JPH07104771A - Silencer - Google Patents

Abstract

PURPOSE:To make it possible to rapidly silence a noise source at a low cost even if this noise source has any size and any shape. CONSTITUTION:A noise detecting microphone 5 is disposed near a noise source 7 and detection signal thereof is supplied to a silencing signal forming device 3, output signal from which drives a speaker disposed to face a slit opening 2 in a casing 2. The sound waves from the speaker are led outward from the opening 2 as a silencing sound wave releasing part and inverts the various densities of the sound from the various densities of the noise source generated from the noise source 7 to offset and silence the noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer.

[0002]

2. Description of the Related Art As a noise source, for example, various vibration application devices can be considered. These include a vibration conveyor, a vibration screen, a drum shaker, etc. Are various vibration exciters such as an electromagnetic vibration drive unit, a crank drive unit, and a pair of vibration motor drive units. By vibrating a trough having a U-shaped cross section, various materials and articles are further added. Similarly, the vibrating screen is a device in which a net is stretched over a trough having a U-shaped cross section, and the powder and granules are transferred thereon by vibration to perform screening. Further, the drum shaker, which will be described later in detail, is a device for separating the sand and the casting by putting a mold after pouring molten iron into the drum and vibrating it. These devices generate noise and cause pollution.As measures to prevent this noise, for example, surround the device with a fence, cover the whole device with a cover, or keep away from the complaining private house. It is possible to install such measures.

However, when it is surrounded by a wall, the wall blocks the propagation of sound in the horizontal direction to reduce noise, and when it is covered with a cover, the noise is certainly blocked by this cover, and outside. Noise is reduced. Also, when installed away from private houses, distant noise diffuses while propagating in the air and is absorbed by the ground, etc., which reduces noise, but has the following drawbacks: Is.

That is, when the noise source is surrounded by a fence, the height of the fence must be sufficiently large in order to prevent noise from wrapping around the fence. in this case,
Maintenance of the noise source inside this fence is difficult, and if this noise source is a vibration application device, for example, powdered material or
This causes a problem that it is difficult to supply or discharge the conveyed goods or parts. In addition, if it is surrounded by a fence, for example, even if the noise of 100 Hz is attenuated by 10 dB, it will be 4 meters or more.
At 0 Hz noise, a height of 6 meters or more is required.

When the whole is covered with a cover, not only is it very difficult for workers to come in and out, cleaning of dust and the like, maintenance such as oil supply and replacement of consumables, supply and discharge of granular materials, and The cost of installing such a silencer is very high. Also, in the case of covering with a cover, in reality, the device itself is not completely covered, but some kind of inlet and outlet must be provided for the supply and discharge of the powdery material, and heat dissipation,
It is necessary to provide some openings for each ventilation. In this case, since sound leaks from these openings, a sufficient effect cannot be expected.

Further, when installing away from a private house, it suffices if a sufficiently distant installation place can be secured, but such a place cannot be secured in many cases due to factors such as the building and site area depending on the factory. Here, the vibrating drum previously developed by the present applicant will be described as an example with reference to FIGS.

This will be described below. The vibrating drum is designated by 14 as a whole, and in the drawing of the cylindrical drum body 15, a casting supply port 16 of the casting to be sanded is formed at the left end, and an outlet 17 of the processed casting is formed at the right end. Is provided. The drum body 15 has a vibration-proof spring 18.
The counterweight 19 is supported on the ground 21 by the vibration-proof spring 20.
It is supported by. The vibration of the counter weight 19 prevents a large vibration force from being transmitted to the ground 21.

An exciter 22 is attached to one side of the drum body 15. The exciter 22 is mainly composed of an electric motor 23, a rotary shaft 27 connected to the electric motor 23 and having universal joints at both ends thereof, and an exciter 25 (not shown). Built-in parallel weights). The vibration unit 25 is fixed to mounting plates 26a and 26b mounted on the drum body 15. Electric motor 2
3 is supported on the ground 21 by a supporting portion 23A. Both ends of the rotary shaft 24 are respectively coupled to the rotary shaft of the electric motor 23 and the rotary shaft rotatably supporting the non-parallel weight of the vibrating portion 25 via universal joints.

