JPH10319973A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the muffler in which the device reliability is secured. SOLUTION: A sound wave generating means is constituted of plural speakers 6a to 6d. Each of the speakers 6a to 6d is provided with an air flow amount detector 32, which detects the amount of air flow caused by the driving of the speaker, a temperature detector 56 and a current detector 55. By comparing the outputs of the detectors 32, 56 and 55 against reference values, an abnormal condition of each speaker is detected. If an abnormal condition is detected for any one of the speakers, the output command of a power amplifier 3a is shut off, the driving of the speaker is stopped and a display 66 is turned on to notify the abnormal condition to the external. Thus, even though any one of the speakers 6a to 6d malfunctions, other normal speakers make up for it, the overall muffling effect is maintained, the malfunctioned speaker is surely detected and the maintenability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a muffler using active noise control (ANC) technology.

[0002]

2. Description of the Related Art FIG. 10 shows a configuration of a conventional silencer. The noise detector 38 detects noise P, the noise detector 38 detects noise reduction deviation, and the output x of these noise detectors 38 and the noise reduction detector. Receiving the output e of 35,
Generation of a muffling signal y for generating a muffling signal y for generating a sound wave having the same magnitude as the noise P and having the opposite phase (hereinafter referred to as muffling sound wave) from the speaker 36 as sound wave generation means toward the sound absorbing duct 1. And an apparatus 14. It is assumed that the noise source is located on the left side of the figure, not shown, and that the distance between the noise detecting means 38 and the speaker 36 and the distance between the speaker 36 and the noise reduction deviation detecting means are as follows.
Actually, it is assumed to be larger than shown.

The output x of the noise detector 38 is an amplifier 39, A
An adaptive filter (hereinafter abbreviated as ADF) 41 and a delay filter 4 via a / D converter 40
2 is supplied. The output e of the silencing deviation detector 35 is supplied to the coefficient calculator 43 via the amplifier 46 and the A / D converter 47. ADF 41 has N taps,
These coefficients are updated by the output of the coefficient calculator 43. Further, the delay filter 42 has an acoustic transfer characteristic corresponding to a path from the speaker 36 to the muffling deviation detector 35. That is, the coefficient of the delay filter 42 is determined in consideration of the time delay, and is measured or identified in advance. Further, the coefficient calculator 43 is an adaptive algorithm for sequentially calculating the optimum coefficient given to the ADF 41. The muffling signal generator 14 has a configuration using the above-described well-known ANC control technology.

[0004] With the above-described configuration of the conventional silencer, the level of the noise P emitted from the discharge end of the sound absorbing duct 1 is greatly reduced or made zero.
Further, the silencer having the above-described configuration is applied to a device that uses a blower, a generator, an engine, or the like as a noise source.

[0005]

[0005] In recent years, ANC
Ensuring the reliability of a silencer using technology has become an important issue. However, the configuration of the conventional silencer described above has a problem that if any one of the noise detector 38, the silence deviation detector 35, and the speaker 36 breaks down or is broken, the entire device does not function at all. is there. In particular, if the noise source is an engine, high-temperature exhaust gas is also emitted.
It is inevitable that the noise deviation detector 35 or the speaker 36 is greatly affected. Therefore, the noise detector 38
And other devices are easily broken or damaged.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a muffler capable of ensuring the reliability of the apparatus.

[0007]

SUMMARY OF THE INVENTION The above-mentioned problems are attained by a noise detecting means for detecting noise from a noise source (for example, corresponding to a reference symbol P in the embodiment, the same applies hereinafter), and a silencer for detecting a silencing deviation. Deviation detection means, an output (x ') of the noise detection means and an output (e') of the noise reduction deviation detection means
And a noise reduction signal generating device (m) for generating a noise reduction signal (y) for generating a sound wave having the same magnitude and opposite phase as the noise (P) from the sound wave generating means toward the sound absorbing duct (1). 17), the sound wave generating means comprises a plurality of sound wave generators (6a, 6b, 6c, 6).
d) and the plurality of sound wave generators (6
a, 6b, 6c, 6d) at least a temperature detector (55) for detecting the temperature of the sound wave generator (6a, 6b, 6c, 6d) and / or the sound wave generator (6a,
6b, 6c, 6d) provided with an air flow detector (56) for detecting an air flow generated by driving the sound wave generator by an output of any one of the temperature detector (55) and the air flow detector (56). When the abnormality of (6a, 6b, 6c, 6d) is detected, the supply of the current for the muffling signal to the sound wave generator is cut off.

