JPH09198054A - Noise cancel device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a noise radiated by equipment in operation environment while securing horizontally wide directivity at the periphery of the auditory organ position of an operator who operates the equipment. SOLUTION: According to a noise signal r(n) detected by a microphone 5 which detects a noise generated by a noise source 10 in an equipment main body 9 and a sound collection signal e(n) detected by a microphone 8 which detects a composite noise radiated outside from the equipment main body 9 in the operation environment area of the equipment main body by the noise source 10 and an eccentric audio mirror speaker 3, an LMS(Least Mean Square) computing element 7 and an adaptive infinite impulse response(FIR) filter 4 generates a noise cancel sound signal which is equal in amplitude to and out of phase with the noise generated by the noise source 10 so that the noise signal r(n) becomes minimum, thereby performing the reproduction of the eccentric audio mirror speaker 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise canceling device that reduces noise radiated by driving a predetermined device by active noise control.

[0002]

2. Description of the Related Art FIG. 6 is a schematic block diagram for explaining the structure of a conventional noise canceling device, which corresponds to the case where the device is used for noise reduction of a device body 9.

In FIG. 6, reference numeral 18 denotes a general loudspeaker, which is an adaptive finite impulse response filter (FIR).
A (Finite Impulse Response) filter 4 (hereinafter referred to as an adaptive FIR filter) reproduces the noise canceling sound based on the signal processed to have the same amplitude and opposite phase as the noise.

Reference numeral 5 denotes a microphone. The noise source 10 collects the generated noise, and the collected noise signal x (n) is FIR.
Output to the filter 6. 7 is LMS (Least Mean Squar
e) A sound collection signal e (n) in the noise reduction area (noise reduction area) 11 collected by the microphone 8 and a noise signal r output from the FIR filter 6 by the computing unit (hereinafter referred to as LMS computing unit) Based on (n), the coefficient of the adaptive FIR filter 4 is calculated so that the sound collection signal (noise signal) e (n) is minimized, and the coefficient w of the adaptive FIR filter 4 is calculated.
Update (n + 1).

The operation of the noise canceling device constructed as above will be described below.

The noise signal detected by the microphone 5 is
It is input to the adaptive FIR filter 4 and the FIR filter 6. The signal processed by the adaptive FIR filter 4 so as to have the same amplitude and opposite phase as the noise is the loudspeaker 18
Reproduced by. Then, the reproduced sound and the noise from the noise source interfere with each other, and the interference sound is detected by the microphone 8 and input to the LMS calculator 7.

On the other hand, the noise signal processed by the FIR filter 6 is also input to the LMS calculator 7.

Here, the transfer function from the loudspeaker 18 to the microphone 8 is preset in the FIR filter 6. Therefore, the LMS calculator 7 calculates the noise signal e from the two noise signals r (n) and e (n) shown in FIG.
The coefficient of the adaptive FIR filter 4 is calculated so that (n) becomes the minimum, and the coefficient w (n + of the adaptive FIR filter 4 is calculated.
Update 1).

As a result, the noise signal is adaptively controlled by the adaptive FIR filter 4 and reproduced from the loudspeaker 18 as a noise cancellation signal having the same amplitude and opposite phase as the noise, thereby reducing the error signal in the microphone 8. Noise is reduced in the noise reduction area 11 (Japanese Patent Laid-Open No. 5-2
16485 publication).

[0010]

However, in the above-mentioned conventional example, regarding the performance of the loudspeaker 18 to be used, when the noise canceling device is applied to equipment used indoors, the head of a human being to be actually silenced. No consideration was given to the horizontal directivity in the space including the periphery.

FIG. 7 is a characteristic diagram showing the horizontal directivity of the loudspeaker 18 installed in the noise canceling device shown in FIG. 6. For example, the frequency range of the audio output signal is 1 KH.
Corresponding to horizontal directivity in the case of z to 8 KHz, it was presented by "Kami Shin and Ichiro Fukai" as "Horizontal directivity of computer simulation eccentric audio mirror speaker" at the 1980 Hokkaido Branch Joint Conference of the Electrical Association. It is based on.

