There is provided a filter circuit for producing a noise reduction signal for reducing a noise signal collected by a microphone, including: a digital section including an analog/digital conversion section configured to convert the noise signal into a digital noise signal, a digital filter section configured to produce a digital noise reduction signal based on the digital noise signal, and a digital/analog conversion section configured to convert the digital noise reduction signal into an analog noise reduction signal； an analog path connected in parallel to said digital section and configured to output the noise signal as it is or after processed by an analog filter； and a synthesis section configured to synthesize the analog noise reduction signal outputted from said digital/analog conversion section of said digital section and the analog signal outputted from said analog path to produce a noise reduction signal to be used for noise reduction.