According to the first aspect of the present invention, the sound wave generating means is constituted by a plurality of sound wave generators (6a, 6b, 6c, 6d). Desired silencing effect can be secured.
At the same time, by detecting the abnormal sound wave generator and interrupting the supply of the silencing signal current (y) to the sound wave generator,
It is possible to prevent the sound deadening effect from being disturbed by the abnormally operating sound wave generator. The abnormality detection can be performed by the output of the temperature detector (55) and / or the air volume detector (56) provided in each of the sound wave generators (6a, 6b, 6c, 6d).

[0009] The above-mentioned problems also include a noise detection means for detecting noise (P) of a noise source, a noise reduction deviation detection means for detecting a noise reduction deviation, an output (x ') of the noise detection means, and a detection of the noise reduction deviation. Upon receiving the output (e ') of the means, a sound-absorbing signal (y) for generating sound waves having the same magnitude and opposite phase as the noise (P) from the sound wave generating means toward the sound absorbing duct (1). The noise detection means and / or the noise reduction deviation detection means comprises a plurality of noise detectors (8a, 8).
b, 8c, 8d) and / or a plurality of silencing deviation detectors (5
a, 5b, 5c, 5d), and the noise detector (8a, 8b, 8c, 8d) and / or the noise reduction deviation detector (8a, 8b, 8c, 8d) based on the sound receiving state of the test signal (Vt) emitted from the sound wave generator. 5a, 5b, 5c, and 5d), and when the abnormal noise detector and / or the silencing deviation detector is detected, the muffling signal is output from the noise detector and / or the silencing deviation detector. The problem is solved by a silencer characterized in that an output supply to the generator is cut off.

According to a sixth aspect of the present invention, for example, the noise detecting means and the silencing deviation detecting means are respectively replaced by a plurality of noise detectors (8a, 8b, 8c, 8d) and the silencing deviation detector (5).
a, 5b, 5c, and 5d), even if one of them fails, the other can make up for it, so that the noise reduction effect is not impaired. Therefore, when an abnormal noise detector and / or silencing deviation detector is detected, the output supply from the noise detector and / or the silencing deviation detector to the muffling signal generator is cut off.

[0011]

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

FIG. 1 shows a silencer according to a first embodiment of the present invention. Parts corresponding to those in FIG. 10 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The sound wave generating means, the noise detecting means, and the silencing deviation detecting means are respectively composed of four speakers 6 having the same configuration.
a, 6b, 6c, 6d, noise detectors 8a, 8b, 8c,
8d, and the silencing deviation detectors 5a, 5b, 5c and 5d. The outputs of the noise detectors 8a to 8d and the muffling deviation detectors 5a to 5d are supplied to operational amplifiers 4 and 2 in a muffling signal generator 17, and their average outputs x 'and e' are calculated. Then, based on these average outputs x ′ and e ′, the conventional silencing signal generator 14
A mute signal y is formed in the same manner as in FIG. 10 (see FIG. 10), and the speakers 6a to 6a
6d is driven.

FIG. 2 shows speakers 6a to 6a according to the present embodiment.
6d shows the abnormality detection circuit 20 of FIG. First, the configuration of the speakers 6a to 6d will be described with reference to FIG. 2, but since they have the same configuration, the configuration of only the speaker 6a will be representatively described.

