JP2009083809A - Active noise reduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active noise reduction device capable of providing a noise reduction effect by controlling transfer of mechanical vibration from a secondary noise generation means transferred to a detection means concerning the active noise reduction means to reduce noise in a cabin. <P>SOLUTION: This active noise reduction device outputs an output of a second simulated transfer characteristic correction means 110 in accordance with mechanical transfer characteristics to an adaptive type filter 107 in addition to a coefficient renewal means 109 together with an output of a noise detection means 103 detecting radial noise and mechanical vibration from a speaker which is a secondary noise generation means 102 and makes it possible to provide the stable active noise reduction device by avoiding malfunction by a signal part in accordance with the mechanical vibration detected by the noise detection means 103. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention allows this signal to interfere with an unpleasant noise such as an engine noise generated in the passenger compartment of the moving means due to engine rotation or driving in various external situations by interfering with an opposite phase and equal amplitude signal. The present invention relates to an active noise reduction device that reduces unpleasant noise.

  Engine noise is synchronized with the engine speed because the vibration generated by the engine rotation is transmitted to the vehicle body and is generated by resonance in the vehicle compartment, which is a closed space, under certain conditions. It has a remarkable periodicity.

  As a conventional active noise reduction device for reducing such an unpleasant engine noise, a method of performing feedforward adaptive control using an adaptive notch filter is known. Such a conventional active noise reduction apparatus will be described in conjunction with the operation by referring to the block diagram of the active noise reduction apparatus shown in FIG.

  According to the figure, the discrete calculation for realizing the active noise reduction device is processed by a control unit 105 such as a DSP (Digital Signal Processor). First, as described above, a signal having a high correlation with noise (engine noise) is used as a reference signal to remove noise and the like superimposed on the engine pulse by the reference signal generation means 106 and generate a waveform after shaping. The output (reference) signal of the reference signal generating means 106 is added to the adaptive filter 107, multiplied by the adaptive filter coefficient, input to the signal amplifying means 104, and then input to the secondary noise generating means 102. Secondary noise is generated by the secondary noise generation means 102 and is reduced by interfering with noise that is a problem. At this time, the residual signal that has not been silenced by the noise detection means 103 of the noise suppression unit 101 is used as an error signal e in the adaptive control algorithm.

  Note that the reference signal generating means 106 detects the rotation signal and ignition signal of the engine that is the noise generation source, if the noise to be reduced has periodicity such as the engine, and the noise that becomes a problem is detected. There are various possibilities such as generating a sine wave and cosine wave substantially the same as the frequency of the sensor, and correcting the output by detecting a change in an acceleration sensor attached to the body of an automobile.

  On the other hand, the first correction signal is a characteristic that simulates the spatial acoustic transmission characteristic from the secondary noise generation means 102 to the noise detection means 103 of the noise suppression unit 101 at the frequency to be silenced obtained from the engine speed. An output signal from the reference signal generating means 106 is input to the first simulated transfer characteristic correcting means 108 to be generated, and an output (first correction signal) from the first simulated transfer characteristic correcting means 108 and an error signal e Is updated to the coefficient updating means 109, and the filter coefficient of the adaptive filter 107 is updated based on an adaptive control algorithm, for example, an LMS (Least Mean Square) algorithm which is a kind of steepest descent method.

  In this way, the filter coefficient of the adaptive filter 107 recursively converges to an optimum value so that the error signal e becomes smaller, in other words, the noise in the noise suppression unit 101 is reduced.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2000-99037 A

  However, in the conventional active noise reduction apparatus described above, as shown in the explanatory diagram for explaining the relationship between the input / output signals to and from the secondary noise generating means 102 and the noise detecting means 103 in FIG. Due to restrictions on the installation location of the generation means 102 and the noise detection means 103, in some cases, the vibration from the speaker that is the secondary noise generation means 102 is not an acoustic vibration that has transmitted the space, but a machine that has transmitted the installation portion. May be transmitted to the microphone of the noise detection means 103 as a typical vibration. At that time, not only the noise that becomes a problem at the occupant's ear position and the secondary noise for canceling it, but also an electrical signal including mechanical vibration is input to the coefficient updating means, The noise reduction effect is reduced, and in the worst case, the noise may increase.

  The present invention solves the above-mentioned problem. In the transfer characteristics from the secondary noise generating means to the noise detecting means, the influence of the mechanical transfer characteristics on the acoustic transfer characteristics is eliminated, and stable noise reduction control is performed. It is an object of the present invention to provide an active noise reduction device that can be used.

