JPH10149172A - Private power generating device with active sound eliminating device, and transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the active sound eliminating device which can reduce the whole noise radiated by equipment, etc., placed in a three-dimensional space under automatic control in simple constitution. SOLUTION: This device is equipped with an additional sound source (speaker) 32 arranged nearby a noise source 31, acoustic power measuring means (microphones 33 and 34) which measure the acoustic power from the additional sound source 32 due to interference between the noise source 31 and additional sound source 32, and a control means 35 which controls the output of the additional sound source 32 so as to minimize the acoustic power measured by the means. Consequently, control for minimizing the acoustic power radiated by the additional sound source is performed, and consequently the total acoustic power of the noise source and additional sound source becomes minimum. Consequently, the noise radiated by the noise source to the circumference is effectively reduced, which greatly contributes greatly to sound elimination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active silencer for reducing noise radiated from a noise source, a private power generator provided with the active silencer, and a transformer.

[0002]

2. Description of the Related Art As is well known, in an active noise reduction system, an additional sound source is newly provided in order to reduce noise radiated from a noise source, and the additional sound radiated from the additional sound source is combined with the noise. The noise is canceled by the sound interference effect. In such an active silencer, a method is often used in which a combined sound of noise and an additional sound is measured by a microphone, and the additional sound source is controlled so that the sound pressure becomes zero or minimum.

In a conventional active silencer for a system in which sound propagates one-dimensionally, such as an air-conditioning duct, noise radiated from a noise source is prevented from leaking outside from an opening of the air-conditioning duct. Therefore, a reference microphone for obtaining a signal of noise propagating in the air conditioning duct is arranged on the noise source side, and an evaluation microphone for obtaining a signal of sound leaking from the opening to the outside is provided on the opening side. And a speaker as an additional sound source for radiating additional sound into the air conditioning duct is arranged at a position between both microphones.

A sound signal obtained by the evaluation microphone is a signal of a synthesized sound of a sound from a noise source and a sound from a speaker. The sound radiated from the speaker is controlled by the adaptive control device so that the synthesized sound approaches zero.

[0005] The adaptive control device constitutes a control system based on the Filtered-XLMS algorithm which is frequently used for active noise reduction control.
(Finite Impulse Response) filter and an adaptive FIR filter. That is, the output signal of the reference microphone is input to the FIR filter, and the adaptive FIR
The signal is input to the filter, and the output signal of the evaluation microphone is input to the adaptive FIR filter.

[0006] The FIR filter outputs the product sum of the input signal and its filter coefficient. When the sum of the output of the filter and the external signal is used as an error signal, the adaptive FIR filter automatically updates the filter coefficient so that the error signal approaches zero. Here, the signal from the evaluation microphone becomes an error signal. Filtered
In the -XLMS algorithm, the filter coefficient of the FIR filter is set to be the same as the filter coefficient of the adaptive FIR filter.

Generally, in an adaptive FIR filter,
The following calculation is performed each time a sampling input is given.

[0008]

(Equation 1)

Note that in equations (1) to (3), e (n)
Is the error signal at time n, d (n) and y (n) are the external signal and the output signal of the filter, respectively, and h (k) is the filter coefficient. new and old represent after and before updating of the filter coefficient, respectively. Further, x (n−k + 1) is an input signal, and μ is a constant called a step size parameter that determines the speed of convergence. Equation (2) representing the update of the filter coefficient is obtained from the following equation (4) of the steepest descent method.

[0010]

(Equation 2)

In such an active silencer, a control additional sound is radiated from the speaker based on the sound detected by the reference microphone, and the additional sound interferes with the noise transmitted through the air conditioning duct from the noise source. Let it. Then, while evaluating the degree of interference using the evaluation microphone, the sound pressure at the position of the evaluation microphone is approached to zero. When a zero sound pressure point is created, sound is reflected at that point due to differences in acoustic impedance. Therefore, the light does not propagate in the direction of the opening, and noise radiated from the opening can be eliminated.

However, such an active silencer is effective for a system in which noise propagates one-dimensionally, such as an air conditioning duct, but cannot be applied to noise that propagates three-dimensionally. This is because in the case of one-dimensional propagation, it is possible to reflect all of the sound from the noise source and prevent the sound from leaking out of the exit by merely reducing the sound pressure at the opening, that is, the exit, to zero, but the three-dimensional propagation In this case, since noise is emitted from the noise source in all directions, even if the sound pressure is made zero at one control point, there is almost no effect.

On the other hand, in consideration of the three-dimensional spread of noise radiated from a noise source device, as a method of reducing the total noise radiated from the device, the device is surrounded by many additional sound sources, There has been proposed a method of radiating additional sound from a sound source to reduce sound leaking outside the surrounding surface. This is an extension of the above-described method using an air-conditioning duct in which sound propagates one-dimensionally to a three-dimensional space.

In the active noise reduction device for realizing this method, a plurality of additional sound sources are arranged on an equidistant surrounding surface around the noise source device, and an evaluation microphone is arranged near each of these additional sound sources. Is done. The output signal of each evaluation microphone is input to a control device that drives and controls each additional sound source. A signal correlated with the sound emitted from the device, for example, a vibration signal of a wall surface, is input to the control device via a signal line as a reference signal.

The control device controls each additional sound source such that the sound pressure at each evaluation microphone is minimized. In other words, the control device controls the amplitude and the phase of each corresponding additional sound source such that the sum of squares of the sound pressure at each evaluation microphone is minimized.

However, in the active silencer configured as described above, since additional sounds from a large number of additional sound sources are mixed into each evaluation microphone, a control system must be constructed in consideration of those effects. However, the control system including the control device is inevitably complicated. Furthermore, since it is necessary to set the interval between the additional sound sources to within 1/2 of the wavelength of the sound whose sound is to be reduced, if the surrounding surface is set relatively far from the noise source device, many There is also a problem that an additional sound source and an evaluation microphone are required.

