closed by the opening / closing actuator 52,
Curve II shows the characteristics when the communication hole 51 is opened, and it can be seen that the resonance frequency becomes lower when the communication hole 51 is opened.

FIG. 12 shows a fourth embodiment. In this embodiment, the resonator type sound absorbing device 4 of the third embodiment is used.
In the wall 45 of FIG. 1, a partition 58 is provided which extends perpendicularly to the front wall 42 and the partition wall 47 and extends over the entire area in the thickness direction of the resonator type sound absorbing device 41, and the resonator type sound absorbing device 41 is provided to a plurality of sound absorbing units 41a. Divided. Then, one or a plurality of inlets 50 are provided in the front wall 42 for each sound absorbing unit 41a.
The partition wall 47 is provided with one or a plurality of communication holes 51, and an opening / closing actuator 52 for opening and closing each communication hole 51 is provided.

In addition, one or a plurality of detectors 58 for detecting the sound absorption frequency are provided on the front wall 42 or the like corresponding to each sound absorbing unit 41a, and these detectors 58 are provided.
In response to the detection result, a control means 60 is provided for opening and closing the opening / closing actuator 52 of each sound absorbing unit 41a and controlling the resonance frequency of each sound absorbing unit 41a so as to match the sound absorbing frequency at the position of the sound absorbing unit 41a. ing. According to this embodiment, even when the sound absorption frequency changes in position, the resonance frequency can be individually controlled for each sound absorption unit 41a, and the control of the resonance frequency is performed based on the detection result of the detector 58. It has the advantage of being autonomous.

It should be noted that the third and fourth embodiments are common.
In the sound absorber type sound absorbing device 41, only one partition wall 47 is provided and shared.
Sound frequency f₀Was changed in two steps,
Provide two or more 47 and make the resonance space 46 into three or more spaces
The partition walls 47 are individually opened and closed in the communication holes 51 of the individual partition walls 47.
By providing the actuator 52, the resonance frequency f ₀
Can be changed in three or more steps. Also open
As the closing actuator 52, the above-described on-off valve portion 55
In addition to those that deform a curved or linear shape,
Various types of opening and closing actuators, such as sliding type
Data can be used.

The resonator type sound absorbing device 1 of each of the above embodiments.
Specifically, for example, the side walls 6 in the engine room 61 (case member) of the automobile as shown in FIG.
1a or the back surface of the lid 61b, or as shown in FIG. 14, a case member 65 of an aircraft turboplot engine 64 having a turbine 62, a fan 63, and the like. Also, a part of the case member itself of these various engines and the like can be constituted by the resonator type sound absorbing devices 11 and 41.

[0048]

According to the first aspect of the present invention, there is provided a resonator type sound absorbing device in which a front wall, a rigid wall opposed to the front wall at a distance from the front wall, and peripheral edges of the front wall and the rigid wall are connected. The space surrounded by the wall consisting of the connecting wall that makes
The front wall is provided with an entrance for communicating the resonance space with the outside, and at least one of the front wall and the rigid wall can be moved in a direction approaching or separating from the other side while maintaining airtightness with the connection wall. By moving at least one of the front wall or the rigid wall to increase or decrease the distance between the front wall and the rigid wall, and changing the volume of the resonance space, the resonance of the resonator type sound absorbing device is improved. Since the frequency can be changed, for example, even when the sound absorption frequency, which is the frequency of the sound from the sound source, changes with time, the resonance frequency of the resonator-type sound absorption device is changed in accordance with the change, so that it can be adapted. Sound absorption processing can be realized.

According to a second aspect of the present invention, in the resonator type sound absorbing device, the front wall and the rigid wall extend from the front wall to the hard wall substantially in the thickness direction of the resonator type sound absorbing device. By providing a partition, the resonator-type sound absorbing device is divided into a plurality of sound absorbing units, an entrance of the front wall is provided corresponding to each sound absorbing unit, and at least one of the front wall or the rigid wall is provided for each sound absorbing unit. Since each divided body of the front wall or the rigid wall is configured to be movable independently of each other, for example, even when the sound absorbing frequency changes in position, each sound absorbing unit is formed. By changing the volume of each resonance space independently and matching the resonance frequency of each sound absorption unit with the sound absorption frequency at the position, adaptive sound absorption corresponding to the sound absorption frequency that changes positionally Management is possible.

