JPH03203491A - Active type noise controller - Google Patents

Abstract

PURPOSE:To optionally change the sound pressure of a prescribed harmonic component at the observation point of a residual noise and to form the sound field of sound quality corresponding to a listerner's liking by allowing a harmonic component correcting means to optionally change the amplitude of a residual noise detecting signal detected by a residual noise detecting means. CONSTITUTION:Control sounds are generated from speakers 5a, 5b to be control sound sources to a noise transmitted from an engine 3 to be a noise source to allow respective sounds to interface with each other and the residual noise on the observation point is detected by microphones 6a to 6c to be a residual noise detecting means and the detection signals are supplied to the harmonic component correcting circuit 9. The circuit 9 corrects the amplitude of the prescribed harmonic component in the noise generation status detecting signal of the noise source detected by a crack angle sensor 7 to be a noise generation status detecting means and supplies the corrected RN detecting signal to processor units 15a, 15b to be control means to form a driving signal for adjusting the specific harmonic component of the residual noise at the observing point and supplies the driving signal to the control sound sources to generate control sounds. Consequently, the sound quantity of residual noise at the observation point an be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active noise control device, and in particular, improves the sound quality of noise by causing control sound generated by a control sound source to interfere with noise from a noise source. It is designed to change the
The present invention relates to a noise control device suitable for vehicle cabins and aircraft cabins.

[Prior Art] Conventionally, as this type of active noise control device, there is one described in, for example, Patent Application Publication No. 1-501344.

This conventional example is an active vibration control device for reducing vibrations generated by a first vibration sound a<noise R, which includes at least one selected harmonic of the first vibration sound source. One reference signal is supplied to a control means using an LMS algorithm that drives a plurality of second vibration sound sources (control sound sources), thereby controlling the vibration sound field formed by the first and second vibration sound sources. It is intended to reduce the vibrational energy detected by the sensor means which acts to sense the vibration.

(Problems to be Solved by the Invention) However, in the conventional active noise control device described above, although it is possible to reduce harmonic components contained in noise caused by periodic vibration sources, this is not fixed in advance. It is an unresolved problem that the sound quality of noise cannot be improved by increasing or decreasing the amplitude of any harmonic component depending on the taste of the person present in the sound field. was there.

Therefore, this invention was made by focusing on the unresolved problems of the conventional example described above, and it is possible to arbitrarily select the harmonic component to be reduced and change its amplitude, thereby improving the sound quality of noise. The purpose is to provide an active noise control device.

ci! l! Means for Solving the Problem] In order to achieve the above object, the active noise control device according to claim (1) allows control sound generated from a control sound source to interfere with noise transmitted from the noise source. In an active noise control device configured to reduce noise, a noise generation state detection means detects a signal related to a noise generation state of the noise source; a residual noise detection means detects residual noise at an observation position; harmonic component correction means for changing at least the amplitude of a predetermined harmonic component in the residual noise detection signal from the residual noise detection means based on the noise generation state detection signal of the state detection means; and control means for forming a drive signal for the control sound source based on the correction signal and the detection signal of the noise generation state detection means.

Further, in the active noise control device according to claim (2), the harmonic component correction means includes an amplitude selection means for selecting the amplitude of a harmonic component to be controlled, and an input signal from the amplitude selection means. The configuration includes an adding means for adding the selection signal and the residual noise detection signal of the residual noise detecting means.

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

[Operation] In the active noise control device according to claim (1), the control sound is emitted from the control sound source to interfere with the noise transmitted from the noise source, and the residual noise at the observation point at that time is reduced to a residual noise. The residual noise detection signal is detected by the noise detection means, and the residual noise detection signal is supplied to the harmonic component correction means.
By correcting the amplitude of a certain harmonic component of the noise generation state detection signal of the noise source detected by the noise generation state detection means and supplying the corrected residual noise detection signal to the control means, The sound quality of the residual noise at the observation point can be improved by applying a drive signal that adjusts a specific harmonic component of the residual noise and supplying this to the control sound source to generate the control sound.

