JP3446242B2 - Active silencer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates unsteady broadband noise in a sound wave propagation passage such as a space in a duct by applying a reversal sound having an opposite phase and the same amplitude. The present invention relates to an improvement of an active silencer that performs

[0002]

2. Description of the Related Art Generally, an active muffling device of this type is used, for example, for an unsteady wide-band noise of a sound wave propagation path such as a space in a duct, which has a phase opposite to that of the noise and a reversal sound of the same amplitude. It is known to generate noise to muffle sound (see, for example, 1988 EA-88-29 of Technical Research Report of the Institute of Electronics, Information and Communication Engineers).

This type of active silencer will be described in detail. As shown in FIGS. 8 and 9, in the duct (a),
One detection microphone (b), a speaker (c), and a monitor microphone (d) are arranged in this order from the upstream side of the air flow, and each of them is connected to a controller (e). Then, the controller (e) has an adaptive FIR that generates an inverted sound signal having a phase basically opposite to that of the noise signal detected by the detection microphone (b) and having the same amplitude.
(Finite Impulse Response) Filter (f) and propagation time required for the inverted sound radiated from the speaker (c) by the output of the inverted sound signal to the speaker (c) to be input to the monitor microphone (d) and the speaker A first filter composed of an FIR filter having a predetermined transfer function for correcting the detection signal of the detection microphone (b) in consideration of the acoustic characteristics from (c) to the monitor microphone (d) and the characteristics of each device.
(g) and a second filter (h) consisting of an FIR filter having a predetermined transfer function to prevent the inverted sound radiated from the speaker (c) from propagating to the detection microphone (b) and causing howling. And an algorithm execution unit (i) for adaptive control.

Then, the adaptive FIR filter (f) generates a reversal sound signal of the same amplitude in anti-phase with respect to the noise signal in the space output from the detection microphone (b), and then the reversal sound signal is output to the speaker. Output to (c) and radiate the reversal sound to the space inside the duct (a).
The synthetic sound with the inversion sound radiated from the sound source is detected, the synthetic sound is input as a reduced sound level, and the adaptive FIR is applied by the algorithm execution unit (i) to reduce the reduced sound level.
The sound pressure level around the observation point is reduced by successively updating the filter coefficient of the filter (f).

[0005]

By the way, in such an active silencer, the detection microphone (b) and the monitor microphone (d) detect a sound as a compressional wave of air, and the fluctuation is detected by an electric signal. By converting into a signal, a noise signal or a reduced sound signal of a synthesized sound of the noise and the inversion sound is obtained. However, in such detection, when air turbulence occurs in the duct (a), the microphones (b) and (d) detect the vortex sound accompanying the turbulence. The electrical signal based on this vortex sound is a detection signal (noise signal or reduced sound signal).
Therefore, it becomes impossible to accurately detect only the sound to be detected. That is, the sound deadening performance is greatly hindered by the vortex sound accompanying the turbulent flow.

Then, such a situation becomes more remarkable as the air flow velocity in the duct becomes higher, and under such a high flow velocity condition, the silencing performance is particularly deteriorated.
In addition, a drift occurs in the vicinity of the fan of the air conditioner, and even when the active silencer as described above is installed in this part, only the sound to be detected is affected by this drift. It cannot be detected accurately, so
It was impossible to dispose this type of active silencer near the fan of the air conditioner.

Further, in such an active silencer, if one microphone fails, it becomes impossible to perform an appropriate silence function, and a problem remains in terms of system reliability.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a configuration capable of improving the accuracy of sound detection by a microphone and improving the reliability of the system.

