JP2008137636A - Active noise control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active noise control device which reduces low-frequency road noise (drumming noise), alleviating effects on musical sound and having a simple configuration. <P>SOLUTION: In accordance with vehicle speed V and the magnitude P of an audio signal of an audio, the amplitude of a control signal Sca output from an active noise control part 12 by a vehicle speed dependent control signal adjusting part 51 and an audio signal dependent control signal adjusting part 52 and supplied to a composition unit 26 is adjusted. This configuration eliminates the necessity of an audio cancel circuit (circuit comprising a subtractor and an audio cancel filter) for canceling an audio signal Sa from output of a microphone 8, which is essential for conventional technologies. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a speaker that outputs an audio signal converted into a musical sound is output together with the musical sound together with a canceling sound having an opposite phase to the vehicle interior noise, and cancels the vehicle interior noise to mute the passenger ( The present invention relates to an active noise control device that enables a passenger to hear a musical sound from the speaker more clearly.

  The vibration of the wheel received from the road (road) is transmitted to the vehicle body via the suspension, and is excited by the acoustic resonance characteristic of the closed space, particularly in the passenger compartment, and has a peak at about 40 Hz and a low bandwidth of 20 to 150 Hz. There has been proposed an active noise control device that cancels out vehicle interior noise caused by high-frequency road noise (also called “drumming noise”) (Patent Document 1).

  As shown in the block diagram of FIG. 10, in the active noise control device 2 described in Patent Document 1, in the vehicle interior 4, the vehicle interior noise and the canceling sound output from the speaker 6 are received. The microphone 8 is provided in the belly part of the acoustic eigenmode of the passenger compartment 4. The active noise control unit 12 constituting the active noise control unit (ANC unit) 18 adapts the control signal so that the signal (error signal) obtained from the microphone 8 through the A / D converter 14 is minimized. And the generated control signal is supplied to the speaker 6 via the D / A converter 16 and the amplifier 10.

JP 2000-322066 A (FIGS. 1 and 3)

  Recently, passenger cars are equipped with audio units for enjoying the music of various music sources such as tuners, compact discs, and hard disks.

  FIG. 11 is a block diagram showing a configuration according to the related art of the audio control device 22 for a vehicle in which the audio unit 20 and the active noise control device 2 shown in FIG. 10 are integrally configured. In FIG. 11, the same components as those shown in FIG.

  In the vehicle acoustic control device 22, the audio signal Sa output from the audio unit 20 and the control signal Sc as the canceling sound signal output from the active noise control unit 12 are combined by the adder 24 of the combining unit 26. The signal is supplied to the speaker 6 in the passenger compartment 4 via the D / A converter 16 and the amplifier 10, and is output from the speaker 6 as a synthesized sound of musical sound and canceling sound.

  The microphone 8 receives the synthesized sound of the musical sound and the canceling sound and the vehicle interior noise, and outputs an error signal obtained by adding the musical sound (audio signal) to the difference between the noise (noise signal) and the canceling sound (cancelling sound signal). .

  This error signal is supplied as an error signal Ea to the subtracted port of the subtractor 28 through the A / D converter 14 of the ANC unit 18a. In this case, an audio signal Sb obtained by converting the audio signal Sa by an audio cancellation filter (audio compensation filter) 30 that is a digital filter is supplied to the subtraction port of the subtractor 28.

  Here, the audio cancellation filter 30 is connected from the input side of the D / A converter 16 to the amplifier 10, the speaker 6, the acoustic transmission path from the speaker 6 to the microphone 8, the microphone 8, and the output side of the A / D converter 14. This is a digital filter having a path transfer function, that is, a path transfer function from the input of the D / A converter 16 to the output of the A / D converter 14. For convenience of understanding, this transfer function is called a transfer function between the speaker 6 and the microphone 8 and corresponds to the transfer function C between the speaker 6 and the microphone 8 in the block of the audio cancellation filter 30. It is described as a simulated transfer function C ^.

  Therefore, by subtracting the audio signal Sb from the error signal Ea by the subtractor 28, in other words, by canceling the audio signal Sb corresponding to the musical sound from the output of the microphone 8, noise is generated on the output side of the subtractor 28. An error signal e corresponding to the difference between the canceling sound and the canceling sound is obtained. The active noise control unit 12 generates the control signal Sc so that the error signal e becomes zero, and supplies the control signal Sc to the other addition port of the adder 24 in which the audio signal Sa is supplied to one addition port.

  With this configuration, at the point (position) where the microphone 8 is provided, a large vehicle interior noise at the belly position of the acoustic eigenmode (vehicle interior noise that increases in resonance), that is, low-frequency road noise ( Drumming noise) is canceled out by the canceling sound, and the musical sound based on the audio signal Sa can be heard clearly throughout the passenger compartment 4.

  When the error signal Ea is directly supplied to the active noise control unit 12 without providing the audio cancel circuit (the audio cancel filter 30 and the subtractor 28) (e = Ea), the load included in the error signal Ea. The bass sound (lowest sound) close to the frequency of the noise (drumming noise) is also silenced at the same time, giving the passenger a sense of incongruity.

  In the vehicle acoustic control apparatus 22 according to the prior art shown in the example of FIG. 11, a relatively large and heavy speaker 6 as an in-vehicle electrical component is used for audio and noise control with respect to the audio unit 20 and the ANC unit 18a. It is used for both. In addition, the amplifier 10 that consumes a large amount of power and generates heat as an in-vehicle electrical component is also used for audio and noise control. As described above, the vehicle acoustic control device 22 in which the audio unit 20 and the active noise control device 2 shown in FIG. 10 are integrally formed is excellent in terms of volume, power consumption, and cost.

