JP2880050B2 - Silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for controlling the noise of a centrifugal blower in a ventilation duct in an air conditioner.

[0002]

2. Description of the Related Art In recent years, an active noise control method has been proposed in which noise from an air conditioner having a blower is output using a digital signal processing technique to output a control sound from a speaker and is silenced in a ventilation duct.

Hereinafter, a conventional silencer will be described with reference to the drawings. FIG. 9 shows a block diagram of a conventional silencer. In FIG. 9, microphones 1a and 1b are first and second noise detectors, 2 is an adaptive filter, 3 is an FIR filter,
4 is an LMS calculator, 5 is a speaker, 7 is an air conditioner body, 8
Is a centrifugal blower having a spiral casing in the air conditioner main body 7, and 9 is a blower duct for guiding air from the air conditioner main body 7 to each room.

[0004] The operation of the thus configured silencer will be described below. FIG. 9 shows a discharge side where the air conditioner main body 7 sends air to each room, and the direction of rotation of the centrifugal blower 8 and the direction of air flow are as indicated by arrows. Therefore, the centrifugal blower 8 that actually causes noise in each room
Is propagated in the air duct 9 in the same direction as the air flows. First, noise generated by the centrifugal blower 8 is radiated from its discharge port into the blower duct 9 and detected by the microphone 1a. Here, the microphone 1a is at a sufficient distance k from the outlet of the centrifugal blower 8 so that the air flow in the blower duct 9 is sufficiently uniform.
(K >> the short side length in the cross section of the air duct). The detection signal is input to the adaptive filter 2 and the FIR filter 3. The noise signal processed by the adaptive filter 2 is transmitted to the speaker 5.
Will be played more. Here, the speaker 5 is the microphone 1
a sufficient distance h from the microphone 1a so as not to oscillate due to the feedback loop between
(Here, as an example of a conventional example, h is set to 350 cm or more). The distance h between the microphone 1a and the speaker 5 can be set irrespective of the long side length and the short side length in the cross section of the air duct. The control sound reproduced by the speaker 5 and the noise radiated from the outlet of the centrifugal blower 8 and transmitted through the ventilation duct 9 are detected by the microphone 1 b and input to the LMS calculator 4. The LMS calculator 4 calculates and updates the coefficient of the adaptive filter 2 based on the detection signal and the output signal from the FIR filter 3.
Here, assuming that the total transfer function from the speaker 5 to the microphone 1b is G, a coefficient g (n) approximating the total transfer function G is set in the FIR filter 3 in advance, and the LMS calculator 4 calculates 1, the coefficient W (n) of the adaptive filter 2 is updated.

[0005]

(Equation 1)

As a result, the adaptive filter 2 operates so as to attenuate noise in the microphone 1b. This method is called the Filtered-x algorithm (reference;
Widrowand S. Stearns, "Adaptive Signal Processing"
(Prentice-Hall, Englewood Cliffs, NJ, 1985)).

[0007]

However, as shown in FIG. 9, in a configuration in which one adaptive filter 2 reproduces a control sound with one speaker 5, the speaker 5
Must generate sufficient sound pressure without distortion within the frequency range of noise control, and in order to reproduce low frequencies sufficiently, it is technically difficult with a small speaker, so a considerably large speaker is required. There are problems such as difficulty in constructing the air duct 9 with respect to the size or weight of the speaker, and an increase in cost.

When the microphone 1b is moved closer to the speaker 5 to improve the low-frequency reproduction capability, the sound wave is not reproduced uniformly in the air duct 9 because only one speaker 5 is provided. Since only a part is detected by the microphone 1b, the operation of the adaptive filter 2 becomes unstable, for example, noise control may be biased in the air duct 9 or noise may be added. On the other hand, if the microphone 1b is installed sufficiently away from the speaker 5 in order to make the reproduced sound of the speaker 5 uniform in the ventilation duct 9, the low-frequency reproduction characteristic of the speaker 5 at the position of the microphone 1b deteriorates, In addition, the length of the air duct 9 becomes longer, and there is a problem in construction.

By the way, if the distance between the microphone 1a and the speaker 5 is shortened in order to shorten the ventilation duct 9, the control sound reproduced by the speaker 5 becomes easy to be detected by the microphone 1a, thereby forming a feedback loop. Easier to do.

Further, as shown in FIG. 9, in the configuration in which the microphone 1a is installed sufficiently away from the discharge port in order to avoid air turbulence near the discharge port of the centrifugal blower 8, control is performed near the air conditioner body 7. When the air duct 9 is branched near the air conditioner main body 7, it cannot be controlled before branching because the air duct 9 cannot be integrated with the air conditioner main body 7. It is necessary to control, and the device becomes large.

