JPH0612083A - Noise reduction device - Google Patents

Abstract

(57) [Summary] [Purpose] Only the noise that should be silenced is silenced indoors. Also, without performing convolution calculation and transfer function estimation,
Increase responsiveness. A sound detection means (M1) for detecting a sound generated by a noise source (engine 12) or a signal corresponding to the sound, and a sound detected by a noise source or a signal corresponding to the sound, which corresponds to noise. Frequency range determining means for determining the frequency range (P
P, SCF1), a first frequency selecting means (SCF1) for extracting only the set frequency range from the sound or signal detected by the sound detecting means, and an antiphase sound of the signal passed through the first frequency selecting means. Anti-phase sound imparting means (BBD1, A1, SP, M2, SCF11, MP
U) equipped noise reduction device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reducing device for reducing noise by adding anti-phase noise to noise.
It can be applied to reduce noise in passenger cars, buses, ships, cabins of passenger cars, airplanes, etc.

[0002]

2. Description of the Related Art Generally, there is an adaptive control method as a method of reducing noise by adding an antiphase sound to noise.
FIG. 18 shows an adaptive control method. Microphone 25 for noise detection
Detects noise, the transversal filter 26 convolves the detection signal, and causes the speaker 27 to generate sound. On the other hand, the signal detected from the mute confirmation microphone 28 estimates and updates the filter coefficient of the transversal filter 26 which is considered to be optimal based on the adaptive algorithm 29. In order to muffle the muffled sound of the engine of the vehicle, a sensor for detecting the engine speed may be used instead of the noise detecting microphone 25. Since feedback is performed in this control method, it is possible to follow changes in the indoor condition, such as changes in the number of people in the room and changes in temperature.
However, the convolution calculation of the transversal filter and the filter coefficient estimation / updating of the adaptive algorithm require a large number of calculations, which cannot be realized without using a high-speed calculation chip such as a digital signal processor or a calculation-dedicated chip. Also, depending on the choice of convergence constant in the adaptive algorithm, the estimation can take a very long time,
During that time, the sound may not be silenced or the control system may become unstable.

Further, the noise reduction works to minimize the mean square error of the residual noise detected by the sound deadening confirmation microphone, so that all the sounds in the room are to be muted. Even the necessary sound is silenced in the room.

FIG. 19 differs from FIG. 18 in that the transfer function is estimated in advance and stored in the memory 24, and only the convolution operation is performed. The advantage of this device is that it does not have a feedback system, so the stability of the system is guaranteed, and it has the effect that the amount of calculation can be greatly reduced because it does not have an adaptive algorithm. However, even in this apparatus, the amount of convolution calculation is still large and a high-speed calculation chip or a calculation-dedicated chip is required. Further, since the transfer function measured in advance is stored in the memory, it is necessary to detect that the state has changed by another means.

An apparatus of the above system is disclosed in, for example, Japanese Patent Laid-Open No.
It is disclosed in JP-A-158296 and JP-A-3-50998.

[0006]

When reducing the noise in the room, it is desirable not to mute the sound needed by the person in the room. In particular, when a noise reduction device is installed in a vehicle, it is not a good idea to mute all the engine sounds, because it loses information on the operating state of the engine to the driver.

In view of the above, the first object of the present invention is to mute only the noise that should be muffled.

Further, convolution calculation and transfer function estimation take time, and a high-speed calculation chip or a calculation-dedicated chip is required.

In view of the above, the second object of the present invention is to improve the responsiveness of the noise reduction device without performing the convolution calculation and the transfer function estimation.

[0010]

To solve the above problems, the first means used in the present invention is sound detecting means for detecting a sound generated by a noise source or a signal corresponding to the sound.
Of the sound generated by the noise source or the signal corresponding to the sound, the frequency range determining means for determining the frequency range corresponding to the noise, and extracting only the set frequency range from the sounds or signals detected by the sound detecting means The first frequency selecting means and the anti-phase sound imparting means for generating the anti-phase sound of the signal passed through the first frequency selecting means.

