JPH0844374A - Active type muffler - Google Patents

Abstract

PURPOSE:To remarkably improve a muffling effect in a high frequency band more than that of a conventional one without reducing the muffling effect in a low frequency band in an active type muffler intended so as to actively muffle noise of a noise medium with secondary sound sources. CONSTITUTION:This device is constituted of a first and a second secondary sound sources 41, 43 arranged in secondary sound source rooms 37, 38, a front side microphone 45 arranged at the front of the first secondary sound source 41, a first inversion means 49 inverting an electric signal from the front side microphone 45 to output it to the first secondary sound source 41, an upstream side microphone 51 arranged at the upstream side of the second secondary sound source 43 in a muffling room 35, a delay means 55 delaying an electric signal from the upstream microphone 51 so that a phase difference due to a distance between the second secondary sound source 43 and the upstream side microphone 51 and the phase difference of the second secondary sound source of its own are eliminated and a second inversion means 57 inverting an electric signal delayed with the delay means 55 to output it to the second secondary sound source 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active silencer capable of positively silencing noise of a noise medium by a secondary sound source.

[0002]

2. Description of the Related Art Conventionally, as an active silencer that actively suppresses noise of exhaust gas by a secondary sound source,
For example, Japanese Utility Model Laid-Open No. 6-14420 and Japanese Patent Laid-Open No. 5-11
Those disclosed in Japanese Patent No. 783 and the like are known.

FIG. 8 shows an active silencer of this type. In the figure, reference numeral 11 denotes a silencer body.
The silencer main body 11 is divided by a partition wall 13 to form a silencer chamber 15 and a speaker chamber 17.

An exhaust pipe 19 for circulating the exhaust gas G is opened in the muffler chamber 15. Speaker room 17
A speaker 21, which is a secondary sound source that radiates sound waves, is arranged inside the muffling chamber 15.

In front of the speaker 21 in the muffling room 15,
A microphone 23 is arranged at a distance L ₁ from the speaker 21. The microphone 23 and the speaker 21 are connected via the preamplifier 25 and the inverting circuit 27.

In such an active silencer, the noise of the exhaust gas G is detected by the microphone 23, and the erasing sound having a phase opposite to the detected noise is emitted from the speaker 21, so that the so-called active muffling is performed. Done.

[0007]

However, in such a conventional active silencer, since the speaker 21 and the microphone 23 are separated by the distance L ₁ , the noise is detected by the microphone 23 before the speaker 21. By the time the erasing sound is emitted, as shown in FIG. 9, the distance L ₁
And a mechanical phase delay deg2 peculiar to the speaker 21 occurs from when an electric signal is input to the speaker 21 to when the diaphragm vibrates.
In particular, there is a problem in that it is not possible to obtain a sufficient silencing effect in the high frequency range where the tracking characteristic of the speaker 21 deteriorates.

The inventors of the present invention have conducted extensive studies in order to solve such a conventional problem, and as a result, as shown in FIG. 10, a microphone 23 is arranged upstream of the speaker 21 in the muffling chamber 15, and the microphone 23 is removed. Is delayed by the delay circuit 29 so that the phase delay deg1 caused by the distance L ₁ between the speaker 21 and the microphone 23 and the phase delay deg2 peculiar to the speaker 21 are eliminated, and the electric signal delayed by the delay circuit 29 is delayed. It has been found that by inverting the signal by the inverting circuit 27 and outputting the result to the speaker 21, the silencing effect in the high frequency range can be significantly improved as compared with the conventional case.

That is, in such an active silencer,
A microphone 23 is arranged on the upstream side of the speaker 21.
Therefore, the noise level detected by the microphone 23
Although the phase advances from the phase in front of the speaker 21, the delay circuit
29 of the noise detected by the microphone 23
The phase is the distance L between the speaker 21 and the microphone 23. ₁
And the phase delay peculiar to the speaker 21
This results in the microphone being delayed to compensate for deg2
The noise detected by the Rohon 23 is in front of the speaker 21.
When placed, the erasing sound corresponding to this noise reaches the noise.
However, since noise is silenced, it is possible to muffle noise at high frequencies.
The effect can be greatly improved compared to the conventional one.