  Incidentally, in-vehicle electrical components such as the vehicle acoustic control device 22 are required to further reduce the cost and improve the theoretical reliability such as MTBF (average time between failures).

  From this point of view, the vehicle acoustic control device 22 according to the prior art shown in FIG. 11 requires as many ANC units 18a and synthesizing units 26 as the number of speakers 6, and in particular, a 4-channel surround system that has been attracting attention recently. In the 5.1 channel surround system, the number of harnesses connecting between the ANC unit 18a and the synthesis unit 26 shown at points a and b in FIG. 11 is the number of speakers (two for each speaker). It was found that this was one of the causes of the increase in the cost of the on-vehicle electrical components and the decrease in the theoretical reliability.

  Further, it has been found that the audio cancellation circuit including the audio cancellation filter 30 and the subtracter 28 is complicated as a control system, and as a result, the cost is increased as a control system for the vehicle acoustic control device 22 as a whole.

  The present invention has been made in view of such problems, and an active noise control device having a simple configuration with little influence on musical tone without using an audio cancel circuit that cancels an audio signal from a microphone output is provided. The purpose is to provide.

  An active noise control device according to the present invention is a mixed sound of a vehicle interior noise, a musical sound from a sound output means based on an audio signal, and a canceling sound of the vehicle interior noise from the sound output means based on a control signal. Audio signal detection for detecting the magnitude of the audio signal in an active noise control device that detects the error signal by a sound detection means and outputs a control signal for generating the canceling sound based on the error signal to the sound output means Means, vehicle speed detecting means for detecting the vehicle speed, audio signal dependent control signal adjusting means for adjusting the amplitude of the control signal in accordance with the detected magnitude of the audio signal, and in accordance with the detected vehicle speed. Vehicle speed dependent control signal adjusting means for adjusting the amplitude of the control signal is provided.

  According to this invention, the audio signal is output from the output of the sound detection means such as a microphone by adjusting the amplitude of the control signal output from the active noise control unit according to the vehicle speed and the size of the audio signal. Therefore, it is possible to construct a low-cost active noise control device that eliminates the need for an audio cancel circuit for canceling the sound and that has little influence on the musical sound.

  Since the audio cancel circuit is not required, the configuration of the active noise control device is simplified, the number of harnesses is reduced, the volume and cost (component cost, manufacturing cost) are reduced, and the theoretical reliability is improved. Can do.

  In this case, the vehicle speed dependent control signal adjusting means adjusts the amplitude of the control signal to zero when the vehicle speed is zero. When the vehicle speed is zero, no low-frequency road noise (drumming noise) is generated. In other words, low-frequency road noise (drumming noise) is generated only during driving, so there is no need to generate a canceling sound based on the control signal. .

  The audio signal dependent control signal adjusting means adjusts the amplitude of the control signal to zero when the audio signal is larger than a predetermined size, thereby reducing low frequency road noise (drumming noise). Let the music play at the expense of the suppression effect.

  Further, the vehicle speed dependent control signal adjusting means adjusts the amplitude of the control signal to be a zero value when the vehicle speed is zero, and the amplitude of the control signal when the vehicle speed increases from zero to a predetermined vehicle speed. The audio signal dependent control signal adjusting means adjusts the control signal so as to increase from zero value to a reference amplitude value according to the increase in the vehicle speed, when the magnitude of the audio signal is a predetermined magnitude or more, When the amplitude of the audio signal decreases from the predetermined size to zero, the amplitude of the control signal is reduced to zero according to the decrease in the size of the audio signal. It adjusts so that it may become large from a reference amplitude value to.

  By adjusting the amplitude of the control signal to increase from the zero value to the reference amplitude value according to the increase in the vehicle speed, the amplitude of the control signal according to the increase in vehicle interior noise due to low-frequency road noise (drumming noise) Can be increased to increase the canceling sound. Also, by adjusting the amplitude of the control signal to increase from zero to the reference amplitude according to the decrease in the size of the audio signal, the size of the audio signal is small, in other words, the bass sound in the musical tone. When the volume of the sound is a small volume that cannot be heard by the ear or body (feel), low frequency road noise (drumming noise) can be suppressed by the canceling sound. That is, the musical sound can be heard clearly even at a low volume.

  Further, the control parameter related to the stability of the control is adjusted according to the magnitude of the audio signal and / or the vehicle speed. As the control parameter to be adjusted, a step size parameter and / or a stability compensation coefficient are used. In the active noise control apparatus that adjusts the amplitude of the control signal output from the active noise control unit in accordance with the magnitude of the audio signal and / or the vehicle speed, further, the magnitude of the audio signal and / or the vehicle speed. By adjusting the step size parameter and / or stability compensation coefficient of the active noise control unit according to the above, the ON region of the active noise control unit can be stably expanded.

  According to the present invention, the amplitude of the control signal for canceling the vehicle interior noise is adjusted according to the vehicle speed and / or the size of the audio signal, so that the audio signal is canceled from the output of the sound detection means. It is possible to construct an active noise control device that eliminates the need for an audio cancellation circuit and has little influence on the musical sound.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a vehicle acoustic control apparatus 40 to which an embodiment of an active noise control apparatus according to the present invention is applied. In the vehicle acoustic control apparatus 40 shown in FIG. 1, the same or corresponding parts as those shown in FIGS. 10 and 11 are denoted by the same reference numerals.

  The vehicle acoustic control device 40 mounted on the vehicle basically has an external input from an external music source such as a musical sound of various internal music sources 60 such as a tuner, a compact disc, a hard disk, or a portable music playback device ( An audio unit 20a for outputting an audio signal Sa for enjoying the musical sound obtained through the AUX input 62) and an active noise control unit (ANC unit) 18b for canceling low-frequency road noise (drumming noise).

