JP2005037447A - Noise controller of air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise from an air conditioner by monopole sound sources in each of which there are integrated a microphone that detects sound waves in a sound field, a planar speaker that is made of piezoelectric elements to transmit sound waves into the sound field, and a control circuit that has a control loop characteristic to generate noise control signals used to amplify output signals of the microphone and to make sound waves transmitted from the speaker interfere in the sound field. <P>SOLUTION: A noise control boundary is formed by arranging a plurality of monopole sound sources 3 in the longitudinal direction of a cross flow air blower 2 of an air conditioner 1 so that air flow being blown from the cross flow air blower 2 is sandwiched at an interval which is smaller than 1/4 wavelength of the sound equivalent to the upper value of a noise control frequency band. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device that performs active noise control in a three-dimensional space, for example, to a noise control device for an air conditioner that actively cancels noise caused by a blower fan of an air conditioner or improves sound quality. It is.
[0002]
[Prior art]
In recent years, there has been proposed an active noise reduction method that uses sound wave properties to cancel the sound with sound, actively canceling the noise caused by the blower fan of the air conditioner, or improving the sound quality of the air conditioner noise. A control device has been proposed (see, for example, Patent Document 1). Hereinafter, a conventional noise control device for an air conditioner will be described with reference to FIG. FIG. 10 is a cross-sectional view showing a configuration of a conventional noise control device for an air conditioner. In FIG. 10, as the noise detecting means, there are provided a rotating sound detecting pickup 22a of the once-through fan and an electromagnetic sound detecting pickup 22b of the motor 21 of the once-through fan. In addition to this, a plurality of sound generating means 20 and a plurality of silencing effect detections are provided. Means 23 are also provided. The plurality of sound generating means 20 are arranged side by side in positions that do not obstruct the air flow. Further, a wind speed and pressure detection pickup 25 at the air outlet is provided, and by processing this output signal, the noise from the outlet can be predicted and the sound from the sounding means 20 can be silenced. The silencing effect detecting means 23 is installed at an appropriate position of the suction grille having the air filter 24.
[0003]
As one method of active silencing, a method of canceling sound with sound using the wave nature of sound when noise is propagated in one dimension such as an air conditioning duct has been put into practical use. The target active muffling is the interference of sound waves if the sounding means is aligned with the noise source, and sound waves having the same phase and amplitude and wavelength as the sound waves emitted from the noise source are emitted from the sounding means. Ideally, it is possible to mute the entire 3D space. However, in reality, it is impossible to match the positions of the sound generation means and the noise source. Therefore, in active silencing in a three-dimensional space, a plurality of sound generation means must be placed near the noise source. Don't be.
[0004]
Next, a control configuration for active silencing in a three-dimensional space will be described with reference to FIGS. 11 and 12. 11 and 12 are block diagrams showing a control configuration in a conventional noise control apparatus for an air conditioner. In the figure, it is composed of a blade sound pickup or electromagnetic sound pickup as an input system, a mute effect detection means as an error sensor system, and a fixed filter or adaptive filter or controller as a signal processing / control system.
[0005]
In addition, the conventional air conditioner to which the conventional three-dimensional active silencer is applied is arranged on the suction grill or the like that does not obstruct the air flow by using the sound transfer tube and active means and device necessary for active control. It was possible to reduce the installation restrictions in the air conditioner.
[0006]
Conventionally, there is a method using a monopole sound source (monopole method) as another active silencing method. The monopole method is composed of a speaker provided close to a microphone that detects external noise and a control circuit that adjusts the gain and phase so that the microphone input is minimized, and does not require an error microphone. There is a feature that it is possible to mute without depending on the acoustic path (see, for example, Patent Document 2).
[0007]
The control circuit for a monopole sound source is generally composed of an analog filter, and is limited to relatively narrow-band noise control in order to suppress the acoustic characteristics of a speaker that is a secondary sound source and monopole sound source oscillation suppression.
[0008]
Hereinafter, an active silencer using a conventional monopole sound source will be described with reference to FIG. FIG. 13 is a block diagram showing a conventional active silencer. In the figure, adaptive control using a digital filter is used as a control circuit for a monopole sound source. In addition, a single or multiple monopole sound sources using digital filters can be used to mute a wide range of spaces.