In addition, when a general closed-type speaker is used as the speaker 5, the static pressure applied to the speaker 5 in the air duct 9 (when the air pressure in the air duct 9 changes compared to the air pressure outside the air duct 9). Due to the generated pressure), the voice coil of the speaker 5 may be largely deviated from the center of the magnetic gap. At this time, the driving force of the voice coil is distorted, so that there is a problem that the noise cannot be stably controlled or noise is added.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to improve low-frequency reproduction capability while using a low-cost and small-sized speaker to improve a sound-muffling effect, and furthermore, to reduce the noise in a ventilation duct. It is an object of the present invention to obtain a uniform and stable damping effect without deviation of the sound deadening volume, and to realize a stable control operation that does not oscillate even if the ventilation duct is shortened. The second purpose is
The driving force distortion due to the static pressure in the ventilation duct does not occur in the operating state of the speaker. A third object is to ensure a sufficient correlation between the noise detection point and the control point near the centrifugal blower. A fourth object is to be able to detect noise without being affected by wind near a centrifugal blower. A fifth object is that noise can be detected at a control point without being affected by wind.

According to the present invention, the first to fifth objects are achieved, and the noise generated in the air conditioner can be uniformly silenced over the entire frequency range of the noise control, and the bias of the noise control in the ventilation duct can be reduced. Without noise, noise control can be performed stably,
An object of the present invention is to provide a noise reduction device that can obtain good noise reduction characteristics.

[0014]

According to the first aspect of the present invention, in order to achieve the first object, a noise radiated from an air outlet of a centrifugal blower having a spiral casing is connected to the air outlet. A first noise detector for detecting the detected noise in the air duct having a rectangular cross section, an arithmetic unit for processing the detected noise signal, an adaptive filter for adaptively controlling the output of the arithmetic unit, A first digital filter for signal processing of an output, and 2 · m (m is an integer) that reproduces the output of the adaptive filter and is installed at a position farther from the centrifugal blower than the installation position of the first noise detector. (A natural number) speaker, a second digital filter that performs signal processing on the output of the adaptive filter and inputs the result to the arithmetic unit, and is installed in an air duct near the speaker. A second noise detector, the second
And a coefficient calculator for calculating the coefficient of the adaptive filter from the output of the first digital filter and the output of the first digital filter. The first noise detector, the speaker, and the second noise detector Installed in the air duct, the first
Noise detector of the four surfaces that constitute the inner wall of the air duct, the surface of the air flow through the duct is the slowest,
Attached on a center line parallel to the direction in which air flows, the speakers are each a closed speaker system housed in a closed cabinet, all of which reproduce the output of the adaptive filter and form four inner surfaces of an air duct. M is provided on each of two sides perpendicular to the plane on which the second noise detector is installed, and the speakers of each side of the air duct are such that the cones of the speakers on the side of the opposed duct face each other. On each side of the air duct where this speaker is installed, center the speaker cone on the center line parallel to the direction of air flow, and the speaker cabinet surface with the front of the cone constitutes the inner wall of the duct And the second noise detector is configured to detect the air flowing through the duct among the four surfaces forming the inner wall of the air duct. On the surface with the slowest speed, install it on the center line parallel to the direction of air flow, and on the duct section passing through the center of the first opposing speaker cone counted from the centrifugal blower side or on the centrifugal blower It is characterized by being installed at a distant position.

According to a second aspect of the present invention, in order to achieve a second object, in the speaker according to the first aspect, the air pressure in the air duct changes when the air pressure changes compared to the air pressure outside the air duct. Due to the pressure on the speaker cone,
The center of the voice coil is previously displaced from the center of the magnetic gap so that the center of the voice coil is located substantially at the center of the magnetic gap.

