JPH04308899A - Adaptive active sound elimination system for sound in car - Google Patents

Abstract

PURPOSE:To operate the system in stable operation after control starts by controlling sound elimination in consideration of characteristics of a sound elimination transmission system. CONSTITUTION:The characteristics of the sound elimination transmission system including a transmission system from a secondary sound source 3 to a control point in the car cabin 200 are measured previously and measured characteristic information on the sound elimination transmission system is used as correction information for a reference signal detected by a reference signal detecting means 1 to control the sound elimination by a control means 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive active muffling system for vehicle interior sounds. In general, interior muffled noise of 200 Hz or less, which has a large effect on passenger noise among vehicle cabin noises, is dominated by panel vibration radiated sound caused by engine rotational vibration, so the countermeasure is to improve the structure of the vehicle body. , which is an important issue related to strength issues.

0002

2. Description of the Related Art Conventionally, various proposals have been made to reduce such indoor noise. For example, in the device described in Japanese Patent Application Laid-Open No. 60-143157, sound inside the car is recorded using a microphone (hereinafter sometimes abbreviated as microphone).
The system collects sound, filters it with an appropriate filter, and generates a mute signal from the speaker based on the result.

[0003] In addition, Japanese Patent Application Laid-Open No. 63-315
The techniques described in Japanese Patent Laid-open No. 346, the technique described in Japanese Patent Application Laid-Open No. 2-158296, the technique described in Japanese Patent Application Laid-Open No. 2-218296, etc. have been proposed.

0004

[Problems to be Solved by the Invention] However, since none of these conventional means adaptively identifies the system, there is a problem in that accurate silencing control cannot be performed.

[0005] Therefore, it has been considered to use an adaptive filter to output a sound having an equal amplitude and an opposite phase to the noise inside the vehicle from a secondary sound source so that the signal at the control point in the vehicle is minimized. However, simply using an adaptive filter causes the problem that the system becomes unstable after control starts because the characteristics of the silencing transmission system, including the transmission system from the secondary sound source to the control point in the vehicle interior, are unknown. There is.

The present invention has been devised in view of the above-mentioned problems, and it is possible to carry out silencing control in consideration of the characteristics of the silencing transmission system, so that the system can operate stably after the control is started. The purpose of the present invention is to provide an adaptive active silencing method for vehicle interior sound.

[0007]

[Means for Solving the Problems] Therefore, the adaptive active silencing method for vehicle interior sound of the present invention includes a reference signal detection means for detecting a reference signal, and a control point for detecting a signal at a control point in the vehicle interior. It comprises a signal detection means and a secondary sound source that outputs a sound wave signal toward the interior of the vehicle, and a reference signal detected by the reference signal detection means and a control point signal detected by the control point signal detection means. In response to this, in order to control the sound wave signal emitted from the secondary sound source so that the control point signal is minimized,
In an adaptive active silencing system for vehicle interior sound, which is equipped with a control means using an adaptive filter, the characteristics of the silencing transmission system including the transmission system from the secondary sound source to the control point in the vehicle interior are measured in advance. Then, the measured characteristic information of the silencing transmission system is used as correction information for the reference signal detected by the reference signal detecting means to perform the silencing control by the control means (Claim 1). ).

Further, the reference signal detection means may be configured as an acceleration sensor that detects vibrations in the vicinity of a mount connecting the engine and the vehicle body (claim 2), and the control point signal detection means may be configured in the vehicle interior. (Claim 3)
). In this case, it is preferable that the microphone be provided in a portion of the headrest near the center of the vehicle interior (Claim 4).

Furthermore, the secondary sound source may be disposed at the rear end of the rear seat in the vehicle interior at a position where the trunk room can be used as a back cavity (claim 5).

Further, the control means is configured to perform the above-mentioned silencing control using an adaptive filter using an algorithm based on the least square error estimation method (claim 6).

[0011]Furthermore, an interface between the reference signal detection means, control point signal detection means, and secondary sound source and the control means, an arithmetic unit and a storage device constituting the control means, and an interface between the interface and the control means are provided. A power supply section for the above is arranged on a common board, the power supply section is surrounded by a lead partition wall for noise prevention, and the connection lines for the above-mentioned interface, arithmetic device and storage device are composed of optical fibers. (Claim 7).

[0012] Furthermore, it is preferable that the characteristics of the silencing transmission system be measured by outputting an M-sequence random sound from a secondary sound source and detecting this by the control point signal detection means (
Claim 8), furthermore, the reference signal detected by the reference signal detection means is filtered by a filter having characteristic information of the measured noise transmission system, and the control point detected by the control point signal detection means is filtered. The filter coefficients are updated based on the signal using an algorithm based on the least square error estimation method (claim 9).

