JPH0651784A - Hybrid silencer - Google Patents

Abstract

PURPOSE:To provide the compact silencer constituted by combining both silencers of a passive type and an active type so that a silencing effect is obtd. in the entire frequency region. CONSTITUTION:A sound absorbent splitter 2 extending in the longitudinal direction of a duct 1 to be silenced is inserted within this duct. A speaker 6 for silencing and silencing controller 7 constituting the active silencer are built in the sound absorbent splitter 2. A detecting microphone 4 for the active silencer is embedded into the top of the sound absorbent splitter 2 and an error microphone 5 is disposed in the rear end of the sound absorbent splitter 2. The sound absorbent splitter is constituted withdrawably from the duct 1 along a guide 8 provided in the duct 1. The sounds of the high-frequency region among the noises in the duct 1 are silenced by the sound absorbent splitter 2 and the sounds of the low-frequency region are silenced by the active silencer built in the sound absorbent splitter 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for silencing blower noise and the like transmitted through a duct, and more particularly to a hybrid muffler combining a passive type and an active type.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional hybrid silencer. Reference numeral 1 denotes a duct to be silenced. Inside the duct 1, a passive silencer and an active silencer are arranged in series as shown.

The passive silencer is composed of a sound absorbing splitter 2 which divides the inside of the duct 1 into a plurality of parts in the length direction, and the sound absorbing splitter 2 is formed of a perforated plate 3.

The active silencer comprises a detection microphone 4 attached to the duct 1, an error microphone 5, a silencer speaker 6 and an active silencer control device 7.

The passive silencer mainly silences the high frequency range by the sound absorbing splitter 2, and the active silencer detects the original sound propagating in the duct 1 by the detection microphone 4 and the active silencer 7 In (1), signal processing is performed so that the signal of the error microphone 5 is minimized, and a control sound is generated from the muffling speaker 6 to mute mainly the low frequency range.

Conventionally, passive type and active type silencers have been used individually, or as shown in the figure, both have been arranged in series and used. A passive silencer using a sound absorbing material has a drawback that when used alone, it has a poor sound-reducing effect in the low-frequency range, and if it is attempted to cover it, it becomes a very large-scaled one. There is a drawback in that it is impossible to muffle the high frequency range by using the muffler alone.

Further, if passive and active silencers are arranged in series, a sound reduction effect can be obtained in the entire frequency range, but there is a drawback that the total length of the duct becomes very long.

Further, in the conventional active silencer, a microphone, a control speaker, a controller, etc. are installed on the duct wall. Therefore, when a plurality of active silencers are installed in a large duct, a wasteful space is provided as shown in FIG. There are drawbacks such that S becomes large and the maintenance of the active silencer is difficult.

Further, when a plurality of control speakers are installed, it is necessary to devise so as not to reduce the acoustic radiation efficiency due to mutual interference. Further, it is necessary to consider so that the microphone does not detect the airflow noise and the S / N ratio with the sound wave is deteriorated.

[0010]

DISCLOSURE OF THE INVENTION The present invention combines both passive and active silencers to obtain a silencing effect in the entire frequency range, but does not occupy a wasted space unlike conventional ones. An object is to provide a device. Another object of the present invention is to provide a silencer having a structure in which the microphone does not deteriorate the S / N ratio due to airflow noise.

It is another object of the present invention to provide a silencer that employs a structure in which a plurality of control speakers do not interfere with each other in an active silencer. Another object of the present invention is to provide a silencer having a structure that can be easily disassembled and removed for maintenance.

[0012]

In order to solve the above-mentioned problems, in the present invention, a sound absorbing splitter is inserted into a duct to be muffled to partition the inside of the duct into a plurality of parts, and an active muffling device is constructed in the sound absorbing splitter. Install necessary devices (detection microphone, error microphone, control speaker, muffler control device, amplifier, power supply, etc.).