The second means used in the present invention to solve the above-mentioned problems is a sound detecting means for detecting a sound generated by a noise source or a signal corresponding to the sound, and a sound generated by the noise source. Alternatively, a frequency range determination means for determining a frequency range corresponding to noise in a signal corresponding to the sound, and a first frequency selection for extracting only the set frequency range from the sound or the signal detected by the sound detection means. Means and said first
Phase adjusting means for adjusting the phase of the signal passed through the frequency selecting means, gain adjusting means for adjusting the amplification degree of the signal passing through the first frequency selecting means, and signal passing through the phase adjusting means and the gain adjusting means A speaker for producing a sound in the room based on the above, a sound deadening confirmation microphone for detecting a sound in the room, a second frequency selecting means for extracting only the set frequency range from the signal detected by the sound deadening confirmation microphone, The control means for setting the phase of the phase adjusting means and the gain of the gain adjusting means so as to minimize the power spectrum of the signal that has passed through the two frequency selecting means.

[0012]

According to the first means, the antiphase sound in the frequency band corresponding to the noise of the noise source detected by the sound detecting means or the signal corresponding to this sound, which corresponds to the noise that makes a person uncomfortable, has the opposite phase. It is generated by the sound adding means. This antiphase sound reaches the ear of the person in the room. At this time, the noise from the noise source also reaches the ear at the same time. A person in the room hears the noise from the noise source and the synthesized sound generated by the speaker. Therefore, the noise in the frequency band corresponding to the noise is canceled.

According to the second means, only the frequency band corresponding to the noise that the person feels uncomfortable in the sound of the noise source detected by the sound detecting means or the signal corresponding to this sound is the first frequency selecting means. It is extracted by. The phase adjusting means and the gain adjusting means adjust the phase and the gain of the extracted frequency range. The adjusted sound is emitted by the speaker and reaches the ear of the person in the room. At this time, the noise from the noise source also reaches the ear at the same time. Therefore,
A person in the room hears the noise from the noise source and the synthesized sound generated by the speaker. This synthesized sound is also detected by the mute confirmation microphone. The second frequency selection means extracts only the frequency band corresponding to noise from the sounds detected by the sound deadening confirmation microphone. Further, the control means calculates the power spectrum of the sound in this frequency band, and sets the phase of the phase adjusting means and the gain of the gain adjusting means so that this power spectrum is minimized. Therefore, the power spectrum of the frequency band corresponding to noise is
The phase adjustment means, the gain adjustment means, the speaker, the sound deadening confirmation microphone, the second frequency selection means, the control means, and the feedback path connected to the phase adjustment means and the gain adjustment means again adjust the value to the minimum value. , Noise in the frequency band corresponding to noise is canceled.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is mounted on a vehicle will be described below with reference to the drawings.

FIG. 1 is an overall schematic view of the present invention. The speaker SP and the mute confirmation microphone M2 extend from the headrest 11 of the seat 10 or the backrest 14 of the seat 10,
It is placed near the ear. An engine speed sensor PP is provided to detect the speed of the engine 12. At least one noise detection microphone M1 is installed as far as possible from the seat 10, for example, near the feet. The controller 13 is connected to the speaker SP, the sound deadening confirmation microphone M2, the engine speed sensor PP, and the noise detection microphone M1.

Since the speaker SP and the sound-deadening confirmation microphone M2 are arranged near the human ear, the speaker SP does not need to make a loud sound. Therefore, the sound emitted from the speaker SP does not affect the part away from the seat 10 or the outside of the vehicle, and the sound is not emphasized in other parts. Therefore, it reliably reduces only the noise coming into the ears of the person sitting in the seat and does not affect others.

