NOISE ATTENUATION CIRCUIT FOR TRANSFORMER OF MULTI TONE AND MULTI CHANNEL TYPE

摘要

A noise reduction circuit is provided to reduce the noise but increase the processing speed by controlling the noise of a transformer with a plurality of peak frequency. A noise reduction device has an error microphone(6) printing out an error signal. An error signal amplifier circuit(10) amplifies the error signal received from the error microphone. An Anti-aliasing filter circuit(13) extracts only the low frequency component of domain with the first quadrant frequency(fmax1) from the error signal inputted to the error signal amplifier circuit An error signal regulating circuit(15) controls a DC offset of the error signal received in the anti-aliasing filter circuit. A reference signal production and level control circuit(20) controls the amplitude of the reference signal generated in the reference signal generating circuitry(21). A reference signal regulating circuit(25) controls the DC offset of the reference signal generated with the reference signal generating circuitry. A central processing unit(40) has an operation unit including a first ADC, a second ADC and a plurality of erase algorithms(41, 42, 43 and 44). The first and the second ADC convert the inputted error signal, and the reference signal into the respective digital signal.