A vibration plate 21 is accommodated in a frame 26 having a plurality of openings 26a formed in the side surface, and an edge 21a of the vibration plate 21 is fixed to an edge of the frame 26. The drive unit will be described. A back plate 2 is attached to a cylindrical bobbin 27 which is concentrically fixed to the lower end of the diaphragm 21 and has a voice coil 24 wound around the side periphery.
The pole piece 28 fixed integrally with the fitting 9 is loosely fitted. A permanent magnet 31 is fixed between the top plate 30 and the back plate 29 fixed to the bottom of the frame 26 at a predetermined interval concentrically with the pole piece 28. Thus, the diaphragm 21 vibrates in the vertical direction by receiving an alternating magnetic attraction generated by supplying the silencing signal current y to the voice coil 24 via the power amplifier 3a. At this time, the lower end of the diaphragm 21 is supported by a spider made of aramid fiber, carbon fiber, glass fiber, or the like disposed between the inner surface of the frame 26 and the bobbin 27, not shown.

The loudspeakers 6a to 6d according to the present embodiment each have an air volume detector 3 for detecting an air volume generated by driving the loudspeakers.
2 are provided. An annular mounting member 33 is disposed in alignment with a through hole 28a formed in the axis of the pole piece 28, and both ends are fixed to the inner wall surface of the mounting member 33 and are disposed in the diameter direction. And a strain detection line 34. The strain detection line 34 is deformed by receiving wind generated by driving the speaker 6a, and outputs a voltage generated according to the amount of deformation. On the back plate 29, a temperature detector 56 for detecting the temperature of the speaker 6a is provided.

Next, the abnormality detecting circuit 20 of the speaker 6a will be described. In the present embodiment, the abnormality of the speaker 6a is detected by the three detectors of the air volume detector 32, the temperature detector 56, and the current detector 55 described later. I try to detect.

The output of the air flow detector 32 is supplied to a comparator 57 via an amplifier 61. As shown in the figure, all the upward and downward cycles of the strain detection line 34 are positive voltage. Is output as Also, so that a mute signal y formed by the silencer signal generator 17 mute signal current y ₁ is supplied to a comparator 57 as a reference value s through the absolute value circuit 62 and the integrator 63. The silencing signal current y ₁ is inverted by the absolute value circuit 62 so that the negative output is also inverted to be a positive output, and the current is temporally integrated by the integrator 63 and the vibration corresponding to the air volume detected by the air volume detector 32. It is converted to the same dimension as the amplitude of the plate 21. Thereby so as to detect whether the speaker 6a is driven in response to the magnitude of the mute signal for the current y _1. If the output of the air volume detector 32 corresponds to the magnitude of this silencing signal current as a reference value s, the output of the comparator 57 is determined to be normal and the output of the comparator 57 is at a high level.
If the output does not correspond to the reference value s, the output is at a low level.

The output of the temperature detector 56 is supplied to a comparator 58 via an amplifier 60. If the output is lower than the reference temperature θ, the output of the comparator 58 is determined to be normal and the output of the comparator 58 is at a high level. Is higher than the reference value θ, the output of the comparator 58 is at a low level. Thus, the temperature detector 56 prevents the voice coil from being overheated and disconnected due to a failure of the power amplifier 3a or a rise in temperature around the speaker 6a.

Further, in the present embodiment, the current value of the silencing signal current y amplified by the power amplifier 3a is detected by the current detector 55, and it is determined by the comparator 59 whether or not this is amplified at a predetermined amplification rate. Compare and
If normal, the output of the comparator 59 is set to a high level.
When the output of the current detector 55 is abnormal, for example, when the current value is zero or not amplified at a predetermined amplification factor,
The output of the comparator 59 is set to a low level.

