JPH03203490A - Active type noise controller - Google Patents

Abstract

PURPOSE:To obtain an acoustic space in the high quality with noise reduced state by controlling a control sound source driving means so that the sum of the sum of squares of respective detection signals from plural noise sensors and the square of a difference between the detecting signals of plural noise sensors corresponding to plural observing positions is minimized. CONSTITUTION:Residual noise levels on plural prescribed observing positions in the acoustic space are detected by plural noise sensors and applied to a control sound control means 16. The means 16 controls the control sound source driving means based on plural residual noise detecting signals and the noise generating states of noise sources so that the sum of the sum of respective squares of plural residual noise detecting signals and the square of the difference between residual noise detecting signals corresponding to required plural observing positions is minimized and generates control sounds from respective control sound sources 18a to 18d. Thereby, offset sounds and noises interfere with each other and the noise level on the whole observing positions can be reduced. In addition, a sound pressure level difference between required plural observing positions can also be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active noise control device that reduces noise transmitted to an acoustic space such as a vehicle interior by interference with control sound, and particularly relates to an active noise control device that reduces noise transmitted to an acoustic space such as a vehicle interior. The present invention relates to an active noise control device that also takes into account the control of noise level differences between multiple observation positions in space.

[Prior Art] Conventionally, as this type of active noise control device, for example, a device described in British Patent Publication No. 2149614 is known. This conventional device is applied to aircraft cabins and similar closed spaces, and includes multiple loudspeakers (secondary sound sources) and microphones installed inside the closed space, and an engine etc. located outside the closed space. The frequency r of a single noise source (-order sound source). -f, and a signal processor that controls driving of the plurality of loudspeakers based on the detection signals of the plurality of microphones and the detection signal of the frequency detection means. The signal processor generates detection signals P7 (n=1.2...1) of the plurality of microphones.
m), that is, the sum of squares of sound pressure P, is set as an evaluation function, and the phase of the control sound from the loudspeaker is controlled so as to minimize this evaluation function P8. As a result, the secondary sound generated from the loudspeaker and the primary sound transmitted from the noise source interfere with each other, thereby reducing residual noise at the observation position in the closed space.

[Problem to be solved by the invention]

However, since the conventional device described above was a control method that simply minimized the sum of the noise levels at each observation position, even if the sum was the minimum, there was a significant difference in the sound pressure level between the positions of the occupant's ears, for example. In such cases, passengers may feel uncomfortable, and it is not necessarily possible to control sound pressure level differences at multiple desired observation positions, making it impossible to achieve high-quality noise reduction for the entire acoustic space such as a single passenger cabin. was in a state.

The present invention was made by paying attention to the situation faced by such conventional devices, and the problem to be solved is to minimize the overall noise at each observation position in the acoustic space, and to The objective is to minimize the difference in sound pressure levels between observation points, maintain a balance between the observation points, and obtain an acoustic space with high quality noise reduction.

[Means to solve the problem]

In order to solve the above problem, in the invention described in claim (1), as shown in FIG. A plurality of noise sensors that individually detect residual noise at observation positions, a control sound source capable of outputting control sound to the acoustic space, a control sound source driving means for driving the control sound source, and detection signals of the plurality of noise sensors. and a signal corresponding to the noise generation state of the noise source, the sum of the squares of the respective detection signals of the plurality of noise sensors and the square of the difference of the detection signals between the noise sensors corresponding to the plurality of observation positions are calculated. and control sound control means for controlling the control sound source driving means so that the sum is minimized.

Further, in the invention described in claim (2), among the components described in claim (1), the acoustic space is a passenger compartment of a vehicle, and the control sound control means is configured to observe two points in a lateral direction of the passenger compartment. a preprocessing calculation unit that calculates a difference between detection signals of the noise sensors corresponding to the positions; and a microprocessor for controlling the control sound source driving means so that the sum of the squares of the respective detection signals of the plurality of noise sensors and the square of the difference signal is minimized based on the signal. .