Another method for reducing the overall noise radiated from the device in consideration of the three-dimensional spread of the noise radiated from the device as the noise source is to use a discrete point sound source as the device as the noise source. The intensity and phase of these point sound sources are determined in advance, and the intensity and phase of each additional sound source are controlled so that the overall sound power when the additional sound source is arranged around is minimized. A way is being considered. Here, the strength of the sound source is the volume velocity that springs out of the sound source,
Vibration velocity is integrated by its area. The sound power is energy per unit time radiated from a sound source.

In an active silencer that implements this method, an additional sound source that is driven and controlled by a control device is disposed on each wall of a device that is a noise source. Further, the control device is connected to a database in which discrete data sources are assumed to be present on the respective walls based on the previously measured vibrations of the respective walls, and data of the data is prepared in advance. The control device calculates the phase and sound intensity of each additional sound source that minimizes the overall sound power when the noise of the device that is the noise source and the additional sound of the additional sound source are added, and the calculation result Drive control of each additional sound source according to the following.

In the active silencer configured as described above,
It is necessary to obtain in advance the amplitude and phase of the intensity of each wall of the device, that is, each sound source. However, it is actually difficult to accurately determine the amplitude and phase of the intensity of each sound source. For this reason, application to general noise sources is difficult. Even if it can be obtained, if there is a change such as a change in the amplitude or phase of the sound source on the way, it is necessary to redo the setting, which is not easy to use. For these reasons, the device has not yet been put to practical use.

In the conventional active silencer described above, there is a problem that the whole noise radiated by the equipment or the like placed in the three-dimensional space cannot be effectively reduced with a simple configuration. Was.

[0021]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object a simple configuration and automatic control of equipment and the like placed in a three-dimensional space. An object of the present invention is to provide an active silencer capable of reducing the entire radiated noise.

[0022]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the object, the present invention is configured as follows.

A private power generator provided with an active silencer according to the present invention is a private power generator provided with an active silencer for suppressing noise from an engine for driving a generator. Sound power measuring means for measuring sound power from the sound source resulting from mutual interference between engine sound from the engine and sound from the sound source; and to minimize sound power measured by the measuring means. Control means for controlling the output from the sound source.

Further, a transformer provided with an active silencer according to the present invention is a transformer provided with an active silencer for suppressing noise from a tank containing an iron core, a coil, and insulating oil. A sound power measuring means for measuring sound power from the sound source resulting from mutual interference between the noise from the tank and the sound from the sound source; and a sound measured by the measuring means. Control means for controlling the output from the sound source so as to minimize the power.

An active noise reduction device according to the present invention is an active noise reduction device for suppressing noise generated from a noise source.
A sound source arranged in the vicinity of the noise source, sound power measuring means for measuring sound power from the sound source resulting from mutual interference between the noise source and the sound source, and sound power measured by the measuring means. Control means for controlling the output from the sound source so as to minimize it.

In the above-described active noise reduction device, control for minimizing the sound power radiated from the additional sound source is performed, and as a result, the total sound power of the noise source and the additional sound source is minimized. For this reason, the noise radiated from the noise source to the surroundings is effectively reduced, which greatly contributes to noise reduction.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) The first embodiment is an embodiment for explaining the basic concept of a sound deadening means provided in an active sound deadening device according to the present invention.

As one of the methods for reducing the sound power of the radiated sound from the noise source, a method of placing an additional sound source having the same amplitude and the opposite phase near the noise source is known. In this case, the sound emitted from the noise source and the sound emitted from the additional sound source interfere with each other, cancel each other, and as a result, the sound power radiated from the whole can be reduced.

Now, consider a simple model shown in FIG. In FIG. 1, reference numeral 22 denotes a noise source, and reference numeral 23 denotes an additional sound source, all of which emit sound having an angular frequency ω.
In case the sound and amplitude equal phase of the sound intensity noise source 22 of the additional sound source 23 is reverse-phase, the acoustic power in the case of only the noise source 22 and W _1, both when sounded additional sound source 23 Assuming that the sum of the acoustic power is W and the ratio is γ,
γ is represented by the following equation (7).

[0031]

(Equation 3)

D is the distance between the noise source 22 and the additional sound source 23. In this equation (7), when γ = 1, the additional sound source 2
3 indicates that the sound power after ringing 3 is equal to the sound power of the noise source 22 only.

However, according to this method, for example, when the distance d between the noise source 22 and the additional sound source 23 becomes close to half the wavelength of the sound, the total sound power becomes larger than the sound power of the noise source 22 alone. This is not a condition for minimizing sound power.

The condition for realizing the minimum acoustic power is that the radiated acoustic power of the additional sound source 23 is set to zero. This does not mean that the additional sound source 23 is stationary and does not emit sound, but the phase of the vibration speed of the additional sound source 23 and the sound pressure on its surface are shifted by 90 degrees, and the energy of the sound radiated from the sound source is Refers to the state where the energy of the sound flowing into the sound source is balanced and zero. When the sound power is the minimum, the ratio γ of the sound power between before and after the sound of the additional sound source 23 is given by the following equation (8). It cannot be greater than power.

[0035]

(Equation 4)

According to the present invention, the sound power of the additional sound source
W _Q , the sound power of the noise source alone is W _q (W ₁ above), the sound power of the additional sound source is W _qQ due to the mutual interference of sound between the noise source and the additional sound source, and the mutual interference of sound between the noise source and the additional sound source is the sound power of the noise source and W _Qq by, when the total acoustic power W is represented by the following _{equation, W = W Q + W qQ} + W Qq + W q ... (9) as shown in the following equation, additional sound source All acoustic power W in the case of acoustic power W _a is zero is defined by noting is minimized.

[0037] _{W a = W Q + W qQ} = 0 ... (10) obtains the sound power W _a of the additional sound source, the total sound power W by controlling the additional sound source so it becomes zero or minimum
Can be minimized.

By the way, the sound power of a sound source (noise source, additional sound source) is the energy of sound radiated from the sound source per unit time as described above, and this is the sound intensity radiated from the sound source. Is integrated over the entire surface surrounding the sound source. The sound intensity is the energy of sound passing through a unit area in a unit time.

