JP6377412B2 - Active noise control system and active noise control method - Google Patents

Description

  The present invention can accurately perform noise reduction control by feedforward control without using an error microphone, and can also improve the processing speed and simplify the system and its method. About.

  Complaints from neighboring residents may be received due to noise generated from factories and construction sites. Of the machines used in factories, etc., sound generated from equipment such as fans and outdoor units and excavators such as backhoes protrudes from the other frequencies in the low frequency range (approximately 100 Hz or less). Has high frequency characteristics. Since fittings such as sashes have poor sound insulation performance in the low frequency region, if noise having a peak in the low frequency band propagates, it may affect residents as an unpleasant sound, which may be a problem.

  For active noise control using the sound interference phenomenon, for example, Patent Documents 1 to 3 are known. The “active noise control device” of Patent Document 1 performs a convolution operation of a transfer function of a specific digital filter on a transfer function of an FIR adaptive digital filter modified by a control algorithm.

  Patent Document 2 “Engine Noise Reduction Device for Construction Machinery” is a speaker that is detachably provided in the vicinity of the engine muffler of the construction machine, and a microphone for engine sound measurement is installed at the tip of the engine muffler sound output. A construction in which a control device electrically connected to the speaker and the microphone is provided in the construction machine, and a sound having a phase opposite to that of the noise from the engine muffler is output from the speaker to reduce the noise of the construction machine. It is a machine engine noise silencer.

  A “noise reduction device using a reducer” in Patent Document 3 emits a sound of a secondary sound source having a phase opposite to that of the original sound from a position close to the original sound to mute the original sound. The speaker for the secondary sound source A reducer is attached, and the speaker is moved backward from the position of the original sound, and the discharge port of the reducer is provided close to the original sound.

JP-A-7-64567 JP 2010-24876 A JP 2011-241745 A

  When the noise frequency is constant, the control sound to be interfered may be constant. However, when the noise of construction work machines is targeted, the frequency and sound pressure of the generated noise change depending on the engine softness and the fluctuation of work load. For this reason, the control sound also needs to change its frequency and sound pressure in accordance with the change in noise.

  Conventionally, when feedforward control is used for active noise control, an error microphone 101 for observing the control result has been used as shown in FIG. 5, for example. The active noise control system 100 in the illustrated example measures noise from a noise source 102 with a microphone 103, converts the measured noise into an antiphase control sound with an adaptive filter 104, and converts the converted control sound into a speaker. 105 is released.

  During this control, both the noise and the control sound are separately measured by the error microphone 101, and the frequency of the control sound, the sound pressure, and the noise are measured using the adaptive algorithm 106 for the sound measured by the error microphone 101. The phase difference is calculated and the coefficient of the adaptive filter 104 is adjusted so that a more appropriate control sound can be emitted. In the figure, 107 is a transfer function from the control speaker to the error microphone, and 108 is a transfer function from the noise source to the error microphone.

  By the way, when an error microphone is used in a place where there are complicated and various disturbances such as outdoors, there is a problem that it is difficult to control with high accuracy because a lot of noise is included in measured data. Regarding this problem, the error microphone for grasping the error signal has different errors due to disturbance for each sound receiving point, and considering that there are innumerable sound receiving points outdoors, this method is It is because it cannot be said that it is suitable for noise reduction outdoors.

  In addition, it takes time to process the data measured by the error microphone, the processing speed is slow, and the use of the error microphone complicates the system.

  The present invention was devised in view of the above-described conventional problems, and is capable of accurately performing noise reduction control by feedforward control without using an error microphone, improving processing speed, and system. It is an object of the present invention to provide an active noise control system and method capable of achieving simplification of the above.