Furthermore, in the invention described in claim (3), among the components described in claim (1), the acoustic space is a cabin of a vehicle,
The control sound control means calculates the sum of detection signals of the noise sensor corresponding to a plurality of observation positions in the lateral direction of the front seat and each detection signal of the noise sensor corresponding to a plurality of observation positions in the lateral direction of the rear seat. a preprocessing calculation unit that calculates the difference between the sum of
Based on the calculation signal of the preprocessing calculation unit, the detection signal of each noise sensor, and the signal corresponding to the noise generation state of the noise source, the sum of squares of each of the detection signals of the plurality of noise sensors and the and a microprocessor for controlling the control sound source driving means so that the sum of the difference signal and the square of the difference signal is minimized.

(Operation) In the present invention, a plurality of noise sensors detect residual noise at a plurality of predetermined observation positions in an acoustic space, and provide the detected residual noise to the control sound control means. Based on the signal according to the noise generation state of
The control sound source driving means is controlled so that the sum of the squares of the plurality of residual noise detection signals and the square of the differences between the residual noise detection signals corresponding to the plurality of desired observation positions is minimized, and the control sound source is controlled by the control sound source. generate sound. As a result, the canceling sound (-blow sound) and the noise (double-blow sound) interfere, reducing the noise level at the entire observation position, and also reducing the difference in sound pressure level between multiple desired observation positions. do.

In particular, in the invention described in claim (2), since the control sound control means also controls the difference in noise level between two observation positions in the lateral direction of the vehicle interior to a minimum, the observation position may be set to the positions of the occupant's ears, for example. By setting this, the difference in sound pressure level between the positions of both ears can be reduced, and the difference in sound pressure level will not cause discomfort to the occupant.

In particular, in the invention set forth in claim (3), the noise level difference between the observation positions of the front and rear seats of the vehicle interior is also controlled to a minimum by the control sound control means, making it difficult to have a conversation in the front and rear of the vehicle interior. Not at all.

〔Example〕

The present invention will be described in detail below.

(First Example) A first example will be described based on FIGS. 2 and 3. This first embodiment is an application of the present invention to a vehicle.

In FIG. 2, 2 indicates wheels, 4 indicates a vehicle engine as a noise source, 6 indicates a single room as an acoustic space, and Elf and 8r indicate front and rear seats in the vehicle interior 6.

This vehicle is equipped with an active noise control device 9, and the active noise control device 9 includes a crank angle sensor 10.
．． Microphones 14a to 14h.

Controller 16. and loudspeakers 18a-18d
Consisted of. Of these, the engine 4 is equipped with a crank angle sensor 10 that outputs a crank angle signal X in the form of a pulse train every 180'' of crank angle.

8r, a total of eight microphones 14a to 14h, such as noise sensors, are attached at positions corresponding to the positions near both ears of the occupant, two for each seat.

The ends of the microphones 14a to 14h detect noise signals e, to e, which are electrical signals corresponding to the sound pressure at the ear position. Detection signals from the crank angle sensor 10 and the microphones 14a to 14h are individually supplied to a controller 16 installed at a predetermined position on the vehicle body.

Further, the output side of the controller 16 is individually connected to a total of four loudspeakers 18a to 18d as control sound sources, and each of the loudspeakers 18a to 18d is connected to the front and rear seats 8f and 8r on both sides of the vehicle body. It is installed facing the.

As shown in FIG. 3, the controller 16 includes a counter 22 that counts the input crank angle signal X', a digital filter 24 and an adaptive filter 26 that input the count signal X of the counter 22 as a reference signal, and microphones 14a to Subtractors 28a to 28a serve as preprocessing calculation units that perform subtraction on the noise signal e+''−'ea from 14h.
28d, and a difference signal e outputted by the subtractors 28a to 28d.

A/D converters 30a to 30d and 32a to 32h that A/D convert the noise signals e+"-'ea outputted by the microphones 14a to 14h, and the A/D converters 30a to 30d and 32a to 32h,
a microprocessor 34 which inputs the converted signals from the converters 30a to 30d and 32a to 32h and the output signal of the digital filter 24; and D which converts the processed signal of the adaptive filter 26 from D/A to output to the loudspeakers 18a to 18d. /A converters 36a to 36d.

