JPH0455612A - Noise reducing device - Google Patents

Abstract

PURPOSE:To perform an efficient reduction in noise in a wide frequency range by a method wherein a sound damping means is made of material having a high thermal resistance and a plurality of porous filters are disposed in the sound dampening means through an air layer. CONSTITUTION:A transmitted heat transmitted from a chimney 1 of high temperature to a speaker box 4 is prohibited from its transmission by a dampening cylinder 9 having a high thermal resistance. Combustion gas A having passed through an opening 5 and entered an initial filter 9b is divided to flow to a grid chamber and further advances to a subsequent air layer 9a while reducing its speed by receiving a surface resistance from a grid wall. At this air layer 9a, flows having passed through each of grids and having different flow speed are merged to each other, mixed to each other and their axial flow speeds are decreased. In addition, the flows are moved toward a speaker 3 and receive a wall surface resistance of the second filter 9b. That is, the combustion gas capable of reaching the speaker 3 receives a resistance action caused by the air layer 9a and the filters 9a and 9b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a noise canceling device for canceling noise generated in a chimney for forcibly exhausting combustion gas.

[Prior Art] Fig. 8 shows a conventional noise canceling device. In the figure, (1) is a chimney, and inside this chimney (1), combustion gas (A) at about 250°C flows. A blower blows air from the inlet side (1a) to the outlet side (1b). (2) is embedded in a through hole in the side wall of the chimney (], ) to reduce the combustion noise inside the chimney (1). A microphone for detecting air noise, (3) a speaker, (4) a speaker box with a speaker (3) open at one end and a diaphragm facing the opening, and (5) a speaker [3].
) to radiate the sound emitted from the chimney (1) into the chimney (1).
The opening provided in the side wall of 1), the speaker box (4) is placed in the chimney (
1) It is fixed to the side wall. The microphone (2) is arranged upstream of the flow of combustion gas (A) with respect to the speaker box (4). (6) is a signal processor that receives the output of the microphone (2), performs frequency analysis on this output, and generates and outputs a signal with an opposite phase to the output;
7) is an audio amplifier that receives the output of the signal processor (6), amplifies the power of the received output, and supplies it to the speaker (3).

The operation will be explained below. The microphone (2) captures the noise such as combustion sound and blower sound transmitted with the combustion gas (A) flowing inside the chimney (1), and releases the noise components caught by the microphone (2) into the white air. A signal processor (6) generates a noise cancellation signal having a phase opposite to that of this noise based on the logic of canceling noise in a frequency band that should not be used. This noise canceling signal is amplified in power by an audio amplifier (7) to the level necessary to cancel the noise inside the chimney (1), and then supplied to the speaker (3), which converts the signal into sound, and the aperture ( This converted sound is radiated into the chimney (1) through the chimney (1) through the chimney (1).
) attenuates the noise flowing inside.

[Problems to be Solved by the Invention] In the conventional noise canceling device configured as described above, 15B is how to maintain the initial performance. In other words, speakers and speaker diaphragms that come into direct contact with high-temperature combustion gas containing solid matter such as soot and chemical components such as NOx and sulfur oxides,
This causes thermal deterioration due to high temperatures, decreased output due to adhesion of solid matter, and chemical deterioration due to reactions with chemical substances.

In addition, in order to deal with noise in a wide frequency band or strong level, large or multiple speakers are generally used. The opening in the side wall becomes larger, which causes the sound radiated into the chimney to be diffused, reducing the silencing effect in principle.On the other hand, a single speaker cannot secure the necessary output energy in a wide frequency band, especially in the bass frequency band. Therefore, there was a problem that the speakers tended to become larger.

The present invention has been made to solve these problems, and it blocks heat, solid substances, and chemical substances from reaching the speaker, and also radiates a high-density energy noise canceler to improve silencing efficiency. It is an object of the present invention to provide a noise canceling device that can efficiently cancel noise in a wide frequency band by increasing the output of a single speaker in the bass frequency band.

[Means for Solving the Problems] A noise canceling device according to the present invention includes a noise detection means for detecting noise inside a chimney, and receives an output signal of the noise detection means and detects noise inside the chimney in opposite phase to the output signal. an anti-phase signal generating means for generating a noise canceling signal for canceling noise; an audio converting means for converting the output signal of the anti-phase signal generating means into audio and radiating the audio into the chimney; comprising a buffer means disposed between the conversion means and the chimney,
This buffering means includes a buffer tube made of a material with high thermal resistance,
This buffer cylinder is made up of a plurality of porous filters placed in front of the sound converting means with air layers interposed between them.

