JPH03203493A - Active type noise controller - Google Patents

Abstract

PURPOSE:To always minimize noise at obserber's ear positions by detecting the variation of the ear positions of the observer located in the vicinity of a sound receiving point and correcting physical constant of an acoustic system in accordance with the detection value so that the noise level of the sound receiving point to be controlled is always held at the minimum value. CONSTITUTION:A reference signal corresponding to the noise generating state of an engine 4 to be a noise source is detected by an engine rotation frequency sensor 10 to be a reference signal detecting means, a noise level on a prescribed sound receiving point in the acoustic space is detected by microphones 14a, 14b to be noise level detecting means and a controller 16 drives loud speakers 18a, 18b to be control sound sources based on both detection values so that the detection values of the noise detecting means are minimized. Thereby, the noise transmitted to the acoustic space and control sounds radiated from the control sound sources are offset to each other, reducing the noise. In parallel with the operation, the variation of the ear positions of the observer existing in the vicinity of the sound receiving point is detected by heat position detectors 12a, 12b to be ear position detecting mean, and even if the detection value is changed, the controller 16 properly corrects the physical properties (a transmission function and an acoustic output axis) of an acoustic system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active noise control device that reduces noise transmitted to the interior of a vehicle etc. by interference with control sound emitted from a control sound source. In particular, the present invention relates to an active noise control device that includes means for correcting an acoustic system depending on the ear position of an observer such as a passenger.

[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 a plurality of microphones that are fixedly installed in the closed space to detect the sound pressure at the installation position, and a double-blow sound in the closed space. A plurality of radiating loudspeakers (secondary sound sources), frequency detection means for detecting frequencies r0 to f7 of a single noise source (-blowing sound source) such as an engine located outside the closed space, and a plurality of microphones. and a signal processor that controls driving of the plurality of loudspeakers based on the detection signal and the detection signal of the frequency detection means. The signal processor then processes the detection signals P of the plurality of microphones, (n=1.2
．．・", m), that is, the sum of squares of sound pressure P: P-Σ pH2 is used as an evaluation function, and adaptive control is performed to minimize this evaluation function P. As a result, the noise emitted from the loudspeaker is The blowing sound and the primary sound transmitted from the noise source interfere to reduce residual noise at each observation location.

[Problem to be solved by the invention]

However, the conventional device described above has a fixed observation position (
Taking a vehicle equipped with such a conventional device as an example, the sound pressure at the position of the occupant's ears when sitting on the seat is reduced due to height differences between the occupants. ) may change due to changes in the sound pressure gradient or sound intensity in the vehicle interior (for example, in the Journal of Automotive Technology, No. 40).
．． 16 of 1989, published by the Society of Automotive Engineers of Japan)
(See Figure 13 on page 3), the perceived noise becomes extremely loud, and even if the noise is effectively reduced for a specific occupant, the perceived noise will vary as the occupant changes. There was a problem. In particular, when the noise frequency reaches a high frequency range of 300 Hz or higher, the wavelength becomes shorter and complex resonance modes are formed in the vehicle interior, making the sound field more complex. Even though the sound field is comfortable for some passengers,
The noise would be extremely loud to other occupants, and the above-mentioned problems would become apparent, so conventional devices were not necessarily able to reliably reduce the noise at the occupant's ear level in a high frequency range.

The present invention was made by focusing on the problems of the conventional device, and the problem to be solved is to ensure that the noise that can be heard is always minimal and constant even if the observer such as the passenger changes. At the same time, the objective is to ensure that such fluctuations hardly appear even in the high frequency range where the sound field becomes complex.

(Means for Solving the Problem) In order to solve the above problem, the invention according to claim (1) is capable of generating control sound in an acoustic space where noise is transmitted from a noise source, as shown in FIG. a control sound source, a reference signal detection means for detecting a reference signal according to a noise generation state of the noise source, a noise detection means for detecting a noise level at a predetermined sound receiving point in the acoustic space, and the reference signal detection means. and adaptive control means for driving the control sound source so that the detected value of the noise detecting means is minimized based on the detected value of the noise detecting means, the active noise control device comprising: a sound source located near the sound receiving point; Ear position detection means for detecting changes in the observer's ear position, and according to the detected value of this ear position detection means,
A correction means is provided for correcting the physical properties of the acoustic system so that the noise level at the sound receiving point controlled by the adaptive control means always maintains a minimum value. .

