Filter (signal processing) - Definition and Overview

In electronics and signal processing, a filter is a device or process that modifies a signal.

Usually a filter has a non-uniform transfer function; i.e. its gain or attenuation depends on the signal's frequency.

• An analog filter is implemented using analog technology.
• An electronic filter is implemented by an electrical circuit.
• A digital filter is an algorithm for processing digital signals, which may be implemented in software, by a dedicated digital circuit, or a digital signal processor. Digital filters can emulate electronic filters and are now used in many modern appliances, such as CD players, radio tuners, TVs etc.
• An audio filter is a filter for processing audio signals; it is used in appliances such as CD players, in synthesizers, and for sound effects.
• An equalization filter or EQ filter corrects the response of another circuit.