According to a third aspect of the present invention, there is provided a resonator type sound absorbing device.
In the configuration of the above, a detector for detecting the sound absorption frequency that is the frequency of the sound from the sound source is provided for each sound absorption unit, so that the resonance frequency of each sound absorption unit matches the sound absorption frequency based on the detected sound absorption frequency. Since the control means for moving the front wall or the rigid wall divided body is provided, the resonance frequency of each sound absorbing unit matches the sound absorbing unit at the position based on the sound absorbing frequency detected by the detector. Control can be performed autonomously.

According to a fourth aspect of the present invention, a space surrounded by a wall including a front wall is used as a resonance space, and an entrance is provided in the front wall to communicate the resonance space with the outside.
The resonance space is divided into a plurality of parts by providing a partition wall substantially parallel to the front wall in the wall body, and a communication port for communicating the spaces on both sides is provided on the partition wall, and an opening / closing means for opening and closing the communication port is provided. When the communication port is opened, the space on both sides of the partition wall becomes a resonance space, and when the communication port is closed by the opening / closing means, only the space on the front wall side with the partition wall as a boundary is substantial. Since it becomes a resonance space, the resonance frequency of the resonator type sound absorbing device can be changed by opening and closing the communication port to change the volume of the substantial resonance space, for example, the sound absorbing frequency changes every moment. Even in such a case, adaptive sound absorption processing corresponding to this is possible.

According to a fifth aspect of the present invention, there is provided a resonator type sound absorbing device.
In the above structure, a partition is provided in the wall body, which extends substantially perpendicularly to the front wall and the partition wall over the entire area in the thickness direction of the sound absorbing unit, and the resonator type sound absorbing device is divided into a plurality of sound absorbing units. Since the entrance of the front wall, the communication port of the partition and the opening / closing means for opening / closing the communication port are provided in correspondence with the unit, for example, in a case where the sound absorption frequency changes in position. Also, by individually opening and closing the communication port by the opening / closing means for each sound absorbing unit, individually controlling the resonance frequency of each sound absorbing unit and realizing an optimum sound absorbing process at each position around the sound source. Becomes possible.

According to a sixth aspect of the present invention, there is provided a resonator type sound absorbing apparatus.
In the configuration of the above, a detector for detecting the sound absorption frequency that is the frequency of the sound from the sound source is provided for each sound absorption unit, so that the resonance frequency of each sound absorption unit matches the sound absorption frequency based on the detected sound absorption frequency. Since the control means for opening and closing the opening / closing means is provided, based on the sound absorbing frequency detected by the detector, the control for matching the resonance frequency of each sound absorbing unit with the sound absorbing unit at the position is performed autonomously. It can be carried out.

According to the seventh aspect of the present invention, there is provided a resonator type sound absorbing device.
In any one of the constitutions from 1 to 6, the resonator type sound absorbing device is attached to a case member covering a part or the whole of the sound source, or is configured as a part of the case member. There is an advantage that a mold type sound absorbing device can be provided, and no extra space is required for sound absorbing processing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a general Helmholtz resonator

FIG. 2 is a schematic longitudinal sectional view of the resonator type sound absorbing device according to the first embodiment of the present invention.

FIG. 3 is a schematic front view of the resonator-type sound absorbing device according to the first embodiment.

FIG. 4 is a schematic longitudinal sectional view showing an experimental apparatus including the resonator-type sound absorbing device of the first embodiment.

FIG. 5 is a graph showing the result of obtaining the relationship between the sound absorption frequency and the normal incidence sound absorption coefficient while changing the gap between the front wall and the rigid wall using the experimental apparatus.

FIG. 6 is a schematic longitudinal sectional view showing a resonator type sound absorbing device according to a second embodiment of the present invention.

FIG. 7 is an explanatory view showing a state in which an entrance is formed in a front wall using an X-ray lithography method.