The loudspeaker 18 shown in FIG.
Since it has a general horizontal directivity as shown in (3), the noise reduction area of the noise canceller has been limited. As a particularly general tendency, as shown in FIG. 7, since the directivity of the loudspeaker 18 becomes narrower as the frequency becomes higher, the frequency band to which the active noise control can be applied is also limited to the low range. There was a problem that it would end up. In FIG. 7, X,
Y and Z indicate a rectangular coordinate system, and φ is 90 degrees.

The present invention has been made to solve the above-mentioned problems, and the first to third inventions of the present invention have the objective of canceling noise generated by driving of the equipment body. By adopting an eccentric audio mirror speaker as a reproduction speaker for reproducing the sound, it is possible to maintain a wide directivity in the horizontal direction around the auditory organ position of the operator who operates the device, while keeping the external direction from the device in the operating environment area. An object of the present invention is to provide a noise canceling device that can mitigate radiated noise.

[0014]

A first invention according to the present invention is directed to a first detecting means for detecting noise generated from a noise source in an equipment body and a noise detecting means for detecting noise generated from the noise source. A reproduction speaker for reproducing a noise-canceling audio signal having an amplitude and an opposite phase, and a second detection for detecting a combined noise externally radiated from the device body by the noise source and the reproduction speaker in an operating environment area of the device body. Means for minimizing the first detection value based on the first detection value detected by the first detection means and the second detection value detected by the second detection means. And a control means for controlling the frequency characteristic of the noise canceling audio signal reproduced from the reproducing speaker.

According to a second aspect of the present invention, there is provided a first detecting means for detecting noise generated from a noise source in the equipment body,
A plurality of reproduction speakers that reproduce noise canceling audio signals having the same amplitude and opposite phase with respect to the noise generated from the noise source, and synthetic noise externally radiated from the device body by the noise source and the reproduction speaker. A plurality of second detection means detected in the operating environment region of the device body, a first detection value detected by the first detection means, and a second detection value detected by the second detection means. And a plurality of control means for controlling the frequency characteristic of the noise canceling audio signal reproduced from each reproduction speaker so that the first detection value is minimized.

In a third aspect of the present invention, the reproduction speaker is an eccentric audio mirror speaker.

[0017]

In the first aspect of the invention, the device body is constituted by the first detection value detected by the first detecting means for detecting the noise generated from the noise source in the device body, the noise source and the reproduction speaker. The control unit minimizes the first detection value based on the second detection value detected by the second detection unit that detects the synthetic noise radiated from the outside in the operation environment region of the device body. In addition, a noise canceling audio signal having the same amplitude and opposite phase to the noise generated from the noise source is generated to reproduce the reproduction speaker, and even if the noise is radiated from the noise source inside the device to the outside of the device. It is possible to mute sound in the operating environment area of.

In the second aspect of the invention, the device body is constituted by the first detection value detected by the first detecting means for detecting the noise generated from the noise source in the device body, the noise source and the reproduction speakers. Based on the respective second detection values detected by the plurality of second detection means for detecting the synthetic noise radiated from the outside in the operation environment region of the device body, each control means has the smallest first detection value. As described above, noise canceling audio signals having the same amplitude and opposite phase with respect to the noise generated from the noise source are generated to reproduce the respective reproduction speakers, and the noise is radiated from the noise source inside the device. However, it is possible to mute a wide area in the operating environment area outside the equipment.

According to the third aspect of the invention, the eccentric audio mirror speaker having a wide directivity with respect to the horizontal direction can muffle the noise in the operating environment outside the device even if the noise is radiated from the noise source inside the device.

[0020]

【Example】

[First Embodiment] FIG. 1 is a block diagram for explaining the arrangement of a noise canceling device according to the first embodiment of the present invention.

In FIG. 1, reference numeral 3 denotes an eccentric audio mirror speaker, which is composed of a cone portion 1 and an audio mirror 2, and is converted into a signal processed by an adaptive FIR filter 4 so as to have the same amplitude and opposite phase as noise. Based on this, the noise canceling sound is reproduced. The eccentric audio mirror speaker 3 has a directivity with respect to the horizontal direction of an output device that generates a noise canceling signal in a space including the vicinity of a human head, which is important when applying the noise canceling device to equipment used indoors. Can be widely secured.