  An active noise control system according to the present invention includes a measurement microphone that measures noise emitted from a noise source, a control controller that generates and outputs a control sound for reducing noise, and a control sound output from the control controller. A control speaker that emits noise, and the control controller transmits only a frequency component of a frequency band to be controlled in noise input from the measurement microphone, and transmits the bandpass filter. Based on the adaptive filter for estimating the dominant frequency to be controlled from the frequency components and the phase delay for each frequency of the control controller measured in advance, the phase delay with respect to the dominant frequency to be controlled input from the adaptive filter is phase-controlled in time control. Make a correction, and create a control sound with the opposite phase. Characterized in that it comprises a control signal arithmetic unit for outputting to use the speaker.

  The adaptive filter estimates a sound pressure of the dominant frequency to be controlled from a frequency component that has passed through the bandpass filter, and the control signal calculation unit is configured to measure each frequency of the measurement microphone and the control speaker that are measured in advance. On the basis of the gain characteristic, a control sound is generated by performing gain correction on the sound pressure with respect to the control target dominant frequency input from the adaptive filter.

  The phase correction for the phase lag performed by the control signal calculation unit is a step of obtaining the number N of data of one wavelength of the control object dominant frequency estimated by the adaptive filter, and the obtained waveform data of one wavelength from the control time. , A step of obtaining a phase delay of the controller with respect to the dominant frequency to be controlled estimated by the adaptive filter, a step of obtaining a data number Np corresponding to the phase delay, and a number of data of one wavelength A step of obtaining a data number Nx obtained by subtracting the data number Np corresponding to the phase delay from N, and a phase correction by removing the subtracted data number Nx from the stored waveform data of one wavelength, starting from the control time. It is characterized by doing.

  The control signal calculation unit, based on the phase delay for each frequency of the measurement microphone and the control speaker measured in advance in addition to the phase delay for each frequency of the control controller measured in advance, It is characterized in that phase correction is performed by time control for the phase delay with respect to the control target dominant frequency that is input.

  The control signal calculation unit is configured to output from the adaptive filter based on a pre-measured gain characteristic for each frequency of the control controller in addition to the pre-measured gain characteristic for each frequency of the measurement microphone and the control speaker. A control sound in which gain correction is performed for a sound pressure corresponding to the input control target dominant frequency is created.

  The active noise control method according to the present invention uses the above active noise control system, measures the noise emitted from the noise source with the measurement microphone, and then uses the bandpass filter to measure the noise from the measurement microphone. In the input noise, only the frequency component of the control target frequency band is transmitted, and then the control target prevailing frequency is estimated from the frequency component transmitted through the band pass filter by the adaptive filter. Based on the phase delay for each frequency of the control controller measured in advance, the control signal calculation unit performs phase correction by time control for the phase delay with respect to the control target dominant frequency input from the adaptive filter, and vice versa. Create a phase control sound and output it to the control speaker. Finally, the control speaker In, wherein the releasing control sound that is input from the control signal calculation unit.

  The adaptive filter estimates the control object dominant frequency from the frequency component transmitted through the band pass filter when estimating the control object dominant frequency, and the control signal calculation unit is input from the adaptive filter. The control input from the adaptive filter based on the gain characteristics for each frequency of the measurement microphone and the control speaker measured in advance when performing phase correction with respect to the phase delay with respect to the control target dominant frequency. A control sound is created by performing gain correction on the sound pressure with respect to the target dominant frequency.

  The phase correction for the phase lag performed by the control signal calculation unit is a step of obtaining the number N of data of one wavelength of the control object dominant frequency estimated by the adaptive filter, and the obtained waveform data of one wavelength from the control time. , A step of obtaining a phase delay of the controller with respect to the dominant frequency to be controlled estimated by the adaptive filter, a step of obtaining a data number Np corresponding to the phase delay, and a number of data of one wavelength A step of obtaining a data number Nx obtained by subtracting the data number Np corresponding to the phase delay from N, and a phase correction by removing the subtracted data number Nx from the stored waveform data of one wavelength, starting from the control time. It is characterized by doing.

