JPH07261770A - Low frequency noise reduction device - Google Patents

Abstract

PURPOSE:To efficiently prevent a comparatively low frequency noise also by substituting a noise generating source and a generation sound of an acoustic outputting means as a point sound source respectively, making the centers of both virtual point sound sources coincident, and arranging a noise generating source and a sound outputting means. CONSTITUTION:An acceleration sensor 4 detects vibration of a noise generating source of a low frequency such as a bowl feeder 1, converts mechanical vibration to an electric signal, and a band pass filter 5 selects a frequency component corresponding to a reduced frequency from this electric signal. A delay circuit 6 delays phases of each frequency component detected by the band pass filter 5 by the prescribed time and make it an opposite phase, and it is amplified by an amplifier circuit 7, outputted from a loudspeaker 8 being an acoustic output means. Then, a virtual point sound source M which can substitute sound generated by the bowl feeder 1 and the loudspeaker 8 as a point sound source respectively is set, the centers of both virtual point sound source M are made coincident, and the loudspeaker 8 is arranged for the bowl feeder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency noise reducing device used for a noise preventing device of a bowl feeder, etc., and particularly cancels a noise generated from a low frequency noise generating source with a sound of opposite phase. The present invention relates to a low frequency noise reduction device.

[0002]

2. Description of the Related Art As a conventional noise preventing device for a bowl feeder of this type, there is a technique disclosed in Japanese Patent Laid-Open No. 4-101918.

The technique disclosed in the above publication is a bowl feeder in which a movable table having a bowl is elastically supported on a fixed table, and a vibration generating means driven by an AC power source is provided between the movable table and the fixed table. A speaker provided in the bowl, a speaker driving means for driving the speaker based on a signal obtained by phase-inversion of a frequency component signal of the AC power supply output, and at least a part of an outer peripheral portion from the fixed base to the bowl. Since it is provided with a sound insulation cover, the sound on the bowl surface is canceled by the sound from the speaker, and the sound from the bottom surface of the bowl is blown out from the fixed base of the bowl feeder main body to the cylindrical outer peripheral part. Since the sound insulation cover with the sound absorbing material attached to the inner surface is used for sound insulation, the vibration noise to the outside can be significantly reduced.

[0004]

As described above, the sound on the bowl surface is canceled by the sound from the speaker, and the sound from the bottom surface of the bowl is blown out from the cylindrical outer peripheral portion from the fixed base of the bowl feeder main body to the bowl. Since the sound-insulating cover is attached to the sound-insulating material for sound insulation, the fixing base of the bowl feeder main body needs to be robust, and the apparatus becomes expensive accordingly. Further, if the frequency characteristic of the sound on the bowl surface and the frequency characteristic of the sound from the bottom surface of the bowl are different, noise cannot be reduced with high efficiency only by the sound from the speaker.
In the technique disclosed in the above publication, the bowl and the speaker are mechanically connected, so if the normal operation is performed,
It is expected that the vibration of the bowl will be canceled by the speaker and the output of the bowl feeder itself will decrease. Furthermore,
The technique disclosed in the above publication cannot be expected to be effective if the AC power supply frequency and the frequency corresponding to the peak value of noise do not match.

Further, according to experiments by the inventors, if the sound generated from the speaker side is generated from the speaker cone, it may not always be possible to eliminate the noise efficiently. That is, even if the frequency to be reduced is accurately determined and the frequency to be reduced generated in the noise generating source can be specified, the frequency to be reduced may not always be efficiently deleted.

[0006] On the other hand, low-frequency voice, although only slightly audible to humans, has a high possibility of affecting psychological and physiological actions. As a countermeasure against this, it is conceivable to shield the sound with a protective wall, but when the sound source is factory equipment, using a protective wall is likely to reduce workability. For example, in Japanese Examined Patent Publication No. 56-4667,
The bowl feeder is covered with a soundproof box. However, the workability at the time of inputting the work is sacrificed.

Therefore, the present invention aims to provide a low frequency noise reducing device capable of efficiently preventing noise even when the noise is relatively low, which is not related to the noise of the AC power source frequency, without impairing workability. It is what

[0008]

A low frequency noise reduction apparatus according to claim 1 detects a vibration of a low frequency noise source and converts the mechanical vibration into an electrical vibration, and Frequency extraction means for selecting a frequency component corresponding to the frequency to be reduced from the electrical signal detected by the vibration detection means, and outputting as a signal of the opposite phase of the frequency component,
An acoustic output unit that outputs mechanical vibration by the output of the frequency extraction unit is provided, and a virtual point sound source that can replace a sound generated by the noise generation source as a point sound source is set, and
A virtual point sound source capable of replacing the sound generated by the sound output means as a point sound source is set, and both virtual point sound sources are made to coincide with each other and the noise generation source and the sound output means are arranged.

