JP2003027916A - Active noise reduction device - Google Patents

Abstract

(57) [Summary] In an active noise reduction device that actively reduces engine muffled sound caused by engine rotation, power is supplied to power amplification means even in a rotation speed region where noise reduction is not required. In addition, there is a problem in consuming wasteful power and reliability in continuous use. SOLUTION: When detecting a first rotation speed or more lower than a second rotation speed which requires noise reduction, power amplification means 102 is provided.
Power is supplied to the power amplification unit 102, and when the second rotation speed or more is detected, a compensation signal is input to the power amplification unit 102 to perform a silencing operation. An active noise reduction device that is not supplied and saves power and improves reliability can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces a so-called engine muffled sound having an unpleasant muffled feeling generated in a vehicle compartment due to engine rotation by interfering a compensation signal having an antiphase equal amplitude with the muffled sound. Regarding active noise reduction device,
Especially in the present invention, the noise is reduced by supplying the power of the power amplifier only in the region where a muffled sound accompanied by discomfort is generated,
At other times, stop the power supply to the power amplifier,
It is an object of the present invention to realize an active noise reduction device that reduces the overall power consumption.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 5-257481 proposes a device for generating and actively reducing so-called engine muffled noise due to engine rotation and an interference wave of opposite phase and equal amplitude.

FIG. 7 shows a block diagram of the apparatus proposed above. The operation of this device will be briefly described here. An error from a microphone 705 that detects an error component after noise and a sound wave interfere with a reference signal of a predetermined frequency based on a rotation signal synchronized with the crankshaft rotation of an engine. The reference signal is filtered so as to minimize the sound pressure signal and input to an adaptive filter 701 that adaptively generates a sound elimination signal to obtain a silence signal. The above-mentioned part is a well-known method which has been proposed as a conventional active noise control device, but in Japanese Patent Laid-Open No. 5-257481, the cutoff control circuit 70 for suppressing the sound wave elimination signal from the adaptive filter 701 is disclosed.
It is characterized in that the cutoff device 703 controls the input to the power amplifier 704 based on the judgment of No. 2. The cutoff control circuit 702 judges that the cutoff device 7 has a crankshaft rotation speed other than a preset control rotation speed.
It has been proposed to block the input of the sound wave elimination signal to the power amplifier 704 by 03.

[0004]

In the above-mentioned method, particularly in the engine rotation region where noise is a problem, the noise is effectively reduced by supplying the noise canceller from the active noise reducer to the power amplifier and generating the noise canceller from the speaker. It is practically valuable because it is possible to prevent the generation of noise other than the control target sound by reducing the noise reduction signal and not supplying the silence signal to the power amplifier in other rotation speed regions. However, the power amplifier used here only cuts off the input, constantly supplies power, and consumes a certain amount of power, although it does not generate an output for control. . Assuming that this power amplifier is of a 20 W class for audio, for example, it consumes about 1 W of power even when there is no signal, which is very wasteful.
Also, in order to muffle sound in a specific engine rotation region of the vehicle, keeping the power amplifier energized at all times during traveling causes a long total operating time, which causes a problem in reliability.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is a power amplifying means for power-amplifying a noise and a compensating signal of antiphase equal sound pressure due to engine rotation. A speaker installed in a space to be silenced and converting the output from the power amplifying means into an erased sound; and a microphone installed in the space to be silenced and detecting the residual sound of the erased sound and noise as an error signal. An adaptive filter that inputs a noise reference signal and automatically changes a filter coefficient to eliminate the noise to form the compensation signal; and a filter of the adaptive filter that uses the error signal and the noise correction signal. Coefficient updating means for updating coefficients, and a transfer characteristic from the output of the adaptive filter to the input of the coefficient updating means for simulating the noise reference signal to form the correction signal. Initially equivalent simulated transfer characteristic correcting means and means for detecting engine speed are provided, and power is supplied to the power amplifying means to operate at a first speed or higher detected by the means for detecting engine speed. Let
When a second rotation speed or higher, which is higher than the first rotation speed, is detected, the compensation signal is output to perform a muffling operation, and the power supply to the power amplifier is stopped in a low rotation region where the muffling operation is not required to reduce power consumption. It has the effect of saving money.

