An active noise control system is capable of canceling out noise in the passenger compartment of a vehicle based on low-frequency road noise. The active noise control system has a feed-forward control unit for being supplied with reference signals highly correlated to noise from a noise source and generating a noise cancellation signal which is out of phase to noise in the passenger compartment of the vehicle, and a canceling sound generating unit disposed in the passenger compartment for generating a noise canceling sound in response to the noise cancellation signal from said feed-forward control unit. The active noise control system also has microphones for generating reference signals which are positioned respectively near the base of the front seat, near the center of a roof, and within a trunk compartment, i.e., respectively at vibrational antinodes of a primary or secondary acoustic normal mode of the passenger compartment in the longitudinal direction thereof. Output signals from the microphones are supplied as the reference signals.

Active noise control system

A microphone assembly (1700) includes one or more transducers (1702) positioned in a housing (1732). Circuitry (Fig. 8) is coupled to the transducer for outputting an electrical signal such that the microphone has a main lobe directed forwardly and attenuates signals originating from the sides and/or rear. The transducers can advantageously include multiple transducers, which, with the circuit, produce a desired sensitivity pattern. The microphone assembly can be employed in a vehicle accessory.

Vehicle accessory microphone

An active noise control apparatus (100) includes a first active noise controller (11) for generating a first canceling signal (Sc1) for a first noise type, a second active noise controller (12) for generating a second canceling signal (Sc2) for a second noise type that is different from the first noise type, a mixer (20) for mixing the first canceling signal (Sc1) and the second canceling signal (Sc2) into a mixed canceling signal (Sc0), a canceling sound output unit (28) for outputting a canceling sound based on the mixed canceling signal (Sc0), and an amplitude suppressor (50) for suppressing the amplitude of the second canceling signal (Sc2) depending on the amplitude of the first canceling signal (Sc1).

Active noise control apparatus

An active noise control system generates an anti-noise signal to drive a speaker to produce sound waves to destructively interfere with an undesired sound in a quiet zone. The anti-noise signal is generated with an adaptive filter having filter coefficients. The coefficients of the adaptive filter may be adjusted based on a first filter adjustment from a first listening region, and a second filter adjustment from a second listening region. A first weighting factor may be applied to the first filter adjustment, and a second weighting factor may be applied to the second filter adjustment. The first and second weighting factors may dictate the location and size of the quiet zone as being outside or partially within at least one of the first listening region and the second listening region.

Quiet zone control system

An active noise control system generates an anti-noise signal to drive a speaker to produce sound waves to destructively interfere with an undesired sound in a targeted space. The speaker is also driven to produce sound waves representative of a desired audio signal. Sound waves are detected in the target space and a representative signal is generated. The representative signal is combined with an audio compensation signal to remove a signal component representative of the sound waves based on the desired audio signal and generate an error signal. The active noise control adjusts the anti-noise signal based on the error signal. The active noise control system converts the sample rates of an input signal representative of the undesired sound, the desired audio signal, and the error signal. The active noise control system converts the sample rate of the anti-noise signal.

System for Active Noise Control with Audio Signal Compensation

PURPOSE:To adequately control a noise based upon any signal component and to reduce the size of the device by selecting and controlling a signal component which has high autocorrelativeness or signal component having no correlation as a component which is dominant to the noise even if the noise is based upon both the components. CONSTITUTION:A noise generation state detecting means 5 detects a signal regarding the noise generation states of plural noise sources and signal component selecting means 41, 43, and 45 select the signal component with high autocorrelativeness or the signal component having no correlation as the component which is dominant to the noise from the output signal of the noise generation state detecting means 5. An adaptive digital filter 13 filters the output signal of the signal component selecting means 45 according to a specific filter coefficient and outputs a signal for driving a control sound source. At this time, an adaptive controller 16 sequentially updates the filter coefficient according to the output signals of residual noise detecting means 8a-8h and the output signal of the signal component selecting means 45 so that the output signals of the residual noise detecting means 8a-8h are reduced.

Active noise controller

PURPOSE:To suppress the increment of arithmetic load on an arithmetic unit and to attain noise reduction precisely by predicting the divergence of a control sound source based on the update quantity of the filter coefficient of an adaptive filter. CONSTITUTION:The filter coefficient is computed so as to minimize the square e of sound pressure based on a reference signal r1m to which filter processing is applied corresponding to the number of combination of transfer relation between microphones 8a-8h and speakers 7a-7d by a microprocessor 16, and the sum computation of the square e of the sound pressure, and the filter processing is applied to a reference signal from a frequency-voltage conversion circuit 11 by the filter coefficient as updating that of the adaptive filter 13 adaptively, and the speakers 7a-7d can be driven. Therefore, since it is possible to predict the divergence of the control sound source and to operate a divergence regulation means 22, divergence phenomenon can be suppressed even when the mechanical characteristics of the speakers 7a-7d and the microphones 8a-8h are changed due to the lapse of time, or the temperature change of control space occurs, etc. Also, it is possible to suppress the increment of arithmetic load on the arithmetic unit.

明生木下

Papers

Active noise controller

Active type noise controller

明生 木下

Papers

Active noise controller

Active type noise controller

明生木下