The vibrating drum 14 previously developed by the present applicant is constructed as described above, and its operation will be described below. A casting to be blasted out is introduced into the supply port 16, and when the vibration exciter 22 is driven, the non-parallel weight 28 in the vibration exciter 25 rotates in the arrow direction as shown in FIG. As a result, the drum body 15 vibrates as a whole around the center of gravity as indicated by the arrow V, but if the center of gravity of the entire body is G as shown in FIG.
In the peripheral wall portion of No. 5, elliptical vibration is performed as described in Japanese Patent Application No. 2-407416 filed by the present applicant. The sizes of the major axis and the minor axis of this elliptical vibration are shown in FIG.
5 shows the distribution as shown in FIG.
The casting M with a large amount of the casting sand S deposited in the inside of FIG.
9 performs a circulating movement as indicated by an arrow P, and while performing this movement, the supply port 16 of the drum body 15 to the discharge port 1
7, the casting sand S separated during this time removes heat of vaporization by the casting sand S to cool the casting M and the binding force of the casting M decreases, so that the sand S is separated and the discharge port 1
Emitted from 7.

Although the drum body 15 is subjected to the above-mentioned sand blasting treatment of the casting, as described in the above-mentioned application, compared with the conventional drum body in which the peripheral wall portion performs linear vibration, The bass noise to the external environment has been greatly reduced, and yet this frequency is as low as a few Hz to 20 Hz, which is inaudible to the human ear, but low frequency noise is emitted to the surrounding buildings. Wake up,
That is, not only does rattling cause the building to rattling, but it may also cause damage to a part of the building. In view of the above problems, the applicant has
A vibrating drum device that is supported on the ground by a vibration-proof spring and a vibrating drum body for the purpose of providing a vibrating drum device capable of preventing low-frequency noise from the surroundings even for the vibrating drum developed previously The entire vibrating drum consisting of the vibration exciter is covered with a cover, and the first part
An opening is formed, the first duct is airtightly attached thereto, the second opening is formed in the other part of the cover, and the second duct is airtightly attached to the second opening, and the outer opening of the first duct is formed. The object to be treated in the drum body from the second duct is introduced into the supply port of the drum body, treated in the drum body, and discharged from the discharge port of the drum body. Is discharged to the outside through the outer opening of the first duct, and a sound wave generating means and a sound wave detecting means are provided in the first duct and the second duct, respectively, and the sound wave detecting means is respectively provided in the first and the second ducts. The sound wave generated in the duct of No. 2 is detected, and the sound wave generating means generates a sound wave for silencing having the same level as the sound wave in each of the outer openings, but the density is in the opposite phase. , Second
A vibrating drum device has been developed which is characterized in that sound waves are reduced or eliminated at each outer opening of the duct. Next, a specific example will be described.

In FIG. 20, the entire vibrating drum 14 is covered with an iron plate 30 having a sufficiently large thickness, and in FIG. 1, the supply port 16 and the supply port 16 formed in the drum body 15 are formed on the left wall portion and the right wall portion. The opening 30a corresponding to the discharge port 17,
30b is formed, and the first duct 31A and the second duct 31B are airtightly fixed to this, for example, by welding.
These inner open ends are separated from the drum body 15. That is, it is vibration-insulated. First duct 31A
An active noise control device ANC is attached to the second duct 31B.

Since the ANCs attached to the first and second ducts 31A and 31B have the same circuit configuration, only the side of the first duct 31A will be described below.