According to a second aspect of the present invention, a power amplification means for power-amplifying a noise and a compensating signal of anti-phase equal sound pressure due to engine rotation, and a power amplification means installed in a space to be silenced are provided. A speaker that converts the output from the sound into an erasing sound, a microphone that is installed in the space to be silenced, and that detects the residual sound of the erasing sound and noise as an error signal,
An adaptive filter that inputs a noise reference signal and automatically changes a filter coefficient to eliminate the noise to form the compensation signal; and a filter coefficient of the adaptive filter that uses the error signal and the noise correction signal. Coefficient updating means for updating, and a simulated transfer characteristic correction for initializing the transfer characteristic of the noise from the output of the adaptive filter to the input of the coefficient updating means in order to form the correction signal. Means for detecting the engine speed and means for detecting the engine speed detected by the means for detecting the engine speed
Of the number of revolutions or more, the compensation signal is stopped to stop the silencing operation, and when the fourth number of revolutions greater than the third number of revolutions is detected, the power supply to the power amplifying means is stopped and the silencing operation is performed. This has the effect of stopping the power supply to the power amplifier and saving the power consumption in a high rotation range where no power supply is required.

According to a third aspect of the present invention, the power amplifying means for amplifying the power of the compensating signal of the noise and the antiphase equal sound pressure due to the rotation of the engine and the power amplifying means installed in the space to be silenced are provided. A speaker for converting the output from the power amplifying means into an erasing sound, a microphone installed in the space to be silenced for detecting the erasing sound and a residual sound of noise as an error signal, and a noise reference signal for inputting the noise. An adaptive filter for automatically changing the filter coefficient to eliminate the noise and forming the compensation signal; a coefficient updating unit for updating the filter coefficient of the adaptive filter with the correction signal of the error signal and the noise; In order to form a signal, a simulated transfer characteristic correction is performed to simulate the transfer characteristic from the output of the adaptive filter to the input of the coefficient updating means to initially equalize the noise reference signal. And a means for detecting the engine speed, and supplying power to the power amplifying means to operate the power amplifier at a first speed or higher detected by the means for detecting the engine speed. Second greater than number
When the number of revolutions is detected or more, the compensation signal is output to perform the silencing operation, and when the number of revolutions greater than the second revolution is detected, the output of the compensation signal is stopped and the silencing operation is stopped. However, when a fourth rotation speed or higher, which is higher than the third rotation speed, is detected, the power supply to the power amplification means is stopped, and the power supply to the power amplifier is stopped in the rotation region where the silencing operation is not required, thereby reducing power consumption. This has the effect of saving money.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the power amplifying means is shared with the power amplifier for audio reproduction. Power is supplied to the power amplifier regardless of engine rotation, and if audio is not being reproduced, whether or not power is supplied to the power amplification means is determined by the engine speed. This has the effect that the power consumption can be saved by sharing the power amplifier with the power amplifier and cutting off the power supply to the power amplifying means when the silencing operation is not required.

[0009]

1 is a block diagram of an active noise reduction device according to a first embodiment of the present invention. In FIG.
Reference numeral 101 denotes an adaptive filter that receives a reference signal of noise generated by engine rotation as an input and automatically changes a filter coefficient to eliminate noise and forms a compensation signal.
Reference numeral 102 is a power amplification means for power-amplifying the compensation signal from the adaptive filter 101, and 103 is a power amplification means 10.
It is a speaker that radiates the compensation signal from 2 as an erasing sound wave into the vehicle interior. Reference numeral 104 denotes a microphone installed in the passenger compartment for detecting a residual sound of noise and erased sound wave as an error signal, and 105 denotes a correction signal of the error signal from the microphone 104 and the reference signal of the noise, and a filter coefficient of the adaptive filter 101. Reference numeral 106 is a coefficient updating means for updating, and simulated transfer characteristic correcting means 106 receives the noise reference signal as an input and simulates the transfer characteristic from the output of the adaptive filter 101 to the input of the coefficient updating means 105 and outputs it as a correction signal. is there.
Reference numeral 107 denotes an engine speed detecting means for detecting the engine speed, and reference numeral 108 receives the speed information from the engine speed detecting means 107, and supplies the power amplifier means 102 with a compensation signal and power supply from the adaptive filter 101. It is a shutoff device that shuts off. Reference numeral 109 indicates an engine. Figure 2
Is a configuration diagram of the breaking device 108, 201 is a compensation signal switch, 202 is a power supply switch,
Reference numeral 203 denotes an engine speed judgment circuit.

The operation of the first embodiment of the present invention will be described below.

