Finite Impulse Response Filter
A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs. An FIR filter can be designed to have linear phase (i.e., constant time delay, regardless of frequency). FIR filters designed for frequencies much lower that the sample rate and/or with sharp transitions are computationally intensive, with large time delays. Popularly used for adaptive filters.
See also: Infinite Impulse Response Filter.