JP2748625B2 - Active noise control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control device, and more particularly to a sound quality of a noise by causing a control sound generated by a control sound source to interfere with noise from a noise source. The present invention relates to a noise control device suitable for a vehicle cabin or an aircraft cabin.

[Conventional technology]

Conventionally, as an active noise control device of this type, there is one described in, for example, Japanese Patent Application Laid-Open No. 1-501344.

This prior art is an active vibration control device for reducing vibrations generated by a first vibration source (noise source), wherein at least one of the first vibration sources includes at least one selected harmonic. The two reference signals are supplied to control means using an LMS algorithm for driving a plurality of second vibration sound sources (control sound sources), thereby generating a vibration sound field formed by the first and second vibration sound sources. The vibration energy detected by the sensor means acting to sense is reduced.

[Problems to be solved by the invention]

However, in the above-mentioned conventional active noise control device, it is possible to reduce the harmonic component contained in the noise due to the periodic vibration source, but this reduces the specific harmonic component fixed in advance. However, there is an unsolved problem that it is not possible to improve the sound quality of noise by increasing or decreasing the amplitude of an arbitrary harmonic component depending on the taste of a person existing in the sound field.

Therefore, the present invention has been made by focusing on the unsolved problem of the conventional example, and it is possible to arbitrarily select a harmonic component to be reduced, change its amplitude, and improve the sound quality of noise. An object is to provide an active noise control device.

[Means for solving the problem]

In order to achieve the above object, an active noise control device according to a first aspect of the present invention is an active noise control device that reduces noise by causing a control sound generated from a control sound source to interfere with noise transmitted from a noise source. A noise generation state detecting means for detecting a signal relating to a noise generation state of the noise source, a residual noise detection means for detecting residual noise at an observation position, and a noise generation state detection of the noise generation state detection means. A target signal for changing at least the amplitude of a predetermined harmonic component in the residual noise detection signal from the residual noise detection means is formed based on the signal, and a correction signal based on the target signal and the residual noise detection signal is output. Harmonic component correction means,
A control for calculating a drive signal for forming the control sound by performing predetermined arithmetic processing based on the correction signal of the harmonic component correction means and the detection signal of the noise generation state detection means, and outputting the drive signal to the control sound source Means.

Further, in the active noise control device according to claim (2), the harmonic component correcting means includes an amplitude selecting means for selecting an amplitude of a harmonic component to be controlled, and an amplitude selecting means for selecting an amplitude of the harmonic component to be controlled. An adder for adding the selection signal and the residual noise detection signal of the residual noise detector is provided.

Further, in the active noise control device according to claim (3), the amplitude selecting means is configured to be linked with a characteristic switching means for switching a suspension characteristic of the vehicle.

[Action]

In the active noise control device according to claim (1),
The control sound source emits a control sound against the noise transmitted from the noise source to cause interference, the residual noise at the observation point at that time is detected by the residual noise detection means, and the residual noise detection signal is corrected for harmonic components. Supply means. In this harmonic component correction means, a target signal for changing at least the amplitude of a specific harmonic component in the residual noise detection signal is formed based on the noise generation state detection signal of the noise source detected by the noise generation state detection means, A correction signal based on the target signal and the residual noise detection signal is output to the control unit, and the control unit forms a drive signal based on the correction signal and the noise generation state detection signal, and supplies the drive signal to a control sound source for control. By generating a sound, the amplitude of the residual noise detection signal and the amplitude of the target signal are matched to change the sound pressure of a specific harmonic component at the observation point, thereby improving the sound quality of the residual noise at the observation point. .

Further, in the active noise control device according to claim (2), since the harmonic component correcting means has a plurality of amplitude selecting means for selecting the amplitude of the harmonic component to be controlled, the listener at the observation point By selecting the amplitude selection means,
The sound quality of the residual noise can be adjusted according to preference.

Further, in the active noise control device according to claim (3), the amplitude selecting means is interlocked with the characteristic switching means for switching the suspension characteristics (for example, the damping force of the shock absorber for suppressing the roll of the vehicle). When high-damping force is selected for sporty driving, the sound quality emphasizes low-order harmonics of residual noise.When low-damping force is selected for soft driving, low-order harmonics of residual noise are attenuated. Then, the gentle sound quality is automatically selected, and the sound quality of the residual noise according to the traveling state can be selected.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a front engine front wheel drive vehicle.