In order to solve the above-mentioned problems, the present invention has a stagnation point formed by installing one of the microphones at the stagnation point of the head of the sound absorbing splitter and the other microphone with a rectifying plate sandwiching the sound absorbing splitter. Adopted a structure that is installed in the section so that airflow noise does not adversely affect the microphone.

Further, according to the present invention, when a plurality of speakers are installed in the active silencer, a speaker box opened only on one surface of the splitter is provided and the speakers are installed therein in order to avoid interaction between the speakers. Adopt structure. The present invention also employs a structure in which the sound absorbing splitter can be slidably inserted into and taken out from the duct.

[0015]

According to the present invention, by accommodating all the active silencers in the sound absorbing splitter that divides the duct into a plurality of flow paths, a passive silencer effective for high frequency noise can be provided in a compact space. , Active muffling effective for low frequency sound is possible at the same time. As described above, according to the present invention, it is possible to realize a silencing device having a wide silencing effect from low frequencies to high frequencies.

Further, since a sound absorbing splitter is installed in the duct to divide the duct into a plurality of parts in the lengthwise direction, the passage width becomes narrower, and the passive type sound deadening effect per unit length is further increased. have. Further, according to the present invention, when the microphone is installed at the stagnation points before and after the splitter, the noise due to the air flow to the microphone can be reduced, and the silencing limit of the active silencer can be set to a lower level.

Further, in the present invention, when the speaker box is opened only in one direction of the splitter, the plurality of speakers face in the same direction, and the speakers do not interfere with each other so that the generated sound efficiency does not decrease.

Further, in the present invention, when the splitter is constructed in a sliding type, the maintenance of the active silencer becomes easy.

[0019]

EXAMPLES The present invention will be specifically described below based on illustrated examples. In FIG. 1, 1 is a duct to be silenced,
Reference numeral 2 is a sound absorbing splitter that divides the inside of the duct 1 into a plurality of flow paths in the length direction, and is formed by a perforated plate 3. Four
Is a detection microphone embedded in the head portion of the sound absorbing splitter 2 according to the outer shape, and 5 is an error microphone disposed in the rear end portion of the sound absorbing splitter 2.

Further, 6 is a muffling speaker, and 7 is an active muffling control device, both of which are arranged in the sound absorbing splitter 2. As shown in the transverse cross-sectional view of FIG. 2, the sound absorbing splitter 2 is configured to have the same structure as that of the conventional passive silencer with respect to the air flow, and the silencer speaker 6 at the rear,
The silence control device 7 and the error microphone 5 are housed to form an active silencer.

The sound absorbing splitter 2 configured as described above
Has a structure that can be taken in and out of the duct 1 along a guide rail 8 arranged in the duct 1. At the end of the sound absorbing splitter 2, as shown in FIG.
An outlet connected to a control device or the like inside is provided so that the splitter 2 can be attached / detached to / from the wiring on the duct side when the splitter 2 is taken in / out of the duct 1, which facilitates maintenance.

Further, as shown in FIG. 2, the front portion of the sound absorbing splitter 2 in which the detection microphone 4 is embedded and the rear portion of the splitter 2 in which the error microphones 5 are arranged by sandwiching the both sides with the rectifying plates 9 are provided. A so-called stagnation point where there is no air flow in the duct 1 is formed.

Therefore, new turbulence of the air flow generated by the air flow flowing over the microphones 4 and 5 and the pressure fluctuation caused thereby are not generated there. As described above, when the microphone is installed at the stagnation point in the duct, noise due to the air flow is reduced, and the S / N ratio of the microphone is improved.

As shown in FIG. 2, it is more preferable to install a screen 10 or the like at the rear edge of the straightening plate 9 forming the stagnation point so that the air flow does not enter the splitter at that portion.

Although FIG. 1 shows an example in which two muffling speakers 6 are installed, the speaker box is always open in one direction, and an acoustic short circuit occurs between the two speakers 6 to produce a sound. It is designed so that the reflection efficiency of is not reduced.

FIG. 4 shows a plurality of muffling units shown in FIG. 1 installed in a duct having a large cross section. Since the active silencer is completely contained within the splitter, there is no wasted space as found in the prior art device of FIG.

