JPH06236190A - Active noise reduction device - Google Patents

Abstract

PURPOSE:To concentrate a noise reduction effect only on an optional position. CONSTITUTION:The noise reduction effect is concentrated only in the vicinity of the selected position by making the output of a measuring sensor 110 set to out of the selected position or in the vicinity of that zero or small with a multiplier 117 based on the selection of a position selector 116 at the time of updating the coefficient of the transfer function of an adaptive FIR filter 105, and operating the adaptive FIR filter 105 and a speaker 109 for reducing only a noise on the selected position or in the vicinity of that.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise reduction device for reducing noise in a closed space.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional active noise reduction device. In FIG. 6, reference numeral 100 is a noise source, 101 is a detection sensor for detecting a signal having a strong correlation with noise, 102 is an amplifier, 103 is a low-pass filter (hereinafter referred to as LPF), 104 is an A / D converter, and 105 is silence The adaptive FIR filter for producing a sound having the same sound pressure and the opposite phase to the noise at the position where is, D / A converter, 107
Is an LPF, 108 is an amplifier, 109 is a speaker, 110
Is a measurement sensor installed at or near the position where the sound is to be silenced, 111 is a speaker 109 to the measurement sensor 110.
Up to the transfer function as a coefficient, 112 is a coefficient updater that updates the coefficient of the adaptive FIR filter 105, 113 is an A / D converter, 114 is an LPF, and 115 is an amplifier that amplifies the output of the measurement sensor 110. is there.

Next, the operation of the above conventional example will be described.
In FIG. 6, the detection sensor 101 detects a signal having a close correlation with the noise output from the noise source 100, and the amplifier 102
The signal is amplified by, the LPF 103 attenuates the frequency component above the cutoff frequency, and the A / D converter 104 converts it into a digital signal. The converted signal is adaptive FIR
The filter 105 converts the sound into a sound having an opposite phase and the same sound pressure at the position to be silenced, and then converted into an analog signal by the D / A converter 106, and the LPF 107
The frequency component above the cut-off frequency is attenuated by and is amplified by the amplifier 108. The amplified signal is output indoors by the speaker 109.

The sum of the noise and the signal output from the speaker 109 is input to the measurement sensor 110 installed near the position where the noise is to be silenced, amplified by the amplifier 115, and the frequency component above the cutoff frequency by the LPF 114. Is attenuated, converted into a digital signal by the A / D converter 113, and becomes one input of the coefficient updater 112.

On the other hand, the digital signal converted by the A / D converter 104 is fed from the speaker 109 to the measurement sensor 110.
The other input of the coefficient updater 112 is passed through the FIR filter 111 whose transfer functions are up to. The coefficient updater 112 calculates and updates the coefficient of the adaptive FIR filter 105 for each sample so that the sound pressure is minimized at the position where the sound is to be silenced.

The coefficient updating formula at this time is, for example, LM
In the S (Least Mean Square) algorithm,

[0007]

[Equation 1]

It is expressed as follows. FIG. 7 shows a case where there are a plurality of noise sources and an attempt is made to reduce noise at a plurality of positions, and is a block diagram showing a configuration of a noise reduction device utilizing the configuration of FIG. 7, the same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. 121 is an adder. The FIR filter 1
The number of 11s and the number of adaptive FIR filters 105 are determined as follows, respectively. That is, the FIR filter uses the transfer function from the speaker 109 to the measurement sensor 110 as a coefficient, and since there are the input signals to the detection sensor 101 corresponding to the number of noise sources, the number thereof is (speaker 109 Number) × (number of measurement sensors 110) ×
(Number of detection sensors 101) Further, since the adaptive FIR filter 105 has a function of converting the signal detected by the detection sensor 101 into a signal to be emitted from the speaker 109,
The number is (number of detection sensors 101) × (number of speakers 109).

As described above, even when there are a plurality of positions where noise is to be silenced in the closed space by the conventional active noise reduction device, the noise is suppressed by updating the coefficient of the adaptive filter 105. can do.

[0010]

However, in the above-mentioned conventional active noise reduction device, in order to uniformly reduce noise at a plurality of positions where noise is to be silenced, for example, a part of the space is used. Even if you want to concentrate the noise reduction effect only at any position, such as when
There is a problem that only noise reduction can be performed uniformly. In particular, if the closed space is a vehicle compartment, the position where the noise reduction effect should be concentrated may differ depending on the usage mode, such as the use of only the driver's seat or the front seat. However, there is a problem in that effective noise reduction cannot be achieved in response to such a change in position.

The present invention solves such a conventional problem, and an object of the present invention is to provide an excellent active noise reduction device capable of concentrating the noise reduction effect only at an arbitrary position.