In the present invention, the above-described sound intensity is measured as an evaluation amount of the sound power, and control is performed such that the measured sound intensity becomes zero or minimum. Speakers are usually used as additional sound sources, but since speakers can be regarded as point sound sources, when the sound intensity is measured at a position close to the speaker on almost the center axis of the vibration surface, an amount proportional to the sound power is obtained. Thus, data necessary for minimizing sound power can be obtained.

There are several methods for measuring the sound intensity of the sound radiated from the additional sound source, but the method called the two-microphone method is the simplest. The sound intensity is the time average of the product of the sound pressure and the particle velocity of the medium,
Particle velocity is proportional to the amount of sound pressure differentiated by distance. Sound pressure can be measured with a microphone, but particle velocity cannot be measured. The two-microphone method uses two closely placed microphones.
This is a method in which sound pressure is measured by each of the microphones, and the particle velocity is obtained based on the difference result.

As described above, by controlling the sound intensity of the additional sound source to be zero, the sound power of the additional sound source can be made zero, and the sound power of the noise source and the additional sound source as a whole can be reduced. Power can be reduced. According to this concept, for sound propagating from the noise source to the three-dimensional space, it is possible to realize a reduction in the noise around the noise source as a whole, instead of simply controlling the sound pressure at one point to zero.

As described above, the additional sound source is arranged near the noise source, and the sound power from the additional sound source (W _a = W _Q + W _qQ ) resulting from the mutual interference of the sound from the noise source and the additional sound source. According to the present invention, the output of the additional sound source is controlled so that the measured acoustic power is set to zero or minimum.
The overall sound power of the noise source and the additional sound source can be reduced. According to this concept, for sound propagating from the noise source to the three-dimensional space, it is possible to realize a reduction in the noise around the noise source as a whole, instead of simply controlling the sound pressure at one point to zero.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

FIG. 2 is a block diagram showing a schematic configuration of an active silencer according to a second embodiment of the present invention.

In the figure, reference numeral 31 denotes a target device such as a transformer arranged in a three-dimensional space, that is, a noise source. In the vicinity of the noise source 31, a speaker 32 as an additional sound source is arranged. 2 on the center axis of the vibration surface of the speaker 32
The microphones 33 and 34 are arranged at a predetermined interval from each other. The sound pressure signals measured by the microphones 33 and 34 are introduced to the control device 35.

The control device 35 includes the microphones 33,
An average sound pressure calculation unit 36 for calculating an average sound pressure between microphones from the sound pressure signal 34 and a particle velocity calculation unit 37 for calculating a particle velocity are provided. The average sound pressure information and the particle velocity information obtained by the average sound pressure calculation section 36 and the particle velocity calculation section 37 are introduced into the sound intensity calculation section 38. The sound intensity calculation unit 38 calculates the sound intensity based on both information.

On the other hand, an accelerometer 39 for obtaining a reference signal correlated with the generated noise is attached to the wall of the noise source 31. The reference signal obtained by the accelerometer 39 is Sent to On the one hand, the reference signal is introduced into the control coefficient FIR filter 40, where it is multiplied by the control coefficient to become the input signal of the speaker 32. The reference signal is further divided into two on the other side, one of which is introduced into the FIR filter 41 for the sound pressure coefficient, and the other is introduced into the FIR filter 42 for the particle velocity coefficient. Then, it is sent to the control coefficient calculation unit 43.

The control coefficient calculator 43 calculates the Filtered-XL
The FI for the control coefficient is adjusted so that the sound intensity radiated from the speaker 32 by the MS algorithm approaches zero.
The control coefficients (filter coefficients) of the R filter 40 are updated. That is, while the error signal is sound pressure in the conventional example described above, the error signal is sound intensity in this example, and the control coefficient of the control coefficient FIR filter 40 is set so that the value sequentially approaches zero. Will be updated.

The control coefficient can be updated by the following equation (11) similar to the equation (4).

[0050]

(Equation 5)

With such a configuration, the radiated sound power from the speaker 32, which is the additional sound source, can be made close to zero, so that the total sound power of the noise source and the additional sound source can be reduced as described above. it can. As a result, a good sound deadening effect can be exhibited.

When the noise source generates loud noise (a detailed embodiment relating to this will be described later), a plurality of additional sound sources are arranged for the noise source. In this case, it is necessary to simultaneously control the output from the additional sound source.

(Third Embodiment) Next, a third embodiment of the present invention will be described.

In the first embodiment described above, only one speaker as an additional sound source is provided. The noise source may generate noise in different modes at a plurality of locations. The present embodiment is directed to such a noise source,
Noise reduction effect by arranging additional sound sources corresponding to each mode and providing sound intensity measurement unit for each additional sound source, and performing control to minimize or minimize the sound power radiated from each additional sound source Is what you get.

FIG. 3 is a block diagram showing a schematic configuration of an active silencer according to a third embodiment of the present invention. In the figure, reference numeral 44 denotes a target device such as a transformer placed in a three-dimensional space;
That is, it is a noise source. This noise source 44 has a mode,
There are belly (maximum amplitude) and nodes (minimum amplitude).

FIG. 11 shows a case where the mode of the noise source 44 has two antinodes.
The control method for simultaneously reducing the antinode amplitude is described.

At the position of the antinode of the mode near the noise source 44,
The speaker 45 is arranged, and the speaker 46 is similarly placed on the adjacent belly.
Place. Two microphones 47, 48, 49, and 50 are arranged at predetermined intervals on the central axis of the vibration surface of the speakers 45 and 46. Microphone 47,
The sound pressure signal measured at 48 and the microphones 49,5
The sound pressure signal measured at 0 is introduced to the control device 51.

The control device 51 includes microphones 47 and 4
Arithmetic units 52 and 53 are provided for calculating an average sound pressure between microphones based on the sound pressure signals of 8, 49 and 50 and calculating a sound intensity which is a time average of particle velocities.

