JP2629410B2 - Noise canceling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention 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 which (1) is a chimney, and a combustion gas (A) at about 250 ° C. is provided inside the chimney (1). Air is blown from the inlet side (1a) to the outlet side (1b) by a blower.
(2) is a microphone embedded in a through hole provided on the side wall of the chimney (1) to detect combustion noise and ventilation noise inside the chimney (1), (3) is a speaker, and (4) is open at one end and has an opening. A speaker box with a speaker (3) facing the diaphragm on the side. (5) is provided on the side wall of the chimney (1) in order to radiate the sound emitted from the speaker (3) into the chimney (1). The opening and the speaker box (4) are fixed to the side wall of the chimney (1) such that the speaker (3) faces the opening (5). The microphone (2) is arranged upstream of the flow of the combustion gas (A) with respect to the speaker box (4). (6) receives the output of the microphone (2), performs a frequency analysis of the output, and generates and outputs a signal having the opposite phase to the signal, and (7) receives the output of the signal processor (6). This is an audio amplifier that amplifies the power of the received output and supplies it to the speaker (3).

The operation will be described below. Noise such as combustion noise and blower noise transmitted along with the combustion gas (A) flowing through the chimney (1) is captured by the microphone (2), and the noise components caught by the microphone (2) are released into the atmosphere. A signal processor (6) generates a noise canceling signal having a phase opposite to that of the noise based on a logic for canceling the noise in a frequency band which is not allowed. The noise canceling signal is amplified by an audio amplifier (7) to a level necessary for canceling the noise in the chimney (1), and supplied to a speaker (3).
The sound is converted by the speaker (3), and the converted sound is radiated into the chimney (1) through the opening (5), thereby attenuating noise flowing through the chimney (1).

[Problems to be Solved by the Invention] In the conventional noise canceling device configured as described above, there is a problem how to maintain the initial performance. That speaker and the speaker diaphragm in direct contact with the solids and NO _x and the combustion gas containing chemical components, such as sulfur oxides, such as soot in the high temperature, thermal degradation due to high temperature, decrease in output due to the adhesion of the solid, Chemical degradation due to reaction with chemical substances occurs.

In general, large or multiple speakers are used to respond to noise in a wide frequency band or high-level noise. The opening provided in the side wall is large, so that the sound radiated into the chimney is diffused and the silencing effect is reduced in principle. On the other hand, a single speaker cannot secure the required output energy in a wide frequency band, especially in a low-temperature frequency band. Therefore, there is a problem that the speaker tends to be large in size.

The present invention has been made in order to solve such a problem, heat, solid substances, and chemical substances reaching the speaker are cut off, and at the same time, high-density energy noise extinction noise is radiated to increase the noise elimination efficiency. It is an object of the present invention to provide a noise canceling device capable of efficiently suppressing noise in a wide frequency band by increasing the output of a single speaker in a low-temperature frequency band.

[Means for Solving the Problems] A noise canceling device according to the present invention comprises: a noise detecting means for detecting noise in a chimney; and an output signal from the noise detecting means, which receives the output signal of the noise detecting means and has a phase opposite to that of the output signal. Anti-phase signal generating means for generating a noise canceling signal for canceling noise, voice converting means for converting an output signal of the anti-phase signal generating means into sound, and radiating the sound into the chimney; A buffer tube made of a material having a large thermal resistance, and a buffer tube made of a material having a high thermal resistance, and a buffer tube inside the buffer tube, which is located on the front surface of the voice conversion device and is air-tight. It is composed of a plurality of porous filters provided via layers.

Further, the buffer cylinder has an acoustic horn structure.

Further, a resonance tube is attached to the sound conversion means.

[Operation] The buffer cylinder of the buffer means in the present invention prevents heat conduction from the chimney to the sound conversion means, and the combustion gas is formed by the plurality of porous filters provided inside the buffer cylinder and the air layer provided therebetween. Solid matter such as heat and soot and CO,
Prevents chemical substances such as CO ₂ , NO _x and sulfur oxides from reaching the sound conversion means. The acoustic horn-shaped buffer cylinder narrows down the sound radiated from the sound conversion means and radiates it into the chimney from the opening of the chimney as high-density acoustic energy. Increase the frequency band sound.