As described above, if the speaker 6a is detected to be normal based on all outputs of the air volume detector 32, the temperature detector 56, and the current detector 55, the comparator 5
AND gate 6 to which output terminals 7, 58 and 59 are connected
The output signal I ₁ from 4, whereas the speaker 6a is maintained desired amplifying effect of the power amplifier 3a continues to be driven, that these air volume, is abnormal even any one of the temperature or current value When it is detected, the output of the AND gate 64 becomes zero, the function of the power amplifier 3a is stopped (the current supply to the speaker 6a is cut off), and the display 66 made of, for example, a light emitting diode is turned on by the output of the NOT gate 65. Then, the abnormality of the speaker 6a is displayed outside. As a result, even if one of the four speakers fails, the desired muffling effect can be ensured by the remaining speakers, and at the same time, when an abnormal speaker is detected, the driving of the speaker is stopped. This can prevent disturbance of the muffling effect due to the generation of sound waves other than the predetermined muffling sound wave, and display an external message as to which speaker is abnormal. In addition, maintainability can be improved.

Although the abnormality detection system for the speaker 6a is constructed and operates as described above, the same applies to the other speakers 6b, 6c and 6d, and a description thereof will be omitted. Next, an abnormality detection system of the noise detectors 8a to 8d and the silencing deviation detectors 5a to 5d will be described with reference to FIGS. 3 to 6. In general, both the noise detector and the silencing deviation detector are constituted by microphones. Therefore, in the present embodiment, both of the microphones are detected with the same system configuration to detect abnormality of these microphones. Therefore, typically, the silencing deviation detectors 5a to 5d
Will be described.

Referring to FIG. 3 and FIG. 4, when detecting anomalies of the silencing deviation detectors 5a to 5d, the entire apparatus is set to a test mode and a test signal Vt (or any of them) is output from the speakers 6a to 6d (or any of them). For example, white noise) is generated. Outputs Vma, Vmb, Vmc (not shown) and Vmd of each of the silencing deviation detectors 5a to 5d receiving the test signal Vt are compared with comparators 77a, 77b, 77, respectively.
c (not shown) and 77d to compare with the true test signal Vt. If normal, the output O of each of the comparators 77a to 77d is compared.
₁ , O ₂ , O ₃ (not shown) and O ₄ go low, and if abnormal, go high and display 78
a, 78b, 78c (not shown) and 78d are turned on. The outputs O _{1 to} O ₄ of the comparators 77a to 77d are shown in FIG.
, Are supplied to knot gates 76a, 76b, 76c (not shown) and 76d. Knot gate 76a
The output terminals of .about.76d are switches 72a and 72, respectively.
b, 72c (not shown) and 72d,
The switches are output as ON / OFF commands for the switches 72a to 72d, respectively, and are closed when the output level is high (O
N), open (OFF) when low. That is, if the silencing deviation detectors 5a to 5d are normal, the switch 72a
To 72d are ON, and if abnormal, they are OFF.

FIG. 3 shows a state in which all the switches 72a to 72d are ON, whereby the outputs Vma to Vmd of the silencing deviation detectors 5a to 5d are supplied to a gain adjuster 75. At this time, the adders 73 and 7
The total sum of the respective outputs Vma to Vmd is supplied to the gain adjuster 75 by 4,. Note that the signal Vm is the output of the gain adjuster 75, and these silence deviation detectors 5a to 5d
In conjunction with the amplification factor (gain) of the operational amplifier 2 (see FIG. 1) that calculates the average output of the operational amplifier 2.

FIG. 5 shows the configuration of the gain adjuster 75, in which negative feedback is applied to the inverting amplifier 80 to adjust the gain (gain). That is, the gain is adjusted by the resistance R _{O of the} input circuit and the resistance R _N of the negative feedback circuit. Here, the resistance _RN is determined by the switch 82
a, 82b, 82c (not shown) and 82d and a resistor R
₁ , the resistance of the entire negative feedback circuit in which a series circuit of R ₂ , R ₃ (not shown) and R ₄ is connected in parallel. These switches 82a to 82d respectively correspond to the outputs O _{1 to} O of the comparators 77a to 77d described with reference to FIG.
₄ are connected to the output terminals of knot gates 81a, 81b, 81c (not shown) and 81d, and are turned on when the outputs of the knot gates 81a to 81d are at a high level.
It is configured to be OFF when at the low level.
Therefore, if the normal all four silencer deviation detector 5a to 5d, the comparator output O ₁ ~ O ₄ of 77a~77d
Is low, the outputs of the knot gates 81a to 81d are high, and the switches 82a to 82d are all in the ON state. At this time, if R ₁ = R ₂ = R ₃ = R ₄ = R, R _N = R / 4, and the amplification factor Af = R _N / R _O = R
/ Can be expressed as (4R _O).

