JP2002082672A - Hybrid muffing device and muffling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid muffling device in which a muffling effect in an all frequency range is obtained by the combination of a passive muffler and an ANC muffler and further reduction in the size of the device is realized. SOLUTION: In the hybrid muffling device which muffles noise that goes through a duct, the ANC muffler is arranged in a front stage and the passive muffler is arranged in a back stage. By constituting the hybrid muffling device so that the ANC muffler muffles noise and then, the passive muffler conducts muffling, the muffling effect in high frequency range by the passive muffler arranged in the back stage is improved in a synergistic manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid silencer and a silencing method for silencing noise by combining different types of silencers.

[0002]

2. Description of the Related Art For example, a passive silencer is used as a passive silencer in order to muffle duct noise such as exhaust gas, ventilation and intake air of an engine power generator and driving noise of various mechanical devices.
2. Description of the Related Art A muffler (hereinafter, referred to as a passive muffler) is generally known and used as an active muffler, and an ANC (Active-Noize-Controler) muffler is used.

[0003] The passive silencer is provided with a sound-absorbing splitter that divides the inside of the duct into a plurality of parts by a sound-absorbing material or the like.
It is known that it is suitable for silencing high-frequency noise.

[0004] The ANC silencer includes a reference microphone for detecting a source sound of noise, an ANC speaker and an ANC control device for radiating sound toward the inside of the duct, an error microphone disposed downstream of the ANC speaker, a speaker amplifier, and the like. The ANC is configured to reduce noise propagating in the duct so that the signal detected by the error microphone is minimized relative to the signal detected by the reference microphone.
The noise reduction is performed by performing a signal processing in the control device and generating a control sound which is an anti-phase wave of the noise from the ANC speaker, and is known to be suitable mainly for a noise reduction in a low-frequency sound range. It should be noted that this type of ANC silencer includes an AN silencer when the object to be silenced is high temperature such as exhaust gas.
In order to protect the C speaker from heat, a speaker cooling fan is appropriately provided.

Conventionally, a passive silencer and an ANC
Silencers such as silencers have been used independently according to noise to be silenced.

[0006]

However, the passive silencer has a problem that the silencing effect in a low-frequency sound range is poor, and if the passive silencer is to be covered, the device becomes very large.

Also, the ANC silencer has a problem that it is impossible to muffle sound in a high frequency range. Furthermore, this species A
The NC silencer requires a fan for cooling the ANC speaker to protect the ANC speaker from heat when the object to be silenced is high temperature such as exhaust gas, so that the whole device becomes large. there were.

[0008] In recent years, a passive silencer has been added to the stage after AN.
A hybrid silencer that can obtain a silencing effect in all frequency ranges by arranging C silencers in series has been studied, but it is difficult to sufficiently reduce the size of the device, and it is difficult to install the device in a small space. There was a problem.

Accordingly, the present invention provides a passive silencer and an AN.
An object of the present invention is to provide a hybrid silencer in which a silencer is combined with a C silencer to obtain a silencing effect in all frequency ranges and further downsizing is possible.

[0010]

Means for Solving the Problems The present invention for solving the problems has the following features.

According to a first aspect of the present invention, in a hybrid silencer for silencing noise passing through a duct, an ANC silencer is arranged in a front stage, and a passive silencer is arranged in a rear stage.
It is characterized in that the low-frequency range is muted by the C silencer and then the high-frequency range is muted by the passive silencer.

Here, in selecting a silencer, 25
It is preferable to select an ANC silencer for noise of 0 Hz band or less and a passive silencer for noise of a frequency exceeding 250 Hz band and a small self-noise according to the target sound volume and the like. .

According to a second aspect of the present invention, the ANC silencer is provided with an ANC speaker which emits sound in response to noise in a duct connected to the duct via an L-shaped pipe having a diameter smaller than that of the duct. It is characterized by having.

Since the pipe is formed in an L-shape and a thin pipe as described above, sound transmission from the ANC speaker to the duct can be secured, and the ANC speaker can be protected from the influence of the radiant heat of the exhaust gas. Particularly, when exhaust gas from an engine generator or a gas turbine generator is at a high temperature, the ANC silencer can be arranged at a position near the generator, which is preferable.

The L-shaped pipe can be applied to a case where a reference microphone and an error microphone are provided, and can similarly protect the microphone from radiant heat.

According to a third aspect of the present invention, a passive silencer is disposed as a primary silencer between a noise source passing through the duct and an ANC silencer.

A fourth invention is characterized in that a reference microphone of the ANC silencer for detecting noise propagating in the duct is arranged near a noise source.