The first duct 31A and the second duct 3
First and second sound wave sensors 32 and 33 as a sensor microphone and an error microphone are attached to the inner wall of 1B, respectively, and the analog output of the first sound wave sensor 32 is increased by a thickener 36. It is supplied to the A / D converter 37, where the analog value is converted into a digital value,
It is supplied to one input terminal of the subtractor 38. The output of the digital filter 41 is supplied to the other input terminal,
Here, the sound wave emitted from the speaker 35 detected by the sensor microphone 32, that is, the howling component is subtracted, and the result is supplied to the coefficient calculator 39 and the adaptive filter 40. The coefficient calculator 39 changes the coefficient and transfer function of the adaptive filter 40 according to parameters that change with time in an actual noise environment, such as atmospheric pressure, temperature, humidity, sound pressure, and frequency components. As a result, a sound wave signal is generated such that a sound wave, which has the same level as the sound wave detected by the sensor 32 as a digital value but the density is reversed, is obtained at the position of the error microphone 33. D /
In the A converter 42, the digital input is converted into an analog force output, which is widened by the widening device 43 and then the speaker 35.
Is supplied to. Thereby, the first and second ducts 31A, 3
The sound wave transmitted from the vibrating drum 14 in 1B can be made substantially zero at the position of the error microphone 33, but the analog output detected by the second sound wave sensor 33 is amplified by the amplifier 45. This is converted into a digital value by the A / D converter 44 and supplied to the above-mentioned coefficient calculator 39, where a predetermined calculation is performed. That is, the first,
If the sound wave level in the second ducts 31A and 31B is not zero at the position of the error microphone 33, this is corrected.

As described above, in the specific example, at the position of the error microphone 33, that is, at the openings 34a and 34b, the sound wave can be greatly reduced or can be made zero.

The above-mentioned device surely eliminates the vibration of the vibrating drum 14, which has conventionally caused pollution at an extremely low frequency. However, as described above, the entire cover is covered with the cover 30. However, since the openings are formed in both end wall portions and ducts 31A and 31B are provided so that the casting to be processed and the casting are discharged through the ducts 31A and 31B, the problems of material supply and discharge can be avoided. However, since the entire large-scale vibrating drum is covered with the cover 30 and the iron plate having a considerable thickness, its installation cost is very high and maintenance is difficult.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and makes it easy to maintain the noise emitted from various noise sources to the surroundings at low cost and to supply an object to be treated by the noise source. It is an object of the present invention to provide a silencer that does not make discharge difficult.

[0017]

[Means for Solving the Problems] The above object is to provide a casing having an opening and provided with sound wave generating means for generating a silencing sound wave from the opening, and a noise disposed near the noise source. One or a plurality of muffling units provided with a detection unit and at least a muffling signal generation device that receives the detection signal of the detection unit and drives the sound wave generation unit, close to or around the noise source. It is achieved by a silencer characterized by being provided.

Further, the above object is to provide a sound wave generating means, a noise detecting means, and at least a detection signal of the detecting means,
This is achieved by one or a plurality of muffling units provided with a muffling signal generating device for driving the sound wave generating means in the vicinity of a noise source.

[0019]

By simply disposing the noise reduction unit around the noise source, the noise generated from the noise source inside can be silenced. If this noise source is some kind of work device, it is possible to easily supply and discharge the articles to be subjected to the work, and simply arrange the muffling units prepared in advance according to the size of the noise source. Since it is good, the installation cost can be greatly reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A silencer according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a muffler of this embodiment having one unit or one channel. The whole is shown by S, and the upper wall portion of the closed casing 1 whose shape is clearly shown in FIG. Has a slit-shaped elongated rectangular opening 2, and a speaker 6 is formed in the center of the bottom wall so as to face the opening 2.
Are attached to the mounting plate 10 and arranged. As shown in FIG. 2, the closed casing 1 is divided into two sound paths 9a and 9b by a partition plate 8, and the speaker 6 is attached to the central portion of the attachment plate 10.
In addition, the partition plate 8 covers the closed casing 1 in equal spaces 9a , 9
Since it is divided into b , the center of the partition plate 8 faces the lower edge portion 8a of the partition plate 8 and is mounted on the mounting plate. The noise source 7 is, for example, the above-described vibrating drum, and a noise detection microphone 5 is disposed between this and the closed casing 1 in the vicinity thereof, and a detection signal of the noise detection microphone 5 is supplied to the muffling signal generation device 3. ing. Further, a muffling deviation detection microphone 4 is arranged above the opening 2 formed in the upper wall portion of the closed casing 1, and a detection signal of the muffling deviation detection microphone 4 is also supplied to the muffling signal generation device 3. Upon receiving the detection signal of the noise detection microphone 5 and the detection signal of the muffling deviation detection microphone, for example, an ANC (Active Noise) as shown in FIG. 19 described in the conventional example.
e Control) circuit is applied, but the drive signal generated by this algorithm is applied to the drive unit 6 of the speaker 6.
It is supplied to a.