  In the active noise control system and method according to the present invention, noise reduction control by feedforward control can be executed accurately without using an error microphone, and the processing speed can be improved and the system can be simplified. Can be achieved.

It is a block diagram which shows suitable one Embodiment of the active noise control system which concerns on this invention. It is explanatory drawing explaining a mode that the various characteristics of the control controller applied to FIG. 1, the measurement microphone, and the control speaker are measured beforehand. It is explanatory drawing explaining the correction method of the phase delay applied to the active noise control system which concerns on this invention, and its method. It is explanatory drawing explaining the operating condition in the field of the active noise control method by the active noise control system shown in FIG. It is a system block diagram for demonstrating a prior art.

  Hereinafter, a preferred embodiment of an active noise control system and an active noise control method according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an active noise control system according to the present embodiment. FIG. 2 is an explanatory diagram illustrating a state in which various characteristics of the control controller, the measurement microphone, and the control speaker applied to FIG. 1 are measured in advance. FIG. 3 is an explanatory diagram for explaining a method of correcting the phase delay. FIG. 4 is an explanatory diagram for explaining the operating state of the active noise control method by the active noise control system according to the present embodiment.

  As shown in FIG. 1, an active noise control system (hereinafter referred to as “ANSS”) 1 according to the present embodiment performs feedforward control, and measures noise Q emitted from a noise source 2. Microphone 3 (also referred to as a reference microphone), a microphone amplifier 4 that amplifies and outputs an input signal input from the control microphone 3, and an analog signal input from the microphone amplifier 4 is converted into a digital signal. The A / D converter 5 to be output, the control controller 6 that processes the digital signal input from the A / D converter 5 to generate and output the control sound for reducing the noise, and the control controller 6 D / A converter 7 that converts a digital signal input from the analog signal into an analog signal and outputs the signal, and amplifies and outputs the input signal input from the D / A converter 7 That the loudspeaker amplifier 8, an output signal output from the speaker amplifier 8, namely a control speaker 9 for emitting a control sound S output from the controller 6.

  A control sound S having a phase opposite to that of the noise Q is generated from the control speaker 9 with respect to the noise Q, whereby the noise Q is interfered and reduced. The control controller 6 includes a band pass filter 6a, an adaptive filter 6b, and a control signal calculation unit 6c.

  An object of the ANCS 1 according to the present embodiment is to select a noise having a frequency to be reduced from noises including various frequency components, and to reduce the noise having the frequency. In the present embodiment, the control controller 6 is configured to reduce the noise at the dominant frequency for the dominant frequency of the noise.

  When applying the ANCS 1 according to the present embodiment, the characteristics of the noise to be controlled are previously investigated by measurement or the like, and what frequency noise is to be subjected to mute control according to the noise characteristics. Considered in advance.

  For example, construction machinery has different engine operating conditions depending on idling, low load, medium load, and high load, and the characteristics of noise generated (excellent frequency and sound pressure) differ accordingly. Is determined in advance, and the ANCS 1 is set based on the obtained noise characteristics.

  In the present embodiment, a case where noise to be silenced, that is, a case where the control target frequency band is a low frequency band will be described. The same applies even if the frequency band to be controlled is the middle / high frequency band.

  For the microphone amplifier 4 and the speaker amplifier 8, the amplification amounts for the input signal from the measurement microphone 3 and the output signal from the D / A converter 7 are always constant.

  The A / D converter 5 converts an analog signal (sound wave) from the measurement microphone 3 into a digital signal (sound wave) at a sampling frequency set in advance based on the grasped noise characteristics. As for sampling of the frequency of noise, for example, one wavelength of sound is modeled by 64 divisions or more. As an example, when applied to noise countermeasures up to 400 Hz, the sampling frequency is set to 25.6 kHz. An output signal (digital signal) from the A / D converter 5 is input to the band pass filter 6 a of the controller 6.

