JPH02130099A - Muffling device - Google Patents

Abstract

PURPOSE:To increase a muffling effect even for a small duct by providing a propagating path to propagate with a noise wave and a speaker to generate the muffling wave of the phase reverse to the noise wave and providing a speaker in the propagation path so that the propagation direction of the noise wave and the propagation direction of the muffling wave from a speaker are coincident. CONSTITUTION:A muffling wave 10 is emitted from a speaker 1. At the time of emitting the muffling wave 10, first, the waveform of the noise wave in a duct 90 is detected by a noise wave sensor 31 and this is sent to a muffling wave signal generator 30. In a muffling wave signal generator 30, an electric signal is sent to a magnet 11 of the speaker 1 so that the muffling wave, which becomes the phase reverse to the noise waveform, can be generated from the speaker 1. Consequently, the muffling wave 10 of the phase reverse to the noise wave is emitted from the speaker 10 and the muffling wave 10 is emitted in the same propagation direction as the noise 8 emitted from the duct 90. Thus, both waves mutually join in a subduct 20, both waves are synthesized and the noise wave is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a muffler that attenuates noise waves in a noise wave propagation path such as in an air conditioning duct.

[Prior art]

In factories, office buildings, etc., ducts (transmission) are used.

The air sent out from the exhaust pipe is often accompanied by noise,
Therefore, inside the duct or at the air outlet.

A silencer (also called an active silencer) is provided.

For example, the silencer shown in FIG. 1O has a speaker 91 provided on the side wall of a duct 90 that blows air. The speaker 91 is actuated by a sound damping signal generator 93 and directs a sound damping sound 95 toward the noise waves 8 in the duct 90.
fire. This damping sound wave 95 is a pressure wave having an opposite phase to the noise wave 8 in the duct. Then, the noise is attenuated by the canceling effect of the pressure waves in the duct 90 and the above-mentioned damping waves. Moreover, the above-mentioned speaker is sometimes called an actuator. Note that the reference numeral 92 in the figure is an enclosure box.

Furthermore, the silencer shown in FIGS. 11 and 12 is connected to the duct 9.
Two upper and lower speakers 91 are arranged at the outlet of the duct 9.
This device emits a damping sound wave 95 to the noise wave 8 in the air emitted from the air, and attenuates the noise in the same manner as above.

[Intelligence B to be Solved] However, as mentioned above, the conventional silencer is called an active silencer.

It is used for ducts with relatively large cross-sectional areas, such as building exhaust ducts.

Therefore, when trying to use such a silencer in the duct of a vehicle's air conditioner, such a duct has a small cross-sectional area, so only a small speaker can be used.
Make the speaker smaller.

The power of low-frequency sounds decreases, and the silencing effect cannot be fully exerted. Further, as shown in FIG. 10, when the speaker is attached to the side wall of the duct, the size of the speaker in the flow direction of the duct becomes large, the phase accuracy of high-frequency sound decreases, and the silencing effect decreases.

In view of this problem, the present invention aims to provide a noise reduction device that has a large noise reduction effect even in small ducts such as the ducts of vehicle air conditioners.

[Means for Solving the Problems] The present invention includes a propagation path through which a noise wave propagates, and a speaker that generates a damping sound wave having an opposite phase to the noise wave, and the propagation direction of the damping sound wave and the damping sound wave from the speaker The sound damping device is characterized in that the speaker is disposed within the propagation path so that the propagation direction of the speaker coincides with the propagation direction of the speaker.

What should be noted in the present invention is that the speaker is disposed within the noise wave propagation path so that the propagation direction of the damping sound coincides with the propagation direction of the noise wave.

Therefore, the above-mentioned loudspeaker has two speakers, for example, as shown in FIG.
The duct is provided so as to surround it in a donut shape. Or,
The speaker is provided with a flat diaphragm on the diametrical cross section outside the duct as shown in FIGS. 5 and 6 or 9;
The arrangement is made by providing an in-duct speaker as shown in FIG.

Further, it is preferable that the rear surface of the speaker is an enclosure box.