The muffling unit S according to the embodiment of the present invention is constructed as described above, and an arrangement example of such a unit S is shown in FIGS. That is, in FIG. 3 of the first arrangement example, S ₁ equivalent to the muffling unit S configured as described above is arranged adjacent to the noise source 7 so as to surround the noise source 7. . These muffling units S ₁ are the same as the muffling units S in the above-described embodiment except that the inside of the casing 1 is not partitioned by the partition plate 8 and the ratio of the height to the lateral length is different. One speaker is provided on the bottom wall portion so as to face the opening 2a formed in the wall portion. The height of the noise source 7 and the height of the muffling unit S ₁ are equal. With such a configuration of the muffling unit S ₁ , it is possible to prevent the noise generated by the noise source 7 from propagating to the outside.

FIG. 4 shows the second arrangement, but the noise source 7
Only along one long side of one of the muffling units S ₁ , S ₂
Is provided. Although the configuration of S ₁ is the same as the configuration of FIG. 3, the muffling units S ₂ arranged at both ends are not a quadrangle but a pentagon, and the upper wall portion, the side wall portion, and the slant between them. Openings 2b, 2d, 2c are formed in the wall.
Such silencing units S ₁ and S ₂ are not arranged on the other long side, but the side facing this is, for example, the case where there is no sea, field or house. In the muffling unit S ₂ , the radiation openings 2c, 2
By forming d, it is possible to muffle noise that wraps around from both sides.

FIG. 5 shows the third arrangement. In this example, the noise source 7 is relatively long, and the noise reduction units S ₁ are arranged adjacent to each other along both sides of the noise source 7 to reduce noise. The muffling unit S ₁ is arranged so as to extend to a position considerably distant from both ends of the source 7, but instead of the muffling unit S ₁ , the pentagonal muffling unit S ₂ shown in FIG.
If both ends are used, this length can be further shortened.

The silencer according to the embodiment of the present invention is constructed as described above, and its operation will be described below.

Active noise control (ANC)
The detection signal of the silence deviation detection microphone 4 and the detection signal of the noise detection microphone 5 are supplied to the silence signal generation device 3 as a circuit. This is the conventional sensor microphone 32 in FIG.
Also, the output of the noise detecting microphone 5 corresponding to the error microphone 33 is supplied to the amplifier 36 in FIG. 19, and the detection signal of the muffling deviation detecting microphone 4 is supplied to the amplifier 45. The D / A converter 42 is installed in the driving unit 6a of the speaker 6.
Is amplified and a muffling signal is generated, which is supplied to the drive unit 6a. The speaker 6 has a known configuration and is provided with a cone-shaped cone paper. By vibrating the cone paper up and down, the sound deadening sound waves are divided into sound paths 9a and 9b in the closed casing 1 and propagated. Sound path 9a , 9
b serves to limit the spread of the sound wave generated by the speaker 6, and as a result, to emit a uniform sound-deadening sound wave that is time-aligned at any position of the opening 2 as the sound-deadening sound wave emitting portion. Therefore, this opening 2 uniformly radiates the sound-deadening sound wave into the space to be muted. Furthermore, this sound-deadening sound wave has a long and narrow opening,
Although it diffuses widely in the target space, the interference with the silencing sound wave generated from the adjacent unit is small. As described in the prior art, the zero-level detection signal is detected if the sound-deadening deviation detecting microphone 4 is completely muted at the position. However, if there is a certain deviation, the sound-deadening signal generating device 3 The algorithm in the inside works so that the noise is not propagated outside the noise source 7.

In the above embodiments, the closed casing has a shape in which large and small rectangular parallelepipeds are stacked, but instead of this, a closed casing having a shape as shown in FIGS. 5 to 8 may be used. That is, the closed casing 1A of FIG. 5 has an R shape (arc portion) on the front surface thereof and has an arc shape, and a slit-like opening A similar to that of the embodiment is provided near the upper end portion of the right side wall portion. Although provided, in the present invention, the upper wall portion of the closed casing includes such a portion. Also, the speaker 6 is the mounting plate 1 which is obliquely arranged as in the embodiment.
It is attached to 0A.

