JPH0727389B2 - Electronic silencing system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic silencing system, and in particular, an unsteady state generated in a propagation path such as a pipeline by performing adaptive control by a controller incorporating a digital filter. The present invention relates to an improvement of an electronic silencing system capable of silencing noise.

[Background of the Invention]

As a method of silencing the noise in the pipe, an active silencer, that is, an electronic silencing system that radiates additional sound of the same sound pressure and opposite phase to the noise propagating from the sound source and forcibly produces the silencing effect by sound wave interference It is getting attention. With the rapid development of electronic devices and signal processing technology, research results from various viewpoints have been announced one after another. The applicant of the present invention also applied the technical means for putting the electronic silencing system to practical use in Japanese Patent Application Nos. 60-139293 (61-296392) and 61-7115 (62-164400). Etc.

However, in such a muffling system, in order to maintain the muffling effect, it is necessary to have a control means for changing the output to the additional sound source in response to the change of noise over time. When the control is continued by using the change over time detected during and control as a new control parameter, the control must be temporarily interrupted in order to correct the data and transfer the data. However, there is a problem in that the muffler system is lacking, and it is required to solve the problem as the muffling system is put into practical use.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electronic muffling system capable of correcting control parameters without interrupting the operation of the system even during the operation of the system.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention generates a sound wave having the same sound pressure and a phase opposite to that of a sound wave propagating from a noise source in the sound wave propagation path, and the sound wave is generated at a predetermined position in the propagation path. A first mechanical-electrical conversion unit that is disposed closer to the noise source than the predetermined position in the propagation path and that detects a sound wave propagated from the noise source and converts the acoustic wave into an electric signal in order to muffle the sound wave interference. An electromechanical conversion means for emitting a sound wave for canceling a sound wave propagating from a noise source at the predetermined position, which is provided between the position where the first electromechanical conversion means is disposed in the propagation path and the predetermined position. A second machine which is provided between or at the predetermined position of the electromechanical conversion means and at the predetermined position, and which detects a sound wave propagated from the electromechanical conversion means and the noise source and converts the sound wave into an electric signal. Electrical conversion means, and the first A drive signal given to the electromechanical conversion means so as to take in the output signal of the electromechanical conversion means and the output signal of the second electromechanical conversion means and maximize the silencing volume of the electronic silencing system based on the given transfer function. Which determines the transfer function to be applied to the digital filter, sets the control parameters for specifying the transfer function in the digital filter, changes the propagation characteristics of the propagation path, and characteristics of the control system. In the electronic silencing system including a control unit that modifies the control parameter according to a change, the digital filter includes a storage device for storing two coefficients and a storage device for two input signals. When the control parameter stored in one storage device for storage is used to create the drive signal, the other storage device The corrected control parameter from the control unit is stored and both of them are switched and used, and the one storage device for the input signal always takes in the input signal from the first electromechanical conversion means. It is used to create a drive signal, and the other storage device is characterized in that writing of an input signal is interrupted if necessary, and the input signal just written is transferred to the control unit. is there.

The most important feature of the present invention is that the digital filter has two RAMs for storing coefficients and two RAMs for input signals. In the conventional digital filter, since each of these RAMs has only one, the operation must be interrupted when updating the coefficient and transferring the input signal.
Although it has been a cause of discontinuity and non-responsiveness, the present invention has made it possible to solve this problem.

Example of Invention

Preferred embodiments of an electronic silencing system according to the present invention will be described below with reference to the accompanying drawings. Prior to the description of a specific embodiment, the principle of a single-pole sound source type electronic silencing system having a single additional sound source will be described with reference to FIG. In the figure, a sensor microphone M ₁ is provided in the propagation path 1 of the sound wave, and a microphone for evaluating the muffling effect is provided downstream of the installation position of the sensor microphone M _1.
Each M ₂ is installed.

Further, an additional sound source S is provided between the microphones M ₁ and M ₂ . A controller 2 is provided between the sensor microphone M ₁ and the additional sound source S.

In the above structure, the sound wave propagated from the noise source is first detected by the microphone M ₁ , converted into an electric signal and input to the controller 2.