FIG. 8 is an explanatory view showing a subsequent procedure for forming the entrance.

FIG. 9 is a schematic longitudinal sectional view showing a resonator type sound absorbing device according to a third embodiment of the present invention.

FIG. 10 is an enlarged perspective view showing an opening / closing actuator in a resonator type sound absorbing device according to a third embodiment.

FIG. 11 is a graph showing an experimental result in which a relationship between a sound absorption frequency and a normal incidence sound absorption coefficient is obtained while opening and closing an opening / closing actuator of the resonator type sound absorbing device according to the third embodiment.

FIG. 12 is a schematic longitudinal sectional view of a resonator type sound absorbing device according to a fourth embodiment of the present invention.

FIG. 13 shows a first example of the resonator type sound absorbing device of each of the above embodiments.
The perspective view showing the example of application of.

FIG. 14 shows a second example of the resonator type sound absorbing device of each of the above embodiments.
The perspective view showing the example of application of.

[Explanation of symbols]

 11, 41 Resonator type sound absorbing device 11b, 41a Sound absorbing unit 12, 42 Front wall 13, 43 Rigid wall 13a Divided body 14, 44 Connecting wall 15, 45 Wall 16, 46 Resonant space 17, 50 Inlet 18 Moving means 28, Reference Signs List 60 control means 47 partition 51 communication hole 52 opening / closing actuator (opening / closing means)

Claims (7)

[Claims] 1. A wall comprising a front wall, a rigid wall opposed to the front wall at a distance from the front wall, and a connecting wall connecting peripheral edges of the front wall and the rigid wall. The front space is provided with an entrance for communicating the resonance space with the outside, and at least one of the front wall and the rigid wall is kept airtight between the front wall and the connecting wall while the other space is provided as a resonance space. A resonator type sound absorbing device characterized by being movable in a direction approaching or moving away from the device. 2. The resonator-type sound absorbing device according to claim 1, wherein a partition extending in the thickness direction of the resonator-type sound absorber from the front wall to the rigid wall substantially perpendicular to the front wall and the rigid wall is provided in the wall body. Dividing the sound absorbing device into multiple sound absorbing units,
Along with providing an entrance of the front wall corresponding to each sound absorbing unit, at least one of the front wall or the rigid wall is configured as a divided body divided for each sound absorbing unit, and each divided body of the front wall or the rigid wall is formed. The resonator type sound absorbing device according to claim 1, wherein the sound absorbing device is movable independently of each other. 3. A detector for detecting a sound absorption frequency which is a frequency of a sound from a sound source is provided for each sound absorption unit, and a resonance frequency of each sound absorption unit is matched with the sound absorption frequency based on the detected sound absorption frequency. 3. The resonator type sound absorbing device according to claim 2, further comprising control means for moving the front wall or the rigid wall divided body. 4. A space surrounded by a wall including a front wall is defined as a resonance space, an entrance is provided in the front wall to communicate the resonance space with the outside, and the wall is substantially parallel to the front wall. A resonant partition which divides the resonance space into a plurality of sections and provides a communication port for communicating the spaces on both sides with the partition, and an opening / closing means for opening and closing the communication port. . 5. A partition extending in the thickness direction of the sound absorbing unit in a direction substantially perpendicular to the front wall and the partition wall in the wall body to divide the resonator type sound absorbing device into a plurality of sound absorbing units. 5. The resonator type sound absorbing device according to claim 4, further comprising an inlet of said front wall, a communication port of said partition wall, and said opening / closing means for opening and closing said communication port corresponding to said sound absorbing unit. 6. A detector for detecting a sound absorption frequency which is a frequency of a sound from a sound source is provided for each sound absorption unit, and a resonance frequency of each sound absorption unit matches the sound absorption frequency based on the detected sound absorption frequency. 6. The resonator type sound absorbing device according to claim 5, further comprising control means for opening and closing said opening and closing means. 7. The sound absorber according to claim 1, wherein the sound absorber is mounted on a case member that covers a part or the whole of the sound source, or is configured as a part of the case member. Resonator type sound absorber.