  The band pass filter 6 a transmits only the sound in the control target frequency band in the noise input from the measurement microphone 3 via the microphone amplifier 4 and the A / D converter 5. That is, the band-pass filter 6a extracts a frequency component near the dominant frequency to be silenced at a preset cutoff frequency based on the grasped noise characteristics, and cuts other unnecessary frequency component signals. To do. Thereby, the high frequency component higher than the control target frequency band and the low frequency component lower than the control target frequency band included in the noise are removed, and the frequency component of the control target frequency band is extracted.

  In the band pass filter 6a, a phase difference occurs between the input signal and the output signal. This phase difference changes with changes in frequency. Even if the sound having the opposite phase of the signal transmitted through the band-pass filter 6a is emitted from the control speaker 9, it does not become the sound having the opposite phase of the noise. In this case, the noise reduction effect is small, and when the phase difference increases, the noise may be amplified. Therefore, for effective noise reduction, it is necessary to correct the phase of the output signal from the bandpass filter 6a.

  The band-pass filter 6a has a known phase characteristic for each frequency at the design stage. As will be described later, with respect to the bandpass filter 6a, the phase correction for the frequency (control target dominant frequency) estimated by the adaptive filter 6b is performed by the control signal calculation unit 6c by using the phase characteristics for each known frequency. Can do.

  The dominant frequency to be controlled is estimated by the adaptive filter 6b of the controller 6 from the low-frequency frequency component that has passed through the band-pass filter 6a. The adaptive filter 6b estimates the sound pressure of the control object dominant frequency from the frequency component that has passed through the bandpass filter 6a.

  As is well known, the adaptive filter 6b performs frequency analysis using a step size parameter. That is, the adaptive filter 6b estimates the dominant frequency, that is, the dominant frequency to be controlled at the time of noise reduction and its sound pressure in the time domain based on the step size parameter selected by an experiment such as simulation.

  The estimation of the dominant frequency in real time of the adaptive filter 6b used for the estimation of the frequency of the low frequency noise is important. By applying the adaptive filter 6b, the frequency of noise whose frequency fluctuates is estimated, and a noise reduction effect for such noise whose frequency fluctuates is ensured.

  A change in noise frequency and a change in maximum sound pressure over time are acquired from the noise obtained through the measurement microphone 3, and in the bandpass filter 6a, the frequency at which the input sound pressure is peak appears, and the bandpass filter 6a. The frequency and sound pressure of the noise to be controlled are estimated using the adaptive filter 6b.

  The control target dominant frequency and its sound pressure in real time estimated by the adaptive filter 6b are input to the control signal calculation unit 6c. Based on the phase delay of each frequency of the controller 6 measured in advance, the control signal calculation unit 6c corrects the phase delay with respect to the control target dominant frequency input from the adaptive filter 6b by time control and further reverses the phase. Create a control sound.

  Further, the control signal calculation unit 6c performs gain correction on the sound pressure with respect to the control target dominant frequency input from the adaptive filter 6b based on the gain characteristics for each frequency of the measurement microphone 3 and the control speaker 9 measured in advance. Create a control sound.

  Since the ANCS 1 according to the present embodiment does not use an error microphone as a premise, it cannot grasp the system phase error and sound pressure error in the ANCS 1 itself. The ANCS 1 according to the present embodiment is completed by devising a method for correcting a phase error and a sound pressure error of a system without an error microphone. The point lies in the function of the control signal calculation unit 6c.

  That is, using the estimation of the dominant frequency of noise performed in the adaptive filter 6b, the control signal calculation unit 6c performs processing such as specific phase correction based on the phase characteristics and gain characteristics inherent in the system, and The phase difference of the control sound to be created is corrected with respect to the frequency extracted by the pass filter 6a and estimated by the adaptive filter 6b, and then the control sound having the opposite phase is output.

