摘要:
An active vibratory noise control apparatus has a speaker for canceling vibratory noise in the passenger compartment of a vehicle, the speaker being used as a speaker of one of different audio devices that can be installed on the vehicle. Each of the audio devices has a command key switch assembly. When the command key switch assembly is operated to turn off the transistor, a control signal is applied to a switching control circuit in an active vibratory noise control unit, which identifies the audio device installed on the vehicle. The active vibratory noise control unit generates a canceling signal matching characteristics of the speaker of the identified audio device for canceling vibratory noise in the passenger compartment.
摘要:
In an active noise cancellation system having an adaptive filter that outputs a control signal, first and second speakers that emit a canceling signal generated based on the control signal, a microphone that detects an error signal, a correction filter that corrects the base signal by a correction value to generate a reference signal and a filter coefficient updater that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter coefficient, while enabling to maintain an area in which noise can be reduced to the same level as that obtained before reducing the number of microphones.
摘要:
An active vibratory noise control apparatus reduces vibratory noise which is produced in the passenger compartment of a vehicle based on vibratory noise generated by a variable-cylinder internal combustion engine that can selectively be operated in a full-cylinder operation mode in which all of the cylinders are operated and a partial-cylinder operation mode in which some of the cylinders are out of operation. The active vibratory noise control apparatus has a partial-cylinder operation mode determining circuit for determining whether the variable-cylinder internal combustion engine is in the partial-cylinder operation mode or not. Depending on a determined result from the partial-cylinder operation mode determining circuit, a transistor is turned on or off to switch an amplifying circuit which drives a speaker into and out of operation.
摘要:
In an active noise cancellation system having an adaptive filter that outputs a control signal, first and second speakers that emit a canceling signal generated based on the control signal, a microphone that detects an error signal, a correction filter that corrects the base signal by a correction value to generate a reference signal and a filter coefficient updater that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter coefficient, while enabling to maintain an area in which noise can be reduced to the same level as that obtained before reducing the number of microphones.
摘要:
An active noise control system is provided which cancels a noise using a secondary noise from a speaker that is operated in accordance with an output from an adaptive controller. The system is configured such that microphone monitor interrupts a switch to thereby stop the secondary noise from being produced, when an error signal delivered by a microphone used for an adaptive computation in an LMS processing portion has the same sign for a predetermined duration. This allows the system to prevent the user from hearing an abnormal acoustic noise resulting from an abnormal operation or divergence of an adaptive filter even when the output signal from the microphone used for the adaptive computation is indicative of an abnormal level.
摘要:
An active noise control system is provided which cancels a noise using a sound radiated from a speaker driven by an output from an adaptive notch filter. The system employs output signals from an adder or simulation cosine-wave and sine-wave signals, an error signal or an output signal from a microphone, and a compensated signal from the adder or a signal available for acoustically transferring an output from the adaptive notch filter to the microphone in accordance with initial transfer characteristics to update the filter coefficient of the adaptive notch filter. This configuration allows the system to operate with stability even when the acoustic transfer characteristics vary with time or under circumstances where there exists a significant amount of incoming external noises. The system also prevents overcompensation for a noise at the ears of a passenger in a vehicle, thereby proving an ideal noise reduction effect.
摘要:
An active noise control system cancels vibration and noise based on an output from an adaptive notch filter. When the difference between a current engine pulse value input to the adaptive notch filter and a past engine pulse value within a predetermined time period exceeds a predetermined level, an engine pulse monitor turns off a switch to stop the output from the adaptive notch filter. As a result, when there is a sudden change in the engine rpm, the output from the adaptive notch filter is stopped before the renewal speed of the adaptive notch filter coefficient becomes too fast to follow and the coefficient diverges, to prevent generation of abnormal sound. With this active noise control system, the user will not hear any abnormal sound from the adaptive notch filter even when there is a sudden change in the engine pulse.
摘要:
The filter coefficients of an adaptive notch filter are sequentially updated to minimize an error signal based on the error signal and a first reference signal which is produced by subtracting a signal which represents the product of a sine corrective value C1 and a reference sine signal, from a signal which represents the product of a cosine corrective value C0 and a reference cosine signal. The filter coefficients of an adaptive notch filter are sequentially updated to minimize the error signal based on the error signal and a second reference signal which is produced by adding a signal which represents the product of the reference sine signal and the cosine corrective value C0 and a signal which represents the product of the reference cosine signal and the sine corrective value C1 to each other.
摘要:
An active noise controller can determine the signal transmission characteristics from the power amplifier and the speaker to the microphone without using any special external measuring instrument and calculate a cosine correction value and a sine correction value without using an external computer. The active noise controller uses the cosine correction value and the sine correction value to actively reduce vibrational noise. The measurement mode is selected on touch panel (3), and correction value calculator (22) calculates cosine correction value C0 and sine correction value C1 by using filter coefficients W0 and W1 which allow error signal e′(n) to approach zero. Memory (23) stores these values C0 and C1.
摘要:
An active noise reducing device includes switchover frequency memory which stores a speaker having weaker influence of level drop or dips in gain characteristics of transmission from first speaker and second speaker both working as secondary noise generators to microphone working as a residual signal detector, and also stores a frequency band of that speaker. Output switcher appropriately and selectively switches first speaker over to second speaker in response to the noise frequency at present calculated based on the rpm of engine by frequency calculator. This structure allows the active noise reducing device to work steadily even if level drop or a dip occurs in the gain characteristics of transmission from the speaker to the microphone, and allows suppressing the occurrence of abnormal sound due to divergence or distorted sound due to excessive output. Ideal noise reduction effect can be expected.