Since the largest of the noise sources of the vehicle is the engine, it is desirable to mute the sound from the engine when it is mounted on the vehicle. FIG. 4 shows the noise distribution in the passenger compartment of a 4-cylinder engine. The engine speed at this time is 4016 rpm (66.9 Hz),
A large peak is formed in the part c of about 134 Hz of the second harmonic component. a is the primary component of the engine sound. The other part is due to other than engine rotation such as road noise. The c peak follows the change in the engine speed and the frequency fluctuates, but the sound of this secondary component is perceived by passengers as noise.

The audible sound that can be heard by the human ear is about 50.
Since the frequency is higher than Hz, the peak portion formed in the portion of 0 to 40 Hz may be ignored. Therefore, in a four-cylinder engine, only the secondary component shown in FIG.

FIG. 2 shows the details of the controller 13. The noise detection microphone M1 is a sound detection means and detects the sound inside the vehicle. The detected sound is the first frequency selecting means
After passing through the frequency selector SCF1, it is sent to the speaker SP through the phase adjuster BBD1 which is the phase adjusting means and the amplifier A1 which is the gain adjusting means. The engine speed sensor PP is a pulse pickup and is installed in the vicinity of the engine output shaft or a shaft indirectly connected to the engine output shaft, and detects the rotation speed of the engine 12.

The first frequency selector SCF1 receives the output e of the engine speed sensor PP. First frequency selector SC
The internal structure of F1 is shown in FIG. First frequency selector SCF
Reference numeral 1 includes a switched capacitor filter SCF, a phase difference detector 20, a charge pump 21, a loop filter 22, a voltage control oscillator VCO and a frequency divider 23. The phase difference detector 20 determines the phase difference between the pulse from the frequency divider and the pulse from the engine. Charge pump 21
Operates to make the phase difference between the pulse from the frequency divider 23 and the pulse from the engine zero, and outputs the voltage pulse of the phase adjusted amount. The loop filter 22 has the structure of an integrator, and outputs the voltage pulse from the charge pump 21 to the voltage control oscillator VCO in the form of an analog voltage. The voltage control oscillator VCO oscillates a frequency pulse according to the input voltage to generate a clock pulse CL
To the switched capacitor filter SCF and the frequency divider 23. The frequency divider 23 divides the input pulse into 1 / N and drops the frequency into 1 / N. This N is an integer and is set in advance.

Now, it is assumed that N times the frequency of the engine rotation pulse matches the clock frequency to the switched capacitor filter SCF. Here, when the engine speed increases, a phase difference occurs between the pulse from the frequency divider 23 and the engine rotation pulse.

At this time, the charge pump 21 acts to make this phase difference zero, and raises the output pulse voltage when the phase increases and lowers the output pulse voltage when the phase difference decreases. The loop filter 22 converts the output pulse into an analog voltage, and the voltage control oscillator VCO
Generates a clock pulse having a frequency corresponding to this analog voltage, so that the clock frequency increases when the phase difference increases, and the clock frequency decreases when the phase difference decreases. Therefore, the clock frequency fluctuates depending on the engine speed. Since the loop filter 22 has the configuration of the integrator, even if the phase difference is matched and the pulse from the charge pump is not output, the value up to that point is continuously output. Therefore, the frequency of the clock pulse CL output to the switched capacitor filter SCF is N times the engine speed.

FIG. 5 shows the principle of the switched capacitor filter. As shown in the figure, in the switched capacitor, the electric charge of CV1 is charged to the capacitor C at t = 0. Next, at t = Tc, the electric charge of CV2 is charged in the capacitor C. Therefore, the charge ΔQ that changes during the cycle Tc when the switch reciprocates is

[0024]

[Equation 1]

Is indicated by The average current i flowing at this time is

[0026]

[Equation 2]

[0027] Since the clock frequency fc is the reciprocal of the period Tc,

[0028]

[Equation 3]

It becomes From the equation (3), the magnitude of the average current is proportional to the capacitance C of the capacitor, its switching frequency fc, and the voltage (V1-V2). Therefore, the equivalent resistance value Req of the circuit of FIG.