  The audio unit 20a and the ANC unit 18b are configured to include a computer, and operate as function realizing means for realizing various functions by the CPU executing programs stored in a memory such as a ROM based on various inputs. .

  The microphone (sound detection means) 8 that receives the vehicle interior noise, the canceling sound of the vehicle interior noise, and the musical sound is positioned at the position of the abdomen in the primary or secondary mode of the acoustic eigenmode in the front-rear direction of the vehicle interior 4 {20 In the low-frequency road noise with a bandwidth of ˜150 Hz, the sound pressure of the standing wave of the vehicle interior resonance sound of 40 [Hz] or 80 [Hz] is provided. Specifically, if the vehicle is a sedan, the cross-section in the width direction of the vehicle is a closed space, for example, near the front position, for example, near the feet of the front seat, near the rearview mirror, behind the instrument panel, etc. Yes (Patent Document 1).

  In order to enhance the surround effect of the 5ch sound, the plurality of speakers (sound output means) 6 are, for example, left and right kick panels on the front seat side of the vehicle, lower center of the instrument panel, and left and right bodies below the C pillar on the rear seat side. It is arranged in the part etc. Note that the 0.1ch woofers have almost no directionality and are therefore arranged at arbitrary positions.

  The synthesizing unit 26 synthesizes the audio signal Sa output from the amplifier 54 of the audio unit 20a and the control signal Sca as the canceling sound signal output from the ANC unit 18b by the adder 24 into the synthesized signal Ss. Ss is supplied to the speaker 6 in the passenger compartment 4 via the D / A converter 16 and the amplifier 10.

  The speaker 6 outputs a composite sound of a musical sound based on the audio signal Sa corresponding to the composite signal Ss and a canceling sound based on the control signal Sca.

  The microphone 8 receives the musical sound, the canceling sound and the vehicle interior noise output from the speaker 6, and outputs an error signal in which the musical sound is added to the vehicle interior noise and the canceling sound (difference). This error signal is supplied as an error signal Ea to the input port of the active noise control unit 12 through the A / D converter 14 of the ANC unit 18b.

  The active noise control unit 12 performs an arithmetic process so that the error signal Ea has a zero value, that is, “noise− (cancellation sound + musical sound)” has a zero value, and outputs a control signal Sc.

  Two adjustment units that adjust the amplitude (gain) of the control signal Sc are connected in series (the connection order is not limited). The control signal amplitude adjustment unit 50 includes the active noise control unit 12, the adder 24, and the like. It is provided between.

  The control signal amplitude adjusting unit 50 is a vehicle speed dependent control signal adjusting unit (vehicle speed dependent) that adjusts the gain Gv to adjust the amplitude of the control signal Sc according to the vehicle speed V detected by the vehicle speed sensor (vehicle speed detecting means) 42. Control signal adjusting means) 51 and a gain Gp for adjusting the amplitude of the control signal Sc according to the magnitude P of the audio signal detected by the magnitude detector (audio signal detecting means) 44 from the output of the audio unit 20a. The audio signal dependence control signal adjustment unit (audio signal dependence control signal adjustment means) 52 is adjusted.

  Note that the vehicle speed dependent control signal adjusting unit 51 and the audio signal dependent control signal adjusting unit 52 are configured such that the resistance division ratio of electronic volume {gain (gain) is between 1 (0 [dB]) and 0 (−∞ [dB]). And the like.

  The control signal Sca after amplitude adjustment (Sca = Gv × Gp × Sc) output from the control signal amplitude adjustment unit 50 is supplied to the other input port of the adder 24 to which the audio signal Sa is supplied to one input port. Supplied.

  FIG. 2A shows a vehicle speed dependent gain characteristic Gv1 (solid line) set in the vehicle speed dependent control signal adjusting unit 51 and an audio signal dependent gain characteristic Gp1 (dotted line) set in the audio signal dependent control signal adjusting unit 52. .

  In the vehicle speed dependent gain characteristic Gv1, the vehicle speed (predetermined vehicle speed) Vth [km / h] near the middle between the vehicle speed V = 0 [km / h] and the vehicle speed V = 100 [km / h] is a threshold, and the vehicle speed 0 The gain is zero (−∞ dB) between [km / h] and the vehicle speed Vth [km / h], and the gain is 1 between the vehicle speed Vth [km / h] and the maximum speed Vmax exceeding 100 [km]. Value (0 [dB]).

  In the audio signal dependent gain characteristic Gp1, the size (predetermined size) Pth of the audio signal near the middle between the audio signal size P = 0 and the maximum audio signal size Pmax is a threshold, and the audio signal The value is 0 (0 [dB]) between the magnitude 0 and the predetermined magnitude Pth, and is zero (−∞ [dB]) between the predetermined magnitude Pth and the maximum audio signal volume Pmax. The

  The operation of the vehicle acoustic control apparatus 40 basically configured as described above will be described with reference to the flowchart of FIG. 3 executed by the ANC unit 18b.

  In step S1, it is determined whether or not the vehicle speed V obtained from the vehicle speed sensor 42 is equal to or higher than the predetermined speed Vth. When the vehicle speed V is equal to or higher than the predetermined speed Vth (V ≧ Vth), it is obtained from the magnitude detector 44 in step S2. It is determined whether or not the magnitude P of the audio signal is equal to or smaller than a predetermined magnitude Pth (P ≦ Pth).

  When the determination result of step S1 is negative, for example, when the vehicle is stopped due to a signal or the like, low-frequency road noise (drumming noise) does not occur. Therefore, below the predetermined vehicle speed Vth, the gain Gv1 of the vehicle speed-dependent control signal adjustment unit 51 is set to zero (Gv1 = 0) so that the control signal Sca is not generated. Therefore, in this case, the value of the control signal Sca output from the control signal amplitude adjusting unit 50 is set to zero (Sca = Gv1 × Gp1 = 0 × Gp1 = 0).

