JP2006105484A - Noise reduction device and noise reduction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-channel active muffler with the simplest system structure not needing addition of a special element into a duct by designing the duct inlet port shape. <P>SOLUTION: This device comprises, as a hardware setting configuration within a casing, an opening part 2 through which noise comes into the casing 1, the opening part having a dimension capable of considering the noise as active muffling top plane wave; a reference microphone 4 set in the vicinity of the opening part inlet; and an additive sound source speaker 5 located in a position separated from the reference microphone 4 through the wall surface of the casing 1 or separated to the downstream side of the incoming noise within a duct structure connected to the opening part; and an error microphone 6 set on the further downstream side of the noise from the additive sound source speaker 5. This device further comprises an additive sound source speaker system for outputting, based on the signal of the reference microphone 4, a signal by use of an evaluation function minimizing the signal of the error microphone 6 in a control device. The setting range of the error microphone 6 is regulated according to the dimension of the opening part, whereby the noise can be controlled as active muffling plane wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus and a noise reduction method for reducing noise entering an opening, for example, a noise reduction apparatus suitable for use in reducing noise in a wall having an opening or a duct in a ventilation system. And a noise reduction method.

  The noise control for reducing the sound propagated to the duct is supported by making the control arithmetic device multi-channel because an acoustic mode occurs in the duct cross section. However, when the number of channels is increased, it is inevitable that the calculation speed is delayed due to an increase in the load on the calculation device. In addition, a large number of microphones are required to perform high-order mode detection. In this case, the microphone arrangement setting that increases the detection accuracy sufficiently with the simple system and the calculation according to the setting are performed (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  However, these methods require a large number of microphones as described above, so that the installation of the plurality of microphones is not only complicated in terms of space and work but also places a load on the control arithmetic unit. Had brought results.

On the other hand, by reducing the number of microphones, it is possible to save the trouble of installing a plurality of microphones, and to simplify the control arithmetic device, the inside of the duct is shaped so that only plane waves are generated along the direction of airflow. There is a method of dividing (see, for example, Patent Document 4). Since this method divides the inside of the duct, a new problem that complicates duct design, manufacture, and assembly is caused.
Japanese Patent Laid-Open No. 10-274556 Japanese Patent No. 3411772 Japanese Patent No. 3411777 JP-A-11-149289

  As described above, conventionally, since an acoustic mode is generated in the cross section of the duct, a multi-channel system has to be used. In order to avoid this, a single channel system is also being developed. In other words, a partition plate is inserted inside the duct, and the inside is divided into a plurality of slits or cells, thereby forming a duct structure that generates a plane wave in each slit or cell. For this reason, it was necessary to make the duct structure according to the mode shape after accurately grasping the acoustic mode. This duct structure resulted in a complex duct structure.

  The present invention has been made in view of the above, and an object thereof is to provide active silencing that simplifies the duct cross-sectional structure and does not require consideration of the acoustic mode shape.

（ここで、ｋ(=2πf／c ，f ：周波数，c ：音速)は波数、ｎは１≦ｎ≦２の実数）を満足する矩形なる前記開口部の近傍に配置されるレファレンスマイクロフォンと、前記他方側に配置され、前記騒音に付加する付加音を放射させる、付加音源スピーカと、前記他方側に配置され、前記騒音と前記付加音との合成音を検出するエラーマイクロフォンであって、前記壁面とほぼ平行な面内において、縦（ｎ−１）ａ、横（ｎ−１）ｂの矩形で、図心を、前記開口部の図心とほぼ一致させた、エラーマイクロフォン設置範囲に設けられた、エラーマイクロフォンと、前記エラーマイクロフォンで検出する前記合成音の音圧が最小となる評価関数を、前記リファレンスマイクロフォンで検出した騒音の音圧を基にして、演算すると共に、付加音源スピーカ用の付加音信号を生成する、制御装置と、を備えるものとして構成される。 The present invention is a noise reduction device for reducing the level of noise when one side of a wall surface having an opening enters the other side from the opening, and has a vertical a, a horizontal b,

(Where k (= 2πf / c, f: frequency, c: speed of sound) is a wave number, n is a real number satisfying 1 ≦ n ≦ 2), and a reference microphone arranged in the vicinity of the rectangular opening, An additional sound source speaker disposed on the other side for radiating additional sound added to the noise, and an error microphone disposed on the other side for detecting a synthesized sound of the noise and the additional sound, In a plane substantially parallel to the wall surface, a rectangular (vertical (n-1) a, horizontal (n-1) b) is provided in the error microphone installation range in which the centroid substantially coincides with the centroid of the opening. The error microphone and the evaluation function that minimizes the sound pressure of the synthesized sound detected by the error microphone are calculated based on the sound pressure of the noise detected by the reference microphone, and the additional sound source speaker And a control device for generating an additional sound signal for power.