Further, in front of the two speakers, as shown in FIG. 1, it is preferable to provide a cylindrical subduct that covers the front of the speakers and the duct. The subduct is.

Efficiently combines noise waves and damping waves to achieve the sound damping effect of the − layer.

Further, a sound damping signal generator is connected to the speaker.

Further, it is preferable that the sound damping signal generating device is provided with a noise wave sensor that detects the state of the noise waves, such as the pulsating waveform of the noise waves in the duct. Then, based on the noise waveform detected by the sensor, a sound damping signal is generated in a sound damping signal generator, and the signal is sent to a speaker. Further, it is preferable to provide not only one speaker but a plurality of speakers, such as two or four speakers.

(Function) In the present invention, using the speaker, a damping sound wave having an opposite phase to the noise wave is emitted in the same direction as the propagation direction of the noise wave.Therefore, the emitted damping sound wave is transmitted from inside the duct. It merges with the noise wave that came out.

Both waveforms having opposite phases are combined to reduce noise.

Further, at this time, if the noise waves propagating in the duct can be regarded as plane waves, the damping sound also constitutes a plane wave at the part where it merges with the noise waves, and exhibits a large sound damping effect.

〔effect〕

- According to the two aspects of the present invention as described above, it is possible to provide a muffling device that emits large muffling waves. In addition, it has an excellent sound damping effect by matching the sound waves with the propagation direction of the noise waves, so it can be used in air conditioner ducts, etc.

It can also be applied to small ducts.

〔Example〕

First Embodiment The silencing device of this example will be explained with reference to FIGS. 1 to 4.

As shown in FIGS. 1 and 2, this device is applied to a duct 90 of an automobile air conditioner, and includes a speaker 1 provided near the tip of the duct 90, and a speaker 1 and the tip of the duct 90. It consists of a cylindrical subduct 20 that covers.

As shown in FIG. 2, the speaker 1 has a doughnut-shaped paper cone 12, and has a magnet 11 on the back side of the paper cone 12 for generating sound waves. The magnet 11
is made so that the front and back sides are N and S poles. Then, in the inner hole 13 of the donut-shaped cone paper 12,
The duct 90 is in the inserted state.

Further, as shown in FIG. 1, the magnet 1l is connected to a sound damping signal generator 30. Further, in the duct 90, a noise wave sensor 3I is disposed within the duct 90 on the upstream side of the portion where the speaker 1 is disposed. The noise wave sensor 31 is connected to the sound damping signal generator 30 .

Further, the sub-duct 20 has, at the front, a tip exhaust portion 22 whose inner diameter is slightly larger than that of the duct 90. Further, the subtallite 20 has an enclosure box 21 at the rear that covers between the outer periphery of the speaker 1 and the outer periphery of the duct 90.

However, when using this example device.

A damping sound wave 10 is emitted from a speaker 1. When emitting the damping sound wave 10, first, the noise wave sensor 31 detects the noise in the duct 9.
The waveform of the noise wave in 0 is detected and sent to the sound wave canceling signal generator 30. The sound damping signal generator 30 sends an electric signal to the magnet 11 of the speaker 1 in order to cause the speaker 1 to generate a damping sound having a phase opposite to the noise waveform.

As a result, the speaker 1 emits a damping sound wave 10 having a phase opposite to that of the noise wave.

The damping sound wave 10 is a noise wave 8 emitted from the duct 90.
is emitted in the same propagation direction as. Therefore.

Both waves merge with each other within the subduct 20.

Both waves are combined and the noise wave is reduced.

The reason for this noise wave reduction is not clear, but it is
The explanation can be made as follows using FIG. 4 and FIG. That is, since the wind speed distribution inside the duct 90 is fast in the center and slow near the wall surface, the sound speed of the noise wave is also small, as shown in FIG. 3, but similar to the wind speed, the sound speed is fast in the center. It is considered that the sound velocity is slow near the wall surface, 82. Also, in the duct, whether the cross section of the duct is circular or square, there is a fourth
As shown in the figure, since standing waves 83 are generated in the direction of the cross-sectional area of the duct, the sound pressure distribution within the duct is approximately symmetrical about the central axis. Therefore, in response to the noise wave having a distribution symmetrical to the central axis, the damping sound wave is also emitted in a direction symmetrical to the central axis. Therefore, both waves merge together and are combined into two waves while remaining symmetrical about the center. As a result, it is thought that a great sound-dampening effect can be achieved.