  In order to solve the above-mentioned problems, the present invention provides mechanical vibration transmission characteristics from the secondary noise generation means by providing second simulated transmission characteristic correction means based on the mechanical vibration transmission characteristics from the secondary noise generation means. This is to prevent the noise reduction effect due to the influence of the deterioration.

  As described above, the active noise reduction device according to the present invention stabilizes vehicle interior noise by suppressing the influence of noise outside the noise detection means due to mechanical vibration transmission from the secondary noise generation means to the noise detection means. Therefore, it is possible to provide an active noise reduction device that can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the description, the same parts as those in the prior art will be denoted by the same reference numerals and the description thereof will be omitted.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The case where the present invention is mounted on, for example, a vehicle or the like to reduce noise generated in the passenger compartment will be described.

  FIG. 1 is a block diagram of an embodiment of an active noise reduction apparatus according to the present invention, and FIG. 2 is an explanatory diagram for explaining the transmission characteristics of spatial acoustic transmission and mechanical vibration transmission in a noise suppression unit which is the main part of the same. FIG. 3 is an explanatory diagram for explaining the relationship between the input signals to the electroacoustic conversion means and the noise detection means, which are the main parts, and the output, and FIG. 4 is the same. It is explanatory drawing explaining the relationship between the input-output signal to a means, and the noise used as a subject.

  According to the figure, the difference from the prior art is that a second correction signal is generated that is corrected with a characteristic simulating the mechanical vibration transfer characteristic between the secondary noise generating means 102 and the noise detecting means 103. The second simulated transfer characteristic correcting means 110 is provided, and the output (second correction signal) of the second simulated transfer characteristic correcting means 110 is input to the coefficient updating means 109 for changing the filter coefficient of the adaptive filter. The filter coefficient of the adaptive filter 107 is changed between the output from the first simulated transfer characteristic correcting means 108 (first correction signal) and the output from the second simulated transfer characteristic correcting means 110 (second correction signal). It is the point which was set as the structure input into the coefficient update means 109 to do.

  The operation and effect of the active noise reduction apparatus having the above configuration including the second simulated transfer characteristic correcting means 110 as described above will be described below.

The noise is Vno, the output from the secondary noise generating means 102 for reducing the noise is Vo, and the spatial acoustic transfer characteristic between the secondary noise generating means 102 and the noise detecting means 103 is Cs and the secondary noise is generated. If the mechanical vibration transmission characteristic between the means 102 and the noise detection means 103 is Cv, the detection signal Verr of the noise detection means 103 is 0 when the noise is ideally reduced. Verr = Vno + CsVo + CvVo = 0 − (1)
It becomes. Here, when mechanical vibration transmission is negligible, that is, when Cv << Cs,
Cs (1 + Cv / Cs) Vo≈CsVo− (2)
Therefore, the noise Vt in the vicinity of the noise detecting means 103 is Vt = Vno + CsVo≈Verr = 0− (3)
It can be seen that noise is reduced. However, if the approximation of equation (2) does not hold (if mechanical vibration transmission cannot be ignored), Vt = Vno + CsVo = −CvVo ≠ 0− (4)
Thus, there is a situation where noise is not necessarily reduced in the vicinity of the noise detection means 103, that is, in the position of the occupant's ear. By the way, assuming that the noise is reduced at the occupant's ear position,
Vt = Vno + CsV ′ = 0− (5)
From this, the detection signal of the noise detection means 103 is
Verr = Vno + CsV ′ + CvV ′ = CvV ′ ≠ 0− (6)
It becomes. Since Verr is not 0, the coefficient updating unit 109 tries to further update the coefficient. However, when the coefficient updating unit 109 recognizes that the state of Verr = CvV ′ is optimal, the coefficient updating is stopped, and Vt = 0. It is possible to maintain the optimum state. That means
Verr ′ = Verr−CvV ′ − (7)
It can be seen that the noise at the occupant's ear position is reduced when the control is performed so as to be optimal.

  In order to perform this control, the second simulated transmission characteristic correction unit 110 uses the detection signal Verr of the noise detection unit 103, the output V ′ of the adaptive filter 107, and the simulated transmission correction value -Cv based on the mechanical vibration transmission characteristic. As a new noise detection signal, a signal obtained by multiplying the signal obtained by multiplying by is able to realize optimal control.

More specifically, the noise detection means 103 such as a microphone provided in the vicinity of the position where noise reduction is desired, and the noise having the same amplitude and opposite phase as the noise at the position where noise reduction is desired. In secondary noise generating means 102 such as a speaker that generates secondary noise and fixing means 101a such as a vehicle body for mounting and fixing these, signal transmission characteristics C (2) from secondary noise generating means 102 to noise detecting means 103 ω) is
C (ω) = S (ω) + V (ω) − (8)
It is expressed.

