JPH07219562A - Noise detector - Google Patents

Abstract

PURPOSE:To sufficiently enhance the detection accuracy of the noises in a duct by averting an adverse influence caused by generation of self-air flow noises and a fluctuation in turbulence pressure on a microphone disposed to an active silencer, etc., formed by using an adaptive IR filter. CONSTITUTION:A microphone body 7 is housed in a pipe member 6 closed at both ends by acoustic absorbing materials as the detecting microphone 2 of the active silencer. This pipe member 6 is embedded into the acoustic absorbing material 1b constituting the wall surface of the duct 1 and is so positioned as to face the internal space of the duct 1. A slit 6a extending in the propagation direction of the noises in the duct is formed in the part facing the internal space of the duct 1 to offset the fluctuations in the turbulence pressures transmitted from the slit 6a to the inside of the pipe member 6 with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise detecting device for detecting noise in a fluid passage, and more particularly to a measure for improving noise detecting accuracy.

[0002]

2. Description of the Related Art Conventionally, as an example of an active silencer for detecting noise in a duct space as a fluid passage and reducing the noise, there has been known one disclosed in Japanese Patent Laid-Open No. 5-323974. This type of active silencer includes a detection microphone, an adaptive FIR (Finite I)
npulse Response) filter and speaker. Then, after generating an inverted sound signal having the same amplitude and an opposite phase with respect to the noise signal based on the noise in the duct detected by the detection microphone by the adaptive FIR filter, the inverted sound signal is input to the speaker to generate the noise in the duct. The reversal sound that cancels out is radiated to the sound dead space in the duct.

Further, a monitor microphone is arranged at a predetermined observation point in the sound dead space, and the monitor microphone detects the synthesized sound of the noise in the duct and the reversal sound at the observation point as the noise in the duct. Then, this synthesized sound signal is fed back to the adaptive FIR filter, and the filter coefficient of the adaptive FIR filter is sequentially updated so that the synthesized sound signal level becomes smaller, thereby reducing the sound pressure level at the observation point. ing.

[0004]

By the way, as one means for improving the sound deadening performance in the above-described active sound deadening apparatus, it is possible to improve the accuracy of detecting noise in the duct by the microphone.

However, in the conventional configuration, due to various causes, a signal such as noise other than the in-duct noise that should be originally detected is included in the detection signal of the microphone. Therefore, it is difficult to sufficiently increase the accuracy of detecting the noise in the duct. For this reason, there is a limit in improving the sound deadening performance in the active sound deadening device.

The present invention has been made in view of the above points, and an object thereof is to sufficiently increase the accuracy of detecting noise in a duct by a microphone.

[0007]

In order to achieve the above object, the present invention eliminates the cause of generation of a signal such as noise other than the in-duct noise that should be originally detected. In the inventions according to claims 1 and 2, for example, when the microphone (b) is arranged in the duct (a) as shown in FIG. 11, the microphone (b) becomes an obstacle of the air flow in the duct, A device that avoids self-air flow noise that occurs due to turbulence in the surroundings and avoids the effects of turbulent pressure fluctuations that occur due to turbulence that occurs near the microphone Is. Specifically, first, the invention according to claim 1 provides a fluid passage.
It is premised on a noise detection device that detects noise propagating in (A). Then, the tubular pipe member (6) and the pipe member
A channel wall (1) having a microphone body (7) housed in the internal space of (6) and forming the fluid channel (A).
An accommodating portion (1e) capable of accommodating the pipe member (6) is formed therein. Further, the pipe member (6) is housed in the housing portion (1e), and a part of the outer surface of the pipe member (6) is made substantially flush with the inner surface of the passage wall (1) so as to face the fluid passage (A). Further, in the portion of the pipe member (6) facing the fluid passageway (A), it extends in the noise propagation direction of the fluid passageway (A) and opens the internal space of the pipe member (6) toward the fluid passageway (A). The slit (6a) is formed.