[0013]

[Operation] In the above-mentioned adaptive active silencing method for vehicle interior sound of the present invention, the characteristics of the noise reduction transmission system including the transmission system from the secondary sound source to the control point in the vehicle interior are measured in advance. The characteristic information of the silencing transmission system is used as correction information for the reference signal detected by the reference signal detecting means to perform the silencing control by the control means.

For example, when measuring the characteristics of the silencing transmission system, the characteristics of the silencing transmission system are measured by outputting an M-sequence random sound from a secondary sound source and detecting this with the control point signal detection means. The reference signal detected by the reference signal detection means is filtered using a filter having characteristic information of the noise reduction transmission system measured in this way, and the reference signal detected by the control point signal detection means is combined with the control point signal detected by the control point signal detection means. The filter coefficients are updated from the point signals using an algorithm based on the least square error estimation method.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

(a) Description of the first embodiment FIGS. 1 to 19 show an adaptive active silencing method for vehicle interior sound as a first embodiment of the present invention, and FIG. 1 is a system block diagram thereof. 2 is a diagram explaining the layout for installing various parts, FIG. 3 is a block diagram showing details of the system control unit, FIG. 4 is a schematic plan view showing an example of mounting the system control unit on a board, and FIG. 5 is a diagram showing the shielding of the power supply section. 6 is a perspective view showing the state in which the control microphone is attached to the seat, FIG. 7 is a sectional view showing the state in which the control microphone is attached to the seat, FIG. 8 is an electric circuit diagram of the amplifier for the control microphone, 9 is a perspective view of the secondary sound source seen from inside the vehicle, FIG. 10 is a sectional view taken along the line X-X in FIG. 11, and FIG.
Figure 12 is a block diagram explaining the control algorithm of this method, Figure 13 is a flowchart explaining the control procedure of this method, and Figures 14 and 15 show the selected reference signal. Figure 16 is a diagram explaining the quality of the detection point, Figure 16 is a diagram explaining the quality of the control microphone installation position, Figure 17 is a diagram explaining the relationship between the filter update coefficient and maximum attenuation, and Figure 18 is the diagram explaining the relationship between the filter update coefficient and attenuation. A diagram explaining the relationship with time, and FIG. 19 is a diagram explaining the relationship between the number of filter taps and the amount of noise reduction.

Now, in this embodiment, as shown in FIGS. 1 and 2, an acceleration sensor 1 that detects vertical vibration in the vicinity of a roll mount 101 that connects a transverse engine 100 and a vehicle body detects a reference signal. A reference signal detecting means is provided to detect the reference signal.

[0018] In addition, as reference signal detection means, other means include longitudinal vibration of the center of the dash panel, longitudinal vibration of the engine head, longitudinal vibration of the vehicle body, vertical vibration of the tip of the vehicle body, vertical vibration of the front suspension, vertical vibration of the front floor, vertical vibration of the seat riser, and vertical vibration of the muffler hanger. Although it is possible to detect vertical vibrations in the center of the front roof rail, it is optimal to detect vertical vibrations near the roll mount 101 as in this embodiment (see FIGS. 14 and 15). here,
FIG. 14 shows the frequency characteristics of the noise level including all frequencies, and FIG. 15 shows the frequency characteristics of the noise level including the secondary frequency of the crank rotation. In each figure, the solid line indicates the case when this control is applied ( (with control), and the dotted line is the case without control, but in both figures, over all engine speeds, the effect with control is better than the case without control. roll mount 1
It can be said that it is better to detect vertical vibration near 01.

Further, control point signal detection means for detecting signals at control points (evaluation points) in the vehicle interior 200 is provided, and this control point signal detection means is shown in FIGS. As shown in FIG. 2, it is configured as a control microphone (for example, a simple conducer microphone) 2-1 provided on a headrest 201-1 of a driver's seat 201 in a vehicle interior 200. More specifically, this control microphone 2-1 is connected to the headrest 201-1.
It is provided through a rubber case 11 in a portion near the center of the vehicle compartment.

Note that the control microphone 2-1 is connected to the headrest 2.
If it is provided near the center of the vehicle compartment of 01-1, the effective area will be expanded as shown in FIG. This is because the influence of glass reflection etc. is small.

The control point signal detected by the control microphone 2-1 is amplified by a microphone amplifier 12-1 provided inside the seat back.

Here, as the electric circuit of the microphone amplifier 12-1, a known one as shown in FIG. 8 is used.