The closed casing 1B shown in FIG. 6 has a shape in which rectangular parallelepipeds of substantially different sizes are stacked, as in the embodiment, and a slit-shaped opening B is formed in the upper wall portion, which is offset to one edge. ing. The speaker 6 is attached to an upright mounting plate 10B. The muffling unit 1B having such a configuration
However, it is clear that the same effect as that of the above-mentioned embodiment can be obtained.

In the closed casing 1C shown in FIG. 7, the upper wall portion has an R shape, and a slit-shaped opening 2C is formed at the top portion of the closed casing 1C. It is installed. Note that in the closed casing 1C of FIG. 7, the speaker 6 exactly faces the slit-shaped opening 2C, but in the present invention, the speaker 6 also faces the slit-shaped opening as shown in FIGS. 5 and 6. It is defined as something to do. Finally, in the closed casing 1D of FIG. 8, the cross section is bottle-shaped, but a slit-shaped opening 2D is formed at the top thereof, and the speaker 6 is attached to the attachment plate 10D that is installed to face this. There is. Next, FIGS. 9 to 12 show modified examples of the arrangement configuration of the partition plate 8. However, in FIG. 9, when the partition plate is not provided, in FIG. 10, the partition plate 8 ′ has three closed casings 1F. Figure 1 shows the case of equal division.
In one closed casing 1G, the inner space is divided into four equal parts by three parallel partition plates 8. In order to propagate sound waves evenly to these four sound paths, two are arranged in the illustrated manner. Speaker 6 is provided. In the closed casing 1H of FIG. 12, the inner space is equally divided into two by one partition plate 8 ″ extending from the upper wall portion to the lower wall portion, and the speaker 6 is arranged in each of the two. This configuration is also conceivable when two units are combined into one casing.

The muffling unit S ₃ casing 10 of FIG.
In 0A, the cross section is a pentagon, but the inside is defined by two partition plates 80 as shown in the figure, and the speaker 6 is arranged at the center position in the radial direction. Therefore, the sound deadening sound waves are evenly propagated from the upper wall surface, the inclined wall surface, and the side wall surface as indicated by arrows.

In the muffling unit S ₄ of FIG. 15, the casing 100B has a quarter circular cross-sectional shape, the sound wave emitting surface is arcuate, and the inside is a partition plate 80 to evenly distribute the inner space. It is divided and the speaker 6 is arranged at the center thereof. Even in such a muffling unit S ₄ , the muffling sound wave can be evenly propagated from the opening of the arc-shaped side wall portion as indicated by an arrow.

FIG. 23 shows a modification 3'of the muffling signal generator 3, in which case a vibration detector 5'is attached to the movable part of the noise source 7 as noise detecting means. For example,
The noise source is attached to its trough T by a vibrating conveyor. In FIG. 23, an acceleration pickup 5 ′ is attached to the trough T as a vibration detector, and its output is supplied to the amplifier 52, and its analog output is digitally converted by the A / D converter 53, and further this digital output is supplied. Is converted into a sound wave signal necessary for silencing through a digital filter 54 having a function such as a phase shifter. This is supplied to the D / A converter 55, and the analog output is amplified by the amplifier 56 and supplied to the muffling speaker 6. As a result, the sound waves generated by the vibration of the trough T and the driving of the vibration exciter propagate to the outside through the opening 2 of the muffling unit S, and the noise to the outside can be avoided. The acceleration pickup 51 may be replaced with a speed pickup or a displacement pickup. The present invention can be applied to both low frequency and high frequency noise. Further, the height of the closed casing 1 of the muffling units S, S ₁ , S ₂ , S ₃ may be higher or lower than that of the noise source 7.

In the above embodiment, when the noise wavelength is relatively short, the muffling unit S having the slit-shaped elongated rectangular opening 2 in the upper wall of the casing 1 is used. The second embodiment is used when the wavelength is relatively long, for example, when the driving frequency of the above-mentioned vibrating drum 14 is further lowered and it is considered to be an extremely low frequency noise source.

A silencer used for such an ultra low frequency noise source will be described below with reference to FIGS. 24 and 25.