Therefore, for example, four silencing deviation detectors 5a
When only 5a of ~5d is assumed to be abnormal, with reference to FIGS. 3 and 4, with only the output O ₁ of the comparator 77a is turned an indicator 78a at a high level, the output of the NOT gate 76a Becomes low level, and only the switch 72a is turned off. As a result, the sum of the outputs Vmb to Vmd of the remaining three normal silencing deviation detectors 5b to 5d is supplied to the gain adjuster 75. At this time, since there are only three normal silence deviation deviation detectors, when the average value is calculated by the operational amplifier 2 in the silence signal generator 17, the output level becomes small. This tendency becomes more pronounced as the number of normal detectors decreases. The gain adjuster 75
In order to improve this, the following operation is performed.

When only the silencing deviation detector 5a is abnormal, the negative feedback circuit in the gain adjuster 75
Output O ₁ of the comparator 77a and the output of the NOT gate 81a becomes a low level with that at a high level. As a result, the switch 82a is turned off. At this time, the resistance R
_{N = R / 3, Af =} R / (3R O) and becomes the amplification factor Af is automatically increased by a factor of 4/3 compared to when all four are normal, as a result, the output signal Vm It will not change. Similarly, when there are two or one normal silencing deviation detectors, the gain is steady gain × 2 or steady gain × 4 (see FIG. 6, where “microphone” indicates the silencing deviation detector). Represent). That is, the gain adjuster 75 automatically increases the gain based on the outputs O _{1 to} O ₄ of the comparators 77 a to 77 d even if the normal noise reduction deviation detector is reduced by the gain adjuster 75. Of the output signal Vm is adjusted so as not to change.

Therefore, according to the present embodiment, the silencing deviation detecting means is constituted by the four silencing deviation detectors 5a to 5d, so that even if any one of the detectors fails, the entire apparatus is not supported. The silencing effect can be maintained. At the same time, the overall gain can be adjusted to always produce an accurate silencing deviation output e ', and an abnormal detector can be displayed externally to facilitate its maintenance.

The abnormality detection system of the silencing deviation detectors 5a to 5d is configured and operates as described above, but the noise detectors 8a to 8d are also configured in exactly the same way, so that the description is omitted. .

FIGS. 7 and 8 show a second embodiment of the present invention. In the present embodiment, the speakers 6a to 6d
, A gain adjuster 85 for automatically adjusting the amplification factor of the silencing signal current y supplied to the remaining normal speaker when any of the abnormalities is detected. The abnormality detection circuit 20 corresponds to the abnormality detection circuit 20 of the speakers 6a to 6d shown in FIG.

Referring to FIG. 7, when the abnormality detection circuit 20 recognizes that the speakers 6a to 6d are normal as described above, the output signals I ₁ to I ₁ of the AND gate 64 (see FIG. 2) are output.
Supplies I ₄ to the power amplifier 3 a to 3 d, and to maintain the predetermined amplification effect. Referring to FIG. 8, gain adjuster 85
Has a configuration similar to that of the gain adjuster 75 for adjusting the detection gains of the silencing deviation detectors 5a to 5d described with reference to FIG. 5, and applies negative feedback to the inverting amplifier 90 to increase the gain (gain). To make adjustments. That is, the gain is adjusted by the resistance R ₀ ′ of the input circuit and the resistance R _N ′ of the negative feedback circuit. Wherein the resistance R _N ', the switches 92a, 92b, 92c (not shown) and 92d and the resistor _{R 1', R 2 ',} R 3' ( not shown) and parallel to each series circuit between the R ₄ ' Represents the resistance of the entire negative feedback circuit connected to. The switch 92a~92d is supplied the output signal I ₁ ~I ₄ from the abnormality detection circuit 20, which (when the speaker 6a~6d is normal) at a high level ON, configured to be OFF at a low level Have been.

