JP3538440B2 - Vehicle interior noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reduction device, and more particularly, to a noise reduction device for a vehicle interior generated when a vehicle is running.

[0002]

2. Description of the Related Art In recent years, improvement of vehicle interior noise has been promoted from the viewpoint of improving comfort, and the noise level has been decreasing year by year. However, a passive method (for example, addition of a soundproofing device, etc.).
The reduction of noise below a certain level is not an effective measure from the economical aspects such as cost and weight, and so noise reduction by an active method has been required. One of such active methods is to use the DSP (Digital Signal P
There is a technique using an adaptive signal technique based on a process (see FIG. 5). Here, as a typical example of the in-vehicle noise generated during the general running of the vehicle, there is periodic noise synchronized with the engine speed. This periodic noise is divided into the following engine noise and muffled sound.

The engine noise is composed of a complex periodic sound in which a harmonic component of the 0.5th component of the engine speed is used as a fundamental wave, and the sound quality changes depending on the composition ratio of each order component. Further, this waveform shows a waveform as if it were amplitude-modulated, and is a noise generated during acceleration and running. The muffled sound is caused by the secondary component of the engine rotation frequency,
It is a sound that is accompanied by a sense of oppression and gives a person discomfort. For example, when the engine speed is 6000 rpm, (6000 /
60) × 2 = 200 Hz standing wave is generated and the muffled sound in the vehicle interior. This muffled sound has a stationary waveform and is generated particularly when the vehicle is accelerated.

FIG. 5 is a block diagram showing a basic configuration of a conventional noise suppression device for suppressing such a muffled sound. In FIG. 5, assuming that the engine speed information as the excitation source is detected and used as a reference signal x, the noise transmission system 51 (the vehicle interior as an acoustic space) receives the muffled sound b based on the reference signal x.
(Booming noise) is output. The adaptive FIR filter 52 outputs a secondary sound c for canceling the muffled sound from the reference signal x. Further, the LMS algorithm 53 cancels the muffled sound b, which is the primary sound, with the secondary sound c from the adaptive FIR filter 52 (the square value of the error signal e between the two outputs from the microphone 54 is minimized. (Similarly) The coefficient of the adaptive FIR filter 52 is updated using the reference value x and the error signal e.

Here, in the adaptive FIR filter, since the number of taps also depends on the sampling frequency, the waveform of the muffled sound b approximates a sine wave. An FIR filter can be realized. Therefore, the noise suppression device that has been practically used conventionally has the basic configuration as described above,
Only the muffled sound was suppressed.

[0006]

However, the conventional noise suppression system having the above-described basic configuration is not compatible with a DSP (Digi
tal Signal Processor), a DSP dedicated to the noise suppression system is required, and the DSP cannot be shared with the audio system. In order to suppress engine noise, which is a complex synchronous sound, an adaptive FIR filter requires several hundred taps. Therefore, engine noise cannot be suppressed unless several DSP LSIs are used. However, since the DSP cannot be shared with the audio system, there is a disadvantage that the cost is high. Therefore, conventionally, only the muffled noise generated depending on the engine speed is performed, and the engine noise is not suppressed. was there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to realize a vehicle interior noise reduction device capable of suppressing engine noise (composite synchronous sound) and muffled noise generated depending on the engine speed. It is another object of the present invention to share a car audio system with a DSP to reduce costs.

[0008]

To achieve the above object, a vehicle interior noise reduction apparatus according to a first aspect of the present invention includes an audio signal reproduction system, and a digital signal processing apparatus for processing an audio signal from the audio signal reproduction system. And a sound reproducing unit for reproducing sound from an output of the digital signal processing unit, an engine speed detecting unit for detecting an engine speed of a car and outputting an engine speed detection signal in an on-vehicle sound reproducing device. Means, a vehicle speed signal detecting means for detecting a vehicle speed and outputting a vehicle speed detection signal, detecting a sound in the vehicle interior, detecting a noise signal remaining without being canceled from the detected sound signal, and outputting it as an erroneous signal A noise component detection unit that determines a running state of the vehicle based on the engine speed detection signal and the vehicle speed detection signal, and outputs a signal to the digital signal processing unit according to the running state;
Control to execute the "sound" suppression process, or
Whether to output a noise suppression periodic signal to minimize
And a control unit for selectively executing the control unit .