In the low frequency noise reduction apparatus according to the second aspect, the vibration of the low frequency noise generating source is detected, and the vibration detecting means for converting the mechanical vibration into the electric vibration is detected by the vibration detecting means. A frequency component corresponding to the frequency to be reduced is selected from the electrical signal, and a frequency extraction unit that outputs the signal as an opposite phase signal of the frequency component and an acoustic output unit that outputs mechanical vibration by the output of the frequency extraction unit. Assuming the center position of a plurality of virtual point sound sources that can be replaced with sound with a plurality of frequencies to be reduced generated by the noise generation source as a point sound source, and sound with a plurality of frequencies to be reduced generated by the sound output means is provided. Assuming the center positions of a plurality of virtual point sound sources that can be replaced as point sound sources, the assumed center positions are made coincident, and the noise generation source and the sound output means are arranged. It is.

The low-frequency noise reduction apparatus according to claim 3 detects the vibration of the low-frequency noise source and converts the mechanical vibration into electrical vibration by the vibration detection means and the vibration detection means. A frequency component corresponding to the frequency to be reduced is selected from the electrical signal, and a frequency extraction unit that outputs the signal as an opposite phase signal of the frequency component and an acoustic output unit that outputs mechanical vibration by the output of the frequency extraction unit. Assuming a plurality of virtual point sound sources that can replace the sound with a plurality of frequencies to be reduced generated by the noise generation source as a point sound source, and the sound with a plurality of frequencies to be reduced generated by the acoustic output means as a point sound source Assuming the respective center positions of a plurality of virtual point sound sources that can be replaced, a plurality of the sound output means are provided that match the plurality of virtual point sound sources of the noise source. .

The low-frequency noise reduction device according to a fourth aspect of the present invention detects a vibration of a low-frequency noise generation source and converts the mechanical vibration into an electrical vibration, and the vibration detection means detects the vibration. A frequency component corresponding to the frequency to be reduced is selected from the electrical signal, and a frequency extraction unit that outputs the signal as an opposite phase signal of the frequency component and an acoustic output unit that outputs mechanical vibration by the output of the frequency extraction unit. It is assumed that a straight line connecting the centers of a plurality of virtual point sound sources that can replace the sound of a plurality of frequencies generated by the noise generation source as a point sound source, and the sound of a plurality of frequencies generated by the sound output means is a point sound source. Assuming a straight line connecting the centers of a plurality of virtual point sound sources that can be replaced as, the assumed straight lines intersect each other.

[0012]

According to the first aspect of the present invention, the virtual point sound source is set so that the sound generated by the low frequency noise source can be replaced as the point sound source, and the sound generated by the sound output means can be replaced as the point sound source. By setting a sound source, arranging the noise generating source and the sound output means to match both virtual point sound sources, and matching the virtual point sound sources of the noise generating source and the sound output means, the phase of the noise generating source The amplitude of the noise from the noise generation source is suppressed by the sound output means which is inverted.

According to the present invention, the center position of a plurality of virtual point sound sources which can replace the sounds of a plurality of frequencies to be reduced generated by the noise generating source as point sound sources is assumed, and the sound output means is desired to reduce. Assuming the center positions of a plurality of virtual point sound sources that can replace sounds with a plurality of frequencies as point sound sources, and arranging the noise generation source and the sound output means by matching the assumed center positions, the noise generation The sound output means in which the phase of the source is inverted suppresses the amplitude of the plurality of frequencies to be reduced from the noise generating source.

In the present invention, it is assumed that a plurality of virtual point sound sources capable of replacing the sounds of a plurality of frequencies to be reduced generated by the noise source as point sound sources are used, and that the plurality of frequencies of the plurality of frequencies to be reduced generated by the sound output means are assumed. Assuming a plurality of virtual point sound sources that can replace sounds as point sound sources, by arranging a plurality of the sound output means for the plurality of virtual point sound sources of the noise generation source, the phase of the noise generation source is inverted. The amplitude of the frequency to be reduced is suppressed by the acoustic output means having the desired frequency to be reduced by the acoustic output means corresponding to each frequency output from the noise generation source.

According to the present invention, a straight line connecting the centers of a plurality of virtual point sound sources capable of replacing the sound of a plurality of frequencies generated by the noise generating source as a point sound source is assumed, and the plurality of frequencies generated by the sound output means are used. Assuming a straight line connecting the centers of a plurality of virtual point sound sources that can replace sound as a point sound source, and arranging the assumed straight lines to cross each other, approximate both virtual point sound sources, and invert the phase of the noise source The generated acoustic output means suppresses the amplitude of the frequency to be reduced from the noise source.