[0009]
[Patent Document 1]
Japanese Patent No. 3072174 [Patent Document 2]
JP-A-9-26793 [0010]
[Problems to be solved by the invention]
However, in the first conventional configuration described above, the noise detection means includes the rotational sound detection pickup 22a of the cross-flow fan, the electromagnetic sound detection pickup 22b of the motor 21 of the cross-flow fan, and the input of the wind speed and wind pressure detection pickup 25 at the air outlet. The noise from the outlet is predicted by a fixed filter, an adaptive filter, or a controller based on the input signals from the plurality of sound generating means 20, the plurality of muffler effect detecting means 23 and each pickup as an output system. It is necessary to have a technology to predict noise from the multi-input signal from the device, the mute error signal from the mute effect detection means and the wind speed / pressure, and the active control system for noise is very complicated. Had the problem of becoming.
[0011]
Further, at a plurality of points of the silencing effect detecting means 23 arranged on the suction grille far from the fan and fan motor 21 considered as a noise source of the air conditioner, the rotating sound of the fan and the electromagnetic sound of the fan motor 21 are obtained. Since other noises are also detected, a silencing error always occurs and the noise reduction effect cannot be expected.
[0012]
In addition, the active means and devices necessary for the use and active control of the sound transmission tube can be placed in a place where the air flow of the air conditioner is not obstructed, for example, on the suction grill. There was also a problem that a complicated design for routing the sound transmission tube in the air conditioner and a space required for active control and an installation space for the device had to be secured.
[0013]
In the configuration of the monopole sound source using adaptive control by the second conventional digital filter described above, a time delay relating to the necessary calculation time required for A / D conversion, D / A conversion, and filtering occurs, and the distance between the microphone and the speaker The silencing frequency range with a monopole sound source of 3cm is extremely low frequency noise, 0 <f ≤ 50Hz, centered around Nz · 2Nz sound (N: fan rotation speed (rps) z: number of fan blades) of several hundred Hz However, there is a problem that the noise reduction effect is hardly obtained for the noise (A characteristic) of the air conditioner spreading over a broad range.
[0014]
Even if the required calculation time required for A / D conversion, D / A conversion, filtering, etc., can be silenced to around 1 kHz due to dramatic advances in DSP, it is necessary to perform noise control in a three-dimensional space. For example, it is necessary to arrange a plurality of monopole sound sources made of expensive DSP around the air outlet of the air conditioner, and there is a problem that it takes considerable cost to control the noise of the air conditioner.
[0015]
In addition, the active control of noise by a monopole sound source suppresses the acoustic characteristics of the speaker that is the secondary sound source and the oscillation phenomenon of the monopole sound source itself. There is a problem that it is limited to a relatively narrow band and is not suitable for noise reduction over a wide band of an air conditioner.
[0016]
The present invention solves such a conventional problem, and provides a low-cost noise control means with a simple configuration of an air conditioner using a monopole sound source using an analog filter as a control circuit. With the goal.
[0017]
The present invention solves the conventional problems, and an object thereof is to provide a noise control device for an air conditioner having a higher noise reduction effect.
[0018]
It is another object of the present invention to provide a noise control device for an air conditioner that improves the degree of freedom of installation in the air conditioner.
[0019]
And this invention solves the conventional subject, and it aims at providing the noise control apparatus of the air conditioner over a wide band with a monopole sound source.
[0020]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a microphone for detecting sound waves in a sound field, a speaker for sending sound waves into the sound field, an output signal from the microphone, and interfering with sound waves sent from the speaker in the sound field. A monopole sound source integrated with a control circuit having a control loop characteristic for generating a noise control signal to be transmitted is traversed at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of the monopole sound source. A plurality are arranged in the longitudinal direction of the flow blower so as to sandwich the flow blown out by the cross flow blower of the air conditioner.
[0021]
Since the monopole sound source is composed of the control circuit using a microphone, a speaker, and an analog filter, the noise control device for an air conditioner can be realized with a very simple system and at a low cost. It is done.
[0022]
The monopole sound source itself can be made into a thin configuration by integrating a flat speaker composed of the piezo element or a thin speaker composed of a sandwich type magnetic circuit, a microphone, and a control circuit. By arranging a plurality of monopole sound sources in the longitudinal direction of the blower at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band, a plurality of monopole sound sources are provided in the vicinity of the cross flow blower. A noise control boundary is formed, and a noise control effect that spreads in a three-dimensional space from a noise emission point such as an air conditioner outlet and a suction port can be obtained.