[0030]

[Equation 4]

It becomes An integrator applying the property of this switched capacitor is shown in FIG.
eq becomes 1 / (C · fc). When this filter is designed, if Req is a resistor, a filter that follows changes in fc can be realized. The MF10 universal monolithic dual switched capacitor filter manufactured by National Semiconductor was created based on the above principle. By using this MF10, a bandpass filter that extracts only the frequency band corresponding to the frequency fc of the clock pulse CK is formed. can do.

Thus, the frequency N of the engine speed is
A clock pulse having a doubled frequency is given to the switched capacitor filter SCF, and the switched capacitor filter SCF adjusts the frequency band to be selected according to the frequency of the clock pulse. By adjusting this value N and the voltage range of the voltage control oscillator VCO, it is possible to obtain a bandpass filter capable of extracting only the frequency twice the engine speed. As a result, the noise detection microphone M
Of the vehicle interior sound detected by 1, only the second harmonic component of the engine speed can be extracted.

The extracted signal PA1 of the second harmonic component passes through the phase adjuster BBD1. The phase adjuster BBD1 is a BBD (Bucket Bridge Device).
e). This BBD has a plurality of stages of delay lines and sequentially transfers electric charge from the input side to the output side each time a clock is input.
There is N3005. When the clock frequency is variable, the signal can be delayed according to the clock frequency and the phase can be shifted. The clock frequency f1 given to the phase adjuster BBD1 is the microprocessing unit MPU.
Given by.

Signal PB1 passed through phase adjuster BBD1
Is fed to amplifier A1. The amplifier A1 receives the input signal PB
1 is amplified by a gain K1 to obtain an output signal PC1. The gain K1 is variable and is given from the microprocessing unit MPU. The output signal PC1 is the speaker S
Given to P. Therefore, of the vehicle interior sound detected by the noise detection microphone M1, the second harmonic component of the engine speed is phase-adjusted and the amplified sound is emitted from the speaker.

The sound generated by the speaker enters the ears of the driver and passengers together with the sound coming from the engine, which is a noise source, and the inside and outside of the vehicle. At the same time, these sounds are detected by the mute confirmation microphone M2. The output VB of the muffling confirmation microphone M2 is frequency-selected by the second frequency selector SCF11 that is the second frequency selecting means, and is sent to the microprocessing unit MPU as the signal PD1. Second frequency selector SC
F11 has the same configuration as the first frequency selector SCF1 and extracts only the signal in the frequency band corresponding to the second harmonic component of the engine speed.

Micro Processing Unit MPU
As described above, receives the signal from the second frequency selector SCF11 and sends it to the phase adjuster BBD1 with the clock frequency f.
1 and sends the gain K1 to the amplifier A1. The micro processing unit MPU operates according to the flowchart of FIG.

When the microprocessing unit MPU is started, the internal memory, the input / output port, etc. are first initialized in step 30, and then the phase adjusting step (steps 31 to 40) and the gain adjusting step (step 41). ~ 49) is repeated.

In the phase adjusting step, first, the power spectrum is calculated. The power spectrum is a distribution of frequency components representing the root mean square of the amount that fluctuates with time.

Normally, a switched capacitor filter SC
It is assumed that the signal passed through F11 is X (t), and T ≦ t ≦
Letting xt (t) be the signal observed only in section T, the power spectrum φxx (ω) is

[0040]

[Equation 5]

Here, XT (ω) represents the Fourier transform of xt (t), and E [] represents an expected value. In reality, it is impossible to make T → infinity, so the number of captured data n is used here. In this case, the power spectrum φxx
(Ω) is

[0042]

[Equation 6]