[0009] A second invention is the above-mentioned first invention, wherein:
The control unit controls and executes the digital signal processing unit.
The process of suppressing the muffled sound that is
When it is not live, it depends on the engine speed.
Sound "is suppressed, and the control unit detects the erroneous signal.
Before outputting the noise suppression periodic signal to minimize it
Except when the car is accelerating and not playing sound
"Muffled sound" also depending on the engine speed or
It is a process of suppressing "engine noise" .

In a third aspect based on the second aspect, the control section has a function comprising the following steps (1) to (5), and the control section includes the digital signal processing section.
Control if the car is accelerating and not playing sound
The "muffled sound" is suppressed, and the vehicle is accelerating and
When the control unit is not in the live state,
Perform processing to suppress "sound" or "engine noise"
It is characterized by the following. (1) It is determined whether or not the engine is operating based on the presence or absence of the engine speed detection signal. (2) At the time of engine operation, the traveling state of the vehicle is determined based on the vehicle speed detection signal to be one of the following (a), (b) or (c). (A) Stopping (b) Accelerating (c) Running at a constant speed (3) When the vehicle is stopped, the control unit suppresses the muffled sound that depends on the secondary component of the engine rotation frequency, and step (2) Return to (4) If the car is accelerating, it is determined whether or not sound is being reproduced. (4-1) If sound reproduction is in progress, sound reproduction is continued and the process returns to step (2). (4-2) If the sound is not being reproduced, the digital signal processor is made to suppress the muffled sound, and the process returns to step (2). (5) When the vehicle is traveling at a constant speed, the control unit suppresses engine noise depending on the engine rotation frequency, and returns to step (2).

In a fourth aspect based on the third aspect, the step (3) comprises the following operation. (3) When the car is stopped, it is determined whether or not the sound is being reproduced. (3-1) When sound is being reproduced, the noise component detection means
The detected sound signal in the vehicle compartment is input, and the time
The corrected output of the digital signal processing unit is subtracted. (3-2) The control unit suppresses a noise that depends on a secondary component of the engine speed, and returns to step (2).

[0012]

In the vehicle interior noise reduction device according to the first aspect of the present invention, the control unit controls the noise reduction processing on the reference signal corresponding to the engine speed and the running state of the vehicle.
The corresponding noise suppression processing is executed.

[0013] In the vehicle interior noise reduction device according to the second aspect of the present invention, the control unit instructs the DSP to generate a "muffled sound" and an engine noise.
The noise suppression processing of the sound part is executed.

As described above, according to the first and second aspects of the present invention, the contents of the noise suppression processing (muffled sound suppression, engine noise , etc.) depend on the running state of the vehicle (stopping, accelerating, running at constant speed).
Sound suppression) can be changed. The digital processing device for use in the digital processing of the O Dio signal (DS
P) can also be used for noise suppression.

[0015]

FIG. 1 is a block diagram showing the configuration of an embodiment of a vehicle interior noise reduction apparatus according to the present invention, in which a microcomputer and a DSP constituting an audio system are used in common. In FIG. 1, reference numeral 1 denotes an audio signal reproducing system, which includes a tuner 1-1 and a CD (compact disk) player 1-2. Reference numeral 2 denotes a microphone, which corresponds to room sound input means, 3 is an engine speed detector, 4 is a speed detector, 5 is a subtractor, and 6,7.
Is an A / D converter, 8 is a waveform shaping circuit, 9 is a DSP, 10
Is a microcomputer and corresponds to a control unit, 11 is a keyboard, 12 is a ROM (Read Only Memory), 13
Is a D / A converter, 14 is a time correction circuit, 15 is an LPF
(Low-pass filter), 16 and 17 are amplifiers, 18 and 1
9 is an adder, 20 and 21 are speakers. Further, the microphone 2, the subtractor 5, the A / D converter 7, and the time correction circuit 14 constitute an unsuppressed noise component detecting means.