In FIG. 1, reference numeral 1 denotes a vehicle body, and a four-cylinder engine 3 as a noise source is disposed in front of a cabin 2. A front seat 4F and a rear seat 4R are provided in the passenger compartment 2, and a loudspeaker which also serves as a control sound source for outputting an audio signal as a control sound source, for example, at a lower portion of the dashboard and behind the rear seat 4R. Speakers 5a and 5b are provided, and microphones 6a, 6b and 6c as remaining noise detecting means are provided at the front, center and rear of the ceiling, respectively.

Further, a crank angle sensor 7 as a noise generation state detecting means is attached to the engine 3, and a noise generation state detection signal consisting of one pulse is output from the crank angle sensor 7 every time the crankshaft rotates 180 degrees. You.

Then, the crank angle detection signal of the crank angle sensor 7 is supplied to a reference signal generator 8 which generates one or more sine wave components in a harmonic (or quasi-harmonic) of the rotation speed of the crankshaft. And outputs this as the reference signal x. The reference signal x output from the reference signal generator 8 is supplied to a harmonic component correction circuit 9 as a harmonic component correction unit. This harmonic component correction circuit 9
A target signal generation circuit 10 to which the reference signal x is input, a target signal e _OL output from the target signal generation circuit 10, and an adder for adding a residual noise detection signal e _L output from the microphones 6a to 6c. 11a to 11c. Here, the target signal generating circuit 10, as shown in FIG. 2, a variable filter F ₁ to F ₃ of the number corresponding to the microphone 6 a to 6 c, storing filter data for these variable filters F ₁ to F ₃ And a target signal e _OL (n) (l = 1, 2, 3) represented by the following equation (1) is output by the variable filters F _{1 to} F ₃ .

e _OL (n) = Esin j (ωt + φ) (1) where E is the amplitude, ω is the angular frequency of the reference signal x, and φ is the phase. Here, the amplitude E is stored in advance in the filter shape memory M so that, for example, the characteristics shown in FIG. 3 showing the relationship between the engine speed and the amplitude E can be obtained from the outputs of the variable filters F _{1 to} F _3. By setting, it is changed as shown in FIG. 3 according to the engine speed.

The reference signal x output from the reference signal generator 8 and the residual noise correction signal output from the adders 11a to 11c
e _L ′ (n) is input to the processor units 15a and 15b.

As shown in FIG. 4, the processor units 15a and 15b perform A / D conversion of the input reference signal x and output the same, and reference the output signal of the A / D conversion circuit 22 as a reference. A digital filter 24 and an adaptive digital filter 26 input as a signal x, an A / D converter 30 for A / D converting the residual noise correction signals e ₁ ′ to e ₃ ′ from the harmonic component correction circuit 9, A microprocessor 34 for inputting a conversion signal by the / D converter 30 and an output signal of the digital filter 24,
D / A for D / A conversion of the processing signal of the adaptive digital filter 26
And a converter 36.

Here, the digital filter 24 receives the reference signal x, and filters the reference signal r _Lm according to the number of combinations of transfer functions between the microphone and the speaker (see the later-described equations (5) and (6)). ), And the adaptive digital filter 26 functions functionally with the speakers 5a and 5b.
Have filters corresponding to the number of output channels to
It receives a reference signal x, and outputs a speaker driving signal y ₁ performs processing convolution based on filter coefficients that are set at that time. The microprocessor 34
The residual noise correction signals e ₁ ′, e ₂ ′ and e ₃ ′ and the filtered reference signal r _Lm are input, and the filter coefficients of the adaptive filter 26 are changed using the LMS algorithm.

Here, the control principle of each processor unit 15a and 15b will be described using a general formula. Now, the residual noise detection signal detected by the l-th microphones 6a to 6c is e _L (n), and the l-th microphones 5a and 5b when there is no control sound (secondary sound) from the loudspeakers 5a and 5b are output. The detected residual noise detection signal is represented by e _PL (n), and the transfer function between the m-th loudspeakers 5a and 5b and the l-th microphones 6a to 6c.
J when H _Lm is represented by FIR (finite impulse response) function
The filter coefficient C _Lmj , the reference signal x (n), and the reference signal x (n) corresponding to the (j = 0,1,2... Ic-1) term are input and the m-th loudspeakers 5a and 5b are input. Let W _mi be the ith (i = 0,1,2... Ik−1) coefficient of the adaptive filter that drives Holds. Here, each term with (n) is a sample value at sampling time n, L is the number of microphones 6a to 6c (three in this embodiment), and M is the number of loudspeakers 5a and 5b. (2 in this embodiment), Ic is the number of taps of the filter coefficient C _Lm expressed in FIR digital filter (filter order), Ik is the number of taps of the adaptive filter W _m (filter order).