The invention according to claim 2 is the fluid passage.
It is premised on a noise detection device that detects noise propagating in (A). Then, the tubular pipe member (6) and the pipe member
The microphone body (7) housed in the internal space of (6) is provided. Further, the pipe member (6) is connected to the fluid passage.
Install on the outside of the passage wall (1) forming (A). Furthermore, the pipe member (6) and the passage wall (1) have slits (6a) extending in the noise propagation direction of the fluid passage (A) and communicating the internal space of the pipe member (6) with the fluid passage (A). , (1d) are formed respectively.

The invention according to claim 3 is the noise detecting device according to claim 1 or 2, wherein the slits (6a), (1d)
A covering member (10), (13) that covers the noise is provided.

According to a fourth aspect of the present invention, when the noise detecting device is attached to the passage wall, the vibration of the passage wall is prevented from being transmitted to the noise detecting device. Specifically, it is premised on a noise detection device that detects noise propagating in the fluid passage (A). The tubular pipe member (6) and the microphone body (7) housed in the internal space of the pipe member (6) are provided.
(6) on the passage wall (1) forming the fluid passage (A) with an elastic member.
It is configured to be supported via (11).

According to a fifth aspect of the present invention, there is provided a noise detecting device,
When a tubular pipe member and a microphone body housed in the internal space of the pipe member are provided, resonance of noise in the internal space of the pipe member is avoided. Specifically, it is premised on a noise detection device that detects noise propagating in the fluid passage (A). And
A tubular pipe member (6) and a microphone body (7) housed in the internal space of the pipe member (6) are provided, and both ends of the pipe member (6) in the longitudinal direction are connected to the sound absorbing material (8). It is configured to be closed by (9).

The invention according to claim 6 is the above-mentioned claim 1.
And the structure according to the invention described in 4 above. Specifically, it is premised on a noise detection device that detects noise propagating in the fluid passage (A). And a tubular pipe member
(6) and the microphone body (7) housed in the interior space of the pipe member (6) are provided, and the pipe member (6) can be housed in the passage wall (1) forming the fluid passage (A). Storage compartment
Form (1e). Further, the pipe member (6) is accommodated in the accommodating portion (1e) while being supported by the passage wall (1) forming the fluid passage (A) via the elastic member (11), and Fluid passage with part of the inner surface of the passage wall (1) being approximately flush
Face (A). Further, in the portion of the pipe member (6) facing the fluid passageway (A), it extends in the noise propagation direction of the fluid passageway (A) and opens the internal space of the pipe member (6) toward the fluid passageway (A). The slit (6a) is formed.

The invention according to claim 7 is the above-mentioned claim 1.
And the configuration according to the invention described in 5. Specifically, in the noise detecting device according to claim 1 or 6, the pipe member (6) is provided with a sound absorbing material at both ends in the longitudinal direction.
It is configured to be closed by (8) and (9).

The invention according to claim 8 is the same as claim 1,
In the noise detecting device described in 2, 4, 5, 6 or 7,
The fluid passage (A) serves as the internal space of the air conditioning duct (1).

According to a ninth aspect of the present invention, the first detecting means (2) for detecting noise propagating through the fluid passage (A) and the noise signal from the first detecting means (2) are in anti-phase with each other. An adaptive FIR filter (5) that generates an inverted sound signal of the same amplitude, and an additional sound source (3) that receives the inverted sound signal generated by the adaptive FIR filter (5) and emits the inverted sound to the fluid passage (A) ) And second detecting means (4) for detecting the reduced sound level at a predetermined observation point of the fluid passage (A) and feeding back to the adaptive FIR filter (5), the adaptive FIR filter (5) is Among the first detecting means (2) and the second detecting means (4), the active muffling apparatus updates the filter coefficient so as to reduce the sound pressure level around the observation point based on the fed back reduced sound level. Claims 1, 2, 4 in at least one
The configuration is such that the noise detecting device described in 5, 6, 7 or 8 is used.