In FIG. 1, a reproduced signal from the audio signal reproducing system 1 is input to the DSP 9 and the microcomputer 10 as a digital signal. The reproduction signal input to the DSP 9 is subjected to sound field reproduction processing by the DSP 9, converted to an analog signal by the D / A converter 13, output as a stereo signal via the amplifier 16, and passed through the adders 18 and 19 to the speaker. It is reproduced and output from 20, 21. Microphone 2
Is provided in the vehicle interior, detects noise (muffled sound and engine sound) generated in the vehicle interior, and inputs the noise to the subtracter 5. In addition, since an audio sound is simultaneously input to the microphone 2 while the audio system is operating, it is necessary to remove the audio sound in order to accurately detect the muffled sound and the engine sound. Therefore, the audio sound that has passed through the D / A converter 13 is time-corrected by the time correction circuit 14 and is canceled by subtraction by the subtracter 5. The time correction is for adjusting a time delay from the speakers 20 and 21 to the microphone 2.

Further, the noise detected by the microphone 2 is converted into a digital signal by the A / D converter 7 and input to the microcomputer 10 and the DSP 9. The engine speed detector 3 detects the rotation of the engine to generate a pulse, and inputs the pulse as a digital signal to the microcomputer 10 via the waveform shaping circuit 8.

The speed detector 4 detects the vehicle speed in order to determine the running state of the vehicle (stopping, accelerating, or running at a constant speed) from the vehicle speed, and inputs the detected vehicle speed to the microcomputer 10. It should be noted that the accelerator opening may be used instead of the speed as information for knowing the traveling state of the vehicle. In this case, a sensor that detects the degree of opening of the accelerator petal may be used instead of the speed detector 4. The microcomputer 10 is operated by a backup power supply (not shown), and controls and executes a noise suppression operation according to a running state of the vehicle by a noise suppression control unit (described later).

More specifically, a signal from the engine speed detector 3 is constantly monitored, and when the engine is operating, the running state of the vehicle is determined, when the vehicle is stopped, when the vehicle is accelerating, When the vehicle is traveling at a constant speed, it is determined which of the three states is present, and noise suppression control or the like is executed, and noise suppression necessary for noise suppression is performed so that the output from the microphone 2 is minimized. Output a periodic signal. Since the noise suppression periodic signal output from the microcomputer 10 is a square wave, the noise suppression periodic signal has a waveform approximated to a sine wave through the LPF 15, is output from the speakers 20 and 21 via the adders 18 and 19 via the amplifier 17, Cancels and suppresses indoor noise. The microcomputer 10 also controls the audio signal reproduction system 1 and the DSP 9 (transfers a muffled sound suppression processing execution program (muffled sound suppression means) or a DSP operation program to the DSP 9). The keyboard 11 inputs necessary instruction information such as DSP parameter input.

In the embodiment, a noise suppression control means for performing noise suppression control based on the present invention, a muffled sound suppression means for suppressing muffled sound, an engine sound suppression means for suppressing engine sound, and the like are realized as programs. The ROM 12 stores these programs and DSP operation programs. These programs are read by the microcomputer 10 as needed.

FIG. 2 is a flowchart showing a configuration example of the noise suppression control means according to the present invention. In this embodiment, the noise suppression control means is executed by the microcomputer 10 mounted on the audio system in the following steps. The operation of the first vehicle interior noise reduction device is controlled to suppress periodic vehicle interior noise.