In the invention as set forth in claim (2), the correction means as set forth in claim (1) is a means for correcting the transfer function of the acoustic system from the controlled sound source to the sound receiving point.

Furthermore, in the invention set forth in claim (3), the correction means set forth in claim (1) is a means for correcting the direction of the acoustic output axis from the controlled sound source toward the sound receiving point or the focal length of the acoustic lens.

Furthermore, in the invention described in claim (4), claim (1) (
The noise control JIU means described in 2) or (3) is used as a means for detecting sound intensity.

[Effect]

In the present invention, the reference signal detecting means detects a reference signal corresponding to the noise generation state of the noise source, the noise level at a predetermined sound receiving point in the acoustic space is detected by the noise detecting means, and the adaptive control means detects the reference signal. Based on the detected value of the noise detecting means and the noise detecting means, the control sound source is driven so that the detected value of the noise detecting means is minimized. As a result, the noise transmitted to the acoustic space and the control sound emitted from the control sound source cancel each other out, thereby reducing the noise. In parallel with this, a change in the ear position of the observer near the sound receiving point is detected by the ear position detection means. Therefore, the correction means appropriately corrects the physical properties of the acoustic system (transfer function and acoustic output axis) even when the detected value of the ear position detection means changes, so that the noise level at the reception point is always at the minimum value. maintain.

In particular, in the invention described in claim (4), since the noise detection means detects the acoustic intensity, the influence of resonance is avoided in the sound field in the high frequency range where traveling wave components are dominant;
Noise can be reduced by reliably eliminating traveling wave components.

〔Example〕

The present invention will be described in detail below.

(First Example) A first example will be described based on FIGS. 2 to 4. This embodiment is applied to the cabin of a vehicle as an acoustic space.

In Fig. 2, 4 represents a vehicle engine as a noise source;
Reference numeral 6 indicates a vehicle interior as an acoustic space, and reference numeral 8 indicates an active noise control device mounted on the vehicle.

The active noise control device 8 includes an engine rotation speed sensor 10 as a reference signal detection means. Seat position detectors 12a and 12b as ear position detection means, microphones 14a and 14b as noise detection means installed in the vehicle interior 6, and a controller 16 installed at a predetermined position in the vehicle. and compartment 6
a loudspeaker 18a as a control sound source installed in
18b.

Of these, the engine rotation speed sensor 10 is attached to the engine 4, detects an engine rotation speed signal X of a pulse train according to the engine rotation, and supplies this to the controller 16. Further, the seat position detectors 12a and 12b are incorporated in the seat sliders 21a and 21b of the front right and left seats 20a and 20b, and supply detection signals s and Sz corresponding to the front and back positions of the seats to the controller 16. Further, of the microphones 14a and 14b, the microphone 14a is located on the side of the vehicle near the head rest of the right front seat 20a, and the microphone 14b is located on the side of the vehicle near the head rest 1 of the left front seat 20b. A sound pressure signal P corresponding to the sound pressure installed near the head rest section.

P2 is detected and supplied to the controller 16.

Further, the loudspeakers 18a and 18b are respectively installed at the left and right positions of the front dash of the vehicle interior 6, and receive a speaker drive signal supplied from the controller 16, and control sounds corresponding to the drive signals ( output (cancelling sound).

In addition, in FIG. 2, HDa and HDb are sound receiving points (occupant's head).

As shown in FIG. 3, the controller 16 receives detection signals S1. A transfer function calculator 24 inputs St and calculates the current transfer function of the acoustic system, and sound pressure signals PI, P from the microphones 14a and 14b.
2 and the reference signal X manually to generate the speaker drive signal y1. Y
A signal processor 26 that calculates z, a correction filter 28 that corrects the output signals yt and yz from the signal processor 26 using the calculated values of the transfer function calculator 24, and a D/A converter for the output of the correction filter 28. D/A converters 29a, 29 to convert
b and amplified by loudspeaker 18a.