[0016]

With the above construction, the following effects can be obtained in the present invention. According to the first aspect of the present invention, when the noise propagating through the fluid passage (A) is detected by the noise detecting device, the noise is generated by the pipe member (6) housed in the housing portion (1e) of the passage wall (1). The pipe member (6) passing through the slit (6a)
Is transmitted to the interior space of. Then, the noise is detected by the microphone body (7). The pipe member (6) accommodated in the accommodating portion (1e) has its outer surface substantially flush with the inner surface of the passage wall (1) and is not located in the fluid passage (A). No self-generated air noise. That is,
The noise signal detected by the microphone body (7) will not contain any self-airstream noise. Also,
Even in the situation where turbulence is generated around the noise detection device, the extension direction of the slit (6a) extends in the noise propagation direction, so that the pipe from each part in the longitudinal direction of the slit (6a). The turbulent pressures propagated in the internal space of the member (6) cancel each other out, and the turbulent pressure fluctuation does not occur in the internal space of the pipe member (6).

In the invention according to claim 2, the pipe member (6)
Since it is attached to the outer surface of the passage wall (1), no self-air flow noise is generated, and the noise signal detected by the microphone body (7) does not include any self-air flow noise. become. Further, claim 1 described above
Similar to the operation according to the described invention, the turbulent pressures propagated from the longitudinal portions of the slit (6a) to the internal space of the pipe member (6) cancel each other out, and in the internal space of the pipe member (6). The turbulent pressure fluctuation does not occur.

According to the invention of claim 3, the covering member (10),
Since the slits (6a) and (1d) are covered with (13), the entry of dust into the internal space of the pipe member (6) is suppressed and the microphone body (7) is protected. .

In the invention according to claim 4, when the passage wall (1) vibrates due to the influence of noise in the fluid passage (A), this vibration is absorbed by the elastic member (11) and transmitted to the pipe member (6). Since the noise is suppressed, the noise detection accuracy will not be deteriorated due to the influence of this vibration.

In the invention according to claim 5, the pipe member (6)
Since both ends of the pipe are closed by the sound absorbing materials (8) and (9), resonance of noise in the internal space of the pipe member (6) is avoided, and noise of a specific frequency is amplified. Disappears.

According to the invention described in claim 6, both the operations according to the invention described in claims 1 and 4 can be obtained.

According to the invention described in claim 7, both the operations according to the inventions described in claims 1 and 5 can be obtained.

In the invention of claim 8, the air conditioning duct
(1) It is possible to accurately detect noise propagating inside.

In the invention of claim 9, the first detecting means
Adaptive FIR filter based on the noise signal from (2) (5)
The inverted sound signal generated by is input to the additional sound source (3), and the inverted sound is radiated from the additional sound source (3) to the fluid passage (A). In addition, the second detection means (4) detects the reduced sound level at a predetermined observation point and feeds it back to the adaptive FIR filter (5), and the filter coefficient of the adaptive FIR filter (5) is updated to update the noise around the observation point. The sound pressure level is reduced. Since the noise detecting device according to claim 1 or 2 is used in at least one of the first detecting means (2) and the second detecting means (4), high noise detection accuracy can be obtained. The silencing performance of the active silencing device will be improved.

[0025]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. Further, in this example, a case where the noise detection device according to the present invention is used for an active silencer will be described.

FIG. 1 shows the overall construction of the active silencer. (1) is a duct as a passage wall that forms the duct internal space (A) as a fluid passage through which noise propagates.
(F) is a blower fan as a noise source arranged at the upstream end (the left end in FIG. 1) in the duct (1). (2) is a detection microphone as the first detection means for detecting the noise generated from the blower fan (F) and propagated in the duct (1). Reference numeral (3) is a speaker which is arranged on the downstream side of the detection microphone (2) and which emits a reversal sound having a phase opposite to that of the noise and having the same amplitude to the noise-eliminating space of the duct (1). The speaker (4) synthesizes the noise propagating in the duct and the inverted sound emitted from the speaker (3).
(3) A monitor microphone as a second detecting means for detecting at the downstream observation point.