（ここで、ｋ(=2πf／c ，f ：周波数，c ：音速)は波数、ｎは１≦ｎ≦２の実数）を満足する複数の矩形のセル単位が横に並んだものとして構成される前記開口部における、前記セル単位毎に配置されるレファレンスマイクロフォンと、前記セル単位毎において、前記他方側に配置され、前記騒音に付加する付加音を放射させる、付加音源スピーカと、前記セル単位毎において、前記他方側に配置され、前記騒音と前記付加音との合成音を検出するエラーマイクロフォンであって、前記壁面とほぼ平行な面内において、縦（ｎ−１）ａ、横（ｎ−１）ｂの矩形で、図心を、前記セル単位の図心とほぼ一致させた、エラーマイクロフォン設置範囲に設けられた、エラーマイクロフォンと、前記セル単位毎において、前記各エラーマイクロフォンで検出する前記合成音の音圧が最小となる評価関数を、前記各リファレンスマイクロフォンで検出した騒音の音圧を基にして、演算すると共に、付加音源スピーカ用の付加音信号を生成する、制御装置と、を備えるものとして構成される。 Furthermore, the present invention is a noise reduction device that reduces the level of noise from one side of a wall surface having an opening to enter the other side from the opening, and has a vertical a, a horizontal b,

(Where k (= 2πf / c, f: frequency, c: speed of sound) is a wave number, and n is a real number of 1 ≦ n ≦ 2). A reference microphone disposed in each cell unit in the opening, an additional sound source speaker disposed on the other side in each cell unit, and radiating additional sound added to the noise, and the cell unit An error microphone that is arranged on the other side and detects a synthesized sound of the noise and the additional sound, and is vertically (n−1) a and horizontally (n -1) An error microphone provided in an error microphone installation range in which the centroid of the rectangle b is substantially coincident with the centroid of the cell unit, and each error microphone is detected for each cell unit. A control device that calculates an evaluation function that minimizes the sound pressure of the synthesized sound to be output based on the sound pressure of noise detected by each reference microphone and generates an additional sound signal for an additional sound source speaker And comprising.

（ここで、ｋ(=2πf／c ，f ：周波数，c ：音速)は波数、ｎは１≦ｎ≦２の実数）を満足させ、前記開口部の近傍にレファレンスマイクロフォンを配置し、前記他方側に、前記騒音に付加音を放射する付加音源スピーカを設け、さらに、前記他方側に、前記騒音と前記付加音との合成音を検出するエラーマイクロフォンを設け、かつ、このエラーマイクロフォンは、前記壁面とほぼ平行な面内において、縦（ｎ−１）ａ、横（ｎ−１）ｂの矩形で、図心を、前記開口部の図心とほぼ一致させた、エラーマイクロフォン設置範囲に設け、前記エラーマイクロフォンで検出する前記合成音の音圧が最小となる評価関数を、制御装置によって、前記リファレンスマイクロフォンで検出した騒音の音圧を基にして、演算すると共に、付加音源スピーカ用の付加音信号を生成し、この付加音信号によって前記付加音源スピーカから付加音を放射させる、ものとして構成される。 Furthermore, the present invention is a noise reduction method for reducing the level of noise when one side of a wall surface having an opening enters the other side from the opening, wherein the opening has a length a and a width b. Set it to a rectangular shape,

(Where k (= 2πf / c, f: frequency, c: speed of sound) is a wave number, n is a real number of 1 ≦ n ≦ 2, and a reference microphone is disposed in the vicinity of the opening, An additional sound source speaker that radiates an additional sound to the noise is provided on the side, and an error microphone that detects a synthesized sound of the noise and the additional sound is provided on the other side. In a plane substantially parallel to the wall surface, a rectangular (vertical (n-1) a, horizontal (n-1) b) is provided in the error microphone installation range in which the centroid substantially coincides with the centroid of the opening. The control device calculates an evaluation function that minimizes the sound pressure of the synthesized sound detected by the error microphone based on the sound pressure of the noise detected by the reference microphone, and is used for an additional sound source speaker. An additional sound signal is generated, and the additional sound is radiated from the additional sound source speaker by the additional sound signal.

  According to the present invention, it is possible to reduce noise that tends to enter from the opening.

  Embodiments of the invention will be described below.

  FIGS. 1A and 1B are a perspective view and a longitudinal sectional side view of the entire apparatus for explaining an embodiment of the present invention. Here, the case where the incident noise 3 from the outside tries to enter the inside of the housing 1 from the opening (or the duct in the ventilation system) 2 in the wall surface is assumed. In this case, the incident noise 3 is made high by the additional sound source speaker 5 provided inside the housing 1 by making the size of the opening 2 large enough to be considered as an active silencing upper plane wave. It tries to offset the efficiency.