Further, in the active noise control device according to claim (2), since the harmonic component correction means has a plurality of amplitude selection 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.

Furthermore, in the active noise control device according to claim (3), since the S width selection means is linked to the characteristic switching means for switching the suspension characteristics (for example, the damping force of the shock absorber that suppresses the roll of the vehicle), For example, when high damping force is selected for sporty driving, the sound quality emphasizes the low-order harmonics of the residual noise, and when low damping force is selected for soft driving, the low-order harmonics of the residual noise are emphasized. It is possible to automatically select the attenuated and calm sound quality and select the sound quality of the residual noise according to the driving condition.

〔Example〕

Embodiments of the present invention will be described below based on 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 the figure, l is a vehicle body, and a four-cylinder engine 3 as a noise source is disposed in front of a vehicle interior 2.

In the vehicle interior 2, a front seat 4F and a rear seat 4R are arranged, and a loudspeaker that also serves as a control sound source outputs an audio signal as a control sound source to the lower part of the dash board and to the rear side of the rear seat 4R, for example. 5a and 5b
Microphones 6a, 6b, and 6C as residual noise detection means are provided at the front, center, and rear of the ceiling, respectively.

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

The crank angle detection signal of the crank angle sensor 7 is
The reference signal generator 8 extracts one or more sine wave components in harmonics (or quasi-harmonics) of the rotation speed of the crankshaft and outputs them as a reference signal X. The reference signal X output from the reference signal generator 8 is supplied to a harmonic component correction circuit 9 as harmonic component correction means. This harmonic component correction circuit 9 includes a target signal generation circuit IO to which the reference signal X is input, a target signal eOL outputted from this target signal generation circuit 10, and residual noise detection signals outputted from the microphones 6a to 6c. e, and adders 11a to 11C. Here, as shown in FIG. 2, the target signal generation circuit IO includes a number of variable filters F, -F3 corresponding to the microphones 6a-6c, and a filter shape memory storing filter data of these variable filters F1-F3. M, and a variable filter F: to F3 outputs a target signal eo1(n) (!!, =1.2.3) expressed by the following equation (1).

eot(n) =Esin j (ω = 1φ)...
・・・・・・・・・(1) However, E is the amplitude and ω is the reference signal X
The angular frequency of , φ is the phase. Here, the amplitude E is preliminarily stored in the filter shape memory M for each variable filter F, such as the characteristic shown in FIG.

By setting the filter data so as to be obtained by the output of F3, the filter data is changed as shown in FIG. 3 according to the engine speed.

Then, the reference signal X output from the reference signal generator 8 and the residual noise correction signal eL'(n) output from the adders 11a to llc are sent to the processor units h15a and 1.
5b.

As shown in FIG. 4, the processor units 15a and 15b include an A/D conversion circuit 22 that A/D converts the input reference signal X and outputs it, and an A/D conversion circuit 22 that converts the input reference signal A digital filter 24 and an adaptive digital filter 26 which are input as the signal A microprocessor 34 inputs the converted signal by the D converter 30 and the output signal of the digital filter 24, and a D/A converter that converts the processed signal of the adaptive digital filter 26 from D/A.
A converter 36.

Here, the digital filter 24 inputs the reference signal X and generates a filtered reference signal rtm according to the number of combinations of transfer functions between the microphone and the speaker (see equations (5) and (6) described later). , and the adaptive digital filter 26 is functionally the speaker 5
It has individual filters according to the number of output channels to a and 5b, inputs the reference signal X manually, performs convolution processing based on the filter coefficient set at that time, and outputs the speaker drive signal y. It is something. The microprocessor 34 receives the residual noise correction signals el% e2 and e3/ and the filtered reference signal r- and is adapted to modify the filter coefficients of the adaptive filter 26 using the LMS algorithm.

Here, the control principle of each processor unit 15a and 15b will be explained using a general formula. Now, the residual noise detection signal detected by the second microphones 6a to 6C is eL.
(n), the residual noise detection signal detected by the first microphones 5a and 5b when there is no control sound (two-blow sound) from the loud speakers 5a and 5b is ept(n), m
jth (j=o) when the transfer function H0 between the loudspeakers 5a and 5b and the first microphones 6a to 6c is expressed as a FIR (finite impulse response) function.