18b. In the figure, CLa and CLb are speaker driving signal cables that extend from the signal processor 26 to the speakers 18a and 18b.

Of these, the transfer function calculator 24 is configured using, for example, a microcomputer, and inputs the seat position detection signal SL+S2 to correct the loudspeakers 18a, 18b and the sound receiving point HDa, as described below. The transfer function of the acoustic system (including the speakers themselves) between HDb is determined.

Now, it is assumed that the speaker drive signals supplied from the speaker drive signal cables CLa and CLb are respectively X1°Xb, and the sound pressures at the sound receiving points HDa and HDb are Ya+Y, respectively, and the loudspeaker 18a to the sound receiving point HDa.

Let the transfer function (including the speaker itself) as a physical constant of HD b be H, , , H, b, respectively, and the loudspeaker 1
8b ~ Letting the transfer functions as physical constants of the sound receiving points HDa and HDb be respectively Hba+Hbb, it can be expressed as follows.

Here, each of the above-mentioned transfer functions when the position of the head (sound receiving point), that is, the seat position changes slightly, is expressed as n1M+Qa
b+ Ab□, then the sound pressure is Y.

The speaker drive signal when Y5 is not changed is 3. If we say father, we get...■.

The above transfer function Hia+ H1lb+ )! bm, H
For bb, set a reference value by actually measuring it at a reference position (for example, the center position in the longitudinal direction of the seat), and when the head position changes, multiply the reference value by a correction coefficient to correct the deviation. .

The correction calculation is performed in the following manner. Here, since the amount of change in the sound receiving points HD'a and HDb is actually often very small, the correction value is calculated assuming a free sound field (this assumption is based on the high frequency range which is the main objective of the present invention). ).

Assume that the sound field advances from the left side of the figure as shown in FIG. 4, and the reception point moves from I to ■. At this time, the sound pressure at point ■ is Y+, the sound pressure at point It is Y2, and Y 2 = A'
Y I ... Represented as ■. A
is a complex number and can be written as IAleJ φ, where IA is the amplitude and φ is the phase correction coefficient. These values are as follows using the distance ro to the point of the speaker itself and the minute distance Δr between the points I→■.

r0+Δr　　　r.

φ−k・Δr (rad)...
■However, k: wave number (-2π/frequency/sound speed).

Since A obtained from the above is equivalent to the change in the transfer function between the speaker sound receiving points, for example, 1'l am = A
is' Ham... It can also be expressed as ■. However, A1. :Speaker 18a~
This is a transfer function correction coefficient between sound receiving points HD a.

In this way, the transfer function correction coefficient is determined based on formulas (1) and (2), and the transfer function is corrected in accordance with formula (2).

As a result, the speaker drive signal sentence, , father, is finally obtained using equation (2).

For such calculation process, the transfer function calculation unit 24
calculates the deviation between the seat position detection signal Sl+S2 and the reference position value, calculates the term . Output. In addition, Ha&+ Hlbt Hbar Hb
b is stored in advance in the memory within the arithmetic unit 24.

Furthermore, as shown in FIG. 3, the signal processor 26 is connected to an A/D converter 4 which inputs a reference signal
6, a digital filter 48 and an adaptive filter 50 that input the conversion output of the A/D converter 46, and the sound pressure signals P, , P2 from the microphones 14a, 14b are A/D
A/D converters 47a and 47b to convert, and this converter 4
7a, 47b and a microprocessor 54 inputting the output signal rL11 of the digital filter 48, and the processed signal y of the adaptive filter 50 is output to the correction filter 28, respectively.

Of these, the digital filter 48 inputs the reference signal X and filters the microphones 14a, 14b and the speaker 18a
18b, the filtered reference signal rt+a ((6) to be described later).