This is because the ANC silencer silences the sound by radiating the control sound from the ANC speaker by calculating the opposite phase wave of the sound detected by the reference microphone in the ANC control device. In order to prevent the noise from being generated, a distance L calculated by multiplying at least the calculation time by the speed of sound is required between the reference microphone and the ANC speaker. It is easy to secure the distance L without increasing the size (lengthening) of the silencer, which is particularly suitable when an existing silencer is provided in the noise source.

According to a fifth aspect of the present invention, as an ANC silencer, 25
An ANC silencer having a silencing effect in a frequency range below the 0 Hz band is selected.

According to a sixth aspect of the present invention, the noise passing through the duct
After the sound is silenced by the NC silencer, the sound is silenced by the passive silencer.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a passive silencer and an ANC
In order to confirm the silencing effect of the silencer, the noise of the source sound shown in Table 1 was silenced by each of the passive silencer and the ANC silencer, and the noise after silencing was measured. FIG. 1 and Table 1 show the results obtained by measuring the sound-muffling effect (noise and sound-muffling volume) with the passive muffler, and FIGS. 2 and 1 show the results obtained by measuring the sound-muffling effect with the ANC muffler. In addition,
The source noise shown in Table 1 is due to the engine generator having an existing passive silencer.

[0022]

[Table 1]

From the figures showing the silencing effect and the results in Table 1, the passive silencer has a poor silencing effect in the low-frequency range, and the ANC silencer is almost impossible to muffle in the high-frequency range. The street's silencing effect was confirmed.

Next, a hybrid silencer was constructed by arranging an ANC silencer in series after the passive silencer, and the noise canceling effect was similarly confirmed for the source noises shown in Table 1. As shown in FIG. 3, it was confirmed that silencing was performed by simply combining the silencing effects of both silencers.

Incidentally, in the hybrid silencer which has been studied so far, ANC is not used due to heat of exhaust gas or the like.
Since it is necessary to protect the configuration of speakers, etc., A
It is considered that it is preferable to arrange the NC silencers in series at an appropriate position at the end of the duct from the downstream of the passive silencer whose temperature is relatively low, and most of them have the lowest temperature due to natural cooling. Located at the exit end.

The applicant has attempted to construct a hybrid silencer by arranging a passive silencer in series after the ANC silencer, and similarly confirms the silencing effect of the noise source shown in Table 1. Was.

Here, an example in which the hybrid silencer according to the embodiment of the present invention is used in the above-described engine power generator will be described with reference to FIGS.

In the figure, reference numeral 1 denotes an engine power generator for generating a sound source of exhaust gas noise, and reference numeral 2 denotes an existing passive silencer provided for silencing the power generator 1 (hereinafter referred to as a primary passive silencer). ), And 3 is a chimney for discharging exhaust gas from the engine power generator 1.

In the figure, reference numeral 4 denotes an ANC silencer connected to the exhaust duct of the primary passive silencer 2, which includes a reference microphone 4a, an error microphone 4b, an ANC speaker 4c, an ANC control device (not shown), and a speaker amplifier (not shown). The noise of exhaust gas discharged from the engine power generation device 1 is detected by the reference microphone 4a, and the ANC control device is configured to minimize the signal of the error microphone 4b with respect to the detected signal. Signal processing is performed, and noise is propagated from the ANC speaker 4c to the noise propagating through the duct 4d, thereby generating a control sound.

In the present embodiment, the reference microphone 4a for detecting the noise of the exhaust gas is provided at the exhaust gas outlet position of the power generator 1 in front of the primary passive silencer 2 near the noise source. In the ANC silencer, the ANC control device calculates the opposite phase wave of the sound detected by the reference microphone and emits the control sound from the ANC speaker. A distance L calculated by multiplying at least the calculation time by the sound speed between the speaker and the speaker is required. In the present embodiment, the reference microphone 4a is provided at the exhaust gas outlet position of the power generation device 1 before the primary passive muffler 2. Since the presence of the primary passive silencer 2 contributes to securing the distance L, the duct extension A
This distance L can be easily ensured without increasing the size (lengthening) of the NC silencer.

When the reference microphone 4a is provided at the position of the exhaust gas outlet of the power generator 1, noise can be detected as a sound spectrum with little attenuation, and the results shown in FIGS. It has been confirmed that the possible frequency range is hardly muted by the passive silencer.
There is no effect on the silencing characteristics of the NC silencer.

In this embodiment, the duct 4d
A pipe 4e connecting the ANC speaker 4c and the ANC speaker 4c is formed of an L-shaped thin tube that is extremely thin with respect to the duct 4d. By making the pipe 4e L-shaped and a thin pipe in this manner, transmission of sound from the ANC speaker 4c to the duct 4d is ensured, and the pipe 4e is removed from the influence of radiant heat of exhaust gas.
Since the C speaker 4c can be protected, the ANC silencer 4 can be disposed in a portion where the exhaust gas has a relatively high temperature, such as in the vicinity of the exhaust gas outlet of the engine generator 1, as described above.