[S1] The microcomputer 10 constantly monitors whether or not the engine of the car is operating. If the engine is not operating, the microcomputer 10 proceeds to steps S12 and S13 to enter a normal audio system operation mode. If the engine is operating, the process enters the noise suppression mode after step S2. The determination as to whether or not the engine is operating can be made based on the result of checking the presence or absence of a signal from the engine speed detector 3 input to the microcomputer 10. [S2] The running state of the car, "whether the car is stopped or running" is determined. If the car is stopped, the muffled sound suppression processing after step S3 is performed. If the car is running, step S6 is performed. Move on to The determination of the traveling state of the vehicle uses the result of checking the presence or absence of a vehicle speed signal by the speed detector 4 input to the microcomputer 10.

[S3] First, it is determined whether or not the audio system is operating. If the audio system is not operating, muffled sound suppression processing is executed in step S5. [S4] When the audio system is operating, the audio sound coming from the microphone 2 is removed. As described above, since the audio sound is also input to the microphone 2 while the audio system is operating, it is necessary to remove the audio sound in order to accurately detect the muffled sound and the engine sound. Therefore, the D / A converter 13
The audio sound that has passed through is time-corrected by the time correction circuit 14 and subtracted by the subtractor 5 to cancel out.

[S5] The muffled sound suppression processing is executed, and after the execution is completed, the flow returns to step S2. The muffled sound suppression processing focuses on the fact that the muffled sound is caused by the frequency of the secondary component due to the engine speed, and is a method for spatially canceling this secondary component. The muffled sound is basically a sine wave. Assuming that there is a sine wave for canceling this waveform internally, the phase and magnitude of the waveform are controlled so that the cancel signal is minimized (FIG. 3 shows an embodiment). The configuration of the muffled sound suppression processing is shown). [S6] It is determined whether the vehicle is accelerating. If the vehicle is not accelerating, the process proceeds to step S10. The determination as to whether or not the vehicle is accelerating can be made by calculating the magnitude of the speed before and after and the increment per unit time based on the vehicle speed signal from the speed detector 4 input to the microcomputer 10.

[S7] If the car is accelerating, it is determined whether or not the audio system is operating. If not, the process proceeds to step S9. [S8] When the car is accelerating and the audio system is operating, the muffled sound is not noticeable in the sense of hearing (the muffled sound is not perceived in the audio sound). The operation of the system is continued, and the process returns to step S6.

[S9] The microcomputer 10 has a D
The muffled sound suppression processing program is transferred to SP9
The muffled sound suppression processing is executed. After completion of the execution, the process returns to step S6. When the vehicle is accelerating, the number of revolutions of the engine is large, and the microcomputer 10 must operate in real time to execute the speed judgment and the like of the noise suppression control means. The muffled sound suppression processing is executed (in DSP9, the audio system execution program and the muffled sound suppression processing program cannot coexist.
The muffled sound suppression processing is performed).

[S10] It is determined whether the vehicle is traveling at a constant speed. If the vehicle is not running at a constant speed (for example, during deceleration), the process returns to step S6. [S11] If the vehicle is traveling at a constant speed, engine sound suppression processing is performed, and after execution is completed, the flow returns to step S10. When the car is traveling at a constant speed, the engine noise is large, and the muffled sound is included in the noise sound. Therefore, the microcomputer 10 obtains the engine speed from the input signal from the engine speed detector 3, Based on the frequency of the 0.5-order component of the rotation speed, a complex periodic sound is created by combining the first, second, third, fourth,. Then, the microphone 2 detects this engine sound, and the microcomputer 10 controls the composite periodic wave to be generated so that the signal level thereof is minimized (FIG. 4 shows the configuration of the engine sound suppression processing in the embodiment). [S12] If the engine is not operating in step S1, it is determined whether or not the audio system is operating. If the engine is operating, the operation of the audio system is continued and the process returns to step S1 and is not operating. In this case, the process simply returns to step S1.