The adaptive filter 101 receives a reference signal of noise generated by engine rotation as an input, and automatically changes a filter coefficient to eliminate noise and forms a compensation signal. The output of the adaptive filter 101 is the power amplification means 10
The power is amplified by 2 and emitted from the speaker 103 into the vehicle interior as an erasing sound wave that cancels noise. The residual sound after the interference of the noise and the sound wave erased from the speaker 103 is the microphone 10.
4 and is input to the coefficient updating means 105 as an error signal. On the other hand, the correction signal obtained by inputting the noise reference signal to the simulated transfer characteristic correcting means 106 is also the coefficient updating means 1.
05, the coefficient updating means 105 recursively updates the filter coefficient of the adaptive filter 101 based on an algorithm such as the well-known LMS method so that the residual sound after the interference between the noise and the erased sound wave becomes small. . This actively reduces the noise in the vehicle compartment due to the engine rotation. The description so far is similar to that proposed for many active noise control systems and is well known. The cutoff device 108 is installed between the adaptive filter 101 and the power amplification means 102, receives information from the engine speed detection means 107, and controls transmission of a compensation signal and power supply to the power amplification means 102. ing. The shutoff device 108 includes a compensation signal switch 201, an engine speed determination circuit 203, and a compensation signal switch 201.
ON / OFF of each switch of the power supply switch 202 is controlled.

FIG. 3 shows an operation state diagram in the first embodiment. When the rotational speed is equal to or higher than the first rotation speed, the power supply switch 202 is turned on, and power is supplied to the power amplification means 102. After that, when the second rotation speed or higher, which is higher than the first rotation speed, is detected, the compensation signal switch 201 is turned on, the compensation signal is supplied to the power amplification means, and the silencing operation is performed. As described above, at the second rotation speed or higher at which the silencing operation is required, the noise accompanying the engine rotation is actively reduced and at the first rotation speed or lower, which is lower than the second rotation speed at which the silencing operation is not required. Then, by cutting off the power supply to the power amplification means 102, it is possible to obtain an effect that unnecessary power consumption can be suppressed.

FIG. 4 shows an operation state diagram in the second embodiment. When the rotational speed is equal to or higher than the third rotation speed, the compensation signal switch 201 is turned off, the supply of the compensation signal to the power amplification means 102 is stopped, and the silencing operation is stopped. Then the third
When the fourth rotation speed or more higher than the rotation speed is detected, the power supply switch 202 is turned off and the power amplification means 10 is detected.
Power to 2 is cut off.

As described above, at the third rotation speed or lower at which the silencing operation is required, the noise accompanying the engine rotation is actively reduced, and the fourth rotation speed higher than the third rotation speed at which the silencing operation is not required. In the above range, it is possible to obtain an effect that unnecessary power consumption can be suppressed by cutting off the power supply to the power amplification means 102.

FIG. 5 shows an operation state diagram in the third embodiment. When the rotational speed is equal to or higher than the first rotation speed, the power supply switch 202 is turned on and the power is supplied to the power amplification means 102. After that, when the second rotation speed higher than the first rotation speed is detected, the compensation signal switch 201 is turned on, the compensation signal is supplied to the power amplifying means 102, and the silencing operation is performed. Further, when the rotation speed is equal to or higher than the third rotation speed, the compensation signal switch 201 is turned off, the supply of the compensation signal to the power amplification means 102 is stopped, and the silencing operation is stopped. When the power supply switch 202 is detected, the power supply switch 202 is turned off and the power supply to the power amplification means 102 is cut off.

As described above, at the second rotation speed or higher and the third rotation speed or lower at which the silencing operation is required, noise accompanying the engine rotation is actively reduced and at the second rotation speed at which the silencing operation is not required. Unnecessary power consumption is cut off by shutting off the power supply to the power amplification means 102 in a region of a low first rotation speed or lower and in a region of a fourth rotation speed or higher higher than the third rotation speed that does not require the silencing operation. The effect that it can be suppressed is obtained.

FIG. 6 shows a breaking device in which the power amplifying means in the fourth embodiment is shared with that for listening to music, and in the case of listening to music, the switch 60 for listening to music is always provided.
4 is turned on, and power is always supplied to the power amplification means regardless of the engine speed. By doing so, there is no inconvenience in the case of listening to music, and as described above, when not listening to music, unnecessary power is cut off by shutting off the power supply to the power amplification means 102 when the silencing operation is unnecessary. The effect is that consumption can be suppressed.

Although it has been described in the above description that the power supply to the power amplification means is cut off, the control function is provided in an IC for power amplification and is in a mode in which power is not substantially consumed. It goes without saying that shutting off the power supply to the same can exert the same effect.

[0019]

As described above, according to the active noise reducing apparatus of the present invention, the power is supplied to the power amplifying means consuming a large amount of power only in the engine rotation region where the noise reduction is required, and the noise is reduced. By cutting off the power of the power amplification means in the engine rotation region where reduction is unnecessary, it is possible to realize an active noise reduction device with low power consumption and excellent reliability.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an active noise reduction device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a blocking device used in the device.