A microphone 5 collects the noise generated by the noise source 10, and the collected noise signal x (n) is FIR.
Output to the filter 6. An LMS calculator 7 collects sound based on a sound collection signal e (n) of a noise reduction area (noise reduction area) 11 collected by the microphone 8 and a noise signal r (n) output from the FIR filter 6. Sound signal e
The coefficient of the adaptive FIR filter 4 is calculated so that (n) becomes the minimum, and the coefficient w (n + of the adaptive FIR filter 4 is calculated.
Update 1). A transfer function from the eccentric audio mirror speaker 3 to the microphone 8 is preset in the FIR filter 6.

Correspondence between the present embodiment and each means of the first invention and its operation will be described below with reference to FIG.

The first aspect of the present invention is to detect the noise generated from the noise source 10 in the device body (copier in this embodiment) 9 by the first detecting means (microphone 5) and the noise source 10. A reproduction speaker (eccentric audio mirror speaker 3) for reproducing a noise-canceling audio signal having the same amplitude and opposite phase with respect to noise, and a device for producing synthetic noise radiated from the device body by the noise source and the reproduction speaker. From the second detection means (microphone 8) for detecting in the operation environment area of the main body, the first detection value (noise signal r (n)) detected by the first detection means, and the second detection means Based on the detected second detection value (sound collection signal e (n)), the frequency characteristic of the noise canceling audio signal reproduced from the reproduction speaker is controlled so that the first detection value is minimized. Control means An eccentricity with the noise signal r (n) detected by the microphone 5 having the LMS calculator 7 and the adaptive FIR filter 4) and detecting the noise generated from the noise source 10 in the device body 9 and the noise source 10. The audio mirror speaker 3 and the sound collecting signal e (n) detected by the microphone 8 that detects the combined noise radiated from the device body 9 in the operating environment region of the device body based on the LM.
The S calculator 7 and the adaptive FIR filter 4 make the noise signal r
In order to minimize (n), a noise canceling audio signal having the same amplitude and opposite phase with respect to the noise generated from the noise source 10 is generated and the eccentric audio mirror speaker 3 is reproduced to generate noise in the device. Even if noise is radiated from the source, it is possible to mute the noise in the operating environment area outside the equipment.

The operation of the noise canceling device constructed as above will be described below.

Noise signal x detected by the microphone 5
(N) is the adaptive FIR filter 4 and the FIR filter 6
Is input to The signal processed by the adaptive FIR filter 4 to have the same amplitude and opposite phase as the noise is reproduced by the eccentric audio mirror speaker 3. And
The reproduced sound and the noise from the noise source 10 interfere with each other, and the interference sound is detected by the microphone 8 and input to the LMS calculator 7.

On the other hand, the noise signal r (n) processed by the FIR filter 6 is also input to the LMS calculator 7. Here, the transfer function from the eccentric audio mirror speaker 3 to the microphone 8 is preset in the FIR filter 6. Therefore, the LMS calculator 7 determines the coefficient of the adaptive FIR filter 4 from the two noise signals r (n) and e (n) shown in FIG. 1 so as to minimize the noise signal e (n). The coefficient of the adaptive FIR filter 4 is calculated and updated.

As a result, the noise signal is adaptively controlled by the adaptive FIR filter 4 and reproduced from the eccentric audio mirror speaker 3 as a noise canceling signal having the same amplitude and opposite phase as the noise, thereby reducing the error signal in the microphone 8. The noise is reduced in the noise reduction area 11.

Hereinafter, various characteristics of the eccentric audio mirror speaker 3 shown in FIG. 1, which is adopted as the speaker of the noise canceling device according to the present invention, will be described.