Embodiment FIG. 1 shows an embodiment of the present invention. In the figure, the same reference numerals as those of the conventional example indicate the same or corresponding parts, and thus the description thereof will be omitted. (8) is an opening (5) with one end provided to the chimney (1)
A cylindrical shock absorber fixed to the side wall of the chimney (1) opposite to the other end, and the open end side of the speaker box (4) fixed to the other end. This shock absorber, (8) is a substance having a large thermal resistance. A structure in which the formed buffer cylinder (9) and a pair of lattice-shaped filters (9b) and (9b) having a predetermined length in the axial direction with the air layer (9a) interposed in the buffer cylinder (9). have. Also, the sound emission direction of the speaker (3) matches the axial direction of the shock absorber (9) and the filters (9b) and (9b), and the axial direction is the combustion gas (A) flowing through the chimney (1).
It is set so that it is almost at a right angle. FIG. 2 is a perspective view showing the external appearance of the shock absorber (8). As shown in the figure, the inside of the shock absorber (8) has a lattice filter (9b) (9b).
Has a through hole divided into more sections.

Next, the operation will be described. The difference from the conventional example is the function of the shock absorber (8). The description will focus on this part and the description of the parts common to the conventional example will be omitted. ), The conduction heat transmitted from the hot chimney (1) to the speaker box (4) is blocked by the buffer tube (9) having a large thermal resistance. The high-temperature combustion gas (A) and solids and chemical substances contained in the combustion gas try to enter through the filter (9b), but the entry is prevented by the following mechanism.
That is, the first filter (9b) through the opening (5)
The combustion gas (A) that has entered into the air advances separately into the lattice chambers, and proceeds to the next air layer (9a) while stalling due to the wall resistance of the lattice walls. In this air layer (9a), Since the flows having different flow velocities passing through the individual grids join together, they mix with each other, resulting in a vortex stagnation, and the axial velocity further decreases. In this swirl-like stagnation, the flow still having an axial velocity component proceeds further toward the loudspeaker (3).
Due to the wall resistance in b), the vehicle stalls again, so that the velocity component in the axial direction is almost eliminated, that is, the combustion gas that can reach the speaker (3) is the air layer (9a) and the filters (9b) (9b) And drastically decrease. Also, during this process, the solids cannot float due to their weight and size and fall in order. In addition, the stagnation in the air layer (9a) and the wall resistance of the filters (9b) and (9b) are reduced one after another. And the invasion of the combustion gas (A), which is about to enter, is prevented, so there is almost no new metabolism of the combustion gas (A) here, and the heat, solids, and chemical substances reaching the speaker (3) Etc. will decrease dramatically.

By the way, since the axis of the radiating direction of the sound radiated from the speaker (3) coincides with the through-hole axis of the lattice of the filter (9b), the attenuation of the sound radiated by the filter (9b) is negligible.

If the effect of preventing combustion gas intrusion is insufficient with the above configuration, the effect can be improved by further increasing the number of air layers (9a) and filters (9b) alternately. if,
If it is necessary to further prevent the intrusion of soot, a soot removal filter (10) may be additionally provided after the filter (9b) as shown in FIG. 3. The soot removal filter (10) has air permeability. For example, it may be made of a wire mesh or the like which has good heat resistance.

FIG. 4 shows another embodiment of the filter (9b), in which (a) adopts a cylindrical shape and (b) adopts a honeycomb shape in place of the lattice shape.

FIG. 5 is a perspective view when the filter (9b) and the soot removal filter (10) of the above-described embodiment are cleaned, and a hinge is used for a joint between the speaker box (4) and the shock absorber (8). The speaker box (4) is opened with the hinge number as a fulcrum, so that the inside can be cleaned without removing the speaker box (4).