Further, by using such a pipe 4e, the length of the pipe 4e can be shortened, and the ANC speaker 4c can be arranged near the duct 4d to reduce the size of the ANC silencer 4 itself. Since a cooling fan is unnecessary or a small-capacity fan can be used, it is possible to further reduce the size of the apparatus as a whole, and if a cooling fan is unnecessary, no maintenance work is required. This leads to a reduction in maintenance and inspection work.

Further, the reference microphone 4a
Similarly, when providing the error microphone 4b,
Provision of the microphone via a narrow tube enables each microphone to be protected from the influence of radiant heat, and is also employed in the present embodiment.

The diameter, length and the like of the pipe 4e can be appropriately set in consideration of the influence of the radiant heat due to the exhaust gas, the radiated sound, and the like.

These facts not only increase the degree of freedom in designing the layout of the hybrid silencer, but also until now, the ANC silencer has been arranged near the chimney 3 which is the exhaust end due to the influence of radiant heat. However, the installation of the ANC silencer 4 as described above allows the installation to be performed at a location where the installation work can be easily performed, for example, in the vicinity of the engine generator 1. It is also possible to do.

In the figure, reference numeral 5 denotes a passive muffler (hereinafter, referred to as a secondary passive muffler) disposed downstream of the ANC muffler 4, and the ANC muffler 4 and the secondary passive muffler 5 are used in the present embodiment. A hybrid silencer according to the present embodiment is configured. Reference numeral 6 denotes a reducer (tapered pipe joint) for connecting ducts having different diameters.

When the sound source shown in Table 1 was silenced by the hybrid silencer configured as described above, FIG.
And the measurement result shown in Table 1 was obtained. As is clear from the measurement results, compared to a hybrid silencer in which an ANC silencer is arranged in series after a passive silencer, its silencing volume, particularly the silencing volume in the 500 Hz band or higher, is clearly increased, It was confirmed that the silencing effect was improved.

From this measurement result, it is found that reducing the sound energy level in the low-frequency sound range in the noise beforehand improves the muffling effect of the passive muffler in the subsequent stage more than when the passive muffler is used alone. It is thought that it has the effect of causing.

From the above results, in constructing a hybrid silencer, a passive silencer is arranged downstream of the ANC silencer, so that the passive silencer can be used at 500 Hz.
Since the noise reduction effect in the high-frequency range above the band can be synergistically improved, the amount of the noise reduction effect is confirmed by preliminary experiments, etc., and by taking this into account, a passive silencer with a smaller noise reduction effect than the target noise reduction volume is considered. Therefore, it is possible to further reduce the size and cost of the hybrid silencer.

When selecting each muffler, as shown in FIG.
Since almost no silencing effect in the 0 Hz band or lower can be obtained, the main object of silencing in the 250 Hz band or lower is AN.
Select a C silencer and select a passive silencer that has good silencing effect and low self-noise at frequencies exceeding the 250 Hz band, and that is optimal according to the noise, the octave band of the ANC silencer, the target silencing volume, etc. Is preferred.

The arrangement (direction) of the components such as the silencers is not limited to the present embodiment, but can be appropriately set in consideration of the installation conditions and the like. For example, even in the case where an existing primary passive silencer is provided, if it is possible in consideration of installation conditions and the like, an ANC silencer is installed before the primary passive silencer so that the primary passive silencer and the ANC silencer can be installed. Therefore, since the silencing characteristics of the primary passive silencer can be improved, the secondary passive silencer can be further reduced in size when the secondary passive silencer is provided.

Here, the relationship between the frequency f to be silenced by the ANC silencer, the sound speed c, and the duct diameter a can be expressed by the following equation (1). The duct diameter of a indicates the length of one side of the duct when the duct diameter is a square. When an actual duct design or the like is performed, a similar sectional area is calculated based on the calculated value. The duct should be set to a width and height that can be secured.

F = 0.5 c / a (1) From the above equation (1), 250
To mute the frequency range below the Hz band, c
= 340 m / s (normal temperature) and f ≦ 250 Hz, duct diameter a ≦ 0.68 m, and c = 61 when the exhaust gas has a high temperature of 600 ° C. such as in a gas turbine generator.
When f ≦ 250 Hz at 0 m / s (600 ° C.), the duct diameter a ≦ 1.22 m, which indicates that a duct having a diameter of about 0.68 to 1.22 m is required.