It is represented by

In step 31, the power spectrum φxx (ω) is obtained as described above, and the power spectrum φx is obtained.
xi. Next, the phase is adjusted to minimize the power spectrum. In step 32, the phase is advanced by Δθ from the current value. As a result, the phase adjuster BBD1 advances the phase of the signal output from the switched capacitor filter SCF1 by Δθ. Next, in step 33, the power spectrum φxxx is obtained again, and in step 34, it is determined whether the level has increased or decreased with respect to the previous value. If the level of the power spectrum φxxx decreases, it means that the phase has advanced.
Since it is connected to lowering i, the phase is changed to Δθ.
Only (step 38). In step 39, the power spectrum φxxi is obtained again, and the power spectrum φx is obtained.
Continue advancing the phase until xi reaches the minimum value. Step 3
If the power spectrum is higher than the previous value at 4, the phase is delayed and the power spectrum is lowered.
Also in this case, the phase is continuously delayed until the power spectrum φxxxi reaches the minimum value. When the power spectrum becomes the minimum, it is determined that the additional sound has the opposite phase to the noise.

Next, a gain adjusting step is performed. If the absolute values of the noise level and the additional sound level match, the noise level and the additional sound level cancel each other out, and the power spectrum becomes minimum. Therefore, a gain that minimizes the power spectrum is obtained as in the phase adjustment step. First, the gain is increased, and if the power spectrum increases, the gain continues to decrease, and if the power spectrum decreases, the gain continues to increase.
The gain adjustment step ends when the power spectrum becomes minimum.

As described above, in the frequency band of the range corresponding to the secondary component of the engine speed, the phase of the sound generated from the speaker and the phase of the sound detected by the sound deadening confirmation microphone M2 are minimized. By adjusting the gain, the noise that directly reaches the ear from the engine and the additional sound emitted from the speaker are canceled out, and the secondary component of the engine speed does not enter from the ear. In the above, the phase adjuster BBD1, the amplifier A1, the speaker SP,
The sound deadening confirmation microphone M2, the second frequency selector SCF11, and the microprocessing unit MPU constitute a footback system, and are configured as an antiphase sound imparting means for generating an antiphase sound with respect to noise.

In the case of a 6-cylinder engine, the noise distribution in the passenger compartment is as shown in FIG. In the figure, a, b, c, d, and e are the engine rotation first-order component, the 1.5th-order component, the second-order component, the 2.5th-order component, and the third-order component, respectively. If the first-order component, the 1.5th-order component, the second-order component, the 2.5th-order component, and the third-order component are deleted, the sound from the engine becomes clean and becomes easy to hear. FIG. 9 shows a second embodiment of the present invention in a 6-cylinder engine. The basic structure is the same as that of the first embodiment, and only the contents of the controller are different.

Controller 13 'in the second embodiment
Has five sets of a first frequency selector, a phase adjuster and an amplifier connected in series. The signal from the noise detection microphone M1 is branched to the respective first frequency selectors SCF1 to SCF5. The outputs of the amplifiers A1 to A5 are given to the adder ADD, which adds the respective outputs and sends the sound signal to the speaker SP.

The signal from the mute confirmation microphone M2 is branched into five signals, which are sent to the second frequency selectors SCF11 to SCF15, respectively. The signals PD1 to 5 from the second frequency selectors SCF11 to 15 are separately sent to the microprocessing unit MPU.

First frequency selectors SCF1-5 and second frequency selectors SCF1-5
The internal configuration of the frequency selectors SCF11 to 15 is the same as that of the first embodiment, but the number of frequency divisions in the frequency divider 23 is 100 in SCF1 and SCF11, and SCF2.
And SCF12 to 150, SCF3 and SCF
13 for 200 and SCF4 and SCF14 for 25
0 and SCF5 and SCF15 are set to 300 (see FIG. 3). Therefore, SCF2
And SCF12 correspond to SCF1 and SCF11 1.
It becomes a bandpass filter that selects a frequency of 5 times. Similarly, for SCF1 and SCF11, SC
F3 and SCF13 double, SCF4 and SCF1
4 is a bandpass filter that selects a frequency of 2.5 times, and SCF3 and SCF13 are frequencies that select a frequency of 3 times. As a result, in the second embodiment, noise can be reduced only in the frequency bands of the first-order component, the 1.5th-order component, the 2nd-order component, the 2.5th-order component, and the 3rd-order component of the engine rotation.