  Here, before describing the embodiments of the present invention in detail, the basic concept of the present invention will be described. In defining the shape of the opening (duct), that is, the aspect ratio, the present invention is an invention in which the basic concept is completely different from the conventional concept made based on the mode shape. That is, the present invention is based on the theory of control effect. This theory is explained below.

（ここで、ａ_０は定数）
と表せる。このときの騒音源からの音（ｐ_１）と付加音源スピーカからの音（ｐ_２）間の位相差（ξ（ｒａｄ））は
ξ＝π （式２）
と導かれる。 Assuming that the two sounds of the sound from the noise source (p ₁ ) and the sound from the additional sound source speaker (p ₂ ) have the same amplitude, the synthesized sound of these two sounds is to minimize the sound pressure. ,

(Where a ₀ is a constant)
It can be expressed. At this time, the phase difference (ξ (rad)) between the sound (p ₁ ) from the noise source and the sound (p ₂ ) from the additional sound source speaker is ξ = π (Expression 2)
It is guided.

であることから、

と求まる。 On the other hand, when the range of the phase difference (ξ (rad)) between the sound (p ₁ ) from the noise source capable of reducing the sound pressure and the sound (p ₂ ) from the additional sound source speaker is obtained,

Because

It is obtained.

となり、開口部の開口面で、２つの入射波相互間がこの位相差範囲にあれば能動消音効果を得ることが可能である。 From (Expression 2) and (Expression 4), the error range (δ (rad)) from π as an ideal phase difference for sound pressure reduction is

Thus, if the two incident waves are within this phase difference range on the opening surface of the opening, an active silencing effect can be obtained.

  The present invention is based on the above theory.

  Now, a case 1 shown in FIG. 1 is assumed. The housing 1 has an opening 2 having a and b on the front side surface (wall surface) as the near side in FIG. A duct 20 is formed on the back side (downstream side of noise) of the opening 2. As can be seen from FIG. 1B, a reference microphone 4 for detecting incident noise 3 is installed in the vicinity of the opening 2 on the front side surface of the housing 1.

  The additional sound source speaker 5 is installed in the duct 20 connected to the opening 2. Further, an error microphone 6 is installed on the downstream side of the duct.

  FIG. 2 is a diagram showing the relationship between the dimension of the opening 2 and the installation position of the error microphone 6.

The openings 2 in the vertical and horizontal directions a and b are actively defined in a size range that can be controlled as an active silencing upper plane wave. That is, the length of the diagonal line in the opening 2 is such that the circularity π satisfies the wave number k (= 2πf / c, f: frequency, c: sound velocity) and an arbitrary real number n (n is 1 ≦ n ≦ 2). It is smaller than the value divided by the product of (real number). That is

  This equation is satisfied in order to produce a plane wave in the opening 2. An error microphone installation range 7 is determined in the opening 2. The size of the error microphone installation range 7 is set as vertical (n-1) a and horizontal (n-1) b.

  FIG. 3 is a block diagram showing the entire apparatus of the present invention. This device includes a control device 9 and an internal coefficient storage device 10 as elements other than the elements described above. In the figure, 8 is a centroid.

  In this apparatus, incident noise 3 is detected by a reference microphone 4 and transmitted to a control device 9. Based on the signal from the reference microphone 4, the control device 9 generates a signal from the additional sound source speaker 5 so as to satisfy the evaluation function that minimizes the sound detected by the error microphone 6, and this signal generates the additional sound source speaker. An additional sound is emitted from 5. The synthesized sound of the incident noise 3 and the additional sound is detected by the error microphone 6. In the above process, the result of the calculation by the control device 9 is stored in the internal coefficient storage device 10. By using the stored result as a fixed coefficient, the error microphone 6 can be finally omitted.

  FIG. 5 shows a case where the opening 2A is longer than the opening 2 shown in FIG. 1, that is, the horizontal length is three times that of the opening 2, for example (3 × b). ing. In this case, it can be considered in the same manner as in the case of FIG. 1 by providing the partition plates 21 and 21 that are divided for each horizontal length b. Further, the partition plate 21 can be omitted. In such a case, the reference microphone 4, the additional sound source speaker 5, and the error microphone 6 may be installed for each section (a × b) as in FIG. That is, if the opening is laterally longer than the opening 2 in FIG. 2, the lateral length may be considered as a plurality of cell units for each b. That is, for example, when the opening 2A is vertical a and horizontal 3b as shown in FIG. 5, the range of vertical a and horizontal b is considered as one cell unit. For each cell unit, a reference microphone 4, an additional sound source speaker 5, and an error microphone 6 may be provided in the same manner as in FIGS. Thereby, noise can be reduced in the same way as in the case of the opening 2 having the vertical a and the horizontal b as described above.