[0009]

In order to achieve the above-mentioned object, in the present invention, a plurality of microphones are arranged and the signals of the sounds detected by the respective microphones are added together to cancel the noise due to the turbulence. I decided to do it.
Specifically, as shown in FIGS. 1 and 2, the invention according to claim 1 is one located in the space (2) inside the duct (1).
Noise source (Sp) and noise detection means (3) that detects the noise in the space (2) and outputs a noise signal, and the same amplitude in antiphase with respect to the noise signal from the noise detection means (3). FIR filter (13) for generating a reversal sound signal, and an additional sound source (4) for receiving the reversal sound signal generated by the sound deadening FIR filter (13) and radiating the reversal sound to the space (2) And the space (2)
Monitor means which is arranged at a predetermined observation point, detects the reduced sound level at the observation point, and outputs the reduced sound signal as feedback.
(5) and the noise signal from the noise detection means (3) and the reduced sound signal fed back from the monitoring means (5) are input, and the sound pressure level around the observation point is reduced by the noise signal and the reduced sound signal. As described above, the FIR filter for muffling (1
It is premised on an active silencer equipped with the adaptive algorithm executing means (15) for updating the filter coefficient of 3). Then, the noise detecting means (3) is arranged at a plurality of places in the space (2) so that the noise in the space (2) can be detected at each place, and the noise detecting means (3), The noise signals of (3), ... Are summed up, and the summed noise signal is added to the sound deadening FIR filter (13) and adaptive algorithm execution means.
The signal summing means (6) for transmitting to (15) is provided.

According to a second aspect of the present invention, in the active silencer according to the first aspect, each noise detecting means (3),
(3), ... Are arranged such that they are arranged at the same position with respect to one noise source (Sp) located in the space (2).

The invention according to claim 3 is the inside of the duct (1).
One noise source (Sp) located in the space (2) and noise detection means (3) that detects the noise in the space (2) and outputs a noise signal
And a muffling FIR filter for generating a reversal signal having the same amplitude and a reverse phase with respect to the noise signal from the noise detecting means (3)
(13), an additional sound source (4) that emits an inverted sound to the space (2) by receiving the inverted sound signal generated by the sound deadening FIR filter (13), and a predetermined observation point of the space (2) Placed in
Monitoring means (5) for detecting the reduced sound level at the observation point and outputting the reduced sound signal as feedback;
The noise signal from (3) and the reduced sound signal fed back from the monitoring means (5) are input, and the noise canceling FIR filter (to reduce the sound pressure level around the observation point by the noise signal and the reduced sound signal. It is premised on an active silencer equipped with an adaptive algorithm executing means (15) for updating the filter coefficient of 13). And the monitor means
(5) is arranged at a plurality of locations in the space (2) to enable detection of the reduced sound level at the observation point in the space (2) at each location, and the monitoring means (5), (5 ), ..., The signal summing means for summing the output signals and transmitting the summed output signal to the adaptive algorithm executing means (15) is provided.

According to a fourth aspect of the present invention, in the active silencer according to the third aspect, the monitor means (5), (5),
Are arranged at the same position with respect to one noise source (Sp) located in the space (2).

The invention according to claim 5 is the same as claim 1,
In the active silencer described in 2, 3, or 4, the tube (3) in which the noise detecting means (3) and the monitoring means (5) are formed in a cylindrical shape with a bottom and a slit (3c) is partially formed
The microphone body (3b) is housed in a).

[0014]

With the above-described structure, the following effects can be obtained in the present invention. In the invention according to claim 1, the noise elimination FIR filter is used for the noise signal from the noise detection means (3).
(13) generates an inverted sound signal, and an inverted sound corresponding to the inverted sound signal is emitted from the additional sound source (4) to the space (2). Also,
The monitor means (5) detects the reduced sound level at the observation point and feeds it back to the adaptive algorithm execution means (15), and the adaptive algorithm execution means (15) filters the silence FIR filter (13). The coefficient is updated sequentially. With such an operation, the sound pressure level around the observation point is favorably reduced. In addition, when detecting noise in the space (2 ) of the duct (1), one noise source (Sp)
Te noise detecting means (3) is detected noise at each location have been arranged in a plurality of locations, will be each is summed in the signal summation means (6), this summation, noise such as swirling component The ingredients will be offset. Therefore, the muffler FIR filter (13) and the adaptive algorithm execution means (1
The signal transmitted to 5) is only the noise signal emitted from the noise source to be originally detected, and the silencing operation is performed appropriately.