10 to 12 show an example of a flow chart showing the operation of the microprocessing unit MPU in the second embodiment. Here, the values of Y are sequentially updated in the range of 1 to 5 by steps 51 to 58. In PDY, FY, and KY in FIGS.
Values of ~ 5 are fitted. When Y is 1, the power spectrum of PD1 is calculated in the phase adjusting step, and the clock frequency f1 is adjusted to control the power spectrum to be minimum. In the gain adjusting step, the power spectrum of PD1 is calculated,
The gain K1 is adjusted so that the power spectrum is controlled to be minimum. As a result, noise reduction of the primary component of engine rotation is performed. Similarly, when Y is 2 to 5, the clock frequency and gain of each component are adjusted and controlled.

In the second embodiment, the adjustment of each component can basically be controlled independently. Therefore, if a unit capable of performing parallel processing is placed in the microprocessing unit MPU, or if five general-purpose microprocessors are arranged in parallel and processed, the processing can be performed at higher speed.

When processing is performed by one general-purpose microprocessor, it may be configured as in the following third embodiment. The structure of the controller 13 '' of the third embodiment is shown in FIG. The method of processing the output signal from the mute confirmation microphone M2 is different from that of the second embodiment.

In the third embodiment, the sound deadening confirmation microphone M is used.
The second output is frequency-selected by the second frequency selector SCF11 ′, and then the microprocessing unit MPU.
Sent to. Also, the micro processing unit M
The signal N is sent from the PU to the second frequency selector SCF11 '.

The internal structure of the second frequency selector SCF11 'is shown in FIG. The frequency divider 23 'is different from the first and second embodiments.
Signal N from the micro processing unit MPU
The difference is that is entered. The frequency divider 23 'divides the frequency according to the received value of N.

The value of N is determined in the microprocessing unit MPU. 15 to 17 are flowcharts of the microprocessing unit MPU of the third embodiment.
Shown in. Here, the value of N is set according to the value of Y.
N is 100 when Y is 1 and N is 150 when Y is 2.
When Y is 3, N is 200, and when Y is 4, N is 25
N is set to 0 and N is set to 300 when Y is 5. When the microprocessing unit MPU outputs the set N to the second frequency selector SCF11 ′, the second frequency selector SCF11 ′ causes the first-order component, the 1.5th-order component, the 2nd-order component, and the 2.5th-order component of the engine rotation. Corresponding ones of the components and the third-order components are extracted. The microprocessing unit MPU adjusts the phase and gain of the extracted component.

As described above, in the third embodiment, each component is adjusted in sequence, but the number of second frequency selectors is reduced by four compared with the second embodiment, resulting in low cost.

In the above second and third embodiments, the primary component, the 1.5th component, the secondary component, the 2.5th component and the tertiary component of the engine rotation are extracted and adjusted. If the component synchronized with the engine speed is transmitted to the driver and passengers as noise, the number of frequency selectors, phase adjusters and amplifiers corresponding to the component may be increased. In some vehicles, for example, if the secondary component of the engine rotation is not heard as noise in the passenger compartment, the number of frequency selectors, phase adjusters and amplifiers corresponding to the components may be reduced.

Although the first, second and third embodiments show the apparatus for reducing the engine noise in the vehicle, the present invention is not limited to the engine and the frequency of the noise portion changes according to the state of the noise source. It can also be applied to things that do. For example,
When reducing the engine noise in the cabin of an airplane,
It can be applied to a patient's bed in a hospital, and can be applied to various applications such as reducing noise generated by equipment such as treatment placed beside the bed. In this case, the noise of an arbitrary frequency band may be reduced by adjusting the clock of the switched capacitor filter. For vehicles, it is also effective in reducing the operating noise of the seat adjuster, the sliding noise of the wiper, the noise generated by the transmission during a shift change, the operating noise of the solenoid valve mounted on the vehicle, and the like.

