Provided is 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.