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 |
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 |
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 |