Although the present invention has been described based on the embodiments, it goes without saying that the present invention is not limited to these and various changes may be made within the scope of the present invention. For example, in the illustrated device, the sound absorbing splitter is detachably attached to the duct in order to facilitate maintenance of the sound absorbing splitter. However, when the frequency of maintenance is low, the sound absorbing splitter is fixed in the duct. May be Further, the stagnation point where the microphone is installed may have an appropriate structure other than that shown in the drawing.

[0028]

FIG. 5 shows an example of the silencing effect of the device according to the present invention shown in FIG. When the active noise suppressor (ANC) is not operated, the low frequency component has a poor muffling effect. However, when the active noise suppressor is activated, the low frequency component is largely silenced, and a uniform muffling is obtained over a wide frequency range. I understand.

FIG. 6 shows the relationship between the flow velocity in the duct and the muffling limit value. When the flow velocity increases, the sound pressure level at the muffler outlet cannot be lowered below a certain value due to air flow noise. As in the device according to the present invention, the limit value can be lowered by 10 dB or more by installing the microphone at the stagnation point.

Other effects of the device according to the present invention will be additionally described below. (1) The total length of the duct can be shortened by integrating the passive silencer and the active silencer. (2) All the parts related to the active noise suppressor are installed in the sound absorbing splitter, and the sound absorbing splitter can be pulled out from the duct, which facilitates maintenance and eliminates protrusions attached to the outer wall. Therefore, it is possible to partition the duct without wasting space.

[Brief description of drawings]

FIG. 1 is a perspective view showing a hybrid silencer according to an embodiment of the present invention with a part broken away;

FIG. 2 is a cross-sectional view of the silencer shown in FIG.

FIG. 3 is a partial perspective view showing a state of an end portion of a sound absorbing splitter,

FIG. 4 is a perspective view showing another embodiment of the silencer according to the present invention,

FIG. 5 is a graph showing the noise reduction effect of the silencer according to the present invention,

FIG. 6 is a graph showing the effect of the silencer according to the present invention,

FIG. 7 is a perspective view showing a conventional silencer,

FIG. 8 is a perspective view showing another example of a conventional silencer,

[Explanation of symbols]

 1 Duct 2 Sound Absorption Splitter 3 Perforated Plate 4 Detection Microphone 5 Error Microphone 6 Noise Suppression Speaker 7 Active Noise Reduction Controller 8 Guide Rail 9 Rectifier 10 Screen

Claims (6)

[Claims] 1. A sound absorbing splitter which is arranged in a duct to be silenced and partitions the inside of the duct into a plurality of parts in the longitudinal direction, and a sound which is arranged in the sound absorbing splitter and has a phase opposite to that of the sound to be silenced. A hybrid muffler having an active muffler. 2. A detection microphone in which the active silencer is arranged at one end of the sound absorbing splitter, an error microphone arranged in the other end of the sound absorbing splitter, and the sound absorbing between the both microphones. 2. The hybrid silencer according to claim 1, further comprising a control sound generator that is disposed in the splitter and that emits the sound of the opposite phase. 3. One of the microphones is embedded in a stagnation point portion of a head portion of the sound absorbing splitter, and the other of the microphones is disposed at a stagnation point portion formed by installing a rectifying plate with the sound absorbing splitter interposed therebetween. The hybrid silencer according to claim 2, wherein a microphone in a direction in which a sound wave to be silenced enters is used as the detection microphone. 4. The active muffling device arranged in the sound absorbing splitter has a speaker installed in a speaker box opened only on one side of the sound absorbing splitter. The hybrid silencer described. 5. The hybrid silencer according to claim 1, 2, 3 or 4, wherein the sound absorbing splitter is detachably mounted in a duct to be silenced. 6. A hybrid muffler having a detection microphone at one end and an error microphone at the other end, a sound absorbing porous plate, a muffling speaker, and a muffling control device being incorporated between the both microphones and having a connection outlet. Sound absorption splitter for equipment.