[0012]

In order to achieve the above object, the present invention updates an adaptive FIR filter that outputs a signal for producing a sound necessary for silencing, and a coefficient of a transfer function of the adaptive FIR filter. A coefficient updater, a position selector for selecting a position near which the noise is to be intensively reduced, and a changing unit for changing a signal level related to the coefficient updating formula based on the selection of the position selector Is.

[0013]

Therefore, according to the present invention, when the coefficient of the transfer function of the adaptive FIR filter is updated based on the selection of the position selector, the level difference is generated between the signal related to the selected position and the other signals. Change the signal level associated with the coefficient update equation as provided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of the first embodiment of the present invention. In FIG. 1, reference numerals 100 to 115 have the same names and functions as those of FIG. 7, and description thereof will be omitted. 116
Are position selectors 117a and 117b are multipliers provided at positions related to the outputs of the measurement sensors 110a and 110b.

Next, the operation of the first embodiment will be described. The operation of reducing noise is the same as in FIG.
Sensor 1 that detects a signal closely related to noise output from 0
01, the amplifier 102 amplifies the signal, and LP
In F103, the frequency component above the cutoff frequency is attenuated, and the A / D converter 104 converts it into a digital signal.
The converted signal is converted by the adaptive FIR filter 105 into a sound having an opposite phase and the same sound pressure at the position to be silenced, and then converted into an analog signal by the D / A converter 106, and cut off by the LPF 107. Frequency components above the frequency are attenuated and amplified by the amplifier 108. The amplified signal is output indoors by the speaker 109.

The sum of the noise and the signal output from the speaker 109 is input to the measurement sensor 110 installed near the position where the noise is to be silenced, amplified by the amplifier 115, and the frequency component above the cutoff frequency by the LPF 114. Is attenuated and converted into a digital signal by the A / D converter 113. The signal digitally converted in this way is set to 1 by the position selector 116.
Alternatively, when two or more positions are selected, the signal level thereof is changed by the multiplier 117 based on the selection, and then the position becomes one input of the coefficient updater 112.

On the other hand, the digital signal converted by the A / D converter 104 passes through the FIR filter 111 and becomes the other input of the coefficient updater 112. Where FIR
From the speaker 109 to the measurement sensor 11
The transfer function up to 0 is used as a coefficient, and the noise source 100
The number of input signals to the detection sensor 101 exists corresponding to the number of (1). Therefore, the number is (number of speakers 109) × (number of measurement sensors 110) ×
(Number of detection sensors 101) is required. Therefore, in FIG. 1, since there are two speakers 109, two measurement sensors 110, and two detection sensors 101, the total number of FIR filters 111 is eight.

Measurement sensor 110 and detection sensor 101
The coefficient updater 1 based on these two input signals from
Reference numeral 12 calculates and updates the coefficient of each adaptive FIR filter 105 for each sample so that the sound pressure is minimized at the position where the sound is to be silenced. Here, since the adaptive FIR filter 105 has a function of converting a signal detected by the detection sensor 101 into a signal to be emitted from the speaker 109, the number thereof is (the number of detection sensors 101) × ( Only the number of speakers 109) is required. Therefore, in FIG. 1, since there are two detection sensors 101 and two speakers 109, a total of four adaptive FIR filters 105 are required.

At this time, the coefficient updating formula in the coefficient updating unit 112 is, for example, LMS (Least Mean).
In the (Square) algorithm, it is expressed as (Equation 1).

Here, as described above, the measurement sensor 110
Multipliers 117a and 117b are provided at positions related to the outputs of a and 110b, respectively, and based on the selection of the position selector 116,

[0021]

[Equation 2]

Among these, the output level of the measurement sensor 110 installed at a position other than the relevant position or its vicinity is calculated by the multiplier 1
It is set to 0 or smaller by 17.

For example, the space in which noise is present is divided into two parts, a front part and a rear part, and the measurement sensor 110 is located in the front part.
a, when the measurement sensor 110b is installed at the rear,
When the front portion is selected by the position selector 116 as the position to be muted, the measurement sensor 110 installed in a portion other than the front portion, that is, in the rear portion, of (Equation 2).
The output level of b is set to 0 or smaller by the multiplier 117b.

As described above, according to the first embodiment,
By changing the output signal level of the measurement sensor 110, a level difference can be provided between the signal related to the position selected by the position selector 116 and the other signals, and the adaptive FIR filter 105 and the speaker 109 are provided.
Can be operated to reduce only the noise at or near the selected position, and the effect of noise reduction can be concentrated.