[0023]
In addition, the thin monopole sound source improves the degree of freedom of installation of the monopole sound source in the air conditioner, and it is not necessary to use a sound transmission tube or the like, so the design of the air conditioner itself A degree of freedom is obtained.
[0024]
Furthermore, by arranging the thin monopole sound source so as to surround the air conditioner outlet at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band, With a simple configuration, a noise control boundary formed at the outlet of the air conditioner can be formed, and a noise control effect for noise spreading from the outlet to a three-dimensional space can be obtained.
[0025]
In order to solve the problem that the noise control band of the monopole sound source is limited to a narrow band, each group of monopole sound sources by noise control frequency band is sandwiched with a flow blown from the cross-flow fan of the air conditioner, and In the longitudinal direction of the cross flow blower of the air conditioner, the monopole sound sources are arranged at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of each group. Alternatively, the noise control frequency of each monopole sound source group so as to surround the outlet of the air conditioner sequentially from the monopole sound source group having a higher upper limit value of the noise control frequency band for the monopole sound source group by noise control frequency band They are arranged at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the band.
[0026]
With the above configuration, the noise control effect of the air conditioner over a wide frequency band can be obtained.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
First, the arrangement of the secondary sound source in the free sound field will be described. Patent Document 1 and the like describe that a plurality of secondary sound sources are disposed within at least half the wavelength of the noise to be silenced.
[0029]
On the other hand, FIG. 6 shows the theoretical noise reduction when the phase error and amplitude error in the active control of noise are used as parameters. For example, when an arbitrary noise and a sound generated from a secondary sound source have a phase error of 15 ° and an amplitude error of 20%, a noise reduction amount of about 10 dB can be obtained as a result of active noise control. In order to obtain a sufficient noise reduction effect by active noise control, it is desirable that the sound generated from the secondary sound source is at least within ± 45 ° (¼ wavelength) with respect to the noise to be silenced. I understand that. In other words, in active control of noise in a free sound field, in order to obtain a sufficient amount of noise reduction, it is necessary to surround the noise source with an interval within 1/4 wavelength of the noise to be silenced in order to obtain a sufficient amount of noise reduction. .
[0030]
(Embodiment 1)
FIG. 1 is a sectional view showing a noise control device for an air conditioner according to Embodiment 1 of the present invention, where 1 is an air conditioner, 2 is a cross flow fan of a cross flow fan, and 3 is a microphone. It is a monopole sound source in which a control circuit 11 having a control loop characteristic for generating a noise control signal that causes interference with a speaker in a sound field is integrated. The monopole sound source 3 has a sound corresponding to the upper limit value of the noise control frequency band of the monopole sound source 3 in the longitudinal direction of the cross flow blower 2 so as to face the flow 4 blown out from the cross flow blower 2. It arrange | positions in the vicinity of the crossflow fan 2 with the space | interval shorter than 1/4 wavelength. In the case of FIG. 1, a plurality of monopole sound sources 3 are arranged on the rear guider 5 and the water tray lower surface 6.
[0031]
Here, the structure of the monopole sound source 3 will be described with reference to FIG. Reference numeral 7 denotes a microphone that detects sound waves in the sound field, and reference numeral 9 denotes a flat speaker that includes a piezo element 8 that sends out sound waves in the sound field. As described above, in recent years, with the widespread use of portable terminals, sounding means using piezoelectric elements such as piezoelectric ceramics and piezoelectric films and sounding means using sandwich type magnetic circuits have been developed. In active control of noise, the back cavity 10 is also included. This makes it possible to construct a thin and compact secondary sound source. A monopole sound source composed of a speaker using a sandwich type magnetic circuit has a structure as shown in FIG.
[0032]
Reference numeral 11 denotes a control circuit having a control loop characteristic that amplifies the output signal of the microphone 7 and generates a mute signal that causes the sound wave transmitted from the speaker 9 to interfere in the sound field. The control circuit 11 composed of an analog circuit is disposed in the back cavity 10 or on the back of the monopole sound source 3 so that the microphone 7 and the speaker 9 can be integrated and thinned. It can be arranged on the lower surface of the water tray 6. As a result, the degree of freedom of arrangement of the monopole sound source and the degree of freedom of design of the air conditioner are increased, and the monopole sound source can be disposed in the vicinity of the noise source of the air conditioner.