The noise source 44 is provided with an accelerometer 62 for obtaining a reference signal correlated with the noise generated therefrom. The reference signal obtained by the accelerometer 62 is
Sent to

On the one hand, the reference signal is
The signals are introduced into IR filters 56 and 57, where they are multiplied by control coefficients to become input signals to speakers 45 and 46. On the other hand, the reference signal is further divided into four, and the FIR filter 58 for the intensity coefficient from the speaker 45 obtained by the microphones 47 and 48, the microphone 4
FIR filter 59 for intensity coefficient from loudspeaker 46 obtained at 7 and 48, microphones 49 and 50
Are introduced into the FIR filter 60 for intensity coefficient from the speaker 45 obtained by the above, and the FIR filter 61 for intensity coefficient from the speaker 46 obtained by the microphones 49 and 50, and the product-sum operation with the original signal is performed. Later, it is sent to the control coefficient calculation units 54 and 55.

The control coefficient calculation units 54 and 55 are provided with Filter-X L
The control coefficients (filter coefficients) of the control coefficient FIR filters 56 and 57 are updated by the MS algorithm so that the sound intensity radiated from the speakers 45 and 46 simultaneously approaches zero. In addition, the update of the control coefficient is determined by the equation (1)
This can be done with the following expression that extends 1).

[0062]

(Equation 6)

With such a configuration, the radiated sound power from the speakers 45 and 46, which are the additional sound sources, can be made close to zero at the same time.
The overall sound power including the additional sound source can be reduced, and a good sound deadening effect can be exhibited.

When the noise source generates a loud noise (a detailed embodiment relating to this will be described later), a plurality of additional sound sources are arranged for the noise source. In this case, it is necessary to simultaneously control the output from the additional sound source. In the above-described example, a plurality of speakers controlled in parallel with the speaker 45 are provided, and a plurality of speakers controlled in parallel with the speaker 46 are provided.

(Fourth Embodiment) FIG. 4 is a block diagram showing a schematic configuration of an active silencer according to a fourth embodiment of the present invention.

In the figure, reference numeral 63 denotes a target device such as a transformer placed in a three-dimensional space, that is, a noise source. The noise source 63 has a mode, and has an antinode (maximum amplitude) and a node (minimum amplitude).

FIG. 9 shows a case where the noise source 63 has two bellies. In the present embodiment, the bellies are sequentially reduced one by one, and finally all the bellies are reduced. This is a description of a control method to be performed.

At the position of the antinode of the mode near the noise source 63,
At least one speaker 64 is disposed, and at least one or more speakers 65 are similarly disposed on the adjacent belly.

Two microphones 66, 67, 68, 69 are arranged at predetermined intervals on the central axis of the vibration surface of the speakers 64, 65. Microphones 66, 67
Sound pressure signal measured by the microphone 68,
The sound pressure signal measured at 69 is introduced to the controller 70.

The control device 70 includes microphones 66 and 6
Calculation units 71 and 72 are provided for calculating the average sound pressure between the microphones based on the sound pressure signals of 7, 68 and 69 and calculating the sound intensity which is the time average of the particle velocities.

The noise source 63 is provided with an accelerometer 80 for obtaining a reference signal having a correlation with the noise generated from the noise source 63. The reference signal obtained by the accelerometer 80 is
Sent to

On the one hand, the reference signal is introduced into the control coefficient FIR filter 74 inside the adaptive control operation section 75, where it is multiplied by the control coefficient to become an input signal to the speaker 64 or 65. The reference signal, on the other hand, is further divided and sent to an intensity coefficient FIR filter 78 from the speaker 64 determined by the microphones 66 and 67 or an intensity coefficient FIR filter 79 from the speaker 65 determined by the microphones 68 and 69. After being introduced and subjected to a product-sum operation with the original signal, the signal is sent to the control coefficient operation unit 74.

The feature of the above system is that, even if the number of additional sound sources increases as the number of bellies increases, unlike the apparatus of the second embodiment, the control coefficient calculation unit and the control coefficient FI
The point is that only one adaptive control operation unit 75 composed of an R filter is always required.

Here, a control procedure by a single adaptive control operation unit will be described.

[Procedure 1] A speaker 64 and microphones 66 and 6 are set near the antinode of the left side of the drawing.
7 and the acceleration sensor 80 are used to reduce the acoustic power of one belly.

In order to realize this, all the signal switching units 81, 82, 83, 84 are set to the side.

This corresponds to FIG. 5, in which sound is emitted only from the speaker 64. The advantage of this method is that the speakers can be placed properly,
Since the solution where the total acoustic power is minimized at that position is found and the optimum output (amplitude / phase) is obtained, the sound does not increase in another place.

Therefore, even if control is performed for the left antinode, the sound of the right antinode (opposite phase) is not adversely affected.
In the worst case, the right belly is unchanged and the sound does not increase.

Therefore, it is possible to sequentially execute the adaptive control on the loud surface. When the sound power from the speaker 64 becomes zero or minimum, the adaptive control ends, the control coefficient obtained by the adaptive control operation unit is sent to the fixed coefficient FIR operation unit, and the constant amplitude and the constant Sound having a phase characteristic is emitted.

[Procedure 2] In the procedure 1, a speaker 65, microphones 68 and 69, and an acceleration sensor 80, which are installed in the vicinity of the right belly which has not been lowered, are used.
Reduce the acoustic power of the belly.

To realize this, the signal switching section 8
1, 82, 83, 84 are all on the side.

This corresponds to FIG. 6, and the speaker 65 is used to reduce the right belly. At this time, sound is also radiated from the speaker 65, but a solution in which the total acoustic power is minimized with the speaker arranged is found, and the optimum output (amplitude /
Accordingly, even in this case, the right side of the target belly can be reduced without being adversely affected by the speaker 64, and the left side sound reduced in the procedure 1 does not increase.

The adaptive control ends when the sound power from the speaker 65 becomes zero or minimum. Note that the sound power component from the speaker 64 is also superimposed on the microphones 68 and 69 provided for measuring the sound power from the speaker 65. However, since the direct sound from the speaker 65 has a large contribution, the total sound power Does not lead to a significant deterioration in the reduction of

[Procedure 3] The control coefficient obtained by the adaptive control operation unit 75 is sent to the fixed coefficient FIR operation unit 77, and the speaker 65 always has constant amplitude / phase characteristics as shown in FIG. Sound is emitted.