According to a third aspect of the present invention, in order to attain the second object, the noise radiated from the air discharge port of the centrifugal blower having the spiral casing has a rectangular cross section connected to the air discharge port. A first noise detector that detects in the air duct, an arithmetic unit that performs signal processing on the detected noise signal, an adaptive filter that adaptively controls an output of the arithmetic unit, and a second unit that performs signal processing on an output of the arithmetic unit. 2 digital filters and 2 · m filters (m is a natural number) installed at a position farther from the centrifugal blower than the installed position of the first noise detector, reproducing the output of the adaptive filter.
Speaker, a second digital filter that performs signal processing on the output of the adaptive filter and inputs the result to the arithmetic unit, a second noise detector installed in an air duct near the speaker, A coefficient calculator for calculating a coefficient of the adaptive filter from an output of the second noise detector and an output of the first digital filter, wherein the first noise detector, the speaker, and the second noise detector are provided. Are installed in the air duct, and the first noise detector is located on the center line parallel to the direction in which the air flows on the surface of the four surfaces forming the inner wall of the air duct, where the flow velocity of the air flowing through the duct is the slowest. The speaker is a bass reflex type speaker system housed in a cabinet having a bass reflex port on the same front as the cone,
All regenerate the output of the adaptive filter, and m are respectively provided on two side surfaces perpendicular to the surface on which the second noise detector is installed among the four surfaces constituting the inner wall of the air duct.
The loudspeakers on each side of the air duct are installed such that the cones of the speakers on the sides of the opposing duct face each other, and on each side of the air duct where the speakers are installed, parallel to the direction in which air flows. The center of the speaker cone and the bass reflex port are aligned on a proper center line, and the speaker cabinet surface having the front surface of the cone is attached so as to form the inner wall of the duct, and the second noise detector forms the inner wall of the air duct. A duct installed on the center line parallel to the direction of air flow on the surface of the four surfaces where the flow velocity of air flowing through the duct is the slowest, and passing through the center of the first opposed speaker cone counted from the centrifugal blower side It is characterized by being installed on a cross section or at a position farther from the centrifugal blower than that.

According to a fourth aspect of the present invention, there is provided a muffler, wherein the speaker according to the first or third aspect is arranged such that a center line of a duct surface on which the first noise detector is installed is positioned. A center line extending along the inner wall to the speaker side, connecting the point at which this center line intersects with the cross section of the duct passing through the center of the first two speaker cones counted from the centrifugal blower side, and the first noise detector Is set at a position whose length is within 300 cm.

According to a fifth aspect of the present invention, in order to achieve a fourth object, the first noise detector according to the first or third aspect is characterized in that the first noise detector has a short duct cross section perpendicular to the direction of air flow. With the side length as N and the air discharge port of the centrifugal blower as the origin,
It is characterized in that it is mounted within the range of N / 2 to 3 · N / 2.

According to a sixth aspect of the present invention, in order to achieve a fourth object, the first noise detector according to the first or third aspect has a short duct cross section perpendicular to a direction in which air flows. The side length is N, and the origin is a point where the curved pipe duct connected to the air discharge port of the centrifugal blower on the side far from the centrifugal blower changes from a curved pipe to a straight pipe, within the range of N / 2 to 3 · N / 2. It is characterized by being attached to.

According to a seventh aspect of the present invention, in order to achieve a fourth object, a blower duct according to the first or third aspect has a duct cross section between the first noise detector and the centrifugal blower. The portion has a plate-shaped porous elastic body.

According to a seventh aspect of the present invention, in order to achieve a fifth object, the air duct according to the first or third aspect is characterized in that the air duct has a curved pipe portion between the first noise detector and the speaker. It is characterized by having.

[0022]

According to the first aspect of the present invention, by using a plurality of speakers, the low-frequency reproduction capability is improved while using low-cost and small-sized speakers. In addition, by installing the speaker and the second noise detector so that the acoustic characteristics in the air duct are symmetrical in the vertical and horizontal directions when viewed from the output of the adaptive filter, the sound volume in the air duct is not biased. Obtain a stable and stable damping effect. Further, the second digital filter and the arithmetic unit prevent the output signal of the adaptive filter reproduced from the speaker from being detected by the first noise detector to form a feedback loop.

According to the second aspect of the present invention, the center of the voice coil is deviated in advance with respect to the center of the magnetic gap so that when the static pressure is applied to the speaker in the air duct, the center of the voice coil is shifted. It comes to the center of the magnetic gap.

According to the third aspect of the present invention, since the speaker is a front bass reflex type, the air pressure in the air duct and the air pressure in the speaker cabinet become equal. According to the configuration of the fourth aspect, the first noise detection point and the control point are brought as close as possible to minimize the disturbance between the first noise detection point and the control point even near the centrifugal blower.

According to the fifth aspect of the present invention, assuming that the short side length of the duct cross section is N, the first noise detection point is mounted within a range of N / 2 to 3 · N / 2 from the discharge port of the centrifugal blower. Thus, the turbulence of the air at the first noise detection point is minimized.

According to the configuration of claim 6, the flow of air is adjusted by the curved pipe duct provided at the discharge port of the centrifugal blower. According to the configuration of claim 7, the turbulence, large vortex or irregular pulsating flow of air near the discharge port of the centrifugal blower is reduced by the porous elastic body provided at the discharge port of the centrifugal blower.