In this embodiment, the noise source 70 has a long shape as in the above embodiment, and the speaker boxes 73 are connected to each other as shown in FIG. 5 are installed. The speaker box 73 has a speaker 74 fixed in a rectangular casing like a known AV device, and these cones are directed outward. Between the noise source 70 and the speaker box 73, noise detection microphones 71 are arranged corresponding to the speaker boxes 73, respectively. That is, in this embodiment, five pieces are provided on both sides at equal intervals. or,
In order to ensure the muffling effect of the speaker box 73,
In order to obtain a predetermined height above the floor 76, it is placed on the support base 75. In addition, the microphone 71 is the same as that of the above-described embodiment (see FIG.
The output signal is supplied to the muffling signal generation device 72 similar to 3 ′) of 3 and the output of the device 72 is supplied to the drive coil of the speaker 74.

The second embodiment is constructed as described above,
Next, the operation will be described.

The ultra low frequency sound wave emitted from the noise source 70 has a very long wavelength, for example, several meters to several tens of meters. Therefore, the sound wave generated by the noise source 70 has the same amplitude and
The relative positional relationship of the speaker box 73 as a sound wave generator that generates sound waves having a phase difference of 180 degrees is not greatly restricted as compared with the case where the frequency of the noise source is relatively high. Unlike the sound deadening unit S, which is not provided with a slit-shaped opening, since the wavelength is long, it is possible to easily obtain a sound wave of a noise source and a sound wave that reverses the density. The operation of the muffling signal generator 72 is the same as that of the above-described embodiment, but even with such a rough arrangement, it is possible to effectively prevent noise from propagating outward.

FIG. 27 shows a modification of the arrangement of the speaker box 73 of the second embodiment when the noise source is the vibrating drum 14. These speaker boxes are placed on the floor below the drum body of the vibrating drum 14. 73 is provided, and the output from the muffling signal forming device 80 is supplied to the speaker 74.
Signals are supplied to this from the vibration detectors 171 fixed to the peripheral wall portions on the inlet side and the outlet side of the vibrating drum 14, respectively. In this example, the muffling deviation detecting microphone is not provided as in the second embodiment, but the muffling signal forming device 80 whose circuit diagram is shown in FIG. 26 is used.

That is, this circuit is an analog circuit,
The input signal from the vibration detector 171 is widened by the widening device 81, this phase is shifted by the phase shifter 82 so as to reverse the density of noise, and this output is driven by the loudspeaker 74 via the widening device 83. Supply to the department. When the noise has a single frequency, the phase shifter 82 is configured by such an analog circuit without using an expensive digital processing circuit and shifts the phase with a bandpass filter, a lowpass filter, a highpass filter, or the like. And the phases can be matched. Even if the noise consists of multiple frequencies, it can be configured with an analog circuit. In this case, if the phases are matched with a graphicizer that can raise or lower these multiple gains, a practically sufficient silencing effect can be obtained. be able to. Of course, this circuit 80 is also applicable to the device 72 of FIG.

FIG. 28 shows another modification of the arrangement. In this modification, a frame 84 is constructed around the vibrating drum 14, and a muffling signal forming device 80 is mounted thereon.
The signals from the respective vibration detectors 171 fixed to the peripheral wall portions on the inlet side and the outlet side of the vibrating drum 14 are supplied to the amplifier 81 in FIG. Further, in this modification, the speaker box 73 is mounted so as to be located above the upper wall portion of the frame body 84, that is, above the vibrating drum 14. Even with such an arrangement, it is possible to effectively prevent the extremely low frequency noise generated from the vibrating drum 14 from propagating outward. 27 and 28, the driving frequency of the vibrating drum 14 is lower than that in the above case.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the second embodiment, as the noise source 70 has a long shape, a plurality of speaker boxes 73 are arranged so as to be connected to each other along both long sides of the noise source 70. A smaller number of speaker boxes may be arranged at a certain interval without being connected to each other. For example, in FIG. 25, they may be arranged at intervals of one speaker box. That is, in this case, three pieces are arranged.

Alternatively, the speaker boxes 73 may be arranged only near both ends of the noise source 70. That is, four speaker boxes 73 are arranged as a whole. Even with this, if the wavelength of the ultrasonic wave is sufficiently long, the silencing effect can be sufficiently obtained. Furthermore, there is a method of replacing the vibration detector with a noise detection microphone or a displacement detector. In the case of a displacement detector, for example, the vibration drum 1
4, an object detecting element is provided below the main body at a predetermined distance, and a change in the distance between the main body and this element is measured.

