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DESCRIPTION JPH03203490

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DESCRIPTION JPH03203490
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
active noise control apparatus for reducing noise transmitted to an acoustic space such as the
interior of a vehicle by interference with a control sound, and in particular to a plurality of
observation positions in the acoustic space. The present invention relates to an active noise
control device which also takes into account the control of the noise level difference of 2.
Description of the Related Art Heretofore, as this type of active noise control device, for example,
a device described in GB-A-2149614 is known. This conventional device is applied to a cabin of
an aircraft or a similar closed space, and includes a plurality of loudspeakers (secondary sound
sources) and microphones installed in the closed space, an engine located outside the closed
space, etc. The frequency r of a single noise source (-next sound source). And a signal processor
for controlling driving of the plurality of loudspeakers based on detection signals of the plurality
of microphones and detection signals of the frequency detection unit. The signal processor sets
the detection signals P7 (n = 1.2... 1m) of a plurality of microphones, that is, the sum of squares P
of sound pressure, as an evaluation function, and louds to minimize this evaluation function P8. It
controls the phase etc. of the control sound from the speaker. As a result, the secondary sound
generated from the loudspeaker and the primary sound transmitted from the noise source
interfere with each other to reduce residual noise at the observation position in the closed space.
[Problem to be Solved by the Invention] However, since the above-mentioned conventional
apparatus is a control method of simply minimizing the sum of noise levels at each observation
position, even if the sum is minimum, for example, both ears of the occupant When there is a
significant difference in sound pressure level between the positions, the occupants feel
discomfort and can not necessarily control to the sound pressure level difference at the desired
multiple observation positions. It was in the condition that high quality noise reduction could not
be achieved. The present invention has been made focusing on the situation facing such
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conventional devices, and the problem to be solved is to minimize noise throughout each
observation position in the acoustic space, and The sound pressure level difference between the
observation points is also minimized to balance the observation points so as to obtain a highquality noise-reduced acoustic space. [Means for Solving the Problems] In order to solve the
above-mentioned problems, in the invention described in claim (1), noise is generated from a
noise source as shown in FIG. 1 (in the figure, a plurality of control sound sources are shown). A
plurality of noise sensors individually detecting residual noise at a plurality of observation
positions in the acoustic space to which the signal is transmitted, a control sound source capable
of outputting a control sound to the sound space, and a control sound source drive means for
driving the control sound source Between the noise sensors corresponding to the sum of the
squares of the detection signals of the plurality of noise sensors and the plurality of observation
positions based on the detection signals of the plurality of noise sensors and the signal according
to the noise generation state of the noise source And a control sound control means for
controlling the control sound source drive means so as to minimize the sum of the difference
between the detection signals and the square of the difference.
Further, in the invention described in claim (2), among the constituent elements described in
claim (1), the acoustic space is a compartment of a vehicle, and the control sound control means
observes two points in the lateral direction of the compartment. A preprocessing operation unit
that calculates the difference between detection signals of the noise sensor corresponding to the
position, the operation signal of the preprocessing operation unit, a detection signal of each noise
sensor, and a noise generation state of the noise source The microprocessor is configured to
control the control sound source driving means so that the sum of the sum of squares of each of
the detection signals of the plurality of noise sensors and the square of the difference signal is
minimized based on the signals. . Further, in the invention described in claim (3), among the
constituent elements described in claim (1), the acoustic space is a compartment of a vehicle, and
the control sound control means is provided at plural points in the lateral direction of the front
seat. A pre-processing operation unit that calculates a difference between a sum of detection
signals of the noise sensor corresponding to an observation position and a sum of detection
signals of the noise sensor corresponding to observation positions of a plurality of lateral points
in the rear sheet; The sum of squares of the detection signals of the plurality of noise sensors and
the difference based on the calculation signals of the pre-processing calculation unit, the
detection signals of the respective noises, and the signals according to the noise generation state
of the noise source A microprocessor is provided to control the control sound source driving
means so as to minimize the sum of the square of the signal. (Operation) In the present invention,
a plurality of noise sensors detect residual noise at predetermined plural observation positions in
the acoustic space, and provide the control noise control means. In the control sound control
means, based on the plurality of residual noise detection signals and the signal corresponding to
the noise generation state of the noise source, residual noise corresponding to the sum of
squares of each of the plurality of residual noise detection signals and a plurality of desired
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observation positions The control sound source driving means is controlled so that the sum of
the difference between the detection signals and the square is minimized, and a control sound is
generated from the control sound source. As a result, the cancellation sound (-blow sound) and
the noise (two-blow sound) interfere with each other to reduce the noise level at the entire
observation position and to reduce the sound pressure level difference between a plurality of
desired observation positions. Do. In particular, in the invention as set forth in claim (2), the noise
level difference between the two observation positions in the lateral direction of the vehicle
compartment is also controlled to a minimum by the control sound control means. By setting the
sound pressure level difference between the binaural positions, it is possible to reduce the sound
pressure level difference, and the sound pressure level difference does not make the occupant
uncomfortable. Particularly, in the invention according to claim (3), since the noise level
difference between the respective observation positions of the front and rear seats of the vehicle
compartment is also controlled to a minimum by the control sound control means, conversation
becomes difficult before and after the vehicle interior I have nothing to do.