  However, S (ω) is an acoustic transmission characteristic transmitted through space, and V (ω) is a mechanical vibration transmission characteristic transmitted through the fixing means 101a.

Here, the relationship between the input signal Vo (ω) to the secondary noise generation means 102 and the input signal Verr (ω) to the noise detection means 103 is a complex plane as shown in FIG. Can be expressed as However, the input signal to the secondary noise generating means 102 is used as a reference. That is, the expression Verr (ω) = C (ω) Vo (ω) + S (ω) Vo (ω) − (9)
It becomes.

  Therefore, the output from the adaptive filter 107 is input to the second simulated transfer characteristic correcting unit 110 that simulates the mechanical vibration transfer characteristic, and the sum of the output of the simulated transfer characteristic correcting unit 110 and the signal of the detecting unit 103 is calculated. By performing control such as the LMS method, it is possible to output a signal having the same amplitude and opposite phase as noise that is acoustically problematic.

That is, the correction value −Vv ′ may be obtained from the input signal Vo ′ and added to the detection signal. here,
−Vv ′ = − V (ω) Vo ′ (ω)
Therefore, it can be seen that the correction value for the certain frequency of the simulated transfer characteristic correction means may be −V (ω).

  As described above, by correcting the transfer characteristic with the value of the reverse phase of the mechanical vibration transfer characteristic, it is possible to eliminate the influence of the transfer characteristic of the mechanical vibration on a certain frequency and realize the optimum noise reduction effect. it can.

  In the above-described embodiment, the frequency to be controlled is described as singular. However, even when the frequency to be controlled is plural, the influence of mechanical vibration can be eliminated by the same method.

  As described above, according to the present invention, the influence of the transmission of mechanical vibration from the secondary noise generating means to the noise detecting means is detected from the adaptive filter by the second simulated transfer characteristic correcting means as described above. By correcting the output, it is possible to calculate the acoustic transmission signal at the occupant's ear position and obtain an ideal noise reduction effect, so not only the vehicle interior noise is reduced, but also mechanical vibration and noise are mixed. It can be used to suppress the influence of mechanical vibration in a noise reduction device in a closed place.

The block diagram which shows the structure of one Embodiment of the active noise reduction apparatus of this invention Explanatory drawing explaining the transmission characteristics of spatial acoustic transmission and mechanical vibration transmission in the noise suppression part which is the main part Explanatory drawing explaining the relationship between the input signal and output to the electroacoustic conversion means and the noise detection means which are the main parts Explanatory drawing explaining the relationship between the input / output signals to the electroacoustic conversion means and the noise detection means, which are the main parts, and the noise to be a problem Block diagram showing the configuration of a conventional active noise reduction device Explanatory drawing explaining the relationship between the input and output signals to the secondary noise generating means and the noise detecting means, which are the main parts, and the noise that is the subject

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Noise suppression part 101a Fixing means 102 Secondary noise generation means 103 Noise detection means 104 Signal amplification means 105 Noise reduction control unit 106 Reference signal generation means 107 Adaptive filter 108 First simulation transfer characteristic correction means 109 Coefficient update means 110 First 2 Simulated transfer characteristic correction means

Claims (1)

A reference signal generating means for generating a reference signal correlated with noise from a noise source, an adaptive filter to which the signal generated by the reference signal generating means is input, and an output signal from the adaptive filter are amplified, An amplifier that outputs an output signal that cancels out the noise, a secondary noise generating means that receives the output signal that cancels out the noise and generates secondary noise that cancels out the noise, and the noise and the 2 Noise detection means for detecting residual noise, which is a result of interference with secondary noise, and the reference signal corrected with characteristics simulating spatial acoustic transmission characteristics between the secondary noise generation means and the noise detection means. An active noise reduction apparatus comprising: a first simulated transfer characteristic correcting unit that generates one correction signal; and a coefficient updating unit that sequentially updates the adaptive filter coefficient based on the first correction signal. Thus, a second correction signal is generated by correcting the output signal from the adaptive filter with a characteristic simulating the mechanical vibration transfer characteristic between the secondary noise generating means and the noise detecting means. Simulated transfer characteristic correction means is provided, and the second correction signal generated by the second simulated transfer characteristic correction means is input to the coefficient update means, and the residual noise, the first correction signal, and the second correction signal are input. Active noise reduction device that updates the adaptive filter coefficient with the correction signal.