  As described above, the band-pass filter 6a generates a phase difference between the input signal and the output signal. Therefore, the entire controller 6 including the bandpass filter 6a also causes a phase difference between the input signal and the output signal. In creating a control sound having an antiphase with respect to noise, it is necessary to perform phase correction by time control to match the phases of the noise and the control sound. For the control speaker 9 and the measurement microphone 3, it is necessary to consider that these gains change depending on the frequency.

  As preparation for phase correction, phase characteristics are measured in advance for the same ANCS 1 installed in the field, or the ANCS 1 installed in the field. FIG. 2 shows the state of measurement. The measurement is performed in the anechoic chamber 10 in order to avoid disturbance (noise) such as reflected sound in the room. The generated sound Q0 used as noise is a pure sound.

  As described above, the measurement target is the same as the ANCS 1 installed at the site. The distance D between the generated sound source 11 that emits the generated sound (pure sound) Q0 and the measurement microphone 3 and the distance D between the control speaker 9 that emits the control sound S and the laboratory microphone 12 are set equal. This distance D is preferably matched to the distance between the noise source 2 and the measurement microphone 3 when the ANCS 1 is installed on the site. In order to reduce the interference between the generated sound Q0 and the control sound S, the direction of the emitted sound is reversed, and the generated sound source 11 and the control speaker 9 are arranged with a sufficient distance.

  Briefly describing the phase difference due to the system configuration at the time of measurement, the sound pressure signal (pure sound) from the generated sound source Q0 is input from the measurement microphone 3 to the controller 6. In the controller 6, a control calculation is performed, and a control sound S based on the calculation result is emitted from the control speaker 9.

  It can be said that the phase difference of the controller 6, that is, the phase difference on the system, is the sum of the phase difference of the bandpass filter 6 a, the phase difference of the measurement microphone 3, and the phase difference of the control speaker 9. In order to generate the control sound having the opposite phase, a control signal in consideration of the phase difference of the controller 6 is required. The phase difference is the sum of the phase characteristics of the device system and the phase characteristics of the bandpass filter 6a. Adjustment of the controller 6 changes the bandpass filter 6a with respect to the grasped phase characteristics of the device system. Is called.

  At the time of measurement, the phase characteristics for each frequency of the entire ANCS 1 including the control controller 6 and the measurement microphone 3 and the control speaker 9 are measured for the entire frequency to be controlled that passes through the band pass filter 6a.

  Further, in order to perform gain correction when using the ANCS 1, the entire frequency to be controlled that passes through the band-pass filter 6 a is controlled for each frequency of the entire ANCS 1 including the control controller 6, and the measurement microphone 3 and the control speaker 9. Measure the gain characteristics.

  If necessary, the phase characteristics and gain characteristics of the microphone amplifier 4, the A / D converter 5, the D / A converter 7, and the speaker amplifier 8 may be taken into consideration.

  Thereby, the measured data of the phase characteristics and gain characteristics of the ANCS 1 measured for phase correction and gain correction are acquired and stored for each frequency in the storage area of the control signal calculation unit 6c.

  In other words, the controller 6 of the ANCS 1 according to this embodiment is not limited to the bandpass filter 6a or itself, but incorporates characteristics of the entire device such as gain and frequency characteristics of the measurement microphone 3 and the control speaker 9. Is the control controller 6.

  The control signal calculation unit 6c reads out the phase characteristics and gain characteristics of the ANCS 1 from the storage area, and executes phase correction by time control for the phase delay of the control target dominant frequency estimated by the adaptive filter 6b with respect to the actual noise.

