A bandpass filter is an electronic device or circuit that allows signals between two specific frequencies to pass, but that discriminates against signals at other frequencies.In signal processing, a band-reject filter (also called a band-stop or notch filter) is a filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels.

The main difference between a bandpass and notch filter is that a bandpass filter allows signals within a particular frequency range to pass and a notch filter will filter those signals out in that one frequency range.

The band-reject filter is used mainly in public address systems and speaker systems for ensuring good quality audio.