When the noise source generates loud noise (a detailed embodiment relating to this will be described later), a plurality of additional sound sources are arranged for the noise source. In this case, it is necessary to simultaneously control the output from the additional sound source.

(Fifth Embodiment) FIG. 8 is a block diagram showing a schematic configuration of an active silencer according to a fifth embodiment of the present invention.

In the figure, reference numeral 85 denotes a noise source such as an engine placed in a machine room (closed space) of the private power generator. The present embodiment, in which sound radiated from the noise source 85 exists as a standing wave in the closed space 86, relates to a noise reduction method in a case where N standing waves predominate in the closed space 86. FIG. 8 shows a case where the resonance mode having two antinodes is dominant, and the noise reduction method of the present embodiment will be described with reference to FIG.

The speaker 87 is brought close to the noise source 85, and the speaker 87 is arranged at the same phase position of the mode to be controlled.

The sound radiation power from the speaker-added sound source resulting from the mutual interference between the noise source 85 and the speaker 87 is measured, and the output from the speaker 87 is controlled so that the measured sound power becomes zero or minimum.

On the center axis of the vibration surface of the speaker 87, two microphones 88 and 89 are arranged at a predetermined interval from each other. The sound pressure signals measured by the microphones 88 and 89 and the particle velocity signal are introduced into the control device 90.

The control device 90 includes microphones 88 and 8
An arithmetic unit 91 for calculating the average sound pressure between the microphones based on the sound pressure signal of No. 9 and calculating the sound intensity which is the time average of the particle velocity is provided.

On the other hand, the noise source 85 is provided with an accelerometer 95 for obtaining a reference signal correlated with the noise generated from the noise source 85. The reference signal obtained by the accelerometer 95 is also transmitted to the control device 90. Sent. On the one hand, the reference signal is introduced into the control coefficient FIR filter 93, where it is multiplied by the control coefficient to become the input signal of the speaker 87. The reference signal is further divided into two on the other side, and the speaker 87 obtained by the microphones 88 and 89 is used.
Are sent to an intensity coefficient FIR filter 94, and are sent to a control coefficient calculation unit 92 after performing a product-sum operation with the original signal.

The control coefficient calculation section 92 updates the control coefficient (filter coefficient) of the control coefficient FIR filter 93 so that the sound intensity radiated from the speaker 87 approaches zero by the Filter-X LMS algorithm.

With such a configuration, the radiated sound power from the speaker 87, which is an additional sound source, can be made close to zero, so that the sound power inside the closed space where the mode is excellent can be reduced. A great silencing effect can be exhibited. Here, unlike the free space, the modes are superimposed in the closed space, and the total acoustic power in the closed space is represented by Expression (a).

[0095]

(Equation 7)

The condition for minimizing the total sound power in the closed space is as follows.

[0097]

(Equation 8)

That is, assuming that the additional sound source is brought close to the sound source and placed at the same phase position of the mode, and all the N additional sound sources are controlled with the same phase, θ _sl = θ
_si (i = 1, 2,... N). Therefore, the output characteristic of the additional sound source when the total acoustic power in the closed space is minimized is given by Expression (b).

[0099]

(Equation 9)

The sound power equation (13) from the additional sound source resulting from mutual interference between the additional sound source and the sound source becomes zero.

[0101]

(Equation 10)

Therefore, if this power can be measured to be minimum or zero, the overall power can also be reduced.

When the noise source generates loud noise (a detailed embodiment relating to this will be described later), a plurality of additional sound sources are arranged for the noise source. In this case, it is necessary to simultaneously control the output from the additional sound source.

(Sixth Embodiment) FIG. 9 is a block diagram showing a schematic configuration of an active silencer according to a sixth embodiment of the present invention.

This embodiment is an embodiment in which the noise source described so far is a loud sound source and the output of one ordinary speaker is insufficient. In order to reduce the output load of one speaker, N speakers arranged in a distributed manner are provided to supplement the output attachment. In addition, according to this, 1
N sets of microphones are also required.

When the number of additional sound sources is one, the total sound power can be minimized when the sound radiation power from the additional sound source resulting from mutual interference between the noise source and the additional sound source is reduced to zero or minimum. However, even if there are a plurality of additional sound sources, the radiated power of the additional sound sources (strictly speaking, the power radiated from one additional sound source when the additional sound sources are sounded one by one, If the sum of the powers caused by mutual interference is made zero or a minimum, the total acoustic power becomes a minimum.

Here, a calculation example in which the effect of reducing the acoustic power when a plurality of additional sound sources are used for the sound transmitted through the wall surface is shown. The wall surface can be represented by a set of point sound sources.

First, as shown in FIGS. 10 (a) to 10 (d), a case is considered in which a plurality of additional sound sources are installed in a matrix in opposition to the wall surface.

The radiated power of the additional sound source alone at this time is as follows.

[0110]

[Equation 11]

The mutual radiation power between the additional sound source and the wall surface is as follows.

[0112]

(Equation 12)

The mutual radiation power between the wall elements is as follows.

[0114]

(Equation 13)

The total sound power is as follows.

[0116]

[Equation 14]

The power of the additional sound source is as follows.

[0118]

(Equation 15)

Therefore, even if there are a plurality of additional sound sources, the radiation power of the following additional sound source becomes zero.

[0120]

(Equation 16)

The amount of decrease in sound power during control is expressed by the following equation (22).
It is as follows.

[0122]

[Equation 17]

Therefore, even when a plurality of additional sound sources are used, the radiation power of the additional sound source (strictly speaking, the power radiated from one additional sound source when each additional sound source is sounded, If the control for minimizing or minimizing the sum of the powers caused by mutual interference is performed, the total sound power can be reduced.

FIG. 9 shows a system configuration for realizing this, and the control method is the same as that of FIG.