(see equation (7)). The adaptive filter 50 inputs the reference signal X, performs adaptive signal processing based on the filter coefficients set at that time, and generates the speaker drive signal y.
It outputs 1. The microprocessor 54 is
Sound pressure signals P+, Pg and filtered reference signal r
0 manually and the filter coefficients of the adaptive filter 50 by LMS.
Change using an algorithm.

Here, the method of noise control in this embodiment will be explained.

Note that this description assumes a generalized case of multiple microphones and multiple loudspeakers.

Now, the sound pressure signal PL(n) from the i-th microphone
, the sound pressure signal P 9L (+'
l) the jth (j=0.1.2°..., IC-1) term of the transfer function (FIR (finite impulse response) function) between the mth loudspeaker and the second microphone; When expressed as a digital filter, the filter coefficient is 005, the reference signal x (n), and the i-th adaptive filter (i = 0.1°2) that inputs the reference signal , ..., Ik l) as W□, P c (n) ''= Ppt(n
) 10... (3) holds true. Here, all terms with (n) are sample values at sampling time n, L is the number of microphones (two in the first embodiment), and M is the number of loudspeakers (in the first embodiment In 2), IC is the number of taps (filter order) of the transfer function CLm expressed by 8 FIR digital filters, and 1 is the number of taps (filter order) of the adaptive filter.

In the above equation (1), the right side “Σ w, i+ x (n−j
-i) The term J(-y,) is an adaptive filter (coefficient Wm
) represents the output when signal X is input to "Σ Cr.

The term (Σ wffii Hx (n-j-t)) indicates that the signal energy inputted to the m-th speaker is output from the speaker as acoustic energy, and is transmitted to the microphone via the transfer function C (□) in the passenger compartment 6. It represents the signal when it arrives, and furthermore, “Σ Σ CLsj ・ (ΣW m
i.x (n-j-4) ] The entire right side of J represents the sum of the two-blow sounds that reach the first microphone, since the signals reaching the microphones are added up for all speakers.

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 a time domain LMS algorithm. In other words, the filter coefficient W1 is the value obtained by partially differentiating the evaluation function Je with respect to each filter coefficient Wmi.
．． Update.

Therefore, from equation (4), it becomes, but from equation (3), the right side of this equation (4) is r ta (n-i)
Then, the filter coefficient rewriting formula can be obtained from the following equation (7).

Wi (n + 1) = w□ (n) + where,
α is a convergence coefficient and is involved in the speed at which the filter optimally converges and the stability at that time.

Furthermore, the filter correction 28 is applied to the loudspeakers 18a, 1
It has two digital filters corresponding to 8b. Each of the digital filters inputs the calculation (! (the value of the above-mentioned formula)) of the transfer function calculator 24 and corrects it to a filter coefficient corresponding to the calculated value, and also inputs the calculation from the signal processor 26. The output signal #Vt is multiplied by the filter coefficient set at that time, that is, the calculation of the above formula (2) is performed to obtain a corrected speaker drive signal sentence.

, respectively, to the D/A converters 29a and 29b.

Here, although the above equation (2) includes an inverse matrix operation, after sending the data to the correction filter 28, the correction filter 28
Since it is used as a mere coefficient, sufficient calculation speed is ensured.

In the above configuration, the signal processor 26. D/A converter 2
9a, 29b and amplifiers 30a, 30b constitute adaptive control means, and transfer function calculator 24 and correction filter 28
constitutes the correction means.

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

When the engine is driven, the engine rotation speed sensor 10 detects the engine rotation and supplies an engine rotation speed signal X corresponding to this to the controller 16.

In the controller 16, the detection signal
The signal is supplied to a digital filter 4 and an adaptive filter 50 through an A/D converter 46 and an adaptive filter 50, respectively. Of these, the digital filter 48 uses the manually generated reference signal
The filtered reference signal r0 according to equation (6) is calculated in accordance with the transfer function C0 between the microphone and the speaker, and the signal r is output to the microprocessor 54.