According to the eighth aspect of the present invention, by providing a curved portion between the first noise detection point and the speaker, the flow of air between the first noise detection point and the speaker is adjusted.

[0028]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams of a muffler according to an embodiment of the present invention. FIG. 2 is a diagram of FIG. 1 viewed from above (direction A), and FIG. (B direction). 1 and 2, reference numerals 1a and 1b denote microphones that are first and second noise detectors, 2 denotes an adaptive filter,
3a and 3b are FIR filters as first and second digital filters, 4 is an LMS calculator as a coefficient calculator, 5a and 5b are speakers, 6
Denotes an arithmetic unit, 7 denotes an air conditioner main body, 8 denotes a centrifugal blower in the air conditioner main body 7, 9 denotes an air duct for guiding air from the air conditioner main body 7 to each room, and 10 denotes an outlet of the centrifugal blower. It is a porous elastic body.

The operation of the muffler configured as described above will be described below. 1 and 2 show the discharge side where the air conditioner main body 7 sends air to each room, and the direction of rotation of the centrifugal blower 8 and the direction of air flow are as indicated by arrows. Therefore, the noise generated by the centrifugal blower 8 which is the source of the noise in each room actually propagates in the air duct 9 in the same direction as the direction in which the air flows. First, the noise generated by the centrifugal blower 8 is radiated from its discharge port into the blower duct 9 and detected by the microphone 1a. The detection signal is subtracted from the signal from the FIR filter 3b by the arithmetic unit 6 and input to the adaptive filter 2 and the FIR filter 3a. The noise signal processed by the adaptive filter 2 is input to the FIR filter 3b and the speakers 5a and 5b, and is reproduced from the speakers 5a and 5b. The control sound reproduced by the speakers 5a and 5b and the noise radiated from the outlet of the centrifugal blower 8 and transmitted through the ventilation duct 9 are detected by the microphone 1b and input to the LMS calculator 4.
The LMS calculator 4 calculates and updates the coefficient of the adaptive filter 2 based on the detection signal and the output signal from the FIR filter 3a. Here, assuming that the total transfer function from the speakers 5a and 5b to the microphone 1b is C, FI
A coefficient c (n) approximating the total transfer function C is set in the R filter 3a in advance.
Update the coefficient W (n) of the adaptive filter 2.

[0030]

(Equation 2)

Thus, the adaptive filter 2 operates so as to attenuate noise in the microphone 1b. However, the control sound reproduced by the speakers 5a and 5b travels through the noise duct 9 to reach the microphone 1a, and is again input to the adaptive filter 2 to form a feedback loop, which may cause oscillation. Here, the transfer function from the speakers 5a, 5b to the microphone 1a is approximated to the FIR filter 3b as a coefficient in advance, and the output of the FIR filter 3b is subtracted from the output of the microphone 1a by the arithmetic unit 6, so that the arithmetic unit 6 Speakers 5a, 5 in output
The feedback component transmitted from b to the microphone 1a can be removed. Thereby, the speakers 5a, 5b
The operation of the adaptive filter 2 is stable even when the microphone 1a and the microphone 1a are close to each other.

As described above, the noise of the centrifugal blower 8 is attenuated in the blow duct 9. Next, the microphones 1 a and 1 b and the speakers 5 a and 5
The relationship of b will be described.

FIG. 3 shows an installation position of the microphone 1a in FIG. 1 and FIG. 2, FIG. 3 (a) is a diagram viewed from the front (direction D) of FIG. 1, and FIG. FIG. 3C shows the case of FIG. 1, FIG. 3C shows the case of FIG.
Is a porous elastic body 10 installed at the outlet of the centrifugal blower 8.
Are respectively shown. The microphone 1a is installed on the inner surface of the duct at a distance k from the air discharge port of the centrifugal blower 8 on the center line of the inner surface that is the long side 9a in the cross section of the air duct 9.

Here, paying attention to the flow of air in the blower duct 9, the distance from the discharge port of the centrifugal blower 8 in the conventional example is sufficiently large so that the flow of air is sufficiently uniform. In a range near the discharge port, the flow velocity of the air becomes faster as it is closer to the duct surface 9b and becomes slower as it is closer to the duct surface 9a. On the duct surface 9a having a low flow velocity, the air flow is disturbed when the duct surface 9c is closer to the duct surfaces 9c and 9d from near the center line of the duct surface 9a. Further, in this range, the turbulence of the air becomes large even if the discharge port is too close to or too far from the discharge port. Furthermore, the entire system is reduced in size to reduce the air conditioner body 7
In this case, noise control is performed at a position very close to the air conditioner body 7 with the microphone 1a. Therefore, the length k is set in the range shown in Expression 3, where N is the length of the short side (9c, 9d) in the cross section of the ventilation duct 9, and M is the length of the long side (9a, 9b).