FIG. 11 shows a comparison of the silencing characteristics of the conventional active silencer shown in FIG. 8 and the above-mentioned active silencer. The solid line shows the silence volume of the conventional active silencer. , The broken line indicates the volume of the active silencer described above. In the active silencer described above, in particular, 280 Hz to 1000 Hz
It can be seen that the muffling effect in the high frequency range of is significantly improved from the conventional one.

However, the above-described active silencer has a problem that the muffling effect is lower than that of the conventional active silencer in the low frequency range below 280 Hz. The present invention has been made to solve such a conventional problem, and an active silencer capable of significantly improving the silencing effect in the high frequency range without reducing the silencing effect in the low frequency range. The purpose is to provide.

[0012]

According to another aspect of the present invention, there is provided an active muffler, wherein a secondary sound source chamber is formed adjacent to a muffler chamber in which a noise medium is circulated, and the secondary sound source chamber is provided inside the muffler chamber. In an active silencer in which a secondary sound source that emits a sound wave is arranged, first and second secondary sound sources arranged in the secondary sound source chamber, and arranged in front of the first secondary sound source. A front side microphone, a first inverting means for inverting an electric signal from the front side microphone and outputting the inverted electric signal to the first secondary sound source, and an upstream side of the second secondary sound source in the silencing chamber. The upstream microphone and the electric signal from the upstream microphone, the phase delay caused by the distance between the second secondary sound source and the upstream microphone, and the second
And a second inverting means for inverting the electric signal delayed by the delay means and outputting the electric signal to the second secondary sound source. It is a thing.

An active silencer according to a second aspect of the present invention is the active silencer according to the first aspect, wherein the first secondary sound source and the second secondary sound source are arranged at positions facing each other with the silencing chamber as a center. It is a thing.

According to another aspect of the active muffler of the present invention, a secondary sound source chamber is formed adjacent to the noise muffler chamber in which the noise medium is circulated, and a secondary sound source emits sound waves into the muffler chamber. In an active silencer in which a sound source is arranged, first and second secondary sound sources arranged in the secondary sound source room, and the first
A first front side microphone arranged in front of the secondary sound source, and a first inverting means for inverting an electric signal from the first front side microphone and outputting the inverted signal to the first secondary sound source; A second front side microphone arranged in front of the second secondary sound source in the silencing chamber, and upstream of the second secondary sound source in the silencing chamber, and the second secondary sound source and the An upstream microphone arranged at a position that eliminates a phase delay due to the distance from the second front microphone and a phase delay specific to the second secondary sound source; and electricity from the second front microphone. And a second inverting means for inverting the electrical signal added by the adding means and outputting the inverted electrical signal to the second secondary sound source. is there.

The active silencer according to a fourth aspect of the present invention is the active silencer according to the third aspect, wherein the first secondary sound source and the second secondary sound source are arranged at positions facing each other with the silencing chamber as a center. First
The front-side microphone and the second front-side microphone are the same microphone.

[0016]

In the active silencer according to the first aspect, the electric signal from the front microphone arranged in front of the first secondary sound source is inverted by the first inverting means and output to the first secondary sound source. By doing so, an erasing sound is radiated from the first secondary sound source, and the erasing sound mainly eliminates noise in the low frequency range.

Since the upstream microphone is arranged on the upstream side of the second secondary sound source, the phase of the noise detected by this upstream microphone advances from the phase in front of the second secondary sound source. The phase of the noise detected by the upstream microphone by the delay means is the phase delay caused by the distance between the second secondary sound source and the upstream microphone and the second phase.
Of the secondary sound source is compensated for, and as a result, when the noise detected by the upstream microphone is located in front of the second secondary sound source, a noise to be erased corresponding to this noise is generated. The noise is reached, and this erased noise mainly silences noise in the high frequency range.