According to this example device as described above, it is possible to provide a silencing device with a large silencing effect.

Second Embodiment The silencing device of this embodiment will be explained with reference to FIGS. 5 and 6.

In this device, a speaker 4 having a doughnut-shaped flat diaphragm 41 is disposed around the outer periphery of a duct 90. The planar diaphragm 41 is made of a honeycomb plate 45 having lattice-shaped holes covered with aluminum foil, as shown in FIG. As shown in FIG. 5, a magnet 43 is placed on the back surface of the flat diaphragm 41, and a voice coil 44 is inserted into the magnet 43. The voice coil 44 is.

The magnet 43 is connected to the flat diaphragm 41 through the frame 42 and attached to the frame 4 on the inner wall of the subduct 20.
Fixed at 6.

A total of four magnets 43 are arranged in pairs with the voice coil 44 on the top, bottom, left and right sides of the flat diaphragm 41. Also,
Each magnet 43 is connected to the sound damping signal generator 30 . An enclosure box 2 is located behind the flat diaphragm 41.
1 will be provided. The rest is the same as the first embodiment.

According to the device of this example, the four magnets 43 are actuated by the electric signal from the sound damping signal generator 30, the voice coil 44 vibrates, and the aluminum foil of the donut-shaped plane diaphragm 41 vibrates, causing the damping. Sound waves 40 are emitted. Therefore, the same effects as in the first embodiment can be obtained.

Third Embodiment The silencing device of this embodiment will be explained with reference to FIGS. 7 and 8.

In this device, the middle of one duct 90 is inflated into an egg shape, and a speaker 5 for emitting a damping sound wave 50 is disposed inside the duct 90. The speaker 5 is provided in an enclosure box 55 having a substantially elliptical cross section in the axial direction. The eight enclosure box 55 is fixed within the duct by a frame 56.

Further, the magnet 52 of the speaker 5 is connected to the sound damping signal generator 30. The rest is the same as the first embodiment.

According to the device of this example, the same effects as those of the first example can be obtained.

Fourth Embodiment A silencer according to this embodiment is shown in FIG. In this example, a flat diaphragm 41 is provided on the outer periphery of the opening of the duct 90. Furthermore, this example is the same as the second example, except that the enclosure box 21 is left and the subducts are removed. The rest is the same as the second embodiment.

In this example, there is no subduct in front of the duct 90 and the plane diaphragm 41, but since the propagation direction of the damping sound 40 by the plane diaphragm 41 is made to match that of the noise wave,
Similar to the second embodiment, it exhibits an excellent silencing effect.

[Brief explanation of the drawing]

1 to 4 show the silencer of the first embodiment; 5. FIG. 1 is a partially cutaway perspective view thereof; FIG. 2 is a sectional view corresponding to FIG. 1;
3 and 4 are explanatory diagrams showing the propagation direction and radial cross section of noise waves, FIGS. 5 and 6 show a silencer of the second embodiment, FIG. 5 is a sectional view thereof, and FIG. The figure is A- in Figure 5.
A sectional view taken along the line A. FIG. 7 and FIG. 8 show a silencer according to a third embodiment. FIG. 7 is a sectional view thereof, FIG. 8 is a sectional view taken along line B-B in FIG. 7, FIG. 9 is a sectional view of the silencer of the fourth embodiment, and FIG.
The figure is a cross-sectional view of a conventional muffler, and FIGS. 11 and 12 are cross-sectional views and side views of other conventional mufflers. 91...Speaker. 50.95. ,,Sound damping subduct sound damping signal generator. noise waves. Duct 1, 4. 5゜20,. 30,. 8. 90...

Claims (1)

[Claims] a propagation path through which a noise wave propagates, and a speaker that generates a damping sound wave having a phase opposite to that of the noise wave; A silencer characterized in that a speaker is disposed within the propagation path.