In the above equation (2), “Σ W _mi · x (n−j−
i) The term “｝” (= y _m ) represents the output when the reference signal x is input to the adaptive filter 26, and “ΣC _Lmj · ｛ΣW _mi · x
(N-j-i)｝ ”means that the signal energy input to the m-th speakers 5a and 5b is output as acoustic energy from these speakers 5a and 5b, and the transfer function C _Lm in the vehicle interior 3
Via represents the signal when it reaches the l-th microphone 6 a to 6 c, further _{"Σ ΣC Lmj · {ΣW mi ·} x (n
-Ji) The entire right side of {} is the l-th microphone.
Since the signals reaching the microphones 6a to 6c are added for all the speakers, the sum of the secondary sounds reaching the l-th microphones 6a to 6c is shown.

Next, the evaluation function (variable to be minimized) Je is far.

Then, for determining the filter coefficients W _m of the evaluation function Je minimized, in the present embodiment employs the LMS algorithm. In other words, the evaluation function Je a value obtained by partially differentiating each filter coefficient W _mi updates the filter coefficient W _mi.

Therefore, from equation (3), From equation (2). Therefore, if the right side of the equation (5) is r _Lm (n−i), the rewriting equation of the filter coefficient is obtained by the following equation (6) including the weight coefficient γ _L.

Here, α is a convergence coefficient, which is related to the speed at which the filter converges optimally and the stability at that time. Although the convergence coefficient α is treated as one constant in this embodiment, a different convergence coefficient (α _mi ) may be used for each filter coefficient, and the weight coefficient γ _L may be taken together. It can also be calculated as a coefficient (α _L ).

Thus, the filter coefficient W _mi (n
+1) to the basis of the reference signal x (n) based on the crank angle detection signal and the output of the crank angle sensor 7 of the residual noise detecting signal y ₁ output from the microphone 6 a to 6 c (n) and y ₂ (n) LMS (Least Mean Square) driving signal y that minimizes the input residual noise correction signals e ₁ ′, (n) to e ₃ ′ (n) by sequentially updating them.
₁ (n) and y ₂ (n) is formed which is the sound quality of the noise is improved by loudspeakers 5a and control sound yet to be output is supplied to the b.

Next, the operation of the above embodiment will be described. When the engine 3 is started, when the crank angle sensor 7 detects
Since a crank angle detection signal having a double frequency is output and input to the reference signal generator 8, the sine of the harmonic of the order to be controlled (even order in the four-cylinder engine 3) is output from the reference signal generator 8. Reference signal x (= sin) composed of wave components
ωt) is output and supplied to the harmonic component correction circuit 9 and the processor units 15a and 15b.

Therefore, the harmonic component correction circuit 9 reads a filter data previously stored in the filter shape memory M based on the engine rotational speed by the variable filter F ₁ to F ₃ of the target signal generating circuit 10, the engine rotational speed Set the filter shape corresponding to. As a result, each of the variable filters F _{1 to} F ₃
As shown in FIG. 3, the target signals e _{O1 to} e _O3 expressed by the above equation (2) obtained by multiplying the amplitude E corresponding to the engine speed by the sine wave reference signal x are added to the adder 11a. ~ 11c
Is output to

On the other hand, from the microphone 6a~6c residual noise detecting signals e ₁ to e ₃ in the passenger compartment 2 is output, these adders 11a~11c
Since supplied to this adder 11a~11c the residual noise detecting signals e ₁ to e ₃ and the target signal e _O1 to e _O3 and individually added to the residual noise correction signal e ₁ '~e _3' output This is supplied to the processor units 15a and 15b.