In the invention according to claim 2, each noise detecting means
Since (3), (3), ... Are arranged at the same position with respect to one noise source (Sp) located in the space (2),
It is not necessary to consider the time shift of the noise signal detected by each noise detection means (3), (3), ...

According to the third aspect of the invention, the sound is silenced in the space (2) in the same manner as the above-described operation according to the first aspect of the invention. Then, when detecting the reduced sound level at the observation point, the monitoring means (5) is arranged at a plurality of locations at the observation point, the reduced sound level is detected at each location, and each is summed by the signal summing means. Therefore, the noise component such as the vortex sound component is canceled by this addition. Therefore, the signal transmitted to the adaptive algorithm executing means (15) is only the reduced sound signal to be originally detected, and the silencing operation is appropriately performed.

According to the invention described in claim 4, in the same manner as the operation according to the invention described in claim 2, the monitor means (5),
(5), ... It is not necessary to consider the time shift of the reduced sound signal detected, and the provision of a delay circuit or the like is unnecessary.

According to the fifth aspect of the invention, when the sound is detected by the microphone body (3b), the air flowing in the space (2) flows along the outer surface of the tube (3a). In the main body (3b), only the sound that should be detected in the space (2) is detected, and the noise associated with the turbulence is removed. That is, the slit (3c) cancels out the noise component, and only the sound signal to be originally detected is output from the microphone body (3b).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment according to the invention described in claims 1 and 2 will be described below with reference to the drawings.

FIG. 1 shows an outline of the configuration of the active silencer of this example, and FIG. 2 shows the installation state of the active silencer of this example in a duct. And, (1) in FIG. 2 is a duct, which is located at the left end in the figure inside the duct.
A space (2) is formed as a propagation path for noise sound waves from one noise source (Sp). (3) is a detection microphone as noise detection means arranged upstream of the noise propagation direction indicated by the arrow in the space (2)
It is designed to detect noise. As a feature of this example, the detection microphones (3), (3), ... Are ducts.
It is arranged at a plurality of locations in (1) (details will be described later). (4) is an addition that is placed downstream of the detection microphone (3) in the direction of noise propagation and that emits a reversal sound of the opposite phase and the same amplitude as the noise to the space (2) of the duct (1). It is a speaker as a sound source.

In the duct (1), the speaker
A monitor microphone (5) as a monitoring means is arranged at a predetermined observation point on the downstream side in the noise propagation direction of (4). The monitor microphone (5) detects, at the observation point, a reduced sound level of noise reduced by the action of the reversal sound radiated from the speaker (4).

The speaker (4) is a controller (1) for generating an inverted sound signal having a phase opposite to that of noise and having the same amplitude.
1) via a D / A converter (not shown) or the like, and the controller (11) outputs the output signals of the detection and monitor microphones (3), (5) to the A / D converter ( (Not shown), and is input via an acoustic mixer (6) as signal summing means. In the controller (11), the inverted sound emitted from the speaker (4) by the output to the speaker (4) after generating the inverted sound signal is output to the monitor microphone.
Propagation time and speaker required to be input to (5) (4)
To the monitor microphone (5) and a first filter (12) consisting of an FIR filter having a predetermined transfer function for correcting the output signal of the detection microphone (3) in consideration of the characteristics of each device and the detection microphone ( 3) An adaptive FI as a muffling FIR filter that basically produces a reversal signal with the same amplitude as the noise signal received from
An FI having a predetermined transfer function for preventing the inverted sound radiated from the R filter (13) and the speaker (4) from propagating to the detection microphone (3) and causing howling.
A second filter (14) consisting of an R filter and an algorithm execution unit (15) as an algorithm execution means for adaptive control.
And are provided. Further, the first filter (12) and the adaptive FIR filter (13) are adapted to receive the signal from the adder circuit (7), and the adder circuit (7) outputs the output signal of the acoustic mixer (6). The output signal of the second filter (14) is removed from the first filter (12) and the adaptive FIR filter
The output signal is sent to (13). In addition, the algorithm execution unit (15) uses the least mean square method (LM
S; Least Mean Square) adaptive control is performed based on the delayed signal of the noise signal received through the first filter (12) and the reduced sound signal fed back from the monitor microphone (5). , Update the filter coefficient of the adaptive FIR filter (13) as the LMS control parameter so as to reduce the sound pressure level around the observation point in the duct (1), and adaptively control and correct the inverted sound signal. It is like this.