  As a result, only the audio signal Sa is supplied to the speaker 6 as the combined signal Ss from the adder 24, and only the musical sound is detected by the microphone 8 while the vehicle is stopped. On the other hand, when the speed is equal to or lower than the predetermined speed Vth, the microphone 8 receives a musical sound and low frequency road noise (drumming noise) having a relatively low sound pressure. At the occupant position, the musical sound is received and the position of the microphone 8 (the position where the sound pressure of the low-frequency road noise (drumming noise) is the highest in the passenger compartment 4 because it is the antinode position of the acoustic eigenmode)}. Low-frequency road noise (noise) with low sound pressure is received.

  If step S1 and step S2 are affirmative, that is, if the vehicle speed V is equal to or higher than the predetermined speed Vth and the audio signal magnitude P is smaller than the predetermined magnitude Pth, low-frequency road noise (drumming noise) and The amplitude of the control signal Sca is adjusted in consideration of the property that a bass sound (sound having the lowest frequency among musical sounds) having the same frequency cannot be heard by the human ear or felt by the body.

  That is, the gain Gp of the audio signal dependent control signal adjustment unit 52 is set to 1 (Gp = 1). In this case, the value of the control signal Sca output from the control signal amplitude adjusting unit 50 is the value of the control signal Sc that is the reference amplitude value (Sca = Gv1 × Gp1 × Sc = 1 × 1 × Sc = Sc ).

  That is, in an in-vehicle environment where the vehicle speed V is equal to or higher than the predetermined speed Vth and the low-frequency road noise (drumming noise) is relatively large, the audio volume (not shown) is adjusted, and the audio signal is narrowed down to listen to the musical sound. When active, the active noise control unit 12 silences low-frequency road noise (drumming noise). Even if the sound is muted and the bass sound of the low frequency road noise (drumming noise) corresponding to the musical sound is suppressed, the bass sound with a low sound pressure can be heard by the human ear or felt by the body. Since this is not possible, the influence of the listener (passenger) on listening to the music is very small.

  Further, when the audio signal size P is larger than the predetermined size Pth, the active noise control unit 12 does not mute low frequency road noise (drumming noise) regardless of the vehicle speed V. Therefore, the listener actively listens to the musical tone including the bass sound.

  Of course, when the surround effect in a high-performance audio system is to be applied, Gv = 0 in all speed ranges and Gp = 0 in all audio signal magnitude ranges, low frequency road noise (drumming noise) by the active noise control unit 12 is set. It is also possible not to perform the mute operation.

  In addition to the control characteristics shown in FIG. 2A, as shown in FIG. 2B, the vehicle speed dependent gain characteristic Gv2 is gradually increased from the 0 value when the vehicle speed V increases from zero to a predetermined speed Vth, and the control signal Sca Is gradually increased from the zero value, and when the vehicle speed V is in the vicinity of the predetermined speed Vth, the value of the vehicle speed-dependent gain characteristic Gv is set to 1 and the mute operation is normal, and the vehicle speed V exceeds the predetermined speed Vth and is higher than the predetermined speed Vth. When the vehicle speed V is about 100 [km / h] or more, the value of the vehicle speed dependent gain characteristic Gv becomes 0, while the audio signal dependent gain characteristic Gp2 The signal size P can be gradually decreased from 1 value toward 0 value from zero to the maximum Pmax of the audio signal size P. If set as shown in FIG. 2B, active noise control can be performed with less discomfort than the setting shown in FIG. 2A.

  In this case, as shown in FIG. 2C, when the vehicle speed V increases from zero to the predetermined speed Vth, the vehicle speed dependent gain characteristic Gv2 is gradually increased from 0 value so that the control signal Sca gradually increases from the zero value. When the vehicle speed V is equal to or higher than the predetermined speed Vth, the value of the vehicle speed dependent gain characteristic Gv is set to 1 and the mute operation is normally performed. On the other hand, the audio signal dependent gain characteristic Gp2 has an audio signal size P from zero. It is possible to gradually decrease from 1 value toward 0 value until the maximum Pmax of the magnitude P of the audio signal. Active noise control having substantially the same effect as the setting of FIG. 2B can be performed.

  As described above, the vehicle acoustic control apparatus 40 according to the above-described embodiment includes the audio unit 20a as the generation unit of the audio signal Sa, the musical sound based on the audio signal Sa, and the canceling sound of the vehicle interior noise based on the control signal Sca. A microphone 6 that outputs a mixed sound of the vehicle interior noise, the canceling sound, and the musical sound as an error signal Ea, a vehicle interior noise signal corresponding to the vehicle interior noise in the error signal Ea, The control signal Sc is subjected to signal processing so that the difference between the canceling sound signal corresponding to the canceling sound and the synthesized signal of the audio signal Sa corresponding to the musical sound {vehicle interior noise signal- (offset sound signal + musical sound)} is minimized. , An active noise control unit 12 that outputs a signal, a magnitude detector 44 that detects the magnitude P of the audio signal, and a vehicle speed sensor that detects the vehicle speed V. 42, an audio signal dependent control signal adjusting unit 52 that adjusts the amplitude of the control signal Sca according to the detected magnitude P of the audio signal, and a vehicle speed that adjusts the amplitude of the control signal Sca according to the detected vehicle speed V A dependence control signal adjustment unit 51.

  According to this configuration, the amplitude of the control signal Sca output from the active noise control unit 12 and supplied to the synthesizing unit 26 is adjusted according to the vehicle speed V and the magnitude P of the audio signal. An audio cancel circuit that cancels the audio signal Sa from the output of the microphone 8 as shown in the prior art {a circuit composed of the subtractor 28 and the audio cancel filter 30} is unnecessary, and the vehicle has a simple configuration and has little influence on the sound. The acoustic control device 40 can be constructed.