In these processor units 15a and 15b, the residual noise correction signal is obtained according to the time domain LMS algorithm described above.
The drive signals y ₁ and y _{1 are set} so that the sum of squares of e ₁ ′ to e ₃ ′ is minimized.
y ₂ is formed, by these drive signals y ₁ and y ₂ is output to each loudspeaker 5a and 5b, these control sound from loudspeakers 5a and 5b are generated, the residual noise correction signal thereby is input Control is performed so that e ₁ ′ to e ₃ ′ are always zero. That is, the amplitude of the residual noise detection signals e _{1 to} e ₃ input to the adders 11a to 11c is equal to the target signal e _O1
It will be controlled so as to coincide with e _O3 . Therefore, as the output of the variable filter F ₁ to F ₃ harmonic component correction circuit 9 as described above is shown in Figure 3, which amplitude E in proportion to the engine rotational degree is set so as to obtain Then, since the amplitude E of the harmonic component is small in a region where the engine rotation speed is low, the harmonic component at the observation point becomes small, and the harmonic component at the observation point increases as the engine rotation speed increases. That is, harmonic components can be controlled according to the engine speed.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the second embodiment, the sound quality of the residual noise in the cabin 2 can be selected according to the preference of the occupant seated in the seats 4F and 4R.

That is, as shown in FIG. 5, even-order (2, 4, 6,...) Harmonic components are output from the reference signal generator 8, and harmonic components are separately provided for the harmonic correction circuits 9a, 9b, 9c. , And the residual noise correction signals e ₁ ′ to e ₂ ′ and e ₃ ′ output from the harmonic correction circuits 9a, 9b, 9c... Are supplied to a pair of processor units 15a, 15b, respectively. The drive signals output from these processor units 15a and 15b are added to an adder 39.
And outputs the result to the loudspeakers 5a and 5b. Here, the processor units 15a and 15b
Are provided as a set, the outputs of the harmonic correction circuits 9a, 9b,... May be selected as one set by a changeover switch.

Further, each harmonic component correction circuit 9a, 9b, the filter shape memory M of ..., as shown in FIG. 6, a plurality of characteristics that the amplitude E differs for advance engine rotational order (linear l ₁ to l ₃₎
The stores the filter data to output variable filter F ₁ to F _3, the filters data is selectably configured manually change-over switch 40 provided in the vicinity of the driver's seat or each seat.

According to the second embodiment, the sound quality of the residual noise at the microphones 6a to 6c is arbitrarily changed according to the occupant's preference by selecting the characteristic of the harmonic amplitude E with respect to the engine rotation order by the manual switch 40. I can do it.

In the second embodiment, the case where the sound quality of the residual noise is selected by the manual switch 40 has been described. However, the present invention is not limited to this. For example, the damping force for selecting the damping force of the variable damping force shock absorber is described. It is also possible to use a switch linked to a changeover switch. In this case, when sporty running with increased damping force, select the straight line l ₁ in FIG. 6 and compare the amplitude of each even-order harmonic component. target greatly by increasing the even-order harmonic components of the residual noise, when performing a soft running with a lower damping force, the amplitude of the selected linear l ₃ of Figure 6 harmonic component of each even order embraces relatively small to quiet environment, when selecting the middle damping force, select a straight line l ₂ of FIG. 6 can select an intermediate residual noise of both according to the running state of the vehicle Form a sound field It is possible.

In the above-described second embodiment, a four-cylinder engine has been described. However, for a six-cylinder engine, it is necessary to change to the tertiary component of engine rotation and its harmonic components shown in FIG.

Further, in each of the above embodiments, the case where the amplitude of the harmonic is changed has been described. In addition, the phase may be changed, and in this case, the sound quality can be changed with a small power. There are advantages.

Furthermore, in each of the above embodiments, the case where the amplitude of the even-order harmonic component is arbitrarily changed has been described.
With respect to the odd harmonic components, the reference signal generator 8 extracts each odd harmonic and supplies the extracted harmonics to the harmonic component correction circuit and the processor units 10a and 10b. By setting E to zero, these odd-order harmonic components are reduced. It has been confirmed by experiments by the present inventors that the sound quality of the residual noise at the observation point is reduced by reducing the odd-order harmonic components in this way (SAE technical paper series).
870955 See pages 53-62).

Further, the number of loudspeakers as control sound sources and the number of microphones as residual noise detecting means are not limited to those in the above-described embodiment, but may be any number equal to or more than one.

Further, in each of the embodiments described above, the case where the four-cylinder engine 3 is applied as the noise source has been described. However, the present invention is not limited to this, and the pickup signal of the suspension vibration correlated with the road noise and the windbreak near the door mirror Sound pickup signal, pickup signal for differential gear and transmission case vibration (signal correlated with noise caused by case vibration of driving force transmission system), pulse signal according to rotation of transmission output shaft for vehicle speed measurement (A signal correlated with noise caused by meshing of the transmission and the differential gear) may be used, or a combination of any of these channels may be used.