FIG. 3 is a block diagram showing a configuration example of the muffled sound suppressing means. In the embodiment, the muffled sound suppressing means is realized by a program and stored in the ROM 12. Then, at the time of execution, the program is executed by the microcomputer 10 as a part (subprogram) of the noise suppression control means which is also realized as a program (see step S5).

[S31] The engine speed is read.
The microcomputer 10 calculates the engine speed based on a signal from the engine speed detector 3. [S32] The frequency of the secondary component corresponding to the engine speed is determined. In this frequency determination method, an approximate expression “frequency of secondary component Δf (engine speed)” is calculated as an equation (for example, (6000/60) × 2 = 200 Hz when engine speed = 6000 rpm) Alternatively, a frequency value corresponding to each division of the secondary component value may be calculated in advance and set as a "correspondence table of engine speed and frequency" in the muffled sound suppressing means (program).

[S33] Creation of a sine waveform based on the determined frequency of the secondary component The creation of a sine waveform can be easily obtained by using a well-known trigonometric function generation program (subroutine). [S34] Since the sine waveform signal is output as a square noise suppression periodic signal, the sine waveform signal is made to have a waveform approximating a sine wave (opposite phase to the muffled sound) through the LPF 15, and then the amplifier 1
The signal is output from the speakers 20 and 21 via the adders 18 and 19 via 7 to cancel and suppress noise in the vehicle interior.

[S35] With the error microphone 2,
The noise remaining without being canceled is detected as an error signal. [S36] It is determined whether the error signal is minimum (within an allowable range). If it is within the allowable range, the execution of the muffled sound suppressing means is terminated, and the flow proceeds to the execution of the noise suppression control means (return to step S1) (return from the sub program to the main program). [S37] If the error signal is not the minimum, the minimizing means (LMS program) is executed, and the process returns to step S34. The LMS program implements a well-known LMS algorithm as a program (not shown), and adjusts the phase of the sine wave output and the like so that the square value of the error signal is minimized.

FIG. 4 is a block diagram showing a configuration example of the engine sound suppressing means. In the embodiment, the engine sound suppressing means is realized by a program and stored in the ROM 12. Then, a part (sub-program) of the noise suppression control means which is also realized as a program at the time of execution
Is executed by the microcomputer 10 (see step S5 in FIG. 2).

[S41] The engine speed is read (similar to the case of FIG. 3). [S42] Primary, secondary and tertiary corresponding to the engine speed
Next, fourth order,... Determine the frequency of the component. This frequency determination method is to calculate the approximate expression "frequency of Nth-order component ≒ F (engine speed)" as an equation, or to calculate the frequency value corresponding to each Nth-order component value in advance and set the "engine What is necessary is just to set it in the engine sound suppression means (program) as a "correspondence table of rotation speed and N-order frequency".

[S43] Each sine waveform is generated based on the determined frequency of each frequency component, and a composite periodic sound is generated. The complex periodic sound is obtained by synthesizing the frequency of each frequency component. Note that the method of creating the sine waveform is the same as in FIG. [S44] Since the sine waveform signal is output as a square noise suppression periodic signal, the sine waveform signal is converted into a waveform approximating a sine wave (opposite phase to the engine sound) through the LPF 15 and then passed through the amplifier 17 through the adders 18 and 19 to the speaker 20, 21
And cancels out the noise in the passenger compartment.

[S45] With the error microphone 2,
The noise remaining without being canceled is detected as an error signal. [S46] It is determined whether the error signal is minimum (within an allowable range). If it is within the allowable range, the execution of the engine sound suppression means is terminated, and the flow proceeds to the execution of the noise suppression control means (return to step S1) (return from the sub program to the main program). [S47] If the error signal is not the minimum, the minimizing means (LMS program) is executed, and the process returns to the step S44.

[0036]

As described above, according to the vehicle interior noise reduction apparatus of the present invention, not only the muffled noise but also the engine noise can be suppressed. Further, since the DSP can be shared with the audio system, the cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a vehicle interior noise reduction device according to the present invention.

