Filter Types

Butterworth

Used in applications where maximum pass band flatness is required.

Designed to have as flat a frequency response as possible in the passband. It is also referred to as a maximally flat (no ripples) magnitude filter.

One main disadvantage is that it achieves this pass band flatness at the expense of a wide transition band as the filter changes from the pass band to the stop band. It also has poor phase characteristics as well.

Bessel

Type of analog linear filter with a maximally flat group/phase delay (maximally linear phase response), which preserves the wave shape of filtered signals in the passband. Bessel filters are often used in audio crossover systems.

Chebyshev

Optimized to give a steeper roll off.

Have a steeper roll-off and more passband ripple (type I) or stopband ripple (type II) than Butterworth filters.

Median

A type of FIR filter which typically takes an odd number of inputs (e.g. 5 or more usually more) and sorts them by value. The filtered output is the median value (the middle value). A median filter can be very effective at removing noise spikes.

C Code Filter Design Tools

http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html