Furthermore, a sound wave signal (2
A speaker as a secondary sound source that outputs a secondary source signal (
Canceling speaker) 3 is provided, but in this case, the speaker 3 uses the trunk room 300 as a back cavity at the rear end of the rear seat 203 of the vehicle interior 200, as shown in FIGS. It is placed in a position where it can be used. That is, this speaker 3 is attached to the bulkhead (speaker mounting plywood) 14 on the back surface of the seat back of the rear seat 203 so that the vibration surface faces the opening that opens when the armrest 203-1 of the rear seat 203 is folded down. In addition, in FIGS. 10 and 11, the reference numeral 30
1 is a spare tire well.

By the way, the system control unit 13 is arranged inside the trunk room 3.

As shown in FIGS. 1 and 3, detection signals from the acceleration sensor 1 and the control microphone 2-1 are input to the system control unit 13, and the speaker amplifier 7 (FIG. 1) is input to the speaker 3. , 2)
A secondary source signal is outputted via.

This system control unit 13 includes a numerical arithmetic processor 40, a ROM 41, a RAM 42-
1. Digital signal processor (hereinafter referred to as DSP) 43-1, status control register (hereinafter referred to as SCR) 44, clock generator 45, low-pass filter 51, 52-1, 53, A/D converter 61, 6
2-1, a D/A converter 63, a timing generator 8, and a serial port 10, and these numerical calculation processors 40, ROM41, RAM42-1, and DSP43
-1, SCR44, A/D converter 61, 62-1, D/
The A converter 63 is connected via an optical fiber 15 with a photoelectric converter (O/E) and an electro-optical converter (E/O).

[0027] These numerical arithmetic processors 40
, ROM41, RAM42-1, DSP43-1, SC
R44 and the clock generator 45 constitute the main control section 4.

Here, the numerical calculation processor 40 is a DSP used for calculations for noise reduction control (active noise cancellation), and on the bus of this numerical calculation processor 40 are a ROM 41, a RAM 42-1, a DSP 43-1, S
It has a CR44 arrangement.

The ROM 41 stores characteristic information of the silencing transmission system [the transmission system from the speaker (secondary sound source) 3 to the control point (control microphone 2-1 installation position) in the vehicle interior 200, the speaker 3, the amplifiers 7, 12, etc. -1, frequency characteristics (transfer function) of the microphone 2-1], etc.

The RAM 42-1 stores a control program, the DSP 43-1 functions as a digital filter processor, and the SCR 44 stores a control program.
-1 and the numerical arithmetic processor 40.

The clock generator 45 generates an operating clock for the numerical arithmetic processor 40.

[0032] Low-pass filters 51, 52-1, 53,
A/D converters 61, 62-1, and D/A converter 63 are interfaces between acceleration sensor 1, control microphone 2-1, and speaker 3, and main control unit 4, and The analog signal is filtered by the low-pass filter 51 and then converted to a digital signal by the A/D converter 62-1, and the analog signal detected by the control microphone 2-1 is filtered by the low-pass filter 52-1. After that, the A/D converter 62-1 converts the secondary source signal into a digital signal, and the secondary source signal from the main controller 4 is converted into a digital signal.
After being converted into an analog signal by the A converter 63, it is filtered by the low-pass filter 51 and output to the speaker 3.

It should be noted that the low-pass filter used is one that cuts the band output above the maximum control frequency in order to prevent aliasing from the speaker 3.

The timing generator 8 includes an A/D converter 61
, 62-1, which generates a timing pulse that determines the input/output timing of the D/A converter 63, and is started/stopped by the numerical arithmetic processor 40 writing a command to the control register.

The serial port 10 is an external terminal for connection to an external computer.

Further, as shown in FIG. 4, the above A/D converters 61, 62-1, D/A converter 63, ROM 41,
A digital signal processing section such as RAM 42-1, DSP 40, 43-1, etc. and a power supply section (DC-DC converter) 16 for this digital signal processing section are arranged on a common substrate (board) 17. As shown in FIGS. 4 and 5, the power supply section 16 is surrounded by a partition wall 18 made of lead for noise prevention so that the digital signal processing section is not adversely affected by power supply noise. Note that the partition wall 18 has an opening for heat radiation at the upper part.

[0037] Since the power supply section 16 is surrounded by the lead partition wall 18 and each element is connected with the optical fiber 15 in this way, the digital signal processing section can perform mass communication in a short time without being adversely affected by power supply noise. This allows the board's performance (processing speed at the command line level) to be dramatically increased.

[0038] When the power is turned on, the control program is booted from the on-board ROM in this system, so that it can operate stand-alone.