  Since the audio cancel circuit becomes unnecessary, the number of harnesses can be reduced, the volume and cost (component cost, manufacturing cost) can be reduced, and the theoretical reliability can be improved. In other words, the wiring for the harness for transmitting the audio signal Sa to the size detector 44 may be one, and the audio signal dependent control signal adjustment unit 52 for other speakers is provided in the printed circuit board on which the ANC unit 18b is mounted. Can be connected by a substrate pattern. Similarly, only one wiring is required for the vehicle speed V transmission harness from the vehicle speed sensor, and the wiring pattern is connected to the vehicle speed dependent control signal adjusting unit 51 for other speakers in the printed circuit board on which the ANC unit 18b is mounted. be able to. That is, when there are five speakers, the number of harnesses required in the prior art is ten, which can be reduced to two times one fifth.

  As described above, the vehicle speed dependent control signal adjustment unit 51 adjusts the amplitude of the control signal Sca to zero when the vehicle speed V is zero, in other words, as shown in FIGS. 2A to 2C. If the gain Gv (Gv1, Gv2, Gv3) is adjusted to zero when the vehicle speed V is zero, the canceling sound based on the control signal Sca when no low-frequency road noise (drumming noise) is generated It is not necessary to generate. In the first place, low-frequency road noise (drumming noise) occurs only during driving. In this case, the listener can hear only the musical sound.

  Further, the audio signal dependent control signal adjustment unit 52 adjusts the amplitude of the control signal Sca to zero when the magnitude P of the audio signal is equal to or larger than the predetermined magnitude Pth, in other words, FIG. As shown in 2A, by adjusting the gain Gp1 to zero, the musical sound that the listener wants to hear at the expense of the effect of suppressing low frequency road noise (drumming noise) by the ANC unit 18b. It is controlled to let you hear. This configuration is suitable for application to a musical sound that includes a base sound having a frequency close to the acoustic frequency of low-frequency road noise (drumming noise) in the vehicle interior noise.

  Further, the vehicle speed dependent control signal adjustment unit 51 adjusts the amplitude of the control signal Sca to zero when the vehicle speed V is zero, and when the vehicle speed V increases from zero to a predetermined vehicle speed Vth, As the vehicle speed V increases, the amplitude is adjusted to increase from a zero value to a reference amplitude value (the amplitude value of the control signal Sca when the gains Gv and Gp are 1 values, respectively, in this case, Sc = Sca). (See Gv2 in FIG. 2B and Gv3 in FIG. 2C.) On the other hand, the audio signal dependent control signal adjustment unit 52 sets the amplitude of the control signal Sca to zero when the magnitude P of the audio signal is equal to or greater than the predetermined magnitude Pth. When the magnitude P of the audio signal decreases from the predetermined magnitude Pth to zero, the amplitude of the control signal Sca is adjusted according to the decrease in the magnitude P of the audio signal. Adjusting the B value so as to increase to the reference amplitude value (Figure 2B, reference Gp2 in Figure 2C) above configuration.

  Thus, by adjusting the amplitude of the control signal Sca so as to increase from the zero value to the reference amplitude value according to the increase in the vehicle speed V, according to the increase in the vehicle interior noise due to the low frequency road noise (drumming noise). The amplitude of the control signal Sca can be increased to increase the canceling sound. Further, by adjusting the amplitude of the control signal Sca from the zero value to the reference amplitude value according to the decrease in the size P of the audio signal, the size P of the audio signal is small. When the volume of the bass sound is a small volume that cannot be heard by the ear or body (feel), low frequency road noise (drumming noise) can be suppressed by the canceling sound. That is, the musical sound can be heard clearly even at a low volume.

  According to the above-described embodiment, the amplitude of the control signal Sca output from the active noise control unit 12 and supplied to the synthesis unit 26 is adjusted according to the vehicle speed V and / or the audio signal magnitude P. Therefore, an audio cancel circuit for canceling the audio signal from the output of the microphone 8 is not required, and the vehicle acoustic control device 40 having a simple configuration with little influence on the musical sound can be constructed.

  When the external input 62 is not present, the audio volume 45 is provided in the audio unit 20b and adjusts the set sound volume output from the speaker 6 as in the vehicle acoustic control device 40A shown in FIG. The set volume P ′ obtained from (set volume adjusting means, set volume adjuster) can be replaced with the magnitude P of the audio signal. In this case, the audio signal dependent control signal adjusting unit 52 constituting the ANC unit 18c is replaced with a volume dependent control signal adjusting unit (adjusting means) 52a having the same configuration, and the size detector 44 is an audio volume 45. Is replaced by

  FIG. 5 is a block diagram showing a configuration of a vehicle acoustic control apparatus 40B including an ANC unit 18d to which still another embodiment of the active noise control apparatus according to the present invention is applied. In the vehicle acoustic control device 40B shown in FIG. 5, the same or corresponding components as those shown in FIG.

  In the vehicle acoustic control device 40B, the active noise control unit 12 shown in FIG. 1 is replaced with an active noise control unit 12a.