[0016]

EXAMPLES The present invention will be described below based on specific examples.

<Basic Principle> Generally, when the noise source is extremely smaller than its wavelength, that is, the noise source of low frequency noise can be regarded as a point sound source. Therefore, looking at the wavelength of 120 [Hz], 2.85 [m]
Then, looking at the wavelength of the frequency 240 [Hz], 1.
It becomes 43 [m], and looking at the wavelength of frequency 360 [Hz], it becomes 0.95 [m], and the frequency is usually 480 [H].
Even if it cannot be said that the noise source is extremely smaller than the wavelength up to z], it can be said that the noise source is smaller than the wavelength.

Then, the actual measurement of the virtual point sound source of the bowl feeder 1 which can replace the sound generated by the noise generating source and having a plurality of frequencies to be reduced as the point sound source is as shown in FIG.

FIG. 1 is a conceptual explanatory view of a virtual point sound source measured by a bowl feeder.

When the phase distribution around the bowl feeder 1 is measured, it becomes as shown in FIG. 1 (a) or 1 (b). FIG. 1A shows a phase distribution when a pure sound having a frequency of 120 [Hz] is generated from the bowl feeder 1, and the virtual point sound source Y1 is located at a position apart from the bowl 2 which is the sound source of the bowl feeder 1 and above. I know that there is. On the other hand,
(B) is a phase distribution when the bowl feeder 1 generates a pure tone with a frequency of 240 [Hz].
Although 2 is inside the virtual point sound source Y1, it can be seen that it is located above the bowl 2 which is the sound source of the bowl feeder 1.

FIG. 2 is a conceptual explanatory view of the phase when the virtual point sound source of the bowl feeder and the virtual point sound source of the sound output means are located at a distance.

Here, as shown in FIG. 2, the bowl feeder 1
When the virtual point sound source Y1 of No. 1 and the virtual point sound source Z1 of the sound output means are located at a position separated by a distance Lo, an attempt is made to cancel the noise generated in the bowl feeder 1 with an output having the same amplitude and the same frequency in the opposite phase. However, if all the phases do not necessarily match, if the virtual point sound source Y1 and the virtual point sound source Z1 are the same,
The distance r1 and the distance r2 coincide with each other, and both phases logically coincide with each other, so that the noise of the frequency 120 [Hz] of the bowl feeder 1 can be completely suppressed.

<Concrete Circuit> FIG. 3 is an overall configuration diagram showing a low frequency noise reducing apparatus according to the first embodiment of the present invention. Figure 3
As is well known in the art, the bowl feeder 1 as the low-frequency noise source of this embodiment is composed of a bowl 2 and a fixed base 3 to which the bowl 2 is attached. An acceleration sensor 4 as a vibration detecting means of this embodiment is attached to a lower center portion of the bowl 2, and the acceleration sensor 4 vibrates by a shaker that converts AC electric energy into mechanical vibration energy (not shown). The mechanical vibration of is detected as electrical vibration. The output of the acceleration sensor 4 is input to the bandpass filter 5, where the output of each frequency component is detected and the output of each frequency component is measured by the output meter 9. Normally, when the commercial power supply is 60 [Hz],
The bowl feeder 1 doubles the bowl 2 frequency, that is, 1
Since it vibrates at 20 [Hz], twice as much noise is generated,
Further, the noise frequency that is an integral multiple thereof is superimposed. The delay circuit 6 delays for a predetermined time so that the phase of each frequency component detected by the bandpass filter 5 is reversed. Then, the output of the delay circuit 6 is set to a predetermined amplification factor by the amplifier circuit 7 and output to the speaker 8 as the sound output means. The speaker 8 is attached to the frame body 10 whose upper and lower sides can be arbitrarily set, It is separated by a predetermined distance L at a position facing 2 and has a center on the same axis (XX line in FIG. 3) as the center of the bowl 2. The speaker 8 as sound output means is housed in a housing 8a as an enclosure that outputs the sound only to the front. The predetermined distance L is the sum of the distance Z to the virtual point sound source M of the speaker 8 as the sound output means and the distance Y to the virtual point sound source M of the bowl feeder 1 as the noise generation source. That is, the virtual point sound source M of the speaker 8 and the virtual point sound source M of the bowl feeder 1
Is matched with.