By the way, in this embodiment, the main control section 4 of the system control unit 13 receives the reference signal detected by the acceleration sensor 1 and the control point signal detected by the control microphone 2-1, and controls the control point signal detected by the control microphone 2-1. It is configured as a control means using an adaptive filter in order to control the sound wave signal output from the speaker 3 so that the point signal becomes minimum (preferably 0). Further, in this example, the main control unit 4 performs the silencing control using an adaptive filter using an algorithm based on the least square error estimation method (LMS method).

Furthermore, in this embodiment, before performing the silencing control, the characteristics of the silencing transmission system including the transmission system from the speaker 3 to the control point in the vehicle interior 200 (control microphone 2-1 arrangement position) are determined in advance. Transfer function) D is measured in advance. This measurement is performed as follows. That is, by outputting an M-sequence random sound (white noise) from the speaker 3 and detecting it with the control microphone 2-1, the characteristic D of the silencing transmission system is measured.

Thereafter, the main controller 4 performs the noise reduction control using the measured characteristic information of the noise reduction transmission system as correction information for the reference signal detected by the acceleration sensor 1. That is, the reference signal detected by the acceleration sensor 1 is filtered by a filter having the measured characteristic information D' of the noise reduction transmission system, and from this and the control point signal detected by the control microphone 2-1, the LMS method is performed. The filter coefficients are updated using the following algorithm.

Next, the basic algorithm of this system will be explained in detail.

First, the silencing control (active noise control) of this system is Filtered-XL
This is done by an adaptive FIR filter using the MS algorithm. A basic block diagram is shown in FIG. In this block diagram, T is the characteristic of the vehicle body transmission system [including the acoustic transmission characteristic from the noise source (acceleration sensor 1 installation position) to the control point (control microphone 2-1 installation position)], W is the adaptive FIR filter, and D is the characteristic of the silencing transmission system [including the acoustic transmission characteristic from the secondary sound source (speaker 3) to the control point (control microphone 2-1 installation position)], D' is the model of D, and LMS is the LMS algorithm.

[0044] This system uses a reference signal X(t
) is input and convolved using FIR to obtain the output Y(t). Y (t) = ΣW (i)

Furthermore, when the present system outputs -Y(t), an error signal E at the control point is obtained due to the transfer characteristics of the sound field. E(t)=T(z)X(z)−D(z
)Y(z)...(2)

Furthermore, in order to maintain the causal relationship between the reference signal X(t) and the error signal E(t), d(t) is obtained by filtering X(t). d(t)=ΣD'(i)X(t-i)...(3)

[
[0047] Also regarding equation (3), i=0 to N-1
It is designed to take the sum of .

Then, the above error signals E(t) and d(t
), the filter coefficient W(i
) to update. In other words, Wn(i)=Wo(i)+kE(t)d(t-i)
(i=0~N-1)

・・・
(4)

Here, Wn(i) is the filter coefficient after update, Wo(i) is the filter coefficient before update, and k is the update coefficient.

[0050] As a result, the filter converges to the optimal filter that minimizes the error signal.

In addition, in FIGS. 17 and 18, the update coefficient value, maximum attenuation amount, and time until 20 dB attenuation are obtained for each representative frequency in order to understand the convergence and responsiveness of the system. From these figures, it can be seen that the convergence of the system has a limit value as the update coefficient increases, and as the frequency increases, the deterioration of the attenuation becomes more pronounced. It can also be seen that the responsiveness of the system becomes faster in proportion to the update coefficient, but tends to become slower in inverse proportion to the frequency. From these results, the upper limit of the update coefficient to be used is 9×1
0-13, so in this embodiment, for example, k=8x10-13 is used.

Furthermore, the error E is determined by the reference signal X, the filter coefficient W, and the noise reduction transmission system characteristic D. In other words, the LMS used to maintain the causal relationship between input data and errors.
It is necessary to consider the above D in the first stage of the algorithm. For this reason, this system uses the Filtered-X-LMS algorithm as its adaptive algorithm, and identifies D before starting adaptive control.

[0053] If this is done, W will converge to the Wiener filter after a sufficient period of time has passed after the start of control, and if this is ideal, then W=-(T/D).

In other words, W performs forward modeling of T and inverse modeling of D at the same time.

At this time, if the input noise signal is X, then
The output of T becomes TX, the output of W becomes (-TX/D), and the output of D becomes (-TX/D).D=-TX.

In other words, the additional points (
(see P), the error signal E becomes 0. Here, when T and D are expressed in polar coordinates, they are expressed as W=(T/D)exp[-j(θt-θd)].