Among these, the digital filter 24 inputs the reference signal X and generates a filtered reference signal rLfi according to the number of combinations of transfer functions between the microphone and the speaker (see sections (4) and (5) 2 described later). , and the adaptive filter 26 is functionally the speaker 18a to 18
It has individual filters according to the number of output channels to d, inputs the reference signal χ, performs adaptive signal processing based on the filter coefficients set at that time, and generates a speaker drive signal 3'm (m-1 , 2, . . . , 4), respectively.

Further, the subtracter 28a manually inputs the noise signal el+82,
The subtracter 28b inputs the noise signal e3゜e4, performs the calculation Fe3e4J and outputs the noise difference signal e1゜, and the subtracter 28c The noise signal esre6 is manually calculated, res ebJ is calculated, and the noise difference signal el is obtained.
f, and the subtracter 28d further outputs noise signals et, e
s is input, Fe7e and J are calculated, and a noise difference signal elt is output.
d, and the noise signals e1 to ea are outputted to the microprocessor 34 via A/D converters 32a to 32h, respectively. The microprocessor 34 generates a noise signal e1
~e8, noise difference signals e, ~e12, and filtered reference signal rL, are input, and the filter coefficients of the adaptive filter 26 are changed using the LMS algorithm.

Here, the control principle according to the present invention will be explained.

Now, the noise signal and noise difference signal output by the i-th microphone 14 and the subtractor 28 are et(n), and 1 when there is no control sound (two-blow sound) from the loud speaker 18.
The noise signal detected by the th microphone 14 and the subtractor 28 is expressed as ep+, (n), and the mth loudspeaker 1
jth (j=o.

1.2. ..., when the term Ic 1) is expressed as a digital filter, the filter coefficient is 001, the crank angle signal is the reference signal x (n), and the reference signal x (n) is input m
i of the adaptive filter driving the loudspeaker 18
th (i=o, 1.2.... Eng.

Let Wmi be the coefficient of EPT(n), et(n)=ept(n)+...(1) holds true. Here, all terms with (n) are sample values at sampling time n, L is the number of microphones 14a to 14h and subtracters 28a to 28d (12 in this embodiment), and M is the number of loudspeakers 14a to 14h and subtractors 28a to 28d (12 in this embodiment). Speakers 18a-18d
(4 in this embodiment), Ic is the number of taps (filter order) of the transfer function C (1) expressed by the FIR digital filter, and Ik is the number of taps of the adaptive filter W.

In the above equation (1), the right side “Σ w,, Hx (n−j
-i)) The term J (=ym) represents the output when the signal χ is input to the adaptive filter coefficient, and is expressed as "Σ CLmj ・
(ΣWIII x (n-j-4)) The term J is such that the signal energy input to the m-th speaker 18 is output as acoustic energy from the m-th speaker 18, and is transferred to the first speaker after passing through the transfer function C0 in the vehicle interior 6. represents the signal when it reaches the microphone 4 and the subtracter 28, and furthermore, ``
Σ Σ C,,,i −(Σ W,, ・x (n
-j-i)) Since the entire right side of J is the sum of the signals arriving at the first microphone 14 and subtractor 28 for all speakers, the two-blow sound reaching the i-th microphone 14 and subtractor 28 is represents the sum of

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

In order to find the filter coefficient W1 that minimizes the evaluation function Je, this embodiment employs the LMS algorithm. That is, the evaluation function Je is converted to each filter coefficient W1. The filter coefficient W1. Update.

Therefore, from equation (2), θW□ θWm = t-busyness, but (1
), so by setting the right side of equation (4) to r(ni), the filter coefficient rewriting equation can be obtained from equation (5) below.

W □ (n + 1) = W □ (n) 10α・Σ e, (n) ・rL, (n-4)
= (5) Here, α is a convergence coefficient, and is involved in the speed at which the filter optimally converges and the stability at that time.

Note that although the convergence coefficient α is treated as a constant in this embodiment, a different convergence coefficient (α1
．． ) can also be used.

In the above configuration, the adaptive filter 26 and the D/A converters 36a to 36d constitute a control i1[1 sound source driving means,
Subtractors 28a to 28d, A/D converter 30a
~30d, 32a ~32h? Bacro processor 3
4. Digital filter 24. The counter 22 and the crank angle sensor 10 constitute a control sound control means.