[0035]

(Equation 3)

By setting the length k in the range of the expression 3, the microphone 1a is installed at a position where the turbulence of the air is minimized, and the turbulence of the air flow adversely affects the noise control. Can be minimized, and the noise to be controlled can be detected with good S / N, so that a large volume can be obtained. Further, by installing the porous elastic body 10 at the discharge port of the centrifugal blower 8, large vortices, turbulence or irregular pulsation of air immediately after the discharge port can be attenuated. it can.

FIG. 4 shows the installation positions of the microphone 1b and the speakers 5a and 5b in FIGS. 1 and 2.
4A is a diagram viewed from the front (the direction of D) of FIG. 1, FIG. 4B shows the case of FIG. 1, and FIG. 4C shows the case of FIG. The speakers 5a and 5b are installed so that the center of the speaker cone faces the center lines of the duct surfaces 9d and 9c, respectively, and the microphone 1b connects the centers of the speakers 5a and 5b on the center line of the duct surface 9a. It is installed at a position farther from the air conditioner main body 7 than that position on the line or as shown by a broken line. Accordingly, in FIG. 4A, the speakers 5a, 5
b, the acoustic characteristics in the ventilation duct 9 are vertically symmetrical with respect to a center line s connecting the duct surface 9c and the duct surface 9d, and are left and right with respect to a center line t connecting the duct surface 9a and the duct surface 9b. Is symmetric. From this, the FIR filter 3a
Are also approximated in a form including symmetry, the operation of the adaptive filter 2 is stabilized, and the speakers 5a, 5
Since the control sound is reproduced uniformly in the air duct 9 from b, the inside of the air duct 9 is uniformly silenced. Furthermore, by using two control speakers, the low-frequency reproduction capability can be improved, and a better silencing effect than one can be obtained. Alternatively, if the same effect is sufficient, there is a margin in the capacity per one speaker, so that the control can be performed stably, or the size can be reduced, so that the price can be reduced.

Next, the speakers 5a and 5b are placed at a distance h from the microphone 1a as shown in FIG. Here, the air flow around the outlet of the centrifugal blower 8 is not uniform as described above, so that if the distance h is too long, the noise signal between the noise signal detected by the microphone 1a and the noise signal detected by the microphone 1b is reduced. Is degraded. For this reason, the distance h is set in a range where the correlation between the noise signals of the microphones 1a and 1b does not extremely deteriorate, that is, in a position as close as possible to the centrifugal blower 8 within 300 cm.

By setting the distance h as described above, it is possible to suppress the deterioration of the correlation between the noise signals of the microphone 1a and the microphone 1b, and thereby to obtain a sufficient noise reduction effect. In addition, by performing the noise control at a position very close to the air conditioner main body 7 in this manner, the entire system can be downsized and integrated with the air conditioner main body 7. In addition, the air duct 9 normally branches into several parts and is led to each room. However, even in the case where the air duct 9 branches immediately near the air conditioner main body 7, it can be controlled before branching because it can be downsized. It is not necessary to control in each duct after branching.

The case where two speakers are used has been described above, but the case where the number of speakers is further increased will be described. FIG. 5 shows a case where the number of speakers is six, as viewed from the same viewpoint as in FIG. 2, and each speaker 5a, 5b, 5c, 5
d, 5e and 5f reproduce the output of the adaptive filter 2. The installation position is the same as before, and the cone of the speaker facing the center line of each duct surface is
The distance from the speakers 5a, 5b closest to the air conditioner body 7 to the microphone 1a is h. The microphone 1b is installed on the center line connecting the speakers 5a and 5b or at a position farther from the air conditioner main body 7 than that point as shown by a broken line.
Here, the overall transfer characteristics from the speakers 5a to 5f to the microphone 1b are approximated to the FIR filter 3a as coefficients, and the overall transfer characteristics from the speakers 5a to 5f to the microphone 1a are approximated to the FIR filter 3b. As described above, as in the case of FIGS. 1 and 2, the sound is muted by the microphone 1b, and the reproduction capability in the low frequency range can be further improved by increasing the number of speakers, so that a better muffling effect than in FIGS. 1 and 2 can be obtained. Alternatively, if the same effect is sufficient, the capacity per speaker can be afforded and stable control can be performed, or the size can be reduced and the price per speaker can be reduced.