FIG. 2 is a schematic diagram for explaining a propagation state of a noise cancel signal reproduced from the eccentric audio mirror speaker 3 shown in FIG. 1. FIG. 3 shows the eccentric audio mirror speaker 3 shown in FIG. It is a characteristic view explaining the directivity in the horizontal direction, which corresponds to the horizontal directivity in the case where the frequency range of the audio output signal is 1 KHz to 8 KHz, for example, in the 1980 Hokkaido Section Union Conference of the Electrical Relations Society 180,
It is based on what was published by Shin Kagami and Ichiro Fukai as "Horizontal directivity of computer simulation eccentric audio mirror speaker". In FIGS. 2 and 3, the same components as those in FIG. 1 are designated by the same reference numerals, and 19 is a casing surface that constitutes a casing in the device. Further, in the figure, X, Y, and Z indicate a rectangular coordinate system, and φ is 90 degrees.

As shown in this figure, in the eccentric audio mirror speaker 3, the degree of narrowing of directivity due to an increase in frequency is small, and when compared at the same frequency, the horizontal directivity (horizontal direction X) is always wider than that of the loudspeaker. Is allowed to have. This means that at the same frequency, the sound waves having the same amplitude are distributed in a wider range than the horizontal direction when the eccentric audio mirror speaker 3 is used, and therefore, noise in the same frequency band is targeted for reduction. In this case, the noise low frequency region is expanded in the horizontal direction as compared with the case where the noise cancel signal is output from the general loudspeaker 18. This corresponds to the position Y of the human head when the device is used indoors,
The effect of applying the noise canceling device will be enhanced.

Further, even if the upper limit of the frequency band of the sound wave generated from the noise source 10 becomes high, it can be applied as a noise canceling device.

Also, the eccentric audio mirror speaker 3
As shown in FIG. 2, since the central axis Z of the cone portion 1 and the central axis of the audio mirror 2 are eccentric, the noise canceling signal to the rear surface of the speaker (corresponding to the housing surface 19) as shown in FIG. Is reduced, and the influence of the reflected wave from the housing surface 19 from the device body on the silencing region is also avoided.

[Second Embodiment] In the first embodiment, the case where the noise generated from the noise source 10 is canceled by one eccentric audio mirror speaker 3 has been described. However, a plurality of eccentric audio mirror speakers are used as noise sources. The noise canceling effect may be enhanced by arranging them at the sandwiched positions. Hereinafter, the embodiment will be described.

FIG. 5 is a block diagram for explaining the configuration of the noise canceling apparatus showing the second embodiment of the present invention, and corresponds to the state in which the inside of the equipment to be adapted is visualized.

In the figure, reference numeral 12 is an eccentric audio mirror speaker, which is composed of a cone portion 1 and an audio mirror 2, and is based on a signal processed by an adaptive FIR filter 13 so as to have the same amplitude and opposite phase as noise. The noise canceling sound is played.

The microphone 5 collects the noise generated from the noise source 10 and outputs the collected noise signal x (n) to the FIR filters 6 and 14. Reference numeral 15 denotes an LMS calculator that collects sound based on a sound collection signal e (n) of the noise reduction area (noise reduction area) 11 collected by the microphone 16 and a noise signal r (n) output from the FIR filter 14. The coefficient of the adaptive FIR filter 13 is calculated so that the sound signal e (n) becomes the minimum, and the adaptive FIR filter 13 is calculated.
Update coefficient of. A transfer function from the eccentric audio mirror speaker 12 to the microphone 16 is preset in the FIR filter 14.

Correspondence between the present embodiment and each means of the second invention and its operation will be described below with reference to FIG.