Next, the operation of the first embodiment will be explained.

When the vehicle runs, rotational vibrations of the engine 4 are transmitted to the passenger compartment 6 through the vehicle body, and remain in the passenger compartment 6 as muffled noise. The engine rotation state at this time is the crank angle sensor 1.
0, and a crank angle signal X' corresponding to the rotational speed of the engine 4 is output to the controller 16. Then, in the controller 16, the number of pulses of the manually inputted crank angle signal X' is counted and converted into a digital quantity, and then supplied as a reference signal X to the digital filter 24 and the adaptive filter 26, respectively.

Of these, the digital filter 24 uses the input reference signal X to generate a filtered reference signal ru# based on equation (4), and outputs this signal r(m to the microprocessor 34.

Further, the microphones 14a to 14h detect sound remaining at their installation positions (observation positions), and similarly output corresponding noise signals e1 to ell to the controller 16. In the controller 16, the human-powered noise signal elxe
, "e+ ex
J+ "es ea J+...+ re,
eel is calculated as an analog quantity and output as noise difference signals e, ~eli+ to A/D converters 30a and 30b.
, . . . , 30d and output to the microprocessor 34.

Along with this, the noise signals e, ~e8 are transmitted to the A/D converter 3.
It is output to the microprocessor 34 via 2a to 32d.

The microprocessor 34 uses each input signal to update the filter coefficients based on equation (5).

In other words, the filter coefficient Wm1(n) at the current sampling time n has an evaluation function, that is, each microphone 1
Noise signal corresponding to the residual sound pressure from 4) and each sea) 8f
, 8r, the noise difference signal e, (n) of the sound pressure difference between the binaural positions.
The filter coefficients in the direction that minimizes the sum of the squares of are applied to each filter, and the filter coefficients W-i (n+1) to be set at the sampling time (n+1) are obtained. Then, the microprocessor 34 calculates the calculated value Wxi(n
+1) is output to the adaptive filter 26. Therefore, the filter coefficient of each filter in the adaptive filter 26 is updated to the newly calculated filter coefficient W m i at sampling time (n+1). In this way, the microprocessor 26 calculates the evaluation function J
The filter coefficient update command is repeated at every predetermined sampling time so as to minimize e.

On the other hand, each filter of the adaptive filter 26 uses the reference signal X and the coefficient W1 according to the filter coefficients set at that time.
．． A vector operation is performed on the output value y to obtain an output value y, and this value is output as a drive signal to the loudspeakers 18a to 18d, respectively, via the D/A converters 136a to 36d.

As a result, each speaker 18a to 18d receives the human power signal y
A control sound (two-blow sound) corresponding to No. 5 is generated.

In other words, a control sound having a phase that offsets the residual noise at eight observation points (microphone installation positions) is generated from each of the speakers 18a to 18d, and this control sound corresponds to the transfer function C0 estimated in advance. The signal propagates through the vehicle interior space based on the directivity of the speaker. For this reason, especially at observation points and their surroundings using the microphones 14a to 14h,
The muffled sound (noise) in the passenger compartment 6 due to engine vibration and the control sound interfere with each other, and the engine noise remaining in the passenger compartment 6 is significantly reduced. At this time, the adjacent microphones 14a, 1
4b (~14g, 14h) is also minimized, so even if the overall noise in the passenger compartment 6 is small as in the past, the significant difference in sound pressure between both ears will cause the occupants to feel uncomfortable. Not at all.

Furthermore, in the first embodiment, the evaluation function Je that minimizes the sound pressure difference between the two ear positions is set by calculating the difference between both noise signals and then calculating the sum of squares. For example, compared to calculating the square of each noise signal 01 to e8 first, then calculating the difference between the signals and calculating the sum, it is better not only when the phases of both noise signals match, but also when the phases are different. (For example, when both signal levels are the same and have opposite phases), it is possible to obtain a difference signal that takes into account the phase difference.This has the advantage that the sound pressure difference can be minimized while taking the phase into account, and the microprocessor This method has the advantage that the computational burden on 34 is small and the computational speed can be increased. Furthermore, since the noise signals e1 to e8 are subtracted by analog calculation before being input to the microprocessor 34, the calculation load on the microprocessor 34 can be further reduced, and the microprocessor 34 can concentrate on filter coefficient update calculations. .

