JPH11336525A - Silencing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the S/N ratio in an environment where a pulsated pressure variation exists, by preventing chattering of a protection film resulting from pulsated pressure variation. SOLUTION: The vibratory surface of a protection film 35 to partition a noise sensor 2 installed inside a lead-in pipe 33 from the inner space 32 of a sound absorbing duct 31 is pinched in sandwich form by a pair of damping members 36A and 36B so that the fundamental vibration of the protection film 35 is maintained, and thereby distortion of a transmitted sound is precluded. The inner space on the side with a sound receiving hole 40a of the lead-in pipe 33 partitioned by the protection film 35 is filled with a filter 41 formed from metal wool so as to remove carbon from the exhaust gas, and thereby stable noise sensing is made practicable for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a noise reduction device using an active noise control (ANC) technology, and more particularly, to a noise detector or a noise reduction deviation detector in an ANC noise reduction device.

[0002]

2. Description of the Related Art Active noise control (A)
As is well known, a noise suppressor using the NC) technology introduces a sound-absorbing sound wave having the same magnitude and opposite phase as the noise toward the internal space of the sound-absorbing duct through which the noise propagates, and the noise sound wave and the sound-absorbing sound are eliminated. The noise-reducing effect is obtained by the interference effect with the use sound wave.

FIG. 10 shows a general configuration of this type of silencer, in which a sound absorbing duct 1 for introducing the noise P, a noise detector 2 for detecting the noise P, and a sound wave for generating a sound absorbing sound wave. It has a speaker 3 as a generator and a silencing deviation detector 4 for detecting a silencing deviation. The speaker 3 is driven by a silencing signal y calculated by the silencing signal generator 5 based on the outputs x and e of the noise detector 2 and the silencing deviation detector 4. The silencing signal generator 5 will be described.
The output x of the noise detector 2 is an amplifier 6, an A / D converter 7
To an adaptive filter (hereinafter abbreviated as ADF) 8 and a delay filter 9. ADF
8 has N taps, the coefficients of which are updated by the output of the coefficient calculator 10. The delay filter 9 has an acoustic transfer characteristic corresponding to a path from the speaker 3 to the silencing deviation detector 4. That is, the coefficient of the delay filter 9 is determined in consideration of the time delay, and is measured or identified in advance. The output e of the silencing deviation detector 4 is supplied to the amplifier 11, the A / D converter 1
2 is supplied to the coefficient calculator 10. Coefficient calculator 1
0 is an adaptive algorithm for sequentially calculating the optimum coefficient to be given to the ADF 8. The muffling signal y calculated by the ADF 8 is supplied to the speaker 3 via the D / A converter 13 and the amplifier 14, and the muffling sound having the same magnitude as that of the noise P and having the opposite phase enters the sound absorbing duct 1. Generated towards. Then, the muffling signal y is adjusted so that the muffling deviation becomes zero at the position of the muffling deviation detector 4. The muffling signal generating device 5 has a configuration using the above-described well-known ANC technology.

[0004] Apart from noise, when the ANC silencer is applied to a noise source (for example, an engine) that emits high-temperature exhaust gas containing corrosive gas such as acid or alkali, the above-described conventional configuration has a problem in that Detector 2 and silencing deviation detector 4
However, there is a problem that the sound is damaged by heat or corrosive gas, and the original sound receiving performance cannot be maintained. Therefore, as shown in FIG. 11, the noise detector 2 (or the noise elimination deviation detector 4. Hereinafter) is provided inside the introduction pipe 22 communicating with the internal space 1 </ b> A of the sound absorbing duct 1 via the sound receiving port 20 by the vibration proof support member 17. , And the like.), And the first and second sections that define the noise detector 2 and the internal space 1A of the sound absorbing duct 1.
The second protective films 18 and 19 are provided, and heat and acid of exhaust gas,
A technique for protecting the noise detector 2 from alkali components has been proposed (for example, Japanese Patent Application No. 10-17835). Here, the first film 18 is formed of a material having heat resistance but not completely airtight (for example, glass cloth, carbon cloth, silica cloth, ceramic paper, etc.), and the second film 19 has no heat resistance. It is formed of a material having perfect airtightness (for example, fluorine resin (PTFE, FEP, ETFE, PFA), polyimide, polypropylene, polyethylene terephthalate, etc.).