The second aspect of the present invention is to detect the noise generated from the noise source 10 in the device body (copier in this embodiment) 9 by the first detecting means (microphone 5) and the noise source 10. A plurality of reproducing speakers (eccentric audio mirror speakers 3 and 12) for reproducing noise canceling audio signals having the same amplitude and opposite phase with respect to noise, and the noise source and the reproducing speaker are externally radiated from the device body. A plurality of second detection means (microphones 8 and 16) for detecting the synthetic noise in the operation environment region of the device body, and a first detection value (noise signal r (n)) detected by the first detection means. And the second detection value (sound collection signal e (n)) respectively detected by the second detection means, the first detection value is reproduced from each reproduction speaker so as to be the minimum. The noise phase A plurality of control means for controlling the frequency characteristic of the audio signal (LMS arithmetic unit 7 and 15, the adaptive FIR filter 4, 13) and has a noise source 10 in the apparatus main body 9
The noise signal r (n) detected from the microphone 5 for detecting the noise generated from the device main body 9 is generated by the noise source 10 and the eccentric audio mirror speakers 3 and 12. The LMS calculators 7 and 15 and the adaptive F based on the respective sound collection signals e (n) detected from the microphones 8 and 16 detected in the operation environment region
The eccentric audio mirror speaker 3 generates noise canceling audio signals having the same amplitude and opposite phase with respect to the noise generated from the noise source 10 so that the IR filters 4 and 13 minimize the noise signal r (n). , 12 can be muted over a wide area in the operating environment area outside the device even if the noise is radiated from the noise source inside the device.

The operation of the noise canceling device constructed as above will be described below.

The noise signal detected by the microphone 5 is
It is input to the plurality of adaptive FIR filters 4 and 13 and the plurality of FIR filters 6 and 14. The signals processed by the adaptive FIR filters 4 and 13 to have the same amplitude and opposite phase to the noise are reproduced by the eccentric audio mirror speakers 3 and 12, respectively. Then, the reproduced sound and the noise from the noise source 10 interfere with each other, and the interference sound is detected by the respective microphones 8 and 16, and the LMS calculators 7 and 1 are detected.
5 is input.

On the other hand, the noise signal r (n) signal-processed by the FIR filters 6 and 14 is also supplied to the LMS calculators 7 and 1, respectively.
5 is input. Here, transfer functions from the eccentric audio mirror speakers 3 and 12 to the microphones 8 and 16 are preset in the FIR filters 6 and 14. Therefore, the LMS calculators 7 and 15 calculate the noise signal e (n) from the two signals r (n) and e (n) shown in FIG.
The coefficients of the adaptive FIR filters 4 and 13 are calculated so as to minimize, and the coefficients of the adaptive FIR filters 4 and 13 are updated. As a result, each noise signal is adaptive FI.
By being adaptively controlled by the R filters 4 and 13 and reproduced from the eccentric audio mirror speakers 3 and 12 as a noise canceling signal having the same amplitude and opposite phase as the noise, the error signal in the microphones 8 and 16 is reduced and the noise reduction region is reduced. Noise is reduced (cancelled) at 11 and 17.

Here, as shown in the first embodiment, the noise canceling device using the eccentric audio mirror speaker 3 produces more noise in the same frequency band than the noise canceling device using the general loudspeaker 18. When applied, the noise reduction area is expanded.

Therefore, when a plurality of eccentric audio mirror speakers 3 are used in the second embodiment, the noise reduction area of each speaker is wider than that of the general loudspeaker 18, so that the entire apparatus is The noise reduction area of is naturally expanded as compared with the case where the same general loudspeaker is used.

As a result, similarly to the first embodiment, when a plurality of eccentric audio mirror speakers 3 are used,
The upper limit of the frequency band of noise to which the noise canceller can be applied can be further increased.

Further, similarly to the first embodiment, the eccentric audio mirror speaker 3 has the cone portion 1 as shown in FIG.
Since the central axis Z of the eccentricity and the central axis of the audio mirror 2 are eccentric, as shown in FIG. 4, the wraparound of the noise canceling signal to the back surface (housing surface 19) of the eccentric audio mirror speaker 3 is reduced, and the device As described above, the influence of the reflected wave from the main body 9 on the silencing area is avoided.

In each of the above embodiments, the device to which the present invention is applied is not disclosed, but the device is not particularly limited as long as it has a noise source adaptable to the frequency characteristics of the eccentric audio mirror speaker 3. .

Correspondence between the first and second embodiments and each means of the third invention and their functions will be described below.

The third invention adopts the eccentric audio mirror speaker 3 or the eccentric audio mirror speakers 3 and 12 as the reproduction speaker, and the eccentric audio mirror speaker 3 having a wide directivity in the horizontal direction is the noise source 10 in the device. Even if noise is emitted from the outside, it is possible to mute the noise in the operating environment area outside the equipment.