The present invention will be described in detail below. (First Embodiment) A first embodiment
will be described based on FIGS. 2 to 3. FIG. The first embodiment is an application of the present
invention to a vehicle. In FIG. 2, 2 indicates a wheel, 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 passenger compartment 6, respectively. An active noise control device 9 is mounted
on the vehicle, and the active noise control device 9 includes a crank angle sensor 10. ?????
????????? ????????? And loudspeakers 18a to 18d. Among them, attached to
the engine 4 is a crank angle sensor 10 which outputs a crank angle signal X consisting of a
pulse train for each crank angle 180 ? ? ?. In addition, the seat 8f of the cabin 6. At 8r,
microphones 14a to 14h are attached at positions corresponding to positions near the both ears
of the occupant, for a total of eight noise sensors, two for each sheet. Each of the microphones
14a to 14h detects noise signals e to e consisting of electrical signals according to the sound
pressure at the ear position. The detection signals of the crank angle sensor 10 and the
microphones 14a to 14h are individually supplied to the controller 16 installed at a
predetermined position of the vehicle body. In addition, the output side of the controller 16 is
individually connected to the loudspeakers 18a to 18d as a total of four control sound sources. It
is installed in the state of facing. As shown in FIG. 3, the controller 16 has a counter 22 for
counting the input crank angle signal X ', a digital filter 24 and an adaptive filter 26 for inputting
the count signal X of the counter 22 as a reference signal, and the microphones 14a to
Subtractors 28a to 28d as pre-processing operation units for performing subtraction on the noise
signal e + "-'ea from 14h and a difference signal e output from the subtractors 28a to 28d. A / D
converters 30a to 30d and 32a to 32h for A / D converting noise signals e + ''-'ea outputted by
the microphones 14a to 14h and the microphones 14a to 14h, and the A / D converters 30a to
30d and 32a 32 h and the microprocessor 34 for inputting the output signal of the digital filter
24; and D / A converters 36 a to 36 d for D / A converting the processed signal of the adaptive
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filter 26 and outputting the same to the loudspeakers 18 a to 18 d. Is equipped.
Among them, the digital filter 24 inputs the reference signal X, and the reference signal rLfi
filtered according to the number of combinations of transfer functions between the microphone
and the speaker (see (4) and (5)). The adaptive filter 26 functionally includes filters individually
corresponding to the number of output channels to the speakers 18a to 18d, receives the
reference signal ?, and the filter coefficients set at that time Adaptive signal processing is
performed based on the above to output speaker drive signals 3 'm (m-1, 2,..., 4). Further, the
subtractor 28a manually calculates the noise signal el + 82, and calculates "et ezJ and outputs a
noise difference signal e. The subtractor 28b receives the noise signal e3.degree.e4 and
calculates Fe3 e4J. The noise difference signal e1 ░ is output, the subtractor 28c manually
calculates the noise signal esre6, the calculation of res ebJ is performed, and the noise difference
signal elf is output, and the subtractor 28d receives the noise signals et and es, and Fe7e , J to
output the noise difference signal elt, and the noise difference signals 09 to elz corresponding to
the subtraction result are respectively transmitted through the A / D converters 308 to 30 d and
the noise signals e1 to ea. Are output to the microprocessor 34 via the A / D converters 32a to
32h. The microprocessor 34 receives the noise signals e1 to e8, the noise difference signals e to
e12, and the filtered reference signal rL, and changes the filter coefficients of the adaptive filter
26 using the LMS algorithm. ing. Here, the control principle according to the present invention
will be described. Now, the noise signal and noise difference signal output from the i-th
microphone 14 and the subtractor 28 are et (n), and the first microphone 14 and subtraction
when there is no control sound (double blowing) from the loudspeaker 18 Ep +, (n), the j-th (j) of
the transfer function (FIR (finite impulse response) function) between the m-th loudspeaker 18
and the c-th microphone 14 and the subtractor 28 = O. ???? ... 001: Filter coefficient when
the term of Ic 1) is expressed by a digital filter, the crank angle signal is the reference signal x (n),
and the reference signal x (n) is input to drive the m-th loudspeaker 18 Adaptive filter i-th (i = o,
1.2. ... work. Assuming that the coefficient of work) is Wmi, et (n) = ept (n) + ... (1) holds.