[0005]

However, in the conventional configuration using the above-described protective film, there is a problem that the protective film sticks due to the pulsating pressure fluctuation of noise, and the transmitted sound is distorted. That is, the protective films 18, 1
9 has a very small bending stiffness, the amplitude limit is exceeded by a slight pulse pressure fluctuation, whereby noise cannot be transmitted faithfully and S / N
Is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides a silencer capable of preventing the protective film from sticking due to pulse pressure fluctuation and improving S / N in an environment where pulsating pressure fluctuation exists. The task is to

[0007]

The object of the present invention is to provide a noise detector for detecting noise of a noise source, a sound absorbing duct for introducing the noise, a noise reduction deviation detector for detecting a noise reduction deviation, and the noise detector. And an output of the silencing deviation detector, and a silencing signal generating device for forming a silencing signal for generating a sound wave having the same magnitude as the noise and having the opposite phase from the sound wave generator, and the sound absorbing duct. The noise detector or the silencing deviation detector is arranged inside the introduction pipe communicating with the internal space through the sound receiving port, and the internal space of the noise detector or the silencing deviation detector and the sound absorbing duct. And a vibrating surface of the protective film is sandwiched by a pair of damping members.

According to the present invention, the vibration surface of the protective film is sandwiched between a pair of damping members to maintain the fundamental vibration of the protective film and transmit sound waves without distortion even in an environment where pulsating pressure fluctuations exist. Thus, a reduction in S / N is prevented.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In each of the following embodiments, a noise detector that detects noise from a noise source will be described. However, a similar configuration can be applied to a noise reduction deviation detector that detects a noise reduction deviation.

FIG. 1 shows a first embodiment of the present invention. The noise detector 2 includes an internal space 3 of the sound absorbing duct 31.
2 is located near the closed end of the introduction pipe 33. The introduction pipe 33 includes an introduction part 34A formed on a side wall part of the sound absorbing duct 31, a cylindrical cooling part 34B, and a lid part 34C in which the noise detector 2 is housed. And are integrally fixed by such fastening means. The periphery of the protective film 35 is held between the introduction part 34A and the cooling part 34B via a pair of holding members 37A and 37B made of a heat insulating material. The vibrating surface of the protective film 35 has a pair of damping members 36A and 36A.
B sandwiches the exhaust gas, and exhaust gas is completely shut off here. In the present embodiment, the protective film 35 is made of a material that is completely airtight and has excellent chemical resistance, for example, a fluororesin such as polytetrafluoroethylene (PTFE) known under the trademark of Teflon, polyimide, mica, or the like. Have been. Damping members 36A, 36B
A soft and small specific gravity material that does not affect the sound transmission of the protective film 35, such as glass wool, ceramic wool, rock wool, and a cloth material woven from various fibers, is used. The vibration surface of the protective film 35 has a sufficient area so as not to affect sound transmission (to have sufficiently small bending rigidity).

The introduction portion 34A and the internal space 32 of the sound absorbing duct 31 are connected to the sound receiving port 4 formed in the sound receiving port forming member 40.
0a. In addition, the metal wool (st
The filter 41 is made of e.g. The filter 41 is formed of a material having excellent heat resistance and chemical resistance, such as stainless steel, and mainly performs a filtering function of carbon contained in exhaust gas. Stainless steel wool is acoustically transparent, generates almost no abnormal noise due to its own vibration, and has the effect of slightly buffering pulsating pressure fluctuations. The net 42 prevents the damping member 36B from being out of shape.
In the other damping member 36A, the filter 41
Supported by