In the figure, the band pass filter 5, the delay circuit 6 and the amplifier circuit 7 are configured so that they can be set for each frequency component, and the acceleration sensor 4 as the vibration detecting means of this embodiment detects them. The frequency extracting unit is configured to select a frequency component corresponding to the frequency to be reduced from the electrical signal and output the signal as a signal having a phase opposite to that of the frequency component.

<Circuit Operation> The bowl feeder 1 as a low frequency noise source of this embodiment is mechanically provided with an acceleration sensor 4 as a vibration detecting means of this embodiment, which is disposed below the center of the bowl 2. The vibration is detected as electrical vibration, and the output of the acceleration sensor 4 is input to the bandpass filter 5, where the output for each frequency component is detected and the output for each frequency component is displayed on the output meter 9. To do. Further, the delay circuit 6 delays for a predetermined time in order to make the phase of each frequency component detected by the bandpass filter 5 the opposite phase, and the output of the delay circuit 6 is set to a predetermined amplification factor by the amplifier circuit 7 and the speaker is set. Output from 8. This amplification factor is determined so that the amplitude of the corresponding frequency is minimized. At this time, the bowl feeder 1 as a noise generation source generates noise around the virtual point sound source M, and at the same time, the speaker 8 as the sound output means has a sound in a phase opposite to the noise around the virtual point sound source M. As a result, the noise of the bowl feeder 1 can be reduced by the output of the speaker 8.

Since the speaker 8 is housed in the housing 8a as an enclosure for outputting the sound only to the front, the sound behind the speaker 8 is blocked by the housing 8a.

<Other Embodiments> FIG. 4 is an explanatory view for explaining the arrangement of the noise generating source and the sound output means of the low frequency noise reducing apparatus of the second embodiment of the present invention, and FIG. 5 is the first embodiment of the present invention. It is explanatory drawing explaining the arrangement | positioning of the noise generation source and the sound output means of the low frequency noise reduction apparatus of 3rd Example.

In the figure, when the bowl feeder 1 as a noise generating source is a virtual point sound source M1 having a specific frequency, a virtual point sound source M2 having twice the frequency, and a virtual point sound source M3 having three times the frequency, First, the virtual point sound source M1 of a specific frequency and the speaker 18A housed in the housing 18a as the sound output means are arranged at the same position as the virtual point sound source M1 to match the frequency of the virtual point sound source M1 of the bowl feeder 1. Output. Further, the virtual point sound source M2 and the speaker 18B housed in the housing 18b as the sound output means are arranged at the same position as the virtual point sound source, and the output coincides with the frequency of the virtual point sound source M2 of the bowl feeder 1. . Similarly, the virtual point sound source M3 and the speaker 18C housed in the housing 18c as the sound output means are arranged at the same position as the virtual point sound source, and the output that matches the frequency of the virtual point sound source M3 of the bowl feeder 1 is obtained. To do. this,
The virtual point sound source M1 having a specific frequency, the virtual point sound source M2 having a frequency twice that of the bowl feeder 1, and the virtual point sound source M3 having a frequency three times that of the bowl feeder 1 are on the same straight line.

In this embodiment, the speaker 18A housed in the housing 18a is arranged above the straight line connecting the virtual point sound source M1, the virtual point sound source M2, and the virtual point sound source M3 of the bowl feeder 1. Since this kind of arrangement can release the periphery of the bowl feeder 1,
In particular, the workability is less likely to be affected in the case of supplying the processed parts from the lateral direction. Further, since the speaker 18B housed in the housing 18b and the speaker 18C housed in the housing 18c can open the upper portion of the bowl feeder 1, the workability is affected particularly when the machine parts are supplied from above. Hard to exert.

The speaker 18B housed in the housing 18b and the speaker 18 housed in the housing 18c.
In the case where the bowl feeder 1 is arranged around the bowl 2 as shown in C, it is effective for a virtual point sound source having a high frequency, and a pair of speakers are provided at opposing positions passing through the center of the bowl 2. By disposing it, noise can be suppressed more effectively.

In this kind of embodiment, a virtual point sound source M of a specific frequency of the bowl feeder 1 as a noise source.
1, the noise of the virtual point sound source M2 having twice the frequency thereof and the virtual point sound source M3 having the triple frequency thereof is suppressed by the frequency of the opposite phase by the speaker 18A, or the speaker 18B and the speaker 18C, respectively.