According to another aspect of the active silencer of the present invention, the first secondary sound source and the second secondary sound source are located opposite to each other with the silencing chamber as the center. In the active silencer according to claim 3, the electric signal from the first front side microphone arranged in front of the first secondary sound source is inverted by the first inverting means and output to the first secondary sound source. By doing so, an erasing sound is radiated from the first secondary sound source, and the erasing sound mainly eliminates noise in the low frequency range.

An electrical signal from an upstream microphone arranged upstream of the second secondary sound source in the muffling chamber,
When the addition means adds the electric signal from the second front side microphone arranged in front of the second secondary sound source,
The phase of the added electrical signal is such that when the noise is located in front of the second secondary sound source, the erased sound corresponding to this noise reaches the noise.

That is, when the second secondary sound source is operated only by the electric signal detected by the second front side microphone arranged in front of the second secondary sound source, the second secondary sound source and the second secondary sound source are operated. The phase delay due to the distance to the front microphone of the second microphone and the phase delay peculiar to the second secondary sound source delay the time when the erased sound corresponding to the noise reaches the noise, but the electric signal of the second front microphone is delayed. In addition, when the electric signals of the upstream microphones are added, the phase detected by the upstream microphones leads the phase in front of the second secondary sound source. When located in front of the second secondary sound source, the phase of the erased sound corresponding to this noise reaches that of the noise, and the erased sound mainly eliminates noise in the high frequency range.

In the active silencer of the fourth aspect, the same microphone is used for the first front microphone and the second front microphone.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of the active silencer of the present invention. In the figure, reference numeral 31 denotes a silencer body.

The silencer body 31 is divided into three parts by partition walls 33 and 34, and a silencer chamber 35 is formed at the center.
Then, first and second speaker chambers 37 and 38 are formed on both sides of the muffling chamber 35.

An exhaust pipe 39 through which the exhaust gas G flows is opened in the muffling chamber 35. In the first speaker room 37, a first speaker 41, which is a first secondary sound source that emits sound waves, is arranged in the muffling room 35.

Further, in the second speaker chamber 38, a second speaker 43 which is a second secondary sound source for radiating sound waves is arranged in the muffling chamber 35. First speaker 41
Is arranged upstream of the second speaker 43, and in front of the first speaker 41, a front microphone 45
Is arranged.

A first inverting circuit 49 is connected to the front microphone 45 via a preamplifier 47. The first inverting circuit 49 inverts the electric signal from the preamplifier 47 and outputs it to the first speaker 41.

However, in this embodiment, the upstream microphone 5 is provided upstream of the second speaker 43 in the muffling chamber 35.
1 is arranged. The arrangement position of the upstream microphone 51 is such that the second speaker 43 and the upstream microphone 5 are arranged.
1 and the phase delay deg1 caused by the distance L ₁ (distance in the central axis direction of the second speaker 43) from the second speaker 43.
The position is such that the phase advances by the phase delay amount added with the inherent phase delay deg2.

A preamplifier 53 is connected to the upstream microphone 51, and an electric signal from the upstream microphone 51 is supplied to the preamplifier 53 by a distance L between the second speaker 43 and the upstream microphone 51. A delay circuit 55 for delaying so as to eliminate the phase delay deg1 caused by ₁ and the phase delay deg2 specific to the second speaker 43 is connected.

The delay circuit 55 is formed of a delay element, a filter and the like. The delay circuit 55 is connected to a second inverting circuit 57 that inverts the electric signal from the delay circuit 55 and outputs the inverted signal to the second speaker 43.

In the active silencer described above, the electric signal from the front microphone 45 arranged in front of the first speaker 41 is inverted by the first inverting circuit 49 and output to the first speaker 41. Allows the first speaker 4
An erasing sound is radiated from 1, and the erasing sound mainly eliminates noise in a low frequency range.