[0033]
As described above, the microphone 7 of the monopole sound source 3 detects the noise 17 diffused from the outlet 15 of the air conditioner 1 by the arrangement of the noise control device in the air conditioner and the structure of the monopole sound source. Then, the control circuit 11 generates a noise control signal that causes interference at the position of the microphone 7 and generates a canceling sound toward the wind flow 4 from the speaker 9 that is a secondary sound source. The canceling sound forms a noise control region 18 in the 1/4 wavelength range of the sound corresponding to the upper limit value of the noise control frequency band with the microphone 7 as the center. A plurality of monopole sound sources 3 are blown out in the longitudinal direction of the cross flow fan 2 on the rear guider 5 and the water tray lower surface 6 at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band. A noise control boundary 18 facing the wind flow 4 is formed, and the noise 17 passing through the noise control boundary 18 is subjected to noise control, and mute or the sound quality is changed.
[0034]
FIG. 7 shows the flow velocity simulation analysis result of the air conditioner, and shows only the portion 13 where the flow velocity is large. The noise of the cross flow blower 2 of the air conditioner is generated when the vortex in the boundary layer of the flow, the acceleration motion of the wake vortex, the vortex flowing from the upstream, or the blade of the cross flow fan passes near the stabilizer 12 The flow inside the cross flow fan 2 and the vicinity of the discharge blade row, the rear guider 5 and the stabilizer 12 are portions 13 having a high flow velocity. It can be estimated that the noise source 1 is near the rear guider 5 and the stabilizer 6.
[0035]
FIG. 8 shows a flow of the monopole sound source 3 blown out from the rear guider 5 and the water tray lower surface 6 by a cross flow blower of an air conditioner at an interval shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band. It is sectional drawing of the model which verifies the noise reduction effect arrange | positioned so that it may be inserted | pinched. In the verification model, pseudo noise of the air conditioner is generated by the speaker 14 disposed in the discharge blade row portion as a pseudo noise source of the air conditioner. The evaluation point is a position 1 m in the horizontal direction and 0.8 m in the vertical direction from the front center of the air conditioner.
[0036]
FIG. 9 shows the noise control effect by the verification model, where (a) shows the noise control effect near the outlet, and (b) shows the noise control effect at the evaluation point. The noise control boundary 18 formed in the vicinity of the noise source, that is, the rear guider 5 and the water tray lower surface 6, immediately cancels the noise 17 radiated from the noise source, and has a noise control effect even in a space away from the air conditioner 1. It turns out that it is obtained.
[0037]
Therefore, a plurality of monopole sound sources 3 are arranged at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of the monopole sound source in the longitudinal direction of the cross flow fan 2 of the indoor blower 1. By disposing the noise near the noise source, the noise radiated from the noise source is silenced at the noise control boundary near the noise source, so that the noise propagating to the three-dimensional space can be suppressed and controlled.
[0038]
(Embodiment 2)
FIG. 2 shows a second embodiment of the present invention, in which a plurality of the monopole sound sources 3 are aired at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of the monopole sound source. The blowout port 15 of the harmony machine is enclosed.
[0039]
FIG. 3 shows a method of performing noise control by surrounding the air outlet 15 of the air conditioner 1 with a plurality of monopole sound sources 3. The noise 17 of the air conditioner is released from the outlet 15 into the three-dimensional space and diffuses. Noise from the air outlet 15 forms a noise control boundary 18 by a plurality of monopole sound sources 3 arranged so as to surround the air outlet 15.
[0040]
Therefore, according to the second embodiment, the noise control boundary 18 formed at the air outlet 15 has a relatively simple configuration in which a plurality of monopole sound sources 3 are arranged around the air outlet 15 of the air conditioner 1. Thus, it is possible to suppress and control noise propagating to the three-dimensional space.
[0041]
(Embodiment 3)
FIG. 15 shows a third embodiment of the present invention, in which a plurality of noise control band-specific monopole sound source groups 3, 3 ′, 3 ″ are sandwiched with a flow 4 that blows out from a cross-flow fan 2 of the air conditioner 1. Thus, in the longitudinal direction of the cross flow fan 2 of the air conditioner, the sound is arranged at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of each group of monopole sound sources.
[0042]
According to the third embodiment, even when the noise control frequency band of the monopole sound source is limited, a plurality of monopole sound source groups for each noise control band are arranged along the blowing direction from the cross-flow fan of the air conditioner. As a result, a wide-band noise control boundary is formed, and noise can be controlled over a wide band as in an air conditioner.