According to the present embodiment, for example, the speaker 6
When the abnormality of the power amplifier 3a is detected, the amplification operation of the power amplifier 3a is stopped, the current supply to the speaker 6a is cut off, and the switch 92a in the gain adjuster 85 is turned off so that the resistance _RN 'of the negative feedback circuit is turned off. Is changed, thereby increasing the gain by a factor of 4/3. Thus, mute signal current y ₂ ~ supplied to the normal speaker 6b~6d residual
amplification factor of y ₃ is being increased would be supplied to the speaker 6b to 6d, it can always be a certain size muffling sound waves generated toward the sound absorbing duct 1 (see FIG. 1). Also in the present embodiment, as shown in FIG. 6, the gain is adjusted according to the number of speakers in which an abnormality is detected.

The abnormality detection system of the noise elimination deviation detectors 5a to 5d and the noise detectors 8a to 8d according to the present embodiment has the same configuration as that of the first embodiment. Detailed description is omitted.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the sound wave generating means, the noise detecting means, and the muffling deviation detecting means are constituted by four speakers 6a to 6d, noise detectors 8a to 8d, and muffling deviation detectors 5a to 5d, respectively. However, the number is not limited thereto, and the number may be further increased. Further, it is not necessary that the same number of speakers, noise detectors, and silencing deviation detectors be used, and they can be changed as appropriate.

The abnormality detecting circuit of the speakers 6a to 6d may be configured as shown in FIG. This is a configuration in which a mute signal current is supplied from one power amplifier 3 to four speakers 6a to 6d, and a shutoff device 50 that can cut off the current supply to each of the speakers 6a to 6d is provided between them. Provided. The shut-off device 50 includes the speakers 6a to 6d
Switches 51a, 51b, 51c, 51 corresponding to
d and dummy resistors 53a, 53b, 53c, 53d
It has. Then, sensors 52a, 52b, 52c, and 52 detect the driving state of each of the speakers 6a to 6d.
The output R is supplied to the abnormality detection circuit 53 and compared with the reference value S. As a result, the switch 51a for the speaker (for example, 6a) detected as abnormal is connected to the dummy resistor 53a. As shown, the current supply to the speaker 6a is cut off. Power amplifier 3
Therefore, the fluctuation of the load impedance viewed from the point of view can be minimized, and the performance of the power amplifier 3 can always be maximized. Even in this case, the same effect as described above can be obtained. In addition, the sensors 52a to 52d are the air volume detector 32 or the temperature detector 56 or the current detector 55 in the above-described embodiment.
May be configured.

[0037]

As described above, according to the muffler according to the first aspect of the present invention, the sound wave generating means is constituted by a plurality of sound wave generators. In this case, the current supply to the abnormal sound wave generator is interrupted, the remaining normal sound wave generators can maintain the silencing effect, and the reliability of the device can be ensured.

According to the silencer according to the sixth aspect of the present invention, the noise detecting means and / or the silencing deviation detecting means are constituted by a plurality of noise detectors and / or silencing deviation detectors. Even if this is the case, it is possible to reliably detect this and shut off the output from the abnormal noise detector or silencing deviation detector and maintain the silencing effect by the remaining normal noise detector and / or silencing deviation detector. And the reliability of the device can be ensured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a silencer according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a sound wave generator abnormality detection system according to the embodiment of the present invention.

FIG. 3 is a partial circuit diagram illustrating an example of an abnormality detection system of a noise detection unit (a silencing deviation detection unit) according to the embodiment of the present invention.

FIG. 4 is a circuit diagram showing another part of the embodiment.

FIG. 5 is a circuit diagram showing an example of a gain adjuster in FIG.

FIG. 6 is a diagram illustrating a relationship between a detection gain of a noise detection unit (a silencing deviation detecting unit) and a normal noise detector (a silencing deviation detector) according to an embodiment of the present invention.