As described above, the low-frequency noise reduction device of the above embodiment detects the vibration of the low-frequency noise generating source such as the bowl feeder 1 and converts the mechanical vibration into the electrical vibration. And a frequency component corresponding to the frequency to be reduced from the electrical signal detected by the vibration detection unit and output as a signal having a phase opposite to that of the frequency component, for example, the bandpass filter 5 A frequency extracting means for delaying a predetermined time by the delay circuit 6 so that the phases of the respective frequency components detected in step 2 are reversed, and the output of the delay circuit 6 is an output set to a predetermined amplification factor by the amplifier circuit 7; A low-frequency noise reduction device comprising: a sound output unit including a speaker 8 that outputs mechanical vibrations by the output of the frequency extraction unit. Set the virtual point sound source M can substitute the sound generated by the raw source as a point source, also, a virtual point sound source M can substitute the sound generated by the sound output means as a point source
Is set and both the virtual point sound sources M are made to coincide with each other, and the noise generation source and the sound output means are set. This can be the embodiment of claim 1.

According to the embodiment of this type, the center of the virtual point sound source M which can replace the sound generated by the low frequency noise generating source such as the bowl feeder 1 as the point sound source is set, and
By setting the center of a virtual point sound source M capable of replacing a sound generated by a sound output means such as a speaker as a point sound source, and by making the centers of both virtual point sound sources coincide with each other, the noise generation source and the sound output means are set. Since the virtual point sound sources of the noise generation source and the sound output means are made to coincide with each other, the amplitude of the noise from the noise generation source can be efficiently suppressed by the sound output means in which the phase of the noise generation source is inverted.

Particularly, when the noise source and the virtual point sound source of the sound output means are made to coincide with each other, the position of the speaker constituting the sound output means is specified even if the virtual point sound source of the sound output means is specified. Therefore, the degree of freedom in arranging the speaker forming the sound output means is high. However, in the case of this kind of embodiment, a sound output means for each frequency to be erased is required.

That is, the low frequency noise reduction system of this embodiment comprises an acceleration sensor 4 for detecting the vibration of a low frequency noise generating source such as the bowl feeder 1 and converting the mechanical vibration into the electrical vibration. A vibration detecting means and a frequency component corresponding to a frequency to be reduced are selected from the electric signal detected by the vibration detecting means and output as a signal having a phase opposite to that of the frequency component, for example, a bandpass filter 5
A frequency extracting means for delaying a predetermined time by the delay circuit 6 so that the phases of the respective frequency components detected in step 2 are reversed, and the output of the delay circuit 6 is an output set to a predetermined amplification factor by the amplifier circuit 7; In a low-frequency noise reduction device comprising a sound output unit including a speaker 8 that outputs mechanical vibrations by the output of the frequency extraction unit, a sound generated by the noise generation source and having a plurality of frequencies to be reduced can be replaced as a point sound source. Assuming a plurality of virtual point sound sources M1, M2, ... Mn, and a plurality of virtual point sound sources M1, M2 ,. Assuming Mn, the plurality of assumed virtual point sound sources M1, M2, ... Mn are matched and the noise generating source and the plurality of acoustic output means, for example,
A plurality of speakers 18A, 1 for the bowl feeder 1
8B and 18C are set, and this can be the embodiment of claim 3.

In the case of this type of embodiment, virtual point sound sources M1, M2, ... Mn capable of replacing the sound generated by a low frequency noise generating source such as the bowl feeder 1 as a point sound source.
, And virtual sound sources M1, M2, ... that can replace the sound generated by the sound output means such as a speaker as a sound source.
..Mn is set so that the virtual point sound sources M1, M2, ... The output means can efficiently suppress the amplitude of noise from the noise source.

By the way, the virtual point sound source M3 of the bowl feeder 1 as the noise generating source of this embodiment and the housing 18 as the sound output means at the same position as the virtual point sound source.
Although the speaker 18C housed in c is arranged,
In the case of implementing the present invention, it is set at an intermediate position between a virtual point sound source M3 having a frequency three times the specific frequency of the bowl feeder 1 and a virtual point sound source M4 (not shown) having a frequency four times the specific frequency. However, since the virtual point sound source is approaching, the speaker 18C housed in the housing 18c set to the virtual point sound source that matches the virtual point sound source M3 has a frequency of three times the specific frequency of the bowl feeder 1. Virtual point sound source M3
Alternatively, the virtual point sound source M4 having four times the frequency may be set.

Alternatively, a virtual point sound source M1 having a specific frequency of the bowl feeder 1 as a noise generation source, a virtual point sound source M2 having twice the frequency thereof, and a virtual point sound source M3 having three times the frequency thereof.
It is also possible to dispose a speaker housed in a housing (not shown) as one sound output means, assuming an average position of, ..., That is, the center position.