1, 2...Ic-1), the filter coefficient corresponding to the term C5□, the reference signal x(n), and the adaptation that inputs the reference signal x(n) and drives the m-th loudspeaker 5a and 5b. i-th filter (i=o, l, 2...+-1)
If the coefficient of is W,... then yt (n) = ypt(n) +...
...(2) holds true. Here, all terms with (0) are sample values 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 example), Ic
is the number of taps (filter order) of the filter coefficient C0 expressed by the FIR digital filter, and lk is the number of taps (filter order) of the adaptive filter W.

In the above formula (2), “Σ Wl, x(n-j-4)” on the right side
The term l J (=ym) represents the output when the reference signal X is input to the adaptive filter 26, and is
The term x (n-j-i) It represents the signal when it reaches the microphones 6a to 6C, and furthermore, “Σ
Σ CL a j・ (Σ W m i・x (n-
j-i) ) The entire right side of J represents the sum of the two-blow sounds reaching the first microphones 6a to 6C, since the signals reaching the first microphones 68 to 6C are added up for all speakers.

Next, the evaluation function (variable to be minimized) Je is set as Je=
Σ (e-(n)) 2 ・・・・・・・・・
...(3).

In order to find the filter coefficient W1 that minimizes the evaluation function Je, this embodiment employs the LMS algorithm. In other words, the evaluation function Je is expressed as each filter coefficient W m
The filter coefficient Wllli is the value partially differentiated with respect to i.
Update.

Therefore, from equation (3), we get ・・・・・・・・・・・・(4), but from (2) 2, we get ・・・・・・・・・・・・(5) , If the right-hand side of (5) 2 is set as r, , (ni), then the filter coefficient rewriting formula including the weighting coefficient T can be obtained from the following equation (6) as 9w,, (n+
1) = wlI, (n) +・・・・・・・・・・・・
(6) Here, α is a convergence coefficient, and is involved in the speed at which the filter optimally converges and the stability at that time. Although the convergence coefficient α is treated as a single constant in this embodiment, it can also be a different convergence coefficient (C1,) for each filter coefficient, or a coefficient that incorporates the weighting coefficient T1 together. It can also be calculated as (αl).

In this way, the filter coefficients W, (n
+1) is the reference signal x based on the output of the residual noise detection signals y+(n) and yz(n) output from the microphones 6a to 6C and the crank angle detection signal of the crank angle sensor 7.
(n) based on L M S (Least Mea
nSquare) algorithm, the input residual noise correction signal el'(n) ~
Drive signals y+(n) and y2 that minimize el'(n)
(n), which is supplied to the loudspeakers 5a and 5b, and the control sound output from these improves the sound quality of the noise.

Next, the operation of the above embodiment will be explained. When the engine 3 is started, the crank angle sensor 7 outputs a crank angle detection signal with a frequency twice the engine speed, and this signal is manually input to the reference signal generator 8.
A reference signal X (-si
nωt) is output and supplied to the harmonic component correction circuit 9 and processor units 15a and 15b.

Therefore, in the harmonic component correction circuit 9, the variable filters F1 to F3 of the target signal generation circuit 10 read the filter data previously stored in the filter shape memory M based on the engine rotation speed, and adjust the filter data corresponding to the engine rotation speed. Set the filter shape.

As a result, as shown in FIG. 3, which is output from each of the variable filters F1 to F3, the target signal represented by (2) 2 is obtained by multiplying the reference signal X made of a sine wave by the amplitude E corresponding to the engine rotation speed. eol~e03 are adders 11 a~ll
It is output to c.

On the other hand, the microphones 6a to 6C output residual noise detection signals C1 to e3 in the vehicle interior 2, and these signals are added to a
This adder 11
Residual noise detection signals e to eJ and target signal e in a-11c.

I-e03 is added individually to obtain a residual noise correction signal e,
“-e3” is output, which is the processor unit 1
5a and 15b.