FIG. 2 is a flowchart illustrating a configuration example of a noise suppression control unit based on the present invention.

FIG. 3 is a block diagram illustrating a configuration example of a muffled sound suppressing unit.

FIG. 4 is a block chart illustrating a configuration example of an engine sound suppressing unit.

FIG. 5 is a block diagram showing a basic configuration of a conventional noise suppression device.

[Explanation of symbols]

1 Audio signal playback system 2 Microphone (vehicle interior sound input means) 3. Engine speed detector (engine speed detector) 4 Speed detector (speed detection means) 5 Subtractor 8 Waveform shaping circuit 9 DSP (digital signal processing unit) 10. Microcomputer (control unit) 20, 21 speaker (sound reproduction unit)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03G 3/32 B60R 11/02 G10K 11/178 H03H 21/00

Claims (4)

(57) [Claims] 1. An on-vehicle vehicle having an audio signal reproduction system, a digital signal processing unit for processing an audio signal from the audio signal reproduction system, and an audio reproduction unit for reproducing sound from an output of the digital signal processing unit. In the sound reproducing device, an engine speed detecting means for detecting an engine speed of the car and outputting an engine speed detection signal; a vehicle speed signal detecting means for detecting a vehicle speed and outputting a vehicle speed detection signal; A noise component detecting means for detecting a noise signal remaining without being canceled from the detected sound signal and outputting it as an erroneous signal; anda running state of the vehicle based on the engine speed detection signal and the vehicle speed detection signal. Judgment and according to the running state,
Let the digital signal processor perform "muffled sound" suppression processing
Noise control to minimize the false signal.
Where to select whether to output the pressure cycle signal
And a control unit . 2. The control section controls the digital signal processing section.
Car accelerates the suppression process of "muffled sound" to be controlled and executed
Depends on the engine speed when running and not playing sound
This is a process of suppressing the "muffled sound",
A noise suppression periodic signal for minimizing the erroneous signal is output.
Force when the car is accelerating and not playing sound
In other cases, it depends on the engine speed.
Processing to suppress "sound" or "engine noise".
If, interior noise reduction device according to claim 1, wherein. 3. The vehicle interior noise reduction device according to claim 2, wherein the control unit has a function including the following steps (1) to (5), and the control unit controls the digital signal processing unit.
If the car is accelerating and not playing sound,
Suppresses the "muffled sound" and reproduces sound while the car is accelerating
If the control unit is not in the "
Perform processing to suppress "sound" or "engine noise"
It, interior noise reduction apparatus according to claim. (1) It is determined whether or not the engine is operating based on the presence or absence of the engine speed detection signal. (2) At the time of engine operation, the traveling state of the vehicle is determined based on the vehicle speed detection signal to be one of the following (a), (b) or (c). (A) Stopping (b) Accelerating (c) Running at a constant speed (3) When the vehicle is stopped, the control unit suppresses the muffled sound that depends on the secondary component of the engine rotation frequency, and step (2) Return to (4) If the car is accelerating, it is determined whether or not sound is being reproduced. (4-1) If sound reproduction is in progress, sound reproduction is continued and the process returns to step (2). (4-2) If the sound is not being reproduced, the digital signal processor is made to suppress the muffled sound, and the process returns to step (2). (5) When the vehicle is traveling at a constant speed, the control unit suppresses engine noise depending on the engine rotation frequency, and returns to step (2). 4. The vehicle interior noise reduction device according to claim 3, wherein step (3) further comprises the following operation. (3) When the car is stopped, it is determined whether or not the sound is being reproduced. (3-1) When sound is being reproduced, the noise component detection means
The detected sound signal in the vehicle compartment is input, and the time
The corrected output of the digital signal processing unit is subtracted. (3-2) The control unit suppresses a noise that depends on a secondary component of the engine speed, and returns to step (2).