Further, the buffer tube has an acoustic horn structure.

In addition, a resonance tube is attached to the sound conversion means.6 [Function] The buffer tube of the buffer means in the present invention prevents heat conduction from the chimney to the voice conversion means, and also has a plurality of resonance tubes provided inside the buffer tube. The porous filter and the air layer between them remove the heat contained in the combustion gas, solid matter such as soot, and co.
This prevents chemicals such as NOx and sulfur oxides from reaching the audio conversion means. In addition, the acoustic horn-shaped buffer cylinder narrows down the sound emitted from the sound converting means, converts it into high-density acoustic energy, and radiates it into the chimney from the chimney opening. Increase the sound of a frequency band.

[Example] FIG. 1 shows an example of the present invention. In the drawings, the same reference numerals as in the conventional example indicate the same or corresponding parts, so the explanation thereof will be omitted. (8) is a planar buffer with one end fixed to the side wall of the chimney (1) facing the opening (5) provided in the chimney (1), and the other end fixed to the open end side of the speaker box (4). This buffer is a container.

(8) is a buffer cylinder (9) made of a material with high thermal resistance,
An air layer (9a) is sandwiched in this buffer cylinder (9), and a pair of lattice-shaped filters (9b) having a predetermined length in the axial direction are inserted.
) (9b). In addition, the sound emission direction of the speaker (3) and the axial direction of the buffer cylinder (9) and filters (9b) (9b) are made to match, and this axial direction is the same as that of the combustion gas (A) flowing inside the chimney (1). It is set so that it is almost at a right angle. Figure 2 shows the buffer (8
), and as shown in the figure, the inside of the buffer (8) is equipped with lattice filters (9b) (9b).
It has a through hole divided into more sections.

Next, I will explain the operation, but the difference from the conventional example is the buffer (8).
This is the function of the high-temperature combustion gas (A').
The conductive heat transmitted from the chimney (1), which is exposed to high temperature and exposed to high temperature, to the speaker box (4) is prevented from being conducted by the buffer cylinder (9), which has a large thermal resistance. Furthermore, although the high temperature combustion gas (A) and the solid matter and chemical substances contained in this combustion gas try to enter through the filter (9b), the following mechanism prevents their entry. That is, the combustion gas (A) that has entered the first filter (9b) through the opening (5) is divided into individual lattice chambers and proceeds while stalling due to the wall resistance of each lattice wall. This air layer (9a) advances to air Fi (9a)
In this case, the flows having different flow velocities that have passed through the individual grids join together and mix with each other, resulting in a stagnation in a swirling state, and the axial velocity further decreases. In this swirl-like stagnation, the flow that still has an axial velocity component advances further toward the speaker (3), but it also stalls here due to the wall resistance of the second filter (9b). The velocity component in the axial direction is almost gone, that is, the combustion gas that can reach the speaker (3) is absorbed by the air layer (9).
The resistance between a) and the filter (9b) decreases dramatically.

During this process, solid matter becomes unable to float due to its weight and size, and falls one after another, and an air layer (9a
) and the wall resistance of the filters (9b) (9b) will prevent the combustion gas (A) from entering one after another. There is almost no new metabolism, and the amount of heat, solids, chemicals, etc. that reach the speaker (3) is drastically reduced.

By the way, since the axis of the radiation direction of the sound radiated from the speaker (3) and the axis of the holes in the grid of the filter (9b) are made to coincide, the attenuation of the sound radiated by the filter (9b) is negligible.

In addition, if the effect of preventing combustion gas from entering is insufficient with the above configuration, the air layer (9a) and filter (9b)
The effect can be improved by increasing the amount alternately. If it is necessary to further prevent soot from entering, a soot removing filter (10) can be added after the filter (9b) as shown in Figure 3.
may be made of a material with good air permeability and heat resistance, such as wire mesh.

The fourth section is another example of the filter (9b), in which a circular tube shape is used in place of the lattice shape in (a), and a honeycomb shape in (b).

FIG. 5 is a perspective view when cleaning the filter (9b) and soot removing filter (10) of the above embodiment, using a hinge at the joint between the speaker box (4) and the buffer (8), The speaker box (4) is opened using the hinge as a fulcrum, and the interior of the speaker box (4) can be cleaned without having to remove it.