On the other hand, the microphones 14a and 14b detect the sound remaining at their installation position (observation position: equivalent to the ear position) and output sound pressure signals PI+P2 corresponding to the sound pressure to the controller 16, respectively. As a result, the sound pressure signals P+, P
z is the A/D converter 47a, 47 in the signal processor 26.
b to the microprocessor 54. The microprocessor 54 uses each input signal to perform the above (7)
) is used to update the filter coefficients. In other words, the evaluation function, that is, the filter coefficient in the direction that minimizes the sum of squares of the sound pressures P, P, is calculated for the filter coefficient W, (n) at the current sampling time n, and is set at the sampling time (n+1). The power filter coefficient W, (n+1) is obtained. Therefore, since the microprocessor 54 outputs a control signal according to the calculated value Wi (n+1) to the adaptive filter 50, the filter coefficient of each filter in the adaptive filter 50 is changed to the newly calculated filter coefficient at the sampling time (n+1). W, (
n+1). In this way, the microprocessor 54 repeats the filter coefficient update command every predetermined sampling time so as to minimize the evaluation function Je.

Therefore, the adaptive filter 50 uses the input reference signal X and the coefficient W according to the filter coefficients set at that time.
, to obtain output values Y+, yz, and output the values )'+ and Vz to the filter correction 28 as drive signals X, , X, respectively.

On the other hand, if the occupant is sitting with the seats h20a and 20b set at their reference positions in the longitudinal direction, it is assumed that the occupant's ears are at the reference position, and the seat position in that state is detected by the seat position detector 12a. , 12b, the signal is extracted as a corresponding electrical signal. Therefore, the transfer function calculator 24 calculates the transfer function correction coefficient using the above-mentioned formulas (1) and (2), and (2)
The transfer function is corrected according to the formula, and calculations are performed based on the formula ■'.However, since the current state is the reference ear position and there is no need for correction, the calculated value of the formula ■' is ultimately "1". become.

Therefore, the coefficient of each digital filter of the correction filter 28 is set to a value corresponding to the calculated value=1.

Therefore, each digital filter of the filter correction 28 is
The corrected speaker drive signals X-, Xb, which are corrected by performing the above equation (2), which multiplies the input speaker drive signals X-, Xb by the filter coefficient set at that time (at the current reference position, X-, (equal to

As a result, the speakers 18a and 18b receive the drive signal 8.
Since a control sound (two-blow sound) is generated according to the sound output, the generated sound output is estimated in advance and propagates through the vehicle interior space corresponding to the transfer function C based on the directivity of the speaker to create a sound field. Form. Therefore, after the control converges, the noise and control sound transmitted from the engine 4 interfere and cancel each other out at the two observation points (microphone installation positions) and in the vicinity thereof.

On the other hand, due to a change of occupants, seat 20a.

Assume that the front and rear positions of 20b are changed. In this case, a detection signal Sl+82 corresponding to the changed seat position is sent to the transfer function calculator 24'. Therefore, the transfer function calculator 24 can calculate the deviation between the reference ear position and the actual value, and the above calculation based on the deviation is repeated. As a result, each filter coefficient of the correction filter 28 is corrected to a value corresponding to the deviation of the ear position, that is, the above-mentioned ``■''. Therefore, each filter of the correction filter 28 corrects the drive signals X, . Output as father. As a result, the speakers 18a, 18
b is the corrected drive signal 9. a.Father.

Since the generated control sound is changed according to the sound pressure, the audible sound pressure is maintained at an almost constant low level even if the position of the passenger's ears changes. This control state is, for example, the seat 2 of the driver's seat.
Similarly, when the seat position of only the seat 0a or the passenger seat 20b is changed, the control sound emitted from each speaker 18a (or 1sb) is adjusted so that it can be sensed by the occupant who has changed the seat position. The noise level caused by the noise is kept approximately minimal and constant.

In this way, even if the ear position changes in a vehicle interior with a complex sound field, the transfer function of the acoustic system associated with the change in ear position can be corrected, and the speaker drive signal can be corrected using the corrected transfer function. Unlike conventional devices, optimal control can be achieved virtually at the ear position.

