JPH0525500U - Active noise control device - Google Patents

Abstract

(57) Abstract: Objective and acoustic wavefront noise, is matched with the wave front of the sound waves emitted from the speaker, the Mute over the entire range. [Structure] The duct 1, which is a noise propagation path, is cut in the middle, and after passing through a hollow interference chamber 7 having a different diameter, the duct is restored to a desired shape. A first microphone 2 is arranged inside the duct 1 before being cut off, and a second microphone 3 for noise reduction evaluation is arranged downstream of the interference chamber 7. In addition, the diaphragm 4a, the top plate 4b, and the opening 1 in which the duct 1 is cut off so that they directly pass through the central axis of the radiating speaker.
Ring magnet 4c, bottom yoke 4d, voice coil 4
e, the spider 4f are arranged, and the control device 5 is provided in the peripheral portion of the duct 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is provided with a speaker for radiating a sound wave having a sound pressure of the same phase as that of the sound wave in a duct propagating the sound wave and having a phase opposite to that of the sound wave, and for muting the sound wave by the mutual interference between the sound wave and the noise. Active noise control device.

[0002]

[Prior Art]

 FIG. 4 is a principle diagram of a conventional active noise control device for a pipeline disclosed in, for example, Japanese Utility Model Laid-Open No. 2-83599. In the figure, 1 is an air-conditioning duct that serves as a sound wave propagation path. In this air-conditioning duct 1, a first microphone 2 and a second microphone 3 for noise reduction evaluation are arranged downstream thereof. There is. Further, a silence speaker 4 is installed between the first microphone 2 and the second microphone 3, and a control device 5 is installed between the silence speaker 4 and the second microphone 3. There is. Reference numeral 6 is a speaker cabinet for the silence speaker 4.

The conventional active noise control device is configured as described above, and the propagating sound wave from the noise source is detected by the first microphone 2, converted into an electric signal and input to the control device 5. The signal detected by the second microphone 3 installed downstream of the first microphone 2 is also input to the control device 5 in the same manner. In the control device 5, at the installation position of the second microphone 3, a driving signal that causes the output of the second microphone to become zero due to the interference between the sound wave for noise elimination emitted from the noise reduction speaker 4 and the sound wave propagated from the noise source. Is generated and output to the muffling speaker 4 so that the sound wave emitted from the noise source can be eliminated at the installation position of the second microphone 3.

[0004]

[Problems to be solved by the device]

 In a conventional active noise control device, a speaker is attached to the side wall surface of the duct and radiates sound waves in a direction perpendicular to the air flow direction.Therefore, the sound wavefront of noise and the wavefront of sound wave radiated from the speaker are There was a problem that they could not be matched and could not be completely muted over the entire range.

The present invention has been made in order to solve such a problem, and by radiating a sound wave that coincides with the wavefront of noise, the active noise that can muffle the noise generated in the duct over the entire sound range. An object is to provide a control device.

[0006]

[Means for Solving the Problems]

 The active noise control device according to the present invention includes a first sound detecting means for detecting noise in a duct, and a direct sound generating means for radiating a sound wave whose phase is 180 degrees inverted with respect to the noise. -Type loudspeaker unit is penetrated through the central part, one end of the opening is connected to a duct, and the other end of the penetrating part is opened to a sound wave interference chamber provided in front of the sound-generating means. The second acoustic detection means detects a composite sound wave of the propagated sound wave and the sound wave emitted from the sound generation means, and a control device that controls the drive of the sound generation means so that the sound pressure of the composite sound wave becomes zero. ing.

[0007]

[Action]

 In the active noise control device according to the present invention, the waveform and level of noise are detected by the first acoustic detection means and converted into an electric signal, the phase of this electric signal is inverted by 180 degrees, and a sound wave that matches the noise waveform is generated. The sound is emitted by the sound generating means.

[0008]

【Example】

 Example 1. FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a duct having a circular cross-sectional shape which serves as a sound wave propagation path, and this duct 1 is cut off in the middle and then returned to a desired duct shape through a hollow interference chamber 7 having a different diameter. .. A first microphone 2 is provided inside the duct 1 before being cut off, and a second microphone 3 for silencing evaluation is arranged downstream of the interference chamber 7 and thereafter. Further, the diaphragm 4a, the top plate 4b, the ring magnet 4c, the bottom yoke 4d, the voice coil 4e, and the spider 4f, which are arranged so that the opening where the duct 1 is cut off penetrate the central axis of the direct emission type speaker, are There is. Further, a control device 5 is installed in the peripheral portion of the duct 1.