Considering the actual model, the engine intake noise measured inside the vehicle is caused by the engine rotation (vibration), so it is always greater than the delay of T, and (θt−θd) shows a positive value. In other words, since W becomes a delay element, it is considered that it can be controlled.

Next, the control flow in this system is shown in FIG. 13. First, step S1
Initial settings are made for A/D, D/A conversion, control registers, and counters, and further, in step S2, characteristic information (initial impulse response) of the silencing transmission system that has been measured in advance is read.

Thereafter, a convolution operation is performed using an adaptive FIR filter, and coefficients are updated using the LMS method until the error signal becomes below a predetermined level, and an output signal is output to the speaker 3 (steps S3 to S6).

The relationship between the number of taps of the adaptive filter and the amount of noise reduction is shown in FIG. 19, and it can be seen from this that the number of taps and the amount of effect thereof have a substantially linear proportional relationship. In other words, increasing the number of taps increases the effect, but it is necessary to make a decision taking into account the performance, number, and cost of the DSP used, and for example, the number of taps is set to 256.

Furthermore, in the silencing control using an adaptive filter, it is necessary to perform control at a sampling frequency at which a waveform of at least four wavelengths exists between the number of taps used, so the sampling frequency is determined in accordance with this.

In this way, the characteristics of the noise reduction transmission system are measured in advance, and the measured characteristic information of the noise reduction transmission system is used as correction information for the reference signal detected by the acceleration sensor 1.
Since the system control unit 13 performs the silencing control, the system can be operated stably after the control is started.

(b) Description of Second Embodiment FIGS. 20 to 25 show an adaptive active silencing method for vehicle interior sound as a second embodiment of the present invention, and FIG. 20 explains the layout for mounting various parts. 21 is a block diagram showing details of the system control unit, FIG. 22 is a block diagram explaining silencing control for only the driver's seat, FIG. 23 is a block diagram illustrating silencing control for the front seats, and FIG. 24 is a block diagram illustrating silencing control for all seats. FIG. 25 is a block diagram explaining the silencing control and a flowchart explaining the control procedure of this method.
The same reference numerals as 19 indicate substantially similar parts.

Now, in the case of this second embodiment, there are four control points. That is, the portion of the headrest 201-1 in the driver's seat 201 closer to the center of the vehicle interior, the portion of the headrest 202-1 in the passenger seat 202 closer to the center of the vehicle interior, and the right and left headrests 20 in the rear seat 203.
Control microphones (for example, simple conducer microphones) 2-1, 2 are installed near the center of each vehicle compartment of 3-2 and 203-3.
-2, 2-3, and 2-4 are provided via a rubber case.

As a result, in this second embodiment, one of the silencing control for only the driver's seat (control mode 1), the silencing control for the front seats (control mode 2), and the silencing control for all seats (control mode 3) is selected. It is now possible to do so.

Therefore, the system control unit 1
3, as shown in FIG.
A secondary source signal is outputted via the following.

[0067] Then, the system control unit 1
3, the number of control points is increased by three compared to the first embodiment, and the number of RAM, DSP, low-pass filter, and A/D converter is increased by three each (numerals 42-2 to 42-4, 43).
-2~43-4, 52-2~52-4, 62-2~62
-4), and a selection switch 9 for selecting a control mode is also added. That is, this system control unit 13 includes a numerical calculation processor 40,R
OM41, RAM42-1 to 42-4, DSP43-1
~43-4, SCR44, clock generator 45, low-pass filter 51, 52-1 to 52-4, 53, A/D converter 61, 62-1 to 62-4, D/A converter 63, timing generation device 8, selection switch 9, serial port 1
0, these numerical calculation processors 40,
ROM41, RAM42-1 to 42-4, DSP43-
1 to 43-4, SCR44, A/D converter 61, 62-
1 to 62-4, the D/A converter 63 is a photoelectric converter (O/
E) and optical fiber 15 with electro-optical converter (E/O)
connected via.

Here, the ROM 41 stores four control points (control microphone 2) in the vehicle interior 200 from the speaker (secondary sound source) 3.
-1 to 2-4 installation positions) [Frequency characteristics (transfer functions) of speaker 3, amplifiers for speakers and control microphones, and microphones 2-1 to 2-4] It also stores information such as

The RAMs 42-1 to 42-4 are for storing control programs for executing each control mode.
SP43-1 to SP43-4 function as digital filter processors.