  FIG. 6 is a block diagram illustrating a configuration example of the active noise control unit 12a. The active noise control unit 12a is a circuit using a feedforward type filtered-X LMS algorithm, and is fixed by a vehicle type, for example, a cosine wave (cos) synchronized with a drumming frequency fd [Hz] of about 42 [Hz]. ) Reference signal generator 70 (cosine wave signal generator 70a and sine wave signal generator 70b) for generating a signal cos2πfdt and a sine wave (sin) signal sin2πfdt, and a drumming frequency in the vehicle compartment 4 from the speaker 6 to the microphone 8 The simulated transfer function C ^ {simulated transfer function (real part) Cr (fd) and simulated transfer function (imaginary part) Ci (fd)} simulating the transfer characteristic of fd sound (drumming noise) is set, and the cosine is set. The reference signal r (n) {simulated cosine wave signal reference is applied to the wave signal cos2πfdt and the sine wave signal sin2πfdt. A reference signal generator (filter) 74 for generating a reference signal rc and a reference signal rs} which is a simulated sine wave signal, a reference signal r (n) and a corrected error signal e (n) to be described later are supplied. Filter coefficients A and B of one-tap adaptive filters (adaptive notch filters) 71 and 72 based on an adaptive control algorithm that minimizes the error signal e (n), for example, an LMS (Least Mean Square) algorithm that is a kind of steepest descent method Filter coefficient updaters (algorithm calculators) 91 and 92, and a cosine wave signal multiplied by the coefficient A supplied from the 1-tap adaptive filters 71 and 72 and a sine wave signal multiplied by the coefficient B are added. And an adder 96 for generating a control signal Sc (n) {Sc (n) = A × cos 2πfdt + B × sin2πfdt}.

  The active noise control unit 12a further includes coefficient multipliers 81 and 82 in which filter coefficients A and B having the same value as the filter coefficients A and B are set. The coefficient multipliers 81 and 82 respectively supply a signal obtained by multiplying the reference signal rc by the filter coefficient A and a signal obtained by multiplying the reference signal rs by the filter coefficient B to the adder 94. The adder 94 is a simulated canceling sound signal (estimated canceling sound signal detected at the position of the microphone 8), which is a composite signal of the reference signal rc multiplied by the filter coefficient A and the reference signal rs multiplied by the filter coefficient B. Signal) Sk is generated and supplied to the stability compensation coefficient multiplier 98. The stability compensation coefficient multiplier 98 supplies a stabilization signal α · Sk obtained by multiplying the simulated cancellation sound signal Sk by the stability compensation coefficient α (0 <α <1) to one input port of the adder 100.

  The error signal Ea detected by the microphone 8 is supplied to the other input port of the adder 100. The adder 100 supplies an error signal e (n) obtained by correcting the error signal Ea with the stabilization signal α · Sk to the filter coefficient updaters 91 and 92.

  The configuration of the active noise control unit 12 of the vehicle acoustic control device 40 shown in FIGS. 1 and 4 is compared with the configuration of the active noise control unit 12a shown in FIG. , 92, the audio signal size P and the vehicle speed V are not present, and the filter coefficient multipliers 81 and 82 and the stability compensation coefficient multiplier 98 are not present.

  The active noise control unit 12a employs an adaptive notch filter, and as is well known, the updated filter coefficient A (n + 1) includes the filter coefficient A (n) before update and the error signal e (n). , The reference signal r (n) and the step size parameter μ are calculated by the following equation (1). The updated filter coefficient B (n + 1) is calculated in the same manner.

  A (n + 1) = A (n) −μe (n) r (n) (1)

  Next, the operation of the vehicle acoustic control device 40B of FIG. 5 having the active noise control unit 12a of FIG. 6 will be described with reference to the control parameter switching table 102 of FIG. 7 and the flowchart of FIG. . In this embodiment, the stability compensation coefficient α and the step size parameter μ, which are control parameters related to control stability, are switched (variable) according to the vehicle speed V and the audio signal magnitude P. .

  Each value described below is an example, and can be determined experimentally and by simulation for each vehicle type and vehicle type grade.

  As shown in FIG. 7, the vehicle speed V is between a low speed Vl (for example, 20 [km / h]) to a medium speed Vm (for example, 100 [km / h]), and the audio signal size P (audio signal). Is measured by, for example, a voltage value), which is equal to or lower than the sound threshold P1, that is, the vehicle speed V is Vl <V <Vm and the audio signal size P is In the region indicated by double hatching of 0 ≦ P <Pl, the active noise control unit 12a performs normal (standard) drumming noise elimination control.

  That is, the active noise control unit 12a constituting the ANC unit 18d uses the step size parameter μ (μ1 = 0.02: standard value) for performing normal control as the filter coefficient updaters 91 and 92 (in practice, the filter 7 is stored in the coefficient updaters 91 and 92, and the stability compensation coefficient α (α1 = 0.2: standard for performing normal control) is set. Value) is set in the stability compensation coefficient multiplier 98.

  On the other hand, in a region where the vehicle speed V is relatively high (Vm <V <Vh) and the size P of the audio signal is relatively small, 0 ≦ P <Pl, the signal detected by the microphone 8 is The ratio of wind noise, engine sound, etc. is larger than drumming noise to be silenced. As a result, it is assumed that there is a problem in stability with the value of the step size parameter μ and the value of the stability compensation coefficient α set in the normal drumming noise elimination control.

  Similarly, even if the vehicle speed V is in the medium speed range (Vl <V <Vm), the drumming noise is generated in the region where the magnitude P of the audio signal is a level indicated by hatching of medium Pl ≦ P <Pm. In this case, there is a problem in stability with the value of the step size parameter μ and the value of the stability compensation coefficient α set in the normal drumming noise elimination control. It is assumed that it will occur. Therefore, in the hatching area, the control parameter (μ1 / 4, 2 × α1) in which the step size parameter μ is ¼ and the stability compensation coefficient α is doubled with respect to the control parameter (μ1, α1) in the normal area. Has been changed.

  The physical meaning of changing the step size parameter μ will be described in more detail. When the audio signal Sa is increased by the user operating the electronic volume of the music source 60 or the like, the musical tone increases in proportion to the audio signal Sa. When the musical tone increases, the musical tone having a frequency component close to the frequency of the drumming noise (42 [Hz]) in the musical tone increases and is received by the microphone 9.