Further, (5) is an adaptive F that receives the output signals of the detection microphone (2) and the monitor microphone (4).
It is an IR filter. This adaptive FIR filter (5)
Includes a silence filter (5a) and a control unit (5b) for adaptive control. Mute filter (5a) is the detection microphone (2)
It is designed to generate an inverted sound signal having a phase opposite to that of the noise signal received from the same and having the same amplitude. Control unit (5b)
Is the least mean squares method (LMS; Least Mean Square)
This is an adaptive control using an algorithm. That is, based on the noise signal received from the detection microphone (2) and the synthetic sound signal fed back from the monitor microphone (4), the LMS of the LMS is designed to reduce the sound pressure level at the observation point in the duct (1). Update the filter coefficient of the silence filter (5a) as a control parameter to
The inverted sound signal of (5a) is adaptively controlled and corrected. The inverted sound signal generated by the sound deadening filter (5a) is input to the speaker (3).

Next, the structure of the detection microphone (2) and its peripheral portion, which is the feature of this embodiment, will be described. This detection microphone (2), as shown in FIG. 2 and FIG.
It is equipped with a cylindrical pipe member (6). The cylindrical sound-absorbing materials (8) and (9) are fitted and closed at the open portions at both ends in the longitudinal direction of the pipe member (6). A microphone body (7) is housed inside the pipe member (6). The microphone body (7) is arranged so that its back surface is close to the sound absorbing material (9) on one side and is arranged so as to face the internal space of the pipe member (6).
It is designed to detect sounds in the interior space of. Further, the signal line (7a) of the microphone body (7) is connected to the FIR filter (5) by penetrating a sound absorbing material (9) arranged on the back side of the microphone body (7).

As one of the features of the detection microphone (2), the pipe member (6) has a slit (6a) extending in the longitudinal direction of the pipe member (6) so that the inside and the outside of the pipe member (6) communicate with each other. ) Is formed. Furthermore, this pipe member
On the outer surface of (6), a cloth (10) as a covering member arranged so as to cover the slit (6a) is attached.
That is, the sound around the detection microphone (2) propagates through the cross (10) and the slit (6a) into the internal space of the pipe member (6) and is detected by the microphone body (7). Has become.

Next, the structure in which the detection microphone (2) thus constructed is supported by the duct (1) will be described. As shown in Figure 4, the detection microphone (2)
Is buried in the wall of the duct (1).

First, the structure of the duct (1) in which the detection microphone (2) is embedded will be described. This duct
In (1), a sound absorbing material (1b) made of glass wool having a predetermined thickness is attached to the entire inner wall surface of a duct body (1a) made of sheet metal. Furthermore, the entire surface of this sound absorbing material (1b) is covered with an inner cloth (1
It is covered with c) to prevent the sound absorbing material (1b) from scattering in the space inside the duct. That is, the duct (1) has a three-layer structure in which the duct body (1a), the sound absorbing material (1b), and the inner cloth (1c) are overlapped with each other. Also this duct (1)
Contains a housing for the detection microphone (2)
(1e) is formed.

The detection microphone (2) is accommodated in the accommodating portion (1e) and attached to the inner wall surface of the duct body (1a) via an anti-vibration rubber (11) as an elastic member. It is embedded in the sound absorbing material (1b) in the state of being kept. Further, the detection microphone (2) is arranged such that a portion of the outer peripheral surface thereof in which the slit (6a) is formed is in contact with the inner pasting cloth (1c). Therefore,
The interior space of the pipe member (6) and the interior space of the duct (1) are separated by these two cloths (1c) and (10). For this reason, the detection microphone (2) passes through the crosses (1c), (10) and goes through the slit (6a) of the pipe member (6) to the pipe member.
Only the sound propagated to the internal space of (6) is detected by the microphone body (7). In addition, when the detection microphone (2) is arranged, the pipe member
The longitudinal direction of (6) coincides with the extension direction of the duct (1), so that the extension direction of the slit (6a) corresponds to the extension direction of the duct (1), that is, the propagation direction of noise in the duct. There is. As an example of specific dimensions of each part of the detection microphone (2), the pipe member (6) has an inner diameter of 10 mm and a wall thickness of 0.5 mm, and the slit (6a) has a width dimension of 1 mm and a length dimension. Is 200 mm.

Next, a silencing operation for silencing the noise in the duct (1) using the above active silencing device will be described. First, the noise generated from the blower fan (F) and propagating in the duct (1) passes through the crosses (1c) and (10) at the position where the detection microphone (2) is arranged, and then the noise of the pipe member (6). It is propagated from the slit (6a) to the internal space of the pipe member (6). Then, the noise is detected by the microphone body (7).