Low-pass filters 51, 52-1 to 52-
4, 53, A/D converter 61, 62-1 to 62-4, D
/A converter 63 includes acceleration sensor 1 and control microphone 2-1.
~ 2-4 and the interface between the speaker 3 and the main control unit 4, the analog signal detected by the acceleration sensor 1 is filtered by the low-pass filter 51, and then converted into a digital signal by the A/D converter 62-1. Along with being converted to
The analog signals detected by the control microphones 2-1 to 2-4 are filtered by low-pass filters 52-1 to 52-4, and then converted to digital signals by A/D converters 62-1 to 62-4. Furthermore, after the secondary source signal from the main control section 4 is converted into an analog signal by the D/A converter 63,
The signal is filtered by a low-pass filter 51 and output to the speaker 3.

[0071] Also in this case, the digital signal processing section and the power supply section (DC-
(DC converter) are arranged on a common board in the same manner as in Fig. 4, and the power supply section is also arranged in the same manner as in Figs. 4 and 5 to prevent the negative influence of power supply noise on the digital signal processing section. It is surrounded by a lead wall to prevent noise. Therefore, by surrounding the power supply section 16 with a lead partition wall and connecting each element with an optical fiber, the digital signal processing section can perform mass communication in a short time without being adversely affected by power supply noise. In this case as well, the performance of the board (processing speed at the command line level) increases dramatically.

By the way, in this second embodiment, when control mode 1 is selected, the main control section 4 of the system control unit 13 uses the reference signal detected by the acceleration sensor 1 and the signal detected by the control microphone 2-1. The sound wave signal emitted from the speaker 3 is controlled using an adaptive filter using the algorithm based on the LMS method described above so that the control point signal is minimized (preferably 0). to perform noise reduction control only for the driver's seat,
When control mode 2 is selected, the reference signal detected by the acceleration sensor 1 and the control point signals detected by the control microphones 2-1 and 2-1 are received, and the sum of these control point signals is the minimum ( Preferably, the sound wave signal emitted from the speaker 3 is controlled using an adaptive filter using the algorithm based on the LMS method described above to perform noise reduction control for the front seats, or control mode 3 is used. When selected, the reference signal detected by the acceleration sensor 1 and the control microphone 2-1
In response to the control point signals detected in steps 2-4 and 2-4, the above-mentioned LM
By using an adaptive filter using an algorithm based on the S method, it is possible to control the sound wave signals emitted from the speaker 3, thereby performing noise reduction control for all seats.

In either case, before performing the silencing control, the silencing transmission including the transmission system from the speaker 3 to the control point in the vehicle interior 200 (control microphones 2-1 to 2-4 arrangement positions) is performed in advance. System characteristics (transfer function) D, D1 to D4 (D1 and D
This measurement is performed by outputting an M-sequence random sound (white noise) from the speaker 3 and detecting it with the control microphones 2-1 to 2-4.
Characteristics D, D1 to D4 of each silencing transmission system are measured.

Thereafter, the measured characteristic information of the silencing transmission system is used as correction information for the reference signal detected by the acceleration sensor 1, and the main control section 4 performs silencing control. That is, the reference signal detected by the acceleration sensor 1 is filtered with a filter having characteristic information of the measured noise reduction transmission system, and this and the control microphone 2-
1; 2-1, 2-2; From the control point signals detected in 2-1 to 2-4, using an algorithm based on the LMS method,
The filter coefficients are updated.

[0075] Here, a block diagram for the silencing control for only the driver's seat, which is performed when control mode 1 is selected, is shown in Fig. 22, which is the same as the previous embodiment. , the explanation thereof will be omitted.

FIG. 23 shows a block diagram for the front seat silencing control that is performed when control mode 2 is selected; After the two error signals are A/D converted,
The sum is controlled to be the minimum value. In addition, in this case, D is used as a representative noise reduction transmission system.

Furthermore, a block diagram for the silencing control for all seats performed when control mode 3 is selected is shown below.
The result will be as shown in FIG. In this case, the data input/output is the same as in control mode 1, but the four error signals are
Multiple error filtered X (Multiple
Error Filtered-X) LMS
Use algorithms.

Of course, the basic algorithm according to this embodiment is the same as that explained in the previous embodiment, and furthermore, the L used to maintain the causal relationship between input data and errors.
The noise reduction transmission system characteristics D, D1 to D are used before the MS algorithm.
4, this D, D1 to D before the start of adaptive control.
The same is true for the identification of item 4.

The control flow in this system is shown in FIG. 25. That is, first, in step S1, initial settings are made for A/D, D/A conversion, control registers, and counters, and further, in step S2, one of control modes 1 to 3 is selected. After that, in step S3, the characteristic information (initial impulse response) of the silencing transmission system that has been measured in advance is read, and then the adaptive FIR
A convolution operation is performed using the filter, and the coefficients are updated using the LMS method until the error signal becomes below a predetermined level, and an output signal is output to the speaker 3 (step S4).
~S7).

