Patent application number | Description | Published |
20080310650 | ACTIVE NOISE REDUCING DEVICE - An active noise reducing device includes processing circuit includes a sine wave generator for generating a sine wave having a specific frequency, a cosine wave generator for generating a cosine wave having the same frequency as that of the sine wave, and two one-tap digital filters for processing the outputs from the generators. The processing circuit also has two coefficient updating sections, which output a sum of outputs from the digital filters. Updating sections update respective coefficients of the filters based on a sum of this output from the updating sections and respective inputs to the updating sections, and the respective outputs from the generators. The noise reducing device also has an adjusting circuit for adjusting the phase and amplitude of an output from the processing circuit, the adjusting circuit thus generates a control signal of opposite phase and equal in amplitude to original noise, so that random noise such as load noise can be reduced. | 12-18-2008 |
20090058633 | ANC NOTCH FILTER ADAPTATION SYSTEM AND METHOD FOR HANDLING ROAD NOISE PEAK SHIFTS IN A MOTOR VEHICLE - A notch filter adaptation system for use with an active noise control system of a motor vehicle has a parameters determination module receiving data from a bus of a vehicle and employing the data to determine one or more parameters for a notch filter. The data can include vehicle type, tire diameter, tire cavity, and/or ambient temperature. The parameters can include one or more notch filter peak frequency values, one or more notch filter Q values, and/or modifications of predetermined peak frequency values and/or Q values. An active noise control module can employ the parameters to generate opposite phase noise in the vehicle according to one or more notch filters having frequency bands at least in part specified by the parameters. | 03-05-2009 |
20090074198 | ACTIVE VIBRATION NOISE CONTROLLER - Microphone is arranged at an evaluation point at the front seat; a signal for controlling vibration noise at this position is sent out from speaker at the front seat; secondary sound for canceling an influence of secondary sound at the front seat on the rear seat is sent out from speaker at the rear seat; microphone is arranged at an evaluation point at the rear seat; a signal for controlling vibration noise at this position is sent out from speaker; and secondary sound for canceling an influence of secondary sound at the rear seat on the front seat is sent out from speaker at the front seat. | 03-19-2009 |
20090175461 | ACTIVE NOISE CONTROLLER - In an active noise reduction apparatus with an adaptive notch filter used, a triangle wave as a reference signal input into a first coefficient updater and a second coefficient updater reduces the number of execution times of product-sum operations in a reference signal generator to reduce the operation load. | 07-09-2009 |
20090208025 | ACTIVE NOISE REDUCTION SYSTEM - An electromechanical converter has independent electric input sections. The output of an active noise reduction controller is inputted into an electric input section and the audio signal from an audio section is inputted into an electric input section. These are mechanically combined at a vibration section and the combined signal is radiated as a sound wave into the space. With such a structure, both the active noise reduction function and the audio reproduction function are realized without installing a large device in an existing audio reproduction apparatus. | 08-20-2009 |
20090279710 | Active Noise Reducing Device - 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. | 11-12-2009 |
20100111318 | ACTIVE NOISE CONTROLLER - An active noise controller using an adaptive notch filter performs a coefficient update operation by using only a signal obtained by processing an error signal with ½ cycle of the frequency of noise to be reduced for a predetermined period. This eliminates the necessity of product operation for the coefficient update operation, and in turn significantly reduces an operation load. | 05-06-2010 |
20110280410 | ACTIVE NOISE CONTROL APPARATUS - An active noise control apparatus includes a control frequency detector for determining a control frequency which is a frequency of a noise to be controlled, a sine-wave generator for generating a reference sine-wave signal having the determined control frequency, a cosine-wave generator for generating a reference cosine-wave signal having the determined control frequency, a first one-tap digital filter for outputting a first control signal obtained by multiplying the reference sine-wave signal by a first filter coefficient, a second one-tap digital filter for outputting a second control signal obtained by multiplying the reference cosine-wave signal by a second filter coefficient, an interference signal generator for generating an interference signal based on a noise control signal obtained by summing the first control signal and the second control signal, an error signal detector for detecting an error signal produced due to an interference between the interference signal and the noise, first and second coefficient updating units for updating the first and second filter coefficients according to the error signal, and a control frequency corrector for correcting the control frequency according to the first and second filter coefficients. This active noise control apparatus can reduce a noise effectively even if the control frequency shifts from the frequency of a noise actually generated. | 11-17-2011 |