When the present invention is installed in a vehicle, the noise reduction device of the present invention can be installed for each seat. In this case, it is advisable to provide a switch for permitting / prohibiting the operation of this device so that the individual seats can be switched. For example, the device can be operated for a person sleeping in the back seat, and the driver can turn off the device to check the engine sound or prevent drowsiness. Will be possible.

Further, in the above embodiment, when the gain is adjusted, the muting volume can be arbitrarily determined by adding or subtracting a constant such as the amount of the gain. According to this, the volume of the sound generated by the engine can be reduced rather than being muted, so that the state of the engine can be checked and the noise can be reduced, so that the driver can drive comfortably. The sound emitted from the speaker is not just an anti-phase sound, and the noise can be changed to the sound desired by the user.

[0062]

According to the present invention, the user does not want to erase all sounds heard by the user, but only the sound of a specific frequency emitted from the noise source is reduced. It doesn't erase even.

According to the present invention, since the transfer function estimation and the convolution operation are not performed, the response is good.

Further, in particular, since a high-speed arithmetic chip and a dedicated arithmetic chip are not required, it is possible to manufacture at low cost without using them.

Furthermore, if the constants of the apparatus can be changed, the noise can be changed to the sound desired by the user.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a structure of first and second frequency selectors according to first and second embodiments of the present invention.

[Fig. 4] Noise distribution inside a 4-cylinder vehicle

FIG. 5 is an operation explanatory diagram of a switched capacitor used in this embodiment.

FIG. 6 is a schematic circuit diagram of a switched capacitor filter used in this embodiment.

FIG. 7 is a flowchart of the microprocessing unit according to the first embodiment of the present invention.

FIG. 8: Noise distribution inside a 6-cylinder vehicle

FIG. 9 is a circuit diagram of a second embodiment of the present invention.

FIG. 10 is a flowchart of the microprocessing unit according to the second embodiment of the present invention.

11 is a flowchart of a subroutine of the phase adjustment routine of FIG.

FIG. 12 is a flowchart of a subroutine of the gain adjustment routine of FIG.

FIG. 13 is a circuit diagram of a third embodiment of the present invention.

FIG. 14 is a circuit diagram showing the structure of a second frequency selector according to the third embodiment of the present invention.

FIG. 15 is a flowchart of the microprocessing unit according to the third embodiment of the present invention.

16 is a flowchart of a subroutine of the phase adjustment routine of FIG.

FIG. 17 is a flowchart of a subroutine of the gain adjustment routine of FIG.

FIG. 18 is an explanatory diagram of a conventional technique using the adaptive control method.

FIG. 19 is an explanatory diagram of a conventional technique using a method of storing transfer functions in advance.

[Explanation of symbols]

 10 seat 11 headrest 12 engine 13 controller 14 backrest 20 phase difference detector 21 charge pump 22 loop filter 23 frequency divider 24 memory 25 noise detection microphone 26 transversal filter 27 speaker 28 silence confirmation microphone 29 adaptive algorithm A1-5 Amplifier ADD Adder C Capacitor M1 Noise detection microphone M2 Noise reduction confirmation microphone MPU Micro processing unit N Dividing value NND1-5 Phase adjuster PP Engine speed sensor Req Equivalent resistance value SCF Switched capacitor filter SCF1-5 First frequency selector SCF11 to 15 Second frequency selector SP speaker VCO voltage control oscillator Y variable φxx (ω), φxxxi power spectrum

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuro Sato 2-1-1 Asahi-cho, Kariya city, Aichi Prefecture Aisin Seiki Co., Ltd.