As described above, in this embodiment as well, the characteristics of the silencing transmission system are measured in advance, and the measured characteristic information of the silencing transmission system is used as correction information for the reference signal detected by the acceleration sensor 1. Since the system control unit 13 performs the noise reduction control, the system can be operated stably after the control is started.

[0081] Furthermore, it is possible to arbitrarily select one of the following: silencing control for only the driver's seat, silencing control for the front seats, and silencing control for all seats, depending on the number of passengers in the vehicle. It also has the advantage of being able to implement appropriate silencing control.

(c) Others As a secondary sound source, in addition to arranging the speaker 3 at the rear end of the rear seat 203 of the vehicle interior 200 in a position where the trunk room 300 can be used as a back cavity as described above, As shown, the roof panel 40
0, or as shown in FIG. 26, a vibrator 20 may be provided on the floor panel 500, and these may be used as secondary sound sources.

[0083] Also, A/D converter, D/A converter, RO
Of course, the connection lines for M, RAM, DSP, etc. may be copper wires.

[0084]

[Effects of the Invention] As described in detail above, according to the adaptive active silencing method for vehicle interior sound of the present invention, the characteristics of the silencing transmission system are measured in advance, and information on the measured characteristics of the silencing transmission system is obtained. is used as correction information for the reference signal detected by the reference signal detection means to perform noise reduction control by the control means.
There is an advantage that the system can be operated stably after control is started.

Further, the reference signal detection means may be configured as an acceleration sensor that detects vibrations near the mount that connects the engine and the vehicle body (claim 2), or the control point signal detection means may be configured as an acceleration sensor that detects vibrations near the mount that connects the engine and the vehicle body. The microphone is provided in the upper headrest (Claim 3), and the microphone is further provided in a portion of the headrest near the center of the vehicle interior (Claim 4), and the secondary sound source is located at the rear end of the rear seat in the vehicle interior. Since the trunk room is arranged in a position where it can be used as a back cavity (claim 5), it is possible to effectively perform noise reduction control.

Furthermore, an interface between the reference signal detection means, control point signal detection means, and secondary sound source and the control means, an arithmetic unit and a storage device constituting the control means, and a power supply for the interface and the control means. The power supply section is arranged on a common board, the power supply section is surrounded by a lead partition wall for noise prevention, and the connection lines for the above-mentioned interface, arithmetic unit, and storage device are composed of optical fibers. Noise does not enter the signal processing section, and the signal processing section can perform large amounts of communication in a short time without being adversely affected by power supply noise, which dramatically increases the performance of the board (processing speed at the command line level). There is an advantage that the amount of energy increases (claim 7).

Furthermore, the characteristics of the silencing transmission system are measured by outputting M-sequence random sounds from the secondary sound source and detecting them by the control point signal detection means, so it is easy to measure the characteristics of the silencing transmission system. There is an advantage that it is possible (claim 8).

Furthermore, the control means performs the above-mentioned silencing control using an adaptive filter using an algorithm based on the least square error estimation method (claim 6), and further measures the reference signal detected by the reference signal detection means. The filter coefficients are updated using an algorithm based on the least square error estimation method from this filter and the control point signal detected by the control point signal detection means. (Claim 9) Therefore, there is an advantage that silencing control in accordance with real time can be realized.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a layout for mounting various parts in the first embodiment of the present invention.

FIG. 3 is a block diagram showing details of the system control unit according to the first embodiment of the present invention.

FIG. 4 is a schematic plan view showing an example of mounting the system control unit on a board according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a shielding structure of a power supply section.

FIG. 6 is a perspective view showing the control microphone attached to the seat.

FIG. 7 is a sectional view showing a state in which the control microphone is attached to the seat.

FIG. 8 is an electrical circuit diagram of a control microphone amplifier.

FIG. 9 is a perspective view of a secondary sound source viewed from inside the vehicle.

FIG. 10 is a sectional view taken along the line XX in FIG. 11;

FIG. 11 is a diagram of a secondary sound source viewed from inside the trunk room.

FIG. 12 is a block diagram illustrating a control algorithm of this system.

FIG. 13 is a flowchart illustrating the control procedure of the first embodiment of the present invention.

FIG. 14 is a diagram illustrating the quality of selected reference signal detection points.

FIG. 15 is a diagram illustrating the quality of selected reference signal detection points.

FIG. 16 is a diagram illustrating the quality of the attachment position of the control microphone.

FIG. 17 is a diagram illustrating the relationship between filter update coefficients and maximum attenuation.