Thereafter, the noise signal based on the noise detected by the microphone body (7) is converted into an adaptive FIR filter.
It is input in (5). And the adaptive FIR filter (5)
Generates a reversal sound signal having the same phase and the opposite phase as the noise signal.The reversal sound signal is input to the speaker (3), and the reversal sound is radiated from the speaker (3) into the duct (1). To be done. As a result, the noise in the duct (1)
It is well reduced by the reversal sound radiated from (3).

Further, at the observation point, the reduced noise level is detected by the monitor microphone (4), and the reduced noise signal, that is, the reduced sound signal is fed back to the control section (5b) of the adaptive FIR filter (5). Based on this reduced sound signal, the mute filter of the control parameter of the LMS
The filter coefficient of (5a) is sequentially updated. Therefore, the reversal sound signal is generated by the noise reduction filter (5a) with respect to the noise in the duct (1) with high accuracy over time, and when the filter coefficient converges, the observation in the duct (1) is performed. The sound pressure level at the point is best reduced.

The operation characteristic of this example is as follows.
This is in the noise detection operation by the detection microphone (2) described above. That is, the detection microphone (2) in this example
Is embedded in the sound absorbing material (1b) of the duct (1), so that the detection microphone (2) does not obstruct the air flow in the duct and turbulence does not occur in the surroundings. That is,
The conventional self-flow noise does not occur at all. For this reason, the noise signal detected by the detection microphone (2) does not include self-airflow noise at all, and the detection accuracy of noise in the duct is ensured to be high.

Further, in the case where the detection microphone (2) is arranged in the vicinity of the air outlet of the blower fan (F) and turbulent flow is generated in the vicinity of the air outlet, Since the extension direction of the slit (6a) matches the propagation direction of the noise in the duct, the turbulent pressures propagated from the longitudinal parts of the slit (6a) to the internal space of the pipe member (6) cancel each other out. To be done. For this reason, the pipe member (6)
In the internal space of, there is no turbulent pressure fluctuation. Therefore, the detection microphone (2) does not detect the pressure fluctuation as the noise in the duct as in the conventional case, which also ensures the high detection accuracy of the noise in the duct.

As described above, according to the present example, the occurrence of self-air flow noise and the adverse effects of turbulent pressure fluctuations, which have hindered the improvement of the detection accuracy of the noise in the duct by the detection microphone (2) in the past, are avoided. By doing so, the detection accuracy of the noise in the duct by the detection microphone (2) can be made sufficiently high, and thus the silencing performance of the active silencer can be improved.

Although the duct body (1a) may vibrate under the influence of noise in the duct, the pipe member (6) has a vibration-proof rubber against the inner wall surface of the duct body (1a) as described above.
Since it is attached via (11), the vibration of the duct body (1a) is suppressed from being transmitted to the detection microphone (2), and the influence of this vibration reduces the detection accuracy of noise in the duct. You can avoid that.

Furthermore, both ends of the pipe member (6) have sound absorbing materials (8),
This pipe member because it is blocked by (9)
Resonance of noise in the internal space of (6) is avoided, noise of a specific frequency is not amplified, and noise can be accurately detected by the microphone body (7).

Further, the microphone body (7) is housed inside the pipe member (6) and the slit (6a) is crossed (1).
Microphone body (7) as it is covered by
Can be protected, and the occurrence of damage or failure can be suppressed.

Next, an experiment conducted to confirm the effect of the present invention that the detection accuracy of the noise in the duct by the detection microphone (2) can be made sufficiently high will be described. In this experiment, as a conventional structure, as shown in FIG. 5, the detection microphone (2 ′) is attached to the inner wall surface of the duct (1) and placed in the space inside the duct, and as a structure of the present invention, FIG. Duct the detection microphone (2) as shown
Measurement of the relationship between the noise frequency and the coherence between the detection microphones (2), (2 ') and the monitor microphone (4) for the case of being embedded in the wall of (1) Is. The conditions of this experiment are that the duct (1) has a rectangular cross section of 300 mm × 215 mm.
Set each microphone (2), (2 ') to a position 300 mm from the outlet of the blower fan (F), and set the air volume from the blower fan (F) to 6
It was 2 m ³ / min.