In addition, since the process related to the correction of the speaker drive signal in the first embodiment does not need to be a real-time process, there is a secondary advantage that there is no need to use a correction means with high-speed computing power. .

Although the first embodiment described above has been described with respect to the case where two sound receiving points and two loudspeakers are installed, the present invention is not necessarily limited to this. It is also possible to have a configuration in which the process is carried out separately.

(Second Embodiment) Next, a second embodiment will be described based on FIGS. 5 to 7. In the second embodiment, the focal length of the acoustic lens is controlled as a physical constant of the acoustic system. Here, the first
Embodiment 7 The same reference numerals are used for the same components as necessary.

In the second embodiment, as shown in FIG. 5, an acoustic lens 62 is installed in front of a loudspeaker 61 in the control sound emission direction, and the focal length of the acoustic lens 62 is always near the passenger's ear position. In addition, the control is performed according to the movement of the occupant's head position. Loudspeaker 61 here
is the loudspeaker IEla in the first embodiment,
It is installed similarly to 18b.

The acoustic lens 62 will be explained with reference to FIG. In the figure, a large number of reflectors 63 are rotatably attached around a bin 64, and each of the reflectors 63 has a shape such that the front ends of the reflectors 63 are tied together, as shown in FIG. It has a long strip shape with one side having the same curvature as the short capsule line Q. Another bin 65 is attached to each reflector 63, and a link member 66 connects each reflector 63 via the bin 65.
is provided. One end of the link member 66 is rotatably attached to worm gears 67a and 67b,
These worm gears 67a and 67b are the servo motor 6.
8.

On the other hand, when the movement of the head position is detected by the seat position detector 70 (ear position detection means) as in the first embodiment described above, and the detection signal is sent to the controller 71, the controller 11 detects the position of the seat. A motor control signal M corresponding to the change in position is sent to the servo motor 68, and the worm gears 67a, 67b are rotated to a predetermined position. The rotation center of the gear 67a coincides with the rotation center of the reflection plate 63a located at the end of FIG.
Further, the distance between the bin portion 66a and the rotation center (rotation radius) is equal to the distance between the bins 64 and 65 for each reflecting plate 63. Therefore, when the worm gears 67a, 67b rotate, the link member 66 moves in translation, and the capsule line Q moves to a position in the direction of Q', and its curvature changes. This embodiment has a configuration in which the curvature increases and the focal length decreases as the lens moves toward QQ'.

The relationship between the amount of rotation of the servo motor 68, the amount of movement of the link member 66, the curvature of the capsule length line Q, and the focal length 11tR is uniquely determined, and the relationship between the amount of rotation of the servo motor 8 and the focal length R is determined in advance. The ratio is stored in the memory of the controller 71. Thereby, the controller 10-71 outputs the motor control signal M according to the input seat position signal S, so that the desired focal length R can be obtained by the acoustic lens 62.

Here, the mechanism by which sound waves are focused by the acoustic lens 62 having the above configuration will be explained. As shown in FIG. 6, the incoming sound waves pass through the gaps between the respective reflecting plates 63, but the average transmission bus of each varies depending on the thickness h of the reflecting plates 63 (see FIG. 7). However, since sound waves have the property of "progressing perpendicularly to the equal phase plane," the sound waves passing through the acoustic lens 63 proceed in a direction in which each path has the same length.

Therefore, by appropriately controlling the paths in the gaps between the respective reflecting plates 63, it is possible to focus the passing sound waves T, , T2 on the point where their path lengths match, for example, in FIG.

The configuration of the control system that provides drive signals to the other speakers 61 is the same as in the first embodiment. In the second embodiment, the controller 71 and the acoustic lens 62 constitute a correction means.

Since the second embodiment is configured and functions as described above, the noise in the vicinity of the passenger's ear position is controlled to a minimum, while the position of the passenger's ear, that is, the seat position in this example, changes due to changes in the passenger. Even in this case, the focal point F of the emitted control sound is maintained approximately at the ear position. At the focal point, that is, near the ear position, the intensity of the sound wave is efficiently increased, and the control sound emitted from the speaker 61 reaches the ear position directly with the same phase, so the canceled sound related to active noise control There is also the advantage that the control becomes easier and the noise reduction at the ear position is even more effective.