Here, the terms with (n) are all sample values at sampling time n, and L is the number of
microphones 14a to 14h and subtractors 28a to 28d (12 in this embodiment), and M is a
loudness. The number of speakers 18a-18d (four in this embodiment), Ic is the transfer function
C (the number of taps of 1 (filter order) represented by the FIR digital filter, and Ik is the number
of taps of the adaptive filter W. In the above equation (1), the term ?? w, H x (n j i)) J (= ym) on
the right side represents the output when the signal ? is input to the adaptive filter coefficient,?
?CL m j ии The signal energy input to the m-th speaker 18 is output as acoustic energy from the
speaker 18 through the (? WIII и x (n?j?4) J, and the first one passes through the transfer
function C0 in the passenger compartment 6? ? i C,, i ? ((W,... X (n-j-i)) J and the entire right
side of the signal is 1 Since the arrival signals to the th microphone 14 and the subtractor 28 are
summed for all the speakers, the sum of the two blowing noises reaching the ith microphone 14
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and the subtractor 28 is represented. Then, let an evaluation function (variable to be minimized)
Je be. Then, in order to obtain the filter coefficient W1 that minimizes the evaluation function Je,
the LMS algorithm is adopted in this embodiment. That is, the evaluation function Je is set to
each filter coefficient W1. The filter coefficient W1. Update Then, ?W ? ?Wm = t? busy from
Eq. (2), but from Eq. (1), if the right side of Eq. (4) is r (ni), the filter coefficient The rewriting
equation is obtained by the following equation (5). W ? (n + 1) = W ? (n) О ? и ?e, (n) и rL,
(n?4) = (5) where ? is a convergence coefficient, and the speed at which the filter converges
optimally or , Involved in the stability at that time. Although the convergence coefficient ? is
treated as one constant in this embodiment, different convergence coefficients (?1. ?????
?????? In the above configuration, the adaptive filter 26 and the D / A converters 36a to
36d constitute a control unit i1 [1 sound source driving means, subtractors 28a to 28d, A / D
converters 30a to 30d, 32a to 32h? ??????????? ???????????? The
counter 22 and the crank angle sensor 10 constitute control sound control means.
Next, the operation of the first embodiment will be described. When the vehicle travels, the
rotational vibration of the engine 4 is transmitted to the passenger compartment 6 via the
vehicle body and remains in the passenger compartment 6 as a roaring noise. The engine
rotation state at this time is detected by the crank angle sensor 10, and a crank angle signal X ?
corresponding to the rotational speed of the engine 4 is output to the controller 16. Then, the
controller 16 counts the number of pulses of the crank angle signal X 'manually input and
converts it into a digital quantity, and then supplies it as the reference signal X to the digital filter
24 and the adaptive filter 26, respectively. Among them, the digital filter 24 generates the
reference signal ru # filtered based on the equation (4) using the input reference signal X, and
outputs this signal r (m to the microprocessor 34. Also, the microphones 14a to 14h detect the
sound remaining at the installation position (observation position), and similarly output noise
signals e1 to ell to the controller 16 according to the detected sound. In the controller 16, among
the noise signals elxe manually input, ?e + ex J +? es ea J +... + Re, eel are respectively
calculated as analog quantities by the subtractors 28 a to 28 d and the noise difference signals e
to eli + As each of the A / D converters 30a, 30b,..., 30d, the data is individually converted and
output to the microprocessor 34. At the same time, noise signals e,..., E8 are output to the
microprocessor 34 via the A / D converters 32a-32d. The microprocessor 34 performs an update
operation of the filter coefficient based on the equation (5) using each input signal. In other
words, the noise of the sound pressure difference between the binaural positions of the noise
coefficients corresponding to the residual sound pressure from each microphone 14 and each
sheet) 8f and 8r with the filter coefficient Wm1 (n) at the current sampling time n. A filter
coefficient in the direction in which the sum of squares of the difference signals e and (n) is
minimized is applied to each filter to obtain a filter coefficient Wi (n + 1) to be set at the sampling
time (n + 1). Then, the microprocessor 34 outputs a control signal corresponding to the
calculated value Wxi (n + 1) to the adaptive filter 26. For this reason, the filter coefficients of
each filter in the adaptive filter 26 are updated to newly calculated filter coefficients Wmi at the
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sampling time (n + 1). As described above, the microprocessor 26 repeats the filter coefficient
update command every predetermined sampling time so as to minimize the evaluation function
Je.