However, it should be noted that, compared to FIG. 3, even though N microphones and speakers are used, the power reduction control methods of the N additional sound sources must be simultaneous. As shown in FIG. 4, the power cannot be reduced one by one in order.

(Seventh Embodiment) FIG. 11 is a cross-sectional view showing a device attached to an active silencer according to a seventh embodiment of the present invention.

[0127] In any of the methods of reducing the acoustic power radiated from the noise source described in the present invention, it is a condition that the additional sound source is arranged close to the sound source. However, there are also cases where it cannot be approached from a thermal aspect such as engine noise. The conduit 400 shown in FIG. 11 is a measure proposed for this heat measure, and can guide and radiate the sound radiated from the additional sound source 401 to a predetermined area of the noise source 402.

It should be noted that even with a noise source having no thermal problem, by installing this conduit, the sound from the additional sound source can be made closer to the noise source, and the noise reduction effect can be further improved.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described. This embodiment relates to a private power generator to which the above-described active silencer is applied.

FIG. 12 is a diagram showing the appearance of the private power generator according to the present embodiment, and FIG. 13 is a block diagram showing a schematic configuration of the private power generator.

The in-house power generation device of the present embodiment can be changed from the rated specification of 16 kVA to 10
A self-powered emergency power generator capable of outputting up to 0 kVA, as shown in FIG. 12, which is a control device that automatically performs everything from power failure detection to automatic power supply and automatic stop at power recovery by a microcomputer, as shown in FIG. 1, an engine 2, an electric generator 3, a detecting unit 4 for detecting a vibration signal or an engine rotation pulse signal of the engine 2, and a control unit 20 for processing a signal obtained from the detecting unit 4 (see FIG. 13).
And a speaker 9 for emitting a signal generated by the control unit 20 as a sound to the engine sound, and a microphone 10 for monitoring the level of the engine sound. Features.

When a power failure occurs in an emergency, the microcomputer control unit 1 receives the power failure confirmation command, confirms the voltage establishment, and switches the power supply from the commercial power supply to the private power generation. As a result, the engine 2 operates, and power is supplied via the generator. When the engine 2 operates, the vibration of the engine correlated with the engine sound is detected by a detection unit (signal detection unit) 4 installed on the surface of the engine. By inputting this to the control device 1,
An engine sound is generated in the opposite phase, and the processed sound is emitted from the speaker toward the engine. The control is performed until the sound intensity detected by the two microphones spaced apart from each other on the axis perpendicular to the speaker vibration plane becomes zero or minimum. When this is zero or at a minimum, the radiated power of the engine is at a minimum and noise is reduced throughout the environment.

The device shown here is called a low-noise in-house power generation device, and is approximately 85 d in a surrounding area of 1 m (1.2 m above the floor).
B (A).

The ultra-low noise type (75 dB (A)), which is one rank higher than the above, has a higher performance than the 85 dB (A) type.
The volume becomes about 1.5 times. Low frequency noise of 10d
In order to reduce B, sound absorption processing with a small noise reduction effect in the low frequency range is dared to be performed, and the volume is increased and the area of the soundproof cover is increased. Therefore, if the proposed ANC device is mounted on an 85 dB (A) type device, a reduction of about 10 dB can be realized without changing the structure, the volume is the same, and a 75 dB (A) type ultra-low noise type is realized. Can be commercialized.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described. This embodiment relates to a transformer to which the above-described active silencer is applied.

The transformer according to the present embodiment has an iron core, a coil, insulating oil, and a tank covering these, and measures the dimensions, weight,
The capacity is increased by changing the number of windings of the coil and the magnetic flux density. In addition, the transformer of the present embodiment is provided with a soundproof cover and a soundproof tank in order to meet a required noise value at the time of delivery. It has an active silencer for silencing low-frequency electromagnetic noise.

It is usual to use a tripod core for a three-phase transformer, but if this is a large-capacity transformer to be transported by freight car, a five-leg core is used to fit it within the transport limit height.

[0138] Single-phase transformers are strictly restricted in Japan in transportation, and they are either special three-phase transformers composed of three single-phase transformers or very large and large-capacity 500kV transformers. Limited to those with strict transportation restrictions. For this reason, a two-leg core is well known as a single-phase transformer core, but in practice, a three-leg core, and for larger capacity, a four-leg or five-leg core is used. In the large-capacity device, since the amount of leakage magnetic flux increases, a large number of cooling oil passages are provided inside the iron core and forced cooling is performed to prevent local overheating.

A coil is wound around the iron core, and the capacity can be changed according to the number of turns. Winding end of disk winding,
In areas where the electric field is likely to concentrate, such as the layer ends of cylindrical windings or the joints of leads drawn from the coil, an insulating structure is provided to prevent excessive stress from being applied to the surrounding oil. Is further filled with insulating oil.

The noise generated from a transformer having a structure in which these are covered with a steel plate tank generally has the following three causes.
Are classified into two types.

1) Electromagnetic mechanical force between windings 2) Magnetic attraction force between seams of iron core and between layers 3) Magnetostrictive vibration of silicon steel plate (iron core) 1) and 2) Significant reduction is achieved by sufficiently tightening the wire and the core together. Therefore, generally, the noise according to 3) is regarded as transformer noise.

However, the noise generation mechanism in the case of 3) is quite complicated, and the noise changes under the influence of the magnetostriction characteristics, magnetic flux density, iron core size, weight, etc. of the silicon steel plate used. For example, if the iron core is constant, the magnetic flux density increases, the magnetostriction increases, and the noise tends to increase. The noise increases by 2 to 3 dB with an increase of 1000 gauss. Since the magnetostriction has a maximum value every half cycle of magnetization, a harmonic appears with a fundamental frequency twice the excitation frequency.

The vibration of the iron core is transmitted to the side of the tank through the following route.

1) Iron core → lower crossbar → tank bottom plate →
Side plate 2) Iron core → Insulating oil → Tank side Therefore, the conventional countermeasures were as follows.

1) Magnetostrictive vibration of the iron core is reduced.
Specific methods include reducing the magnetic flux density, selecting a steel plate material, and improving the tightening mechanism.