That is, the low frequency noise reduction system of this embodiment comprises the acceleration sensor 4 which detects the vibration of the low frequency noise source such as the bowl feeder 1 and converts the mechanical vibration into the electrical vibration. A vibration detecting means and a frequency component corresponding to a frequency to be reduced are selected from the electric signal detected by the vibration detecting means and output as a signal having a phase opposite to that of the frequency component, for example, a bandpass filter 5
A frequency extracting means for delaying a predetermined time by the delay circuit 6 so that the phases of the respective frequency components detected in step 2 are reversed, and the output of the delay circuit 6 is an output set to a predetermined amplification factor by the amplifier circuit 7; In a low-frequency noise reduction device comprising a sound output unit including a speaker 8 that outputs mechanical vibrations by the output of the frequency extraction unit, a sound generated by the noise generation source and having a plurality of frequencies to be reduced can be replaced as a point sound source. , Mn are assumed, and a plurality of virtual point sound sources M1, M2 capable of replacing the sound generated by the sound output means with a plurality of frequencies to be reduced as a point sound source. , ..., Mn is assumed to be the center position, and the assumed center positions are made to coincide with each other to set the noise generating source and the sound output means. It can be.

According to this embodiment, the center positions of a plurality of virtual point sound sources M1, M2, ..., Mn capable of replacing the sound of a plurality of frequencies to be reduced generated by the noise generating source as a point sound source are assumed, and Assuming the center positions of a plurality of virtual point sound sources M1, M2, ..., Mn that can replace the sounds generated by the sound output means and having a plurality of frequencies to be reduced as point sound sources, and match the assumed center positions. By setting the noise generation source and the sound output means, the amplitude of the plurality of frequencies to be reduced from the noise generation source is suppressed by the sound output means in which the phase of the noise generation source is inverted.

Of course, virtual point sound sources M1, M2, ..., M
It is possible to associate one or more of n with the sound output means and average the others to set the center positions of several virtual point sound sources M1, M2, ..., Mn. Particularly, in this type of embodiment, it is not necessary to provide the sound output means for each frequency to be deleted, and the number of the sound output means can be reduced.

In this way, the virtual point sound source M of a specific frequency is
1, the virtual point sound source M2 having twice the frequency thereof and the virtual point sound source M4 having four times the frequency thereof have their noises suppressed by the frequencies of the opposite phases by the speaker 18A, the speaker 18B and the speaker 18C, respectively. The virtual point sound source M3 having a triple frequency and the virtual point sound source M5 having a triple frequency are present in the vicinity of the virtual point sound source M4 having a quadruple frequency. It is desirable to set to output.

Further, as shown in FIG.
Like a speaker 28A housed in a, it is arranged around the bowl 2 and a virtual point sound source M of a specific frequency above it is provided.
It is also possible to match 1 with the virtual point sound source of the speaker 28A. The speaker 28B housed in the housing 28b corresponds to the virtual point sound source M2 between the virtual point sound source M2 and the virtual point sound source M3 on the straight line connecting the virtual point sound source M1 and the virtual point sound source M2 of the bowl feeder 1. The virtual point sound source Z2 of the frequency to be set is set. In particular, in this embodiment, the virtual point sound source M3 is set to be between the virtual point sound source M2 and the virtual point sound source M3, or to the virtual point sound source M3 from the middle, and a slight phase disturbance is set as the virtual point sound source Z2 by the speaker 28B. The point sound source M2, the virtual point sound source M3, and noise of a higher frequency than that are canceled.

The low-frequency noise reduction device of this embodiment detects vibration of a low-frequency noise generation source such as the bowl feeder 1 and detects vibration of the mechanical vibration into electrical vibration. Means and a frequency component corresponding to the frequency to be reduced from the electrical signal detected by the vibration detection means, and outputs as a signal having a phase opposite to the phase of the frequency component. For example, each detected by the bandpass filter 5. The delay circuit 6 delays for a predetermined time in order to make the phase of the frequency component the opposite phase, and the output of the delay circuit 6 is the amplification circuit 7
In the low-frequency noise reduction device, the low-frequency noise reduction device is provided with: a frequency extraction means for producing an output set to a predetermined amplification factor by the above; and a sound output means comprising a speaker 8 for outputting mechanical vibration by the output of the frequency extraction means. Assuming a straight line connecting the centers of a plurality of virtual point sound sources M1, M2, M3 that can replace the sound of multiple frequencies generated by the source as a point sound source,
Further, a straight line connecting a plurality of virtual point sound sources M2 and M3 capable of replacing sounds generated by the sound output means with a plurality of frequencies as point sound sources is assumed, and the assumed straight lines intersect each other. Yes, this can be the embodiment of claim 4.