In the first embodiment, the evaluation function Je was selected to minimize the sound pressure difference for each of the seats 8f and 8r, but the present invention is not limited to this, and for example,
or only to the driver's seat, in which case, in the evaluation function Je, 'el ez J,'
It is sufficient to include only e3 ea J or "ee2".

(Second Embodiment) Next, a second embodiment will be described based on FIGS. 2 and 4. Here, the same reference numerals are used for the same components as in the first embodiment, and the description thereof will be omitted or simplified.

In the second embodiment, in addition to reducing the noise of the entire vehicle interior, noise control is performed in consideration of the sound pressure difference between the front and rear seats (8f and Br). Therefore, the overall configuration of the active noise control device 9 mounted on the vehicle is the same as shown in FIG.
A controller 16 therein is arranged as shown in FIG.

In FIG. 4, on the microphone input side of the microprocessor 34, instead of each component of the first embodiment, there is an A/D converter 40a for A/D converting the noise signals e, -e8 from the microphones 14a to 14h. ~40h, front seat 8f, microphone 14a-1 installed on the Br side
an adder 42 that mutually adds the noise signals el-ea from the microphones 4d, an adder 44 that mutually adds the noise signals e and -e8 from the microphones 14e to 14h installed on the rear seat 8r side, and The output signal of the adder 44 on the rear side is subtracted from the output signal of the adder 42 to obtain the noise difference signal e.
, and the calculation result of this subtracter 46 as A
/D conversion and supply to microprocessor 34
A converter 48 is added.

In addition, in the second embodiment, the adder 42.44° and the subtracter 4
6. A/D converters 40a to 40h, 48 microprocessor 34. The digital filter 24, the counter 22, and the crank angle sensor 10 constitute the control sound control means, of which the adders 42, 44 and the subtracter 46 correspond to the preprocessing calculation section.

The other configurations are the same as the first embodiment. Further, the control method is also the same as that of the first embodiment, but the evaluation function Je to be minimized using the LMS algorithm is determined as follows.

That is, each noise signal e, (1=1.2...,8)
and the square value of the value obtained by subtracting the rear sum from the front sum of the noise signal e, and the added value is made to be the minimum.

Of these, the adders 42 and 44 and the subtracter 46 of the controller 16 are configured to perform the calculation of the second term on the right side of equation (2)' before inputting to the microprocessor 34.

The second embodiment is configured as described above, and its evaluation function J
It is controlled using the LMS algorithm so that e is minimized. Therefore, as in the first embodiment, the muffled sound transmitted from the engine 4 is reliably reduced in a state where the sound pressure difference between the front and rear seats 8f and Br is minimized, and especially , a situation in which conversation becomes difficult before and after the vehicle compartment 6 is reliably prevented.

In addition, the above-mentioned 1. In the second embodiment, a noise control device is described in which the microphone position for controlling the sound pressure difference to the minimum is fixed in advance, but instead of fixing the microphone position for controlling the sound pressure difference to a minimum, The microphone position for sound pressure difference control is configured to be selectable, and the passenger operates this selection switch to arbitrarily select the microphone position for sound pressure difference control, thereby improving the noise control function.

Furthermore, in each of the embodiments described above, addition and subtraction by preprocessing operations performed before the microprocessor can of course be performed within the microprocessor.

Further, in each of the above embodiments, a case has been described in which a plurality of loud speakers are provided as control sound sources, but the present invention is not necessarily limited to this, and a configuration with one loud speaker may also be adopted.

Furthermore, the active noise control device of the present invention is not limited to a device applied to a passenger compartment as in the above-described embodiment, but may be a device applied to an aircraft cabin, or a device applied to a plurality of air conditioners. It is also possible to use a device that uses trr4 to reduce indoor noise caused by the rotation of the outdoor unit. On the other hand, in the above-mentioned embodiments, the case where the noise source is located outside a kind of closed space called the passenger compartment has been explained, but the present invention is applicable to the case where the noise source is installed inside such a closed space. It can also be applied to

Furthermore, as means for detecting noise generation conditions applied to the present invention, in addition to crank angle signals related to muffled noise and exhaust noise caused by engine vibration, pickup signals related to road noise caused by suspension vibration, and pickup signals related to road noise caused by suspension vibration, It may also be a pickup signal related to wind noise accompanying vibration.

