JPH08270518A - Active noise control device - Google Patents

Abstract

PURPOSE: To detect each noise frequency at an antinode part of the mode, and to securely radiate the interfering acoustic wave to each frequency and to improve the noise reduction effect by setting the fitting position of a noise detecting sensor, which is to be fitted to a duct of an active noise control device, at a position, to which loops of the mode of each frequency of the noise inside the duct are concentrated. CONSTITUTION: A speaker 14 is fitted to an air cleaner casing 12 fitted to an intake pipe 10 of an internal combustion engine E, and the signal of a noise detecting sensor 15 is input to a controller 16 so as to radiate the interfering sound from the speaker 14. Position (e) of the noise detecting sensor 15 is set at a position, to which antinodes of the mode of each frequency (a), (b), (c) are concentrated. Noise of each frequency is thereby picked up so as to radiate the interfering wave, and the noise reduction effect is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control (hereinafter abbreviated as ANC) device in which a speaker is provided in the middle of a duct through which noise is transmitted, and a sound wave having a phase opposite to that of the noise is output to accelerate the noise.

[0002]

2. Description of the Related Art Conventionally, there is an ANC device attached to an intake duct of an internal combustion engine to reduce noise on the intake side, which is disclosed, for example, in Japanese Utility Model Laid-Open No. 5-106524. FIG. 2 shows one of these methods. An air cleaner 2 is provided in an intake pipe 1 of the internal combustion engine E, and a speaker 4 that emits sound waves is provided in a casing 3 of the air cleaner 2.
The noise signal detected by the noise detection sensor 5 provided on the upstream side of the noise is input to the controller 6, and a sound wave having a phase opposite to the detected noise is radiated from the speaker 4 based on the noise signal, and the noise is reduced and canceled. Is what you are trying to do.

[0003]

In the conventional position of the noise detecting sensor 5, the arrival time of the noise from the position of the sensor 5 to the speaker 4 is longer than the time required from the noise detection to the operation of the speaker 4. Thus, it was set at an appropriate position on the upstream side of noise. At that position, there are modes of each frequency included in the noise that are antinodes like the frequency a, and modes that are deviated from the node or other antinode positions like the frequencies b and c. Therefore, the sound of the frequency a which becomes the antinode is surely detected, but the sounds of the other frequencies are hard to be detected, and the dry wave is hard to be emitted to the sound, and the sound deadening effect is reduced.

[0004]

In the ANC device of the present invention, the position of the noise detection sensor in the duct is set to the position where the antinodes of the modes of each frequency are concentrated.

[0005]

In the ANC device of the present invention, noise detection is performed at the antinode position of each frequency mode, so that the advancing wave corresponding to each frequency can be radiated from the speaker, and the silencing effect becomes great.

[0006]

EXAMPLE FIG. 1 shows an example. In this ANC device, an air cleaner 11 is interposed in an intake pipe 10 provided in an internal combustion engine E, a filter element 13 is housed in a case 12 of the air cleaner 11, and a speaker 14 is mounted. On the other hand, a noise detecting sensor 15 is attached at a position e on the upstream side of the intake pipe 10 relative to the speaker 14, and the controller 16
The noise detection sensor 15 and the speaker 14 are connected to the.

The mounting position e of the noise detecting sensor 15 is such that the noise arrival time to the speaker 14 is longer than the time required from noise detection to noise signal processing in the controller 16, speaker control signal output, and speaker operation. Then, the position is set to the position [FIG. 1, frequencies a, b, and c] where the antinodes of each frequency of noise are concentrated. This position can be determined based on previously measured mode data. Further, if the position of the speaker 14 is also set at a position where the antinodes of each frequency mode are concentrated, the progress is surely performed and the sound deadening effect is further enhanced.

[0008]

According to the present invention, since the position of the noise detecting sensor is set at a position where the antinodes of each frequency mode in the duct are concentrated, a noise signal which surely captures each frequency mode is output. Because it emits sound waves, it has a great sound deadening effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an example.

FIG. 2 is a diagram showing a conventional ANC device.

[Explanation of symbols]

 10 duct 14 speaker 15 noise detection sensor

Claims (1)

[Claims] 1. An active noise control device for providing a speaker in the middle of a duct to radiate a sound wave having a phase opposite to that of a noise to allow the noise to progress, and to mount a noise detecting sensor for controlling the speaker on the duct. The active noise control device is characterized in that the positions of the antinodes of a plurality of noise frequency modes are concentrated.