In these processor units 15a and 15b, drive signals y and y2 are formed so that the sum of squares of the residual noise correction signals el' to e, / is minimized according to the time-domain LMS algorithm described above, and these drive signals y and By outputting y2 to the loudspeakers 5a and 5b, control sounds are generated from these loudspeakers 5a and 5b, thereby controlling the input residual noise correction signals e~e, / so that they are always zero. will be held. That is, the amplitude of the residual noise detection signals e, ~e3 input to the adder 11a-1ie is the target signal cot~(!
It will be controlled to match 0:l. Therefore, as described above, the outputs of the variable filters F, ~F, and I of the harmonic component correction circuit 9 are set so as to obtain an amplitude E proportional to the engine rotation speed, as shown in FIG. Assuming that, in a region where the engine rotation speed is low, the amplitude E of the harmonic component is small, so the harmonic component at the observation point becomes smaller, and as the engine rotation speed increases, the harmonic component at the observation point becomes smaller. The 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. 5 and 6.

In this second embodiment, the sound quality of the residual noise in the vehicle interior 2 can be adjusted to a level of II according to the preference of the occupants seated in the seats 4F and 4R.

That is, as shown in FIG. 5, harmonic components of even orders (2, 4, 6, . . . ) are output from the reference signal generator 8, and a harmonic correction circuit 9a is configured to separately provide these harmonic components. 9b
Residual noise correction signals el, 82' and e are input to the harmonic correction circuits 9a, 9b, 9c, .

are supplied to a pair of processor units 15a and 15b, respectively, and drive signals output from these processor units 15a and 15b are added by an adder 39 and output to loudspeakers 5a and 5b. Here, an example is shown in which a plurality of sets of processor units 15a and 15b are provided, but the outputs of the harmonic correction circuits 9a, 9b, . . . may be selected as one set using a changeover switch.

In addition, as shown in FIG. 6, a plurality of characteristics (straight lines 1., - 1:l) as variable filter F.

-F:l are stored so that these filter data can be selected by a manual changeover switch 40 provided near the driver's seat or each seat.

According to this second embodiment, by selecting the characteristic of the harmonic amplitude E with respect to the engine rotational order using the manual switch 40, the sound quality of the residual noise at the microphone positions 6a to 6C can be arbitrarily changed according to the passenger's preference. Something happens.

In the second embodiment, a case has been described in which the sound quality of the residual noise is selected using the manual switch 40, but the present invention is not limited to this. It can also be a switch that is linked to the force changeover switch. In this case, if you want to increase the damping force for sporty driving, select the direct vA1 shown in Figure 6 and compare the amplitudes of the harmonic components of each even order. If you want to increase the even-order harmonic components of the residual noise by increasing the target and lower the damping force to achieve soft running, select the straight line shown in Figure 6 and compare the amplitudes of each even-order harmonic component. When the damping force is selected to create a quiet environment by reducing the damping force, the residual noise can be selected between the two by selecting straight line 12 in Fig. 6, and the sound field is created according to the driving condition of the vehicle. can be formed.

Further, in the second embodiment, a four-cylinder engine has been described, but for a six-cylinder engine, the third-order component of engine rotation and its height 11'11. n';i.

need to be changed to minutes.

Furthermore, in each of the above embodiments, the case where the amplitude of the harmonic is changed has been described, but in addition to this, the phase may also be changed, and in this case, the sound quality can be changed with less power. There are advantages.

Furthermore, in each of the above embodiments, the case where the amplitude of even-order harmonic components is arbitrarily changed has been described, but the same applies to odd-order harmonic components as well. The $ signal generator 8 extracts each odd-numbered harmonic, supplies it to a harmonic component correction circuit, and also supplies it to the processor units loa and 10b.
Furthermore, by setting the amplitude E to zero in the harmonic component correction circuit, these odd-order harmonic components are reduced. The inventor's experiments have confirmed that by reducing the odd harmonic components in this way, the sound quality of the residual noise at the observation point is improved (see SAFE Technical Paper Series 870955, pages 53 to 62). .