Furthermore, the reference input of the adaptive filter included in the control sound source driving means is not limited to a signal based on a crank angle signal as described in the above-mentioned embodiments, but may also be a detection signal of a microphone, for example. , a reference signal generator that generates a periodic function.

Furthermore, the filter coefficient updating algorithm according to the control sound control means of the present invention may be, for example, an LMS algorithm in the frequency domain, in addition to the time domain LMS algorithm as described in the above-described embodiments.

(Effects of the Invention) As explained above, according to the present invention, the sum of the squares of residual noise detection signals at a plurality of observation positions in an acoustic space and the residual noise detection signals corresponding to a plurality of desired observation positions Since the control sound is controlled so that the sum of the square of the difference between The sound pressure level of the residual noise becomes almost equal, the amount of noise in the acoustic space is minimized and the noise distribution is made uniform, and a high-quality noise reduction state is obtained.

In particular, in the invention described in claim (2), by setting two observation positions in the lateral direction of the vehicle interior, for example, at the positions of both ears of the occupant, the sound pressure level difference between the positions of both ears can also be adjusted. This has the effect of reliably eliminating discomfort caused by the sound pressure level difference between the two ears even if the amount of noise inside the vehicle is reduced.

In particular, according to the invention set forth in claim (3), the difference in sound pressure level between the front and rear seats of the passenger compartment is also minimized, so that conversation between the front and rear seats is not hindered by the difference in sound pressure level. , it has the effect of allowing you to have a natural conversation.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, and FIG. A schematic configuration diagram showing the second embodiment; FIG. 3 is a partially omitted block diagram of the controller in the first embodiment;
FIG. 4 is a partially omitted block diagram of the controller in the second embodiment. 9: Active noise control device, lO: Crank angle sensor, 1
4a-14d: Microphone, 16: Controller, 1
8a-18d Niloud speaker, 28a-28d,
46: Subtractor, 34: Microprocessor, 42.44
: Adder.

Claims (3)

[Claims] (1) A plurality of noise sensors that individually detect residual noise at a plurality of observation positions in an acoustic space where noise is transmitted from a noise source, a control sound source that can output control sound to the acoustic space, and a control sound source that Based on the control sound source driving means to be driven, the detection signals of the plurality of noise sensors, and the signal according to the noise generation state of the noise source, the sum of the squares of the detection signals of the plurality of noise sensors and the desired plurality of An active noise control device comprising control sound control means for controlling the control sound source driving means so that the sum of the square of the difference between the detection signals of the noise sensors corresponding to the observation position is minimized. (2) The acoustic space is a passenger compartment of a vehicle, and the control sound control means is a preprocessing calculation unit that calculates a difference between detection signals of the noise sensor corresponding to two observation positions in a lateral direction of the passenger compartment. Based on the calculation signal of the preprocessing calculation unit, the detection signal of each of the noise sensors, and the signal according to the noise generation state of the noise source, the sum of squares of the detection signals of the plurality of noise sensors and the difference are calculated. 2. The active noise control device according to claim 1, further comprising a microprocessor that controls the control sound source driving means so that the sum of the signal and the square of the signal is minimized. (3) The acoustic space is a passenger compartment of a vehicle, and the control sound control means combines the sum of detection signals of the noise sensors corresponding to observation positions at multiple points in the lateral direction of the front seat and the lateral direction of the rear seat. a preprocessing calculation unit that calculates a difference between the sum of detection signals of the noise sensors corresponding to observation positions of a plurality of points; a calculation signal of the preprocessing calculation unit; a detection signal of each of the noise sensors; and the noise source. a microprocessor for controlling the control sound source driving means so that the sum of the squares of the respective detection signals of the plurality of noise sensors and the square of the difference signal is minimized based on a signal corresponding to a noise generation state of the noise sensor; The active noise control device according to claim 1, characterized in that it has the following.