AC noise filters are used to silence an aircraft's electronic noise, such as the whine of an alternator or the noise of a rotating beacon or strobe light. The filters work by using inductance and capacitance to reduce or eliminate low-frequency noise.
AC noise filters reduce noise by allowing only DC to power sensitive onboard electronics. Many filters use either inductance or capacitance to reduce noise, but AC noise filters use both, which allows them to minimize or eliminate a wider range of frequencies. Some AC filters come with surge suppression capabilities to shield electronics from power spikes and surges.