FIG. 3 is an operation state diagram of the device.

FIG. 4 is an operation state diagram of the active noise reduction device according to the second embodiment of the present invention.

FIG. 5 is an operation state diagram of the active noise reduction device according to the third embodiment of the present invention.

FIG. 6 is a configuration diagram of a blocking device for an active noise reduction device according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a conventional active noise reduction device.

[Explanation of symbols]

101 Adaptive filter 102 power amplification means 103 speaker 104 microphone 105 coefficient updating means 106 simulated transfer characteristic correction means 107 engine speed detecting means 108 Breaker 109 engine 201 Compensation signal switch 202 Power supply switch 203 Engine speed judgment circuit 604 Music listening switch 701 Adaptive filter 702 Cutoff control circuit 703 Circuit breaker 704 power amplifier 705 microphone

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Claims (4)

[Claims] 1. A power amplification means for power-amplifying a compensating signal of noise and an antiphase equal sound pressure due to engine rotation, and a speaker installed in a space to be silenced and converting an output from the power amplification means into a cancellation sound. And a microphone installed in the space to be silenced, which detects the erasure on and the residual sound of noise as an error signal, and a reference signal of noise is input to automatically change the filter coefficient to eliminate the noise. An adaptive filter that forms the compensation signal, a coefficient updating unit that updates the filter coefficient of the adaptive filter with the error signal and the correction signal of the noise, and a reference signal of the noise to form the correction signal. , A simulated transfer characteristic correcting means for simulating the transfer characteristic from the output of the adaptive filter to the input of the coefficient updating means and initially equivalent, and means for detecting the engine speed. A power supply is supplied to the power amplification means to operate it at a first rotation speed or higher detected by the engine rotation speed detection means, and a second rotation speed or higher higher than the first rotation speed is detected. An active noise reduction device, characterized in that the compensation signal is output at times to perform a muffling operation. 2. A power amplifying means for power-amplifying a compensating signal of noise and an antiphase equal sound pressure caused by engine rotation, and a speaker installed in a space to be silenced and converting an output from the power amplifying means into a canceling sound. A microphone installed in the space to be silenced, which detects the noise to be eliminated and the residual noise of noise as an error signal, and a reference signal of noise is input to automatically change the filter coefficient to eliminate the noise. An adaptive filter that forms the compensation signal, a coefficient updating unit that updates the filter coefficient of the adaptive filter with the error signal and the correction signal of the noise, and a reference signal of the noise to form the correction signal. , A simulated transmission characteristic correction means for simulating the transmission characteristic from the output of the adaptive filter to the input of the coefficient updating means and initially equivalent, and means for detecting the engine speed. When the means for detecting the engine speed is equal to or higher than a third speed detected by the means, the compensation signal is stopped to stop the silencing operation, and when a fourth speed or higher, which is higher than the third speed, is detected. An active noise reduction device characterized in that power supply to the power amplification means is stopped. 3. A power amplification means for amplifying the power of a compensating signal of noise and anti-phase equal sound pressure caused by engine rotation, and a power amplification means installed in a space to be silenced. A speaker to be converted, a microphone installed in the space to be silenced, which detects the noise to be eliminated and residual noise noise as an error signal, and a noise reference signal is input to automatically filter coefficients to eliminate the noise. An adaptive filter that changes to form the compensation signal; a coefficient updating unit that updates the filter coefficient of the adaptive filter with the error signal and the correction signal of the noise; Simulated transfer characteristic correcting means for simulating the transfer characteristic of the reference signal from the output of the adaptive filter to the input of the coefficient updating means and initially equalizing it, and detecting the engine speed. Means for supplying power to the power amplification means to operate the power amplification means at a first speed or higher detected by the means for detecting the engine speed,
When the second rotation speed higher than the rotation speed is detected, the compensation signal is output to perform the silencing operation, and when the third rotation speed higher than the second rotation is detected, the compensation signal is output. Stop and stop the silencing operation,
The active noise reduction device is characterized in that the power supply to the power amplification means is stopped when a fourth rotation speed higher than the rotation speed is detected. 4. The power amplifying means is also used as a power amplifier for audio reproduction, and during audio reproduction, power is supplied to the power amplifier regardless of engine rotation and audio is not reproduced. The active noise reduction device according to any one of claims 1, 2 and 3, wherein whether or not power supply is possible is determined by the engine speed.