Kenichiro Muraoka

Apparatus for reducing noise in space applicable to vehicle passenger compartment

An apparatus for reducing periodical noises transmitted from a noise source into a vehicle passenger compartment. The apparatus comprises control sound sources for producing control sounds in the vehicle passenger compartment, residual noise sensors for detecting the residual noises in the vehicle passenger compartment, transfer function filters modeled on transfer function between the control sound sources and the residual noise sensors, and adaptive digital filters having variable filter coefficients. A reference signal is produced in the form of a series of impulses having the same period as the noises. The transfer function filters are convoluted with the reference signal to produce reference processed signals. The adaptive digital filters are convoluted with the reference signal to generate drive signals to drive the control sound sources. The filter coefficients of the respective adaptive digital filters are updated based on the processed reference signals and the residual noises to reduce the noises in the vehicle passenger compartment.