Therefore, a straight line connecting the centers of a plurality of virtual point sound sources capable of replacing the sound of a plurality of frequencies generated by the noise source as a point sound source is assumed, and the sound of a plurality of frequencies generated by the sound output means is generated by the point sound source. Assuming a straight line connecting the centers of a plurality of virtual point sound sources that can be replaced, the assumed straight lines intersect each other, approximate both virtual point sound sources, and acoustic output by inverting the phase of the noise source By the means, it is possible to suppress the amplitude of the frequency that is desired to be reduced from the noise source, and the degree of freedom in disposing the noise source is increased.

By the way, the vibration detecting means of the above embodiment is
The acceleration sensor 4 detects the vibration of the bowl 2 and converts the mechanical vibration into the electrical vibration. However, when the present invention is implemented, the vibration of the bowl 2 is detected and the mechanical vibration is detected. It suffices as long as it can convert electrical energy into electrical vibration.

Further, the frequency extracting means of the above embodiment comprises the low-pass filter 5 for selecting the frequency component corresponding to the peak value of noise from the electric signal detected by the vibration detecting means. In this case, it is only necessary that the frequency component corresponding to the peak value of noise can be selected from the electric signal detected by the vibration detecting means.

The embodiment of the present invention has been described on the assumption that noise is generated in the bowl 2 of the bowl feeder 1. However, in the case of carrying out the present invention, the bowl 2 and the fixed mounting of the bowl 2 are fixed. Even if noise is generated on any of the stand 3,
Similarly, a virtual point sound source of the noise generation source may be set, and the virtual point sound source may be used as the virtual point sound source of the noise generation source. Of course, the virtual point sound source may be incorporated in the housing of the bowl feeder 1.

[0049]

As described above, the low frequency noise reduction apparatus according to claim 1 sets the virtual point sound source capable of replacing the sound generated by the low frequency noise source as the point sound source, and the sound output means. Also, a virtual point sound source that can replace the generated sound as a point sound source is set, and the noise generation source and the sound output means are arranged so as to match both virtual point sound sources, and the noise generation source and the sound output means are virtual. By making the point sound sources coincide with each other, the amplitude of the noise from the noise generating source is suppressed by the acoustic output means in which the phase of the noise generating source is inverted.

Therefore, the degree of freedom in arranging the sound output means is high, workability is not impaired, and noise can be effectively prevented even in the case of relatively low noise unrelated to the noise of the AC power supply frequency.

The low-frequency noise reduction device according to claim 2 assumes the center position of a plurality of virtual point sound sources capable of replacing, as a point sound source, sounds of a plurality of frequencies to be reduced generated by a noise source,
Further, assuming a center position of a plurality of virtual point sound sources capable of replacing sounds generated by the sound output means and having a plurality of frequencies to be reduced as point sound sources, and matching the assumed center positions with each other, the noise source and the sound output. By providing the means, the acoustic output means in which the phase of the noise generating source is inverted, suppresses the amplitude of a plurality of frequencies to be reduced from the noise generating source.

Therefore, there is no need to prepare the sound output means for each of a plurality of frequencies for which reduction is desired, and the device can be manufactured at low cost. Further, the degree of freedom in arranging the sound output means is high, and it is possible to efficiently prevent noise in a comparatively low noise unrelated to the noise of the AC power supply frequency without impairing workability.

The low-frequency noise reduction device according to claim 3 assumes a plurality of virtual point sound sources capable of replacing, as point sound sources, sounds of a plurality of frequencies generated by a noise generation source, and is generated by the sound output means. Assuming a plurality of virtual point sound sources capable of replacing sounds of a plurality of frequencies to be reduced as point sound sources, by disposing a plurality of the sound output means for the plurality of virtual point sound sources of the noise source, the noise generation The amplitude of the frequency to be reduced by the acoustic output means corresponding to each frequency output from the noise generation source is suppressed by the acoustic output means of the frequency to be reduced by inverting the phase of the source.

Therefore, since the amplitude of the frequency to be reduced is suppressed by the acoustic output means corresponding to each frequency output from the noise generating source, the amplitude of the frequency to be reduced can be efficiently suppressed, and the acoustic output means can be suppressed. The degree of freedom in arranging is high, and it is possible to effectively prevent noise in a comparatively low noise which is not related to the noise of the AC power source frequency without impairing workability.

The low-frequency noise reduction device according to claim 4 assumes a straight line connecting the centers of a plurality of virtual point sound sources capable of replacing the sound of a plurality of frequencies generated by the noise generating source as a point sound source, and the sound output means. Assuming a straight line connecting the centers of a plurality of virtual point sound sources that can replace the sound with a plurality of generated frequencies as a point sound source, and the arrangement where the assumed straight lines intersect with each other,
The plurality of virtual point sound sources are approximated to each other, and the amplitude of the frequency desired to be reduced from the noise generation source is suppressed by the acoustic output means in which the phase of the noise generation source is inverted.