In the present embodiment, the introduction pipe 3 is set so that the resonance frequencies of all acoustic systems are equal to or higher than the upper limit of the silencing band.
3 inside size is set. The major resonance system comprising at issue here, there are two Helmholtz resonance system and the air column resonance system, of which the Helmholtz resonance system is introduced with the air mass of the sound receiving opening 40a which is determined by the length L ₄ and the aperture diameter D ₂ Part 34
A first resonance system determined by the air volume inside A, L ₄ and D
₂ , there is a second resonance system determined by the sum of the air mass of the sound receiving port 40a, the air volume of the introduction portion 34A, and the air volume of the cooling portion 34B (including the air volume of 34C). Is a third resonance system determined by the length L ₁ from the sound receiving port 40 a to the coating 35, a fourth resonance system determined by the length L ₂ from the coating 35 to the bottom inside the introduction pipe 33, and L ₁ + L. There is a fifth resonance system determined by ₂ . At this time, the dimensions of each part of the introduction pipe 33 are determined so that the primary resonance frequencies of all of the first to fifth resonance systems are higher than the upper limit of the silencing band. Further, the cross-sectional area expanding portion extending from the inner diameter D ₁ to diameter D ₃ of the vibration surface of the film 35 of the inlet section 34A (or the cooling part 34B), so-called expansion silencer is formed,
Also in this case, the length L ₃ of the expanded portion is determined so that there is no influence of resonance.

When the protective film 35 is made of PTFE,
Although the heat-resistant limit temperature is about 260 ° C., in the present embodiment, the distance from the sound receiving port 40 a to the protective film 35 is determined so that the surface temperature of the protective film 35 is 260 ° C. or less. At this time, one of the damping members 36A located on the sound receiving port 40a side can also serve as heat insulation,
In this case, the surface temperature can be adjusted also by the thickness of the damping member 36A. Furthermore, if the temperature of the internal space of the introduction portion 34A is adjusted to be always 100 ° C. or higher, it is possible to prevent aggregation of water in the internal space.

Cooling fins 43A and 43B are formed in the introduction section 34A and the cooling section 34B, respectively. The cooling fins 43A and 43B dissipate the heat propagating through the outer wall of the introduction pipe 33, and the temperature of the sound receiving section where the noise detector 2 is located. The rise has been suppressed. Further, a sealing member 38 is sandwiched between the cooling unit 34B and the lid 34C, so that the lid 34C is arranged from the cooling unit 34B side.
It suppresses vibration propagation to the side and prevents intrusion of sound from outside. The noise detector 2 is located near the closed end of the introduction pipe 33,
That is, it is supported by the anti-vibration support member 39 in the lid 34C. Since the sound wave propagating inside the cooling unit 34B has a large sound pressure, a sound pressure attenuator may be provided at the sound wave input port of the noise detector 2.

This embodiment is configured as described above, and the operation will be described next.

The noise P flowing upward from the lower part of the drawing in the interior space 32 of the sound absorbing duct 31 is accompanied by high-temperature exhaust gas, and is introduced into the introduction part 34A of the introduction pipe 33 through the sound receiving port 40a. When the exhaust gas flows through the filter 41 made of metal wool, the exhaust gas is subjected to the filtering action of the carbon contained therein. Here, conventionally, the solid deposition of the carbon causes clogging of the conventional filter made of a porous material, impairs the acoustic characteristics of the protective film, and further blocks the sound receiving port 40a. Although there is a defect, according to the present embodiment, the metal wool 41 itself vibrates due to the pulse pressure and performs an action of powdering the attached carbon, so that the above defect does not cause a problem. In other words, pulsating pressure fluctuations, which are originally harmful, are used in reverse. The powdered carbon has a low specific gravity and does not impair the sound transmission performance at all. In addition, since the carbon powder is held in the gap between the stainless steel wool 41, a heat insulating effect and a damping effect are generated, the temperature rise of the protective film 35 is reduced, and a slight noise that can be generated from the stainless steel wool itself is generated. Prevent occurrence.

The noise P reaches the inside of the cooling section 34B by vibrating the protective film 35 according to the amplitude and frequency thereof, and is detected by the noise detector 2. At this time, even if a pulsating pressure fluctuation occurs, the protective film 35 can maintain the basic vibration and transmit the noise P without distortion by the damping action of the damping members 36A and 36B, thereby preventing the deterioration of the S / N. You. Here, since the primary resonance frequencies of the above-described first to fifth resonance systems inside the introduction pipe 33 are set to be higher than the upper limit of the silencing band, a flat sound receiving characteristic can be obtained within the silencing band. it can. The output signal x of the noise detector 2 is supplied to a muffling signal generator (not shown), and is used for forming a muffling signal to be supplied to a speaker serving as a sound wave generator (not shown) as in the related art, without detailed description. You.