In FIG. 6, which shows another embodiment, the same reference numerals are used to indicate parts that are the same as or correspond to those of the previous embodiment. In this example, two speakers (3) (3) are placed in a speaker box (4), and while maintaining the function of the buffer (8), the buffer (109) is shaped like a horn and the beaker (3) Narrow down the amount of noise cancellation emitted from (3) based on the horn theory, make the acoustic energy highly dense, and radiate it into the chimney (1) from the opening (5) provided in the side wall of the chimney (1). It is something. In addition, a joint part (109C) with a smooth curved surface is formed near the connection part of the horn-shaped buffer tube (109) with the chimney (1), and an opening (5) is formed in the side wall of the chimney (1). ) is provided with a smooth curved surface on the opening edge (5a) to prevent acoustic loss and secondary noise caused by generation of eddies.

By the way, this embodiment aims to improve the noise cancellation efficiency by making the buffer (8) into a horn shape to reduce the area of sound radiated into the chimney (1) and increasing the acoustic energy density. The acoustic energy is not radiated from a large area, but is radiated from a small area in a high density manner, so the amount of noise cancellation is not scattered and the noise cancellation effect is higher. ) (3) For example, although we have explained the example using speakers for high-frequency range and low-frequency range, it goes without saying that the noise cancellation efficiency is improved even when there is one speaker or three or more speakers. be.

FIG. 7 shows another embodiment. In the figures, the same reference numerals are used to indicate parts that are the same as or corresponding to those in the previous embodiment. This embodiment has a cylindrical resonance tube ( 1
2) is installed so that the air in the speaker box (4) and the air mass in the resonance tube (12) resonate based on the Holmhertz principle, and the reproduction bass band frequency of the speaker (3) is It is made to be able to emit more (radiation).

[Effects of the Invention] As described above, according to the present invention, a buffer, which is a buffering means, is provided between a speaker, which is a sound converting means, and a chimney, and this buffer allows heat to be conducted from the chimney to the sound converting means. In addition, the filter and air layer installed inside the buffer prevent the heat of the combustion gas and the solid matter such as soot and chemicals contained in the combustion gas from reaching the voice conversion means. This has the effect of preventing thermal deterioration of the means, reduction in transmission efficiency due to solid matter adhesion, and chemical deterioration due to chemical substances.

Further, by forming the shock absorber into a horn shape, the radiation area for noise cancellation is reduced and acoustic energy is radiated at a high density, thereby increasing the sound deadening effect.

Furthermore, by introducing the resonant structure, the low frequency of the radiated sound can be increased, so that the amount of noise cancellation can be emitted over a wider range, and therefore the silencing effect can be increased.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is an external perspective view of a shock absorber, and FIG. 3 is a configuration diagram showing another embodiment.
Fig. 4 is a plan view of another embodiment of the filter, Fig. 5 is an explanatory diagram showing another embodiment of the buffer, Figs. 6 and 7 are block diagrams of other embodiments, and Fig. 8 is a plan view of another embodiment of the filter. FIG. 2 is a configuration diagram of a conventional example. In the figure, 1... chimney, 2... microphone, 3
...Speaker, 4...Speaker box 1.5
...Aperture, 6...Signal processor, 7...Audio amplifier, 8...Buffer, 10...Soot removal filter,
12... Co-ro, 1 tube, 109... Buffer cylinder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (3)

[Claims] (1) Noise detecting means for detecting noise in the chimney that forcibly exhausts combustion gas, and a noise canceling signal for receiving the output signal of the noise detecting means and having a phase opposite to this output signal to cancel the noise in the chimney. an anti-phase signal generating means for generating a signal, an audio converting means for converting the output signal of the anti-phase signal generating means into audio and emitting the audio into the chimney, and a device between the audio converting means and the chimney. and a buffer means arranged,
This buffering means includes a buffer tube made of a material with high thermal resistance,
A noise canceling device comprising a plurality of porous filters placed inside the buffer cylinder in front of the audio converting means with air layers interposed between them. (2) The noise canceling device according to claim 1, wherein the buffer tube has an acoustic horn structure. (3) The noise canceling device according to claim 1 or claim 2, characterized in that a resonance tube is attached to the sound conversion means.