The detection microphones (3), (3), ... Arranged at a plurality of locations as the characteristic configuration of this embodiment are respectively disposed at four locations on the same vertical cross section in the duct (1). Has been done. That is, each detection microphone (3), (3), ... Is a noise source
They are arranged at positions with the same distance from (Sp). The structure of each of the detection microphones (3) will be described. As shown in FIG. 3, the detection microphone (3) includes a microphone body (3b) housed in a slit tube (3a). In addition, this structure is Journal of Sound
and Vibration (1989), P125 to P135, which will be described with reference to FIGS. 3 and 4. The tube (3a) is a bottomed cylindrical body having a curved front end, and a slit (3c) extending along the longitudinal direction of the tube (3a) is formed on the side surface thereof. . Then, on the bottom of this tube (3a), one microphone body (3
The detection microphone (3) is configured by arranging b). And a detection microphone configured in this way
(3) are arranged at four locations in the duct (1) so that the tapered tip of the tube (3a) faces the upstream side of the air flow.
For details of this arrangement structure, as shown in FIG.
The sound absorbing material (1a) disposed on the inner wall surface of (1) is partially removed, and the detection microphone (3) is placed in the recess (1b) formed by this removal. . With this structure, the air flowing in the duct (1) is
Guided by the tip of (3a), it will flow along its outer surface (see arrow in Fig. 3), and in the microphone body (3b), the sound from the noise source (Sp) in the duct (1) will be heard. Only noise will be detected and the noise associated with turbulence will be removed. The principle of noise removal by the tube (3a) will be described. As shown in FIG. 4, a large number of microphones (20), (20), ... Are arranged in parallel and the respective detection signals are delayed by the delay circuit (21), (). In a system in which the time delay is corrected by 21), ... And added by the adder circuits (22), (22), ..., the noise component (eddy current sound component) is canceled by the addition of these detection signals. Eventually, only the sound signal that should be detected should be output. Such an action will be performed in the slit (3c) of the tube (3a), and the microphone body (3b) detects only noise-removed sound, that is, the sound emitted from the noise source (Sp). It is supposed to be done.

The thus-configured detection microphones (3), (3), ... Are arranged at four positions of equal distance from the noise source (Sp), and the detection microphones (3), (3) are arranged. The noise signals detected at, ... Are summed up by the sound mixer (6) and sent to the controller (11). Then, when the noise signals are added up by the acoustic mixer (6), the noise component (vortex sound component) is canceled out similarly to the principle of noise removal by the tube (3a) described above, and the controller (11) Is supposed to output only the sound that should be detected, that is, the signal of the sound emitted from the noise source (Sp).

Next, a silencing operation for silencing the noise in the duct (1) using the above active silencing device will be described.

First, the noise in the space (2) in the duct (1) is detected by the detection microphones (3), (3), ... And detected by the detection microphones (3), (3) ,. The generated noise signals are summed by the acoustic mixer (6). A noise component (vortex sound component) is canceled out in the summed noise signal, and the noise signal from which the noise component has been removed passes through the adding circuit (7) of the controller (11) and the adaptive FIR filter (13 ). The noise signals detected by the respective detection microphones (3), (3), ... Have some noise removed by the function of the tube (3a), and the noise removal operation by the tube (3a) A noise signal based on only the sound emitted from the noise source (Sp) by the noise removal operation by the addition of the noise signals detected by the detection microphones (3), (3), ... In the acoustic mixer (6) Is input to the adaptive FIR filter (13). Further, this noise signal is corrected by delay processing or the like for a predetermined time by the first filter (12) and is also input to the algorithm execution unit (15). And the adaptive FI
In the R filter (13), an inverted sound signal having a phase opposite to that of the noise signal and having the same amplitude is generated, the inverted sound signal is input to the speaker (4), and the inverted sound is output from the speaker (4). It is radiated into space (2). This radiation causes the duct (1)
The noise inside will be well reduced by the reversal sound radiated from the speaker (4).