The experimental results are shown in FIGS. 7 and 8, FIG. 7 shows the experimental results in the conventional structure (shown in FIG. 5), and FIG. 8 shows the experimental results in the structure of the present invention (shown in FIG. 6). is there. When the coherence is closer to 1, the correlation between the detection microphone (2) and the monitor microphone (4) is better, and the adverse effects of noise are less, and the active muffling device can obtain high muffling performance. It is possible.

As can be seen from FIGS. 7 and 8, the structure of this example has a higher coherence in the frequency range of 0 to 500 Hz than that of the conventional structure. Therefore, it was confirmed that the detection accuracy of the noise in the duct by the detection microphone (2) was improved.

(Second Embodiment) Next, a second embodiment according to the present invention will be described. The above-described first embodiment has been described with respect to the case where the detection microphone (2) is arranged on the duct (1) formed by attaching the sound absorbing material (1b) to the entire inner wall surface of the duct body (1a). However, in this example, the case where the detection microphone (2) is provided for the duct (1) composed of only the duct body (1a) will be described.

As shown in FIGS. 9 and 10, the arrangement structure of the detection microphone (2) in this example is a duct.
A slit (1d) of a specified length extending in the duct extension direction is formed in the center of the upper surface of (1) in the width direction.
A detection microphone substantially similar to that of the above-described embodiment at a position facing the slit (1d) on the upper surface of (1).
(2) is provided. The detection microphone of this example
In (2), unlike the detection microphone (2) of the first embodiment described above, the cloth (10) that covers the slit (6a) is not provided.

The arrangement state of the detection microphone (2) is determined by the slit formed on the upper surface of the duct (1).
Pipe member (6) of detection microphone (2) against (1d)
The slits (6a) formed in the are opposed to each other.

Further, as a support structure of the detection microphone (2), a support member (12) having a hat-shaped cross section which opens downward is attached to the upper surface of the duct (1). Anti-vibration rubber (11), (1
The pipe member (6) is supported via 1). Furthermore,
A cross (13) as a covering member is attached to the inner wall surface of the duct (1) at a position corresponding to the slit (1d) formed in the duct (1). The internal space of (1) and the internal space of the pipe member (6) are partitioned.

Due to such a structure, the blower fan
The noise generated from (F) and propagating in the duct (1) passes through the cross (13) attached to the inner wall surface of the duct (1), and the noise of the duct (1) and the pipe member (6) The noise is propagated to the internal space of the pipe member (6) through the slits (1d) and (6a) formed in each, and this noise is detected by the microphone body (7).

Therefore, the same effect as that of the above-described first embodiment can be obtained by the structure of this embodiment. That is, since the microphone (2) is installed outside the duct (1), self-airflow noise is avoided, and the turbulent pressure in the internal space of the pipe member (6) is canceled out, so that the detection accuracy of noise in the duct is improved. Secured high.

As described above, according to the structure of this example, the duct (1) which is not provided with the sound absorbing material and includes only the duct body (1a).
On the other hand, it is possible to dispose the detection microphone (2) capable of ensuring high detection accuracy of noise in the duct.

Further, as in the case of the first embodiment described above, the pipe member (6) is attached to the duct body (1a) through the vibration isolating rubber (11) and the supporting member (12). It should be possible to avoid the adverse effects of vibrations, avoid the resonance of noise by the sound absorbing materials (8), (9) that block both ends of the pipe member (6), and protect the microphone body (7) by the cross (13). It also becomes.

In each of the above-described embodiments, the case where the structure according to the present invention is applied to the detection microphone (2) and its peripheral portion has been described, but the present invention is not limited to this.
It is also possible to apply to the monitor microphone (4) and its peripheral part.When both microphones (2) and (4) have the structure of the present invention, noise detection accuracy is further improved. It Further, the present invention is not limited to the microphones (2) and (4) provided in the active silencer described above, but is arranged so as to simply detect the noise propagated in the internal space of the duct (1). It may be applied to a microphone. Further, although the cloths (10) and (13) are adopted as the covering members for covering the slits (6a) and (1d), the present invention is not limited to this, and a wire mesh having a fine mesh may be adopted.