2) Vibration-proof support of the contents of the transformer with respect to the tank bottom.

3) An accumulator (bag filled with gas) is placed on the inner wall surface of the tank to prevent the transmission of vibration by the liquid.

4) The wall material of the tank is made to have a large loss coefficient.

If the required noise value at the time of delivery is not satisfied even if the above measures are taken, measures to further cover the transformer tank body are examined.

For example, a large capacity transformer of 100 to 300 MVA class employs the following various structures according to the required noise value.

1) Noise value 70 to 80 dB The side wall of the transformer main body is covered with a soundproof cover, and a low noise unit cooler with a reduced fan speed is used for the cooler.

2) Noise value 60 to 70 dB The transformer body is covered with a soundproof tank made of iron plate, and the cooler is
Employs a fan with lower fan speed or a low-noise unit cooler with a sound-absorbing duct.

3) Noise value 55 to 65 dB The transformer body is covered with a soundproof tank made of concrete panel, and the cooler employs a low noise unit cooler with a sound absorbing duct or a radiator bank.

4) Noise value 50 to 60 dB The transformer main body is installed inside a concrete soundproof building, the cooling system is generally an oil-feeding self-cooling system, and a radiation bank is installed outside the building.

As described above, if noise cannot be reduced at the iron core of the source, a large amount of work and cost are required for the countermeasure. For example, it is easy to see that noise can be reduced by completely covering the tank with concrete, but this not only increases costs but also significantly increases weight.
It is hard to say that this is the optimal method from the viewpoint of installation work.
The reason that noise countermeasures based on concrete must be adopted at present is that the main component of transformer noise is in the low range where the transmission loss coefficient is small. In the steel sheet class, the surface density cannot be obtained, so no sound insulation effect can be expected. Therefore, a method for reducing transformer noise by using active noise reduction technology, in which the noise reduction effect becomes better as the frequency becomes lower, will be examined.

In this case, the noise target is set to the following 2
Consider the noise countermeasures of transformers in the case of roughly dividing into two cases.

1) A case in which electromagnetic noise due to magnetic vibration of an iron core, which propagates through an insulating oil, is transmitted to a side wall of a transformer tank, and further penetrates the side wall surface and is radiated into a three-dimensional space (see FIG. 14) 2) When the entire transformer tank is covered with a soundproof cover, electromagnetic noise due to magnetic vibration of the iron core that penetrates the tank side wall surface, further penetrates the soundproof cover, and is emitted to the three-dimensional space is considered. FIG. 14 is a block diagram showing a first configuration example of a transformer including the active noise reduction device according to the present embodiment. As shown in the figure, an iron core 510, a coil 511, and an insulating oil 512 are accommodated in a tank (body) 513.

The active speaker 515 is a tank 513
The output of the controller 51
9. Also, the active speaker 51
The two microphones 516 and 516 are on the central axis of the vibration surface of No. 5.
517 are arranged at a predetermined interval from each other. The sound pressure signals measured by the microphones 516 and 517 and the particle velocity signal are introduced into the control device 519.

The control device 519 includes the microphone 51
An arithmetic unit is provided for calculating the average sound pressure between the microphones based on the 6,517 sound pressure signals and calculating the sound intensity, which is the time average of the particle velocities.

On the other hand, the tank 513 as a noise source has
Detection unit 5 for reference signal correlated with noise generated from here
Reference numeral 18 obtained by the detection unit 518 is sent to the control device 519. The reference signal is, on the one hand, introduced into the control coefficient FIR filter, where it is multiplied by the control coefficient to become the input signal of the speaker 515. The reference signal is further divided into two on the other side, introduced into the intensity coefficient FIR filter from the speaker 515 obtained by the microphones 516 and 517, and the product-sum operation with the original signal is performed. Later, it is sent to a control coefficient calculation unit (not shown).

The control coefficient calculator updates the control coefficient (filter coefficient) of the control coefficient FIR filter so that the sound intensity radiated from the speaker approaches zero by the Filter-X LMS algorithm.

FIG. 15 is a block diagram showing a second configuration example of a transformer provided with the active noise reduction device according to the present embodiment.
The second configuration example has a soundproof cover (or a soundproof tank) 514 that covers the entire tank 513, and the active speaker 515 is attached to the wall surface of the soundproof cover 514. FIG. 16 is a partial cross-sectional view showing a more specific structure of the transformer according to the second configuration example.

The input signals for active control include the above 1) 2)
In either case, a voltage signal or a current signal for exciting the coil is used. In the case of 1), the active speaker (additional sound source) is used to mitigate noise caused by the vibration of the soundproof cover in the case of 2).
Is installed near the vibrating surface (wall surface). Further, as described above, the acoustic intensity of the active speaker is measured by two microphones spaced apart on the axis of the vibration surface of the active speaker, and adaptive control is performed to minimize the sound intensity. Thereby, the acoustic radiation power transmitted from the vibration surface can be reduced, and the noise spreading in the three-dimensional space can be reduced.

At this time, if the vibrating surface has a mode, at least one active speaker is installed at the position of the antinode of the mode. If the sound intensity from each speaker can be reduced, all antinodes can be used. Thus, it is possible to reduce the wall-permeated sound power having the mode.

Note that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

[0166]

As described above, according to the present invention,
Noise generated by devices and the like arranged in a three-dimensional space can be reduced without complicating the configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing a model of a noise source and an additional sound source according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an active silencer according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of an active silencer according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of an active silencer according to a fourth embodiment of the present invention.

FIG. 5 is a view for explaining a control procedure by an adaptive control means according to the fourth embodiment.

FIG. 6 is a view for explaining a control procedure by an adaptive control means according to the fourth embodiment.

FIG. 7 is a view for explaining a control procedure by an adaptive control means according to the fourth embodiment.

FIG. 8 is a block diagram showing a schematic configuration of an active silencer according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of an active silencer according to a sixth embodiment of the present invention.