Furthermore, the noise level reduced at the observation point,
That is, the reduced sound level is detected by the monitor microphone (5), and the reduced noise signal, that is, the reduced sound signal is fed back to the algorithm execution unit (15), and the reduced sound signal and the first filter (12) The filter coefficient of the adaptive FIR filter (13) is sequentially updated based on the noise signal. By updating this filter coefficient, the generation of the inverted sound signal by the adaptive FIR filter (13) is performed by the duct.
(1) The duct is used to accurately measure the noise in the duct over time.
The sound pressure level around the observation point in (1) is best reduced.

In this mute operation, the adding circuit (7)
The inverted sound signal output from the adaptive FIR filter (13) is input through the second filter (14), the inverted sound signal is subtracted from the noise signal, and the inverted sound emitted from the speaker (4) is generated. Howling is prevented from occurring by propagating to each detection microphone (3), (3), ....

As described above, according to the configuration of this example, one
The detection microphones (3), (3), ... are arranged at multiple locations with respect to the noise source (Sp), and the output signals of the detection microphones (3), (3), ... are combined in the acoustic mixer (6). By canceling the noise component (vortex sound component), the controller (1
In 1), since only the noise signal based on the sound emitted from the noise source (Sp) is output, it seems that the silencing performance is greatly hindered by the vortex sound accompanying turbulence as in the past. This can be avoided, and the sound deadening performance can be improved with the improvement in the accuracy of sound detection by the detection microphone (3). Further, the muffling performance can be maintained well even in a situation where the air velocity in the duct (1) is high. In addition, even if this device is installed in a place where uneven flow of air occurs, good silencing operation can be obtained.
It is feasible to dispose the silencer near the fan of the air conditioner. Also, even if one detection microphone (3) fails, the remaining microphones (3), (3), ... detect appropriate noise, so even in such a situation, the noise is suppressed. The operation can be performed stably, and the reliability of the system can be improved.

(Modification) A modification of the present invention will be described below. FIG. 6 shows a modified example of the invention according to claims 3 and 4, wherein not only the detection microphones (3), (3), ... Microphone (5), (5),
... are also arranged at a plurality of locations. Like the detection microphones (3), (3), ..., the monitor microphones (5), (5), ...
It is arranged in each place. In addition, the structure of each monitor microphone (5) is similar to that of the detection microphone (3), and the microphone body is housed inside the slit tube to remove noise. With this configuration, the output signals of the monitor microphones (5), (5), ... Are summed to cancel the noise component (eddy current sound component), and the controller (11) detects the sound that should be originally detected. That is, only the monitor signal of the reduced noise is output, and each monitor microphone is output.
(5), (5), ... It is avoided that the sound deadening performance is greatly hindered by the vortex sound caused by the turbulent flow in the peripheral area, and the sound deadening performance is improved as the sound detection accuracy of the monitor microphone (5) is improved. Can be improved.

Alternatively, the number of the detection microphones (3) may be one, and only the monitor microphones (5) may be arranged at a plurality of locations.

As another modified example, the one shown in FIG. 7 is the active muffler of the modified example described above, which has a cylindrical duct (1 ').
And the detection microphones (3),
(3), ... and monitor microphones (5), (5), ... are ducts
The inner peripheral surface of (1 ′) is arranged at positions at equal angular intervals (90 ° in this example).

The above-described embodiments are microphones.
Although (3) and (5) are arranged at four locations and arranged at equal distances from the noise source (Sp), the invention according to claim 1 or 3 However, the microphones (3) and (5) may be installed at two or three or five or more locations, and each microphone (3) and (5) may be a noise source (S
It may be arranged such that they are arranged at positions different in distance from p), and a delay circuit for correcting a time lag of sound detection is provided for each.