For example, in a gas turbine power generator of 4000 kVA, when a duct is designed with an exhaust gas amount of 2500 m ³ / min and a gas flow rate of 10 m / sec, the duct diameter a =
2.0 m is required. And the size of the mounting diameter of the secondary passive silencer will be further expanded on the physique,
A with duct diameter a = 1.22m after the secondary passive silencer
When an NC silencer is arranged, it is necessary to provide a reducer or the like and connect it, and further, in order to connect to an exhaust port of a chimney or the like in a later stage of the ANC silencer, it is necessary to provide a reducer again and expand the pipe. According to the present invention, the exhaust port of the power generator or, if there is an existing passive silencer, the exhaust port of the primary passive silencer or the like having a small diameter before enlarging the duct diameter (for example, in the aforementioned 4000 kVA gas turbine power generator, A about 0.8m x 1.2m) duct
Since the duct of the NC silencer can be connected, the hybrid silencer can be installed with a simple piping configuration and piping work.

Further, in the present embodiment, the noise due to the exhaust gas of the engine power generator has been described. However, the present invention is not limited to this, but can be applied to the exhaust, ventilation, intake, etc. of other noise sources.

Furthermore, particularly when the exhaust gas as a noise source is a high temperature exhaust gas as in a gas turbine generator, for example, a 63 Hz band at 600 ° C. has a longer wavelength and corresponds to an approximately 31.5 Hz band at room temperature. As a result, it is virtually impossible to mute with a passive silencer,
It is preferable to apply the hybrid silencer of the present invention in consideration of the influence of temperature.

[0048]

As described above, according to the present invention, a passive silencer is arranged at the subsequent stage of the ANC silencer to constitute a hybrid silencer, and after the noise is silenced by the ANC silencer, the passive silencer is used. In this way, the passive silencer can synergistically improve the silencing effect of the high frequency range.

If the improvement in the noise reduction effect is confirmed in advance and taken into consideration, a passive noise reduction device having a smaller noise reduction effect than the target noise reduction volume can be selected. , And cost reduction.

Also, the ANC speaker of the ANC silencer is
By connecting to the duct through an L-shaped pipe with a diameter smaller than that of the duct, it is possible to protect the ANC speaker from the effects of exhaust gas heat while ensuring sound transmission from the ANC speaker to the duct. Since the ANC silencer can be arranged without restricting the temperature even in a high temperature part of the exhaust gas, such as in the vicinity of the engine generator, the fan for cooling the ANC speaker can be eliminated or the capacity can be reduced, thereby further reducing the size of the entire device. Is possible.

[Brief description of the drawings]

FIG. 1 is a graph showing a noise reduction characteristic of a passive noise reduction device.

FIG. 2 is a graph showing the noise reduction characteristics of an ANC silencer.

FIG. 3 is a graph showing a noise reduction characteristic of a hybrid noise reduction device in which an ANC muffler is arranged after a passive noise reduction device.

FIG. 4 is a schematic side view of the hybrid noise reduction device according to the embodiment of the present invention.

FIG. 5 is a schematic plan view of an ANC silencer in the hybrid silencer according to the embodiment of the present invention.

FIG. 6 is a graph showing the noise reduction characteristics of the hybrid noise reduction device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power generator 2 ... Primary passive silencer 3 ... Chimney 4 ... ANC silencer 4a ... Reference microphone 4b ... Error microphone 4c ... ANC speaker 4d ... Duct 4e ... Piping 5 ... Secondary passive silencer 6 ... Reducer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G10K 11/16 G10K 11/16 B (72) Inventor Yuichiro Noguchi 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside the company Meidensha (72) Inventor Masaaki Okabe 2-1-1-17 Osaki, Shinagawa-ku, Tokyo F-term inside the company Meidensha 3G004 AA06 BA01 CA00 EA05 3H025 CA01 CB41 5D061 EE11 FF02

Claims (6)

[Claims] 1. A hybrid silencer that silences noise passing through a duct, wherein an ANC silencer is arranged at a front stage, a passive silencer is arranged at a later stage, and the passive silencer is silenced by the ANC silencer. A hybrid silencer characterized by silencing. 2. The ANC muffler according to claim 1, wherein an ANC speaker that emits sound with respect to noise in the duct is provided to be connected to the duct via an L-shaped pipe having a diameter smaller than that of the duct. The hybrid silencer according to claim 1, wherein: 3. The hybrid silencer according to claim 1, wherein a passive silencer is arranged as a primary silencer between a source of noise passing through the duct and an ANC silencer. . 4. A reference microphone of the ANC silencer for detecting noise propagating in the duct is arranged near a noise source.
The hybrid noise reduction device according to claim 1. 5. An ANC having a silencing effect in a frequency range below a 250 Hz band as the ANC silencer.
The hybrid silencer according to any one of claims 1 to 4, wherein a silencer is selected. 6. A silencing method, wherein the noise passing through the duct is silenced by a passive silencer after being silenced by an ANC silencer.