Since the upstream microphone 51 is arranged on the upstream side of the second speaker 43, the phase of the noise detected by the upstream microphone 51 leads the phase in front of the second speaker 43. The phase of the noise detected by the upstream microphone 51 by the delay circuit 55 is the same as that of the second speaker 43 and the upstream microphone 51.
A phase delay deg1 due to the distance L ₁ between, delayed to compensate for the second speaker 43 unique phase lag Deg2, this result, noise detected by the upstream microphone 51 and the second speaker 43 When it is located in front of, the erasing sound corresponding to this noise reaches the noise, and the erasing sound mainly cancels the noise in the high frequency range.

In the above-described active silencer, however, the first speaker 41 mainly silences low-frequency noise, and the second speaker 43 primarily silences high-frequency noise. It is possible to significantly improve the silencing effect in the high frequency range as compared with the conventional one without reducing the silencing effect in the low frequency range.

FIG. 2 shows the muffling characteristics of the above-mentioned active silencer. The solid line shows the muffling volume of the conventional active muffler shown in FIG. 8, and the broken line shows the muffling of the active muffler of this embodiment. The muffling volume is shown, and it can be seen that the muffling effect is improved over almost the entire area.

FIG. 3 shows a second embodiment of the active silencer of the present invention. In this embodiment, the first speaker 41 and the first speaker chamber are provided in the second speaker chamber 38. 37
The 2nd speaker 43 is arrange | positioned inside, and the 1st speaker 41 and the 2nd speaker 43 are arrange | positioned in the position which opposes centering on the muffling room 35. As shown in FIG.

FIG. 4 shows the muffling characteristics of the active muffler of this embodiment. The solid line shows the muffling volume of the conventional active muffler shown in FIG. 8, and the broken line shows the active muffling of this embodiment. The muffling volume of the container is shown, and it can be seen that, as in the first embodiment, the muffling effect is substantially improved over almost the entire area.

In particular, the silencing effect in the low frequency range is significantly improved as compared with the conventional one. In the active silencer of the second embodiment, the first speaker 41 and the second speaker 43 are arranged so as to face each other with the silencer chamber 35 as the center, so that the active silencer is made compact. can do.

FIG. 5 shows a third embodiment of the active silencer of the present invention. In this embodiment, a sound wave is radiated into the silencer chamber 35 in the first speaker chamber 37. A first speaker 41, which is the first secondary sound source, is arranged.

Further, in the second speaker chamber 38, a second speaker 43 which is a second secondary sound source for radiating sound waves is arranged in the muffling chamber 35. First speaker 41
Is arranged on the upstream side of the second speaker 43, and the first front microphone 45 is arranged in front of the first speaker 41.

A first inverting circuit 49 is connected to the first front microphone 45 via a preamplifier 47. The first inverting circuit 49 inverts the electric signal from the preamplifier 47 and outputs it to the first speaker 41.

In this embodiment, however, the second front microphone 61 is arranged in front of the center of the second speaker 43 in the muffling chamber 35. In addition, the upstream microphone 6 is provided on the upstream side of the second speaker 43 in the muffling chamber 35.
3 are arranged.

The upstream microphone 63 has a distance L between the second speaker 43 and the second front microphone 61.
A phase delay deg1 due to _1, the second speaker 43 unique eliminating a phase delay deg2 position, i.e., are arranged from the second front-side microphone 61 at a distance L _2.

The optimum position of this distance L ₂ changes depending on the temperature of the exhaust gas which is a noise medium. For example, the distance L 2 from the second speaker 43 to the second front microphone 61 is L. _{If 1} is 50 mm and the phase delay deg2 peculiar to the second speaker 43 is 0.36 Hz,
The optimum distance is as shown in FIG.

In FIG. 6, the horizontal axis represents the temperature of exhaust gas, and the vertical axis represents the distance L ₂ . In this embodiment, the temperature L _{2 which} the exhaust gas normally has is set as the distance L 2.
In consideration of the temperature of 00 to 300 ° C, 250 mm is set.