Furthermore, in the above-described embodiment, the case where the present invention is applied to a vehicle has been described. However, the present invention is not limited to this. For example, a case where engine noise of a cabin of an aircraft is reduced or a plurality of outdoor units for air conditioning are used. The present invention can also be applied to a case where the indoor noise caused by the rotation of the vehicle is reduced.

Furthermore, in the above-described embodiment, the case where the noise source is outside a kind of closed space such as a vehicle compartment has been described. However, the present invention is not limited to this, and the present invention is applied to a case where the noise source is inside a closed space. It goes without saying that you get it.

Further, in each of the above embodiments, the update algorithm of the filter coefficient of the adaptive digital filter is the LMS in the frequency domain instead of the LMS algorithm in the time domain described above.
Other algorithms, such as algorithms, can be applied.

〔The invention's effect〕

As described above, according to the active noise control device of the first aspect, the amplitude of the residual noise detection signal detected by the residual noise detection means is changed by the harmonic component correction means to the noise of the noise generation state detection means. A correction signal based on the target signal for changing at least the amplitude of at least a predetermined harmonic component in the residual noise detection signal formed based on the occurrence state detection signal and the residual noise detection signal is output to the control unit, and the control unit corrects the signal. Since the drive signal is formed based on the signal and the noise generation state detection signal, the amplitude of the residual noise detection signal and the amplitude of the target signal are made to match, and the sound pressure of the specific harmonic component at the observation point is adjusted. The sound quality of the residual noise at the observation point can be improved by changing it, and the sound pressure of the harmonic component at the observation point can be changed arbitrarily by changing the amplitude of the target signal arbitrarily. According to It is possible to form a sound field of quality,
The effect that a more comfortable acoustic space can be obtained is obtained.

According to the active noise control device of the present invention, since the harmonic component correcting means is provided with an amplitude selecting means such as a manual switch for selecting the amplitude of the harmonic component to be controlled, By selecting the amplitude selecting means, the user can select any sound quality according to his / her preference.

Further, according to the active noise control device of the third aspect, the amplitude selecting means is linked with the switching means for switching the suspension characteristics of the vehicle, so that the sound quality is automatically changed according to the running state of the vehicle. The effect that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing an example of a target signal generation circuit, FIG. 3 is a characteristic diagram showing a relationship between an engine speed and the amplitude of a harmonic component, FIG. 4 is a block diagram showing an example of a processor unit, and FIG. FIG. 6 is a block diagram showing a second embodiment of the present invention, and FIG. 6 is a characteristic diagram showing the relationship between the engine rotational order and the amplitude of harmonic components in the second embodiment. In the figure, 1 is a vehicle body, 2 is a cabin, 3 is a 4-cylinder engine, 5a, 5
b is a loudspeaker (control sound source), 6a to 6c are microphones (residual noise detecting means), 7 is a crank angle sensor (noise generating state detecting means), 8 is a reference signal generator, 9, 9a, 9b
…… is a harmonic component correction circuit (harmonic component correction means), 10
Is a target signal generating circuit, 11a to 11c are adders, 15a and 15b are processor units, 24 is a digital filter, 26 is an adaptive digital filter, 34 is a microprocessor, and 40 is a manual switch.

Claims (3)

(57) [Claims] 1. An active noise control device for reducing noise by causing a control sound generated from a control sound source to interfere with noise transmitted from a noise source, wherein a signal relating to a noise generation state of the noise source is detected. Noise occurrence state detecting means,
A residual noise detecting means for detecting residual noise at the observation position; and a specific harmonic to be controlled in the residual noise detection signal from the residual noise detecting means based on the noise generating state detection signal of the noise generating state detecting means. Harmonic component correction means for forming a target signal for changing at least the amplitude of the component and outputting a correction signal based on the target signal and the residual noise detection signal; a correction signal of the harmonic component correction means and the noise generation state Control means for performing a predetermined calculation process based on the detection signal of the detection means to calculate a drive signal for forming the control sound, and outputting the drive signal to the control sound source. apparatus. 2. An amplitude selecting means for selecting an amplitude of a harmonic component to be controlled, and an adding means for adding the amplitude selected by the amplitude selecting means to a residual noise detection signal. The active noise control device according to claim 1, further comprising: 3. The active noise control device according to claim 2, wherein said amplitude selecting means is interlocked with characteristic switching means for switching suspension characteristics of the vehicle.