[0043]
(Embodiment 4)
FIG. 4 shows a fourth embodiment of the present invention, in which a plurality of noise control band-specific monopole sound source groups 3, 3 ′, 3 ″ are arranged so as to surround a blowout port 15 of an air conditioner. The monopole sound source groups having the highest band upper limit values are sequentially arranged at intervals shorter than ¼ wavelength of the sound corresponding to the upper limit value of the noise control frequency band of each monopole sound source group.
[0044]
For example, when the upper limit value of the noise control frequency band of the monopole sound source group 3, 3 ′, 3 ″ is 1000 Hz, 700 Hz, and 300 Hz, the 1/4 wavelength of the sound corresponding to each frequency is about 8 cm and about 12 cm. In order to form each noise control boundary corresponding to each group of monopole sound sources, a monopole with a short wavelength is connected to the air conditioner outlet in consideration of the finite size of the monopole sound source. The sound source group 3 must be arranged.
[0045]
According to the fourth embodiment, even when the noise control frequency band of the monopole sound source is limited, a wideband noise is set near the outlet of the air conditioner by a plurality of monopole sound source groups for each noise control band. A control boundary is formed, and noise can be controlled over a wide band like an air conditioner.
[0046]
(Embodiment 5)
FIG. 5 shows the structure of a monopole sound source composed of a flat speaker composed of piezo elements as shown in the first embodiment. 7 is a microphone that detects sound waves in the sound field, 9 is a planar speaker that includes a piezo element 8 that sends out sound waves in the sound field, and 11 is an amplifier that amplifies the output signal of the microphone 7 and from the speaker 9. This is a control circuit 11 having a control loop characteristic for generating a mute signal that causes a transmitted sound wave to interfere in the sound field. By arranging the control circuit 11 constituted by an analog circuit in the back cavity 10 or on the back surface of the monopole sound source 3, the microphone 7 and the speaker 9 can be integrated and thinned.
[0047]
Therefore, according to the fifth embodiment, the rear guider 5 and the water tray 6 can be arranged on the lower surface, and the degree of freedom of the monopole sound source arrangement and the design of the air conditioner is increased, and above all, The effect of suppressing and controlling the noise propagating to the three-dimensional space can be expected by the noise control boundary by a plurality of monopole sound sources arranged in the vicinity of the noise source.
[0048]
(Embodiment 6)
FIG. 14 shows the structure of a monopole sound source composed of a thin speaker 9 ′ composed of a sandwich type magnetic circuit. The same effect as that of the fourth embodiment can be expected by integrating and thinning the control circuit 11, the microphone 7, and the speaker 9 configured by analog circuits.
[0049]
【The invention's effect】
As is apparent from the above, the present invention is a flat speaker composed of a microphone that detects sound waves in the sound field, a piezoelectric element that sends sound waves into the sound field, and an output signal from the microphone that is amplified and sent from the speaker. A monopole sound source integrated with a control circuit that has a control loop characteristic that generates a noise control signal that causes the sound wave to interfere in the sound field provides a very simple system and low-cost air conditioner noise control device. There is an effect that is.
[0050]
In addition, the monopole sound source can be made thinner by using a flat speaker composed of piezo elements or a thin speaker composed of a sandwich-type magnetic circuit to make the monopole sound source thinner. This has the effect of increasing the degree of freedom in designing the arrangement of the monopole sound source.
[0051]
In addition, the degree of freedom in designing the arrangement of the monopole sound source in the air conditioner has increased, making it possible to place the monopole sound source in the vicinity of the noise source of the air conditioner, and the noise emitted from the noise source. Is also silenced at the noise control boundary formed by a plurality of monopole sound sources, and the effect of suppressing the noise propagating from the air conditioner to the three-dimensional space can be achieved.
[0052]
In addition, the present invention makes it possible to control broadband noise of the monopole sound source, and to control noise that spreads broadly like an air conditioner.
[0053]
In addition, the present invention forms a noise control boundary by arranging a monopole sound source so as to surround the air outlet of the air conditioner. There is an effect that noise from the mouth can be controlled.