FIG. 2 is an exploded perspective view of a top plate 4b made of a magnetic material, a ring magnet 4c, and a bottom yoke made of a magnetic material, which constitute the magnetic circuit of the direct radiating speaker.

The direct emission type loudspeaker, which is a sound generating means, is driven by the same principle as the conventional one, and the description thereof is omitted here. In the active noise control device configured as described above, the waveform and level of noise is detected by the first microphone 2 and converted into an electric signal, and the phase of this electric signal is inverted by 180 degrees to match the noise waveform. The generated sound wave is generated in the control device 5 and is emitted from the vibrating plate 4a in a direction coinciding with the noise wave front, and the noise sound wave and the antiphase sound wave from the vibrating plate 4a interfere in the interference chamber 7 to eliminate or reduce the noise. It is a thing.

In the active noise control device according to the present invention, the material of the duct 1 to which the active noise control device is applied is made of a non-magnetic material or an extremely high magnetic flux so that the magnetic flux generated from the ring magnet 4c efficiently flows into the magnetic circuit. It must be made of a material with low magnetic permeability. Further, in order to suppress the resonance of the air in the interference chamber 7, it is desirable to make the cross-sectional area of the interference chamber 7 as close as possible to the cross-sectional area of Duct 1 and further reduce the volume of the interference chamber.

Example 2. FIG. 3 shows a ring shape by combining a plurality of fan-shaped magnets 4g and a fan-shaped magnetic material 4h instead of the ring magnet 4c of FIG. 2 shown in the first embodiment.

When the active noise control device according to the present invention is applied to a duct having a large diameter, if it is configured as in the second embodiment shown in FIG. 3, the amount of magnets used can be reduced and the manufacturing cost can be reduced. ..

[0014]

[Effect of the device]

 According to the present invention, it is possible to emit the anti-phase sound wave matched with the waveform of the noise sound wave in the direction coinciding with the noise wave front in the duct, so that it is possible to eliminate the noise over the entire sound range. ..

[Submission date] March 26, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

[Means for Solving the Problems]

The active noise control device according to the present invention includes a first sound detecting means for detecting noise in a duct, and a direct sound generating means for radiating a sound wave whose phase is 180 degrees inverted with respect to the noise. is passed through the central portion of the mold speaker units, connect one end of the opening in the duct, yet the acoustic generator having an open second end of the penetrating part to sound waves interfere chamber provided in front of the sound generation means, said Consists of a second acoustic detection means for detecting a composite sound wave of a sound wave propagating sound and a sound wave emitted from the sound generation means, and a control device for controlling the drive of the sound generation means so that the sound pressure of the composite sound wave becomes zero. Has been done.

[Brief description of drawings]

FIG. 1 is a sectional view showing an active noise control device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the magnetic circuit unit of FIG.

FIG. 3 is a perspective view showing an active noise control device according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional active noise control device.

[Explanation of symbols]

 1 Air Conditioning Duct 2 First Microphone 3 Second Microphone 4 Silence Speaker 4a Vibration Plate 4b Top Plate 4c Ring Magnet 4d Bottom Yoke 4e Voice Coil 4f Spider 4g Magnet 4h Magnetic Material 5 Controller 6 Speaker Cabinet 7 Interference Chamber

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[Procedure amendment]

[Submission date] March 26, 1992

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Scope of utility model registration request] 1. A first acoustic detecting means provided for detecting a propagating sound wave from a noise source generated in a duct which is a propagating path of the sound wave, and a sound wave having a phase inverted by 180 degrees with respect to the propagating sound wave. A second sound source that radiates sound and that suppresses the noise that is the propagating sound wave by the sound wave interference thereof and a synthetic sound wave of the sound wave propagating from the noise source and the sound wave that is radiated from the sound generating means. In the active noise control device including the sound detection means and the control device that controls the drive of the sound generation means so that the sound pressure of the synthetic sound wave detected by the second sound detection means becomes zero, The central portion of the direct radiating speaker unit, which is the means, is penetrated, one end of the opening is connected to the duct, and the other end of the penetrating portion of the sound generating means is a sound wave interference chamber provided in front of the sound generating means. Open An active noise control device characterized in that 2. A ring-shaped magnet formed by combining a plurality of fan-shaped magnets and a fan-shaped magnetic material is used in place of the ring magnet constituting the magnetic circuit of the direct-radiation type speaker unit. The active noise control device according to claim 1.