On the other hand, each filter of the adaptive filter 26 receives the reference signal X and the
coefficients W1. The following vector operation is performed to obtain an output value y, which
is output as driving signals to the loudspeakers 18a to 18d through D / A conversions 136a to
36d. As a result, each of the speakers 18a to 18d generates a control sound (second blowing
sound) according to the human power signal y5. That is, a control sound having a phase that
cancels out 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 which is estimated in advance. The passenger compartment space is
propagated based on the directivity of the speaker. For this reason, especially at the observation
points by the microphones 14a to 14h and in the vicinity thereof, the booming noise (noise) in
the compartment 6 and the control sound interfere with the engine vibration, and the engine
noise remaining in the compartment 6 is significantly reduced. . At this time, since the sound
pressure difference between the adjacent microphones 14a and 14b (~ 14g and 14h) is also
minimized, the sound pressure difference between both the ears is large even if the noise of the
entire vehicle compartment 6 is small as in the prior art. There is no need for the crew to feel
uncomfortable. Further, in the first embodiment, as the method of setting the evaluation function
Je for minimizing the sound pressure difference between binaural positions, the difference
between both noise signals is calculated and then the sum of squares is calculated. For example,
in the case where the phases of the two noise signals coincide with each other, the phases are
different, for example, as compared with the case where the difference between the signals is
obtained and the sum is calculated after the squares of the noise signals 01 to e8 are calculated
first. Even when the signal levels are the same and opposite in phase, for example, a difference
signal taking into consideration the phase difference can be obtained, thereby obtaining an
advantage that the sound pressure difference can be minimized with the phase taken into
consideration. There is an advantage that the operation load at 34 is small and the operation
speed can be increased. Furthermore, since the subtraction of the noise signals e1 to e8 is
performed by analog calculation before the input of the microprocessor 34, the calculation load
of the microprocessor 34 can be further reduced, and the microprocessor 34 can concentrate on
the filter coefficient update calculation. . In the first embodiment, the evaluation function Je is
selected to minimize the sound pressure difference for each of the sheets 8f and 8r, but the
present invention is not limited thereto. For example, only the front sheet 8f or the driver's seat
In this case, only 'el ez J,' e3 ea J or 'ee2' may be included in the evaluation function Je.
Second Embodiment Next, a second embodiment will be described based on FIGS. 2 and 4. FIG.
Here, the same reference numerals are used for the same components as in the first embodiment
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to omit or simplify the explanation. In the second embodiment, noise control is performed in
consideration of the sound pressure difference between the front and rear sheets 8f and Br in
addition to the noise reduction in the entire cabin. For this reason, the overall configuration of
the active noise control device 9 mounted on the vehicle is the same as that of FIG. 2, and the
controller 16 therein is as shown in FIG. In FIG. 4, an A / D converter 40a for A / D converting
noise signals e,..., E8 from the microphones 14a to 14h on the microphone input side of the
microprocessor 34 instead of the components of the first embodiment. Through 40h and an
adder 42 for mutually adding the noise signals el-ea from the microphones 14a-14d which are
disposed on the front sheet 8f and the Br side, and from the microphones 14e to 14h which are
disposed on the rear sheet 8r side Noise signal e,... E8 of each other, and a subtractor 46 which
subtracts the output signal of the rear adder 44 from the output signal of the front adder 42 to
obtain a noise difference signal e. The A / D converter 48 is added to A / D convert the operation
result of the subtractor 46 and supply it to the microprocessor 34. In the second embodiment,
the adder 42.44 ░ subtractor 46. A / D converters 40a-40h, 48 microprocessors 34. The digital
filter 24, the counter 22 and the crank angle sensor 10 constitute control sound control means,
and of these, the adders 42 and 44 and the subtractor 46 correspond to the pre-processing
operation unit. The other configuration is the same as that of the first embodiment. The control
method is also the same as that of the first embodiment, but the method of estimation function Je
which is minimized using the LMS algorithm is as follows. That is, each noise signal e, (1 = 1.2.