The method of phase correction for the phase lag performed by the control signal calculation unit 6c is as follows (see FIG. 3). In the figure, the solid line is the phase characteristic (sound pressure change) of the controller 6, and the broken line is the phase characteristic (sound pressure change) of the control object dominant frequency estimated by the adaptive filter 6 b from the output of the bandpass filter 6 a, that is, True sound pressure. B is the control start time, M is the sound pressure value of the controller 6 at the control start time B, and R is the true sound pressure value at the control start time B.
(1) The number of data N of one wavelength (wave for one period; range from A to B) of the control target dominant frequency estimated by the adaptive filter 6b is obtained based on the control time increment.
(2) From the control start time B, the waveform data (waveform expressed by the number of data N) of the obtained one wavelength (one period) is stored.
(3) The phase delay φ (rad) of the controller 6 with respect to the dominant frequency to be controlled estimated by the adaptive filter 6b is obtained. It is obtained from the phase of the estimated frequency and the phase of the frequency acquired by the measurement in the anechoic chamber 10.
(4) The number of data Np corresponding to the phase delay is obtained. (Np = N × (φ / 2π))
(5) The number of data Nx is obtained by subtracting the number of data Np corresponding to the phase delay from the number of data N for one wavelength (for one period).
(6) From the stored waveform data for one wavelength, the control start time B is traced back, and the subtracted data number Nx is removed, and the phase-corrected sound pressure (phase) H at this position is converted to the original sound pressure ( Phase) R is determined. This is based on the wave phase being repeated between 0 and 2π.

  The control signal calculation unit 6c further creates a control sound by performing a process of making the phase-corrected waveform in reverse phase. The created control sound is output from the control signal calculation unit 6 c of the control controller 6. For creating the output sound pressure, the gain characteristic of the ANCS 1 obtained by measurement is used, and the output sound pressure is obtained by multiplying the estimated sound pressure by the response magnification.

  The digital signal of the control sound output from the controller 6 is converted into an analog signal by the D / A converter 7. The output signal (analog signal) of the control sound output from the D / A converter 7 is input to the speaker amplifier 8 and amplified. The amplified control sound S output from the speaker amplifier 8 is emitted from the control speaker 9.

  The active noise control method according to the present embodiment is achieved by operating the above-described ANCS1. Using the estimation of the dominant frequency of noise performed in the adaptive filter 6b without using an error microphone, the control signal calculation unit 6c performs processing such as specific phase correction based on the phase characteristics and gain characteristics inherent in the system. The phase difference and the sound pressure difference of the control sound to be created are corrected with respect to the frequency extracted by the band pass filter 6a, and then the control sound having the opposite phase is output.

  The execution procedure of the active noise control method is as follows. The noise Q emitted from the noise source 2 is measured by the measurement microphone 3, and then in the noise input from the measurement microphone 3 through the microphone amplifier 4 and the A / D converter 5 by the band pass filter 6 a. , Only the frequency component of the control target frequency band is transmitted, and then the adaptive filter 6b estimates the control target dominant frequency from the frequency component transmitted through the bandpass filter 6a. Next, the control signal calculation unit 6c Based on the measured phase lag for each frequency of the controller 6, the phase lag with respect to the dominant frequency to be controlled input from the adaptive filter 6 b is corrected by time control, and the control sound of the opposite phase is created by this. Finally, the control sound S input from the control signal calculation unit 6c through the D / A converter 7 and the speaker amplifier 8 by the control speaker 9 is output. It is adapted to release.

  The adaptive filter 6b estimates the sound pressure of the control target dominant frequency from the frequency component transmitted through the bandpass filter 6a when estimating the control target dominant frequency, and the control signal calculation unit 6c receives the control input from the adaptive filter 6b. When performing phase correction by time control for the phase delay with respect to the target dominant frequency, based on the gain characteristics for each frequency of the measurement microphone 3 and the control speaker 9 that are measured in advance, the control target dominant frequency input from the adaptive filter 6b A control sound may be created by performing gain correction on the sound pressure.

  FIG. 4 shows a state in which the ANCS 1 according to the present embodiment is installed at the site P and the mute control is performed. The arrangement of the noise source 2 and the control speaker 9 employs well-known dipole radiation, thereby reducing the radiated acoustic power. When measurement is performed with the measurement microphone 3 at the sound receiving point 13, the noise Q emitted from the noise source 2 interferes with the control sound S having the same sound pressure and opposite phase, which is emitted from the control speaker 9, Thereby, noise can be reduced.