The loudspeakers 5a to 5f in FIGS. 1 and 2 and in FIG. 5 have been described as sealed speakers. However, the static pressure in the air duct 9 is large, so that the loudspeakers 5a to 5f If the center of the voice coil deviates greatly from the center of the magnetic gap, the driving force of the voice coil is distorted, so that noise control cannot be performed stably or noise is added. To prevent this,
In the speakers 5a to 5f, the center of the voice coil is provided so as to be deviated from the center of the magnetic gap so as to oppose the static pressure in the air duct 9, and when the static pressure is applied, the speakers 5a to 5f are provided. The center of the 5f voice coil is positioned near the center of the magnetic gap. This can prevent noise control from deteriorating due to driving force distortion. Note that FI
The coefficients of the R filters 3a and 3b are transfer functions in a state where a static pressure is applied.

Next, a case where the control speakers 5a and 5b are changed to the front bass reflex type will be described. FIG. 6 is a diagram in which the speakers 5a and 5b in the block diagrams of FIGS. 1 and 2 are replaced with bass reflex speakers 5a and 5b, and corresponds to FIG. In FIG. 6, the method of installing the bass reflex speakers 5a and 5b and the microphone 1b with respect to the duct 9 is the same as before, and
The relationship between a and 5b and the microphone 1b is such that the microphone 1b is on the center line connecting the cones of the bass reflex speaker 5a and the bass reflex speaker 5b. This is the same even when the bass reflex port is closer to the air conditioner body 7. From the above, the same effects as in the case of FIG. 1 and FIG. 2 are obtained. Further, the internal pressure of the speakers 5a, 5b and the pressure in the duct 9 become equal by using the front bass reflex type of the control speakers 5a, 5b. Since the voice coil is located substantially at the center of the magnetic gap, it can be controlled without driving force distortion. In the bass reflex system, the resonance of the bass reflex port is used near the minimum reproduction band, whereby the amplitude of the cone is reduced, so that the nonlinear distortion of the support system supporting the cone can also be prevented.

Next, FIG. 7 shows a case where the air duct 9 has a curved tube portion between the microphone 1a and the centrifugal fan 8 in the case of FIG. By using the curved tube duct 9 in this manner, the direction of air flow can be freely changed, and after the air has passed through the curved tube portion, the portion with a high flow velocity faces the duct surface where the microphone 1a is installed. Since the microphone 1a is further biased toward the surface (9b in FIG. 4), the influence of wind can be reduced, and noise can be detected effectively. Here, the microphone 1 a has a short side length N of a duct cross section perpendicular to the direction in which air flows, and is directly connected to a curved tube duct connected to an air discharge port of the centrifugal blower 8 from a curved tube on a side far from the centrifugal blower 8. With the point that becomes a tube as the origin, N /
It is mounted in the range of 2 to 3 · N / 2. The outlet of the centrifugal blower 8 shown in FIG.
Is installed, but it is not necessary if the effect of the wind can be sufficiently removed only by the curved pipe portion of the discharge port.

Finally, FIG. 8 shows the case of FIG. 1 in which the air duct 9 has a curved portion between the microphone 1a and the speakers 5a and 5b. Here, the distance along the inner wall of the duct 9 from the microphone 1a to the speakers 5a and 5b is h, and other configurations are the same as those in FIG. By using the curved tube duct 9 in this manner, the direction of air flow can be freely changed, and after the air has passed through the curved tube portion, the portion with a high flow velocity faces the duct surface where the microphone 1b is installed. Surface (9b in FIG. 4)
In the microphone 1b, the influence of wind can be reduced. This further improves the noise effect.

[0045]

According to the first aspect of the present invention, by using a plurality of speakers, the low-frequency reproduction capability can be improved while using a low-cost and small-sized speaker, thereby improving the silencing effect, and the output of the adaptive filter can be improved. The speaker and the second noise detector are installed so that the acoustic characteristics in the air duct are symmetrical up, down, left, and right as viewed from above, so that a uniform and stable damping effect can be obtained in the air duct with no uneven sound volume. Further, it is possible to prevent the output signal of the adaptive filter reproduced from the speaker by the second digital filter and the arithmetic unit from being detected by the first noise detector and forming a feedback loop. A stable control operation that does not oscillate even if shortened can be performed.

According to the configuration of claim 2, the same effect as that of claim 1 can be obtained, and the center of the voice coil is previously displaced with respect to the center of the magnetic gap, so that the voice coil can be connected to the speaker in the air duct. When the static pressure is applied, the center of the voice coil can be made to be at the center of the magnetic gap, so that the driving force distortion of the voice coil in the noise control state can be prevented.