(Third Embodiment) Next, a third embodiment will be described based on FIGS. 8 to 11. In the third embodiment, the tonic axis of the control sound is controlled as a physical constant of the acoustic system. Here, the same reference numerals are used for the same components as in the 1.2 embodiment as necessary.

In the third embodiment, the focal point of the acoustic lens 80, which is subjected to flash control, can be moved in the same manner as in the second embodiment. In FIGS. 8 and 9, the acoustic lens 80 includes a reflector 8
1a, and a slide mechanism 8 that slidably supports the reflector unit 81.
2, and a ball screw unit 83 for moving the reflector unit 81 along the slide mechanism 82.

Further, in the figure, 83a is a female screw unit, which is fixed to the reflector unit 81, and 83b is a male screw part, which is fixed to the slide mechanism 82 via a bearing, and the male screw part 83b is It is driven by a servo motor 83c.

This servo motor 83c is driven by a motor control signal M from a controller 84 similar to the second embodiment. 85 is a seat position detector (ear position detection means).

Other configurations are No. 1. This is the same as the second embodiment.

In the third embodiment, the controller 84 and the acoustic lens 80
constitutes the correction means.

Therefore, when a movement of the head position is detected by the seat position detector 85, the reflection plate unit 81 is translated in parallel by the slide mechanism 82 according to the mechanism of the third embodiment. As shown in FIG. 10, this corresponds to the acoustic lens 80 moving in a direction perpendicular to its central axis (see the arrow in the figure), and the real image B of the sound source A also moves largely in the same direction. . Thereby, even if the reflector unit 81 is moved by a small amount, it is possible to move the focal length over a wide range.

Therefore, if the configuration of the third embodiment is applied to, for example, a front door embedded speaker (installed so as to face the left and right directions of the vehicle), its usefulness will be significantly demonstrated. In other words, since the position of the passenger's ear varies mainly in the longitudinal and vertical directions, by moving the focal point in a plane perpendicular to the speaker axis (for example, see Figure 11), this variation can be easily accommodated. The noise level can always be maintained at a substantially minimum and constant level.

Note that the slide mechanism 83 is arranged in a plane 2 perpendicular to the speaker axis.
They function even more effectively when installed individually in different directions.

In each of the above-mentioned embodiments, the noise detection means is configured to detect the sound pressure near the ear position, but the present invention is not necessarily limited to this, and for example, when the noise frequency is in a high frequency range, Since the sound pressure caused by the noise, that is, the active component becomes dominant, a pair of two microphones may be used as the noise detection means to detect the intensity, and the intensity may be controlled to cancel out the intensity at the seat position. According to this, as seen in the above-mentioned article (for example, see Figure 13 on page 163 of Automotive Technology Papers (No. 40, 1989, published by the Society of Automotive Engineers of Japan), even if only two sound sources are used, If a complex intensity 2 sound pressure distribution is observed near the driver's seat,
It is possible to avoid the effects of the easily fluctuating resonance and eliminate the most dominant active component, thereby achieving substantial noise reduction, and the fact that the perceived noise increases even when the ear position changes. The effect is great.

In addition to the above-mentioned embodiments, the ear position detection means of the present invention may include a seat position detector combined with a seat switch that detects the weight of the occupant (that is, whether there is an occupant present or not). When the user is not present, unnecessary control may not be performed, or the direction of the mirror may be determined by detecting the height information of the ear position using a potentiometer and using this information.

Furthermore, the active noise control device of the present invention is not limited to a device applied to a vehicle interior as in the above-mentioned embodiments;
For example, the device may be applied to an aircraft cabin, or it may be a device configured to reduce indoor noise caused by the rotation of an air conditioning outdoor unit. On the other hand, in the above-mentioned embodiment, the case where the noise source is located outside a kind of closed space called the passenger compartment was explained, but the present invention is applicable to the case where the noise source is installed inside such a closed space. can also be applied.