The heat introduced into the introduction pipe 33 together with the noise P is generated by a holding member 37A holding the peripheral portion of the protective film 35,
Due to the heat insulation function of 37B, propagation to the cooling section 34B side is suppressed, and heat is radiated from the cooling fins 43A, 43B to the outside air, so that the temperature rise of the sound receiving section where the noise detector 2 is located is prevented, and noise detection is performed. The durability of the container 2 can be improved. Here, the cooling section 34B may be made of either a metal material or a heat insulating material. That is, if the cooling unit 34B is made of a metal material, it is possible to radiate heat propagating in the internal space of the cooling unit 34B, while if the cooling unit 34B is made of a heat insulating material, the cooling unit 34B can be moved from the introduction unit 34A to the lid 34C. Heat propagation can be suppressed.

As described in detail above, according to the present embodiment, even in an environment where there is a pulsating pressure fluctuation, the sound wave can be transmitted without distortion by the protective film 35 sandwiched between the damping members 36A and 36B. Therefore, it is possible to prevent a reduction in S / N. In addition, it is not necessary to use a material having a high heat-resistant temperature for the protective film 35, and the noise detector 2 can be effectively protected from heat to improve durability. Further, the protective film 35 or the noise detector 2 can be protected from carbon contained in the exhaust gas to prevent deterioration of sound wave transmission performance or sound reception performance. Furthermore, since a material having perfect airtightness is used for the protective film 35, moisture does not aggregate inside the introduction pipe 33 (especially, the cooling section 34B), and the region is also included inside the introduction section 34A. By adjusting the temperature as described above, the aggregation of water can be prevented, and the corrosion of the inner wall surface of the introduction pipe 33 due to the water and the damage due to the adhesion of the water to the noise detector 2 can be prevented.

FIG. 2 shows a second embodiment of the present invention. In the drawings, the same reference numerals are given to portions corresponding to the above-described first embodiment, and a detailed description thereof will be omitted.

That is, the present embodiment is configured on the assumption that it is used in a relatively high temperature environment.
Insulating materials 45A and 45B are arranged in the internal space of 4A and the internal space of cooling unit 34B, respectively. As the heat insulating materials 45A and 45B, for example, the same material as the damping members 36A and 36B, that is, glass wool, ceramic wool, rock wool, or the like is used. Thus, the noise detector 2 can be protected from heat even in a high-temperature environment, while obtaining the same effects as those of the first embodiment.

FIG. 3 shows a third embodiment of the present invention. In the drawings, parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

That is, the present embodiment is based on the premise that it is used in a relatively low-temperature environment, and the cooling unit 34B used in the first and second embodiments is omitted. The cover 34C is attached directly to the introduction section 34A via the sealing member 38 to form the introduction pipe 33 '. According to the present embodiment, since the noise detector 2 is protected from the heat without providing the cooling unit 34B, the introduction pipe 33 'is provided.
Can be made shorter than the first and second embodiments.

FIG. 4 shows a fourth embodiment of the present invention. In the drawings, parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

In the present embodiment, the configuration is such that the carbon contained in the exhaust gas is prevented from being introduced into the introduction pipe 33 as much as possible. It is an alternative to the filter 41. That is, the above-mentioned heat insulating effect and damping effect can be obtained to the extent that an appropriate amount of carbon is retained in the filter 41, but if this carbon is excessively accumulated, it affects the sound transmission, The sound receiving performance of the noise detector 2 may be impaired. Therefore, a throttle passage 51a having a reduced flow path area is formed inside the sound absorbing duct 51, the sound receiving port 40a of the sound wave is arranged near the outlet of the throttle passage 51a, and the introduction portion 34A of the introduction pipe 33 is A suction hole 48 communicating with the outside is formed on the wall surface, and a pressure difference is generated between the inlet side and the outlet side of the throttle passage 51 a inside the sound absorbing duct 51 (inlet side> outlet side). , The outside air is introduced into the sound absorbing duct 51 as shown by an arrow F. As a result, the exhaust gas becomes
0a, so that noise P accompanying exhaust gas
Can be stably detected over a long period without deteriorating the S / N. Further, according to the present embodiment, the filter made of metal wool is not always necessary, but when the flow rate of the exhaust gas flow is low such as when the engine is stopped, the exhaust gas may enter the inside of the sound receiving port 40a. If the above filter is provided, there is no problem at all. The throttle passage 51a in the present embodiment is provided with a reduced diameter portion in the middle of the pipe of the sound absorbing duct 51, but may be configured as described later.

