Audio filter

An audio filter is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications including graphic equalizers, synthesizers, sound effects, CD players and virtual reality systems.

Being a frequency dependent amplifier, in its most basic form, an audio filter is designed to amplify, pass or attenuate (negative amplification) some frequency ranges. Common types include low-pass filters, which pass through frequencies below their cutoff frequencies, and progressively attenuates frequencies above the cutoff frequency. A high-pass filter does the opposite, passing high frequencies above the cutoff frequency, and progressively attenuating frequencies below the cutoff frequency. A bandpass filter passes frequencies between its two cutoff frequencies, while attenuating those outside the range. A band-reject filter, attenuates frequencies between its two cutoff frequencies, while passing those outside the 'reject' range.