Furthermore, the reference signal detection means of the present invention, that is, the means for obtaining a signal correlated with the noise generation state, is not limited to the configuration for detecting the 4X engine rotation state as described above.
For example, it may be an acceleration pickup attached to a suspension that obtains an electrical signal corresponding to road noise, thereby reducing road noise from the road surface.

The algorithm for updating filter coefficients according to the adaptive control means of the present invention may be a frequency domain LMS algorithm in addition to the time domain LMS (Least Mean 5 square) algorithm as described in the above-described embodiments.

[Effects of the Invention] As explained above, according to the present invention, changes in the ear position of an observer near the sound receiving point are detected, and the receiver is controlled by the adaptive control means in accordance with the detected ear position value. The structure is equipped with a correction means that corrects the physical constants of the acoustic system so that the noise level at the sound point always maintains a minimum value. Even if the position of the ears of the observer changes when sitting in the seat, it is possible to reliably eliminate the situation where the perceived noise becomes louder depending on the occupant, and to keep the noise at the observer's ear position at a minimum and constant. It has the effect of being able to maintain

In particular, in the invention described in claim (4), even if the noise frequency is in a high frequency range of 300 Hz or more and a complex resonance mode is formed in the vehicle interior, the intensity is measured and the intensity is canceled out. By controlling the control sound in this way, it is possible to achieve a reliable noise reduction state by reducing the active component of the sound pressure, which corresponds to the traveling wave that is dominant in the high frequency range, without being affected by the resonance mode. .

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic configuration diagram showing a first embodiment of the present invention, Fig. 3 is a block diagram showing the configuration of the controller of the first embodiment, and Fig. 4 is an ear FIG. 5 is an explanatory diagram illustrating the change in position. FIG. 5 is an explanatory diagram illustrating the acoustic system in the second embodiment of the present invention. FIG. 6 is a plan view illustrating the acoustic lens of the second embodiment. A side view of a reflecting plate constituting the acoustic lens of the second embodiment, FIG. 8 is a plan view illustrating the acoustic lens in the second embodiment of the present invention, and FIG. 9 is a line 1-1 in FIG. FIG. 10 is an explanatory diagram illustrating the movement of the tonic axis in the third embodiment, and FIG. 11 is an explanatory diagram illustrating an application example of the third embodiment. 4: Engine, 6: Vehicle interior, 8: Active noise control device, 1
0; Engine speed sensor, 12a, 12b, 70. s
3: Seat position detector, 14a14b: Microphone,
16, 71, 84: Controller, 18a, 18b Niloud speaker, 24: Transfer function calculator, 26: Signal processor, 28: Correction filter, 29a, 29b: A/D converter, 30a, 30b: Amplifier, 62 , 81: Acoustic lens

Claims (4)

[Claims] (1) A control sound source capable of generating a control sound in an acoustic space where noise is transmitted from the noise source, a reference signal detection means for detecting a reference signal according to the noise generation state of the noise source, and a control sound source in the acoustic space in which noise is transmitted from the noise source. A noise detection means for detecting a noise level at a predetermined sound receiving point, and an adaptation for driving the control sound source so that the detection value of the noise detection means is minimized based on the detection values of the reference signal detection means and the noise detection means. an active noise control device comprising: an ear position detection means for detecting a change in the ear position of an observer near the sound receiving point; An active noise control device comprising: a correction means for correcting physical constants of the acoustic system so that the noise level at the sound receiving point controlled by the control means always maintains a minimum value. (2) The active noise control device according to claim 1, wherein the correction means is a means for correcting a transfer function of an acoustic system from the controlled sound source to the sound receiving point. (3) The active noise according to claim (1), wherein the correction means is a means for correcting the direction of the acoustic output axis from the controlled sound source toward the sound receiving point or the focal length of an acoustic lens. Control device. (4) Claims (1) and (2) characterized in that the noise control means is means for detecting acoustic intensity.
Or the active noise control device described in (3).