[0054]
Further, the present invention provides a noise control for each group of monopole sound sources in the longitudinal direction of the crossflow fan so as to sandwich the flow blown out from the crossflow fan through each group of monopole sound sources configured for each noise control frequency band. They are arranged at intervals shorter than a quarter wavelength of the sound corresponding to the upper limit value of the frequency band. Alternatively, a plurality of monopole sound source groups for each noise control band are sequentially ordered from the monopole sound source group having a high upper limit value of the noise control frequency band so as to surround the air outlet of the air conditioner, so that the noise of each monopole sound source group Even if the monopole sound source has only a narrow noise control band, it is arranged at intervals shorter than ¼ wavelength of the sound corresponding to the upper limit value of the control frequency band. It is possible to form a noise control boundary having a wider noise control frequency band depending on the group, and it is also possible to control a broad noise like an air conditioner.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a noise control device for an air conditioner according to Embodiment 1 of the present invention. FIG. 2 is a plan view showing the noise control device for an air conditioner according to Embodiment 2 of the present invention. FIG. 4 is a schematic diagram for explaining the operation of the air conditioner noise control apparatus according to the second embodiment of the present invention. FIG. 4 is a plan view showing the air conditioner noise control apparatus according to the fourth embodiment of the present invention. Fig. 6 is a schematic diagram showing the structure of a monopole sound source using loudspeakers with elements. Fig. 6 is a graph showing the amount of noise reduction in theoretical active noise control when phase error and amplitude error are used as parameters. FIG. 8 is a schematic diagram showing the result of analyzing the flow velocity simulation of the machine. FIG. 8 is a schematic diagram for verifying the noise reduction effect of the noise control device for the air conditioner according to the first embodiment of the present invention. Air conditioner noise FIG. 10 is a cross-sectional view showing a configuration of a conventional noise control device for an air conditioner. FIG. 11 is a block diagram showing a control mechanism of the noise control device for a conventional air conditioner. Fig. 12 is a block diagram showing a control mechanism in a conventional noise control device for an air conditioner. Fig. 13 is a block diagram showing a conventional active silencer. Fig. 14 is a diagram of a monopole sound source using a speaker constituted by a sandwich magnetic circuit. FIG. 15 is a schematic view showing a noise control device for an air conditioner according to Embodiment 3 of the present invention.
DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Cross flow fan 3 Monopole sound source 4 Flow to blow out 8 Piezo element 15 Outlet

Claims (6)

A microphone that detects sound waves in the sound field, a speaker that sends sound waves into the sound field, and a control loop characteristic that amplifies the output signal of the microphone and generates a noise control signal that causes the sound waves sent from the speaker to interfere in the sound field. The monopole sound source integrated with the control circuit having the upper limit value of the noise control frequency band of the monopole sound source so as to sandwich the flow blown from the cross flow blower in the longitudinal direction of the air conditioner A noise control device for an air conditioner, characterized in that a plurality of them are arranged at intervals shorter than a quarter wavelength of the sound corresponding to. A microphone that detects sound waves in the sound field, a speaker that sends sound waves into the sound field, and a control loop characteristic that amplifies the output signal of the microphone and generates a noise control signal that causes the sound waves sent from the speaker to interfere in the sound field. A monopole sound source integrated with a control circuit having an air conditioner so as to surround the outlet of the air conditioner at an interval shorter than a quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of the monopole sound source, A noise control device for an air conditioner, characterized in that a plurality of air conditioners are arranged. The longitudinal direction of the cross flow blower of the air conditioner so as to sandwich the flow blown out from each cross flow blower of each group of monopole sound sources by noise control frequency band composed of a plurality of monopole sound sources configured for each noise control frequency band The noise control apparatus for an air conditioner according to claim 1, wherein the noise control apparatus is arranged at intervals shorter than a quarter wavelength of a sound corresponding to an upper limit value of a noise control frequency band of each group of monopole sound sources. The quarter wavelength of the sound corresponding to the upper limit value of the noise control frequency band of each group of monopole sound sources so as to surround the outlet of the air conditioner sequentially from the monopole sound source group having a higher upper limit value of the noise control frequency band The noise control device for an air conditioner according to claim 2, wherein the noise control device is arranged at shorter intervals. 5. A noise control apparatus for an air conditioner according to claim 1, wherein the monopole sound source is a flat speaker composed of a piezo element for transmitting a sound wave into the sound field. 5. A noise control apparatus for an air conditioner according to claim 1, wherein a speaker for transmitting a sound wave in a sound field is constituted by a sandwich type magnetic circuit in a monopole sound source.

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