The controller 2 also receives an evaluation signal 3 for evaluating the sound deadening effect from the microphone M ₂ . Controller 2 adds a driving signal such as the output of the micro Huong M ₂ is zero by interference between sound waves propagating from the sound-absorbing acoustic and noise source emitted from the additional sound source S at the installation position of the micro Huong M ₂ Output to the sound source S. With this configuration, it is possible to eliminate the sound wave emitted from the noise source at the installation position of the microphon M ₂ .

Such in order to enhance the silencing effect in the configuration electronic silencing system transfer function Gd showing the propagation characteristics of sound in the electro-acoustic transducer shown in FIG. 2, Gd ', in addition to the micro-von M _1, M of Gt _{2. It} is also necessary to consider the conversion characteristics of each electroacoustic transducer such as the additional sound source S.

Further, FIG. 3 shows a principle diagram of a dual-sensing microphonic electronic silencing system.

In this figure, the difference from the single-pole sound source type electronic silencing system shown in FIG. 2 is that two sensor microphones M ₁ and M ₁ for detecting a sound wave propagating from a noise source in the sound wave propagation path 1 are provided. 'to the output of the additional sound source S to based on the fact that are respectively disposed on the upstream and downstream position sensor micro Huong M _1, M ₁ other sensors micro Huong' the output of the inverse phase Then, these output signals are input to the adder circuit 20, and the output signal of the adder circuit 20 is input to the controller 2.

Here, He is a transfer function indicating the control characteristic of the controller 2. The output of the sensor microphone M ₁ and the additional sound source S
, And the output of the sensor microphone M ₁ ′ are provided with electrically measurable evaluation points V _A , V _B , and V _C.
FIG. 4 shows a model in which the propagation characteristics of sound waves in the propagation path 1 and the conversion characteristics of the electroacoustic transducers themselves are considered with reference to these evaluation points V _A , V _B , and V _C. In the figure, thick arrows indicate the propagation direction of sound waves, and solid arrows indicate the flow of electrical signals.

P ₁ and P ₂ are microphons M ₁ and M ₁ ′ of propagating sound waves from a noise source propagating in the propagation path 1 in the downstream direction, respectively.
Is a voltage at the sound pressure at the installation _{position, V A, V B, V} C is the micro Huong M ₁ as described above, the speaker S as an additional source, the measuring point provided in s husband micro Huong M ₁ ' .

Further, Gd is a transfer function indicating the propagation characteristic of the sound wave from the microphon M ₁ to the microphon M ₁ ′, and H _M1 and H _M1 ′ are for the sound wave detected by the microphons M ₁ and M ₁ ′ in the propagation path 1. It is a transfer function showing a sound pressure-voltage conversion characteristic.

Further, Hr is a sensor microphone from the additional sound speaker S.
Ht is a transfer function expressed by including the conversion characteristics of each electroacoustic transducer itself of the system leading to M ₁ and the propagation characteristics of the sound wave in the propagation path 1. Ht is the system leading from the additional sound source S to the sensor microphone M ₁ ′. Is a transfer function expressed by including the conversion characteristics of each electroacoustic transducer itself and the propagation characteristics of the sound wave in the propagation path 1.

In this dual sensing microphone system, the characteristic is located at a position where the transfer functions Ht and Hr from the additional sound source S become equal (simply, a position equidistant from the additional sound source S in the propagation path 1 corresponds to this). 'set up, to the output of the sensor micro Huong M _1, sensor micro von M _1' SoroiTsuta sensor micro Huong M _1, M ₁ and inputted to the adding circuit 20 while the output of the reverse phase, the adder circuit 20 outputs are input to the controller 2.

With this configuration, the sensor microphone M ₁
The sound wave propagated from the additional sound source S detected by
It is electrically erased by 20, and the oscillation state is suppressed.

As described above, the dual sensing microphonic method is an excellent feature that can suppress the acoustic feedback by only adding one sensor microphone and a basic addition circuit as an electric circuit to the electronic muffling system of the monopole sound source method. You can see that it has.