[0044]

As described above, according to the sound deadening device of the present invention, it is possible to quickly take sound deadening measures regardless of the shape and size of the noise source.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a muffling unit according to an embodiment of the present invention in the context of a noise source.

FIG. 2 is a partially cutaway view of the muffling unit.

FIG. 3 is a perspective view showing an example in which a plurality of the muffling units are arranged with respect to a noise source.

FIG. 4 is a perspective view showing an arrangement example in which a plurality of the muffling units described above are arranged only along one long side portion.

FIG. 5 is a plan view showing an example in which the silencing unit is arranged on both sides of a long noise source.

FIG. 6 is a cross-sectional view showing a modified example of the closed casing.

FIG. 7 is a cross-sectional view showing another modified example of the closed casing.

FIG. 8 is a cross-sectional view showing another modified example of the closed casing.

FIG. 9 is a cross-sectional view showing another modified example of the closed casing.

FIG. 10 is a schematic front sectional view of a closed casing that does not use a partition plate.

FIG. 11 is a schematic front sectional view of a closed casing when two partition plates are used.

FIG. 12 is a schematic front cross-sectional view of a closed casing when three partition plates are used.

FIG. 13 is a schematic front cross-sectional view of a closed casing when one partition plate is used.

FIG. 14 is a schematic cross-sectional view of a casing when two partition plates are used.

FIG. 15 is a cross-sectional view showing a sound deadening unit having a ¼ circle cross section when one partition plate is used.

FIG. 16 is a side view of a conventional drum shaker.

FIG. 17 is a plan view of the same.

FIG. 18 is a schematic front view for explaining the operation of the drum shaker.

FIG. 19 is a schematic sectional view for explaining the same effect.

FIG. 20 is a cross-sectional view showing a noise prevention device for a conventional vibrating drum.

FIG. 21 is a front view of the same.

FIG. 22 is a block diagram of an ANC circuit in the same device.

FIG. 23 is a block diagram showing a modified example of the ANC circuit.

FIG. 24 is a front view of a silencer according to a second embodiment of the present invention.

FIG. 25 is a side view of the same.

FIG. 26 is a circuit diagram showing a modified example of the silence signal forming device.

FIG. 27 is a side view showing a modification of the arrangement of the second embodiment.

FIG. 28 is a side view showing another modification of the arrangement.

[Explanation of symbols]

1 Airtight casing 2 Slit-shaped opening 3 Noise reduction signal generator 5 Noise detection microphone 6 Speaker 7 Noise source 70 Noise source 71 Microphone 73 Speaker box 74 Speaker 80 Noise reduction signal forming device 171 Vibration detector S Noise reduction unit S ₁ Noise reduction unit S ₂ Noise reduction Unit S ₃ silencer unit

Claims (7)

[Claims] 1. A casing having an opening and provided with sound wave generating means for generating a silencing sound wave from the opening,
One or a plurality of muffling units including a noise detecting unit arranged near the noise source, and a muffling signal generating device for receiving the detection signal of the detecting unit and driving the sound wave generating unit. A sound deadening device, which is arranged close to or around this. 2. The silencer according to claim 1, wherein the inside of the casing is partitioned by one or a plurality of partition walls. 3. The muffler according to claim 1, further comprising a muffling deviation detecting microphone provided near the opening of the casing, and the detection signal is supplied to the muffling signal generating device. 4. A muffling unit provided with a sound wave generating means, a noise detecting means, and a muffling signal generating device for receiving the detection signal of at least the detecting means and driving the sound wave generating means, in the vicinity of the noise source. , Or a plurality of silencers are provided. 5. The muffling unit is above the noise source,
Alternatively, the silencer according to claim 4, which is disposed below. 6. The noise reduction device according to claim 4, wherein the noise sources have a longitudinal shape, and the noise reduction units are arranged along both long sides of the noise source and close to them. 7. The silencer according to claim 1, wherein the silencer signal generator is an analog circuit including a phase shifter.