10 (a) is a perspective view schematically showing a state in which a plurality of additional sound sources are installed in a matrix form facing a wall surface, and FIG. 10 (b) is a diagram showing a plurality of additional sound sources in a matrix. (C) is a diagram showing a coordinate system of an additional sound source in a state in which a plurality of additional sound sources are installed in a matrix shape facing the wall, and a state in which the additional sound sources are installed facing the wall in a zigzag direction. (D) is a diagram of a state in which a plurality of additional sound sources are installed in a matrix shape facing the wall surface as viewed from the Z-axis direction.

FIG. 11 is a sectional view showing an attachment device for an active silencer according to a seventh embodiment of the present invention.

FIG. 12 is an external view showing a configuration of a private power generation device according to an eighth embodiment of the present invention.

FIG. 13 is a block diagram showing a schematic configuration of an active silencer applied to the private power generator according to the eighth embodiment.

FIG. 14 is a block diagram showing a first configuration example of an active silencer applied to a transformer according to a ninth embodiment of the present invention.

FIG. 15 is a block diagram showing a second configuration example of the active silencer applied to the transformer according to the ninth embodiment.

FIG. 16 is a partial cross-sectional view illustrating a configuration of a transformer according to the ninth embodiment.

[Explanation of symbols]

 22, 31 noise source 23 additional sound source 32 speaker 33, 34 microphone 35 control device 36 average sound pressure calculator 37 particle velocity calculator 38 acoustic intensity calculator 39 accelerometer 40 control coefficient FIR filter 41: FIR filter for sound pressure coefficient 42: FIR filter for particle velocity coefficient 43: Control coefficient calculation unit

Claims (20)

[Claims] 1. A private power generator having an active silencer that suppresses noise from an engine that drives a generator, comprising: a sound source arranged near the engine; an engine sound from the engine; Sound power measuring means for measuring sound power from the sound source resulting from mutual interference with sound; andcontrol means for controlling output from the sound source to minimize the sound power measured by the measuring means. An in-house power generator, comprising: 2. A transformer provided with an active silencer that suppresses noise from a tank containing an iron core, a coil, and insulating oil, wherein a sound source disposed near the tank and noise from the tank are provided. Sound power measuring means for measuring sound power from the sound source resulting from mutual interference between the sound source and the sound from the sound source; and controlling the output from the sound source to minimize the sound power measured by the measuring means. And a control means. 3. The transformer according to claim 2, further comprising soundproof means for covering a tank having an iron core, a coil, and insulating oil. 4. An active silencer for suppressing noise generated from a noise source, comprising: a sound source disposed near the noise source; and a sound power from the sound source resulting from mutual interference between the noise source and the sound source. An active silencer comprising: a sound power measuring means for measuring the sound power; and a control means for controlling an output from the sound source so as to minimize the sound power measured by the measuring means. 5. The sound power measuring means comprises sound intensity measuring means for measuring sound intensity emitted from the sound source as a result of mutual interference between the noise source and the sound source. The active silencer according to claim 4, wherein 6. The active device according to claim 4, wherein said control means sequentially supplies an input signal to said sound source such that a sound power measured by said sound power measuring means becomes zero. Silencer. 7. The control means is constituted by adaptive control means for independently controlling each of the sound sources,
7. The active silencer according to claim 6, wherein said adaptive control means controls a corresponding sound source such that acoustic powers of antinodes having the same phase plane of said noise source are simultaneously reduced. 8. The active silencer according to claim 7, wherein said adaptive control means comprises a filter and a calculation unit. 9. The active silencer according to claim 4, further comprising a guiding unit for guiding a sound emitted from the sound source to the noise source. 10. The active silencer according to claim 9, wherein said guide means is constituted by a conduit. 11. The active noise reduction device according to claim 4, wherein a mode including a belly and a node is provided before the noise. 12. The active noise reduction device according to claim 4, wherein the noise source generates a standing wave. 13. An active silencer for suppressing noise generated from a noise source, comprising: a sound source arranged near the noise source; and at least a sound source arranged on the same plane as a center axis of a vibration surface of the sound source. A sound intensity measuring means having two microphones for measuring a sound intensity of the sound source resulting from mutual interference between the noise source and the sound source; and a sound intensity measured by the measuring means becomes zero. Control means for controlling the output of the sound source as described above. 14. An active silencer for suppressing noise generated from a noise source, comprising: N (N is an integer) sound sources disposed in the vicinity of the noise source; Sound power measuring means for measuring sound power from the N sound sources resulting from mutual interference; and control means for controlling outputs of the N sound sources so that the sound power measured by the measuring means is minimized. An active silencer, comprising: 15. The apparatus according to claim 14, wherein the control means sequentially supplies input signals to the N sound sources so that the sound power measured by the sound power measuring means becomes zero. Active silencer. 16. The control means is constituted by a single adaptive control means for independently controlling each of the N sound sources, and the adaptive control means comprises an antinode having the same phase plane of the noise source. The active noise reduction device according to claim 15, wherein the sound sources are controlled one by one so that the acoustic power of the sound sources is reduced one by one. 17. An active noise reduction method for suppressing noise by mutual interference of sound between the noise source and the sound source generated by driving a sound source arranged near the noise source, the method comprising: Measuring the radiated acoustic power, and controlling the output of the sound source such that the measured acoustic power is minimized. 18. An active noise reduction method for suppressing noise from a noise source that emits a sound having a mode including a plurality of antinodes and nodes, wherein N (N is an integer) sound sources are arranged at antinode positions in the mode. Measuring the N sound powers from each sound source resulting from mutual interference between the noise source and each sound source; and measuring the N sound powers so that the N sound powers are minimized. Controlling the output of the sound source. 19. The control step is performed by N adaptive control means for independently controlling each of the N sound sources such that N antinodes of the noise source having the same phase plane are simultaneously reduced. 19. The method of claim 18, including controlling a corresponding sound source. 20. The method according to claim 19, wherein the controlling step includes a single adaptive control unit for controlling each of the N sound sources such that the N antinodes on the same phase plane of the noise source are reduced one by one. 19. The method of claim 18 including the step of controlling.