According to the third aspect of the invention, the same effect as that of the first aspect is obtained, and the air pressure in the air duct and the air pressure in the speaker cabinet can be equalized by using the front bass reflex type speaker. Even when a static pressure is applied to the speaker in the air duct, the center of the voice coil can be prevented from largely deviating from the center of the magnetic gap, and the driving force distortion of the voice coil in the noise control state can be prevented.

According to the configuration of claim 4, the same effect as that of claim 1 or claim 3 can be obtained, and the first noise detection point and the control point can be made as close as possible, so that even in the vicinity of the centrifugal blower. Since the disturbance between the first noise detection point and the control point can be minimized, the correlation between the first noise detection point and the control point can be sufficiently ensured.

According to the configuration of claim 5, the same effect as in claim 1 or claim 3 can be obtained, and the short side length of the duct cross section is set to N, and the first noise detection point is set to the discharge port of the centrifugal blower. By installing the sensor in the range of from N / 2 to 3 · N / 2, the turbulence of the air at the first noise detection point can be minimized. S / N can be detected well without being affected by disturbance.

According to the structure of claim 6, the same effects as those of claim 1 or claim 3 are obtained, and the flow of air can be adjusted by providing a curved pipe duct at the discharge port of the centrifugal blower. In addition, turbulence, large vortices or irregular pulsations near the discharge port of the centrifugal blower can be reduced, and the first noise detector can detect noise with good S / N without being affected by these.

According to the structure of claim 7, the same effects as those of claim 1 or claim 3 can be obtained. In addition, by providing a porous elastic body at the discharge port of the centrifugal blower, the discharge port of the centrifugal blower can be obtained. Since the turbulence, large eddies or irregular pulsating flow of the nearby air can be reduced, the first noise detector can detect the noise with good S / N without being affected by these.

According to the configuration of claim 8, the same effects as those of claim 1 or claim 3 can be obtained, and further, by providing a curved tube portion between the first noise detection point and the speaker, the first effect can be obtained. Since the air flow between the noise detection point and the speaker can be adjusted, the second noise detector can detect the noise without being affected by the wind.

As described above, the noise generated in the air conditioner can be uniformly silenced over the entire frequency range of the noise control, the noise control can be uniformly silenced in the ventilation duct without bias, and the noise control can be stably performed. As a result, good silencing characteristics can be obtained. As a result, better silencing characteristics can be obtained as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a side view of a silencer according to an embodiment of the present invention.

FIG. 2 is a plan view of the silencer of the embodiment.

FIG. 3 is an enlarged view of the vicinity of a discharge port of the muffler of the embodiment.

FIG. 4 is an enlarged view of the vicinity of a speaker of the muffler of the embodiment.

FIG. 5 is a plan view of a muffler according to another embodiment.

FIG. 6 is an enlarged view of the vicinity of a speaker of the muffler of the embodiment.

FIG. 7 is a side view of a silencer according to still another embodiment.

FIG. 8 is a side view of a silencer according to still another embodiment.

FIG. 9 is a side view of a conventional silencer.

[Explanation of symbols]

 1a, 1b Microphone 2 Adaptive filter 3a, 3b FIR filter 4 LMS calculator 5a-5f Speaker 6 calculator 10 Porous elastic body

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tadashi Tamura 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (72) Inventor Yutaka Taniyama 1006 Kadoma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. Person Tomoe Yano 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-53590 (JP, A) JP-A-4-11515 (JP, A) JP-A-3-3 188799 (JP, A) JP-A-3-188798 (JP, A) JP-A-2-70195 (JP, A) JP-A-63-110612 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G 10K 11/178 F24F 13/02 H03H 17/02 H03H 21/00

Claims (8)