Further, the number of installed loudspeakers as control sound sources and microphones as residual noise detection means is not limited to the above embodiment, and the number of installed windows may be one or more.

Furthermore, in each of the above embodiments, the case where the four-cylinder engine 3 is applied as the noise source has been described, but the present invention is not limited to this. Pickup signals for wind noise, pickup signals for differential gear and transmission case vibrations (No. 13 correlated with noise caused by case vibrations in the drive power transmission system), and response to the rotation of the transmission output shaft for measuring vehicle speed. It may be a multi-channel system that also incorporates pulse signals (signals correlated with noise caused by meshing of transmissions and differential gears), or it may be a combination of any of these.

Furthermore, in the above embodiment, the case where the present invention is applied to a vehicle has been described, but the present invention is not limited to this. For example, the case where the engine noise in the cabin of an aircraft is reduced, It can also be applied to reduce indoor noise caused by the rotation of motor vehicles.

Furthermore, in the above embodiments, the case where the noise source is outside a kind of closed space called the passenger compartment has been explained, but this invention is not limited to this, and the present invention can also be applied to the case where the noise d is inside a closed space. It goes without saying that it can be done.

Furthermore, in each of the above embodiments, the algorithm for updating the filter coefficients of the adaptive digital filter is a frequency 19. S
Other algorithms can be applied, such as the R-region LMS algorithm.

(Effects of the Invention) As explained above, according to the active noise control device according to claim (1), the amplitude of the residual noise detection signal detected by the residual noise detection means is arbitrarily changed by the harmonic component correction means. Since the sound pressure of a predetermined harmonic component can be arbitrarily changed at the residual noise observation point, it is possible to form a sound field with sound quality that matches the listener's preference. The effect is that a more comfortable acoustic space can be obtained.

Further, according to the active noise control device according to claim (2), since the harmonic component correction means is provided with amplitude selection means such as a manual switch for selecting the amplitude of the harmonic component to be controlled, the listener can By selecting the amplitude selection means, it is possible to select any sound quality according to one's preference.

Furthermore, according to the active noise control device according to claim (3), since the amplitude selection means is linked with the switching means for switching the suspension characteristics of the vehicle, the sound quality can be automatically changed according to the running condition of the vehicle. You can get the desired effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram showing an example of a target signal generation circuit, and FIG.
The figure is a characteristic diagram showing the relationship between the engine rotation speed and the widening of harmonic components, Figure 4 is a block diagram showing an example of Prosensor Uni 7h, and Figure 5 is a block diagram showing the second embodiment of the present invention. 6 are characteristic diagrams showing the relationship between the engine rotational order and the amplitude of harmonic components in the second embodiment. In the diagram, 1 is the vehicle body, 2 is the passenger compartment, 3 is the 4-cylinder engine, and 5a
, 5b is a loudspeaker (control sound R), 6a to 6c are microphones (residual noise detection means), 7 is a crank angle sensor (noise generation state detection means), 8 is a reference signal generator,
9.9a, 9b... are harmonic component correction circuits (harmonic component correction means), 1O is a target signal generation circuit, 1la
-11 and c 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. Patent distributor Nissan Motor Co., Ltd.

Claims (3)

[Claims] (1) In an active noise control device that reduces noise by causing control sound generated from a control sound source to interfere with noise transmitted from a noise source, noise that detects a signal related to the noise generation state of the noise source. a generation state detection means; a residual noise detection means for detecting residual noise at an observation position; harmonic component correction means for changing at least the amplitude of a harmonic component; and control means for forming a drive signal for the control sound source based on a correction signal of the harmonic component correction means and a detection signal of the noise generation state detection means. An active noise control device characterized by comprising: (2) The harmonic component correction means includes an amplitude selection means for selecting the amplitude of the harmonic component to be controlled, and an addition means for adding the amplitude selected by the amplitude selection means to the residual noise detection signal. The active noise control device according to claim (1). (3) Claim (2), wherein the amplitude selection means is interlocked with characteristic switching means for switching suspension characteristics of the vehicle.
The active noise control device described.