  Actually, since the temporal change in the magnitude of the musical sound component is extremely rapid compared to the temporal change in the magnitude of the drumming noise component, the noise component recognized by the filter coefficient updaters 91 and 92 fluctuates. As a result, the noise control in the ANC unit 18d may become unstable. Therefore, as the size of the audio signal Sa increases, the robustness of noise control is improved by reducing the step size μ.

  As shown in the sensitivity functions ga (f) and gb (f) in FIGS. 9A and 9B, when the step size μ is made smaller than when the step size μ is large, the sensitivity functions ga (f) and gb ( f) Above, the control frequency fd, in this case, the silencing frequency range centered on the above 42 [Hz] is narrowed, but the silencing effect is enhanced (the negative function value is increased).

  If the step size μ is reduced, the convergence time to the target output will be longer, but it will operate accurately at the control frequency, and unnecessary low-frequency components (in this case, musical tones with the same frequency components). ) And impulsive noise can be said to be more robust. That is, the silencing effect at the frequency synchronized with the drumming noise (the control frequency fd) is narrow, but the silencing effect becomes high at that frequency, so that the active noise control is unstable due to the influence of the change in the audio signal Sa. Can be prevented.

  Next, the physical meaning of changing the stability compensation coefficient α will be described. As can be seen from FIG. 6, the simulated canceling sound signal Sk obtained on the output side of the adder 94 is a cosine having a control frequency fd of drumming noise. Since the reference signal generator 74 applies the simulated transfer characteristic C ^ {simulated transfer characteristic (real part) Cr and simulated transfer characteristic (imaginary part) Ci} to the wave signal cos2πfdt and the sine wave signal sin2πfdt. It can be seen that the signal simulates the canceling sound actually detected at the position of the microphone 8. The canceling sound actually detected by the microphone 8 is a signal detected by the canceling sound generated from the speaker 6 based on the control signal Sc passing through the real space sound field in the passenger compartment 4.

  A constant for changing the magnitude of the simulated canceling sound signal Sk is the stability compensation coefficient α (0 ≦ α <1).

  Regarding the property of the stabilization signal αSk obtained by multiplying the simulated canceling sound signal Sk by the stability compensation coefficient α, first, consider the case of α = 0. At this time, when the audio signal Sa (musical sound) becomes large at the control frequency fd, the ratio of drumming noise received by the microphone 8 becomes relatively small. Then, the ANC unit 18d becomes unstable. In this case, when the stability compensation coefficient α is increased from 0, the ratio of the stabilization signal α · Sk in the error signal e is increased, so that the stability at the control frequency fd is improved. However, if the stability compensation coefficient α is too large (too close to a value of 1), the response to changes in the magnitude of drumming noise received by the microphone 8 becomes dull, and noise control becomes meaningless. Therefore, by setting the stability compensation coefficient α that increases as the magnitude P of the audio signal increases in the stability compensation coefficient multiplier 98, it is possible to perform constant drumming noise control even when the tone is loud. become able to.

  It should be noted that the update equation of the filter coefficient A when there is no stability compensation is the following equation (2) with reference to the above equation (1) when the control frequency fd is 42 [Hz], It can be seen that the following equation (3) is obtained when there is stability compensation.

A (n + 1) = A (n) −μe (n) _{42 Hz} r (n) _{42 Hz} (2)
A (n + 1) = A (n)
−μ {e (n) _{42 Hz} r (n) _{42 Hz} + αr (n) _{42 Hz} } (3)

  In the control parameter switching table 102 in FIG. 7, the control parameter (μ, α) in the halftone dot region is (μ1 / 16, 4 × α1), and the step size parameter μ is 1/16 of the normal control. The stabilization compensation coefficient α1 is four times that of normal control. Further, in the control parameter switching table 102 of FIG. 7, the white area is an area where the noise control is faded out and stopped.

  Therefore, in the flowchart of FIG. 8, it is determined whether or not the vehicle speed V is higher than the high speed Vh (Vh = 200 [km / h]) in step S11, and if it is higher than the high speed Vh, the noise control is stopped in step S12. . In FIG. 7, the vertical axis is a logarithmic axis.

  If the vehicle speed V is less than the high speed Vh in step S11, it is determined in step S13 whether the vehicle speed V is equal to or higher than the medium speed Vm (Vm = 100 [km / h]). In S14, it is determined whether or not the volume P of the audio signal is less than or equal to the sound Pl, and if it is less than or equal to the sound P1, control is performed in the hatching area in the control parameter switching table 102. μ, α) is switched to (μ1 / 4, 2 × α1), and drumming control is performed in step S16.

  If the audio signal loudness P is greater than the small sound Pl in step S14, it is determined in step S17 whether the audio signal loudness P is less than the loud sound Ph. In the control parameter switching table 102, since control is performed in the halftone dot region, the control parameter (μ, α) is switched to (μ1 / 16, 4 × α1), and drumming control is performed in step S16. Note that, in step S17, when the magnitude P of the audio signal exceeds the loud sound Ph, the noise control is stopped in step S12.

  If the vehicle speed V is less than the high speed Vh in step S11 and the vehicle speed V is less than the medium speed Vm (Vm = 100 [km / h]) in step S13, the vehicle speed V is further greater than or equal to the low speed Vl in step S19. If it is equal to or lower than the low speed Vl (Vl <V <Vm), it is determined in step S20 whether the magnitude P of the audio signal is equal to or lower than the small sound Pl.

  If the pitch is less than P1, the control parameter switching table 102 is controlled in the double hatched area, so the control parameter (μ, α) is switched to (μ1, α1) in step S21, and normal in step S16. Perform drumming control.