Therefore, by arranging the straight lines connecting the centers of the virtual point sound sources close to each other, the degree of freedom in arranging the sound output means is high, the workability is not impaired, and the comparison is not related to the noise of the AC power supply frequency. In low noise,
Noise can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory diagram of a virtual point sound source measured by a bowl feeder.

FIG. 2 is a conceptual explanatory diagram of a phase when a virtual point sound source of the bowl feeder and a virtual point sound source of the sound output means are located at a position separated by a distance.

FIG. 3 is an overall configuration diagram showing a low frequency noise reduction device according to a first embodiment of the present invention.

FIG. 4 is an explanatory view for explaining the arrangement of the noise generating source and the sound output means of the low frequency noise reducing apparatus according to the second embodiment of the present invention.

FIG. 5 is an explanatory view for explaining the arrangement of the noise generating source and the sound output means of the low frequency noise reducing apparatus of the third embodiment of the present invention.

[Explanation of symbols]

 1 Bowl Feeder 2 Bowl 3 Fixed Base 4 Acceleration Sensor 5 Bandpass Filter 6 Delay Circuit 8 Speaker M Virtual Point Sound Source 18a, 18b, 18c Housing 18A, 18B, 18C Speaker 28a, 28b Housing 28A, 28B Speaker

Claims (4)

[Claims] 1. A vibration of a low frequency noise source is detected,
A vibration detecting means for converting the mechanical vibration into an electric vibration and a frequency component corresponding to a frequency to be reduced from the electric signal detected by the vibration detecting means are selected and output as a signal having a phase opposite to the frequency component. In a low frequency noise reduction device comprising frequency extraction means and acoustic output means for outputting mechanical vibration by the output of the frequency extraction means, a virtual point sound source capable of replacing the sound generated by the noise generation source as a point sound source. Setting a virtual point sound source capable of replacing the sound generated by the sound output means as a point sound source, and arranging the noise generating source and the sound output means by making the centers of both virtual point sound sources coincide with each other. Low frequency noise reduction device characterized by. 2. A vibration of a low frequency noise source is detected,
A vibration detecting means for converting the mechanical vibration into an electric vibration and a frequency component corresponding to a frequency to be reduced from the electric signal detected by the vibration detecting means are selected and output as a signal having a phase opposite to the frequency component. In a low frequency noise reduction device comprising frequency extraction means and acoustic output means for outputting mechanical vibrations by the output of the frequency extraction means, a plurality of frequencies of sounds to be reduced generated by the noise source are replaced as point sound sources. Assuming the center position of a plurality of virtual point sound sources that are possible, and assuming the center position of a plurality of virtual point sound sources that can replace sounds generated by the acoustic output means and having a plurality of frequencies to be reduced as point sound sources, the assumed center A low-frequency noise reduction device, characterized in that the noise generating source and the sound output means are arranged at the same position. 3. A vibration of a low frequency noise source is detected,
A vibration detecting means for converting the mechanical vibration into an electric vibration and a frequency component corresponding to a frequency to be reduced from the electric signal detected by the vibration detecting means are selected and output as a signal having a phase opposite to the frequency component. In a low frequency noise reduction device comprising frequency extraction means and acoustic output means for outputting mechanical vibrations by the output of the frequency extraction means, a plurality of frequencies of sounds to be reduced generated by the noise source are replaced as point sound sources. Assuming a plurality of virtual point sound sources that can be used, and assuming a plurality of virtual point sound sources that can replace sounds generated by the acoustic output means and having a plurality of frequencies to be reduced as point sound sources, a plurality of virtual point sound sources of the noise source A low frequency noise reduction device, characterized in that a plurality of the sound output means matched with the above are provided. 4. A vibration of a low frequency noise source is detected,
A vibration detecting means for converting the mechanical vibration into an electric vibration and a frequency component corresponding to a frequency to be reduced from the electric signal detected by the vibration detecting means are selected and output as a signal having a phase opposite to the frequency component. In a low frequency noise reduction device comprising frequency extraction means and acoustic output means for outputting mechanical vibration by the output of the frequency extraction means, a plurality of sound sources of a plurality of frequencies generated by the noise generation source can be replaced as point sound sources. Is assumed to be a straight line connecting the centers of the virtual point sound sources, and a straight line connecting the centers of a plurality of virtual point sound sources capable of replacing the sound with a plurality of frequencies generated by the sound output means as a point sound source, and the assumed straight line A low-frequency noise reduction device characterized by being arranged so that they intersect with each other.