Next, FIG. 5 shows a specific configuration of the electronic silencing system according to the present invention constructed based on the above model.

In the figure, sensor microphones M ₁ and M are provided in the propagation path 1.
The transfer function Hr _{of 1} 'indicates the propagation characteristics of sound waves radiated from said additional sound source S by sandwiching the additional sound source S, Ht is equivalent position, is disposed equal distance position referenced to the example additional sound source S ing.

Further, 28 is an input / output interface, which is an A / D converter 24,
25 and a D / A converter 26. 29 is a speaker S that emits a sound wave for canceling a sound wave propagating from the noise source.
Is a digital filter that creates a drive signal to be output via the D / A converter 26.

Further, the control unit 30 causes the output signals of the adder circuit 20 to which the outputs of the sensor microphones M ₁ and M ₁ ′ are input and the output signal of M ₁ ′, which also functions as the muffling effect evaluation microphone, from the A / D conversion units 24 and 25. A test signal is output to each circuit section in the state where noise does not exist in the propagation path 1 based on these signals, and the propagation characteristics of the propagating sound wave between each electroacoustic transducer or each A transfer function indicating the conversion characteristic of the electroacoustic transducer itself is derived, or a control parameter for giving a predetermined transfer function to the digital filter 29 when noise exists in the propagation path 1 is set.

Further, the control unit 30 performs adaptive control so as to correct the control parameters according to the disturbance in the propagation passage 1, for example, the change in the propagation characteristic of the sound wave due to the fluctuation of the air flow and the change in the characteristic of the control system.

In the above configuration, first, the digital filter 29 has the transfer function He shown in FIG.
The control unit 30 sets the control parameter for giving the transfer function corresponding to. In this state, the sound wave propagated from the noise source in the propagation path 1 is
When detected by M ₁ and M ₁ ′, the sensor microphone
The output signal from the adder circuit 20 to which the output signals of M ₁ and M ₁ ′ are input is the A / D converter 24 in the input / output interface 28.
Is input to the digital filter 29 and the control unit 30 via.

The control unit 30 obtains transfer functions showing these characteristics in consideration of changes in the propagation characteristics due to disturbances in the propagation path 1 and changes in the characteristics of each electroacoustic transducer itself, and the muffling is performed based on these transfer functions. The transfer function to be given to the digital filter 29 is determined so that the effect, that is, the output signal of the microphone M ₁ ′ for detecting the interference state between the sound wave propagated from the noise source and the sound wave emitted from the speaker S is minimized, A digital filter is used as a control parameter for specifying the transfer function.
Set to 29. As described above, the control unit 30 modifies the control parameter, that is, the coefficient of the digital filter 29, as needed, according to the change in the propagation characteristic of the propagation path 1 and the change in the characteristic of the control system.

As a result, the sound wave propagated from the noise source detected by the microphones M ₁ and M ₁ ′ is converted into an electric signal, and the adding circuit 20,
The input signal is input to the digital filter 29 via the A / D converter 24 in the input / output interface 28, and the input signal has predetermined amplitude characteristics and phase based on the transfer function given from the controller 30 by the digital filter 29. It is converted into a digital signal having characteristics. The digital signal is A / D converted by the A / D converter 26 in the input / output interface 28 and applied to the drive coil of the speaker S as a drive signal of the speaker S. Propagation of a noise source emitted from the speaker S. Sound waves are emitted to cancel the sound waves. Consequently microphone M ₁ 'propagating sound waves from at the installation position of the noise source by the interference of sound waves is erased, in microphones M ₁ during the propagation path' propagation wave from the noise source on the downstream side of the installation position of It will not be propagated. The acoustic sound-muffling emitted from the speaker S is 'detected by a speaker S and the microphones M _1, M _1' microphones M ₁ and M ₁ is an acoustic feedback system between is formed, above 'I have been arranged, and a microphone M ₁ with respect to the output signal of the microphone M _1' additional sound source S when viewed from the microphone M ₁ in the equivalent position transfer function, M ₁ as the output of the adder in opposite phase state The electric signal corresponding to the sound wave propagated from the speaker S to the sensor microphone M ₁ in order to be added in the circuit 20 is erased in the adding circuit 20, and therefore from the speaker S as an additional sound source to the sensor microphone M ₁ side. The acoustic feedback of is suppressed and the oscillation state does not occur.

