JP3904307B2 - Noise reduction type duct - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a noise reduction type duct provided with a noise reduction device that is provided in an air passage of an air conditioner / ventilator and reduces noise transmitted through the air passage.
[0002]
[Prior art]
Conventionally, as disclosed in JP-A-8-248964, a sound absorbing material is attached to the inner surface of a duct provided in an air passage of an air conditioner / ventilator and an active noise reduction device is provided. Yes. The noise reduction device detects noise with a detection microphone, and emits a control sound having an opposite phase to the noise and the same amplitude from the speaker into the duct. Then, the synthesized sound of the noise and the control sound is detected by the error microphone, and the synthesized sound is fed back and controlled to reduce the synthesized sound level.
[0003]
[Problems to be solved by the invention]
However, in such conventional devices, in order to obtain a noise reduction effect by sound wave interference by the noise reduction device, the coherence of the signal output between the detection microphone and the error microphone must be high. When the detection microphone picks up the solid propagation sound propagating through the duct body, there is a problem that coherence is lowered and a sufficient noise reduction effect cannot be obtained. In addition, when the error microphone picks up the solid propagation sound, a control sound including the same amplitude component is output in the opposite phase to the solid propagation sound, and this signal component is fed back, so that a sufficient noise reduction effect is obtained. There was no problem.
[0004]
The subject of this invention is providing the noise reduction type | mold duct which improves the reduction of the noise by a noise reduction apparatus.
[0005]
[Means for Solving the Problems]
In order to achieve this problem, the present invention has taken the following measures in order to solve the problem. That is,
In the noise reduction type duct that is provided in the air passage of the air conditioning and ventilation device, detects noise with a microphone, emits control sound from the speaker according to the noise, and reduces noise,
An inner duct formed of a porous material;
An outer duct formed on the inner duct and formed of a damping steel plate,
A noise reduction type duct characterized in that a noise reduction chamber is formed between the inner duct and the outer duct, the speaker is attached to the outer duct, and a control sound is emitted from the speaker into the outer duct. That is it.
[0006]
The porous material may be a rigid porous material having a large number of holes formed therethrough. Alternatively, a support member that supports the microphone may be formed of a damping steel plate.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, reference numeral 1 denotes an air conditioner / ventilator main body, and conditioned air from a fan 2 in the air conditioner / ventilator main body 1 is supplied to a room 6 via a blower passage 4. The air passage 4 is formed by a plurality of ducts 8, 10, 12, and the like, and one of the ducts 10 is provided with a noise reduction device 14.
[0008]
The duct 10 includes an inner duct 16 having the same cross-sectional area as that of the front and rear ducts 8 and 12. The inner duct 16 is connected to the front and rear ducts 8 and 12 via adjusters 18 and 20. ing. Both adjusters 18 and 20 have a structure that can be adjusted and connected when the inner duct 16 and the front and rear ducts 8 and 12 are connected.
[0009]
The inner duct 16 is formed of a porous material, and in the present embodiment, an open-cell foamed aluminum material is used as the porous material. As the porous material, it is sufficient to use a porous material that has a large number of holes penetrating and is at least rigid enough to be self-supporting, and is not limited to a foamed aluminum material, but may be a porous ceramic plate or the like. In particular, a foamed aluminum material is preferable.
[0010]
In addition, the duct 10 includes an outer duct 22 that is sheathed on the inner duct 16, and a sound deadening chamber 24 is formed between the inner duct 16 and the outer duct 22. The sound deadening chamber 24 communicates with the inside of the inner duct 16 through a large number of holes in the inner duct 16. The volume of the muffler chamber 24 is sized according to the frequency band to be muffled so as to function as a passive muffler.
[0011]
The outer duct 22 is formed of a damping steel plate in which a resin film or the like is sandwiched between two steel plates, and the inner duct 16 and the outer duct 22 are connected by a plurality of leg members 26 formed of a foamed aluminum material. Has been. Reinforcing members 28 are attached to the outer duct 22 at predetermined intervals to further reduce the solid propagation sound.
[0012]
Further, a detection microphone 30 is provided on the air conditioning / ventilating device main body 1 side of the duct 10. The detection microphone 30 penetrates the inner duct 16 through the inner duct 16 by a support member 32 having one end attached to the outer duct 22. Arranged in the center of the duct 16. This support member 32 is formed of a damping steel plate.
[0013]
An error microphone 34 is provided at the center of the inner duct 16 on the outlet side of the duct 10, and the error microphone 34 is also attached to the outer duct 22 by a support member (not shown) formed of a damping steel plate. A speaker 36 is attached to the outer duct 22 between the detection microphone 30 and the error microphone 34 so that sound can be emitted from the speaker 36 into the outer duct 22.
[0014]
The detection microphone 30, the error microphone 34, and the speaker 36 are connected to a noise reduction circuit 38, and the noise reduction circuit 38 generates a control sound having an opposite phase and the same amplitude with respect to the noise signal detected by the detection microphone 30. The control sound is generated and output to the speaker 36. Then, the synthesized sound of the noise and the control sound in the duct 10 is detected by the error microphone 34, and the synthesized sound signal is fed back to control to reduce the synthesized sound level.
[0015]