In FIG. 5, reference numeral 65 is a preamplifier 6
The electric signal from the second front side microphone 61 through 7 and the upstream side microphone 63 through the preamplifier 69.
It shows an adder circuit for adding the electric signal from the.

The adder circuit 65 includes a second inverting circuit 71.
It is connected to the. The second inverting circuit 71 includes an adding circuit 6
The electric signal from 5 is inverted and output to the second speaker 43.

In the active silencer described above, the first front microphone 4 arranged in front of the first speaker 41 is used.
The electric signal from 5 is inverted by the first inversion circuit 49,
By outputting to the first speaker 41, an erasing sound is radiated from the first speaker 41, and the erasing sound mainly eliminates noise in a low frequency range.

Then, the second speaker 4 in the muffling room 35
When the electric signal from the upstream microphone 63 arranged on the upstream side of 3 and the electric signal from the second front microphone 61 arranged in front of the second speaker 43 are added by the adding circuit 65, the addition is performed. When the noise is positioned in front of the second speaker 43, the phase of the generated electric signal is
The phase is such that the erased sound corresponding to this noise reaches the noise.

That is, when the second speaker 43 is operated only by the electric signal detected by the second front microphone 61 arranged in front of the second speaker 43, the second speaker 43 and the microphone 61 are separated from each other. a phase delay deg1 due to the distance L _1, the second speaker 43 unique phase delay Deg2, although timing is delayed to cancellation sound corresponding to the noise reaches the noise, the electrical signal of the second front-side microphone 61 When the electric signals of the upstream microphone 63 are added, the phase detected by the upstream microphone 63 is ahead of the phase in front of the second speaker 43. 2 speakers 43
When it is positioned in front of, the phase of the erased sound corresponding to this noise reaches the noise, and the second speaker 43
Noise in the high frequency range is mainly silenced by the erase sound from.

Also in the active silencer described above, noise in the low frequency range is mainly suppressed by the first speaker 41, and noise in the high frequency range is mainly detected by the second speaker 43, as in the first embodiment. Since the noise is silenced, the silencing effect in the high frequency range can be significantly improved as compared with the conventional one without reducing the silencing effect in the low frequency range.

FIG. 7 shows a fourth embodiment of the present invention. In this embodiment, the first speaker 41 and the second speaker 43 are located at positions facing each other with the muffling chamber 35 as the center. The first front microphone 45 arranged and shown in FIG.
The same microphone 73 is used for the first front microphone 61 and the second front microphone 61.

In the active silencer of this embodiment, one microphone 73 can be shared by the first front microphone 45 and the second front microphone 61 shown in FIG. The number can be reduced.

In the embodiment described above, the muffling chamber 35
Although the example in which the first speaker 41 is arranged on one side and the second speaker 43 is arranged on the other side has been described, the present invention is not limited to such an embodiment, and for example, the first and third speakers are arranged. In the embodiment, the first and second speakers 41 and 43 may be arranged only on one side of the muffling room.

Further, in the above-mentioned embodiment, an example in which the present invention is applied to reduce exhaust noise of an engine or the like has been described, but the present invention is not limited to such an embodiment. It can be widely applied to reduce noise from circulating noise media.

[0054]

As described above, in the active silencer according to the first aspect of the invention, the low frequency noise is mainly muted by the first speaker and the high frequency noise is mainly muted by the second speaker. Since the sound is muted, the sound deadening effect in the high frequency range can be significantly improved as compared with the conventional one without reducing the sound deadening effect in the low frequency range.

In the active silencer of the second aspect, the first secondary sound source and the second secondary sound source are arranged so as to face each other with the silencing chamber as the center, so that the active silencer is compact. Can be

In the active silencer of the third aspect, the first speaker silences noise in the low frequency range, and the second speaker silences noise in the high frequency range.
It is possible to significantly improve the silencing effect in the high frequency range as compared with the conventional one without reducing the silencing effect in the low frequency range.

In the active silencer of the fourth aspect, since one microphone can be shared by the first front microphone and the second front microphone, the number of microphones can be reduced. There are advantages.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an active silencer of the present invention.

