Digital filters play a key role in the field of digital signal processing. This research presents application of particle swarm optimization (PSO) and its three new variants, dynamic and adjustable particle swarm optimization (DAPSO) and particle swarm optimization with variable acceleration factor (PSO-VAF) and attractive and repulsive particle swarm optimization (ARPSO) in linear phase digital low pass finite impulse response (FIR) filter design. Two fitness functions are considered. The fitness1 is used to find the possible minimum ripples in pass band and stop band. Fitness2 is able to...