Next, the operation principle of the noise reduction type duct of this embodiment described above will be described. First, when the air conditioner / ventilator main body 1 is operated, the conditioned air flows into the inner duct 16 through the duct 8 and the adjuster 18, and is supplied to the room 6 through the adjuster 20 and the duct 12.
[0016]
At that time, noise generated in the air conditioner / ventilator main body 1 and the like enters the inner duct 16 through the duct 8 and the adjuster 18 together with the conditioned air. This noise is detected by the detection microphone 30, and based on the detected noise signal, the noise reduction circuit 38 generates a control sound having an opposite phase and the same amplitude, and outputs it to the speaker 36.
[0017]
The control sound and noise emitted from the speaker 36 interfere with each other, and the noise is reduced. Further, the synthesized sound of the control sound and the noise is detected by the error microphone 34, and the detected synthesized sound signal is fed back to the noise reduction circuit 38 to control to reduce the synthesized sound level.
[0018]
On the other hand, the noise is not limited to the case of propagating with the conditioned air, but the noise generated in the air conditioning / ventilating device main body 1 may be solidly propagated to the duct 10 via the duct 8 and the adjuster 18. The solid-propagated noise is attenuated and reduced by the outer duct 22 made of a damping steel plate. In addition, noise generated by the disturbance of the flow of conditioned air may cause the duct 10 to vibrate and propagate through the solid. Such noise is also attenuated and reduced by the outer duct 22 made of a damping steel plate.
[0019]
Furthermore, when the control sound is generated from the speaker 36, the vibration of the speaker 36 may be propagated to the outer duct 22, but such noise is also attenuated and reduced by the outer duct 22 made of damping steel plate. . In addition, the vibration of the outer duct 22 may propagate to the detection microphone 30 via the support member 32. Since the support member 32 is formed of a damping steel plate, the vibration is attenuated, and the vibration propagated through the solid by the detection microphone 30 is picked up as noise, thereby preventing the coherence from being lowered. The same applies to the error microphone 34.
[0020]
On the other hand, the noise that has entered the inner duct 16 along with the flow of the conditioned air enters the silencer chamber 24 through the hole of the inner duct 16 and is attenuated by interference of reflected sound waves from the walls at both ends of the silencer chamber 24. The Thereby, the duct 10 also works as a passive silencer, and further reduces noise in combination with noise reduction by the noise reduction device 14.
[0021]
As shown in FIG. 3, the detection microphone 30 may be provided on the upstream adjuster 18, and the error microphone 34 may be provided on the downstream adjuster 20. As a result, it is possible to reduce the sound generated when the speaker 36 is driven and propagates through the duct 10 and is detected by the detection microphone 30 and the error microphone 34, thereby further reducing vibration and noise.
[0022]
As shown in FIG. 4, instead of the leg members 26 and the reinforcing members 28 described above, a plurality of L-shaped steel support members 40 are provided on the inner surface of the outer duct 22 at predetermined intervals. The inner duct 16 is supported by the support member 40 and the sound deadening chamber 24 is divided into small sections. Thereby, sound absorption performance can be improved.
[0023]
The present invention is not limited to such embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention.
[0024]
【The invention's effect】
As described above in detail, the noise reduction type duct according to the present invention reduces the solid propagation sound by the outer duct made of the damping steel plate and picks up the vibration propagated by the solid as a noise to prevent the coherence from being lowered. At the same time, since the duct also functions as a passive silencer, there is an effect of further reducing noise in combination with noise reduction by the noise reduction device. Further, since the outer duct is formed of the damping steel plate, the increase in the duct weight is small.
[0025]
When the cross-sectional areas of the front and rear ducts and the inner duct are the same, an increase in fluid resistance can be suppressed. Moreover, it can reduce in weight by forming a porous material with a foaming aluminum material. Furthermore, by forming the microphone support member from a damping steel plate, it is possible to further prevent a decrease in coherence.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a noise reduction type duct as an embodiment of the present invention.
2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is a schematic configuration diagram of a noise reduction type duct as another embodiment.
FIG. 4 is a schematic configuration diagram of a noise reduction type duct as another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Air-conditioning / ventilation apparatus main body 4 ... Airflow path 6 ... Indoor 8, 10, 12 ... Duct 14 ... Noise reduction device 16 ... Inner duct 18, 20 ... Adjuster 22 ... Outer duct 24 ... Silence room 30 ... Detection microphone 32 ... Support Member 34 ... Error microphone 36 ... Speaker 38 ... Noise reduction circuit

Claims (3)

In the noise reduction type duct that is provided in the air passage of the air conditioning and ventilation device, detects noise with a microphone, emits control sound from the speaker according to the noise, and reduces noise,
An inner duct formed of a porous material;
An outer duct formed on the inner duct and formed of a damping steel plate,
A noise-reducing duct characterized in that a noise reduction chamber is formed between the inner duct and the outer duct, the speaker is attached to the outer duct, and a control sound is emitted from the speaker into the outer duct.   The noise-reducing duct according to claim 1, wherein the porous material is a rigid porous material having a large number of holes formed therethrough.   The noise reduction type duct according to claim 1 or 2, wherein the supporting member for supporting the microphone is formed of a damping steel plate.

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