Circuit Audio Noise Filter
This audio noise
filter circuit is a bandpass filter for audio frequency band. It filters unwanted signals that are lower or higher than the audio frequencies.
Both
filters are second-order filters with a 24 dB/octave fiter capability. The 3 dB cut-off freq. are 11.8 Hz and 10.7 kHz.
The bandpass characteristic can be changed by changing the values of the capacitors and resistors. If you want to raise the bottom cut-off freq., you must reduce the values of C1 up to C4. For lowering the bottom cut-off freq. you must increase the values.