The sum of squares of 8) and the square value of the noise signal e minus the sum on the rear
side from the sum on the front side are added, and the sum is made to be minimum . Among
them, the adders 42 and 44 and the subtractor 46 of the controller 16 perform the operation of
the second term of the right side of the equation (2) 'before the input of the microprocessor 34.
The second embodiment is configured as described above, and is controlled using the LMS
algorithm so that the evaluation function Je is minimized. For this reason, as with the first
embodiment, as the first embodiment, with the sound pressure difference between the front and
rear sheets 8f and Br being minimized, the loom noise transmitted from the engine 4 is reliably
reduced. The situation that the conversation becomes difficult before and after the passenger
compartment 6 is surely prevented.
In addition, the first one described above. In both of the second embodiment, the noise control
device in which the microphone position for controlling the sound pressure difference to a
minimum is fixed in advance is described, but the microphone position of the sound pressure
difference control is not fixed and the switch signal from the selection switch is used. The
microphone position of the sound pressure difference control can be selected, and by operating
the selection switch, the microphone position of the sound pressure difference control can be
arbitrarily selected to enhance the noise control function. Further, it is of course possible to
perform addition / subtraction based on the pre-processing operation performed in the previous
stage of the microprocessor in each of the above-mentioned embodiments inside the
microprocessor. Furthermore, although the case where a plurality of loudspeakers as control
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sound sources are provided has been described in each of the embodiments, the present
invention is not necessarily limited to this, and a configuration of one loudspeaker can also be
adopted. Furthermore, the active noise control device of the present invention is not limited to
the device applied to the passenger compartment as in the above-described embodiment, but
may be a device applied to the cabin of an aircraft, for example. It is also possible to use a trr4
device to reduce indoor noise caused by the rotation of the outdoor unit. On the other hand,
although the case where the noise source is outside the kind of closed space of the cabin is
described in the above-mentioned embodiment, the present invention is the case where the noise
source is installed inside such a closed space It can be applied to Furthermore, as a means for
detecting the noise generation state applied to the present invention, in addition to a crank angle
signal related to muddy noise and exhaust noise caused by engine vibration, a pickup signal
related to road noise caused by suspension vibration, door mirror It may be a pickup signal or
the like regarding wind noise associated with vibration. Furthermore, the reference input of the
adaptive filter included in the control sound source driving means is not limited to the signal
based on the crank angle signal as described in the above-described embodiment, and may be,
for example, a detection signal of a microphone The reference signal generator may generate a
periodic function. Furthermore, the algorithm of the filter coefficient update according to the
control sound control means of the present invention may be, for example, the LMS algorithm in
the frequency domain in addition to the LMS algorithm in the time domain as described in the
embodiment described above. (Effects of the Invention) As described above, according to the
present invention, detection signals of residual noise at a plurality of observation positions in
acoustic space are sums of squares of the respective noises and detection signals of residual
noise corresponding to a plurality of desired observation positions. Since the control sound is
controlled so that the sum of the difference and the square of the difference is minimized, not
only the sum of the residual noise amount at a plurality of observation positions is simply
minimized as in the prior art, but also at desired The sound pressure level of the residual noise is
also approximately equal, the noise amount in the acoustic space is minimized, and the noise
distribution is equalized, and a high quality noise reduction state is obtained.
Particularly, in the invention according to claim (2), the sound pressure level difference between
both binaural positions is also adjusted by setting the observation positions at two points in the
lateral direction of the cabin to, for example, the binaural positions of the occupant. Therefore,
even if the noise level in the vehicle compartment is reduced, the discomfort caused by the sound
pressure level difference between both ears can be reliably eliminated. In particular, in the
invention recited in claim (3), the sound pressure level difference between the front and back of
the cabin is also minimized, so that the conversation between the front and rear seats is not
disturbed by the sound pressure level difference. Has the effect of being able to have a natural
conversation.
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[0002]
Brief description of the drawings
[0003]
FIG. 1 is a diagram corresponding to the claims of the present invention, and FIG.
FIG. 3 is a schematic block diagram showing the second embodiment, FIG. 3 is a block diagram
partially omitting the controller in the first embodiment, and FIG. 4 is a block diagram partially
omitted the controller in the second embodiment. 9: Active noise control device, lO: crank angle
sensor, 14a-14d: microphone, 16: controller, 18a-18d two loud speakers, 28a-28d, 46:
subtractor, 34: microprocessor, 42.44: addition vessel.
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