Claims (10)

[Claims] 1. A sound detecting means for detecting a sound generated by a noise source or a signal corresponding to the sound, and determining a frequency range corresponding to the noise in the sound generated by the noise source or the signal corresponding to the sound. Frequency range deciding means, first frequency selecting means for extracting only the set frequency range from the sound or signal detected by the sound detecting means, and inverse for generating a reverse phase sound of the signal passing through the first frequency selecting means. A noise reduction device comprising a phase sound imparting means. 2. A sound detecting means for detecting a sound generated by a noise source or a signal corresponding to the sound, and determining a frequency range corresponding to the noise in the sound generated by the noise source or the signal corresponding to the sound. Frequency range determining means, first frequency selecting means for extracting only the set frequency range from the sound or signal detected by the sound detecting means, phase adjusting means for adjusting the phase of the signal passing through the first frequency selecting means A gain adjusting means for changing the amplification factor of a signal passed through the first frequency selecting means, a speaker for producing a sound in the room based on the signals passing through the phase adjusting means and the gain adjusting means, and a muffling for detecting a sound in the room A confirmation microphone, a second frequency selection unit that extracts only the set frequency range from the signals detected by the mute confirmation microphone, and a signal that has passed through the second frequency selection unit. Control means for setting the gain of the phase and gain adjustment means of the phase adjusting means to the word spectrum minimize, the noise reduction apparatus comprising a. 3. A noise detection microphone for detecting a sound in a vehicle compartment, an engine speed sensor for detecting an engine speed, a frequency range determining means for determining a set frequency range according to a detection signal of the engine speed sensor, and a noise detection. First frequency selecting means for extracting only the set frequency range from the sound detected by the microphone, phase adjusting means for adjusting the phase of the signal passed through the first frequency selecting means, and passing through the first frequency selecting means A gain adjusting unit that changes the amplification of a signal, a speaker that produces a sound in the room based on the signal that has passed through the phase adjusting unit and the gain adjusting unit, a sound deadening confirmation microphone that detects the sound in the room, and a sound deadening confirmation microphone that detects the sound. Second frequency selecting means for extracting only the set frequency range of the signal, and a power spectrum of the signal passing through the second frequency selecting means. A noise reduction device for a vehicle interior, comprising: a control unit that sets the phase of the phase adjustment unit and the gain of the gain adjustment unit so as to minimize the torque. 4. The noise reducing device according to claim 2, wherein a switched capacitor filter is used for the first and second frequency selecting means. 5. The noise reduction device according to claim 2, wherein a bucket briquette device is used as the phase adjusting means. 6. The noise reduction apparatus for a vehicle interior according to claim 2, wherein the phase adjusting unit and the gain adjusting unit are arranged in series, and the gain adjusting unit adjusts the gain of the output of the phase adjusting unit. . 7. The noise in the vehicle interior according to claim 3, wherein the first frequency selecting means extracts a frequency band having a width including a frequency of an engine speed and / or a harmonic of the engine speed. Reduction device. 8. The first frequency selecting means, the phase adjusting means, and the gain adjusting means are frequency bands that give discomfort to humans among the respective frequency bands including the engine speed and the harmonic frequency of the engine speed. , The plurality of first frequency selecting means perform selection for each frequency band, and the noise reducing device passes through the plurality of phase adjusting means and gain adjusting means. 4. The noise reduction device for a vehicle interior according to claim 3, further comprising: an adding unit that adds the signals of the above, and the speaker generates a sound in the room based on an output value of the adding unit. 9. The noise reduction device for a vehicle interior according to claim 3, wherein the speaker and the sound deadening confirmation microphone are incorporated in a headrest portion of a seat. 10. The noise reduction device for a passenger compartment according to claim 3, wherein the speaker is incorporated in a headrest portion of a seat, and the sound deadening confirmation microphone is incorporated in a backrest portion of the seat.