FIG. 2 is an explanatory diagram showing a silencing characteristic of the active silencer of FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the active silencer of the present invention.

4 is an explanatory diagram showing a silencing characteristic of the active silencer of FIG. 3. FIG.

FIG. 5 is a circuit diagram showing a third embodiment of the active silencer of the present invention.

FIG. 6 is an explanatory diagram showing the relationship between temperature and distance L ₂ .

FIG. 7 is a circuit diagram showing a fourth embodiment of the active silencer of the present invention.

FIG. 8 is a circuit diagram showing an example of a conventional active silencer.

FIG. 9 is an explanatory diagram showing a phase delay due to the distance between the secondary sound source and the microphone and a phase delay unique to the secondary sound source.

FIG. 10 is a circuit diagram showing an active silencer previously developed by the present inventors.

11 is an explanatory diagram showing a silencing characteristic of the active silencer of FIG.

[Explanation of symbols]

 31 silencer body 35 silencer room 37 first speaker room 38 second speaker room 41 first speaker 43 second speaker 45 front side microphone 49 first inverting circuit 51, 63 upstream side microphone 55 delay circuit 57, 71 Second Inversion Circuit 61 Second Front Microphone 65 Addition Circuit 73 Microphone

Claims (4)

[Claims] 1. A secondary sound source chamber (37, 38) is formed adjacent to a muffler chamber (35) through which a noise medium is circulated, and the muffler chamber (37, 38) is formed in the secondary sound source chamber (37, 38). 35) An active silencer in which secondary sound sources (41, 43) for radiating sound waves are arranged in the second sound source chamber (37, 38). A sound source (41, 43), a front microphone (45) arranged in front of the first secondary sound source (41), and an electric signal from the front microphone (45) is inverted to reverse the first electric signal. A first inversion means (49) for outputting to a secondary sound source (41) and an upstream microphone (51) arranged upstream of the second secondary sound source (43) in the silencing chamber (35). And the electric signal from the upstream microphone (51) to the second secondary sound source (43). A delay unit (55) for delaying so as to eliminate the phase delay due to the distance from the upstream microphone (51) and the phase delay specific to the second secondary sound source (43); and the delay unit (55). ) And a second inverting means (57) for inverting the delayed electric signal and outputting it to the second secondary sound source (43). 2. The active silencer according to claim 1, wherein the first secondary sound source (41) and the second secondary sound source (43).
Are disposed at positions facing each other with the silencing chamber (35) as a center, the active silencer. 3. A secondary sound source chamber (37, 38) is formed adjacent to a silencing chamber (35) through which a noise medium is circulated, and the silencing chamber (37, 38) is provided in the secondary sound source chamber (37, 38). 35) An active silencer in which secondary sound sources (41, 43) for radiating sound waves are arranged in the second sound source chamber (37, 38). A sound source (41, 43), a first front microphone (45) arranged in front of the first secondary sound source (41), and an electric signal from the first front microphone (45). A first reversing means (49) for reversing and outputting to the first secondary sound source (41); and a first reversing means (49) arranged in front of the second secondary sound source (43) in the silencing chamber (35). 2 front microphones (61)
And the second secondary sound source (43) and the second secondary sound source (43) upstream of the second secondary sound source (43) in the silencing chamber (35).
Upstream microphone (63) arranged at a position that eliminates the phase delay due to the distance from the front microphone (61) of the second secondary sound source (43).
And an addition means (65) for adding the electric signal from the second front microphone (61) and the electric signal from the upstream microphone (63), and the electric signal added by the addition means (65). A second inverting means (71) for inverting a signal and outputting it to the second secondary sound source (43), the active silencer. 4. The active silencer according to claim 3, wherein the first secondary sound source (41) and the second secondary sound source (43).
Are arranged at positions facing each other with the muffling chamber (35) as a center, and the first front microphone (45) and the second front microphone (61) are the same microphone (73). An active silencer characterized by this.