FIG. 5 shows a fifth embodiment of the present invention. In the drawings, parts corresponding to those in the above-described fourth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

That is, in this embodiment, the throttle passage 53
Is formed as a separate member from the sound absorbing duct 31, and is formed in a cone shape in which the flow path area decreases toward the downstream side of the sound absorbing duct 31. According to this configuration, the throttle passage 5 is also provided.
3, the flow rate of the exhaust gas on the outlet side is made larger than that on the outlet side to generate a pressure difference (inlet side> outlet side), whereby the same effect as in the above-described fourth embodiment can be obtained. . Although not shown, the sound absorbing duct 31 and the throttle passage 53 are integrated by a fastening means such as a bolt.

FIG. 6 shows a sixth embodiment of the present invention. In the drawings, parts corresponding to those in the above-described fourth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the noise P propagating in the sound absorbing duct 51 is introduced into the introduction pipe 33 through the probe pipe 60. One end 60b of the probe tube 60 is opened inside the introduction tube 33, and the other end 60a is connected to the throttle passage 51.
The sound receiving port is located near the outlet of a and opened toward the downstream side of the sound absorbing duct 51. This allows the outside air sucked from the suction hole 48 to be introduced into the sound absorbing duct 51 through the probe tube 60 by utilizing the pressure difference generated when the exhaust gas (noise P) flows through the throttle passage 51a. Exhaust gas can be prevented from entering the inside of the introduction pipe 33 as in the above-described fourth and fifth embodiments.
Further, according to this embodiment, even when the flow of the exhaust gas is small as compared with the above-described fourth and fifth embodiments, the inflow of carbon into the introduction pipe 33 is reduced. There is no problem even if the filter made of the product is omitted.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these embodiments.
Various modifications are possible based on the technical idea of the present invention.

For example, in each of the embodiments described above, the distortion of transmitted sound is prevented by sandwiching the protective film 35 between the damping members 36A and 36B. Therefore, it is desirable to determine the opening area of the sound receiving port 40a and the total length of the introduction portion 34A so as not to exceed the amplitude limit. However, in this case, the introduction part 34 is reduced by the reduced input sound pressure level of the noise P.
Note that noise in A becomes relatively large.

In the first to third embodiments, the sound receiving port 40a is provided at the axial center of the introduction portion 34A.
With this configuration, the carbon accumulated at the bottom in the introduction portion 34A cannot be discharged to the outside. Therefore, as shown in FIGS. 7 and 8, if the sound receiving port forming member 55 is formed so that the sound receiving port 55a is located below the axial center of the introduction portion 34A, the sound absorbing duct 55a is provided with carbon from the sound receiving port 55a. Since it can be discharged into the inside 31, the amount of accumulated carbon can be reduced. Also, simply set the sound receiving port to the sound absorbing duct 3
If it is arranged above the one axis, carbon accumulated by the action of gravity can be easily discharged into the sound absorbing duct 31.

In each of the above embodiments, the noise detector 2 is connected to the cover 34 of the introduction pipe 33 via the vibration isolating support member 39.
Although the noise detector 2 is supported in C, as shown in FIG. 9, the noise detector 2 may be supported in a state of being suspended in a gel-like anti-vibration rubber. In this case, the noise detector 2
Can be arranged in the introduction pipe 33 together with the wiring board 62, and only the sound receiving portion of the noise detector 2
2, the sound can be detected without being affected by the acoustic characteristics in the cover 34C, and the S / N can be further improved. In addition, the noise detector 2 floats in the vibration isolating rubber.
, The absorptivity of the vibration propagating through the introduction pipe 33 is increased, and the S / N is improved. In the drawing, reference numeral 64 denotes a connector for connection to external wiring.