FIG. 18 is a diagram illustrating the relationship between filter update coefficients and decay time.

FIG. 19 is a diagram illustrating the relationship between the number of filter taps and the amount of noise reduction.

FIG. 20 is a diagram illustrating a layout for attaching various parts in a second embodiment of the present invention.

FIG. 21 is a block diagram showing details of a system control unit according to a second embodiment of the present invention.

FIG. 22 is a block diagram illustrating silencing control for only the driver's seat.

FIG. 23 is a block diagram illustrating noise reduction control for the front seat.

FIG. 24 is a block diagram illustrating noise reduction control for all seats.

FIG. 25 is a flowchart illustrating the control procedure of the second embodiment of the present invention.

FIG. 26 is a diagram illustrating another example of a secondary sound source.

[Explanation of symbols]

1 Acceleration sensor (reference signal detection means) 2-1 to 2-
4 Control microphone (control point signal detection means) 3 Speaker (secondary sound source) 4 Main control section 7 Amplifier 8 Timing generator 9 Selection switch 10 Serial port 11 Rubber case 12-1 Microphone amplifier 13 System control unit 14 Partition wall 15 Optical fiber 16 Power supply section (DC-DC converter) 17 Substrate (board) 18 Noise prevention partition 19, 20 Vibrator 40 Numerical operation processor 41 ROM 42-1 to 42-4 RAM 43-1 to 43-4 DSP 44 SCR 45 Clock generator 51, 52-1 to 52-4, 53 Low-pass filter 61, 62-1 to 62-4 A/D converter 63 D
/A converter 100 Engine 101 Roll mount 200 Vehicle interior 201 Driver seat 201-1 Headrest 202 Passenger seat 202-1 Headrest 203 Rear seat 203-1 Armrest 203-2, 203-2 Headrest 300 Trunk room 301 Spare tire well 400 Roof panel 500 floor panel

Claims (9)

[Claims] Claim 1: A reference signal detection means for detecting a reference signal, a control point signal detection means for detecting a signal at a control point in a vehicle interior, and a secondary sound source for outputting a sound wave signal toward the interior of the vehicle. At the same time, in response to the reference signal detected by the reference signal detection means and the control point signal detected by the control point signal detection means, a sound wave is emitted from the secondary sound source so that the control point signal is minimized. In an adaptive active silencing system for vehicle interior sound, which includes a control means using an adaptive filter to control signals, a noise reduction transmission including a transmission system from the secondary sound source to a control point in the vehicle interior is performed in advance. Measuring the characteristics of the system and using the measured characteristic information of the silencing transmission system as correction information for the reference signal detected by the reference signal detecting means to perform the silencing control by the control means, Features an adaptive active silencing method for vehicle interior sound. 2. The reference signal detection means is configured as an acceleration sensor that detects vibrations in the vicinity of a mount connecting the engine and the vehicle body.
Adaptive active silencing method for vehicle interior sound. 3. The adaptive active muffling method for vehicle interior sound according to claim 1, wherein the control point signal detection means is configured as a microphone provided in a headrest above a seat in the vehicle interior. 4. The adaptive active muffling method for vehicle interior sound according to claim 3, wherein the microphone is provided in a portion of the headrest near the center of the vehicle interior. 5. Claim 1, wherein the secondary sound source is disposed at a rear end of the rear seat of the vehicle interior at a position where the trunk room can be used as a back cavity.
Adaptive active silencing method for vehicle interior sound. 6. The adaptive active silencing of vehicle interior sound according to claim 1, wherein the control means performs the silencing control using an adaptive filter using an algorithm based on a least square error estimation method. method. 7. An interface between the reference signal detection means, control point signal detection means, and secondary sound source and the control means, an arithmetic device and a storage device constituting the control means, and an interface between the interface and the control means. A power supply section for the above is arranged on a common board, and the power supply section is surrounded by a lead partition wall for noise prevention, and the connection lines for the above-mentioned interface, arithmetic unit, and storage device are constructed of optical fibers. 2. The adaptive active muffling method for vehicle interior sound according to claim 1. 8. A characteristic of the silencing transmission system is measured by outputting an M-sequence random sound from the secondary sound source and detecting it by the control point signal detection means. 1. The adaptive active silencing method for vehicle interior sound described in 1. 9. The reference signal detected by the reference signal detection means is filtered by a filter having characteristic information of the measured noise transmission system, and this and the control point signal detected by the control point signal detection means are filtered. 7. The adaptive active muffling method for vehicle interior sound according to claim 6, wherein the filter coefficients are updated using an algorithm based on the least square error estimation method.