| 摘要 |
PURPOSE:To exhibit a satisfactory noise reducing effect by forming the noise correlation detecting signal of an internal combustion engine or its multiplied signal as a sampling clock, and conducting operations such as A/D conversion, D/A conversion and filter processing by use of the sampling clock. CONSTITUTION:When an engine is started, a crank angle detection signal (x) as a noise correlation signal corresponding to double of the engine rotating speed is outputted from a sensor 8 and inputted to a processor unit 10, and a residual noise detection signal (e) detected by a microphone 7 is also inputted to the unit 10. Therefore, in the unit 10, the signals (x) and (e) are digitalized in converters 14, 15 by a clock signal SC in which the signal (x) outputted from a sampling clock generating circuit 13 is increased by four times. Then, the conversion signals X, E corresponding to the signals (x), (e) converted into a frequency area by the converting parts 27, 28 of a body 16 are subjected to filter processing by an adaptive filter part 19, and the result is converted into a time area signal by an inverse Fourier transforming part 21 and outputted to a speaker 5. |