[0050]

As described above, the first embodiment according to the present invention is described.
According to the invention, the first detection value detected by the first detection means for detecting the noise generated from the noise source in the device body, the noise source and the reproduction speaker are externally radiated from the device body. The noise so that the control means minimizes the first detection value based on the second detection value detected by the second detection means detecting the combined noise in the operation environment region of the device body. Since a noise canceling audio signal having the same amplitude and opposite phase to the noise generated from the source is generated and reproduced by the reproducing speaker, even if the noise is radiated from the noise source inside the equipment, the operating environment area outside the equipment Can be muted at.

According to the second invention, the device is constituted by the first detection value detected by the first detecting means for detecting the noise generated from the noise source in the main body of the device, the noise source and the reproduction speakers. Based on the respective second detection values detected by the plurality of second detection means for detecting the synthetic noise radiated from the main body in the operating environment area of the device body, each control means determines that the first detection value is Since noise canceling audio signals having the same amplitude and opposite phase to the noise generated from the noise source are generated and reproduced by the respective reproduction speakers so that the noise is minimized, the noise is radiated from the noise source inside the device to the outside. Even if it is done, it is possible to mute in a wide area in the operating environment area outside the device.

According to the third aspect of the invention, the eccentric audio mirror speaker having a wide directivity in the horizontal direction allows the operating environment area outside the device, particularly the auditory organs of the device operator, to be emitted even if noise is radiated from the noise source inside the device. It can mute in the high operating environment of.

Therefore, in the vicinity of the position of the auditory organ of the operator who operates the device, it is possible to suppress the noise radiated from the device externally in the operation environment region while ensuring a wide directivity in the horizontal direction.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a noise canceling device according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a propagation state of a noise cancel signal reproduced from the eccentric audio mirror speaker shown in FIG.

FIG. 3 is a characteristic diagram for explaining horizontal directivity of the eccentric audio mirror speaker shown in FIG.

FIG. 4 is a characteristic diagram illustrating a propagation state of reflected waves of the coaxial audio mirror speaker illustrated in FIG.

FIG. 5 is a block diagram illustrating a configuration of a noise canceling device showing a second embodiment of the present invention.

FIG. 6 is a schematic block diagram illustrating the configuration of a conventional noise canceling device.

7 is a characteristic diagram showing horizontal directivity of a loudspeaker installed in the noise canceling device shown in FIG.

[Explanation of symbols]

 3 Eccentric audio mirror speaker 4 Adaptive FIR filter 5 Microphone 6 FIR filter 7 LMS calculator 8 Microphone 9 Device body 10 Noise source 11 Noise reduction area

Claims (3)

[Claims] 1. A first detection means for detecting noise generated from a noise source in a device body, and a reproduction for reproducing a noise canceling audio signal having the same amplitude and opposite phase to the noise generated from the noise source. A loudspeaker, a second detection means for detecting a synthetic noise externally radiated from the equipment body by the noise source and the reproduction speaker in an operation environment region of the equipment body, and a second detection means detected by the first detection means. 1 detection value and the second
Control means for controlling the frequency characteristic of the noise canceling audio signal reproduced from the reproduction speaker so that the first detection value is minimized based on the second detection value detected by the detection means. A noise canceling device having. 2. A plurality of first detecting means for detecting noise generated from a noise source in the device body, and a plurality of reproducing noise canceling audio signals having the same amplitude and opposite phase to the noise generated from the noise source. From the first detection means, a plurality of second detection means for detecting combined noise externally radiated from the equipment main body by the noise source and the reproduction speaker in an operation environment region of the equipment main body, Based on the detected first detection value and the respective second detection values detected by the second detection means, the noise reproduced from each reproduction speaker so that the first detection value becomes the minimum. A noise canceling device comprising: a plurality of control means for controlling the frequency characteristic of a canceling audio signal. 3. The noise canceling device according to claim 1, wherein the reproduction speaker is an eccentric audio mirror speaker.