[0054]

As described above, according to the present invention, the following effects are exhibited. According to the first aspect of the present invention, the pipe member is accommodated in the accommodating portion of the passage wall, and a part of the outer surface of the pipe member is made substantially flush with the inner surface of the passage wall so as to face the fluid passage. Since a slit that extends in the noise propagation direction of the fluid passage and opens the internal space of the pipe member toward the fluid passage is formed in the portion of the member facing the fluid passage, the accuracy of detecting noise in the fluid passage is improved in the related art. It is possible to avoid the adverse effects due to the occurrence of self-air flow noise and the fluctuation of turbulent pressure, which have hindered the improvement, and the detection accuracy of noise in the fluid passage can be sufficiently increased.

According to the second aspect of the present invention, the pipe member is attached to the outer surface of the passage wall, and the pipe member and the passage wall extend in the noise propagation direction of the fluid passage to form the internal space of the pipe member and the fluid passage. Since the slits for communicating with each other are formed respectively, it is possible to avoid the adverse effects of the occurrence of self-airflow noise and turbulent pressure fluctuations, as in the case of the effect according to the invention described in claim 1, and the duct by the microphone. It is possible to sufficiently increase the accuracy of detecting internal noise.

According to the third aspect of the present invention, since the noise-permeable covering member for covering the slit is provided, intrusion of dust into the internal space of the pipe member is suppressed, and the microphone body can be protected and damaged. And the occurrence of failures can be suppressed.

According to the fourth aspect of the invention, since the pipe member is supported on the passage wall via the elastic member, when the passage wall vibrates due to the influence of noise in the fluid passage, this vibration is caused by the elastic member. The absorption and the transmission to the pipe member are suppressed, and it is possible to prevent the detection accuracy of the noise in the fluid passage from being lowered due to the influence of this vibration.

According to the fifth aspect of the present invention, since both ends in the longitudinal direction of the pipe member are closed by the sound absorbing material, noise does not resonate in the internal space of the pipe member, and the microphone body accurately The noise in the space inside the duct can be detected. According to the invention of claim 6, the effects of the inventions of claims 1 and 4 described above can be obtained together, and the accuracy of detecting the noise in the fluid passage can be further enhanced.

According to the invention of claim 7, the effects of the inventions of claims 1 and 5 described above can be obtained together, and the accuracy of detecting the noise in the fluid passage can be further enhanced by this. .

According to the eighth aspect of the invention, since the fluid passage is the internal space of the air conditioning duct, noise propagating in the air conditioning duct can be accurately detected.

According to the invention described in claim 9, in the active muffler, at least one of the first detecting means and the second detecting means is characterized by claim 1, 2, 4, 5, 6, 7 or 8. Since the noise detecting device is used, noise can be detected with high accuracy, the silencing performance of the active silencer is improved, and the reliability of the active silencer can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an entire active silencer.

FIG. 2 is a bottom view of a detection microphone.

FIG. 3 is a cross-sectional view of the detection microphone at a position corresponding to a line III-III in FIG.

FIG. 4 is a vertical cross-sectional view showing an arrangement state of detection microphones.

FIG. 5 is a cross-sectional view showing an arrangement state of a conventional detection microphone used in an experiment.

FIG. 6 is a cross-sectional view showing an arrangement state of a detection microphone having the structure of the present invention used in an experiment.

FIG. 7 is a diagram showing a relationship between frequency and coherence as an experimental result of a conventional structure.

FIG. 8 is a diagram showing a relationship between frequency and coherence as an experimental result of the structure of the present invention.

FIG. 9 is a vertical cross-sectional view showing an arrangement state of detection microphones in a modified example.

10 is a cross-sectional view showing an arrangement state of detection microphones at a position corresponding to line XX in FIG.

FIG. 11 is a diagram showing a conventional microphone arrangement state.