  In the control controller 6 of the ANCS 1, the measured noise is input to the band pass filter 6a, the adaptive filter 6b estimates the control object dominant frequency in the time domain from the output of the band pass filter 6a, and the control signal calculation unit 6c further The phase and sound pressure are corrected, and a sound having a phase opposite to that of the corrected wave component is created, whereby noise can be reduced.

  In the active noise control system 1 and the method thereof according to the present embodiment described above, the phase with respect to the control target dominant frequency input from the adaptive filter 6b based on the phase delay of each frequency of the controller 6 measured in advance. Since the control signal calculation unit 6c that corrects the phase of the delay by time control and further generates a control sound of the opposite phase is provided, the control signal calculation unit 6c preferably includes the measurement microphone 3 and the measurement microphone 3 that are measured in advance. Based on the gain characteristics for each frequency of the control speaker 9, a control sound is generated by performing gain correction for the sound pressure with respect to the control target dominant frequency input from the adaptive filter. In addition to the phase delay for each frequency of the controller 6 measured in advance, a measurement microphone measured in advance And, based on the phase delay for each frequency of the control speaker 9, the phase correction for the control target dominant frequency input from the adaptive filter 6 b is performed by time control, and more preferably, the control signal calculation unit 6 c In addition to the measured gain characteristics for each frequency of the measurement microphone 3 and the control speaker 9, based on the previously measured gain characteristics for each frequency of the controller 6, the control target dominant frequency input from the adaptive filter 6 b is determined. Since the control sound with gain correction for the sound pressure is created, noise reduction control by feedforward control can be executed with high accuracy without using an error microphone.

  In addition, when an error microphone is used, it takes time to process data measured by the error microphone, and the processing speed is slow. On the other hand, in the ANCS1 and the method according to the present embodiment, the error microphone is not used. The minute processing data can be reduced, the processing speed can be improved, and the system operation responsiveness essentially required for sound processing can be remarkably improved. Furthermore, since an error microphone is not used, the number of device elements that need to be considered as control elements can be reduced, the control contents can be simplified, and the system can be prevented from becoming complicated.

  Further, as a method of phase correction for the phase lag performed by the control signal calculation unit 6c, a step of obtaining the number N of data of one wavelength of the control target dominant frequency estimated by the adaptive filter 6b, and the obtained one wavelength from the control time A step of storing the waveform data, a step of obtaining the phase delay of the controller 6 with respect to the dominant frequency to be controlled estimated by the adaptive filter 6b, a step of obtaining the number Np of data corresponding to the phase delay, A step of obtaining a data number Nx obtained by subtracting the data number Np corresponding to the phase delay from the data number N, and removing the subtracted data number Nx from the stored waveform data of one wavelength, starting from the control time. The phase correction method is used to correct the phase with a high-precision filter without using an error microphone. Therefore, it is possible to execute a forward-forward control, and thereby to construct an efficient ANCS 1 capable of appropriately emitting a control sound conforming to the noise in which the frequency of the sound to be muffled is changed every moment in the time domain. Can do.

DESCRIPTION OF SYMBOLS 1 Active noise control system 2 Noise source 3 Measurement microphone 6 Control controller 6a Band pass filter 6b Adaptive filter 6c Control signal calculation part 9 Control speaker Q Noise S Control sound

Claims (8)