FIG. 6 shows another embodiment. In the figure, the same reference numerals are used for those which are the same as or correspond to those of the above-described embodiment. In this embodiment, two speakers (3)
(3) The noise canceling sound radiated from the speakers (3) and (3) is arranged in the speaker box (4), and while the function of the shock absorber (8) is maintained, the shock absorber tube (109) is formed in a horn shape. Aperture (5) provided on the side wall of the chimney (1) with a high acoustic energy density based on the horn logic
And radiates into the chimney (1). In the vicinity of the connection between the horn-shaped buffer cylinder (109) and the chimney (1), a joint (109c) having a smooth curved surface is formed and an opening (5) provided on the side wall of the chimney (1). The opening edge (5a) of (1) is provided with a smooth curved surface to prevent sound loss and secondary noise due to generation of eddy current.

By the way, the present embodiment aims to improve the noise canceling efficiency by increasing the acoustic energy density by making the shock absorber (8) horn-shaped and reducing the sound area radiated into the chimney (1). Since the sound energy is radiated from a small area at a high density instead of being radiated from a large area, the noise canceling sound is not diffused and the noise canceling effect is further enhanced. In the present embodiment, an example is described in which two loudspeakers (3) and (3), for example, a loudspeaker for the high frequency range and a loudspeaker for the low frequency range are used. It goes without saying that it improves.

FIG. 7 shows another embodiment. In the drawings, the same reference numerals are used to indicate the same or corresponding parts as in the above-described embodiment. In this embodiment, a cylindrical resonance tube (12) is mounted on the surface of the speaker box (4) on which the speaker (3) is mounted, and the air in the speaker box (4) and the air in the resonance tube (12) are removed. The speaker is configured to resonate with the mass based on the Holm Hertz principle so that the reproduced bass band frequency of the speaker (3) can be radiated more.

[Effects of the Invention] As described above, according to the present invention, a shock absorber as a shock absorber is provided between a speaker as a sound converter and a chimney,
The shock absorber prevents heat from being transmitted from the chimney to the sound converting means.The filter and the air layer provided inside the shock absorber heat the combustion gas, as well as solids such as soot and chemicals contained in the combustion gas. Since the substance or the like is prevented from reaching the sound conversion means, the sound conversion means has an effect of preventing thermal deterioration of the sound conversion means, a decrease in transmission efficiency due to solid matter adhesion, and a chemical deterioration due to chemical substances.

Further, by making the shock absorber a horn shape, the radiation area of the noise canceling sound is reduced and the sound energy is radiated with high density, so that the effect of enhancing the sound suppressing effect can be obtained.

In addition, the introduction of the resonance structure can increase the low-frequency range of the radiated sound, thereby radiating noise in a wider range, thereby increasing the noise reduction effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, FIG. 2 is an external perspective view of a shock absorber, 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 view showing another embodiment of the shock absorber, FIGS. 6 and 7 are configuration diagrams of another embodiment, and FIG. FIG. 9 is a configuration diagram of a conventional example. In the figure, 1 ... chimney, 2 ... microphone, 3 ...
Speaker, 4 ... speaker box, 5 ... opening,
6 ... Signal processor, 7 ... Audio amplifier, 8 ... Buffer, 10 ... Soot filter, 12 ... Resonant tube, 109 ...
It is a buffer cylinder. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

(57) [Claims] 1. A noise detecting means for detecting noise in a chimney for forcibly exhausting combustion gas, and a noise for receiving an output signal of the noise detecting means and canceling the noise in the chimney in an opposite phase to the output signal. Anti-phase signal generating means for generating a cancellation signal;
Voice conversion means for converting the output signal of the antiphase signal generation means into sound and emitting the sound into the chimney; and buffer means arranged between the sound conversion means and the chimney. It is characterized in that the means is constituted by a buffer cylinder made of a material having a large thermal resistance, and a plurality of porous filters located inside the buffer cylinder in front of the sound converting means and installed mutually via an air layer. Noise canceling device. 2. The noise canceling device according to claim 1, wherein said buffer cylinder has an acoustic horn structure. 3. The noise canceling device according to claim 1, wherein a resonance tube is attached to said voice converting means.