FIG. 2 shows the configuration of the second embodiment. The second embodiment uses a multiplier as the signal level changing means like the first embodiment, but unlike the position of the multiplier 117 in FIG. 1, the position related to the output of the detection sensor 101. Is provided with a multiplier 118, and the position selector 116 or the multiplier 118 previously specifies a noise source having a strong correlation with the noise at each position to be silenced from the acoustic characteristics in the closed space. . With this configuration, when the correlation between the noise and the noise source is specified by the position selector 116 based on the correlation, by controlling the signal from the position selector 116 to the multiplier 118, When the correlation between the noise and the noise source is specified in the multiplier 118, the multiplier 118 corresponds to the signal of the position selector 116 so that the position selector 116 selects one or more positions. When,

[0026]

[Equation 3]

Of the above, the detection sensor 1 relating to a noise source that is not highly correlated with the noise at or near the selected position
The output of 01 is made 0 or smaller by the multiplier 118. This has the same effect as that of the first embodiment, in particular, the shape of the space is specified, such as in the vehicle interior, and the correlation between the position to be silenced and noise is specified in advance. It is more effective when

FIG. 3 shows the configuration of the third embodiment. The third embodiment uses a multiplier as the signal level changing means like the first embodiment, but unlike the position of the multiplier 117 in FIG. 1, the position related to the output of the FIR filter 111. Is provided with a multiplier 119. With this configuration, the position selector 116
When more than one position is selected,

[0029]

[Equation 4]

Among these, the output of the FIR filter 111 having a coefficient unrelated to the noise at the relevant position or its vicinity can be reduced to 0 or smaller by the multiplier 117, and the same effect as the first embodiment can be obtained.

FIG. 4 shows the configuration of the fourth embodiment. In the fourth embodiment, the multiplier 119 of the third embodiment is
The coefficient replacing device 120 is replaced.

In this embodiment, when one or more positions are selected by the position selector 116, the measurement sensor 1 at or near the corresponding position in (Equation 4) is selected.
The coefficient interchanger 120 interchanges the coefficients of the FIR filter 111 so that the coefficients associated with the measurement sensors 110 other than 10 are reduced to 0 or smaller. As a result, the related coefficients of the FIR filter 111 can be weighted, so that the same effect as the first embodiment can be obtained.

The configurations of the above-mentioned first to fourth embodiments can be arbitrarily used together.

FIG. 5 shows the configuration of the fifth embodiment. The fifth embodiment is a combination of the first and second embodiments. In FIG. 5, reference numerals 100 to 120 are the same as those in FIG. 1 and FIG. Also, 1
Reference numeral 21 denotes an adder, and the number of FIR filters 111 and the number of adaptive FIR filters 105 are determined in the same manner as in the case of FIG. With this configuration, it is possible to more effectively concentrate the noise reduction effect.

In each of the above embodiments, the position selector 116 can be configured by a touch panel or button of a wall surface or car audio, an infrared sensor, a seat belt attachment / detachment sensor, or the like.

[0036]

The present invention is clear from the above embodiment,
Based on the selection of the position selector, by changing the signal level related to the coefficient update formula so as to provide a level difference between the signal related to the selected position and the other signals, any selected This has the effect that the noise reduction effect can be concentrated only on the position.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an active noise reduction device according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram of an active noise reduction device according to a second embodiment of the present invention.

FIG. 3 is a schematic block diagram of an active noise reduction device according to a third embodiment of the present invention.

FIG. 4 is a schematic block diagram of an active noise reduction device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic block diagram of an active noise reduction device according to a fifth embodiment of the present invention.

FIG. 6 is a schematic block diagram of a conventional active noise reduction device.

FIG. 7 is a schematic block diagram of a conventional active noise reduction device that reduces noise at a plurality of positions.

[Explanation of symbols]

 100 Noise Source 101 Detection Sensor 105 Adaptive FIR Filter 109 Speaker 110 Measurement Sensor 111 FIR Filter 112 Coefficient Updater 116 Position Selector 117 Multiplier 118 Multiplier 119 Multiplier 120 Coefficient Swap 121 Adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Miyagawa 4-3-1, Tsunashimahigashi, Kohoku-ku, Yokohama-shi, Kanagawa Matsushita Communication Industrial Co., Ltd.

Claims (1)

[Claims] 1. At least one or more first sensors for detecting a signal having a strong correlation with noise emitted from a noise source, and second sensors installed at a plurality of positions for silencing the noise or in the vicinity thereof, respectively. Emission means for emitting a sound for canceling the noise into the room, and an adaptive FIR filter for producing a transfer function for producing a sound having a phase opposite to that of the noise and having the same sound pressure and outputting a signal to the emission means. This adaptive FI
A coefficient updater for updating the coefficient of the transfer function of the R filter;
A position selector for selecting which position of the plurality of positions to mute is to be focused on for reducing noise, and a changing unit for changing the signal level of the coefficient updating unit based on the selection by the position selector. Active noise reduction device equipped.