A measurement microphone that measures noise emitted from a noise source, a control controller that generates and outputs control sound for reducing noise, and a control speaker that emits control sound output from the control controller,
The control controller estimates a control target dominant frequency from a band pass filter that transmits only a frequency component of a control target frequency band in noise input from the measurement microphone, and a frequency component transmitted through the band pass filter. Based on the phase delay for each frequency of the adaptive filter and the control controller measured in advance, the phase delay for the control target dominant frequency input from the adaptive filter is corrected by time control, and the opposite phase is controlled. An active noise control system comprising: a control signal calculation unit that generates sound and outputs the sound to the control speaker. The adaptive filter estimates the sound pressure of the dominant frequency to be controlled from the frequency component transmitted through the bandpass filter,
The control signal calculation unit performs gain correction on sound pressure with respect to the control target dominant frequency input from the adaptive filter, based on gain characteristics for each frequency of the measurement microphone and the control speaker measured in advance. 2. The active noise control system according to claim 1, wherein a control sound is created. The phase correction for the phase lag performed by the control signal calculation unit is:
Obtaining the number of data N of one wavelength of the controlled dominant frequency estimated by the adaptive filter;
Storing the waveform data of one wavelength obtained from the control time;
Obtaining a phase delay of the control controller with respect to the dominant frequency to be controlled estimated by the adaptive filter;
Obtaining a data number Np corresponding to the phase delay;
Obtaining a data number Nx by subtracting a data number Np corresponding to the phase delay from the data number N of the one wavelength;
3. The active noise control system according to claim 1, wherein the phase correction is performed by removing the number of subtracted data Nx from the stored waveform data of one wavelength retrospectively starting from the control time.   The control signal calculation unit, based on the phase delay for each frequency of the measurement microphone and the control speaker measured in advance in addition to the phase delay for each frequency of the control controller measured in advance, The active noise control system according to any one of claims 1 to 3, wherein phase correction is performed by time control for a phase delay with respect to the input control target dominant frequency.   The control signal calculation unit is configured to output from the adaptive filter based on a pre-measured gain characteristic for each frequency of the control controller in addition to the pre-measured gain characteristic for each frequency of the measurement microphone and the control speaker. The active noise control system according to any one of claims 1 to 4, wherein a control sound is generated by performing gain correction on a sound pressure with respect to the input control target dominant frequency.   The active noise control system according to claim 1, the noise emitted from the noise source is measured by the measurement microphone, and then the noise in the noise input from the measurement microphone is measured by the bandpass filter. , Only the frequency component of the frequency band to be controlled is transmitted, and then the dominant frequency is estimated from the frequency component that has passed through the bandpass filter by the adaptive filter, and then the control signal calculation unit Based on the phase delay of each frequency of the control controller measured in advance, the phase delay with respect to the dominant frequency to be controlled inputted from the adaptive filter is corrected by time control, and the control sound of the opposite phase is created. To the control speaker, and finally, the control speaker inputs the control signal from the control signal calculation unit. Active Noise Control method characterized by outputting a sound. The adaptive filter, when estimating the control object dominant frequency, estimates the sound pressure of the control object dominant frequency from the frequency component transmitted through the bandpass filter,
The control signal calculation unit performs gain correction for each frequency of the measurement microphone and the control speaker measured in advance when performing phase correction by time control for a phase delay with respect to the control target dominant frequency input from the adaptive filter. The active noise control method according to claim 6, wherein a control sound is generated by performing gain correction on the sound pressure with respect to the control target dominant frequency input from the adaptive filter based on characteristics. The phase correction for the phase lag performed by the control signal calculation unit is:
Obtaining the number of data N of one wavelength of the controlled dominant frequency estimated by the adaptive filter;
Storing the waveform data of one wavelength obtained from the control time;
Obtaining a phase delay of the control controller with respect to the dominant frequency to be controlled estimated by the adaptive filter;
Obtaining a data number Np corresponding to the phase delay;
Obtaining a data number Nx by subtracting a data number Np corresponding to the phase delay from the data number N of the one wavelength;
8. The active noise control method according to claim 6 or 7, wherein the phase correction is performed by removing the number of data Nx subtracted from the stored one-wavelength waveform data retrospectively starting from the control time.

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