FIG. 7 is a circuit diagram showing an example of a sound wave generator abnormality detection system according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram illustrating an example of a gain adjuster in FIG. 7;

FIG. 9 is a circuit diagram of a main part showing a modification of FIG. 2;

FIG. 10 is a circuit diagram showing a conventional silencer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sound absorption duct 5a Silence deviation detector 5b Silence deviation detector 5c Silence deviation detector 5d Silence deviation detector 6a Speaker 6b Speaker 6c Speaker 6d Speaker 8a Noise detector 8b Noise detector 8c Noise detector 8d Noise detector 17 Silence signal Generator 20 Speaker abnormality detection circuit 32 Airflow detector 34 Strain detection line 55 Current detector 56 Temperature detector 75 Gain adjuster 85 Gain adjuster 77a Comparator 77b Comparator 77d Comparator

Claims (9)

[Claims] A noise detection means for detecting noise of a noise source; a noise reduction deviation detecting means for detecting a noise reduction deviation; an output of the noise detection means and an output of the noise reduction deviation detection means; And a muffling signal generator that forms a muffling signal for generating sound waves of equal and opposite phases from the sound wave generator toward the inside of the sound absorbing duct, wherein the sound wave generator has a plurality of sound wave generators. Wherein each of the plurality of sound wave generators is provided with a temperature detector for detecting at least a temperature of the sound wave generator and / or an air flow amount detector for detecting a flow amount generated by driving the sound wave generator. When the abnormality of the sound wave generator is detected by the output of any one of the air conditioner and the air volume detector, the supply of the current for the muffling signal to the sound wave generator is cut off. Muffler being characterized in that as. 2. The air volume detector comprises a strain detection line provided below a center of a diaphragm of the sound wave generator and deformed by receiving wind generated by driving the sound wave generator. The noise reduction device according to claim 1, wherein a voltage generated according to the deformation is output. 3. A current detector for detecting a magnitude of the silencing signal current supplied to the sound wave generator via a power amplifier, and detecting an abnormality of the power amplifier based on a detection current of the current detector. 3. The muffler according to claim 1, wherein the output of the power amplifier is shut off when the power is turned off. 4. When an abnormality of the sound wave generator is detected,
The muffler according to any one of claims 1 to 3, wherein an amplification factor of the muffling signal current supplied to the remaining normal sound wave generator is adjusted. 5. The muffler according to claim 1, wherein a display for displaying an abnormality of the sound wave generator is provided for each of the plurality of sound wave generators. 6. A noise detecting means for detecting noise of a noise source, a silencing deviation detecting means for detecting a silencing deviation, receiving the output of the noise detecting means and the output of the silencing deviation detecting means, And a muffling signal generator for forming a muffling signal for generating sound waves of equal and opposite phases from the sound wave generating means toward the inside of the sound absorbing duct, wherein the noise detecting means and / or the muffling deviation are provided. The detection means includes a plurality of noise detectors and / or a plurality of noise reduction deviation detectors, and detects an abnormality of the noise detector and / or the noise reduction deviation detector from a sound receiving state of a test signal emitted from the sound wave generation means. And when the abnormal noise detector and / or the silencing deviation detector is detected, the output from the noise detector and / or the silencing deviation detector to the muffling signal generator is performed. Muffler being characterized in that so as to cut off the supply. 7. When the noise detector and / or the silencing deviation detector detects an abnormality, the noise detecting means and / or the silencing deviation comprising the remaining normal noise detector and / or the silencing deviation detector. 7. The muffler according to claim 6, wherein the detection gain from the detection means is adjusted. 8. The apparatus according to claim 7, wherein the detection gain is adjusted based on an output of a comparator that compares an output of the noise detector and / or the silencing deviation detector with the test signal. The sound deadening device according to claim 1. 9. A display for displaying an abnormality of the noise detector and / or the silencing deviation detector is provided for each of the plurality of noise detectors and / or the plurality of silencing deviation detectors. The muffler according to any one of claims 6 to 8.