[Explanation of symbols]

 (1) Duct (passage wall) (1d) Slit (1e) Storage section (2) Detection microphone (first detection means) (3) Speaker (additional sound source) (4) Monitor microphone (second detection means) (5) Adaptive FIR filter (6) Pipe member (6a) Slit (7) Microphone body (8), (9) Sound absorbing material (10), (13) Cloth (abdominal member) (11) Anti-vibration rubber (elastic member) (A) Duct space (fluid passage)

Claims (9)

[Claims] 1. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a cylindrical pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ) And a pipe member is provided in the passage wall (1) forming the fluid passage (A).
A storage part (1e) capable of storing (6) is formed, and the pipe member (6) is stored in the storage part (1e), and a part of the outer surface of the pipe wall (1e) is The inner surface of the pipe member (6) is substantially flush with the fluid passageway (A), and the portion of the pipe member (6) that faces the fluid passageway (A) extends in the noise propagation direction of the fluid passageway (A). Element
A noise detecting device characterized in that a slit (6a) is formed to open the internal space of (6) toward the fluid passage (A). 2. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a tubular pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ), The pipe member (6) is a passage wall forming a fluid passage (A).
The pipe member (6) and the passage wall (1) are attached to the outer surface of the fluid passage (A).
The noise detecting device is characterized in that slits (6a), (1d) extending in the noise propagation direction of the pipe member (6) and connecting the internal space of the pipe member (6) and the fluid passage (A) are formed. 3. The noise detecting device according to claim 1, further comprising a covering member (10), (13) which covers the slits (6a), (1d) and allows noise to pass therethrough. 4. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a cylindrical pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ) And the pipe member (6) has a passage wall (1) forming a fluid passage (A).
A noise detecting device, characterized in that it is supported by an elastic member (11). 5. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a cylindrical pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ) And both ends of the pipe member (6) in the longitudinal direction are attached to the sound absorbing materials (8), (9).
A noise detection device characterized in that it is blocked by. 6. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a tubular pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ) And a pipe member is provided in the passage wall (1) forming the fluid passage (A).
A storage part (1e) capable of storing (6) is formed, and the pipe member (6) is a passage wall forming a fluid passage (A).
The storage unit (1) is supported by the elastic member (11) on the (1).
e) and part of the outer surface is the passage wall (1)
Of the pipe member (6) extending substantially in the noise propagation direction of the fluid passage (A) at a portion of the pipe member (6) facing the fluid passage (A). Pipe member
A noise detecting device characterized in that a slit (6a) is formed to open the internal space of (6) toward the fluid passage (A). 7. A noise detecting device for detecting noise propagating through a fluid passage (A), comprising a tubular pipe member (6) and a microphone body (7) housed in an internal space of the pipe member (6). ) And a pipe member is provided in the passage wall (1) forming the fluid passage (A).
A storage part (1e) capable of storing (6) is formed, and the pipe member (6) is stored in the storage part (1e), and a part of the outer surface of the pipe wall (1e) is The inner surface of the pipe member (6) is substantially flush with the fluid passageway (A), and the portion of the pipe member (6) that faces the fluid passageway (A) extends in the noise propagation direction of the fluid passageway (A). Element
A slit (6a) is formed to open the internal space of (6) toward the fluid passage (A), and both ends of the pipe member (6) in the longitudinal direction are sound absorbing materials (8), (9).
The noise detection device according to claim 1 or 6, wherein the noise detection device is closed. 8. The fluid passage (A) is an internal space of the air conditioning duct (1), wherein the fluid passage (A) is an internal space.
Or the noise detection device described in 7. 9. A first detection means (2) for detecting noise propagating through the fluid passage (A), and a reversal sound signal having the same amplitude as the noise signal from the first detection means (2) but in opposite phase. And an adaptive FIR filter (5) for generating
Reversing sound signal generated by
An adaptive FIR filter that detects the additional sound source (3) radiated to (A) and the reduced sound level at a specified observation point in the fluid passage (A)
A second detection means (4) for feeding back to (5),
The adaptive FIR filter (5) updates the filter coefficient so as to reduce the sound pressure level around the observation point based on the feedback reduced sound level. 9. The noise detecting device according to claim 1, wherein the noise detecting device is used in at least one of the two detecting means (4).