(57) [Claims] 1. A first noise detector for detecting noise radiated from an air discharge port of a centrifugal blower having a spiral casing in a blower duct having a rectangular cross section connected to the air discharge port, and the detected noise. An arithmetic unit for processing a signal, an adaptive filter for adaptively controlling the output of the arithmetic unit, a first digital filter for processing the output of the arithmetic unit, and a first digital filter for reproducing the output of the adaptive filter; 2.m speakers (m is a natural number) installed at a position farther from the centrifugal blower than the installation position of the noise detector and signal processing of the output of the adaptive filter and inputting the result to the arithmetic unit A second digital filter, a second noise detector installed in an air duct near the speaker, an output of the second noise detector and the first digital A first noise detector, a speaker and a second noise detector are installed in an air duct, and the first noise detection is performed by a coefficient calculator for calculating a coefficient of the adaptive filter from an output of the first filter. The vessel is
At least one of the four surfaces constituting the inner wall of the air duct is mounted on a center line parallel to the direction in which the air flows in the surface having the slowest flow velocity of the air flowing through the duct, and each of the speakers is housed in a closed cabinet. A system, all of which reproduces the output of the adaptive filter, and sets m on each of two side surfaces perpendicular to the surface on which the second noise detector is installed among four surfaces constituting the inner wall of the air duct. Then, the speakers on each side of the air duct are installed such that the cones of the speakers on the side of the opposing duct face each other, and on each side of the air duct on which the speakers are installed, on the center line parallel to the direction in which air flows. Align the center of the loudspeaker cone with the loudspeaker, and attach the speaker cabinet with the front of the corn to the inner wall of the duct The second noise detector is installed on a center line parallel to a direction in which air flows on a surface of the four surfaces forming the inner wall of the air duct, where the flow velocity of the air flowing through the duct is the slowest, and A silencer installed on a duct section passing through the center of the cone of the first opposing speaker counted from the center or farther from the centrifugal blower. 2. The speaker according to claim 1, wherein the center of the voice coil is located substantially at the center of the magnetic gap by pressure on the cone of the speaker generated when air pressure in the air duct changes compared to air pressure outside the air duct. 2. The muffler according to claim 1, wherein the center of the voice coil is previously displaced from the center of the magnetic gap. 3. A first noise detector for detecting noise radiated from an air discharge port of a centrifugal blower having a spiral casing in a blower duct having a rectangular cross section connected to the air discharge port, and the detected noise. An arithmetic unit for processing a signal, an adaptive filter for adaptively controlling the output of the arithmetic unit, a first digital filter for processing the output of the arithmetic unit, and a first digital filter for reproducing the output of the adaptive filter; 2.m speakers (m is a natural number) installed at a position farther from the centrifugal blower than the installation position of the noise detector and signal processing of the output of the adaptive filter and inputting the result to the arithmetic unit A second digital filter, a second noise detector installed in an air duct near the speaker, an output of the second noise detector and the first digital A first noise detector, a speaker and a second noise detector are installed in an air duct, and the first noise detection is performed by a coefficient calculator for calculating a coefficient of the adaptive filter from an output of the first filter. The vessel is
Of the four surfaces forming the inner wall of the air duct, the surface where the flow velocity of the air flowing through the duct is the slowest is mounted on the center line parallel to the direction in which the air flows, and the speakers each have a bass reflex port on the same front as the cone. A bass reflex speaker system housed in a cabinet, all of which reproduces the output of the adaptive filter, and which is perpendicular to the surface on which the second noise detector is installed, of the four surfaces constituting the inner wall of the air duct. M speakers on each side, the speakers on each side of the air duct are installed so that the cones of the speakers on the side of the opposing duct face each other, and on each side of the air duct where the speakers are installed, air Center the speaker cone and bass reflex port on a center line parallel to the The cabinet surface is attached so as to form the inner wall of the duct, and the second noise detector is configured such that the air flows on the surface of the four surfaces forming the inner wall of the air duct, where the flow velocity of the air flowing through the duct is the slowest. A silencer installed on a center line parallel to the direction, and installed on a section of a duct passing through the center of the cone of the first opposing speaker counted from the centrifugal blower side or at a position farther from the centrifugal blower than that. 4. A speaker according to claim 1, wherein the center line of the duct surface on which the first noise detector is installed extends to the speaker side along the inner wall, and the center line is counted from the centrifugal blower side for the first two speakers. The length of the center line connecting the point intersecting with the cross section of the duct passing through the center of the cone and the first noise detector is 3
Claim 1 installed at a position within 00 cm
Or the silencer according to any one of claims 3 to 7. 5. A first noise detector, wherein N is a short side length of a cross section of a duct perpendicular to a direction in which air flows, and N / 2 to 3 · N / 2 with an air discharge port of a centrifugal blower as an origin. 4. The muffler according to claim 1, wherein the muffler is mounted within a range. 6. A first noise detector, wherein a short side length of a cross section of a duct perpendicular to a direction in which air flows is N, and a curved pipe duct connected to an air discharge port of a centrifugal blower on a side far from the centrifugal blower. 4. The muffler according to claim 1 or 3, wherein the muffler is mounted within a range of N / 2 to 3 · N / 2 with a point at which a curved pipe becomes a straight pipe. 7. The sound deadening device according to claim 1, wherein the blower duct has a plate-shaped porous elastic body in a duct cross section between the first noise detector and the centrifugal blower. apparatus. 8. The air duct according to claim 1, wherein the air duct has a curved portion between the first noise detector and the speaker.
The silencing device according to any one of the above.