Further, in each of the embodiments described above, the noise detector 2 has been described. However, as described above, the noise detector 2 can also be applied to the silencing deviation detector 4.

[0035]

As described above, according to the muffler of the present invention, since the vibration surface of the protective film is sandwiched by the pair of damping members, the protective film can be protected even in an environment where pulsating pressure fluctuations exist. Can be transmitted without distortion while maintaining the fundamental vibration of the above, thereby preventing a reduction in S / N.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 3 is a sectional view of a main part showing a third embodiment of the present invention.

FIG. 4 is a sectional view of a main part showing a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a main part showing a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a main part showing a sixth embodiment of the present invention.

FIG. 7 is a side sectional view of a main part showing a modification of the configuration of the sound receiving port.

FIG. 8 is a front view of the same.

FIG. 9 is a cross-sectional view of a main part showing a modified example of a support mechanism of the noise detector and / or the silencing deviation detector.

FIG. 10 is a configuration diagram illustrating an example of a conventional silencer.

FIG. 11 is a cross-sectional view of a main part showing an example of an arrangement configuration of a noise detector according to another related art.

[Explanation of symbols]

 Reference Signs List 31 sound absorbing duct 32 internal space 33 introduction pipe 35 protective film 36A damping member 36B damping member 40a sound receiving port 41 filter made of metal wool 45A heat insulating material 45B heat insulating material 48 suction hole 51a throttle path 53 throttle path 56 sound receiving port 60 probe pipe 60a Sound receiving port 63 Anti-vibration rubber

Claims (9)

[Claims] A noise detector for detecting noise of a noise source;
A sound absorbing duct for introducing the noise, a silencing deviation detector for detecting a silencing deviation, receiving outputs of the noise detector and the silencing deviation detector, and generating a sound wave having the same magnitude as the noise and having an opposite phase. A muffling signal generating device for forming a muffling signal for generating from a sound wave generator, and inside the introduction pipe communicating with the internal space of the sound absorbing duct via a sound receiving port,
A noise elimination device provided with the noise detector or the noise elimination deviation detector and a protective film for partitioning the noise detector or the noise elimination deviation detector and the internal space of the sound absorbing duct; A silencer characterized in that the surface is sandwiched between a pair of damping members. 2. The muffler according to claim 1, wherein a filter made of metal wool is filled in an inner space on the sound receiving port side of the introduction pipe defined by the protective film. 3. The muffler according to claim 1, wherein the size of the inside of the introduction pipe is set such that the resonance frequencies of all the acoustic systems are equal to or higher than a high-frequency limit of a muffling band. 4. A distance from the sound receiving port to the protective film such that a surface temperature of the protective film facing the internal space on the sound receiving port side of the introduction pipe is equal to or lower than a heat-resistant limit temperature of the protective film. 3. The muffler according to claim 2, wherein: 5. The method according to claim 1, wherein at least the damping member located on the sound receiving port side is made of a heat insulating material, and a maximum surface temperature of the protective film is adjusted by adjusting a thickness of the damping member. Item 5. The noise reduction device according to Item 4. 6. A heat insulating material is disposed in each of the internal spaces on the sound receiving port side of the introduction pipe and the closed end side of the introduction pipe, which are defined by the protective film.
The silencing device according to any one of the above. 7. A throttle passage is formed inside the sound absorbing duct, the sound receiving port is arranged near an outlet of the throttle passage, and communicates with the outside in the sound receiving port side internal space of the introduction pipe. 7. The muffler according to claim 1, wherein a suction hole is formed. 8. The muffler according to claim 7, wherein the sound receiving port is formed at the other end of the probe tube having one end opening inside the introduction tube and opening toward the downstream side of the sound absorbing duct. . 9. The apparatus according to claim 1, wherein the noise detector or the silencing deviation detector is supported at a closed end of the introduction pipe in a state of being suspended in a vibration isolating rubber. Silencer.