[0034]

As described above, according to the active muffler of the present invention, the following effects are exhibited. According to the invention of claim 1, the noise detecting means
(3) is arranged at a plurality of locations with respect to one noise source (Sp ) in the space (2) so that the noise in the space (2) can be detected at each location, and the noise detection means The noise signals of (3), (3), ... are added up, and the added noise signal is added to the FIR for noise reduction.
Since the filter (13) and the signal summing means (6) for transmitting to the adaptive algorithm execution means (15) are provided, the noise signals detected by the noise detection means (3), (3), ... Noise components such as vortex sound components are canceled out by the summation in the signal summing means (6), and the signals transmitted to the sound deadening FIR filter (13) and the adaptive algorithm executing means (15) are originally detected. It is possible to avoid only the noise signal generated from the noise source that should be generated, and to prevent the noise reduction performance from being significantly impaired by the eddy-current noise associated with turbulence as in the past. It is possible to improve the silencing performance accompanying the improvement in detection accuracy. In addition, the sound deadening performance can be favorably maintained even when the air flow velocity in the space (2) is high. Furthermore, even if the present device is installed in a place where uneven flow of air is generated, good muffling operation can be obtained. Therefore, it is necessary to install the muffling device near the fan of the air conditioner. Can be feasible. Further, even if one noise detecting means (3) fails, the remaining noise detecting means (3), (3), ... detect appropriate noise, so such a situation The muffling operation can be performed stably even underneath, and the reliability of the system can be improved.

According to the second aspect of the present invention, each noise detecting means (3), (3), ... Is a noise source (S) located in the space (2).
Since they are arranged at the same position with respect to p), it is not necessary to consider the time shift of the noise signal detected by each noise detection means (3), (3), ... It is possible to simplify the configuration of the silencer as a whole, because the circuit and the like are not required.

According to the invention of claim 3, the monitor means
(5) is arranged at a plurality of locations with respect to one noise source (Sp ) in the space (2) so that the reduced sound level at the observation point in the space (2) can be detected at each location, Each monitor means
The signal summing means for summing the output signals of (5), (5), ... And transmitting the summed output signal to the adaptive algorithm executing means (15) is provided. The effect according to the invention can also be obtained on the monitor side. In other words, the output signals from the respective monitor means (5), (5), ... Are canceled by noise components such as eddy current sound components due to the summation by the signal summation means, and the adaptive algorithm execution means.
The signal transmitted to (15) is only the signal of the reduced sound level to be originally detected, and the silencing performance can be improved with the improvement of the detection accuracy of the reduced sound by the monitoring means (5).
In addition, the sound deadening performance can be favorably maintained even when the air flow velocity in the space (2) is high. Furthermore, 1
Even if one of the monitoring means (5) fails, the remaining monitoring means (5), (5), ... Detect the appropriate reduced sound, so the silencing operation is stable even under these circumstances. It is also possible to improve the reliability of the system.

According to the invention described in claim 4, each of the monitor means (5), (5), ... Is a noise source (Sp) located in the space (2).
Since they are arranged at the same position with respect to each other, it is not necessary to consider the time shift of the noise signal detected by each monitor means (5), (5), ... Since the disposition is unnecessary, the structure of the silencer as a whole can be simplified.

According to the fifth aspect of the invention, the tube (3a) in which the noise detecting means (3) and the monitoring means (5) are formed in a cylindrical shape with a bottom and a slit (3c) is formed in part Since the microphone body (3b) is housed in (), the air flowing in the space (2) flows along the outer surface of the tube (3a), so that the space (2 Only the sound that should be detected in () is detected, and the noise due to turbulence is removed. That is, the slit
By (3c), the noise component is canceled and only the signal of the sound to be originally detected is output from the microphone body (3b), and the silencing performance can be further improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a schematic configuration in a state where an active silencer is provided in a duct.

FIG. 3 is a side view showing a detection microphone.

FIG. 4 is a diagram for explaining a noise removal principle of a tube with a slit.

FIG. 5 is a diagram showing an arrangement structure of detection microphones.

FIG. 6 is a partially cutaway perspective view showing the inside of a duct in a modified example.