By the way, it is preferable that the digital filter 29 update the coefficient of the filter even during operation. Therefore, in this digital filter, as shown in FIG. 1, when two RAMs for storing coefficients are prepared and RAM1 is used for convolution.
It is configured to transfer a new coefficient to RAM2, switch RAM1 and RAM2 when the coefficient transfer is completed, and transfer the new coefficient to RAM1 this time. As a result, the coefficient can be updated without interrupting the convolution. Furthermore, the input X of the digital filter and the error signal e are required to update the coefficients, of which X must also be used for the convolution, so that the acquisition cannot be interrupted. Therefore, as shown in FIG. 1, two digital signal RAMs are prepared for the digital filter, one is always writing new data, and the other is for input signal transfer, which is not required from the outside. As long as new data is written, writing is interrupted when a request is made and the written input signal is transferred to the outside. With this function, the input signal can be transferred to the outside without interrupting the convolution.

〔The invention's effect〕

As described above, in the present invention, since the digital filter in the electronic silencing system has the two memory devices for storing the coefficient and the two memory devices for the input signal for modifying the control parameter, It is possible to correct the control parameters even during the operation of the above without interrupting the operation.

[Brief description of drawings]

FIG. 1 is a block diagram of the digital filter 29 shown in FIG.
Fig. 2 is an explanatory diagram showing a model of an electronic muffling system of a unipolar sound source system, Fig. 3 is a principle diagram of an electronic muffling system of a dual sensing microphone system, and Fig. 4 is a propagation characteristic of a propagation path and each electric sound. FIG. 5 is an explanatory diagram showing a model of the electronic silencing system shown in FIG. 2 in consideration of the conversion characteristics of the converter itself, and FIG. 5 is a block diagram showing a concrete configuration of the electronic silencing system shown in FIG. 1 ... Propagation path, 20 ... Addition circuit, 24, 25 ... A / D converter, 2
6 …… D / A converter, 28 …… I / O interface, 29 ……
Digital filter, 30 ... Control unit.

Claims (1)

[Claims] Claim: What is claimed is: 1. A sound wave having a phase opposite to that of a sound wave propagating from a noise source in the sound wave propagation path and having the same sound pressure is generated, and the sound wave is muted at a predetermined position in the propagation path by the sound wave interference. In the electronic silencing system, a first mechanical-electrical conversion unit that is disposed closer to the noise source than the predetermined position in the propagation path, detects a sound wave propagating from the noise source, and converts the sound wave into an electric signal. An electromechanical conversion means for emitting a sound wave for canceling a sound wave propagating from a noise source at the predetermined position, the electromechanical conversion means being provided between the arrangement position of the first electromechanical conversion means and the predetermined position. Second mechanical-electrical conversion means provided between the position where the means is provided and the predetermined position or at the predetermined position, for detecting a sound wave propagated from the electro-mechanical conversion means and the noise source and converting it into an electric signal; The first A drive signal given to the electromechanical conversion means so that the output signal of the electromechanical conversion means and the output signal of the second electromechanical conversion means are taken in and the volume of the electronic silencing system is maximized based on the given transfer function. To determine the transfer function to be applied to the digital filter, set the control parameters for specifying the transfer function in the digital filter, and change the propagation characteristics of the propagation path and the characteristics of the control system. And a controller including a digital filter and a controller, wherein the digital filter includes a storage device for storing two coefficients and a storage device for two input signals. And using the control parameter stored in the one storage device for storing the coefficient to create the drive signal. In this case, the other storage device stores the modified control parameter from the control unit, and both are used by switching, and one storage device for the input signal is used from the first electromechanical conversion means. The input signal of 1 is always used to generate the drive signal, and the other storage device interrupts the writing of the input signal as necessary and transfers the input signal written immediately before to the control unit. Electronic muffling system characterized by doing so.