  FIG. 4 is a graph showing the effect of the embodiment of the present invention. The vertical axis represents the sound pressure level SPL (sound pressure level). When the center frequency is 250 Hz, 500 Hz, and all frequencies OA (overall), the left side indicates the sound noise level when the present invention is not applied, and the right side indicates the sound noise level when the present invention is applied. As can be seen from FIG. 4, according to the embodiment of the present invention, it can be seen that noise is reduced at each frequency.

The perspective view which shows the installation positional relationship of each element for demonstrating the Example of this invention, and longitudinal cross-sectional explanatory drawing. Explanatory drawing of an opening part. The block diagram of the apparatus of the Example of this invention. The graph which shows the effect of the Example of this invention. The figure which shows the opening part of the Example from which this invention differs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Opening part 3 Incident noise 4 Reference microphone 5 Additional sound source speaker 6 Error microphone 7 Error microphone installation range 8 Center of centroid 9 Control device 10 Internal coefficient storage device

Claims (5)

A noise reduction device that reduces the level of noise on one side of a wall surface having an opening when entering the other side from the opening,
Vertical a, horizontal b,

(Where k (= 2πf / c, f: frequency, c: speed of sound) is a wave number, n is a real number satisfying 1 ≦ n ≦ 2), and a reference microphone arranged in the vicinity of the rectangular opening,
An additional sound source speaker that is disposed on the other side and radiates an additional sound to be added to the noise;
An error microphone that is disposed on the other side and detects a synthesized sound of the noise and the additional sound, and is vertically (n−1) a and horizontally (n−1) within a plane substantially parallel to the wall surface. an error microphone provided in an error microphone installation range, wherein the centroid of the rectangle b is substantially coincident with the centroid of the opening;
An evaluation function that minimizes the sound pressure of the synthesized sound detected by the error microphone is calculated based on the sound pressure of the noise detected by the reference microphone, and an additional sound signal for the additional sound source speaker is generated. A control device;
A noise reduction device comprising:   The noise reduction device according to claim 1, wherein at least one of the reference microphone, the error microphone, and the additional sound source speaker is provided.   A storage device that stores the internal coefficient of the control device as a fixed coefficient, and after the evaluation function is once calculated by the control device, the addition based on the internal coefficient without using the detection signal of the error microphone; The noise reduction apparatus of Claim 1 which controls a sound source speaker. A noise reduction device that reduces the level of noise on one side of a wall surface having an opening when entering the other side from the opening,
Vertical a, horizontal b,

(Where k (= 2πf / c, f: frequency, c: speed of sound) is a wave number, and n is a real number of 1 ≦ n ≦ 2). A reference microphone arranged for each cell unit in the opening,
An additional sound source speaker that is arranged on the other side and emits an additional sound to be added to the noise in each cell unit;
In each cell unit, an error microphone that is arranged on the other side and detects a synthesized sound of the noise and the additional sound, and is vertically (n−1) a in a plane substantially parallel to the wall surface, An error microphone provided in an error microphone installation range in a horizontal (n-1) b rectangle and having a centroid substantially coincident with the centroid of the cell unit;
For each cell unit, an evaluation function that minimizes the sound pressure of the synthesized sound detected by each error microphone is calculated based on the sound pressure of the noise detected by each reference microphone, and an additional sound source speaker A control device for generating an additional sound signal for
A noise reduction device comprising: A noise reduction method for reducing the level of noise on one side of a wall surface having an opening when entering the other side from the opening,
The opening is set to a rectangular shape of length a and width b,

Where k (= 2πf / c, f: frequency, c: sound speed) is wave number, and n is a real number of 1 ≦ n ≦ 2.
Place a reference microphone in the vicinity of the opening,
On the other side, an additional sound source speaker that radiates an additional sound to the noise is provided,
Further, an error microphone for detecting a synthesized sound of the noise and the additional sound is provided on the other side, and the error microphone is arranged in a vertical (n−1) a, in a plane substantially parallel to the wall surface. A lateral (n-1) b rectangle with a centroid substantially aligned with the centroid of the opening, in the error microphone installation range;
An evaluation function that minimizes the sound pressure of the synthesized sound detected by the error microphone is calculated by the control device based on the sound pressure of the noise detected by the reference microphone, and the additional sound for the additional sound source speaker is calculated. A signal is generated, and an additional sound is emitted from the additional sound source speaker by the additional sound signal;
The noise reduction method characterized by the above-mentioned.

Images