  When the magnitude P of the audio signal is larger than the small sound Pl in step S20, it is further determined in step S22 whether the magnitude P of the audio signal is equal to or lower than the medium sound Pm. (Pl <P <Pm), the control parameters (μ, α) are switched to (μ1 / 4, 2 × α) in step S23, and drumming control is performed in step S16.

  On the other hand, when the magnitude P of the audio signal is larger than the medium sound Pm in step S22 (Pm <P), it is further determined in step S24 whether or not the magnitude P of the audio signal is less than the loud sound Ph. If it is less than the loud sound Ph (Pm <P <Ph), the control parameter (μ, α) is switched to (μ1 / 16, 4 × α1) in step S25, and drumming control is performed in step S16. If the magnitude P of the audio signal exceeds the loud sound Ph in step S24, the noise control is stopped in step S12.

  As described above, according to the vehicle acoustic control device 40B of the example of FIG. 5, basically the vehicle speed V and the audio signal are the same as the vehicle acoustic control devices 40 and 40A of the example of FIG. 1 and FIG. The amplitude of the control signal Sc is adjusted according to the magnitude P of the control signal, and further, the step size parameter μ and the stabilization, which are control parameters related to the stability of the control, according to the vehicle speed V and the magnitude P of the audio signal Since the compensation coefficient α is adjusted, the area where the active noise control unit 18d operates stably can be expanded.

1 is a block diagram illustrating a configuration of a vehicle acoustic control device to which an active noise control device according to an embodiment of the present invention is applied. 2A to 2C are explanatory diagrams of audio signal dependent gain characteristics set in the vehicle speed dependent control signal adjusting unit and the audio signal dependent control signal adjusting unit. It is a flowchart with which operation | movement description of the active noise control apparatus which concerns on one Embodiment is provided. It is a block diagram which shows the structure of the acoustic control apparatus for vehicles to which the active type noise control apparatus which concerns on other embodiment was applied. It is a block diagram which shows the structure of the acoustic control apparatus for vehicles to which the active noise control apparatus which concerns on other embodiment was applied. FIG. 6 is a block diagram illustrating a configuration of an active noise control unit in FIG. 5. FIG. 6 is an explanatory diagram of switching between a step size parameter and a stabilization compensation coefficient for explaining the operation in the example of FIG. 6 is a flowchart for explaining the operation of the example in FIG. 5. FIG. 9A is an explanatory diagram of the sensitivity function when the step size parameter is large, and FIG. 9B is an explanatory diagram of the sensitivity function when the step size parameter is small. It is a block diagram which shows the structure of the active noise control apparatus which concerns on a prior art. It is a block diagram which shows the structure of the acoustic control apparatus for vehicles which concerns on a prior art.

Explanation of symbols

6 ... Speaker 8 ... Microphone 10, 54 ... Amplifier 12, 12a ... Active noise controller 14 ... A / D converter 16 ... D / A converter 18, 18a, 18b, 18c, 18d ... Active noise control unit ( ANC unit)
20, 20a, 20b ... audio units 22, 40, 40A, 40B ... vehicle acoustic control device 24 ... adder 26 ... synthesis unit 42 ... vehicle speed sensor 44 ... size detector (audio signal detection means)
45 ... Audio volume 50 ... Control signal amplitude adjusting unit 51 ... Vehicle speed dependent control signal adjusting unit (vehicle speed dependent control signal adjusting means)
52. Audio signal dependent control signal adjusting unit (audio signal dependent control signal adjusting means)
102 ... Control parameter switching table

Claims (7)

A mixed sound of a vehicle interior noise, a musical sound from a sound output means based on an audio signal, and a canceling sound of the vehicle interior noise from the sound output means based on a control signal is detected as an error signal by a sound detection means, In an active noise control device that outputs the control signal for generating the canceling sound based on an error signal to the sound output means,
Audio signal detection means for detecting the magnitude of the audio signal;
Vehicle speed detection means for detecting the vehicle speed;
Audio signal dependent control signal adjusting means for adjusting the amplitude of the control signal according to the detected magnitude of the audio signal;
An active noise control apparatus comprising: a vehicle speed dependent control signal adjusting unit that adjusts an amplitude of the control signal in accordance with the detected vehicle speed. The active noise control device according to claim 1,
The active noise control device, wherein the vehicle speed dependent control signal adjusting means adjusts the amplitude of the control signal to a zero value when the vehicle speed is zero. The active noise control device according to claim 1,
The active noise control apparatus, wherein the audio signal dependent control signal adjusting means adjusts the amplitude of the control signal to be a zero value when the size of the audio signal is equal to or larger than a predetermined size. The active noise control device according to claim 1,
The vehicle speed dependent control signal adjustment means adjusts the amplitude of the control signal to zero when the vehicle speed is zero, and adjusts the amplitude of the control signal when the vehicle speed increases from zero to a predetermined vehicle speed. Adjust to increase from zero value to reference amplitude value as vehicle speed increases,
The audio signal dependent control signal adjusting means adjusts the amplitude of the control signal to be a zero value when the size of the audio signal is equal to or larger than a predetermined size, and the size of the audio signal is set to the predetermined value. An active noise control apparatus, wherein when the amplitude decreases from zero to zero, the amplitude of the control signal is adjusted so as to increase from a zero value to a reference amplitude value according to a decrease in the size of the audio signal. The active noise control device according to claim 1,
Furthermore, the control parameter regarding the stability of control is adjusted according to the magnitude | size of the said audio signal, or the said vehicle speed. The active type noise control apparatus characterized by the above-mentioned. The active noise control device according to claim 5,
The active noise control apparatus, wherein the control parameter is a step size parameter. The active noise control device according to claim 5,
The active noise control apparatus, wherein the control parameter is a stability compensation coefficient.

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