FIG. 7 is a view corresponding to FIG. 6 in another modification.

FIG. 8 is a view corresponding to FIG. 1 in a conventional example.

9 is a view corresponding to FIG. 2 in a conventional example.

[Explanation of symbols]

(2) Space (3) Detection microphone (noise detection means) (4) Speaker (additional sound source) (5) Monitor microphone (monitor means) (6) Acoustic mixer (signal summing means) (13) Adaptive FIR filter (silence suppression) FIR filter) (15) Algorithm execution unit (adaptive algorithm execution means) (Sp) Noise source

Continuation of front page (51) Int.Cl. ⁷ Identification code FI H04R 3/00 310 G10K 11/16 H (56) Reference JP-A-3-203496 (JP, A) JP-A-62-145998 (JP, A) JP-A-60-20700 (JP, A) Special Table 1-502973 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G10K 11/178 F01N 1/00 F24F 13 / 02 H03H 17/00 601 H03H 21/00 H04R 3/00 310

Claims (5)

(57) [Claims] 1. Located in the space (2) inside the duct (1)
One noise source (Sp), noise detection means (3) that detects noise in the space (2) and outputs a noise signal, and the same phase as the noise signal from the noise detection means (3) in opposite phase. FIR filter for muffling that produces a sound signal with inverted amplitude (13)
And an additional sound source that receives the inverted sound signal generated by the silencing FIR filter (13) and emits the inverted sound to the space (2)
(4), a monitor means (5) arranged at a predetermined observation point in the space (2), which detects a reduced sound level at the observation point and outputs a reduced sound signal as feedback, and the noise detection means (3) Noise signal from the monitor and monitoring means
An adaptive type which inputs the reduced sound signal fed back from (5) and updates the filter coefficient of the silencing FIR filter (13) so as to reduce the sound pressure level around the observation point by the noise signal and the reduced sound signal. Algorithm execution means (15)
In the active muffler having the above, the noise detecting means (3) is arranged at a plurality of locations in the space (2), and the noise in the space (2) can be detected at each location. At the same time, the noise signals of the respective noise detecting means (3), (3), ... Are summed up, and the summed noise signal is added to the silencing FIR filter (13).
And an active muffling device comprising a signal summing means (6) for transmitting to the adaptive algorithm executing means (15). 2. Each noise detecting means (3), (3), ... Is a space (2)
2. The active muffler according to claim 1 , wherein the noise sources (Sp) located at the same position are arranged at the same position. 3. Located in the space (2) inside the duct (1)
One noise source (Sp), noise detection means (3) that detects noise in the space (2) and outputs a noise signal, and the same phase as the noise signal from the noise detection means (3) in opposite phase. FIR filter for muffling that produces a sound signal with inverted amplitude (13)
And an additional sound source that receives the inverted sound signal generated by the silencing FIR filter (13) and emits the inverted sound to the space (2)
(4), a monitor means (5) arranged at a predetermined observation point in the space (2), which detects a reduced sound level at the observation point and outputs a reduced sound signal as feedback, and the noise detection means (3) Noise signal from the monitor and monitoring means
An adaptive type which inputs the reduced sound signal fed back from (5) and updates the filter coefficient of the silencing FIR filter (13) so as to reduce the sound pressure level around the observation point by the noise signal and the reduced sound signal. Algorithm execution means (15)
In the active muffling device including, the monitor means (5) is arranged at a plurality of locations in the space (2), and the reduced sound level at the observation point of the space (2) can be detected at each location. In addition, the output signals of the monitor means (5), (5), ... Are summed, and the summed output signal is used by the adaptive algorithm execution means.
(15) An active silencer, characterized in that it is provided with a signal summing means for transmitting to (15). 4. The monitor means (5), (5), ... Are in the space (2) .
4. The active silencer according to claim 3 , wherein the noise sources (Sp) are located at the same position. 5. Noise detection means (3) and monitoring means (5)
The microphone body (3b) is housed in a tube (3a) which is formed in a cylindrical shape with a bottom and a slit (3c) is formed in a part thereof.
The active silencer according to 2, 3, or 4.